Microscopic non-axial study of even-even ^226-230Th isotopes using octupole interaction

The yrast spectra, quadrupole moments, octupole moments, quadrupole deformation parameters (2), non-axiality parameters (γ), root mean square radii for protons and neutrons, occupation probabilities, and B(E2) transition probabilities are calculated for ^226-230Th in Cranked Hartree-Bogoliubov (CHB) framework. These calculations have been performed by employing one body octupole potential field added to a quadrupole-quadrupole plus pairing model of residual interaction operating in a reasonably large valence space outside the ¹⁶⁴Pb core. Our calculations reproduce qualitatively the observed yrast spectra in ²²⁶Th to ²³⁰Th up to spin 20⁺. The calculated results indicate that the quadrupole deformation increases and non-axiality of all these nuclei decreases along the yrast states. The results of octupole moments indicate that the octupole collectivity decreases as one moves from ²²⁶Th to ²³⁰Th. The observed increase in deformation in going from ²²⁶Th to ²³⁰Th is due to the increase in the occupation of low k components of (2g_9/2) and (1j_15/2)u orbits. (author)