NUCLEAR PHYSICS A, cilt.788, 2007 (SCI-Expanded)
The Sn-112,Sn-120(gamma, gamma ') reactions were studied for different endpoint energies of the incident bremsstrahlung spectrum below the neutron separation energies at the superconducting Darmstadt electron linear accelerator S-DALINAC. Dipole transition strength distributions have been extracted for Sn-112; the analysis of Sn-120 is Still in progress. In the case of Sn-112 a concentration of dipole excitations is observed between 5 and 8 MeV. Combining with existing data for Sn-116,Sn-124 provides a systematics of the pygmy dipole resonance (PDR) in stable Sn nuclei which serves as a benchmark test of recent microscopic calculations aiming at a description of the PDR in exotic neutron-rich Sn isotopes.