Strong fragmentation of low-energy electromagnetic excitation strength in Sn-117

Results of nuclear resonance fluorescence experiments on Sn-117 are reporte d. More than 50 gamma transitions with E gamma < 4 MeV were detected. For t he first time microscopic calculations making use of a complete configurati on space for low-lying states are performed for a heavy odd-mass spherical nucleus. The theoretical predictions are in good agreement with the data. I t is concluded that although the El transitions are the strongest ones also M1 and E2 decays contribute substantially to the observed spectra. In cont rast to the neighboring even Sn116-124 nuclei, in Sn-117 the 1(-) component of the two-phonon [2(1)(+) x 3(1)(-)] multiplet built on top of the 1/2(+) ground state is proved to be fragmented.