Y. D. Zang

Mass Measurement of 45Cr and Its Impact on the Ca-Sc Cycle in X-Ray Bursts

Masses of neutron-deficient 58Ni projectile fragments have been measured at the HIRFL-CSR facility in Lanzhou, China employing the isochronous mass spectrometry technique. Masses of a series of short-lived Tz = –3/2 nuclides including the 45Cr nucleus have been measured with a relative uncertainty of about 10–6-10–7. The new 45Cr mass turned out to be essential for modeling the astrophysical rp-process. In particular, we find that the formation of the predicted Ca-Sc cycle in X-ray bursts can be excluded.

A resonant Schottky pickup for the study of highly charged ions in storage rings

A resonant Schottky pickup was built into the experimental storage ring at GSI Darmstadt in 2010 and a similar one in the CSRe storage ring at IMP Lanzhou in 2011. Single-ion sensitivity was achieved at 400 MeV u−1. The pickup has also been used in many storage ring experiments ever since. A brief description of the pickup and its application in single-ion lifetime spectroscopy is provided in this work.

Test of IMME in fp shell via direct mass measurements of TZ = -3/2 nuclides

Isochronous mass spectrometry has been applied to neutron-deficient Ni-58 projectile fragments at the HIRFL-CSR facility in Lanzhou, China. Masses of four short-lived T-z = -3/2 nuclides Ti-41, Cr-45, Fe-49, and Ni-53 have been measured with a precision of 20 - 40 keV. The new mass data enabled for the first time to test the isobaric multiplet mass equation (IMME) in fp-shell nuclei. We observed that the IMME is inconsistent with the generally accepted quadratic form for the A = 53, T = 3/2 quartet. We performed full space shell model calculations and compared them with the new experimental results. The main results were published in Y.H. Zhang et al., Physical Review Letters 109 (2012). Here we give details on the experiment and data analysis as well as summarize the main findings.

Mass Measurements of Proton‐rich Nuclides at the Cooler Storage Ring at IMP

Recent results and progress of mass measurements of proton‐rich nuclei using isochronous mass spectrometry (IMS) are reported. The nuclei under investigation were produced via fragmentation of relativistic energy heavy ions of 78Kr and 58Ni. After in‐flight separation by the fragment separator RIBLL‐2, the nuclei were injected and stored in the experimental storage ring CSRe, and their masses were determined from measurements of the revolution times. The impact of these measurements on the stellar nucleosynthesis in the rp‐process is discussed.

Direct Mass Measurements of Short-Lived A=2Z-1 Nuclides {sup 63}Ge, {sup 65}As, {sup 67}Se, and {sup 71}Kr and Their Impact on Nucleosynthesis in the rp Process

Mass excesses of short-lived A=2Z-1 nuclei (63)Ge, (65)As, (67)Se, and (71)Kr have been directly measured to be -46,921(37), -46,937(85), -46,580(67), and -46,320(141)  keV, respectively. The deduced proton separation energy of -90(85)  keV for (65)As shows that this nucleus is only slightly proton unbound. X-ray burst model calculations with the new mass excess of (65)As suggest that the majority of the reaction flow passes through (64)Ge via proton capture, indicating that (64)Ge is not a significant rp-process waiting point.