Gamma-Ray Widths of the 3.00-MeV Level ofAl27and the 3.13-MeV Level ofP31

Abstract

Nuclear resonant scattering of bremsstrahlung by the 3.00-MeV level of ${\mathrm{Al}}^{27}$ has been observed. From comparison with resonant scattering by the 2.98-MeV level of ${\mathrm{Al}}^{27}$, and with the branching taken from the literature as $\frac{{\Gamma }_0}{\Gamma }=0.87\mathrm{}$, widths ${\Gamma }_0=5.3\mathrm{}\pm 1.0$ meV and $\Gamma =6.1\mathrm{}\pm 1.2$ meV are obtained. These values are in some disagreement with inelastic electron scattering results. Comparison with Doppler-shift values tends to verify $\mathrm{spin}=\frac{9}{2}$ for the 3.00-MeV level and to rule out $\mathrm{spin}=\frac{3}{2}$. Self-absorption measurements of the resonant scattering by the 2.21- and 2.98-MeV levels of ${\mathrm{Al}}^{27}$ give $\Gamma ={{17.6}_{-3.3\mathrm{}}}^{+2.9\mathrm{}}$ meV and $\Gamma ={{125}_{-13\mathrm{}}}^{+14\mathrm{}}$ meV, in agreement with previous results. Self-absorption measurements for the 3.13-MeV level of ${\mathrm{P}}^{31}$ give $\Gamma =66.3\mathrm{}\pm 7$ meV.