Search for the electric dipole excitations to the 3s(1/2)circle times[2(1)(+)3 circle times(-)(1)] multiplet in Sn-117 - art. no. 014309

The odd-mass Sn-117 nucleus was investigated in nuclear resonance fluoresce nce experiments up to an end point energy of the incident photon spectrum o f 4.1 MeV at the bremsstrahlung facility of the Stuttgart University. More than 50 mainly hitherto unknown levels were found. From the measurement of the scattering cross sections model independent absolute excitation strengt hs were extracted. The measured angular distributions suggested the spins o f 11 excited levels. Quasiparticle phonon model calculations including a co mplete configuration space were performed for the first time for a heavy od d-mass spherical nucleus. These calculations give a clear insight in the fr agmentation and distribution of the E1, M1, and E2 excitation strength in t he low energy region. It is proven that the 1(-) component of the two-phono n [2(1)(+) x 3(1)(-)] quintuplet built on top of the 1/2(+) ground state is strongly fragmented. The theoretical calculations are consistent with the experimental data.