Isobaric analog states in rare-earth nuclei studied with the (3He, t) charge-exchange reaction at [theta]L = 0[deg]

Abstract

The (3He, t) charge-exchange reaction leading to the ground-state isobaric analog states (IAS) of 152, 154, 156, 158, 160Gd, 160,162Dy, 162,164,166,168,170Er, 170, 172, 174, 176Yb and 176, 178, 180Hf has been studied at [theta]L = 0[deg] and E(3He) = 60.5 MeV. The reaction 28Si(3He, t)28P was used for energy calibration. The centroid energies of most IAS were determined to +/-6 keV. Coulomb displacement energies have been extracted from the measured Q-values. They display the influence of non-spherical nuclear shapes which increase the rms radii and lower the Coulomb displacement energies. The dependence on both quadrupole and hexadecapole deformations is apparent with deformation parameters in good agreement with results from other measurements. The total widths [Gamma] of the IAS are in the range 30 to 110 keV. They increase more strongly with neutron excess than is known for the IAS of the Sn and Te isotopes. The width of the IAS of 176Yb is anomalously low. The zero-degree (3He, t) cross sections are in the range 5 to 20 [mu]b/sr. They generally increase with neutron excess except for the sequence of Yb isotopes. No systematic dependence on (N - Z) appears to exist. Excitation energies and zero-degree cross sections for the reactions 28Si(3He, t)28P, 16O(3He,t)16F and 12C(3He,t)12N are reported.