Gamow–Teller strength extraction from (3He, t) reactions

Abstract

Abstract Details of Gamow–Teller (GT) and Fermi (F) strength extraction from charge-exchange reactions at intermediate energies, as well as the concept of using the phenomenological effective interaction for the description of the reactions are reviewed. The focus lies on high-resolution ( 3 He, t ) data, yet new data on ( d , 2 He) charge-exchange reactions are presented as well to indicate the connection and the similarity of both probes to the elementary ( p , n ) , resp. ( n , p ) reactions. We show that for the extraction of B ( GT ) and B ( F ) strength a proper extrapolation of the charge-exchange cross section to the zero momentum transfer point, q = 0 , gets to be increasingly important for medium to high-mass target nuclei and at moderate excitation energies of a few MeV. Numerous ( 3 He, t ) and ( p , n ) spectra are being compared, and, once adjusted for the different momentum transfers, they reveal a remarkable similarity up to the highest measured excitation energies of ≈ 25 MeV . Further, we remark that the precision, with which GT and F transition strengths can be extracted, is limited by the relatively poor knowledge of the absorption processes, and a more thorough theoretical understanding of the nuclear structure leading to absorption in charge-exchange reactions, especially in the restricted kinematic region of low-momentum transfers, is warranted. Finally, B ( GT ) values for the 136 Xe( 3 He, t ) are being re-evaluated in the light of the present discussion.