Shell-model study of spin-dipole strength in 12C and 16O

We have studied effects of tensor correlations and couplings to 3 (h) over bar omega excitations on the quenching of spin-dipole strengths in C-12 and O-16 by large scale shell model calculations, We found that the transition strengths in the energy range E-x = (20-40) MeV in C-12 are quenched by about 20% due to the coupling to the 3 (h) over bar omega configuration space, and by additional 10% due to the tensor interaction. There is also a similar quenching of spin-dipole strengths for 1(-) states in O-16. The calculated results are compared with available experimental data of spin-dipole states observed by charge exchange (p, n) and ((d) over right arrow, He-2) reactions on C-12. An astrophysical implication of spin-dipole strengths in O-16 for detections of supernova neutrinos is also discussed. (C) 1998 Elsevier Science B.V.