Abnormal signature inversion and multiple alignments in doubly odd 126I.

High-spin states in 126I have been investigated by using in-beam γ-ray spectroscopy with the 124Sn(7Li, 5n)126I reaction at a beam energy of 48 MeV. The level scheme of 126I has been extended and modified considerably by adding about 80 new γ rays and establishing five new bands. The configurations have been tentatively assigned for the yrast, yrare, and other excited bands with the help of triaxial projected shell-model (TPSM) and cranked shell-model calculations. The first band crossing in the yrast band is found due to alignments of a pair of (h11/2)² neutrons. The first and the second band crossings in the yrare band are caused by the alignments of a pair of (d5/2)² protons and a pair of (h11/2)² neutrons, respectively. Due to the successive excitations of two, four, and six quasiparticles, the alignments in the yrare band present a gigantic rising feature. The yrast band exhibits a signature inversion at low spins and becomes normal after a reversion spin of lrev = 14. The yrare band exhibits an abnormal signature inversion in which the signature inversion phase persists up to the highest spin. The signature inversions in 126I are well reproduced and successfully interpreted by the TPSM calculations. Some features of chirality are found for the four-quasiparticle (4qp) part of the yrast band and the 4qp excited band 2. [ABSTRACT FROM AUTHOR]