High-Energy Gamma Radiation from Lithium Bombardment of Be9, B10, B11, and C12

Abstract

Gamma-ray spectra have been obtained with a 5-×6-in. NaI(Tl) crystal for the bombardment of thick ${\mathrm{Be}}^9$, ${\mathrm{B}}^{10}$, ${\mathrm{B}}^{11}$, and ${\mathrm{C}}^{12}$ targets with ${\mathrm{Li}}^6$ and ${\mathrm{Li}}^7$ beams. Intensities and source assignments are given for all gamma rays observed with an energy of 8 MeV or more. The probable gamma decay of the 9.83-MeV state in ${\mathrm{N}}^{15}$ was observed for several target-beam combinations. In the ${\mathrm{Li}}^6$ + ${\mathrm{B}}^{10}$ reaction, the population of the 9.17-MeV state in ${\mathrm{N}}^{14}$ and the 15.11-MeV state in ${\mathrm{C}}^{12}$ was observed. The population of these states is forbidden by isotopic-spin selection rules. For each reaction upper-limit total cross sections are about 1 μb for the production of the compound nucleus with subsequent gamma decay. This indicates that compound nuclei are not formed to any significant degree in these reactions.