Nuclear level densities and γ-ray strength functions inSc44,45

Abstract

The scandium isotopes $^{44,45}\mathrm{Sc}$ were studied with the $^{45}\mathrm{Sc}$($^{3}\mathrm{He}$, $\ensuremath{\alpha}\ensuremath{\gamma}$)$^{44}\mathrm{Sc}$ and $^{45}\mathrm{Sc}$($^{3}\mathrm{He}$, $^{3}\mathrm{He}$${}^{'}\ensuremath{\gamma}$)$^{45}\mathrm{Sc}$ reactions, respectively. The nuclear level densities and \ensuremath{\gamma}-ray strength functions have been extracted using the Oslo method. The experimental level densities are compared to calculated level densities obtained from a microscopic model based on BCS quasiparticles within the Nilsson level scheme. This model also gives information about the parity distribution and the number of broken Cooper pairs as a function of excitation energy. The experimental \ensuremath{\gamma}-ray strength functions are compared to theoretical models of the $E1$, $M1$, and $E2$ strength and to data from (\ensuremath{\gamma}, $n$) and (\ensuremath{\gamma},$p$) experiments. The strength functions show an enhancement at low \ensuremath{\gamma} energies that cannot be explained by the present standard models.