Isobaric analog states of the tin and tellurium isotopes studied with the ( 3He, t) reaction at θ L = 0°

Abstract

The Sn( 3He, t)Sb and Te( 3He, t)I reactions to the g.s. isobaric analog states (IAS) of 112, 114, 116, 117, 118, 119, 120, 122, 124Sn and 124, 125, 126, 128, 130Te have been studied at θ = 0° and E( 3 He) = 45.9 MeV . The Coulomb displacement energies decrease more slowly than A − 1 3 indicating that the rms radius of the nuclear matter distribution increases more slowly than A 1 3 . The total widths of the IAS are 10 to 60 keV and exhibit a pronounced odd- A even- A variation correlated with the excitation and decay energies of the IAS. Estimates of the decay and spreading widths have been obtained, with the latter yielding an isospin-mixing matrix element of about 1 keV. The ( 3He, t) cross sections at 0° appear to be directly related to (p, n) total cross sections for the 0 + IAS. The cross sections for the Sn-Sb and Te-I isotopes, in contrast to accepted expressions, depend in a complicated manner on the neutron excess. A microscopic analysis gives an effective interaction ( μ = 1 fm −1) of V t· t = 11 ± 4 MeV. This is smaller than values obtained from analyses of ( 3He, t) reactions on nuclei with A ⪅ 90, if one assumes a simple direct charge-exchange reaction.