Absolute differential cross sections for the elastic scattering of alpha particles by ${\mathrm{N}}^{15}$ have been measured in a differentially-pumped gas scattering chamber. The measurements were made at center-of-mass angles of 169.1, 149.5, 140.8, 125.3, 90.0, and 70.0 degrees for alpha-particle energies from 1.75 to 5.50 Mev, corresponding to 5.37- to 8.33-Mev excitation of the compound nucleus ${\mathrm{F}}^{19}$. The experimental widths of the levels observed below approximately 3.5-Mev bombarding energy are generally narrow, in most cases less than 10 kev. Above 3.5 Mev a marked increase in the level width was observed. As a result of an analysis based on the Wigner-Eisenbud reaction theory, values of $J$, $\pi$, $E_{\lambda }$, and ${{\gamma }_{\lambda }}^2$ were assigned to 16 levels in ${\mathrm{F}}^{19}$.

• Received 24 August 1960

DOI:https://doi.org/10.1103/PhysRev.122.232