Direct Mass Measurements to Inform the Behavior of 128m$\mathrm{Sb}$ in Nucleosynthetic Environments

• Published in: Physical review letters Vol. 131; no. 26
• Main Authors: Hoff, D. E. M., Kolos, K., Misch, G. W., Ray, D., Liu, B., Valverde, A. A., Brodeur, M., Burdette, D. P., Callahan, N., Clark, J. A., Gallant, A. T., Kondev, F. G., Morgan, G. E., Mumpower, M. R., Orford, R., Porter, W. S., Rivero, F., Savard, G., Scielzo, N. D., Sharma, K. S., Sieja, K., Sprouse, T. M., Varriano, L.
• Format: Journal Article
• Language: English
• Published: United States American Physical Society (APS) 27-12-2023
• Subjects: nuclear astrophysics; NUCLEAR PHYSICS AND RADIATION PHYSICS; r process; radioactive beams; shell model
• ISSN: 0031-9007

Nuclear isomer effects are pivotal in understanding nuclear astrophysics, particularly in the rapid neutron-capture process where the population of metastable isomers can alter the radioactive decay paths of nuclei produced during astrophysical events. The β-decaying isomer 128mSb was identified as potentially impactful since the β-decay pathway along the A = 128 isobar funnels into this state bypassing the ground state. Here we report the first direct mass measurements of the 128Sb isomer and ground state using the Canadian Penning Trap mass spectrometer at Argonne National Laboratory. We find mass excesses of -84564.8(25) keV and -84608.8(21) keV, respectively, resulting in an excitation energy for the isomer of 43.9(33) keV. These results provide the first key nuclear data input for understanding the role of 128mSb in nucleosynthesis, and we show that it will influence the flow of the rapid neutron-capture process.