Excited States ofB13

Abstract

The energy levels in ${\mathrm{B}}^{13}$ up to an excitation energy of 6 Mev have been investigated by means of the reaction ${\mathrm{Li}}^7({\mathrm{Li}}^7, p){\mathrm{B}}^{13}$ at an energy of 2 Mev for the incident ${\mathrm{Li}}^7$ ions. Selection and identification of the outgoing protons in the presence of deuterons, tritons, and alpha particles emitted in competing reactions is achieved with a proportional counter-CsI(Tl) scintillation counter telescope system which gives a measure of the $\frac{\mathrm{dE}}{\mathrm{dx}}$ and $E$ of the emitted particle. From the observed energy spectrum of protons emitted at 90°, the $Q$-value of the reaction leading to the ground state of ${\mathrm{B}}^{13}$ was determined to be 5.97±0.05 Mev in agreement with a previous measurement by Norbeck, and the energy of excitation of the first four levels in ${\mathrm{B}}^{13}$ were determined to be 3.70±0.05 Mev, 4.16±0.05 Mev, 5.05±0.08 Mev, and 5.5±0.1 Mev. At 90° in the laboratory system the relative intensities of the proton groups leading to the ground state and first four excited states are in the ratios of 1.0:2.6:0.8:1.6:1.0, respectively.