Sprecher
Beschreibung
Nuclear masses of neutron-deficient N$\sim$Z nuclei are pivotal for modeling astrophysical processes, such as the rapid proton-capture (rp) and $\nu$p processes, which drive nucleosynthesis in X-ray bursts and proton-rich supernova ejecta. These masses determine proton separation energies, reaction Q-values, and waiting points, directly influencing reaction flows, light curves, and p-nuclei abundances. This talk presents recent advances in high-precision mass measurements at the Ion Guide Isotope Separator On-Line (IGISOL) facility in Finland and the Rare-RI Ring at RIKEN, Japan, focusing on their technical innovations and astrophysical impacts. At IGISOL, the JYFLTRAP double Penning trap, coupled with an inductively heated hot-cavity catcher laser ion source, has enabled mass measurements of exotic nuclides, like $^{95-97}$Ag, with $\sim$1 keV/c$^2$ precision, using time-of-flight ion-cyclotron resonance (TOF-ICR) and phase-imaging ion-cyclotron resonance (PI-ICR) techniques to achieve a relative precision of 10$^{-8}$. These measurements, particularly of $^{95}$Ag and the $^{96}$Ag isomers, have refined reaction rates for the rp-process, impacting X-ray burst modeling, and confirmed the robustness of the N=50 shell closure. Additionally, the Multi-Reflection Time-of-Flight Mass Spectrometer (MR-TOF-MS) at IGISOL has targeted the A$\sim$84 region, addressing the Zr-Nb cycle’s role in limiting rp-process flows (although some masses in this region have been measured at RIKEN with MR-TOF-MS). At RIKEN, the Rare-RI Ring employs isochronous mass spectrometry (IMS) and B$\rho$-TOF methods to access heavy N$\sim$Z nuclei (A=70–100), achieving a relative precision of 10$^{-6}$–10$^{-7}$ for exotic nuclei with half-lives of 100 ns to 1 ms. Approved experiments using a $^{124}$Xe beam aim to measure masses near $^{100}$Sn, critical for rp- and $\nu$p-process termination cycles, like Sn-Sb-Te. Technical advances, including isochronous optics and high-efficiency ion extraction, enhance measurement precision to $\sim$10–100 keV. These results will provide critical inputs for modeling waiting points and p-nuclei production in the future.
The talk will highlight achievements, such as resolving the $^{96}$Ag astromer and incorporating measured masses of $^{95-96}$Ag to refine reaction rates, technical advances in all modern mass measurement techniques (existing and proposed, using Penning Trap, MR-TOF MS, IMS and B$\rho$-TOF methods with storage ring and beam line) for the A$\sim$70–100 region, and outline future plans to measure N$\sim$Z nuclei, resolving nuclear structure puzzles and refining astrophysical models. Collaborative efforts with facilities, like the FRS/SuperFRS Ion Catcher at GSI/FAIR, will further extend the reach of these techniques, paving the way for the next 25 years of nuclear mass spectrometry in astrophysics.
