Lifetime measurements in $^{63}$Co and $^{65}$Co

TL;DR

This study measured the lifetimes of specific nuclear states in cobalt isotopes using advanced gamma-ray detection and transfer reactions, providing data that helps distinguish between single-particle and collective nuclear behaviors.

Contribution

It provides new lifetime measurements for $^{63}$Co and $^{65}$Co states and compares them with shell-model calculations to analyze nuclear structure.

Findings

Lifetimes of key states were successfully measured.

E2 transition probabilities were extracted or bounded.

Results support insights into the single-particle versus collective nature of states.

Abstract

Lifetimes of the $9/2^-_1$ and $3/2^-_1$ states in $^{63}$Co and the $9/2^-_1$ state in $^{65}$Co were measured using the recoil distance Doppler shift and the differential decay curve methods. The nuclei were populated by multi-nucleon transfer reactions in inverse kinematics. Gamma rays were measured with the EXOGAM Ge array and the recoiling fragments were fully identified using the large-acceptance VAMOS spectrometer. The E2 transition probabilities from the $3/2^-_1$ and $9/2^-_1$ states to the $7/2^-$ ground state could be extracted in $^{63}$Co as well as an upper limit for the $9/2^-_1\rightarrow7/2^-_1$ $B$(E2) value in $^{65}$Co. The experimental results were compared to large-scale shell-model calculations in the $pf$ and $pfg_{9/2}$ model spaces, allowing to draw conclusions on the single-particle or collective nature of the various states.