X-ray Raman scattering under pulsed excitation

Accounting for actual and anticipated developments in synchrotron radiation - and in x-ray and free electron laser techniques, we present a theory of r esonant scattering of short-pulsed x rays. Both the instantaneous and integ rated-over-observation-time x-ray scattering spectra are studied. Contrary to the commonly accepted notion of an instantaneous probability, we find th at the correct quantity describing the resonant x-ray scattering (RXS) expe riment is the probability integrated over the time of measurement. It is sh own that the integral RXS probability is given by the convolution of the RX S probability for monochromatic excitation with the Wiener-Khintchine spect rum of the nonstationary incident radiation. We have found that short pulse s yield a new spectral band following a non-Raman dispersion law. The finit e duration of pulses results in a broadening of the Raman resonance. Some a spects of the theoretical analysis of the RXS spectra as functions of the p ulse duration time are analyzed by numerical calculations. (C) 2000 America n Institute of Physics. [S0021-9606(00)01313-1].