First identification of dipole excitations to a2+⊗3−⊗particle multiplet in an odd-Anucleus

A photon scattering experiment has been performed on the odd-A nucleus ${}_{}{}^{143}{}_{}{}^{}\mathrm{Nd}$. Strong dipole excitations have been detected in the energy region around 3.2 MeV. This is near the expected position of the two-phonon ($2^{+}$⊗$3^{\mathrm{-}}$) multiplet in the even-even neighboring nucleus ${}_{}{}^{142}{}_{}{}^{}\mathrm{Nd}$. The summed dipole strength between 2.8 and 3.6 MeV in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Nd}$ is in agreement with the sum rule for weak particle coupling to the core nucleus ${}_{}{}^{142}{}_{}{}^{}\mathrm{Nd}$. Model calculations in a harmonic approximation are in a very good agreement with the experiment and they suggest a two-phonon ($2^{+}$⊗$3^{\mathrm{-}}$) particle structure of the excitations in ${}_{}{}^{143}{}_{}{}^{}\mathrm{Nd}$.