9704228 Boolchand This award provides partial support for implementing a new concept of a 67Zn M ssbauer spectrometer which will yield significantly larger (at least a factor of 20) signal to noise ratios than hitherto possible using standard velocity drives in transmission measurements of materials. The novel features of the present concept includes (a) use of a phase modulation drive which avoids any relative motion between source and absorber matrix, and (b) time-filter the re-emitted radiation to discriminate the short lived (10-12s) non-resonant radiation from the long-lived (10-5s) resonant one to enhance the signal to noise ratio. Feature (a) will be implemented by using a rotating wheel consisting of Al wedges which interrupt the -beam from a source to modulate the energy with respect to a stationary absorber. Feature (a) will also permit region of interest velocity scans, an option that will permit a more efficient collection of information with the short-lived M ssbauer parents (67Ga and 67Cu). Feature (b) will be implemented by using a shutter wheel with narrow slits, that will block the -beam from the source while a scintillation detector registers the re- emitted -rays and conversion electrons from the absorber. Implementation of these features at 4.2K will be done by supporting the wheels in an exchange gas column of a liquid Helium dewar. The project will demonstrate the enormous cost advantage of obtaining Zn spectra using the new spectrometer and should make possible obtaining spectra of Zn compounds of normal enrichment. Such an experimental facility will have important consequences in the field of basic materials research. High resolution studies of Zn based inorganic compounds in absorption and Cu- and Ga-based compounds in emission spectroscopy will permit addressing outstanding materials science issues in a wide variety of materials including II-VI, III-V and II-IV-V2 semiconductors, cuprate superconductors, galvanization of steels, Zn-ferrites, Zn-spinels and zinc based enzymes.
