Observation of Natural Linewidth for the 35.5-keVγResonance inTe125

Linewidth measurements of Cu: ${\mathrm{Sb}}^{125}$ sources as a function of cubic ZnTe absorber thickness are performed at 4.2 and 78°K. The data show that ${\Gamma }_{\mathrm{source}}=5.20\mathrm{}\pm 0.08$ mm/sec and that the Debye temperature ${\Theta }_D$ of cubic ZnTe is (175 ± 9) °K. Sizable line broadening is observed in commercially obtained polycrystalline ZnTe. This is attributed to the presence of hexagonal ZnTe in such samples. The quadrupole splitting in Te metal at 78 °K is measured to be 7.30 ± 0.08 mm/sec.