Evidence concerning Δ-hole states

Recent (p,n) experiments at intermediate energy at the Indiana University Cyclotron have been used to study the spin-isospin transfer response function of nuclei. In particular forward angle spectra are dominated by neutron peaks characterized with ΔL = 0 transfer, which have been identified as Gamow-Teller (GT) 1+ states. The GT strength function in nuclei throughout the periodic table is presented. The sum of the total observed GT strength is compared to a model independent sum rule to obtain an A dependence of the quenching. General features of GT strength distributions are presented and discussed. A especial effort is made to estimate how much of the GT strength resides at excitation energies between 20 - 40 MeV. The fact that less GT strength is observed than is expected (either calculations or sum rule) may be associated with intrinsic nucleon degrees of freedom, in particular the excitation of Δ-hole states. 14 references, 9 figures