Study of the Energy Levels ofTl203Using (γ,γ′) Reaction

Abstract

Elastic and inelastic nuclear resonant scattering of monochromatic photons from $^{203}\mathrm{Tl}$ has been studied using a 20-cc Ge(Li) detector. The $\ensuremath{\gamma}$ source was obtained from thermal-neutron capture in titanium. The scattering isotope was identified by using an isotopically enriched thallium target. The energy of the resonance level in $^{203}\mathrm{Tl}$ was found to be 6.418 MeV. Assuming the high-energy lines to be primary transitions deexciting the resonance level, some 14 energy levels were found from the ground state up to 2.9 MeV, 4 of which may be identified with recently reported levels.By measuring the angular distribution of the scattered radiation, the spin of the 6.418-MeV level was determined to be \textonehalf{}, and thus, based on the assumption of dipole transitions, the spins of several low-lying levels were found to be either \textonehalf{} or $\frac{3}{2}$. The total radiative width of the resonance level was determined and found to be ${\ensuremath{\Gamma}}_{\ensuremath{\gamma}}=0.32\ifmmode\pm\else\textpm\fi{}0.06$ eV and $\frac{{\ensuremath{\Gamma}}_{0}}{{\ensuremath{\Gamma}}_{\ensuremath{\gamma}}}=0.026$. The spectral shape of scattered radiation was found to have a strong intensity bump at about 5 MeV; this is discussed in the light of similar bumps obtained in ($n,\ensuremath{\gamma}$) and ($d,p\ensuremath{\gamma}$) reactions on nuclei in the same mass region.