0000000000115437
AUTHOR
G. Bollen
"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…
Mass measurements on neutron-deficient Sr and neutron-rich Sn isotopes with the ISOLTRAP mass spectrometer
Abstract The atomic masses of 76,77,80,81,86,88 Sr and 124,129,130,131,132 Sn were measured by means of the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. 76 Sr is now the heaviest N = Z nucleus for which the mass is measured to a precision better than 35 keV. For the tin isotopes in the close vicinity of the doubly magic nucleus 132 Sn, mass uncertainties below 20 keV were achieved. An atomic mass evaluation was carried out taking other experimental mass values into account by performing a least-squares adjustment. Some discrepancies between older experimental values and the ones reported here emerged and were resolved. The results of the new adjustment and their impact will be pr…
Quadrupole excitation of stored ion motion at the true cyclotron frequency
Abstract The motion of an ion in a Penning trap has been investigated in the presence of an azimuthal quadrupole radio frequency field and a damping force provided by buffer gas collisions. Analytical expressions are derived which describe the line shape of the cyclotron resonance as well as the properties of the mass-selective cooling mechanism for heavy ions. Excellent agreement is observed between theoretical results and experimental data obtained with the tandem Penning trap mass spectromer ISOLTRAP at ISOLDE (CERN).
Nuclear shape transition in neutron-deficient gold isotopes
4 pages, 1 table, 4 figures.
Ramsey technique applied in a Penning trap mass spectrometer
Abstract The Ramsey method has been applied in an experiment aiming for accurate mass determination of unstable isotopes. The ion motion in a Penning trap has been excited with time-separated oscillatory fields and Ramsey fringes were observed in the case of dipole and quadrupole excitation. The experimental resonances are in good agreement with theory. Further applications of the technique are discussed.
The SMILETRAP (Stockholm-Mainz-Ion-LEvitation-TRAP) facility
Described in this paper is an experimental facility which measures atomic masses by using multiply charged ions from an electron beam ion source. The ions are injected into a Penning trap and the cyclotron frequencies measured. A precision of 2×10−9 has been reached using highly charged carbon, nitrogen, oxygen and neon.
Direct mass measurements on neutron-deficient xenon isotopes with the ISOLTRAP mass spectrometer
The masses of Xe isotopes with 124 A 114 have been measured using the ISOLTRAP spectrometer at the on-line mass separator ISOLDE/CERN. A mass resolving power of 500000 was chosen resulting in an accuracy of m 12 keV for all isotopes investigated. Con icts with existing mass data of several standard deviations were found. peerReviewed
SMILETRAP — Atomic mass measurements with ppb accuracy by using highly charged ions
In the SMILETRAP facility externally produced highly charged ions are captured in a Penning trap and utilized for high precision measurements of atomic masses. Accuracy tests on a ppb level have been performed, using highly charged carbon, oxygen and neon ions. In all cases hydrogen ions served as a reference for the calibration and monitoring of the magnetic field in the trap. Deviations smaller than 3 ppb from the expected results were found in mass measurements of the16O and20Ne atomic masses. The proton atomic mass, determined from the reference measurements on hydrogen ions, is in good agreement with the accepted value [1]. A direct mass measurement on the86Kr-isotope, using trapped86K…
The Stockholm–Mainz ion trap project
A new ion trap facility is described which is dedicated to studies of highly charged ions in a Penning trap. Such a trap will be connected to sources of highly charged ions, in particular the electron beam ion source CRYSIS, at the Manne Siegbahn Institute for Physics. The use of highly charged ions in a Penning trap increases the cyclotron frequency with a factor proportional to the charge which leads to a higher resolution. Also, the possibility to vary the charge state makes it possible to search for and identify different systematic effects. Thus, a substantial increase in accuracy can be expected. In addition, the combination of high charge state ions and a Penning trap allows new appl…
First absolute mass measurements of short-lived isotopes
Absolute mass measurements of short-lived isotopes have been performed at the on-line mass separator ISOLDE at CERN by determining the cyclotron frequencies of ions confined in a Penning trap. The cyclotron frequencies for77,78,85,86,88Rb and88Sr ions could be determined with a resolving power of 3×105 and an accuracy of better than 10−6, which corresponds to 100 keV for massA=100. The shortest-lived isotope under investigation was77Rb with a half-life of 3.7 min. The resonances obtained for the isobars88Rb and88Sr were clearly resolved.
Highly-charged ions in a penning trap: mass measurements, etc.
The use of a Penning trap will start a new generation of precision experiments on highly charged ions. The long storage time of the ions in combination with a controlled confinement in a very small volume will enable accuracies in mass determination better than δm/m = 10-8.
High-power pulsed dye laser with Fourier-limited bandwidth
A high-peak-power, narrow-linewidth light source with a homogeneous beam profile has been constructed by modifications to a commercially available pulsed-dye-laser system. Output pulses of up to 10 mJ were generated with linewidths of about 50 MHz for 12-nsec pulses. The pulse-to-pulse frequency stability was better than the linewidth, and the center frequency could be scanned over a frequency range of 142.5 GHz at a wavelength of 600 nm. The performance of the system was demonstrated by observing the 6s2 1S0–6s7s1S0 transition in atomic mercury at 2λ = 312.8 nm and the 6s2S1/2–8s2S1/2 transition in atomic gold at 2λ = 308.9 nm using up to 1 mJ of frequency-doubled output for two-photon non…
Direct determination of the mass of28Si as a contribution to a new definition of the kilogram
The mass of 28Si has been determined to be m(28Si) = 27.976 926 57(30) u by comparing the cyclotron frequencies of the singly charged ions 12C+, 12C+3 and 28Si+ in a Penning trap mass spectrometer. The experimental technique and the setup are described. The obtained accuracy as well as possible improvements are discussed. Our measurements are related to current efforts to base the kilogram on atomic properties by using an almost perfect single crystal of silicon.
Penning-trap mass measurements of neutron-deficient Rb and Sr isotopes
Abstract The Penning-trap mass spectrometer ISOLTRAP installed at the on-line mass separator ISOLDE 2 at CERN has been used for mass determination of 75–87 Rb and 78–83,87 Sr. Ions are captured in a Penning trap and their cyclotron frequency ω c = ( q m )B in the trapping field B is measured. Ratios of these frequencies lead to the determination of the atomic mass of these isotopes. A resolving power of typically m Δm = 10 6 and an accuracy of δm ≈10 keV is obtained. The mass of 78 Sr is measured for the first time and, in most cases, the mass values of the other isotopes are significantly improved. The experimental masses are compared with theoretical predictions.
High-Accuracy Mass Determination of Unstable Rb, Sr, Cs, Ba, Fr and Ra Isotopes with a Penning Trap Mass Spectrometer
The majority of masses of radioactive isotopes has been measured by determination of Q-values in nuclear reactions or in nuclear decay. For a long time the use of direct mass determination has been limited to stable isotopes or isotopes close to stability. This changed in the 70’s with magnetic spectrometers put on-line to isotope separators. The Orsay group (Audi et al., 1986) succeeded in measuring the masses in long isotope chains of alkali elements. They impressively demonstrated the possibilities embedded in direct mass determination of isotopes far from stability. The persisting demand for more precise masses of short-lived isotopes (or exotic particles) has prompted during recent yea…
Mass Determination of Francium and Radium Isotopes by a Penning Trap Mass Spectrometer
Abstract A tandem Penning trap mass spectrometer is used for mass measurement of radioactive isotopes produced at the on-line isotope separator ISOLDE/CERN. The mass is determined directly and with high accuracy by measuring the cyclotron frequency of the stored ions. Measurements were performed on 209 210 211 212 221 222Fr and 226 230Ra. A resolving power of 5 × 105 was used and an accuracy of 1·8 × 10−7 has been achieved.
ISOLTRAP: A tandem penning trap mass spectrometer for radioactive isotopes
The masses of over sixty short-lived Rb, Sr, Cs, Ba, Fr and Ra isotopes have been measured at the on-line mass separator ISOLDE at CERN/Geneva by determination of their cyclotron frequency in the tandem Penning trap system ISOLTRAP. Resolving powers exceedingm/Δm(FWHM)=106 and accuracies of typically δm/m=10−7 could be achieved. ISOLTRAP can also act as an isomer separator, as proven for the cases of84Rb and78Rb.
Nuclear physics with ion traps at ISOLDE: present and future
Nuclear physics experiments with ion traps started at the on-line separator ISOLDE/CERN, Geneva, with the installation of the tandem Penning trap mass spectrometer ISOLTRAP. With this device the massM of a stored ion is determined by measuring its cyclotron frequency θc=(q/M)B in a magnetic fieldB. Mass measurements with a resolving powerR=θc/Δθc(FWHM)≈1×106 and accuracies of δM/M≈10−7 were performed on more than sixty unstable isotopes of the elements Rb, Sr, Cs, Ba, Fr, and Ra.
High-precision masses of neutron-deficient rubidium isotopes using a Penning trap mass spectrometer
The atomic masses of the neutron-deficient radioactive rubidium isotopes $^{74-77,79,80,83}$Rb have been measured with the Penning trap mass spectrometer ISOLTRAP. Using the time-of-flight cyclotron resonance technique, relative mass uncertainties ranging from $1.6 \times 10^{-8}$ to $5.6 \times 10^{-8}$ were achieved. In all cases, the mass precision was significantly improved as compared with the prior Atomic-Mass Evaluation; no significant deviations from the literature values were observed. The exotic nuclide $^{74}$Rb with a half-life of only 65 ms, is the shortest-lived nuclide on which a high-precision mass measurement in a Penning trap has been carried out. The significance of these…
Ground-state properties of neutron-deficient platinum isotopes
The hyperfine structure splitting and the isotope shift in the λ=266 nm transition of Pt isotopes within the mass range 183 ≦A≦ 198 have been determined by Resonance Ionization Mass Spectroscopy (RIMS) in combination with Pulsed-Laser Induced Desorption (PLID). The Pt isotopes were obtained at the on-line isotope separator ISOLDE-3/CERN as daugthers of the primarily produced Hg isotopes. Magnetic moments, quadrupole moments, and changes in the mean-square charge radii are deduced and compared with results of a particle-triaxial rotor model and mean field calculations. Good agreement with experimental data (including nuclear level schemes and transition probabilities) can only be obtained if…
Sudden change in the nuclear charge distribution of very light gold isotopes
4 pages, 3 tables, 2 figures.-- PACS nrs.: 21.10.Ft, 21.10.Ky, 27.70.+q.
Precision mass measurements using a penning trap and highly charged ions produced in an electron beam ion source
A method for precision mass measurements in a Penning trap using highly charged ions produced in an electron beam ion source (CRYSIS) has been developed. The cyclotron frequencies for O8+, 7+, 6+, 5+ and Ar18+, 17+, 16+, 15+, 14+, 13+ ions have been determined by the excitation of the sum frequency v+ + v−. In addition to CRYSIS ions, H+, H2+ and He+ ions were produced by electron bombardment of the H2 rest gas or helium gas introduced through an UHV leak valve into an auxiliary ion trap (or a pre-trap). A technique for fast (seconds) interchanging of the ion species in the precision trap has been implemented to reduce the long term magnetic field drift.
The SMILETRAP facility
The SMILETRAP experimental set-up, a Penning trap mass spectrometer for highly charged ions, is described. Capture and observation of cyclotron frequencies of externally produced highly charged ions, rapid interchange of investigated and reference ions and measurements of the rotational kinetic energies are demonstrated. Mass measurements utilizing different charge states and species to verify the consistency of the measurements are presented. A relative uncertainty of about 10−9 is attained in comparisons between highly charged carbon, nitrogen, oxygen, neon and the singly charged hydrogen molecule.
Cluster isobars for high-precision mass spectrometry
Doublet mass measurements of the isobars28Si3 and12C7 are performed by use of a Penning trap mass spectrometer and the Fourier transform ion cyclotron resonance (FT-ICR). The carbon and silicon cluster ions are produced by laser ablation. Results of these preliminary measurements are presented.
Ion traps — recent applications and developments
Abstract Paul and Penning traps are now widely applied in chemistry and physics laboratories. They are used as storage devices, as tools for precision spectroscopy and metrology, and as mass spectrometers. Direct mass measurements of short-lived Rb, Sr, Cs, Ba, Fr and Ra isotopes were performed at the on-line mass separator ISOLDE at CERN, Geneva, by means of a tandem Penning trap system. The ions from ISOLDE are captured and cooled in a first trap and trasnferred to a second trap. Here the mass of the trapped ions is determined by measuring their cyclotron frequency. Resolving powers exceeding m/Δm (FWHM) = 106 could be achieved. Mass values of about 60 isotopes have been determined with a…
Accurate mass determination of short-lived isotopes by a tandem Penning-trap mass spectrometer
A mass spectrometer consisting of two Penning traps has been set up for short-lived isotopes at the on-line mass separator ISOLDE at CERN. The ion beam is collected and cooled in the first trap. After delivery to the second trap, high-accuracy direct mass measurements are made by determining the cyclotron frequency of the stored ions. Measurements have been performed for $^{118}--^{137}$Cs. A resolving power of over ${10}^{6}$ and an accuracy of 1.4\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}7}$ have been achieved, corresponding to about 20 keV.
Resolution of nuclear ground and isomeric states by a Penning trap mass spectrometer.
Ground and isomeric states of a nucleus have been resolved for the first time by mass spectrometry. Measurements on $^{78}\mathrm{Rb}^{\mathit{m},}$g and $^{84}\mathrm{Rb}^{\mathit{m},}$g were performed using a tandem Penning trap mass spectrometer on-line with the isotope separator ISOLDE/CERN. The effects of ion-ion interaction were investigated for two ion species differing in mass and stored simultaneously in the trap.
ISOLTRAP Mass Measurements for Weak-Interaction Studies
International audience; The conserved-vector-current (CVC) hypothesis of the weak interaction and the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix are two fundamental postulates of the Standard Model. While existing data on CVC supports vector current conservation, the unitarity test of the CKM matrix currently fails by more than two standard deviations. High-precision mass measurements performed with the ISOLTRAP experiment at ISOLDE/CERN provide crucial input for these fundamental studies by greatly improving our knowledge of the decay energy of super-allowed beta decays. Recent results of mass measurements on the beta emitters 18Ne, 22Mg, 34Ar, and 74Rb as pertaining to weak-i…
Precision Measurements of Atomic Masses Using Highly Charged Ions and Atomic Clusters
A high precision Penning trap will be connected to the beam of highly charged ions from the electron beam ion source CRYSIS at the Manne Siegbahn Institute for Physics (MSI) in Stockholm. The first series of experiments aim at accurate mass measurements by exploiting the increase of the cyclotron frequency with the charge state of the trapped ion. Using charged states of about 50 it should be possible to achieve relative mass accuracies for mass doublets better than 10-9. For this high accuracy a Penning trap with low imperfections is needed, as well as a sophisticated beam handling and retardation system for controlled injection of the ions into the trap. In order to minimize the effect of…