Low-lying Gamow-Teller states inNb92

Cross sections for the (p,n) reaction on targets of $^{90}\mathrm{Zr}$ and $^{92}\mathrm{Zr}$ have been measured at 26 MeV. Our resolution for these measurements was better than 200 keV and allowed the observation of numerous ${1}^{+}$ states in $^{92}\mathrm{Nb}$ below 7 MeV excitation. Our analysis is focused on states below the primary Gamow-Teller state and shows a fragmentation of the Gamow-Teller strength that is only partially accounted for by three different model calculations: a quasiparticle model, a shell model, and a random-phase approximation calculation. All three models yield predictions which include appreciable strength between 3 and 7 MeV excitation, but fail to describe our experimental results in detail. \textcopyright{} 1996 The American Physical Society.