Neutrons and Gamma Rays from the Bombardment ofO16byHe3

Abstract

The threshold energy for the ${\mathrm{O}}^{16}({\mathrm{He}}^3, n){\mathrm{Ne}}^{18}$ reaction has been measured. The value obtained, 3.811±0.015 Mev, determines the mass of ${\mathrm{Ne}}^{18}$ to be 18.011446±0.000014 amu (${\mathrm{O}}^{16}$ standard, 1960 mass tables). The slow-fast ratio method for the observation of neutron thresholds was employed at bombarding energies from the ground-state threshold to 5.6 Mev, corresponding to a region of excitation in the residual nucleus from zero to 1.5 Mev. No excited states in ${\mathrm{Ne}}^{18}$ were identified. The bombardment of ${\mathrm{O}}^{16}$ by ${\mathrm{He}}^3$ also produced the reactions ${\mathrm{O}}^{16}({\mathrm{He}}^3, p){\mathrm{F}}^{18}$ and ${\mathrm{O}}^{16}({\mathrm{He}}^3, \alpha ){\mathrm{O}}^{15}$. Energy spectra were obtained by means of a scintillation spectrometer for gamma rays resulting from certain transitions in ${\mathrm{F}}^{18}$ and ${\mathrm{O}}^{15}$. For 4.5-Mev ${\mathrm{He}}^3$ particles impinging on a 1-Mev thick target of Ti${\mathrm{O}}_2$, gamma rays of the following energies were observed and attributed to ${\mathrm{F}}^{18}$: 0.652±0.007, 0.939±0.005, 1.041±0.005, 1.17±0.01, 1.61±0.02, 1.68±0.02, 2.09±0.01, 2.51±0.01, 2.65±0.05, 3.06±0.05, 3.35±0.10?, and 3.84±0.10 Mev. The following gamma rays were also observed and attributed to ${\mathrm{O}}^{15}$: 5.25±0.05, 6.22±0.10, and 6.87±0.10 Mev.