Analog Resonances ofTl206andTl

Abstract

The levels of 206 T1 and 204 T1 are studied by observing their analog resonances in the reactions 205 -203 Tl(/>, p 0 ) and 205, 203X1 (p } p f ). The lowest-lying states formed by a proton hole (3si/ 2 ) coupled to a neutron hole (3pm, 2/5/2, or 3^3/2) are observed to resonate weakly as in the case of the neutron-hole states formed in the 206 Pb(/>, po) analog resonances. Above 2.5-MeV excitation energy in the parent nucleus, states containing neutron particles coupled to the target ground-state core are observed to resonate strongly. The energy spreads of the dominant configurations [ m (3su2~1)p(nlj) n ']jr are deduced by comparing the total widths measured in the inelastic channels to the total widths measured in the decay of the (nlj) n configuration formed in the 208 Pb(/>, p') reaction. The g 9 / 2 neutron strength remains highly localized in both 206 T1 and 204 T1, which have total widths (r) of 219 and 217 keV, respectively, compared with the 209 Pb width of 253 keV. In the energy region of the 2gm-3d m neutron stength, T =427 and 996 keV for 206 T1 and 204 T1, respectively, compared to r = 300 keV for 209 Pb. The strengths of these configurations are thus spread over an energy range >150 keV in 206 T1, >700 keV in 204 T1, whereas the two states are split by 50 keV in 209 Pb.