Statistical orientation fluctuations in 188Os

Abstract

Abstract The role of the nuclear orientation in hot rotating nuclei is explored microscopically. We calculate statistical fluctuations in the orientation of the nucleus 188 Os relative to the spin vector by solving the finite-temperature HFB equation with three-dimensional cranking and the pairingplus-quadrupole interaction. The nuclear principal axis frame is defined self-consistently for each orientation by constraining the quadrupole mass tensor to be diagonal. We study the thermal and rotational dependence of the orientation probability distribution within the constant average spin constraint. Orientation fluctuations are also computed with the macroscopic Landau theory of hot rotating nuclei, and the results compare favorably with those of the microscopic HFB calculations. The equilibrium nuclear orientation is calculated as a function of temperature and spin to investigate the possibility of stable tilted rotation for this nucleus. For all rotational configurations considered, the nuclear free energy is found to be a minimum when the spin axis coincides with a principal axis of the quadrupole shape.