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TITAN mass measurements of neutron-rich Cs, Ba and r-process lanthanide abundances
Authors:
T. -H. Yeh,
J. D. Cardona,
Y. Wang,
J. Ash,
B. Ashrafkhani,
I. Belosovic,
J. Bergmann,
E. Dunling,
L. Egoriti,
G. Gelinas,
G. Gwinner,
Z. Hockenbery,
C. Izzo,
A. Jacobs,
S. Kakkar,
B. Kootte,
E. M. Lykiardopoulou,
T. Murbock,
A. Mollaebrahimi,
A. Ridley,
S. F. Paul,
W. S. Porter,
M. P. Reiter,
J. Ringuette,
R. Simpson
, et al. (4 additional authors not shown)
Abstract:
We present measurements for the masses of five neutron-rich isotopes, $^{149-151}$Cs and $^{151, 152}$Ba, probed for the first time by TITAN at TRIUMF with time-of-flight measurement techniques. We propagate these masses to the nuclear reaction and decay data required for the simulation of the rapid neutron capture process (r-process) nucleosynthesis in neutron star mergers. We show that these neu…
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We present measurements for the masses of five neutron-rich isotopes, $^{149-151}$Cs and $^{151, 152}$Ba, probed for the first time by TITAN at TRIUMF with time-of-flight measurement techniques. We propagate these masses to the nuclear reaction and decay data required for the simulation of the rapid neutron capture process (r-process) nucleosynthesis in neutron star mergers. We show that these neutron-rich masses affect the abundance predictions near mass number $A\sim148-152$ corresponding to lanthanide element abundances at $Z=60,\,62$ and $63$. We demonstrate that these new TITAN masses smooth out the odd-even effect in isotopic abundance predictions near $A\sim150$ in both fission cycling astrophysical conditions and conditions that do not reach actinides. We further show that these new masses adjust how fission fragments settle into place when forming the final abundances, and consider the effect on comparisons with stellar abundance ratios such as [Ag/Eu], [Sm/Eu], and [Nd/Eu].
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Submitted 5 August, 2026;
originally announced August 2026.
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Precision mass measurements of $^{74-76}$Sr using TITAN's Multiple-Reflection Time-of-Flight Mass Spectrometer
Authors:
Z. Hockenbery,
T. Murböck,
B. Ashrafkhani,
J. Bergmann,
C. Brown,
T. Brunner,
J. Cardona,
T. Dickel,
E. Dunling,
J. D. Holt,
C. Hornung,
B. S. Hu,
C. Izzo,
A. Jacobs,
A. Javaji,
S. Kakkar,
B. Kootte,
G. Kripko-Koncz,
Ali Mollaebrahimi,
D. Lascar,
E. M. Lykiardopoulou,
I. Mukul,
S. F. Paul,
W. R. Plaß,
W. S. Porter
, et al. (7 additional authors not shown)
Abstract:
We report precision mass measurements of $^{74-76}$Sr performed with the TITAN Multiple-Reflection Time-of-Flight Mass Spectrometer. This marks a first time mass measurement of $^{74}$Sr and gives increased mass precision to both $^{75}$Sr and $^{76}$Sr which were previously measured using storage ring and Penning trap methods, respectively. This completes the A = 74, T = 1 isospin triplet and giv…
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We report precision mass measurements of $^{74-76}$Sr performed with the TITAN Multiple-Reflection Time-of-Flight Mass Spectrometer. This marks a first time mass measurement of $^{74}$Sr and gives increased mass precision to both $^{75}$Sr and $^{76}$Sr which were previously measured using storage ring and Penning trap methods, respectively. This completes the A = 74, T = 1 isospin triplet and gives increased precision to the A = 75, T = 1/2 isospin doublet which are both the heaviest experimentally evaluated triplets and doublets to date. The new data allow us to evaluate coefficients of the isobaric multiplet mass equation for the first time at A = 74, and with increased precision at A = 75. With increased precision of 75Sr, we confirm the recent measurement reported by CSRe which was used to remove a staggering anomaly in the doublets. New ab initio valence-space in-medium similarity renormalization group calculations of the T = 1 triplet are presented at A = 74. We also investigate the impact of the new mass data on the reaction flow of the rapid proton capture process in type I x-ray bursts using a single-zone model.
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Submitted 12 January, 2025;
originally announced January 2025.
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Convergence on the Proton Drip-Line in Thulium
Authors:
B. Kootte,
M. P. Reiter,
C. Andreoiu,
S. Beck,
J. Bergmann,
T. Brunner,
T. Dickel,
K. A. Dietrich,
J. Dilling,
E. Dunling,
J. Flowerdew,
L. Graham,
G. Gwinner,
Z. Hockenbery,
C. Izzo,
A. Jacobs,
A. Javaji,
R. Klawitter,
Y. Lan,
E. Leistenschneider,
E. M. Lykiardopoulou,
I. Miskun,
I. Mukul,
T. Murböck,
S. F. Paul
, et al. (13 additional authors not shown)
Abstract:
Direct observation of proton emission for very small Q-values is often unfeasible due to the long partial half-lives of the proton emission channel associated with tunneling through the Coulomb barrier. Therefore, proton emitters with very small decay energies may require the masses of both parent and daughter nuclei in order to establish them as proton unbound. Nuclear mass models have been used…
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Direct observation of proton emission for very small Q-values is often unfeasible due to the long partial half-lives of the proton emission channel associated with tunneling through the Coulomb barrier. Therefore, proton emitters with very small decay energies may require the masses of both parent and daughter nuclei in order to establish them as proton unbound. Nuclear mass models have been used to predict the proton drip-line of the thulium (Tm) isotopic chain ($Z=69$), but until now the proton separation energy has not been experimentally tested. Mass measurements were performed using a Multiple Reflection Time-Of-Flight Mass Spectrometer (MR-TOF-MS) at TRIUMF's TITAN facility to conclusively map the limit of proton-bound Tm. The masses of neutron-deficient, $^{149}$Tm and $^{150}$Tm, combined with measurements of $^{149m,g}$Er (which were found to deviate from literature by $\approx$150 keV), provide the first experimental confirmation that $^{149}$Tm is the first proton-unbound nuclide in the Tm chain. Our measurements also enable the strength of the $N=82$ neutron shell gap to be determined at the Tm proton drip-line, providing evidence supporting its continued existence.
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Submitted 9 August, 2025; v1 submitted 13 December, 2024;
originally announced December 2024.
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Collision-Induced Dissociation at TRIUMF's Ion Trap for Atomic and Nuclear science
Authors:
A. Jacobs,
C. Andreoiu,
J. Bergmann,
T. Brunner,
T. Dickel,
I. Dillmann,
E. Dunling,
J. Flowerdew,
L. Graham,
G. Gwinner,
Z. Hockenbery,
B. Kootte,
Y. Lan,
K. G. Leach,
E. Leistenschneider,
E. M. Lykiardopoulou,
V. Monier,
I. Mukul,
S. F. Paul,
W. R. Plaß,
M. P. Reiter,
C. Scheidenberger,
R. Thompson,
J. L Tracy,
C. Will
, et al. (4 additional authors not shown)
Abstract:
The performance of high-precision mass spectrometry of radioactive isotopes can often be hindered by large amounts of contamination, including molecular species, stemming from the production of the radioactive beam. In this paper, we report on the development of Collision-Induced Dissociation (CID) as a means of background reduction for experiments at TRIUMF's Ion Trap for Atomic and Nuclear scien…
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The performance of high-precision mass spectrometry of radioactive isotopes can often be hindered by large amounts of contamination, including molecular species, stemming from the production of the radioactive beam. In this paper, we report on the development of Collision-Induced Dissociation (CID) as a means of background reduction for experiments at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). This study was conducted to characterize the quality and purity of radioactive ion beams and the reduction of molecular contaminants to allow for mass measurements of radioactive isotopes to be done further from nuclear stability. This is the first demonstration of CID at an ISOL-type radioactive ion beam facility, and it is shown that molecular contamination can be reduced up to an order of magnitude.
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Submitted 18 October, 2022;
originally announced October 2022.
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Investigating nuclear structure near $N = 32$ and $N = 34$: Precision mass measurements of neutron-rich Ca, Ti and V isotopes
Authors:
W. S. Porter,
E. Dunling,
E. Leistenschneider,
J. Bergmann,
G. Bollen,
T. Dickel,
K. A. Dietrich,
A. Hamaker,
Z. Hockenbery,
C. Izzo,
A. Jacobs,
A. Javaji,
B. Kootte,
Y. Lan,
I. Miskun,
I. Mukul,
T. Murböck,
S. F. Paul,
W. R. Plaß,
D. Puentes,
M. Redshaw,
M. P. Reiter,
R. Ringle,
J. Ringuette,
R. Sandler
, et al. (10 additional authors not shown)
Abstract:
Nuclear mass measurements of isotopes are key to improving our understanding of nuclear structure across the chart of nuclides, in particular for the determination of the appearance or disappearance of nuclear shell closures. We present high-precision mass measurements of neutron-rich Ca, Ti and V isotopes performed at the TITAN and LEBIT facilities. These measurements were made using the TITAN mu…
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Nuclear mass measurements of isotopes are key to improving our understanding of nuclear structure across the chart of nuclides, in particular for the determination of the appearance or disappearance of nuclear shell closures. We present high-precision mass measurements of neutron-rich Ca, Ti and V isotopes performed at the TITAN and LEBIT facilities. These measurements were made using the TITAN multiple-reflection time-of-flight mass spectrometer (MR-ToF-MS) and the LEBIT 9.4T Penning trap mass spectrometer. In total, 13 masses were measured, eight of which represent increases in precision over previous measurements. These measurements refine trends in the mass surface around $N = 32$ and $N = 34$, and support the disappearance of the $N = 32$ shell closure with increasing proton number. Additionally, our data does not support the presence of a shell closure at $N = 34$.
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Submitted 11 August, 2022; v1 submitted 30 June, 2022;
originally announced June 2022.
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Mass measurements of $^{60-63}$Ga reduce x-ray burst model uncertainties and extend the evaluated $T=1$ isobaric multiplet mass equation
Authors:
S. F. Paul,
J. Bergmann,
J. D. Cardona,
K. A. Dietrich,
E. Dunling,
Z. Hockenbery,
C. Hornung,
C. Izzo,
A. Jacobs,
A. Javaji,
B. Kootte,
Y. Lan,
E. Leistenschneider,
E. M. Lykiardopoulou,
I. Mukul,
T. Murböck,
W. S. Porter,
R. Silwal,
M. B. Smith,
J. Ringuette,
T. Brunner,
T. Dickel,
I. Dillmann,
G. Gwinner,
M. MacCormick
, et al. (5 additional authors not shown)
Abstract:
We report precision mass measurements of neutron-deficient gallium isotopes approaching the proton drip line. The measurements of $^{60-63}$Ga performed with the TITAN multiple-reflection time-of-flight mass spectrometer provide a more than threefold improvement over the current literature mass uncertainty of $^{61}$Ga and mark the first direct mass measurement of $^{60}$Ga. The improved precision…
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We report precision mass measurements of neutron-deficient gallium isotopes approaching the proton drip line. The measurements of $^{60-63}$Ga performed with the TITAN multiple-reflection time-of-flight mass spectrometer provide a more than threefold improvement over the current literature mass uncertainty of $^{61}$Ga and mark the first direct mass measurement of $^{60}$Ga. The improved precision of the $^{61}$Ga mass has important implications for the astrophysical rp process, as it constrains essential reaction Q-values near the $^{60}$Zn waiting point. Based on calculations with a one-zone model, we demonstrate the impact of the improved mass data on prediction uncertainties of X-ray burst models. The first-time measurement of the $^{60}$Ga ground-state mass establishes the proton-bound nature of this nuclide; thus, constraining the location of the proton drip line along this isotopic chain. Including the measured mass of $^{60}$Ga further enables us to extend the evaluated $T=1$ isobaric multiplet mass equation up to $A=60$.
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Submitted 13 December, 2021; v1 submitted 24 November, 2021;
originally announced November 2021.
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Mass Measurements of Neutron-Rich Gallium Isotopes Refine Production of Nuclei of the First r-Process Abundance Peak in Neutron Star Merger Calculations
Authors:
M. P. Reiter,
S. Ayet San Andrés,
S. Nikas,
J. Lippuner,
C. Andreoiu,
C. Babcock,
B. R. Barquest,
J. Bollig,
T. Brunner,
T. Dickel,
J. Dilling,
I. Dillmann,
E. Dunling,
G. Gwinner,
L. Graham,
C. Hornung,
R. Klawitter,
B. Kootte,
A. A. Kwiatkowski,
Y. Lan,
D. Lascar,
K. G. Leach,
E. Leistenschneider,
G. Martínez-Pinedo,
J. E. McKay
, et al. (11 additional authors not shown)
Abstract:
We report mass measurements of neutron-rich Ga isotopes $^{80-85}$Ga with TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The measurements determine the masses of $^{80-83}$Ga in good agreement with previous measurements. The masses of $^{84}$Ga and $^{85}$Ga were measured for the first time. Uncertainties between $25-48$ keV were reached. The new mass values reduce the nuclear uncertain…
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We report mass measurements of neutron-rich Ga isotopes $^{80-85}$Ga with TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The measurements determine the masses of $^{80-83}$Ga in good agreement with previous measurements. The masses of $^{84}$Ga and $^{85}$Ga were measured for the first time. Uncertainties between $25-48$ keV were reached. The new mass values reduce the nuclear uncertainties associated with the production of A $\approx$ 84 isotopes by the \emph{r}-process for astrophysical conditions that might be consistent with a binary neutron star (BNS) merger producing a blue kilonova. Our nucleosynthesis simulations confirm that BNS merger may contribute to the first abundance peak under moderate neutron-rich conditions with electron fractions $Y_e=0.35-0.38$.
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Submitted 30 January, 2020; v1 submitted 26 October, 2018;
originally announced October 2018.
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Dawning of the N=32 shell closure seen through precision mass measurements of neutron-rich titanium isotopes
Authors:
E. Leistenschneider,
M. P. Reiter,
S. Ayet San Andrés,
B. Kootte,
J. D. Holt,
P. Navrátil,
C. Babcock,
C. Barbieri,
B. R. Barquest,
J. Bergmann,
J. Bollig,
T. Brunner,
E. Dunling,
A. Finlay,
H. Geissel,
L. Graham,
F. Greiner,
H. Hergert,
C. Hornung,
C. Jesch,
R. Klawitter,
Y. Lan,
D. Lascar,
K. G. Leach,
W. Lippert
, et al. (20 additional authors not shown)
Abstract:
A precision mass investigation of the neutron-rich titanium isotopes $^{51-55}$Ti was performed at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The range of the measurements covers the $N=32$ shell closure and the overall uncertainties of the $^{52-55}$Ti mass values were significantly reduced. Our results confirm the existence of a weak shell effect at $N=32$, establishing the abrupt…
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A precision mass investigation of the neutron-rich titanium isotopes $^{51-55}$Ti was performed at TRIUMF's Ion Trap for Atomic and Nuclear science (TITAN). The range of the measurements covers the $N=32$ shell closure and the overall uncertainties of the $^{52-55}$Ti mass values were significantly reduced. Our results confirm the existence of a weak shell effect at $N=32$, establishing the abrupt onset of this shell closure. Our data were compared with state-of-the-art \textit{ab-initio} shell model calculations which, despite very successfully describing where the $N=32$ shell gap is strong, overpredict its strength and extent in titanium and heavier isotones. These measurements also represent the first scientific results of TITAN using the newly commissioned Multiple-Reflection Time-of-Flight Mass Spectrometer (MR-TOF-MS), substantiated by independent measurements from TITAN's Penning trap mass spectrometer.
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Submitted 18 January, 2018; v1 submitted 23 October, 2017;
originally announced October 2017.
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Precision mass measurements of $^{125-127}$Cd isotopes and isomers approaching the $N=82$ closed shell
Authors:
D. Lascar,
R. Klawitter,
C. Babcock,
E. Leistenschneider,
S. R. Stroberg,
B. R. Barquest,
A. Finlay,
M. Foster,
A. T. Gallant,
P. Hunt,
J. Kelly,
B. Kootte,
Y. Lan,
S. F. Paul,
M. L. Phan,
M. P. Reiter,
B. Schultz,
D. Short,
J. Simonis,
C. Andreoiu,
M. Brodeur,
I. Dillmann,
G. Gwinner,
J. D. Holt,
A. A. Kwiatkowski
, et al. (2 additional authors not shown)
Abstract:
We present the results of precision mass measurements of neutron-rich cadmium isotopes. These nuclei approach the $N=82$ closed neutron shell and are important to nuclear structure as they lie near doubly-magic $^{132}$Sn on the chart of nuclides. Of particular note is the clear identification of the ground state mass in $^{127}$Cd along with the isomeric state. We show that the ground state ident…
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We present the results of precision mass measurements of neutron-rich cadmium isotopes. These nuclei approach the $N=82$ closed neutron shell and are important to nuclear structure as they lie near doubly-magic $^{132}$Sn on the chart of nuclides. Of particular note is the clear identification of the ground state mass in $^{127}$Cd along with the isomeric state. We show that the ground state identified in a previous mass measurement which dominates the mass value in the Atomic Mass Evaluation is an isomeric state. In addition to $^{127/m}$Cd, we present other cadmium masses measured ($^{125/m}$Cd and $^{126}$Cd) in a recent TITAN experiment at TRIUMF. Finally, we compare our measurements to new \emph{ab initio} shell-model calculations and comment on the state of the field in the $N=82$ region.
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Submitted 1 October, 2017; v1 submitted 12 May, 2017;
originally announced May 2017.