Non-spin-flip ( 3He, t) charge-exchange and isobaric analog states of actinide nuclei studied at [formula omitted] and 200 MeV

Abstract

The ( 3He, t) charge-exchange reaction has been studied at θ = 0° and bombarding energies of E( 3 He) = 76.5 MeV and 200 MeV . Spectra were measured using magnetic analysis for target nuclei of 12, 13C, 16O, 19F, 28, 29, 30Si, 90Zr, 117, 120Sn, natTa, natW, 197Au, 208Pb, 230, 232Th, 234, 236, 238U and 244Pu. The measurements at 76.5 MeV concentrated on the isobaric analog states of several actinide nuclei, particularly on their widths and the branching ratios for proton decay. Cross sections, Q-values and total widths were determined for the transitions to the isobaric analog states. Coulomb displacement energies derived from the measured Q-values display the influence of deformed nuclear shapes. Escape widths Γ ↑ and spreading widths Γ ↓ of the isobaric analog states in five actinide nuclei were deduced from the measured proton-decay branching ratios. They were found to be in agreement with predictions which postulate isospin mixing via the Coulomb force with the ( T 0−1)-component of the isovector giant monopole resonance. The measurements at 200 MeV were concerned with transitions to isobaric analog states in both light and heavy nuclei, including several actinide nuclei, but Gamow-Teller resonances and transitions to numerous other states were also observed. The measured cross sections for several transitions to isobaric analog states from 30Si to 208Pb were used to extract the effective interaction V τ for non-spin-flip ( 3He, t) charge exchange at E( 3 He) ≈ 200 MeV . The interaction strength V τ decreases by a factor 0.6 when compared to previously measured values for the energy range E( 3 He) = 65 to 90 MeV . An angular distribution from θ τ = 0° to 16° for the transition to the isobaric analog state in 120Sb measured at E( 3 He) = 200 MeV was found to be in very good agreement with microscopic calculations.