Nuclear Structure ofNa22. II. Some Gamma-Ray Doppler-Shift and Correlation Measurements

Abstract

Levels of ${\mathrm{Na}}^{22}$ below an excitation energy of 4.4 MeV have been investigated through the ${\mathrm{F}}^{19}(\alpha , n\gamma ){\mathrm{Na}}^{22}$ and ${\mathrm{Ne}}^{20}({\mathrm{He}}^3, p\gamma ){\mathrm{Na}}^{22}$ reactions. Using the first reaction, initiated in a C${\mathrm{Cl}}_2$ ${\mathrm{F}}_2$ gas target, the Doppler shifts of $\gamma$-ray transitions from the 0.891-, 2.221-, and 2.572-MeV levels were measured using $\alpha$ energies between 4 and 7 MeV. From these results upper limits were placed on the lifetimes of the three initial states. Combining these upper limits with previously obtained lower limits yields the following restrictions on the mean lifetimes (in psec) for these three levels: $8<\mathrm{}\tau <52\mathrm{}$, $11<\mathrm{}\tau <42\mathrm{}$, and $10<\mathrm{}\tau <42\mathrm{}$, respectively. Proton-$\gamma$ angular correlations were measured at $E_{{\mathrm{He}}^3}=6.56\mathrm{}$ MeV using the ${\mathrm{Ne}}^{20}({\mathrm{He}}^3, p\gamma ){\mathrm{Na}}^{22}$ reaction. These results gave information on $\gamma$-ray branching and multipole-mixing ratios and served to limit the possible spin-parity assignments of some of the levels.