Properties of Excited States ofP31. II. Gamma-Ray Angular Distributions and Correlations

Angular distributions and triple correlations of gamma rays emitted from several resonances in the range $E_p=1177\mathrm{} \mathrm{to} 1509$ keV in the ${\mathrm{Si}}^{30}(p, \gamma )P^{31}$ reaction have been measured using thin, highly enriched ${\mathrm{Si}}^{30}$ targets. The decay schemes of these resonances and of intermediate levels excited in ${\mathrm{P}}^{31}$ were presented in an earlier paper (I). The angular distributions and correlations lead to the resonance level assignments $1177\left(\frac{7}{2}\right)$, $1204\left(\frac{5}{2}\right)$, $1324\left(\frac{5}{2}\right)$, $1392\left(\frac{5}{2}\right)$, $1400\left(\frac{3}{2}\right)$, $1489\left(\frac{3}{2}\right)$, and $1509\left(\frac{5}{2}\right)$ where the proton resonance energies are in keV. The results indicate even parity for all of the resonances if it is assumed that all gamma-ray multipolarity mixings are of the form $\frac{E(L+1\mathrm{})\mathrm{}}{M\left(L\right)\mathrm{}}$. The mixing ratios (all of the type $\frac{E2\mathrm{}}{M1\mathrm{}}$) are presented for most of the observed primary transitions and of several secondary transitions. The results of this study are consistent with the assignments $\frac{3}{2}+$, $\frac{5}{2}+$, $\frac{3}{2}+$, $\frac{5}{2}+$, $\frac{3}{2}+$, and $\frac{5}{2}+$ made elsewhere for the 1.27-, 2.23-, 3.13-, 3.29-, 3.51-, and 4.19-MeV levels of ${\mathrm{P}}^{31}$. The 3.41-MeV level is identified as $\frac{7}{2}+$ by means of angular-distribution and correlation measurements at the 1509-keV resonance. A $\frac{7}{2}+$ assignment for the 3.41-MeV level casts doubt upon the existence of a weak transition, which has been reported by earlier workers and in I, from that level to the ½+ ground state. Results of several measurements designed to determine the origin of the weak gamma-ray peak of approximately 3.4 MeV in coincidence spectra at the 1509-keV resonance were inconclusive. Angular distributions at the 1204-keV resonance lead to the assignment of $\frac{3}{2}+$ to the 4.26-MeV level. Limitations are placed on the possible assignments for the 4.43- and 5.01-MeV levels. Both members of the recently discovered doublet near $E_p=1481\mathrm{}$ keV are found to decay mainly to the ground state, and each have