학술논문
$\beta^-$ decay of neutron-rich $^{45}$Cl at magic number N=28
Document Type
Working Paper
Author
Bhattacharya, Soumik; Tripathi, Vandana; Tabor, S. L.; Volya, A.; Bender, P. C.; Benetti, C.; Carpenter, M. P.; Carroll, J. J.; Chester, A.; Chiara, C. J.; Childers, K.; Clark, B. R.; Crider, B. P.; Harke, J. T.; Liddick, S. N.; Lubna, R. S.; Luitel, S.; Longfellow, B.; Mogannam, M. J.; Ogunbeku, T. H.; Perello, J.; Richard, A. L.; Rubino, E.; Saha, S.; Shehu, O. A.; Unz, R.; Xiao, Y.; Zhu, Yiyi
Source
Subject
Language
Abstract
Results from the study of $\beta^-$-decay of $^{45}$Cl, produced in the fragmentation of a 140-MeV/u $^{48}$Ca beam, are presented. The half-life for $^{45}$Cl $\beta$-decay is measured to be 513(36) ms. The $\beta^-$ and $\beta^- 1n$ decay of $^{45}$Cl populated excited states in $^{45,44}$Ar, respectively. On the basis of $\gamma$-ray singles and $\gamma$-$\gamma$ coincidence data, decay schemes for the two daughter nuclei have been established. They are compared with shell model calculations using the FSU interaction. The low-lying negative parity states for $^{45}$Ar are well described by a single particle (neutron) occupying orbitals near the Fermi surface, whereas neutron excitations across the $N = 20$ shell gap are needed to explain the positive-parity states which are expected to be populated in allowed Gamow-Teller $\beta$-decay of $^{45}$Cl. The highest $\beta$-feeding to the 5/2$^+$ state in $^{45}$Ar from the ground state of $^{45}$Cl points towards a 3/2$^+$ spin-parity assignment of the ground state of the parent over the other possibility of 1/2$^+$. The high Q$_{\beta^-}$ value of $^{45}$Cl decay allows for the population of $1p1h$ states above the neutron separation energy in $^{45}$Ar leading to positive parity states of $^{44}$Ar being populated by removal of one neutron from the $sd$ shell. The spin-parities of the excited levels in $^{44}$Ar are tentatively assigned for the first time by comparison with the shell model calculations. The 2978~keV level of $^{44}$Ar is identified as the excited 0$^+$ level which could correspond to a different configuration from the ground state.
Comment: 11 pages, 10 figures
Comment: 11 pages, 10 figures