Die experimentelle Bestimmung der Ionisationsenergien von Berkelium und Californium

"Safe" Coulomb excitation of 30Mg.

We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient $\gamma$ -spectrometer MINIBALL. Using $^{30}$Mg ions accelerated to an energy of 2.25MeV/u together with a thin $^{nat}$Ni target, Coulomb excitation of the first excited 2+ states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative de-excitation $\gamma$ -ray yields the B(E2; 0$^{+}_{gs} \rightarrow 2^{+}_{1}$) value of $^{30}$Mg was determined to be 241(31)$e^{2}$fm$^{4}$. Our result is lower than values obtained at projectile fragmenttion facilities using the intermediate-ene…

The neutron-rich Mg isotopes: first results from MINIBALL at REX-ISOLDE

After the successful commissioning of the Radioactive beam EXperiment (REX) at ISOLDE (CERN) in 2002, first physics experiments were performed in 2003 which focussed on the neutron-rich Mg isotopes in the vicinity of the “island of inversion”. After introducing the REX facility and the modern γ spectrometer MINIBALL first preliminary results will be presented showing the high potential and physics opportunities offered by this new radioactive beam facility.

Measurement of the transverse Doppler shift using a stored relativistic7Li+ ion beam

We have performed for the first time precision spectroscopy on a coasting fast7Li+ ion beam in a storage ring. The ion beam moving with 6.4% speed of light was first electron cooled and then merged with two counterpropagating laser beams acting on two different hyperfine transitions sharing a common upper level (λ-system). One laser was frequency locked to thea 3 127J2 hfs frequency component established as a secondary frequency standard at 514 nm. The second laser was tuned over theλ-resonance, which was recorded relative to127J2 hfs components. This experiment is sensitive to the time dilation in fast moving frames and will lead to new limits for the verification of special relatively. Th…

A Wind Tunnel Study of Turbulence Effects on the Scavenging of Aerosol Particles by Water Drops

Abstract Laboratory experiments are described where the effects of turbulence on the impaction scavenging of aerosol particles by water drops were investigated. During the experiments the drops were freely suspended at their terminal velocities in the Mainz vertical wind tunnel. Turbulence in the tunnel airstream was produced by placing a needle obstruction upstream of the floating drop. The energy dissipation rates e were between 0.03 and 0.5 m2 s−3. The power spectrum covered a range of k values between 102 and 3 × 103 m−1, agreeing with atmospheric observations within this range. Collector drops of 346-μm, 1.68-mm, and 2.88-mm radius were exposed to indium acetylacetonate aerosol particl…

Laser spectroscopy of radioactive lead and thallium isotopes

By collincar fast beam laser spectroscopy hyperfine structure and isotope shift have been measured of neutron deficient radioactive isotopes of lead (190Pb,191Pb,192Pb,193Pb,194Pb,195Pb,196Pb,197Pb) and thallium (188Tl190Tl,191Tl,192Tl,194Tl,196Tl). Therefrom nuclear magnetic dipole moments, electric quadrupole moments, changes of the mean square charge radii and deformation parameters are deduced and compared with predictions from theory.

Beta-decay measurements of neutron-rich thallium, lead, and bismuth by means of resonant laser ionisation

Abstract Neutron-rich thallium, lead, and bismuth isotopes were investigated at the ISOLDE facility. After mass separation and resonant laser ionisation of the produced activity, new spectroscopic data were obtained for 215,218 Bi and 215 Pb. An attempt to reach heavy thallium had to be abandoned because of a strong francium component in the beam that gave rise to a neutron background through (α,n) reactions on the aluminium walls of the experimental chamber.

Test of Time Dilation Using StoredLi+Ions as Clocks at Relativistic Speed

We present the concluding result from an Ives-Stilwell-type time dilation experiment using 7Li+ ions confined at a velocity of β=v/c=0.338 in the storage ring ESR at Darmstadt. A Λ-type three-level system within the hyperfine structure of the 7Li+3S1 →3P2 line is driven by two laser beams aligned parallel and antiparallel relative to the ion beam. The lasers' Doppler shifted frequencies required for resonance are measured with an accuracy of <4×10(-9) using optical-optical double resonance spectroscopy. This allows us to verify the special relativity relation between the time dilation factor γ and the velocity β, γ√1-β2=1 to within ±2.3×10(-9) at this velocity. The result, which is singled …

Bunching and cooling of radioactive ions with REXTRAP

The properties of radioactive ion beams produced by the present on-line target ion source technology are often not suitable for direct post acceleration. For that purpose pulsed and cooled beams of higher charged ions are required. In the case of REX-ISOLDE, the post accelerator at the CERN-ISOLDE radioactive beam facility, a unique system for beam preparation is used. It consists of a gas-filled cylindrical Penning trap (REXTRAP) for bunching and cooling followed by an electron beam ion source for charge state breeding. The Penning trap has been successfully operated with an efficiency of up to 40% and a total number of up to 107 ions stored. Buffer-gas sideband cooling at the ions’ cyclot…

Resonance ionization mass spectrometry for ultratrace analysis of plutonium with a new solid state laser system

Abstract Resonance ionization mass spectrometry (RIMS) is well-suited for isotope selective ultratrace analysis of long-lived radioactive isotopes due to its high element and isotope selectivity and good sensitivity. For the analysis of plutonium with a pulsed RIMS apparatus, a powerful, reliable and easy to handle Nd:YAG pumped titanium–sapphire laser system has been developed and combined with a time-of-flight mass spectrometer. Spectroscopic measurements led to an efficient three step excitation and ionization scheme for plutonium with λ1 = 420.76 nm, λ2 = 847.28 nm, and λ3 = 767.53 nm. The isotope shifts in this scheme for the plutonium isotopes 238 Pu through 244 Pu have been determine…

Towards laser cooling of fast Be+ ions in the storage ring TSR

Publisher Summary This chapter presents a clear understanding of laser-ion interactions under storage ring conditions to prepare the basis of laser cooling of fast-stored ion beams. In addition, the method of laser-induced fluorescence provides precise data for beam properties such as absolute velocity, momentum spread, and lifetime. 9Be+ ions stored in a heavy-ion storage ring are a promising species for laser cooling down to temperatures several orders of magnitude less than those reached for protons by electron cooling at the Novosibirsk ring. Short cooling times and microkelvin temperatures can be envisaged, where the structure of the ion beam is dominated by Coulomb repulsion. The chap…

Frequency tripling for resonance ionization spectroscopy (RIS) of Cd

To explore the nucleosynthesis of heavy elements in the rapid neutron-capture process, investigations on short- lived, very neutron-rich Cd isotopes are planned that require pure samples. These will be produced at the CERN-ISOLDE on-line mass separator in combination with a chemically se- lective laser ion source. The excitation scheme for resonance ionization of Cd was tested in Mainz with a copper-vapor- pumped dye laser system. Due to the high ionization potential of Cd, frequency tripling was required for the first excita- tion step.1D 228: 8n m/. Laser light with an average power of 2m Wwas obtained after frequency tripling and was suc- cessfully used for RIS test measurements on cadmi…

Hydrogen-like bismuth

Atomic physics at heavy ion storage rings allows to study matter in an extreme ionization state and at very high velocity. The concept of electron cooling yields an ion beam with epithermal temperatures, which is suited for many precision experiments. At the ESR even the heaviest elements can be stored up to the fully stripped charge state. The H-like ions with nuclear spin exhibit a groundstate hfs-splitting in the optical region. This can be used as a probe for QED at high Z and magnetization inside the nucleus. The topics related to cooling of ions and laser spectroscopy in a storage ring are reported and a first result of the 1s hfs in 209Bi82+ is discussed for the relevance in testing …

Efficient three-step, two-color ionization of plutonium using a resonance enhanced 2-photon transition into an autoionizing state

Resonance ionization mass spectrometry (RIMS) has proven to be a powerful method for isotope selective ultra-trace analysis of long-lived radioisotopes. For plutonium detection limits of $\rm 10^{6}$ to $\rm 10^{7}$ atoms have been achieved for various types of samples. So far a three-step, three-color laser excitation scheme was applied for efficient ionization. In this work, a two-photon transition from an excited state into a high-lying autoionizing state, will be presented, yielding a similar overall efficiency as the three-step, three-color ionization scheme. In this way, only two tunable lasers are needed, while the advantages of a three-step, three-color excitation (high selectivity,…

Large Odd-even Radius Staggering In The Very Light Platinum Isotopes From Laser Spectroscopy

Laser spectroscopy measurements have been carried out on very-neutron-deficient platinum isotopes with the COMPLIS experimental setup. Using the ${5d}^{9}{6s}^{3}{D}_{3}\ensuremath{\rightarrow}{5d}^{9}{6p}^{3}{P}_{2}$ optical transition, hyperfine spectra of ${}^{182,181,180,179,178}\mathrm{Pt}$ and ${}^{183}{\mathrm{Pt}}^{m}$ were recorded for the first time. The variation of the mean square charge radius between these nuclei, the magnetic moments of the odd isotopes, and the quadrupole moment of ${}^{183}{\mathrm{Pt}}^{m}$ were thus measured. A large deformation change between ${}^{183}{\mathrm{Pt}}^{g}$ and ${}^{183}{\mathrm{Pt}}^{m},$ an odd-even staggering of the charge radius, and a d…

Collinear two-photon excitation of indium rydberg states in a fast atomic beam

The 29p-Rydberg state of neutral indium was produced by double resonant two-photon excitation in a fast atomic beam and detected via field ionization in a longitudinal electric field.

Nuclear moments and change in the charge-radii of neutron deficient lead isotopes

The nuclear moments of195Pb and the change in the charge radii of192,194,195,196Pb have been determined from the isotope shift and hyperfine structure of the 723 nm line of neutral lead by collinear laser spectroscopy.

Collinear laser spectroscopy on108g, 108m In using an ion source with bunched beam release

The hyperfine structure and isotope shift of108gIn and108mIn have been investigated by means of collinear fast-beam laser spectroscopy in the resonance line atλ=451 nm. The indium isotopes were prepared at the GSI on-line mass separator following a fusion evaporation reaction. For the first time, a FEBIAD ion source with bunched release of indium was used. Magnetic dipole moments, electric quadrupole moments and isotope shifts were determined. The present results lead us to assign the spinI=2 to the108In (T 1/2=40 min) state. Spins and moments are discussed in the framework of thejj-coupling model.

Early onset of deformation in the neutron-deficient polonium isotopes

In-source laser spectroscopy has been performed at CERN-ISOLDE with the RILIS laser ion source on Po-191-204,Po-206,Po-208-211,Po-216,Po-218. New information on the beta decay of Po-199 were extracted in the process, challenging previous results. Large-scale atomic calculations were performed to extract the changes in the mean-square charge radius delta from the isotope shifts. The delta for the even-A isotopes reveal a large deviation from the spherical droplet model for N < 116.

Atomic spectroscopy studies of short-lived isotopes and nuclear isomer separation with the ISOLDE RILIS

The Resonance Ionization Laser Ion Source (RILIS) at the ISOLDE on-line isotope separator is based on the selective excitation of atomic transitions by tunable laser radiation. Ion beams of isotopes of 20 elements have been produced using the RILIS setup. Together with the mass separator and a particle detection system it represents a tool for high-sensitive laser spectroscopy of short-lived isotopes. By applying narrow-bandwidth lasers for the RILIS one can study isotope shifts (IS) and hyperfine structure (HFS) of atomic optical transitions. Such measurements are capable of providing data on nuclear charge radii, spins and magnetic moments of exotic nuclides far from stability. Although t…

A test of special relativity with stored lithium ions

Laser spectroscopy at the heavy ion storage ring TSR in Heidelberg allows for precision experiments testing the limits of the special theory of relativity. With an opticalΛ-type three-level system of7Li+ the Doppler shift has been measured by saturation spectroscopy as a test of the time dilatation factor γ = (1 −β2)−1/2 at an ion velocity ofυ = 6.4% c. A precision ofΔν/ν < 9 × 10−9 has been obtained, which sets a second-order limit of 1.1 × 10−6 for any deviation from the time dilatation factor. The fourth-order limit of this deviation is set below 2.7 × 10−4 by the present experiment. These limits are given at a 1 σ confidence level.

Toward a New Test of the Relativistic Time Dilation Factor by Laser Spectroscopy of Fast Ions in a Storage Ring

The frequency measurement of Doppler-shifted optical lines of ions circulating in a storage ring at high speed permits a sensitive test of the relativistic Doppler-formula and, hence, the time dilation factor γSR of special relativity. Previous measurements at the storage ring TSR with 7Li+ at v = 0.065c gave a new, improved limit, but were hampered by the large observed linewidth, exceeding the natural width 15-fold. Recently we have identified the broadening to be caused by velocity-changing processes in the storage ring. Saturation spectroscopy has proven to be largely immune against these effects and has yielded linewidths only a few MHz larger than the natural one. This is the major in…

Testing Time Dilation on Fast Ion Beams

We report the status of an experimental test of time dilation in Special Relativity. This is accomplished by simultaneously measuring the forward and backward Doppler shifts of an electronic transition of fast moving ions, using high-precision laser spectroscopy. From these two Doppler shifts both the ion velocity ? = v/c and the time dilation factor can be derived. From measurements based on saturation spectroscopy on lithium ions stored at ? = 0.03 and ? = 0.06 in the TSR heavy-ion storage ring, we achieved an upper limit for a [?2] deviation from Special Relativity of . In recent measurements on a ? = 0.34 Li+ beam in the ESR storage ring we used optical-optical double-resonance spectros…

Test of relativistic time dilation with fast optical atomic clocks at different velocities

Time dilation is one of the most fascinating aspects of special relativity as it abolishes the notion of absolute time. It was first observed experimentally by Ives and Stilwell in 1938 using the Doppler effect. Here we report on a method, based on fast optical atomic clocks with large, but different Lorentz boosts, that tests relativistic time dilation with unprecedented precision. The approach combines ion storage and cooling with optical frequency counting using a frequency comb. 7Li+ ions are prepared at 6.4% and 3.0% of the speed of light in a storage ring, and their time is read with an accuracy of 2×10−10 using laser saturation spectroscopy. The comparison of the Doppler shifts yield…

Isotope shift of182Hg and an update of nuclear moments and charge radii in the isotope range181Hg-206Hg

The technique of collinear fast-beam laser spectroscopy has been used to measure the isotope shifts of the even-even isotopes of Hg (Z=80) in the mass range 182≤A≤198 at the on-line mass separator ISOLDE at CERN. The atomic transition studied (6s 6p 3 P 2- 6s7s 3 S 1,λ=546.1 nm) starts from a metastable state, which is populated in a quasi resonant charge transfer process. The resulting changes in nuclear mean square charge radii show clearly that182Hg follows the trend of the heavier, even, weakly oblate isotopes. Correspondingly the huge odd-even shape staggering in the light Hg isotopes continues and the nuclear shape staggering and shape coexistence persists down to the last isotope inv…

First Experimental Determination of the Ionization Potentials of Berkelium and Californium

First Determination of the Ionization Potential of Actinium and First Observation of Optical Transitions in Ferminm

For the determination of the first ionization potential of actinium, 227Ac was electrodeposited on a Ta backing and covered with ~1 μm Zr. From this filament, Ac atoms were evaporated at ≥ 1250 °C. By resonant excitation with UV light of 388.67 nm and subsequent excitation with light of ca. 568 nm, Ac was ionized in an external electrical field. By determining the ionization thresholds as a function of the electrical field strength and by extrapolation to zero field strength, the first ionization potential of 43398(3) cm−1 = 5.3807(3) eV was measured.About 1 ng of 255Fm, half life 20.1 h, was prepared at ORNL by milking from 255Es produced in the High Flux Isotope Reactor and shipped to Mai…

Polarization-Dependent Disappearance of a Resonance Signal -- Indication for Optical Pumping in a Storage Ring?

We report on laser spectroscopic measurements on Li$^+$ ions in the experimental storage ring ESR at the GSI Helmholtz Centre for Heavy Ion Research. Driving the $2s\,^3\!{S}_1\;(F=\frac{3}{2}) \,\leftrightarrow\,2p\,^3\!P_2\;(F=\frac{5}{2}) \leftrightarrow 2s\,^3\!{S}_1\;(F=\frac{5}{2})$ $\Lambda$-transition in $^7$Li$^+$ with two superimposed laser beams it was found that the use of circularly polarized light leads to a disappearance of the resonance structure in the fluorescence signal. This can be explained by optical pumping into a dark state of polarized ions. We present a detailed theoretical analysis of this process that supports the interpretation of optical pumping and demonstrate…

Laser spectroscopy and laser cooling of relativistic stored ion beams

Abstract Experiments with relativistic ions at the test storage ring TSR [P. Baumann et al., Nucl. Instr. and Meth. A268 (1988) 531] demonstrate the potential of the interaction of laser light with energetic stored ions for spectroscopic purposes as well as for manipulation of the ion velocity. Latest results for Li+ ions are reported. At the ion energies available at ESR [B. Franzke, Nucl. Instr. and Meth. B24 B25 (1987) 19] it will become possible to prepare and store bare ions up to U92+. Experiments using these exotic beams are discussed and an outlook to the situation at even higher energies is given.

Nuclear spins, moments and charge radii of108?111Sn

The hyperfine structure splittings (hfs) and isotope shifts (IS) in the atomic transitions 5s2 5p21S0 → 5s2 5p6s1,3P1 have been measured for the radioactive isotopes108−111Sn and all stable ones. The tin isotopes were prepared as fast atomic beams for collinear laser spectroscopy at the GSI online mass separator following a fusion reaction. Nuclear spins, magnetic dipole, electric quadrupole moments and changes in mean square charge radii have been determined. In109Sn the spinI=5/2 was measured for the nuclear ground state (T1/2=18 min) in contradiction to the literature value. The mean square charge radii show a parabolic behaviour with a maximum at N=66. This is interpreted by collective …

“Safe” Coulomb Excitation ofMg30

We report on the first radioactive beam experiment performed at the recently commissioned REX-ISOLDE facility at CERN in conjunction with the highly efficient γ spectrometer MINIBALL. Using Mg-30 ions accelerated to an energy of 2.25 MeV/u together with a thin Ni-nat target, Coulomb excitation of the first excited 2(+) states of the projectile and target nuclei well below the Coulomb barrier was observed. From the measured relative deexcitation γ-ray yields the B(E2;0(gs)(+)R 2(1)(+)) value of Mg-30 was determined to be 241(31)e(2) fm(4). Our result is lower than values obtained at projectile fragmentation facilities using the intermediate-energy Coulomb excitation method, and confirms the …

Precision measurement of two iodine lines at 585 nm and 549 nm

The transition frequencies of thei-component of the R(99)15-1 and thew-component of the R(85)26-0 transition in the B-X system of molecular127I2 have been determined with an overall relative standard uncertainty of 1.3 · 10−10. For this purpose a commercial linear dye laser has been modified and stabilized to the corresponding iodine line. This dye laser serves as a transportable frequency standard which is compared with the wavelength standards of the PTB. The evaluation of an experiment for testing special relativity at the test storage ring (TSR) in Heidelberg is based on the precision of the reported interferometric wavelength comparison.

Partial Laser Cooling and Saturation Spectroscopy on 9 MeV 7Li+ - Ions in a Storage Ring

Publisher Summary Laser cooling and spectroscopy in traps have reached impressive perfections. This chapter discusses laser cooling and partially Doppler-suppressed spectroscopy on stored ions at 5.4% speed of light in the test storage ring (TSR) heavy ion storage ring in Heidelberg. It discusses the requirements for saturation spectroscpy with two counterpropagating collinear laser beams. In contrast to Penning and RF-traps, the ions in a storage ring move at a high longitudinal velocity with small transverse harmonic oscillations around the central orbit with just a few times the orbiting frequency in the case of strong focussing. However, the injection of the high velocity beam introduce…

Coulomb Excitation of Neutron-Rich Zn Isotopes: First Observation of the21+State inZn80

Neutron-rich, radioactive Zn isotopes were investigated at the Radioactive Ion Beam facility REX-ISOLDE (CERN) using low-energy Coulomb excitation. The energy of the 2(1)+ state in 78Zn could be firmly established and for the first time the 2+ --> 0(1)+ transition in 80Zn was observed at 1492(1) keV. B(E2,2(1)+ --> 0(1)+) values were extracted for (74,76,78,80)Zn and compared to large scale shell model calculations. With only two protons outside the Z=28 proton core, 80Zn is the lightest N=50 isotone for which spectroscopic information has been obtained to date. Two sets of advanced shell model calculations reproduce the observed B(E2) systematics. The results for N=50 isotones indicate a g…

LASER SPECTROSCOPY WITH A COOLER RING AT THE ESR (GSI) AND THE TSR (MPI HEIDELBERG)

At the TSR cooler ring at Heidelberg, laser studies were carried out using singly charged lithium and beryllium ions. Laser spectroscopy of relativistic lithium ions (v=0.04c) yielded signals with a narrow linewidth, suitable for an experimental test of special relativity. A dramatic reduction of the beam temperature, as defined by the longitudinal velocity spread, was achieved via laser cooling in both cases. At the ion energies available at ESR it will become possible to prepare and store bare ions up to U92+. Electron cooling was succesfully demonstrated for hydrogen-like Bi82+ ions, where a laser experiment is scheduled to study the ground-state hyperfine splitting.

Investigation of the Li9+H2→Li8+t reaction at REX-ISOLDE

The one-neutron transfer reaction Li-9 + H-2 -> Li-8 + t has been investigated in an inverse kinematics experiment by bombarding a deuterated polypropylene target with a 2.36 MeV/u Li-9 beam from the post-accelerator REX-ISOLDE at CERN. Excitation energies in Li-8 as well as angular distributions of the tritons were obtained and spectroscopic factors deduced. (c) 2006 Elsevier B.V. All rights reserved.

Space-Charge Effects with REXTRAP

The beam quality of radioactive ion beams produced by present target ion source technology is often not sufficient for direct post-acceleration. Furthermore, pulsed beams insure a more efficient use of an accelerator. In the case of REX-ISOLDE, the post accelerator at the CERN ISOLDE facility, a gas-filled Penning trap (REXTRAP) has been chosen for accumulation of the radioactive ions and conversion into cooled bunches. Radial centering of the ions is achieved by applying an rf field with a frequency equal to the cyclotron frequency of the desired ion species. The efficiency achieved in the first tests with different isotopes covering nearly the entire mass range was already >20%. Going to …

Trace analysis of plutonium in environmental samples by resonance ionization mass spectroscopy (RIMS)

Resonance ionization mass spectroscopy (RIMS) is well suited for trace analysis of long-lived radioisotopes in environmental, biological and technical samples. By multiple resonant laser excitation and ionization of the elemental atoms under investigation, an extremely high element selectivity can be achieved. In addition, isotope selectivity is obtained by subsequent mass analysis. The excellent sensitivity results from the large atomic cross-sections in the excitation–ionization process and the good detection efficiency for ions. The element selectivity of RIMS allows a simplified procedure for the chemical preparation of the samples compared to the requirements of thin sources for α-spec…

Laser desorption/ionization cluster studies for calibration in mass spectrometry

Precise mass calibration is mandatory in many fields of mass spectrometry. We have performed laser desorption/ionization cluster studies with a MALDI-TOF mass spectrometer on gold and fullerene targets to produce atomic clusters. These investigations demonstrate that clusters are ideally suited for this purpose. Pulsed N 2 -laser and Nd:YAG-laser ablation was used to produce positively as well as negatively charged clusters. Earlier observations of dianionic metal clusters are confirmed. First results from the tandem Penning trap mass spectrometer ISOLTRAP using carbon clusters as mass references show how carbon clusters can be applied to precision mass spectrometry by providing absolute ma…

Charge radius changes of even-even neutron-rich Tellurium isotopes

Laser spectroscopy based on resonant ionization of laser-desorbed atoms has been used to study the neutron-rich tellurium isotopes with the COMPLIS facility at ISOLDE-CERN. The isotope shift and the hyperfine structure of several neutron-rich Te isotopes: $^{120–136}$Te and $^{123m–133m}$Te have been measured. From the hyperfine structure and the isotope shift we can extract the magnetic and quadrupole moments and the change in the mean square charge radius respectively. The mean square charge radii of the even-even isotopes have been deduced and their comparison with the known data for the other elements near Z=50 is presented. The experimental $\delta$ is compared with that obtained from …

Charge-radius change and nuclear moments in the heavy tin isotopes from laser spectroscopy: Charge radius ofSn132

Laser spectroscopy measurements have been carried out on the neutron-rich tin isotopes with the COMPLIS experimental setup. Using the $5{s}^{2}5{p}^{2\phantom{\rule{0.3em}{0ex}}3}{P}_{0}\ensuremath{\rightarrow}5{s}^{2}5p6s\phantom{\rule{0.3em}{0ex}}{}^{3}{P}_{1}$ optical transition, hyperfine spectra of $^{126\ensuremath{-}132}\mathrm{Sn}$ and $^{125,127,129\ensuremath{-}131}\mathrm{Sn}{}^{m}$ were recorded for the first time. The nuclear moments and the mean square charge radius variation ($\ensuremath{\delta}\ensuremath{\langle}{r}_{c}^{2}\ensuremath{\rangle}$) were extracted. From the quadrupole moment values, these nuclei appear to be spherical. The magnetic moments measured are thus co…

Test of Special Relativity in a Heavy Ion Storage Ring

Resonance ionization mass spectroscopy for trace determination of plutonium in environmental samples

Resonance ionization mass spectroscopy (RIMS) is a sensitive and isotope selective method and well suited for trace analysis of plutonium in the environment. After the chemical isolation of plutonium from soil, air filters or urine, e.g., it is electrolytically deposited as hydroxide on a tantalum backing and covered with a thin titanium layer. By heating such a sandwich filament in the RIMS-apparatus under vacuum an atomic beam of plutonium is produced. The atoms are ionized by a three-step resonant excitation using pulsed dye lasers, and the ions are mass-selectively detected with a time-of-flight (TOF) spectrometer and a multi channel plate detector. RIMS yields a low detection limit of …

Improved test of time dilation in special relativity.

An improved test of time dilation in special relativity has been performed using laser spectroscopy on fast ions at the heavy-ion storage-ring TSR in Heidelberg. The Doppler-shifted frequencies of a two-level transition in 7 Li + ions at v = 0.064c have been measured in the forward and backward direction to an accuracy of Δν/ν = 1 × 10 - 9 using collinear saturation spectroscopy. The result confirms the relativistic Doppler formula and sets a new limit of 2.2 × 10 - 7 for deviations from the time dilation factor γ S R = (1 - ν 2 /c 2 ) - 1 / 2 .

Nuclear Radiation Detected Optical Pumping of neutron-deficient Hg isotopes

The extension of the Nuclear Radiation Detected Optical Pumping method to mass-separated samples of isotopes far off stability is presented for a series of light Hg isotopes produced at the ISOLDE facility at CERN. The isotope under investigation is transferred by an automatic transfer system into the optical pumping apparatus. Zeeman scanning of an isotopically pure Hg spectral lamp is used to reach energetic coincidence with the hyperfine structure components of the 6s 2 1 S 06s6p 3P1,λ=2,537 A resonance line of the investigated isotope and the Hg lamp. The orientation built up by optical pumping is monitored via the asymmetry or anisotropy of the nuclear radiation. Nuclear spins, magneti…

β−decay of the neutron-rich isotope215Pb

This Brief Report reports on the first observation of the β--delayed γ decay of 215Pb, feeding states in 215Bi. The 215Pb beam was produced using resonant laser ionization and mass separated at the ISOLDE-CERN on-line mass separator. This ensured clean identification of the γ rays as belonging to the decay of 215Pb or its β-decay daughters. A half-life of 147(12) s was measured for the 215Pb β decay and a level scheme for the daughter nucleus 215Bi is proposed, resulting in an extended systematics of the excited states of the neutron-rich Bi isotopes.

Isotope selective ultratrace analysis of plutonium by resonance ionisation mass spectrometry

Abstract Resonance ionisation mass spectrometry (RIMS) is a sensitive and selective method for isotopically resolved ultratrace analysis of long-lived radionuclides. For the routine analysis of plutonium three titanium–sapphire lasers pumped by a pulsed Nd:YAG laser in combination with a time-of-flight mass spectrometer are used. The detection limit of this system is as low as 106–107 atoms for the plutonium isotopes 238Pu to 244Pu. The RIMS technique was applied to investigate the isotopic composition and the content of plutonium in a depleted uranium penetrator as used during the Balkan conflict delivering important information on the origin of the depleted uranium in this type of ammunit…

Nuclear moments and the change in the mean square charge radius of neutron deficient thallium isotopes

The hyperfine structure, isotope and isomeric shifts in the atomic transition 6p 2 P 3/2−7s 2 S 1/2, λ=535 nm have been measured for theI=7 andI=2 states of190, 192, 194, 196Tl; theI=1/2 andI=9/2 states of191Tl and the I=7 isomer of188Tl. The thallium isotopes were prepared as fast atomic beams at the GSI on-line mass separator following fusion reactions and — in some cases — subsequentβ-decay. The nuclear dipole moments, electric quadrupole moments and the change in the nuclear mean square charge radius are evaluated. Theuu-isotopes show an isomeric shift which changes sign between192Tl and194Tl.

Status of REX-ISOLDE

REX-ISOLDE [1] is a post-accelerator situated at the ISOLDE radioactive ion beam facility placed at CERN, Geneva. It’s main aim is to increase the energy of light (A < 50) radioactive ions from 60 keV to 0.8–2.2MeV/u. REX—ISOLDE uses a new concept of post-acceleration of radioactive ion beams by using charge breeding of the ions in a high charge state ion source and the efficient acceleration of the highly charged ions in a short LINAC using modern ion accelerator structures. In a first step the radioactive ions are captured in a large gas-filled Penning trap. The task is to accumulate, cool and bunch the beam and prepare it for the injection into an electron beam ion source (EBIS). Cooling…

Cluster calibration in mass spectrometry: laser desorption/ionization studies of atomic clusters and an application in precision mass spectrometry.

For accurate mass measurements and identification of atomic and molecular species precise mass calibration is mandatory. Recent studies with laser desorption/ionization and time-of-flight analysis of cluster ion production by use of fullerene and gold targets demonstrate the generation of atomic clusters for calibration purposes. Atomic ion results from the Penning trap mass spectrometer ISOLTRAP, in which a carbon cluster ion source has recently been installed, are presented as an application in the field of precision mass spectrometry.

Bimodal velocity distribution of atoms released from nanosecond ultraviolet laser ablation

We have investigated the velocity distributions of atoms released from a metallic gadolinium surface by UV laser ablation. The fluences of the nanosecond laser pulses were chosen for a pure release of neutrals and at a higher fluence level for the release of both neutrals and ions. In both cases a thermal Maxwell-Boltzmann slope has been observed for the low velocities, whereas for high velocities strong deviations from a thermal distribution have been seen. The observed velocity distribution has been explained by a bimodal structure including a thermal phase and a shockwave driven ``blow-off'' phase.

New access to the magnetic moment distribution in the nucleus by laser spectroscopy of highly charged ions

Abstract The availability of high intensity, high quality beams of highly charged ions has started a new application for laser spectroscopy. High resolution spectroscopy can now be applied to a study of hydrogen-like atomic states in heavy elements. In principal, this will allow a determination of the hyperfine splitting with an accuracy in the 10 −6 -range or better. Presently this exceeds the limits given by the uncertainties of the nuclear quantities, especially the distribution of the nuclear magnetization in the nucleus. Since the new approach can be applied to a family of test cases, it can provide a wide experimental basis for the separation of nuclear and QED effects. This is especi…

Measurement of isotope shift and hyperfine splitting of190, 191, 193, 197Pb isotopes by collinear laser spectroscopy

We report here on the measurement of isotope shift and hyperfine splitting of190, 191, 193, 197Pb for the 723 nm atomic optical transition. Detailed analysis of the optical data has been done by combining them with the available muonic and electronicx-ray isotope shift data. The magnetic dipole moments and the electric quadrupole moments of the odd isotopes have been extracted from the hyperfine coupling constants of the atomic states involved in the optical transition used.

Nuclear moments and charge radii of107?111in determined by laser spectroscopy

Collinear fast beam laser spectroscopy has been used to measure the hyperfine structure and isotope shift in the atomic 5s 2 5p 2 P 3/2-5s 2 6s 2 S 1/2 transition (λ=451 nm) of107–111In. Secondary beams of neutron deficient indium isotopes were prepared at the GSI on-line mass separator following fusion evaporation reactions. Magnetic dipole moments and electric quadrupole moments have been determined. The isotope shifts are discussed in terms of the change of the mean square nuclear charge radii and compared with the droplet model predictions and the deformation values calculated from the quadrupole moments.

Ion beam preparation of 7Li+ for precision experiments at heavy ion storage rings

Abstract Heavy ion storage rings allow for tests of the structure of local space time via the Doppler effect. At the TSR/Heidelberg an experiment with high resolution laser spectroscopy at 7 Li + is performed. To gain the maximum resolution for saturation spectroscopy new methods of relativistic ion beam preparation and diagnostics have been developed. The laser cooling of the beam allows for precision determination of the mean velocity of the ions. A novel phase synchronous detection scheme, ultimately sensitive to single ions, gives insights into the cooling mechanism and dynamics. With an additional synchronous excitation scheme systematic uncertainties of the test experiment can be dras…

Determination of the first ionization potential of actinide elements by resonance ionization mass spectroscopy

Abstract Resonance ionization mass spectroscopy (RIMS) in the presence of an external static electric field has been used for the determination of photoionization thresholds. Extrapolation of the thresholds obtained with different electric field strengths to zero field strength directly leads to the first ionization potential (IP). The ionization potentials of the transplutonium elements americium, curium, berkelium and californium could be measured for the first time. Due to the high sensitivity of RIMS, samples of only 1012 atoms have been used. The results are: IPAm = 5.9738(2)eV, IPCm = 5.9915(2)eV, IPBk = 6.1979(2)eV and IPCf = 6.2817(2)eV. The same technique was applied to thorium, ne…

Nuclear Moments and Deformation Change inA184ug,mfrom Laser Spectroscopy

Resonance ionization spectroscopy (RIS) was performed on desorbed Au, and the complete hyperfine spectrum of both isomeric and ground states of the short lived 184Au nucleus has been recorded from the 5d106s S1y2 ! 5d106p P3y2 optical transition. The nuclear moments of both states and the mean square charge radius changes were measured. The magnetic moments were determined to be m 184g I­5 ­ 12.07s2dmN and m I­2 ­ 11.44s2dmN and the spectroscopic quadrupole moments to be Q 184g s ­ 14.65s26db and Q184m s ­ 11.90s16d b. A difference in the mean square charge radius dkr2 c l184g,184m ­ 20.036s3d fm2 was found. [S0031-9007(97)03992-6]

Orientation of199mHg by optical pumping detected by ?-radiation anisotropy

199mHg was produced and mass separated at the ISOLDE facility (CERN). Nuclear orientation achieved by optical pumping via the resonance line 6s21S0→6s6p3P1,λ=2537A was monitored by means of the anisotropy of theγ-radiation emitted in the cascade199mHg(I=13/2+) $${}^{199m}Hg(I = 13/2^ + )\xrightarrow[{M4}]{}{}^{199*}Hg(I = 5/2^ - )\xrightarrow[{E2}]{}{}^{199}Hg(I = 1/2^ - ).$$ 199*Hg(I=5/2−)199Hg(I=1/2−).

Precision Laser Spectroscopy of the Ground State Hyperfine Splitting of HydrogenlikeBi82+209

The first direct observation of a hyperfine splitting in the optical regime is reported. The wavelength of the $M1$ transition between the $F=4$ and $F=5$ hyperfine levels of the ground state of hydrogenlike $^{209}\mathrm{Bi}^{82+}$ was measured to be ${\ensuremath{\lambda}}_{0}=243.87(4)$ nm by detection of laser induced fluorescence at the heavy-ion storage ring ESR at GSI. In addition, the lifetime of the laser excited $F=5$ sublevel was determined to be ${\ensuremath{\tau}}_{0}=0.351(16)$ ms. The method can be applied to a number of other nuclei and should allow a novel test of QED corrections in the previously unexplored combination of strong magnetic and electric fields in highly cha…

Determination of spin, magnetic moment and isotopic shift of neutron rich205Hg by optical pumping

Neutron rich205Hg (T 1/2=5.2 min) was produced and on-line mass separated at the ISOLDE facility at CERN. The polarization achieved by optical pumping via the atomic line (6s 21 S 0↔6s6p 3 P 1,λ=2 537A) was monitored by theβ decay asymmetry. Hyperfine structure and isotopic shift of the205Hg absorption line was determined by Zeeman scanning. In addition a magnetic resonance was performed on the polarized205Hg nuclei in the atomic ground state. The results are: $$I(^{205} Hg) = \tfrac{1}{2}$$ (confirmed);μ I (205Hg)=0.5915 (1)μ N (uncorrected for diamagnetism); isotopic shiftδv204/205=v(205Hg)-v(204Hg)=−1.8 (1) GHz.μ I and IS are discussed briefly in the frame of current literature.

Accelerated radioactive beams from REX-ISOLDE

In 2001 the linear accelerator of the Radioactive beam EXperiment (REX-ISOLDE) delivered for the first time accelerated radioactive ion beams, at a beam energy of 2 MeV/u. REX-ISOLDE uses the method of charge-state breeding, in order to enhance the charge state of the ions before injection into the LINAC. Radioactive singly-charged ions from the on-line mass separator ISOLDE are first accumulated in a Penning trap, then charge bred to an A/q < 4.5 in an electron beam ion source (EBIS) and finally accelerated in a LINAC from 5 keV/u to energies between 0.8 and 2.2 MeV/u. Dedicated measurements with REXTRAP, the transfer line and the EBIS have been carried out in conjunction with the first co…

Hyperfine measurements in a storage ring

Starting with a look at the outstanding role of the hydrogen atom in modern physics, this work reviews aspects of an extension of precision spectroscopy to the ground-state hyperfine structure of highly charged hydrogenic ions. In this connection, the preferences of heavy-ion storage rings are outlined and illuminated by the laser-spectroscopic measurement (the first of that kind) of the 1s hyperfine splitting of 209Bi82+, stored in the heavy-ion storage ring at GSI. The experimental results, including the mean lifetime of the upper 1s substate, are compared with the presently available theoretical calculations. The relevance of studying further hydrogenicc ions in the vicinity of the doubl…

Spins, moments and charge radii in the isotopic series181Hg-191Hg

The hyperfine structure splitting and the isotope shift in the (6 s2 1S0 - 6s 6p3P1,λ=2,537 A) line of very neutron deficient Hg isotopes were determined by the β radiation detected optical pumping method (β-RADOP). In addition, nuclear magnetic resonance was observed in the atomic ground state. The results are Mean-square nuclear charge radii are calculated. Interpreting the sudden change of nuclear radius between187Hg and185Hg δ〈r2〉187,185=0.42(5)fm2 as oblate-prolate shape transition, one obtains δ〈β2〉 =0.054(5).

Production of ionic and atomic beams of alkaline elements

Abstract An on-line mass spectrometer has been developed and used to perform atomic and nuclear spectroscopy on long series of alkali isotopes including nuclei far from stability. The apparatus was on-line either to the ISOLDE mass separator or directly to the PS, proton beam. In the case of atomic spectroscopy, a thermal atomic beam is needed. As ISOLDE delivers 60 keV ions, a high efficiency “ion-to-atom coverter” has been developed. In all cases, an “ionizer” is required to produce 10 keV ions for the ion source of the mass spectrometer. These two special devices are described, their efficiency and the consequent delay times discussed. The different targets which have been developed for …

Laser spectroscopy of neutron deficient lead and thallium isotopes: Systematics of nuclear radii in the Z = 82 region

Publisher Summary The high sensitivity achievable in laser spectroscopic methods allows the extraction of nuclear quantities even of artificially produced short-lived nuclides far off from nuclear stability. By analyzing the hyperfine structure and the isotope shift magnetic dipole moments, the electric quadrupole moments and the change of the nuclear charge radius can be studied. This chapter describes an experiment that was carried out at the GSI on-line mass separator using collinear fast atomic-beam laser spectroscopy. Radioactive lead and thallium isotopes were produced by bombarding natural tungsten targets with oxygen beams. For the lighter thallium isotopes, a tantalum target was us…

Test of special relativity in an ion storage ring

An accurate measurement of the Doppler effect in collinear laser spectroscopy has been performed at the TSR storage ring with electron cooled7Li+ ions atΒ=0.064. This experiment is a sensitive test of theγ=(1−Β2)−1/2 factor(Β=v/c) in the special theory of relativity. The Doppler shifted frequencies of the moving7Li+ ions are compared with calibrated molecular lines at rest. The frequencies at rest for the7Li+ ions are known from independent measurements. The Doppler shifted frequencies in the collinear experiment have been measured with a precision ofδv/v=6×10−9, mainly limited by the signal width of the resonance. A corresponding upper limit of 8×10−7 is deduced for any deviation of the ti…

High resolution spectroscopy of rydberg states in indium I

Two-photon laser spectroscopy in a dense indium vapour allowed to investigatenp2P1/2, 3/2 states (n=27–35) for113, 115In with a thermionic diode. Precise data on the fine structure splitting of these states and the isotope shift of the two photon transitions have been obtained. The fine structure splitting shows a hydrogenic behaviour. By using the result of our isotope shift measurement in combination with literature values, level isotope shifts with reference to the ionization limit are deduced and analysed with respect to the different contributions.

Accelerating Radioactive Ion Beams With REX-ISOLDE

The post accelerator REX‐ISOLDE is installed at the ISOLDE facility at CERN, where a broad variety of radioactive ions can be addressed. Since the end of 2001 beams at the final energy of 2.2 MeV/u are available. REX‐ISOLDE uses a unique system of beam bunching and charge breeding. First a Penning trap accumulates and bunches the ions, which are delivered as a quasi‐continuous beam from the ISOLDE target‐ion‐source, and then an electron beam ion source (EBIS) charge‐breeds them to a mass‐to‐charge ratio below 4.5. This enables a very compact design for the following LINAC, consisting of a 4 rod RFQ, an IH structure and three 7‐gap‐resonators. The later ones allow a variation of the final en…

Optical spectroscopy using mass-separated beams: Nuclear properties of unstable indium and tin isotopes

Abstract Collinear fast-beam laser-spectroscopy has been used to measure the hyperfine structure and isotope shift of several indium and tin isotopes. The related experimental techniques are described, including the preparation of mass-separated beams of neutron-deficient indium and tin isotopes at the GSI on-line mass separator following fusion-evaporation reactions. The deviation of the observed dependence of the charge radii upon the neutron number from the expected behaviour is briefly discussed.

First observation of the β-decay of neutron-rich 215Pb and 218Bi by the pulsed-release technique and resonant laser ionisation

The neutron-rich Tl, Pb and Bi isotopes are of exceptional interest to trace the evolution of single-particle levels away from the doubly magic 208Pb towards the neutron-rich side of the nuclear chart. While 208Pb is well understood in terms of the shell model, experimental data on the heavier isotopes is very scarce and it is far from clear to what extent the shell model is upheld [1]. Furthermore, large branchings ratios for β-delayed neutron emission are expected in this mass region, adding astrophysical interest to the subject [2].

Laser cooling of stored high-velocity ions by means of the spontaneous force

A longitudinal laser cooling of ion beams at about 5% of the velocity of light has been performed at the Heidelberg Test Storage Ring with various cooling schemes employing the spontaneous force. For a 7.29-MeV $^{9}\mathrm{Be}^{+}$ beam with an initial longitudinal temperature of 2700 K, the main characteristics of laser cooling in a storage ring are discussed. When undamped, the transverse betatron oscillations of the coasting ions limit the longitudinal temperature after laser cooling to typically 1 K. After damping the transverse motion by precooling the ions with an electron cooler, longitudinal temperatures of below 30 mK have been obtained in the subsequent laser cooling. In this cas…

First laser cooling of relativistic ions in a storage ring

The first successful laser cooling of ions at relativistic energies was observed at the Heidelberg TSR storage ring. A $^{7}\mathrm{Li}^{+}$-ion beam of 13.3 MeV was oberlapped with resonant copropagating and counterpropagating laser beams. The metastable ions were cooled from 260 K to a longitudinal temperature of below 3 K and decelerated by several keV. The longitudinal velocity distribution was determined by a fluorescence method. After laser cooling a strongly enhanced narrow peak appeared in the Schottky noise spectrum in addition to the uncooled ion distribution.

Determination of the first ionization potential of einsteinium by resonance ionization mass spectroscopy (RIMS)

Abstract The first ionization potential of einsteinium (IP Es ) was determined by resonance ionization mass spectroscopy (RIMS) using samples with ≤10 12 atoms of 254 Es ( T 1/2 =276 days). This method is based on the measurement of photoionization thresholds as a function of applied electric field strength, followed by extrapolation to zero field strength to yield IP Es . An atomic beam of Es was created by heating a filament on which einsteinium was electrodeposited from an aqueous solution onto a tantalum backing and covered with titanium metal. Es atoms were ionized via a three-step excitation scheme, and the ions mass-selectively detected in a time-of-flight (TOF) mass spectrometer. Th…

A new measurement of the 7Be(p,γ)8B cross-section with an implanted 7Be target

Abstract The 7Be(p,γ)8B capture reaction is of major importance to the physics of the sun and the issues of the “solar neutrino puzzle”. We report here on a new determination of the absolute cross section of this reaction, using a novel method which overcomes some of the major experimental uncertainties of previous measurements. We utilize a 7Be target implanted into a Cu substrate and a uniformly scanned particle beam larger than the target spot, eliminating issues of target homogeneity and backscattering loss of 8B reaction products. The target was produced using a beam of 1.8·1010/s 7Be nuclei extracted at ISOLDE (CERN) from a graphite target bombarded by 1 GeV protons in a two-step reso…

Structure of191Pb from α- and β-decay spectroscopy

International audience; Complementary studies of 191 Pb have been made in the β decay of 191 Bi at LISOL (CRC) and in the α decay of 195 Po at ISOLDE (CERN). Fine structures in the α decay of the low-spin and high-spin isomers of 195 Po have been fully resolved. Identification of the parent state is made possible via isomer selection based on narrowband laser frequency scanning. The α-particle and γ-ray energies have been determined with greater precision. New α-particle and γ-ray energies are identified. Branching ratios in the decay of 195 Po and 191 Pb have been examined. Structure of 191 Pb from α- and β-decay spectroscopy 2 PACS numbers: 23.20.Nx Internal conversion, 23.60.+e α decay, …

Charge radius change in the heavy tin isotopes until A = 132 from laser spectroscopy

Laser spectroscopy measurements have been carried out on the very neutron-rich tin isotopes with the COMPLIS experimental setup. Using the 5s 25p 23P 0 → 5s 25p6s 3P 1 optical transition, hyperfine spectra of 126-132Sn and 125m, 127m, 129m-131mSn where recorded for the first time. The variation of the mean-square charge radius ( δ〈r 2〉) between these nuclei and nuclear moments of the isomers and the odd isotopes were thus measured. An odd-even staggering which inverts at A = 130 is clearly observed. This indicates a small appearance of a plateau on the δ〈r 2〉 which has to be confirmed by measuring the isotope shift beyond A = 132.

Lasers in nuclear physics

Laser preparation of bunched ion beams

Abstract Laser ionization at ISOLDE is performed with high repetition laser beams in the ion source unit and for daughter elements with low repetition lasers synchronized with laser desorption from a secondary target. We are preparing an implementation of thermal adsorption followed by laser desorption and laser ionization in the target ion source unit of ISOLDE. The combination of resonance ionization with thermal bunching allows the preparation of bunched and chemically pure ion beams. Bunched ion beams of Mg or Ca are prepared for post-acceleration at REX-ISOLDE. In order to investigate the process of adsorption and pulsed laser desorption, experiments are performed with Ba vapour. In a …

Intense beams of mass-separated, neutron-deficient indium, tin, thallium and lead isotopes

A discharge ion source of the FEBIAD-type that delivers intense beams of neutron-deficient isotopes of indium, tin, thallium and lead produced in heavy-ion-induced fusion reactions is described. After mass separation the isotopically pure beams with intensities of up to 3 × 107 ions/s were available for gamma and laser spectroscopy. This corresponds to an overall separation efficiency of about 30%.

Cooling of radioactive ions with the Penning trap REXTRAP

Abstract Cooling of radioactive ion beams in a Penning trap is an essential component of the post-accelerator REX-ISOLDE at CERN. Prior to their charge-breeding and acceleration, ions from the on-line mass separator ISOLDE are accumulated, cooled and bunched with REXTRAP. This beam preparation provides short ion pulses with low emittance, key ingredient for a high efficiency of REX-ISOLDE. Two different cooling techniques have been investigated with REXTRAP. Both rely on the use of a buffer gas as the coolant but differ in the way the transversal compression of the stored ion cloud is achieved. Sideband cooling with a light buffer gas as coolant is the standard technique used at REXTRAP so …

Nuclear moments and charge radii of105, 106In

With high resolution collinear fast beam laser spectroscopy in the 451 nm-line of Indium nuclear moments and the change in the mean square radii of the nuclear charge distribution of105,106 In have been determined.

Iodine hyperfine structure and absolute frequency measurements at 565, 576, and 585nm

Abstract The hyperfine structure splittings of the P(10)14-1, R(15)14-1, and R(99)15-1 transitions at 585 nm, P(62)17-1 at 576 nm, and P(80)21-1 at 565 nm in 127 I 2 are measured by heterodyne spectroscopy using two dye lasers. In addition, the absolute frequencies of the hyperfine components P(10)14-1 a 15 and P(80)21-1 a 10 are determined using a self-referenced frequency comb. These frequencies are used in an experiment testing relativistic time dilation by laser spectroscopy on a fast ion beam.

Charge radii of odd-A 191–211Po isotopes

Isotope shifts have been measured for the odd-A polonium isotopes 191–211Po and changes in the nuclear mean square charge radii δr2 have been deduced. The measurements were performed at CERN-ISOLDE using the in-source resonance-ionization spectroscopy technique. The combined analysis of these data and our recent results for even-A polonium isotopes indicates an onset of deformation already at 197,198Po, when going away from stability. This is significantly earlier than was suggested by previous theoretical and experimental studies of the polonium isotopes. Moreover and in contrast to the mercury isotopes, where a strong odd–even staggering of the charge radii of the ground states was observ…

Modern Ives-Stilwell Experiments At Storage Rings: Large Boosts Meet High Precision

We give a brief overview of time dilation tests using high-resolution laser spectroscopy at heavy-ion storage rings. We reflect on the various methods used to eliminate the first-order Doppler effect and on the pitfalls encountered, and comment on possible extensions at future facilities providing relativistic heavy ion beams at $\gamma \gg 1$.

Laser spectroscopy of radioactive isotopes

The experimental conditions for laser spectroscopy of shortlived isotopes is discussed with respect to nuclear lifetime, reaction rates and samples preparation by on-line mass-separator techniques. The method of collinear laser spectroscopy is presented with results for medium mass elements near the closed proton shell Z=50. An interpretation of magnetic moments, spectroscopic quadrupole moments and the parabolic shape of the isotope shift in this region of nuclei is given.

Recent developments in and applications of resonance ionization mass spectrometry

Resonance Ionization Mass Spectrometry (RIMS) has nowadays reached the status of a routine method for sensitive and selective ultratrace determination of long-lived radioactive isotopes in environmental, biomedical and technical samples. It provides high isobaric suppression, high to ultra-high isotopic selectivity and good overall efficiency. Experimental detection limits are as low as 106 atoms per sample and permit the fast and sensitive determination of ultratrace amounts of radiotoxic contaminations. Experimental arrangements for the detection of different radiotoxic isotopes, e.g. 236–244Pu, 89,90Sr and 99Tc in environmental samples are described, and the application of RIMS to the ul…

First experiments with the heidelberg test storage ring TSR

Abstract The Heidelberg heavy ion test storage ring TSR started operation in May 1988. The lifetimes of the ion beams observed in the first experiments can be explained by interactions with the residual gas. Multiple Coulomb scattering, single Coulomb scattering, electron capture and electron stripping are the relevant processes. Electron cooling of ions as heavy as O 8+ has been observed for the first time. With increasing particle number, the longitudinal Schottky noise spectrum becomes dominated by collective waves for cooled beams, allowing a determination of velocities of sound. After correcting for these coherent distortions fo the Schottky spectrum, the longitudinal beam temperature …

Determination of the first ionization potential of nine actinide elements by resonance ionization mass spectroscopy (RIMS)

The high sensitivity of RIMS enables the precise determination of the first ionization potential of actinide elements with a sample size of ≤1012 atoms. By multiple resonant laser excitation, the actinide atoms under investigation are ionized in the presence of an electric field, and the ions are mass-selectively detected in a time-of-flight spectrometer. The first ionization potential is obtained by scanning the wavelength of the laser used for the last excitation step across the ionization threshold Wth—indicated by a sudden increase of the ion count rate—at various electric field strengths. Extrapolation of Wth to electric field strength zero leads directly to the first ionization potent…

Periodic unmixing of a binary metallic vapor

We report on a type of surface structuring after short pulse laser ablation of a binary alloy. We observe the emergence of a concentric ring structure with changing elemental composition. The composition changes are interpreted by condensation of the ambient ablation vapor due to stress wave excitations in the ablation spot.

Statistical mechanics of fullerene coalescence growth

Among the different carbon allotropes fullerenes are exceptionally intriguing for their spheroidal topology out of pentagons and hexagons. However, the dominant formation mode is still ambiguous. Here, we analyze the fullerene formation process by the statistical analysis of fullerene sizes produced in a laser-induced microplasma finding that a simple two-parameter lognormal distribution describes impressively well the cluster frequencies under various conditions. Our findings clearly reveal coalescent growth following a classical collision dynamics and disagree with several earlier assumptions.

Multi-color resonance ionization of laser ablated gadolinium at high laser power

Abstract Spectroscopic and analytical properties of a trace analytical method using multi-step resonance ionization at high laser intensities (>kW/cm 2 ) have been investigated with gadolinium as a test element. Strongly saturated transitions are observed, which have been used for a temperature determination of the atoms in the laser ablated plume. Regimes of multi-step resonance ionization and multiphoton ionization could be distinguished. Analytical performances due to resonance enhancement and resulting discrimination against non-resonant background, precision in isotope ratio determination and overall detection efficiency are discussed.

Low energy reactions with radioactive ions at REX-ISOLDE-the 9Li + 2H case

19 pages, 12 figures, 2 tables.-- PACS nrs.: 25.60.-t; 25.45.-z; 27.20.+n.-- et al. ISOLDE Collaborattion and REX-ISOLDE Collaboration.

A laser desorption/resonance enhanced photoionisation TOF-system for the spatially resolved trace analysis of elements

Abstract A novel method for direct and spatially resolved elemental trace analysis with high sensitivity and elemental selectivity is presented. The concept is based on the combination of a commercial MALDI-TOF mass spectrometer with a pulsed laser system for resonant postionisation of neutrals. While the MALDI method is usually applied for investigations of large organic compounds and biomolecules, the technique discussed here concerns the low mass range around 1 ⩽ A ⩽ 300. The analytical performances of the setup with respect to mass analysis, spatial resolution and overall detection efficiency are discussed.