NEW OPPORTUNITIES FOR TIME-RESOLVED X-RAY-SCATTERING AT THE ESRF

This is a review of the temporal structure of the radiation from inser tion devices at the ESRF and its use for time resolved experiments on macromolecular crystals and liquids. The article presents single pulse Laue data from cutinase, a 22 kD lipolitic enzyme, wich show that Lau e patterns of high resolution can be acquired on three 170 ps pulses. The strongest reflections count up to 3 10(4)photons per pulse and the data were integrated to 1.5 Angstrom resolution. The possibility of u sing a monoharmonic undulator for Laue diffraction at higher resolutio n is looked into by means of calculations of the brilliance and bandwi dth. Finally the initiation of reactions in photo sensitive molecules is examined by calculations of the photodissociation process in the he me protein myoglobin dioxide (MbO(2)). The conclusion is the following : an organic crystal can only accept an ultra short laser pulse at lo w power densities. The concentration of photolysed unit cells is there fore low, which scales down the difference amplitude between the groun d and excited states. We suggest using stroboscopic accumulation techn iques to recover the needed precision.