Study of the ReactionNe20(α, α′γ)Ne20

Abstract

Particle-gamma coincidence spectra of the reaction ${\mathrm{Ne}}^{20}(\alpha , {\alpha }^{\prime }\gamma ){\mathrm{Ne}}^{20}$ provide evidence for the existence of two, new, gamma-emitting levels in ${\mathrm{Ne}}^{20}$. A new level at 7.93 MeV is observed to decay by gamma emission to the 4.97-MeV ($2^{-}$) level; a new level at 5.88 MeV is observed to decay to the 4.25-MeV ($4^{+}$) level. Tentative spin-parity assignments are $3^{+}$ for the 5.88-MeV level and $1^{+}$, $2^{-}$, $3^{+}$, or $4^{-}$ for the 7.93-MeV level. Evidence is seen for the recently discovered level at 7.02 MeV ($4^{-}$). The data suggest a considerably larger value of $\frac{\Gamma \gamma }{\Gamma }$ for the 5.63-MeV ($3^{-}$) level than that previously reported. Angular distribution measurements of elastic and inelastic alpha-particle groups are compared with current direct-interaction theory. The production of states of ${\mathrm{Ne}}^{20}$ with $J\ne L$ through inelastic alpha-particle scattering suggests a fairly strong spinorbit interaction between the orbital angular momentum of the incident alpha particle and the spin of one (or more) target nucleons. Possible collective model interpretations of the ${\mathrm{Ne}}^{20}$ level structure are suggested.