The Levels of²³⁰Th Obtained in the Decay of²³⁰Pa

Abstract

The decay of 230Pa to the levels of 230Th has been investigated using semi-conductor detectors for gamma and electron singles-spectra measurements and Ge(Li) detectors combined with a NaI(Tl) detector for gamma-gamma coincidence measurements. Some weak gamma transitions not reported earlier were observed. A decay scheme is presented which counts all of the transitions observed in the present work. The following bands are established in 230Th: The ground state band (2+, 4+, 53.2 keV, 174 keV), the beta quadrupole band (0+, 2+, 635.1 keV, 677.3 keV), the gamma quadrupole band (2+, 3+, 781.4 keV, 825.8 keV), the Kπ = 0- octupole band (1-, 3-, 508.1 keV, 571.8 keV), the Kπ = 1- octupole band (1-, 2-, 3-, 951.7 keV, 971.6 keV, 1 012.5 keV) and the Kπ = 2- octupole band (2-, 3-, 1 079.3 keV, 1 127.4 keV). The 2+ state at 1 009.5 keV is thought to be a two-phonon state. The experimental data are discussed in terms of nuclear models and compared with those of other authors. The beta feeding to the states in 230Th has been discussed from the point of view of the two quasi-particle composition of the vibrational states.