NUCLEAR-STRUCTURE OF SB-109

This is the first report on nuclear structure of 109Sb. Excited states up to I(pi) = 27/2+ and 35/2- have been established using the reaction (Fe(Ni,3p)Sb)-Fe-54-Ni-58-Sb-109 and in-beam techniques. According to the particle(hole)-core coupling scheme these excited states were classified into five bands: three are based on the pid5/2, pig7/2, and pih11/2 states; the other two are the DELTAI = 1 collective bands built on the 17/2+ state at 2651 keV and the 23/2- state at 4487 keV. The 11/2+ --> 9/2+ transition in the pig7/2 band possesses an E2/M1 mixing ratio delta > 0, which suggests admixing of the pig9/2 hole state. Positive mixing ratios observed in the collective bands indicate a prolate deformation due to the (pig9/2)-1 core excitation. In the pih11/2 band, B(M1; 23/2- --> 21/2-) was measured to be 0.040(3) W.u. Furthermore the 27/2- --> 25/2- transition was too weak for a proton M1 transition. These transitions are retarded by the nuh11/2 configurations mixed in the involved states.