Mass measurements of neutron-rich gallium isotopes refine production of nuclei of the first <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mi>r</mml:mi></mml:math>-process abundance peak in neutron-star merger calculations
M. P. Reiter, S. Ayet San Andrés, S. Nikas, Jonas Lippuner, C. Andreoiu, C. Babcock, B. R. Barquest, J. Bollig, T. Brunner, T. Dickel, J. Dilling, I. Dillmann, E. Dunling, G. Gwinner, Lorraine Graham, C. Hornung, R. Klawitter, B. Kootte, A. A. Kwiatkowski, Y. Lan, D. Lascar, K. G. Leach, E. Leistenschneider, G. Martı́nez-Pinedo, J. E. McKay, S. F. Paul, W. R. Plaß, Luke F. Roberts, H. Schatz, C. Scheidenberger, André Sieverding, René Steinbrügge, R. I. Thompson, Michael E. Wieser, C. Will, D. Welch
Abstract
We report mass measurements of neutron-rich Ga isotopes $^{80\ensuremath{-}85}\mathrm{Ga}$ with TRIUMF's Ion Trap for Atomic and Nuclear science. The measurements determine the masses of $^{80\ensuremath{-}83}\mathrm{Ga}$ in good agreement with previous measurements. The masses of $^{84}\mathrm{Ga}$ and $^{85}\mathrm{Ga}$ were measured for the first time. Uncertainties between 25 and 48 keV were reached. The new mass values reduce the nuclear uncertainties associated with the production of $A\ensuremath{\approx}84$ isotopes by the $r$-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 ${Y}_{e}=0.35\ensuremath{-}0.38$.