EVALUATION OF ACCIDENTAL COINCIDENCES FOR TIME-DIFFERENTIAL MOSSBAUER-SPECTROSCOPY

The accidental coincidences of a measuring system based on time-to-amp litude conversion are considered in some detail for the case of low st arting and high stopping rates. Two types of accidental coincidences a re distinguished, those carrying time information and those without ti me information. Neglecting any deadtime effects of the detectors, anal ytical expressions for the calculation of the time distribution of the random coincidences are evaluated. The analytical expressions have be en confirmed by Monte Carlo simulations. The procedure is applied to t ime-differential Mossbauer spectroscopy in order to extract the time s pectra of true coincidences. The measured spectrum in a time channel t urns out to be a superposition of the true spectrum (true coincidences ),a time integral spectrum (random coincidences),and a weighted superp osition of true spectra of other time channels (random but time carryi ng information). A measurement with a single line Co-57/Rh-source and single line K[Fe(CN)(6)]. 3H(2)O-absorber with stopping rates of 1 MBq shows agreement between the theoretical time-filtered spectra and the corrected measured spectra of true coincidences.