Intruder structures in $^{32}$Si and $^{29}$Al

TL;DR

This study investigates high-spin structures in $^{32}$Si and $^{29}$Al using fusion-evaporation reactions, revealing new intruder states and comparing them with shell model predictions.

Contribution

The paper reports the first observation of high-spin intruder structures in $^{32}$Si and $^{29}$Al, with detailed lifetime measurements and shell model comparisons.

Findings

Identification of high-spin states feeding a $5^-$ isomer in $^{32}$Si.

Discovery of a rotor-like negative-parity band in $^{29}$Al.

Agreement between experimental data and shell model calculations.

Abstract

We have studied $^{32}$Si and $^{29}$Al using $^{12}$C($^{22}$Ne,2p) and $^{12}$C($^{22}$Ne,$\alpha$p) fusion-evaporation reactions. In both cases, we observed significant population of high-spin structures distinct from the ground-state yrast bands. In $^{32}$Si, most of the high-energy states feed into a $J^{\pi} = 5^-$ nanosecond isomer. In $^{29}$Al, we identified a rotor-like negative-parity band with a $J^{\pi} = 7/2^-$ band-head. Doppler shift lifetime measurements were performed for all observed states. These results were compared to shell model calculations and interpreted in terms of proton and neutron cross-shell excitation.