The levels of ${}_{}{}^{206}{}_{}{}^{}\mathrm{Tl}$ and ${}_{}{}^{204}{}_{}{}^{}\mathrm{Tl}$ are studied by observing their analog resonances in the reactions ${}_{}{}^{205,203}{}_{}{}^{}\mathrm{Tl}(p,p_0)$ and ${}_{}{}^{205,203}{}_{}{}^{}\mathrm{Tl}(p,p^{\prime })$. The lowest-lying states formed by a proton hole ($3s_{\frac{1}{2}}$) coupled to a neutron hole ($3p_{\frac{1}{2}}$, $2f_{\frac{5}{2}}$, or $3p_{\frac{3}{2}}$) are observed to resonate weakly as in the case of the neutron-hole states formed in the ${}_{}{}^{206}{}_{}{}^{}\mathrm{Pb}(p,p_0)$ 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 ${\left[{\left(3\mathrm{}s_{\frac{1}{2}}^{}{}_{}{}^{-1\mathrm{}}\right)}_p{\left(n{l}_j\right)}_n\right]}_{J\pi }$ are deduced by comparing the total widths measured in the inelastic channels to the total widths measured in the decay of the ${\left(n{l}_j\right)}_n$ configuration formed in the ${}_{}{}^{208}{}_{}{}^{}\mathrm{Pb}(p,p^{\prime })$ reaction. The $g_{\frac{9}{2}}$ neutron strength remains highly localized in both ${}_{}{}^{206}{}_{}{}^{}\mathrm{Tl}$ and ${}_{}{}^{204}{}_{}{}^{}\mathrm{Tl}$, which have total widths ($\Gamma$) of 219 and 217 keV, respectively, compared with the ${}_{}{}^{209}{}_{}{}^{}\mathrm{Pb}$ width of 253 keV. In the energy region of the $2g_{\frac{7}{2}}-3d_{\frac{3}{2}}$ neutron stength, $\Gamma =427\mathrm{} \mathrm{and} 996$ keV for ${}_{}{}^{206}{}_{}{}^{}\mathrm{Tl}$ and ${}_{}{}^{204}{}_{}{}^{}\mathrm{Tl}$, respectively, compared to $\Gamma =300\mathrm{}$ keV for ${}_{}{}^{209}{}_{}{}^{}\mathrm{Pb}$. The strengths of these configurations are thus spread over an energy range ≥150 keV in ${}_{}{}^{206}{}_{}{}^{}\mathrm{Tl}$, ≥700 keV in ${}_{}{}^{204}{}_{}{}^{}\mathrm{Tl}$, whereas the two states are split by 50 keV in ${}_{}{}^{209}{}_{}{}^{}\mathrm{Pb}$.

• Received 14 July 1969

DOI:https://doi.org/10.1103/PhysRev.188.1934