Fast nuclear rotation and octupole deformation

TL;DR

This study investigates high-spin states in 150Sm, revealing the disappearance of octupole deformation above spin I=22, consistent with theoretical predictions, through gamma-ray measurements following a nuclear reaction.

Contribution

First high-spin measurement of 150Sm showing the abrupt end of octupole deformation at I=22, providing experimental evidence for shape evolution in this nucleus.

Findings

Observation of alternating parity band up to I=22

Identification of band crossings with aligned states

Evidence suggesting vanishing octupole shape above I=22

Abstract

The 150Sm nucleus has been studied to high spins in a measurement of gamma radiation following the 136Xe(18O,4n)150Sm, compound-nucleus reaction at beam energy of 76 MeV. The measurement was performed at NBI Riso using the NORDBALL array. Alternating parity, s=+1 band in 150Sm has been observed up to spin I=22. This band is crossed by two aligned bands, corresponding to a reflection-symmetric shape. After the second crossing the s=+1 band ends abruptly, suggesting that the octupole shape vanishes in 150Sm above spin I=22, as predicted by calculations. Other explanations, assuming continuation of the s=+1 band past the two alignments are also discussed.