Electromagnetic properties of the 11/2^- states in ¹¹¹Sn and ¹¹³Sn

Abstract

In order to study the core polarization effects in medium heavy spherical nuclei the mean lives and g factors of the 11/2^- states in ¹¹¹Sn and ¹¹³Sn have been measured. The isomeric states were populated by the ¹¹¹Cd(α,2n)¹¹³Sn and ^107,109Ag(⁷Li,3n)^111,113Sn reactions with pulsed a and ⁷Li beams. The nuclear spin precession in the 60 kG field of an on-line superconducting magnet was observed time differentially. The following values were obtained: ¹¹¹Sn (11/2^-, 979.6 keV): t=13.3(15) ns, g=-0.23(2); ¹¹³Sn (11/2^-, 740 keV): t=118.5(25) ns, g=-0.235(4). The magnetic moments of the 11/2^- states in ^{111,113,115,119}Sn and their near constancy as a function of mass number are reproduced by a first order M1 core polarization calculation using pairing model wave functions, experimentally determined energy denominators, and occupancy parameters. The strong reduction of the M2 rates for the h_11/2→g_7/2 transition as compared to the single particle estimate shows the destructive effect of the spin-isospin M2 core polarization.