Differential cross sections for the elastic scattering of alpha particles by neon have been measured at four angles for alpha energies from 2 to 4 Mev. Absolute values of the cross section are good to ±4 percent. The angles chosen correspond to center-of-mass angles such as to simplify assignments of angular momentum to the scattered resonance wave. Because no nuclear spins are involved, the angular momentum of the scattered wave also fixes the parity and angular momentum of the compound state.

Thirteen resonances were observed. Eleven are attributed to virtual states of ${\mathrm{Mg}}^{24}$ and two are assigned to virtual states of ${\mathrm{Mg}}^{26}$. The experimental data were analyzed in terms of the Wigner-Eisenbud formalism to determine the additional level parameters: $E_r$, $\gamma {\lambda }^2$ and ${\Delta }_{\lambda }$. The laboratory energies of the (${\mathrm{Ne}}^{20}$+$\alpha$) resonances in Mev, and the total angular momentum and parity assignments of the virtual states are: 2.488($1^{-}$), 2.573 ($0^{+}$), 2.652 ($2^{+}$), 2.903 ($0^{+}$), 3.062 ($1^{-}$), 3.184 ($2^{+}$), 3.548 ($3^{-}$), 3.780 ($1^{-}$), 3.801 ($2^{+}$), 3.839 ($4^{+}$), and 3.923 ($2^{+}$). Similarly, the assignments for (${\mathrm{Ne}}^{22}$+$\alpha$) resonances are 3.245 ($3^{-}$) and 3.418 ($3^{-}$).

The resonances above 3.0-Mev bombarding energy were investigated for competing reactions. No competing reaction with cross sections greater than about one percent of the elastic value were observed.

• Received 12 November 1953

DOI:https://doi.org/10.1103/PhysRev.93.799