M. E. Wieser

Collision-Induced Dissociation at TRIUMF's Ion Trap for Atomic and Nuclear science

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. PlaÃŸ, M. P. Reiter, C. Scheidenberger, R. Thompson, J. L Tracy, C. Will, M. E. Wieser, M. Yavor, J. Dilling [1], A. A. Kwiatkowski

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 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.

Mass Measurements of Neutron-Rich Gallium Isotopes Refine Production of Nuclei of the First r-Process Abundance Peak in Neutron Star Merger Calculations

M. P. Reiter, S. Ayet San AndrÃ©s, S. Nikas [3,4], J. Lippuner [5,6,7], C. Andreoiu [8], C. Babcock [2], B. R. Barquest, J. Bollig [2,9], T. Brunner [2,10], T. Dickel [1,3], J. Dilling [2,11], I. Dillmann [2,12], E. Dunling [2,13], G. Gwinner [14], L. Graham [2], C. Hornung [1], R. Klawitter [2,15], B. Kootte [2,14,12], A. A. Kwiatkowski, Y. Lan [2,11], D. Lascar [2,16,17], K. G. Leach, E. Leistenschneider [2,11,3,4,12,9,1], G. MartÃnez-Pinedo, J. E. McKay, S. F. Paul, W. R. PlaÃŸ, L. Roberts [18], H. Schatz [7,18,19], C. Scheidenberger [1,3], A. Sieverding [3,4,20,2], R. SteinbrÃ¼gge, R. Thompson [21], M. E. Wieser, C. Will [1], D. Welch [18]

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 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 $Y_e=0.35-0.38$.

Dawning of the N=32 shell closure seen through precision mass measurements of neutron-rich titanium isotopes

E. Leistenschneider [1,2,3,4], M. P. Reiter, S. Ayet San AndrÃ©s, B. Kootte [1,5], J. D. Holt, P. NavrÃ¡til, C. Babcock [1], C. Barbieri [6,1], B. R. Barquest, J. Bergmann [3], J. Bollig [1,7], T. Brunner [1,8], E. Dunling [1,9], A. Finlay [1,2], H. Geissel [3,4], L. Graham [1], F. Greiner [3], H. Hergert [10], C. Hornung [3], C. Jesch [3], R. Klawitter [1,11], Y. Lan [1,2], D. Lascar [1,12], K. G. Leach, W. Lippert [3,1,13,7], J. E. McKay, S. F. Paul, A. Schwenk [11,14,15], D. Short [1,16], J. Simonis [17,18,1,19], V. SomÃ, R. SteinbrÃ¼gge, S. R. Stroberg, R. Thompson [20], M. E. Wieser, C. Will [3], M. Yavor [21], C. Andreoiu [16], T. Dickel [3,4], I. Dillmann [1,13], G. Gwinner [5,3,4], W. R. PlaÃŸ, C. Scheidenberger [3,4,1,13], A. A. Kwiatkowski, J. Dilling [1,2]

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 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.