Gamow-Teller and spin-dipole strength in 90Zr(n,p) at 65 MeV.

Abstract

The $^{90}\mathrm{Zr}$(n,p) reaction at 65 MeV has been studied over a wide range of angles down to 0\ifmmode^\circ\else\textdegree\fi{}. At low excitations the main strength appears to be in three concentrations of spin-dipole strength. Within certain limits Gamow-Teller ${\ensuremath{\beta}}^{+}$ strength is not evident in the spectra. Together with the earlier analysis of ${\ensuremath{\beta}}^{\mathrm{\ensuremath{-}}}$ strength in $^{90}\mathrm{Zr}$(p,n) these (n,p) results suggest either (1) that Gamow-Teller quenching due to \ensuremath{\Delta}(isobar)-hole mixing in nuclear particle-hole excitations is relatively small (\ensuremath{\lesssim}15%), or (2) that \ensuremath{\Delta}-hole quenching is percentagewise much larger (x5) for ${\ensuremath{\beta}}^{+}$ than for ${\ensuremath{\beta}}^{\mathrm{\ensuremath{-}}}$ transitions.