Experimental Study of the Low-Lying Levels ofSi31

Abstract

The 0.76-, 1.70-, 2.32-, 2.79-, and 3.54-MeV levels of ${\mathrm{Si}}^{31}$ have been studied using a collinear geometry with the observed particles being detected in an annular solid-state counter placed at 180° relative to the beam direction. The above levels were populated by the ${\mathrm{Si}}^{30}\mathrm{}(d,p)\mathrm{}{\mathrm{Si}}^{31}$ reaction with deuteron energies of 3.01 and 3.22 MeV. $\gamma$ radiation was detected by a 7.62×7.62-cm NaI crystal at five angles between 26° and 90° relative to the beam direction. From the analysis of the experimental correlations, spin determinations of $\frac{5}{2}$, $\frac{3}{2}$, $\frac{7}{2}$ and $\frac{3}{2}$ were established for the 1.70-, 2.32-, 3.14-, and 3.54-MeV levels, respectively. An isotropic correlation was measured for the level at 760 keV, in agreement with the known spin of ½ for this level. The analysis for the 2.79-MeV level agrees with the spin value of $\frac{5}{2}$ which is indicated from the shape of the $l_n=2\mathrm{}$ angular distribution from the ${\mathrm{Si}}^{30}\mathrm{}(d,p)\mathrm{}$ reaction corresponding to population of this level. In addition, information on the $\gamma$-ray multipole mixing ratios and $\gamma$-ray branching ratios for many of the above levels was determined.