Abstract
Levels in the
75Kr nucleus were populated in the inverse
24Mg(
54Fe, 2pn)
75Kr reaction at beam energies of 177 and 190 MeV. In the reaction study at 177 MeV, the γ-rays were detected in coincidence with neutrons and mass-75 nuclei and in the reaction at 190 MeV only γγ-coincidence data were collected. Using the γγ-neutron gated γγ- and
Recoil-γγ-coincidence techniques, we were able to develop the level scheme up to spins (
37+
2
) and (
31−
2
) in the positive- and negative-parity bands, respectively. These spins are high enough to allow us to study alignment effects in this mass region. The signature splitting at low spin can be reproduced in a cranked shell model calculation assuming a quadrupole deformation
β
2 = 0.37 and a slightly triaxial (
γ≈ −10°) shape for positive-parity states but an axial shape for the negative-parity sequence. The spin alignment as a function of rotational frequency has been studied; in the positive-parity band alignment is observed at a rotational frequency of
h
̵
ω ≈ 0.63
MeV
and in the negative-parity band the alignment occurs at
h
̵
ω ≈ 0.57
MeV
. The observed alignment in both bands is associated with a pair of
g
9
2
protons, and the difference in the alignment frequencies is thought to be due to differing intrinsic shapes.