Inelastic Scattering

Abstract

Historically the initial utilization of synchrotron radiation has been closely tied to various absorption spectroscopies. Successful photoemission and exafs studies have also been responsible for the rapid growth in synchrotron radiation research activity. However, as useful and important as those techniques are, it is highly likely that the second generation of dedicated facilities and synchrotron users will be remembered for the beginning of a successful utilization of scattering techniques. The delay in the application of synchrotron radiation inelastic scattering techniques is directly related to the fact that for most inelastic scattering experiments momentum resolution is not critical. Thus one can afford to collect a relatively large solid angle (typically 2° × 2°) of the characteristic emission of a conventional source for the experiment. In the above solid angle a 10-kW x-ray tube would provide 10¹² photons/s in the Kα 2.5-eV-wide emission line. This is slightly more than has been available in the most intense beam line at the Stanford Synchrotron Radiation Laboratory. Even for that flux inelastic scattering experiments typically produced counting rates of only 1–10/s. However, dedicated sources hold the promise of 10¹³–10¹⁴ photons/s in a 1-eV bandwidth. When these sources are in operation, a whole new generation of experiments will become possible. The breath of new studies is made possible not only because of the high flux, but also because the high collimation and tunability of the synchrotron radiation enables one to perform high-energy resolution and/or resonant types of experiments. Those experiments are virtually impossible with a conventional source.