Asymmetry parameters in183W and182W using mice detection with a crystal monochromator

Using exceptionally high intensity Mössbauer sources (～ 1–100 Ci) of¹⁸²Ta and¹⁸³Ta, we have measured the Mössbauer effect for the 46.5 and 99.1 keV transitions of¹⁸³W and the 100.1 keV transition of¹⁸²W. Using a microfoil internal conversion electron (MICE) /1/ detector capable of operation at low temperatures, and a LiF crystal monochromator, we obtain effects of nearly 600% for the 46.5 keV transition and 3 1/2% and 6% for the other two cases, while standard transmission measurements typically yield much smaller signal-to-background ratios. With this technique we have measured the asymmetry term in the conversion electron spectra. To our present level of accuracy the results are in agreement with theoretical calculations of interference parameters /2/. Our results do not agree with earlier measurements /3/ on this transition, which are grossly at variance with theoretical calculations of the interference parameter.