TIME-DOMAIN SPECTROSCOPY OF RECOILLESS GAMMA-RAYS

Alternatives to the conventional Doppler-scanning method of Mössbauer spectroscopy, which might offer improved resolution in spectroscopy of recoilless gamma rays, are considered. It is shown that the gamma ray frequency spectrum can be determined by observation of the time-distribution of delayed coincidence counts of photons transmitted by a stationary resonant filter. This may be the best alternative to Doppler scanning for long-lived transitions, especially if experiments to reduce the inhomogeneous linebreadth are to be undertaken. Some practical aspects of the design of systems for making this measurement are discussed, and experiments are suggested which would evaluate the method with known Mössbauer isotopes. In particular, it is suggested that one may be able to resolve the hyperfine splitting in natural iron and that one might observe dependence of the linebreadth upon the direction of emission from an oriented iron-57 nucleus and on the hydrogen concentration in metallic tantalum. Long counting times and high background of chance coincidences are the principal limitations to the technique. © 1979.