Proton Spectra from the Nitrogen Bombardment of Fluorine

Abstract

Energy spectra and absolute differential cross sections of protons from bombardment of ${\mathrm{F}}^{19}$ with 21.4- and 27.4-Mev ${\mathrm{N}}^{14}$ were measured. The energy spectra were analyzed in terms of the statistical model with a level density $\exp \left(\frac{E^{*}}{T}\right)$, where $E^{*}$ is the excitation energy in the residual nucleus of the assumed reaction ${\mathrm{F}}^{19}({\mathrm{N}}^{14}, p)P^{32}$. The nuclear temperature $T$ increased from about 1.9 Mev at 0° to about 2.5 Mev at 145° c.m., but did not vary with bombarding energy. The angular distribution show minima near 90° c.m., with anisotropy increasing as the bombarding energy and proton energy increase. At the lower bombarding energy there is approximate agreement with the Ericson-Strutinski theory of angular-momentum effects in compound-nucleus processes, over the entire observed ranges of angle and proton energy. The fit is consistent with $\sigma =3\mathrm{}$ in the nuclear level spin distribution $\mathrm{}(2j+1)\mathrm{}\exp [-\frac{j(j+1\mathrm{})\mathrm{}}{\left(2\mathrm{}{\sigma }^2\right)}]$. At the higher bombarding energy a considerable excess of protons are emitted into the backward hemisphere, especially at high proton energies, suggesting a direct-interaction mechanism in which the observed proton comes from the ${\mathrm{F}}^{19}$.