Systematics on the low-lying spectra in N = 78 ~ 80 isotones

Abstract

Combining the new spectroscopy results of 144 Tb and previous spectroscopy studies of neighboring nuclei, a systematic investigation on the low-lying spectra in N = 78 ~ 80 isotones is performed. Good systematics have been found for the coupling patterns which couple the odd nucleon(s), such as πh11/2, [Formula: see text], to the 2+, 4+, 6+ and 3- core excitations. It is found that the relative excitation energies of the states formed by coupling h11/2 proton(s) to the 2+, 4+ core excitations are pushed up, in contrast with those formed by coupling h11/2 neutron hole(s) to the 2+, 4+ core excitations, which are pulled down. According to the systematics, the interpretation that the 17/2+ states observed in 141 Sm and 143 Gd are the fully aligned member of coupling the odd h11/2 neutron hole to the octupole 3- core excitation, is explored to the isotones 145 Dy , 142 Eu , and 144 Tb .