Proton Resonances in the Deuteron Bombardment of Carbon

Abstract

The protons resulting from the deuteron bombardment of ${\mathrm{C}}^{12}$ have been studied in some detail, with particular emphasis on the variation of the intensity of the long-range protons with energy and angle. Excitation curves at three fixed angles, one forward, one backward, and one at 90° to the beam, show peaks which in some cases agree in energy with one another and with neutron and gamma-peaks observed in the same bombardment elsewhere. In other cases, however, there is no peak on one mode of observation at an energy where one appears in another. In some cases peaks in different modes of observation which do not quite coincide in energy are so close together that it seems reasonable to attribute them to the same virtual level of the compound nucleus, and the existence of the small energy discrepancies is discussed. Two shorter range groups of protons are studied less extensively because they penetrate the thin windows only at high bombarding energies, and their range coincides with that of the scattered deuterons at some bombarding energies. The two short range groups indicate excited states of ${\mathrm{C}}^{13}$ at 3.12 and 3.91 Mev. A possible low excited state near 0.8 Mev, suspected from an alpha-induced reaction, is not confirmed. The transition to it cannot be shown to be absent but only weak because protons indicating its existence could be masked by protons observed from an oxygen impurity. Of the three angular distributions observed in detail, the one at the lowest bombarding energy is the simplest, in keeping with the expectation that only deuterons of low angular momentum penetrate at low energies.