Accurate Determinations of Nuclear Reaction Energies

A precise magnetic spectrometer of the annular type is described; the focusing properties and line shapes are analyzed. The use of the instrument to measure absolute particle momenta in terms of the proton magnetic moment precessional frequency and a standard length is presented for three nuclear transmutations and for the determination of the energy necessary to excite a state in ${\mathrm{Ne}}^{20}$. The $Q$ values obtained are: ${\mathrm{C}}^{12}(d, p){\mathrm{C}}^{13}$, $Q=2.722\mathrm{}\pm 0.004$ Mev; ${\mathrm{O}}^{16}(d, \alpha ){\mathrm{N}}^{14}$, $Q=3.119\mathrm{}\pm 0.005$ Mev; and ${\mathrm{Li}}^7(p, \alpha ){\mathrm{He}}^4$, $Q=17.344\mathrm{}\pm 0.013$ Mev. The energy at a resonance in the reaction ${\mathrm{F}}^{19}(p, \alpha \gamma ){\mathrm{O}}^{16}$ was determined to be 872.5±1.8 kev.