The reactions ${}_{}{}^6{}_{}{}^{}\mathrm{Li}\mathrm{}(p,pn)\mathrm{}{}_{}{}^5{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^9{}_{}{}^{}\mathrm{Be}\mathrm{}(p,pn)\mathrm{}{}_{}{}^8{}_{}{}^{}\mathrm{Be}$, and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}\mathrm{}(p,pn)\mathrm{}{}_{}{}^{12}{}_{}{}^{}\mathrm{C}$, as well as the reaction ${}_{}{}^6{}_{}{}^{}\mathrm{Li}\mathrm{}(p,2p)\mathrm{}{}_{}{}^5{}_{}{}^{}\mathrm{He}$, have been studied at 46 MeV. The plane-wave impulse approximation (PWIA) has been used for a preliminary analysis. The ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ and ${}_{}{}^{13}{}_{}{}^{}\mathrm{C}$ cross sections show a pronounced $p$-state minimum near zero recoil momentum as expected in the PWIA. No such minimum is seen for either reaction of ${}_{}{}^6{}_{}{}^{}\mathrm{Li}$. The angular dependence of the three ($p,pn$) reactions departs strongly from PWIA predictions.

• Received 26 December 1973

DOI:https://doi.org/10.1103/PhysRevLett.32.684