Shell model results for $T=1$ and $T=0$ bands in $^{66}$As

TL;DR

This paper presents comprehensive shell model analyses of $^{66}$As, comparing theoretical predictions with experimental data for multiple bands, revealing structural changes and identifying isomeric states using advanced interactions.

Contribution

It provides new shell model calculations for $^{66}$As using the jj44b interaction, including structural insights and comparisons with experimental data and other interactions.

Findings

Reasonable agreement between shell model results and experimental data for low-lying bands.

Prediction of structural change at $8^+$ in the $T=1$ band.

Identification of isomeric states and parity of observed levels.

Abstract

Results of a comprehensive shell model (SM) analyses, within the full $f_{5/2}pg_{9/2}$ model space, of the recently available experimental data [P. Ruotsalainen et al., Phy. Rec. C {88}, 024320 (2013)] with four $T=0$ bands and one $T=1$ band in the odd-odd $N=Z$ nucleus $^{66}$As are presented. The calculations are performed using jj44b effective interaction developed recently by B.A. Brown and A.F. Lisetskiy for this model space. For the lowest two $T=0$ bands and the $T=1$ band, the results are in reasonable agreement with experimental data and deformed shell model is used to identify their intrinsic structure. For the $T=1$ band, structural change at $8^+$ is predicted. For the third $9^+$ band with $T=0$, the shell model $B(E2)$ values and quadrupole moments (in addition to energies) are consistent with the interpretation in terms of aligned isoscalar $np$ pair in $g_{9/2}$ orbit coupled to the $^{64}$Ge ground band. Similarly, the $9^+$ level of band 4 and a close lying $5^+$ level are found to be isomeric states in the analysis. Finally, energies of the band 5 members calculated using shell model with both positive and negative parity show that the observed levels are most likely negative parity levels. The SM results with jj44b are also compared with the results obtained using JUN45 interaction.