The Mossbauer Recoilless Fraction of Gold

摘要

The Mossbauer recoilless fraction, f, of the 77-keV gamma ray of Au197 in a gold metal absorber has been measured as a function of temperature between 4.5 and 100°K. The source was Au197 in platinum metal. The Mossbauer spectrum was fit with the absorption integral, and the recoilless fraction was derived from the shape and width of the spectrum. The recoilless fraction varies between 0.17 at 4.5°K and 0.01 at 100°K. The analysis indicates that the source and absorber lines are Lorentzian and have approxi¬mately equal widths, 0.937 ± 0.011 mm/sec. Shirley's theoretical estimate of the in¬ternal conversion coefficient, 3.96 ± 0.14, was assumed in the recoilless fraction calculations. The Debye temperature vs temperature corresponding to the mea¬sured recoilless fraction was compared to that derived from theoretical phonon frequency distributions reported in the litera¬ture. An appendix gives many general prop¬erties of the Mossbauer absorption integral.