Femtosecond time-resolved X-ray diffraction from laser-heated organic films

The extension of time-resolved X-ray diffraction to the subpicosecond domain is an important challenge, as the nature of chemical reactions and phase transitions is determined by atomic motions on these timescales. Physicists in France are carrying out X-ray diffraction studies on the millionth of a billionth of a second-femtosecond-timescale [Nature, 390, 490 (1997)], following angstrom-level atomic disordering in an organometallic film. They follow the response of a Langmuir-Blodgett multilayers film of cadminum arachidate to laser heating by observing changes in the intensity of one Bragg peak for different delays between the perturbing optical pulse and the X-ray probe pulse. C. Rischel and A. Rousse are viewing fast atomic motion - which ultimately drives processes like chemical reactions and phase transformations - on the timescale at which it occurs.

One day it may be possible to watch movies of evolving molecular structures one frame at a time.