Shell-model description of neutron-rich pf-shell nuclei with a new effective interaction GXPF 1

Abstract

Abstract. The shell-model effective interaction GXPF1 is tested for the description of unstable pf -shell nuclei. The GXPF1 successfully describes the N = 32 shell gap in Ca, Ti and Cr isotopes, while the deviation of predicted Ex(2Ti from the recent experimental data requires the modification of the Hamiltonian especially in the T = 1 matrix elements related to the p 1/2 and f 5/2 orbits. The modified interaction gives improved description simultaneously for all these isotope chains. PACS

Valence nucleon populations in the Ni isotopes

“…Two interactions were used in the calculations that were fit to different data sets in this region. The GXPF1A [30] interaction is a slightly modified form of the GXPF1 [31] interaction based on nuclei in the mass range 47 and 66, and does not include the 0g 9/2 in the model space. The second interaction JUN45 [32] was obtained by fitting data in the mass range between 63 and 96, with a somewhat different model space that included the g 9/2 state but not the f 7/2 .…”

Multiparticle-multihole states aroundO16and correlation-energy effect on the shell gap

“…We now examine the cross-shell correlation energies around 56 Ni as an example of the j -j closure. They are calculated in the pf shell with the GXPF1A interaction [10]. To avoid a diagonalization of a huge shell-model Hamiltonian, the model space is truncated at the truncation level t = 6, where t denotes the maximum number of excitation across the N = Z = 28 gap.…”

Study of nuclei aroundZ= 28 by large-scale shell model calculations

“…Two-body matrix elements (TBMEs) of the interaction consist of three parts. TBMEs in the p f shell are those of the GXPF1A interaction [5] and TBMEs in the f 5 pg 9 space related to the 0g 9/2 orbit are those of the JUN45 interaction [6]. The GXPF1A and JUN45 interactions were determined by combining microscopically derived interactions with a minor empirical fit.…”

“…The exotic nucleus has different shell structure from that of ordinary nucleus and can show different magic numbers. We use a p f g 9 d 5 model space, which consists of the 0 f 1p shell, 0g 9/2 and 1d 5/2 orbits, in order to treat magic numbers 28, 50 and a submagic number 40. Conventional shell-model calculations are difficult in this large model space and we use the Monte Carlo shell model (MCSM) [1].…”