Detection of neutron-excess isotopes of low-Zelements produced in high-energy nuclear reactions

Abstract

A search was made for new isotopes of the elements lithium through nitrogen produced in the high-energy (4.8-GeV) proton irradiation of a uranium target. The fragments were identified by $\Delta E-E$ and time-of-flight techniques. An electronic pulse-width discriminator greatly reduced the background allowing high sensitivity. A new method for analyzing time-of-flight data and a new algorithm for particle identification were introduced. Two new isotopes, ${}_{}{}^{14}{}_{}{}^{}\mathrm{Be}$ and ${}_{}{}^{17}{}_{}{}^{}\mathrm{B}$, were observed to be particle stable and the existence of ${}_{}{}^{19}{}_{}{}^{}\mathrm{C}$ was confirmed. It was shown that ${}_{}{}^{12}{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^{16}{}_{}{}^{}\mathrm{B}$ are particle unbound. Approximate production cross sections were determined for ${}_{}{}^{14}{}_{}{}^{}\mathrm{Be}$, ${}_{}{}^{17}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{18}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{19}{}_{}{}^{}\mathrm{C}$, and upper limits estimated for ${}_{}{}^{13}{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^{19}{}_{}{}^{}\mathrm{B}$, ${}_{}{}^{20}{}_{}{}^{}\mathrm{C}$, and ${}_{}{}^{22}{}_{}{}^{}\mathrm{N}$.