Evidence for Predicted Level Crossings in $\tilde{\pi }{h}_{\frac{9}{2}}\otimes \tilde{\nu }{i}_{\frac{13}{2}}$ Bands in Very Neutron-Deficient, Doubly Odd T1 Isotopes

Isomeric transitions, of $E3\mathrm{}$, $M2\mathrm{}$, and $\frac{E1\mathrm{}}{M2\mathrm{}}$ character, depopulating $\tilde{\pi }{h}_{\frac{9}{2}}\otimes \tilde{\nu }{i}_{\frac{13}{2}}$ bands in ${}_{}{}^{186,188,190}{}_{}{}^{}\mathrm{T}1\mathrm{}$, respectively, have been found with use of $\gamma$-ray spectroscopic techniques. The changes in multipolarity reflect successive changes in the bandhead spin values corresponding to level crossings within the $\tilde{\pi }{h}_{\frac{9}{2}}\otimes \tilde{\nu }{i}_{\frac{13}{2}}$ system. These crossings were predicted in the framework of the two-quasiparticle plus rotor model and interpreted as a direct consequence of the depletion of the $i_{\frac{13}{2}}$ shell.