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

High spin states of the odd proton-nucleus ^169Ta have been populated in the reaction ^155Gd(^19F,5n) with beam energies of 97MeV,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.