DIPOLE EXCITATIONS TO BOUND-STATES IN SN-116 AND SN-124

Dipole transitions to bound states in the Sn nuclei Sn-116 and Sn-124 have been investigated by means of nuclear resonance fluorescence (NRF ) using 12 MeV linearly polarized bremsstrahlung and unpolarized brems strahlung with different end point energies (4.1, 7.5, and 10 MeV). Th e measurements enable the determination in a completely model-independ ent way of reduced transition probabilities, multipolarities, and pari ties of the observed transitions. More than 150 new dipole ground stat e transitions have been identified. The observed dipole strength distr ibution displays for both isotopes a clear concentration around 6.5 Me V. For about half of the observed dipole excitations parities could be extracted. They all turned out to be E1 excitations except for three tentative M1 assignments. The NRF results are compared with data from tagged photon scattering experiments and quasiparticle phonon model ca lculations. [S0556-2813(98)05105-X].