Surface studies by means of the Moessbauer effect

The advantages of the use of the Moessbauer effect in the study of surface properties are pointed out. A seven page summary of some basic aspects of the theory (recoilless fraction, isomer shift and second-order Doppler shift, and magnetic and electric field effects) is given, followed by a two page description of the experimental problems, apparatus and procedure. The Moessbauer effect of 57Fe on the surface of polycrystalline tungsten has been measured at several temperatures between 100 and 500 degrees Kelvin and at angles of zero and sixty degrees with respect to the surface normal. The observed asymmetry in the surface spectra, the angular dependence of the shape, and the magnitude of the line splitting are attributed to surface quadrupole splitting. The Moessbauer spectra on polycrystalline tungsten are graphically given for measurements at 100 degrees Kelvin. The importance of the electronic and lattice vibrational properties of surface atoms in practical situations is mentioned, and the use of the Moessbauer effect to microscopically sense electric and magnetic fields, electronic charge densities, and details in lattice bonds, is advocated. 18 refs, 6 figs