Towards high-accuracy mass spectrometry of highly charged short-lived ions at ISOLTRAP

Dedicated to H.-J. Kluge on the occasion of his 65th birthday anniversary - Jürgen Kluge Special Issue; Multiply charged ions of stable xenon isotopes from a plasma ion source have been mass-selected by the on-line mass separator ISOLDE/CERN and delivered to the triple-trap mass spectrometer ISOLTRAP. The doubly charged ions that survived the charge-exchange processes during bunching and ion preparation were transferred to a precision Penning trap for mass determination. Mass values were obtained for the isotopes with mass numbers A=126,129,130,136. They are consistent with previous results except for the case of $^{126}Xe$ where a significant deviation from the literature value was found. …

Erratum to: “Mass measurements on neutron-deficient Sr and neutron-rich Sn isotopes with the ISOLTRAP mass spectrometer” [Nucl. Phys. A 763 (2005) 45]

Mass Measurement on the rp-Process Waiting Point 72Kr

The mass of one of the three major waiting points in the astrophysical rp process $^{72}$Kr was measured for the first time with the Penning trap mass spectrometer ISOLTRAP. The measurement yielded a relative mass uncertainty of $\deltam/m = 1.2\times 10–7 (\deltam$ = 8 keV). $^{73,74}$Kr, also needed for astrophysical calculations, were measured with more than 1 order of magnitude improved accuracy. We use the ISOLTRAP masses of $^{72–74}$Kr to reanalyze the role of $^{72}$Kr (T$_{1/2}$ = 17.2 s) in the rp process during x-ray bursts and conclude that $^{72}$Kr is a strong waiting point delaying the burst duration with at least 80\% of its $\beta$-decay half-life.

Eine Waage für exotische Kerne: Massenbestimmung von Atomkernen mit Isoltrap

Die prazise Massenbestimmung von Atomkernen ist fur verschiedene Gebiete der Physik interessant. Penning-Fallen-Massenspektrometer wie Isoltrap am CERN konnen auch kurzlebige exotische Kerne “wiegen”, die zuvor im Labor erzeugt wurden. Die genaue Kenntnis ihrer Masse ist ein Schlussel zum Verstandnis dafur, wie Sterne, Novae und Supernovae Elemente erbruten, die schwerer als Helium sind. Isoltrap ermoglicht auch einen Test des Standardmodells: Die prazise Bestimmung von Kernmassen vor und nach einem radioaktiven Zerfall liefert wichtige Informationen uber die Natur der elektroschwachen Wechselwirkung.

Mass spectrometry and decay spectroscopy of isomers across the Z=82 shell closure

Recent results from a measurement campaign studying the isomerism in neutron-deficient Tl isotopes are presented. The measurements make use of a nuclear spectroscopy setup coupled to the high-resolution Penning-trap mass spectrometer ISOLTRAP at CERN's radioactive ion-beam facility ISOLDE. The mass values of 190,194Tl are improved and a mass-spin-state assignment is carried out. An additional mass measurement of the grandparent nuclide 198At allows the deduction of the spin-state ordering in 190Tl. As a result, the excitation energies of the isomers in both Tl isotopes are determined for the first time to Eex(194Tl)=260(15) keV and E ex(190Tl)=89(12) keV. Furthermore, this allows anchoring …

Direct mass measurements of neutron-deficient xenon isotopes with the ISOLTRAP mass spectrometer

Abstract 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 500 000 was chosen resulting in an accuracy of δm ≈12 keV for all isotopes investigated. Conflicts with existing mass data of several standard deviations were found.

Octupolar-Excitation Penning-Trap Mass Spectrometry forQ-Value Measurement of Double-Electron Capture inEr164

The theory of octupolar-excitation ion-cyclotron-resonance mass spectrometry is presented which predicts an increase of up to several orders of magnitude in resolving power under certain conditions. The new method has been applied for a direct Penning-trap mass-ratio determination of the $^{164}\mathrm{Er}\mathrm{\text{\ensuremath{-}}}^{164}\mathrm{Dy}$ mass doublet. $^{164}\mathrm{Er}$ is a candidate for the search for neutrinoless double-electron capture. However, the measured ${Q}_{ϵϵ}$ value of 25.07(12) keV results in a half-life of ${10}^{30}$ years for a 1 eV Majorana-neutrino mass.

Surveying the N=40 island of inversion with new manganese masses

High-precision mass measurements of neutron-rich 57−66Mn and 61−63Fe isotopes are reported. The new mass surface shows no shell closure at N=40. In contrast, there is an increase of the two-neutron separation energy at N=38. This behavior is consistent with the onset of collectivity due to the occupation of intruder states from higher orbits, in analogy with the well known “island of inversion” around N=20. Our results indicate that the neutron-rich Mn isotopes, starting from 63Mn, are most likely within the new island of inversion. From the new mass surface, we evaluate the empirical proton-neutron interaction and the pairing gap, both playing a significant role in the structural changes i…

Probing the nuclide 180W for neutrinoless double-electron capture exploration

Abstract The mass difference of the nuclides 180 W and 180 Hf has been measured with the Penning-trap mass spectrometer SHIPTRAP to investigate 180 W as a possible candidate for the search for neutrinoless double-electron capture. The Q ϵ ϵ -value was measured to 143.20(27) keV. This value in combination with the calculations of the atomic electron wave functions and other parameters results in a half-life of the 0 + → 0 + ground-state to ground-state double-electron capture transition of approximately 5 × 10 27 years / 〈 m ϵ ϵ [ eV ] 〉 2 .

Double-βtransformations in isobaric triplets with mass numbersA=124, 130, and 136

The Q values of double-electron capture in ${}^{124}$Xe, ${}^{130}$Ba, and ${}^{136}$Ce and double-beta decay of ${}^{124}$Sn and ${}^{130}$Te have been determined with the Penning-trap mass spectrometer SHIPTRAP with a few hundred eV uncertainty. These nuclides are members of three isobaric triplets with common daughter nuclides. The main goal of this work was to investigate the existence of the resonant enhancement of the neutrinoless double-electron-capture rates in ${}^{124}$Xe and ${}^{130}$Ba in order to assess their suitability for the search for neutrinoless double-electron capture. Based on our results, in neither of these cases is the resonance condition fulfilled.

A linear radiofrequency ion trap for accumulation, bunching, and emittance improvement of radioactive ion beams

An ion beam cooler and buncher has been developed for the manipulation of radioactive ion beams. The gas-filled linear radiofrequency ion trap system is installed at the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. Its purpose is toaccumulate the 60-keV continuous ISOLDE ion beam with high efficiency and to convert it into low-energy low-emittance ion pulses. The efficiency was found to exceed 10\,\% in agreement with simulations. A more than 10-fold reduction of the ISOLDE beam emittance can be achieved. The system has been used successfully for first on-line experiments. Its principle, setup and performance will be discussed. An ion beam cooler and buncher has been developed fo…

Time-separated oscillatory fields for high-precision mass measurements on short-lived Al and Ca nuclides

High-precision Penning trap mass measurements on the stable nuclide 27Al as well as on the short-lived radionuclides 26Al and 38,39Ca have been performed by use of radiofrequency excitation with time-separated oscillatory fields, i.e. Ramsey's method, as recently introduced for the excitation of the ion motion in a Penning trap, was applied. A comparison with the conventional method of a single continuous excitation demonstrates its advantage of up to ten times shorter measurements. The new mass values of 26,27Al clarify conflicting data in this specific mass region. In addition, the resulting mass values of the superallowed beta-emitter 38Ca as well as of the groundstate of the beta-emitte…

TRIGA-SPEC: A setup for mass spectrometry and laser spectroscopy at the research reactor TRIGA Mainz

The research reactor TRIGA Mainz is an ideal facility to provide neutron-rich nuclides with production rates sufficiently large for mass spectrometric and laser spectroscopic studies. Within the TRIGA-SPEC project, a Penning trap as well as a beam line for collinear laser spectroscopy are being installed. Several new developments will ensure high sensitivity of the trap setup enabling mass measurements even on a single ion. Besides neutron-rich fission products produced in the reactor, also heavy nuclides such as 235-U or 252-Cf can be investigated for the first time with an off-line ion source. The data provided by the mass measurements will be of interest for astrophysical calculations on…

Breakdown of the Isobaric Multiplet Mass Equation atA=33,T=3/2

Mass measurements on ${}^{33,34,42,43}\mathrm{Ar}$ were performed using the Penning trap mass spectrometer ISOLTRAP and a newly constructed linear Paul trap. This arrangement allowed us, for the first time, to extend Penning trap mass measurements to nuclides with half-lives below one second ( ${}^{33}\mathrm{Ar}$: ${T}_{1/2}\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}174\mathrm{ms}$). A mass accuracy of about ${10}^{\ensuremath{-}7}$ $(\ensuremath{\delta}m\ensuremath{\approx}4\mathrm{keV})$ was achieved for all investigated nuclides. The isobaric multiplet mass equation was checked for the $A\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}33$, $T\phantom{\rule{0ex}{0ex}}=\phantom…

Approaching theN=82shell closure with mass measurements of Ag and Cd isotopes

Mass measurements of neutron-rich Cd and Ag isotopes were performed with the Penning trap mass spectrometer ISOLTRAP. The masses of ${}^{112,114\ensuremath{-}124}$Ag and ${}^{114,120,122\ensuremath{-}124,126,128}$Cd, determined with relative uncertainties between $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ and $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}$, resulted in significant corrections and improvements of the mass surface. In particular, the mass of $^{124}\mathrm{Ag}$ was previously unknown. In addition, other masses that had to be inferred from $Q$ values of nuclear decays and reactions have now been measured directly. The analysis includes various mass…

Accurate masses of neutron-deficient nuclides close to

Abstract Mass measurements with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN are extended to nonsurface ionizable species using newly developed ion-beam bunching devices. Masses of 179–197Hg, 196,198Pb, 197Bi, 198Po and 203At were determined with an accuracy of 1×10 −7 corresponding to δm≈20  keV. Applying a resolving power of up to 3.7×10 6 ground and isomeric states of 185,187,191,193,197Hg were separated. First experimental values for the isomeric excitation energy of 187,191Hg are obtained. A least-squares adjustment has been performed and theoretical approaches are discussed to model the observed fine structure in the binding energy.

Trapped charged particles and fundamental interactions

Low-Energy Precision Tests of Electroweak Theory.- Principles of Ion Traps.- Simulations for Ion Traps Methods and Numerical Implementation.- Simulations for Ion Traps Buffer Gas Cooling.- Highly-charged ions and high-resolution mass spectrometry in a Penning trap.- Fundamental tests with trapped antiprotons.

High-precision Penning-trap mass measurements of heavy xenon isotopes for nuclear structure studies

With the double Penning-trap mass spectrometer ISOLTRAP at ISOLDE/CERN the masses of the neutron-rich isotopes $^{136\ensuremath{-}146}\mathrm{Xe}$ were measured with a relative uncertainty of the order of ${10}^{\ensuremath{-}8}$ to ${10}^{\ensuremath{-}7}$. In particular, the masses of $^{144\ensuremath{-}146}\mathrm{Xe}$ were measured for the first time. These new mass values allow one to extend calculations of the mass surface in this region. Proton-Neutron interaction strength, obtained from double differences of binding energies, relate to subtle structural effects, such as the onset of octupole correlations, the growth of collectivity, and its relation to the underlying shell model l…

Towards Shorter-Lived Nuclides in ISOLTRAP Mass Measurements

Recently, the applicability of Penning trap mass spectrometry has been extended to nuclides with a half-life of less than one second. The mass of 33Ar(T 1/2 = 174 ms) was measured using the ISOLTRAP spectrometer with an accuracy of 4.2 keV. This measurement provided a stringent test of the Isobaric Multiplet Mass Equation (IMME) at mass number A = 33 and isospin T = 3/2. The fast measurement cycle that shows the way to other measurements of very-short-lived nuclides is presented. Furthermore, the results of the IMME test are displayed.

Extension of Penning-trap mass measurements to very short-lived nuclides

Abstract Mass measurements on 33,34,42,43 Ar have been performed at the ISOLTRAP spectrometer. An accuracy of δm ≈4 keV has been achieved for all measured isotopes. With 33 Ar it is the first time that a nuclide with a half-life shorter than one second has been investigated using a Penning trap. This became possible due to the recently installed linear radio-frequency ion-trap system and an improved, faster measurement cycle.

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…

Recent Upgrades of the SHIPTRAP Setup: On the Finish Line Towards Direct Mass Spectroscopy of Superheavy Elements

With the Penning-trap mass spectrometer SHIPTRAP at GSI, Darmstadt, it is possible to investigate exotic nuclei in the region of the heaviest elements. Few years ago, challenging experiments led to the direct measurements of the masses of neutron-deficient isotopes with Z = 102,103 around N = 152. Thanks to recent advances in cooling and ion-manipulation techniques, a major technical upgrade of the setup has been recently accomplished to boost its efficiency. At present, the gap to reach more rare and shorter-lived species at the limits of the nuclear landscape has been narrowed. ispartof: pages:423-429 ispartof: Acta Physica Polonica B vol:48 issue:3 pages:423-429 ispartof: location:Zakopa…

Towards high-precision mass measurements on 74Rb for a test of the CVC hypothesis and the unitarity of the CKM matrix

At the highest possible precisions, atomic-mass measurements can be used to perform fundamental studies. Examples for such studies are a check of the conserved-vector-current (CVC) hypothesis and the unitarity of the Cabibbo-Kobayashi-Maskawa (CKM) matrix, both postulates of the Standard Model. The comparative half-lives Ft of superallowed β decays constitute the nuclear-physics access to these tests. The Q value of the β decay of 74 Rb, one of the three experimentally accessible parameters that enter into the Ft values, has been measured with the ISOLTRAP experiment at ISOLDE/CERN. The ultimate mass precision requirement and the way to achieve it are outlined.

Restoration of theN=82Shell Gap from Direct Mass Measurements ofSn132,134

A high-precision direct Penning trap mass measurement has revealed a 0.5-MeV deviation of the binding energy of (134)Sn from the currently accepted value. The corrected mass assignment of this neutron-rich nuclide restores the neutron-shell gap at N=82, previously considered to be a case of "shell quenching." In fact, the new shell gap value for the short-lived (132)Sn is larger than that of the doubly magic (48)Ca which is stable. The N=82 shell gap has considerable impact on fission recycling during the r process. More generally, the new finding has important consequences for microscopic mean-field theories which systematically deviate from the measured binding energies of closed-shell nu…

Mass Measurements of Very Neutron-Deficient Mo and Tc Isotopes and Their Impact on rp Process Nucleosynthesis

The masses of ten proton-rich nuclides, including the N=Z+1 nuclides 85-Mo and 87-Tc, were measured with the Penning trap mass spectrometer SHIPTRAP. Compared to the Atomic Mass Evaluation 2003 a systematic shift of the mass surface by up to 1.6 MeV is observed causing significant abundance changes of the ashes of astrophysical X-ray bursts. Surprisingly low alpha-separation energies for neutron-deficient Mo and Tc are found, making the formation of a ZrNb cycle in the rp process possible. Such a cycle would impose an upper temperature limit for the synthesis of elements beyond Nb in the rp process.

Accurate mass measurements on neutron-deficient krypton isotopes

soumis à Nuclear Physics A; The masses of $^{72-78,80,82,86}$Kr were measured directly with the ISOLTRAP Penning trap mass spectrometer at ISOLDE/CERN. For all these nuclides, the measurements yielded mass uncertainties below 10 keV. The ISOLTRAP mass values for $^{72-75}$Kr outweighed previous results obtained by means of other techniques, and thus completely determine the new values in the Atomic-Mass Evaluation. Besides the interest of these masses for nuclear astrophysics, nuclear structure studies, and Standard Model tests, these results constitute a valuable and accurate input to improve mass models. In this paper, we present the mass measurements and discuss the mass evaluation for t…

High-accuracy mass measurements of neutron-rich Kr isotopes

The atomic masses of the neutron-rich krypton isotopes {sup 84,86-95}Kr have been determined with the tandem Penning trap mass spectrometer ISOLTRAP with uncertainties ranging from 20 to 220 ppb. The masses of the short-lived isotopes {sup 94}Kr and {sup 95}Kr were measured for the first time. The masses of the radioactive nuclides {sup 89}Kr and {sup 91}Kr disagree by 4 and 6 standard deviations, respectively, from the present Atomic-Mass Evaluation database. The resulting modification of the mass surface with respect to the two-neutron separation energies as well as implications for mass models and stellar nucleosynthesis are discussed.

Mass measurements on unstable Sn and Sr isotopes with the ISOLTRAP mass spectrometer

Direct mass measurements have been performed on the isotopes 76,77,80,81Sr and 129,130,131,132Sn by means of the Penning trap mass spectrometer ISOLTRAP at ISOLDE/CERN. In the case of 76Sr the mass was measured for the first time and an accuracy of about 30 keV was reached (Fig. 1). The masses of the tin isotopes are known for a long time from Q β measurements.

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…

How to measure nuclear ground-state properties in simple systems such as 11Li or U91+?

Abstract Atomic spectroscopy yields key information on properties of ground and isomeric states via a determination of the hyperfine structure and isotope shift. In order to deduce precise nuclear moments and charge radii, the electromagnetic fields produced by the electrons at the site of the nucleus must be known with high accuracy. This is presently possible only for simple systems with very few electrons. This contribution describes two scenarios for such experiments: the determination of the charge radius of the neutron-rich isotopes 8,9Li and of the halo nucleus 11Li at the on-line isotope separators at GSI and TRIUMF and the Highly charged Ion TRAP (HITRAP) facility which is under co…

Mass Measurement on therp-Process Waiting PointKr72

With the aim of improving nucleosynthesis calculations, we performed for the first time, a direct high-precision mass measurement on the waiting point in the astrophysical rp-process 72Kr. We used the ISOLTRAP Penning trap mass spectrometer located at ISOLDE/CERN. The measurement yielded a relative mass uncertainty of δm/m = 1.2×10-7. In addition, the masses of 73Kr and 74Kr were measured directly with relative mass uncertainties of 1.0×10-7 and 3×10-8, respectively. We analyzed the role of 72Kr in the rp-process during X-ray bursts using the ISOLTRAP and previous mass values of 72-74Kr.

High-accuracy mass measurements on neutron deficient neon isotopes

International audience; The atomic masses of the short-lived nuclides 17Ne and 19Ne have been measured with the triple-trap mass spectrometer ISOLTRAP at ISOLDE/CERN. The obtained mass excess for both nuclides deviates significantly from the literature value, in the case of 17Ne about 40 keV. The mass value of 17Ne can be applied for a test of the isobaric multiplet mass equation with respect to an isospin T = 3/2 quartet. In addition, both masses can contribute to the data analysis of collinear laser-spectroscopy experiments where mean-square nuclear-charge radii are determined.

Schottky mass measurements of stored and cooled neutron-deficient projectile fragments in the element range of 57≤Z≤84

Abstract A novel method for direct, high precision mass measurements of relativistic exotic nuclei has been successfully applied in the storage ring ESR at GSI. The nuclei of interest were produced by projectile fragmentation of 930 MeV / u bismuth ions, separated in-flight by the fragment separator FRS, stored and cooled in the ESR. The mass values have been deduced from the revolution frequencies of the coasting cooled ions. We have measured 104 new mass values with a precision of about 100 keV and a resolving power of 3.5×10 5 for the neutron-deficient isotopes of the elements 57≤Z≤84 . This paper presents the experimental method, the mass evaluation and a table of the experimental mass …

Mass measurements of $^{56-57}$Cr and the question of shell reincarnation at N = 32

Binding energies determined with high accuracy provide smooth derivatives of the mass surface for analysis of shell and pairing effects. Measurements with the Penning trap mass spectrometer ISOLTRAP at CERN-ISOLDE were made for $^{56-57}$Cr for which an accuracy of 4 $\times 10^{-8}$ was achieved. Analysis of the mass surface for the supposed new N = 32 shell closure rather indicates a sub-shell closure, but of a different nature than known cases such as $^{94}$Sr.