Coulomb excitation Mössbauer effect experiments have been performed on the first excited state of ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ using Th-metal targets and Th-metal and various Th-compound absorbers. The metal is shown to yield a Mössbauer linewidth in agreement with that predicted by electronic measurements of the half-life of the first excited state. The zero-thickness absorber linewidth (half width at half maximum), absorber recoilless fraction, and source recoilless fraction were found to be ${\Gamma }_0=8.66\mathrm{}\pm 0.64$ mm/sec, $f_a=0.45\mathrm{}\pm 0.12$, and $f_s=0.23\mathrm{}\pm 0.08$, respectively, for Th metal. Experiments performed on noncubic absorber materials gave broadened spectra which are attributed to electric quadrupole hyperfine interactions.

[NUCLEAR REACTIONS ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}(\alpha ,\alpha )$, $E=49.4\mathrm{}$ keV; measured Mössbauer effect. ${}_{}{}^{232}{}_{}{}^{}\mathrm{Th}$ level deduced $T_{\frac{1}{2}}$, hyperfine fields.]

• Received 2 August 1973

DOI:https://doi.org/10.1103/PhysRevC.8.2302