Quasicontinuum M1 \(\gamma \) strength as function of nuclear deformation

Abstract

In this investigation, we examine the mean transition probabilities of low-energy \(\gamma \)-rays within the quasicontinuum excitation region. Particular emphasis is placed on the low-energy enhancement (LEE) and scissors mode (SM) structures, which are observed in the \(\gamma \)-ray strength function (\(\gamma \)SF). The stable isotopic chain of neodymium includes nuclei that range from nearly spherical to well-deformed shapes. Consequently, analyzing the LEE and SM structures in relation to deformation may elucidate the characteristics of these phenomena. It has been observed that the integrated measured \(\gamma \)-ray strength of the LEE reaches a maximum of \(B(M1) \approx 21 \mu _N^2\) at a deformation of \(\beta _2 \approx 0.16\), while the SM attains a maximum of \(B(M1) \approx 8 \mu _N^2\) at \(\beta _2 \approx 0.3\). Furthermore, the two phenomena display different average \(\gamma \) energies. These experimental findings suggest that the origins of the two structures arise from distinct mechanisms.