Dispersive XAS at third-generation sources: strengths and limitations

The experience of two years of operation of the ESRF Dispersive XAS beamlin e is reviewed. The examples of experiments performed show that the advent o f third generation sources has given a new perspective to the field of X-ra y absorption in the dispersive mode. The achievement of an aberration-free horizontal focal spot of similar to 20 mu m FWHM has opened up unique possi bilities for performing X-ray absorption studies in extreme conditions of t emperature and pressure. The implementation of quarter wave plates has allo wed extremely accurate XMCD and nanosecond-resolved XMCD using the pump-pro be scheme to be recorded. However, the reduction of source size combined to the lengthening of beamlines have introduced new problems related to the m uch higher sensitivity to beam instabilities amplified by phase contrast ph enomena. Possibilities for the future have been investigated and shall be d iscussed.