2025/04/17 by Kimura, S., Wada, M., Fu, C. Y. +27
Physics and Astronomy · #Astro and Planetary Science #Astrophysical Phenomena and Observations #FOS: Physical sciences #Gamma-ray bursts and supernovae #High Energy Astrophysical Phenomena (astro-ph.HE) #Nuclear Experiment (nucl-ex) #Nuclear Theory (nucl-th)
paper · pdf · doi:10.48550/arxiv.2504.12639
openalex publication_date 2025/04/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The rapid proton-capture (rp-) process is one of the primary, explosive thermonuclear burning processes that drive type I X-ray bursts. A possible termination of the rp-process at around 84Mo was previously suggested by the formation of a ZrNb cycle. We report here precision mass measurements at around 84Mo, which have concluded the possibility of the cycle. The experiment was conducted using the multi-reflection time-of-flight spectrograph at RIKEN RI Beam Factory, and the masses of 79Y, 83Nb, 84Mo, 88Ru, and an isomer in 78Y were measured. For 84Mo, and 88Ru, and the isomeric state of 78Y, their masses are experimentally determined for the first time with uncertainties of δm ≈ 20~\rm keV/c2. The mass precision of 79Y and 83Nb is improved to 13~\rm keV/c2 and 9.6~\rm keV/c2, respectively. The new α-separation energy of 84Mo, 1.434(83) MeV, unambiguously rules out the possibility of forming the ZrNb cycle. The X-ray burst simulation with the new masses shows that our measurements effectively remove the large final abundance uncertainties in the A=80-90 mass region. The new mass values improve the prediction power for the composition of the nuclear ashes in X-ray bursts.