Low-lying electric and magnetic dipole strengths in Pb207

Abstract

Low-lying dipole transitions in $^{207}\mathrm{Pb}$ were measured via nuclear photon scattering using a quasimonochromatic, linearly polarized photon beam. The spins and/or parities of the states observed in $^{207}\mathrm{Pb}$ were determined from the intensity asymmetry of resonantly scattered $\ensuremath{\gamma}$ rays with respect to the polarization plane of the incident photon beam. The electric ($E1$) and magnetic ($M1$) dipole strengths were obtained for excitation energies from 5.49 to 6.75 MeV. The present experimental results, combined with $(\ensuremath{\gamma},n)$ data from the literature, were used to investigate the $E1$ and $M1$ photoabsorption cross sections near the neutron separation energy by comparison with predictions from the particle-vibration coupling with the quasiparticle random-phase approximation model.