Abstract
The work reports several new excited states in the neutron-rich 147La nucleus, populated in spontaneous fission of 252Cf. The excitation scheme has been reinvestigated by means of γ-ray spectroscopy, using high-fold γ coincidences measured with the Gammasphere array of Ge detectors. It is shown that the 229.65-keV level has spin and parity 11/2-, which changes the 9/2- spin-parity reported in a recent evaluation and sets up the spinparity of the ground state as 5/2+. New levels allow to arrange the excitation scheme of 147La into a parity-doublet-like structure showing that the 147La nucleus may have an octupole deformation.
Highlights
The region of neutron-rich nuclei with masses A≈150 is a place where octupole correlations can be studied in detail
The present status based on studies of of 144Ba [4, 5] is that there is an octupole deformation in Ba isotopes
In the N=90 isotone 147La, excited states could be arranged into a parity-doublet structure, though only at higher excitation energy [11, 12]. In both works spin and parity 11/2− were assigned to the 229.65-keV level, it was a surprise that the recent compilation [13] has reported 9/2− spinparity for this level. Such an assignment does not agree with the proposed parity doublet structure in 147La
Summary
The region of neutron-rich nuclei with masses A≈150 is a place where octupole correlations can be studied in detail. Such an assignment does not agree with the proposed parity doublet structure in 147La. recent works report the presence of 11/2− bands in other N=90 isotones, 145Cs [14] and 149Pr [15].
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