Electric dipole and quadrupole ground state transitions inBa138fromBa138(γ,γ) andBa138(γ,γ′)

Twelve ground state transitions up to about 5 MeV have been observed by the resonant scattering of bremsstrahlung from natural barium. Six of the first seven lines are from $2^{+}$ states in ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ba}$ as evidenced by the angular distribution measurements and the correspondence of the energies with known levels in ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ba}$. Presumably these arise from proton configurations. Of the remaining five lines four have distributions expected for spin 1 levels. The linear polarization of the scattered radiation for the first of these, at 4027 keV, suggests a negative parity. It is likely that this state is derived from the superposition of the one phonon quadrupole and octupole transitions in ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ba}$. Comparison with the results of other studies indicates that the other three lines are from neutron particle-hole states in ${}_{}{}^{138}{}_{}{}^{}\mathrm{Ba}$. Widths in terms of the ground state branching ratios and the partial widths for decays to the ground state are given for the identified levels.