The structure of 113Sn from proton and alpha- particle induced reactions

Abstract

The results of in-beam investigations of 113 Sn using the (p,n), (p,3n), (α,n) and (α,2n) reactions are summarized. Excited states have been identified until E x = 4715 MeV and J π = (27/2t -). For a large number of levels mean lifetimes τ have been determined with the DSA method. For the J k = 25/2+ state at E x = 4059 MeV, τ = 1.0(4) ns has been measured with the γ-RF method. The experimental results are compared with the predictions of shell-model calculations. Most of the positive-parity states may be considered as one-or three-quasiparticle neutron excitations of the 2d5/2, 1g7/2, 3s1/2 and 2d3/2 shells, the negative-parity states as the coupling of one 1h11/2 neutron to the two- or four-quasiparticle neutron excitations in the even-mass 112Sn core. For the 25/2+ isomer the three-quasiparticle neutron configuration ν(h 11 2/2 g 7 2/−1 ) has been proposed on the basis of a shell-model analysis using the mass-formula formalism. The experimentally observed yrast states in 50 113 Sn63 are compared with the corresponding states in the valence mirror nucleus 63 145 Eu82 giving remarkable similarities although the parameters for the shell-model calculations differ considerably. The analysis of nearest-neighbour spacing distributions of experimentally obtained 5/2+ states in 113Sn does not allow definite conclusions about regularity or chaos.