Structure of the Semi-decoupled π 1/2[411] Band in Odd Proton Nucleus 169 Ta

High spin states of the odd proton-nucleus 169Ta have been populated in the reaction 155Gd(19F,5n) with beam energies of 97 MeV. Rotational band based on d3/2 proton 1/2[411] Nilsson state has been pushed up to 39/2+ in the α = 1/2 decay sequence. Its signature partner, the α = -1/2 decay sequence with four link transitions has been established and 1/2[411] band in 169Ta was reassigned to be a semi-decoupled band. The systematics of the signature splitting in the K = 1/2 bands in the rear-earth region and the accidental degeneracy conclusion given by the angular projection shell model were discussed.