Two-phonon 1- state in Sn-112 observed in resonant photon scattering

Results of a photon scattering experiment on $^{112}\mathrm{Sn}$ using bremsstrahlung with an endpoint energy of ${E}_{0}=3.8$ MeV are reported. A $J=1$ state at ${E}_{x}=3434(1)$ keV has been excited. Its decay width into the ground state amounts to ${\ensuremath{\Gamma}}_{0}=151(17)$ meV, making it a candidate for a $[{2}^{+}\ensuremath{\bigotimes}{3}^{\ensuremath{-}}]{1}^{\ensuremath{-}}$ two-phonon state. The results for $^{112}\mathrm{Sn}$ are compared with quasiparticle-phonon model calculations as well as the systematics of the lowest lying ${1}^{\ensuremath{-}}$ states established in other even-mass tin isotopes. In contrast to findings in the heavier stable even-mass Sn isotopes, no ${2}^{+}$ states between 2 and 3.5 MeV excitation energy have been detected in the present experiment.