Excitation Function of theC12(p, pn)C11Reaction in the Bev Region

The ratio of the cross section of the ${\mathrm{C}}^{12}(p, pn){\mathrm{C}}^{11}$ reaction to the cross section of the ${\mathrm{Al}}^{27}(p, 3pn){\mathrm{Na}}^{24}$ reaction has been measured in the energy range 400 Mev to 3 Bev. This ratio as well as the excitation curve of the ${\mathrm{C}}^{12}(p, pn){\mathrm{C}}^{11}$ reaction appear to be quite insensitive functions of the energy in the range studied. A possible interpretation is discussed.