Ultrashort Electron Pulses

Abstract

Abstract : The focus of our research is the generation of ultrashort electron pulses, and their application to time-resolved pump-probe diffraction experiments. Our diffractometer utilizes a pulsed electron source that delivers subpicosecond electron pulses. This new instrument is applied to pump-probe experiments probing molecular structures in excited states. The short duration of the laser and the electron pulses allow time-resolved experiments that follow molecular rearrangements in real time. During the funding period, significant progress has been made toward the goal of observing time resolved structures. On the experimental side, we have built a new diffractometer designed to operate with the ultrashort electron pulses. We were able to observe high quality diffraction patterns with short exposure times (seconds, rather than hours with conventional photographic plates). First test runs on pump-probe diffraction images have been performed. On the theoretical side, we continued our investigations into the observability of wave functions, and extended the theory to vibrational wave functions of diatomic and triatomic molecules. We found that the diffraction signatures of vibrational wave functions are observable with our experiment, in spite of obstacles such as orientational averaging. This opens up the opportunity to image vibrational wave functions during chemical reactions.