Peter M. Weber: Watching ‘Chemistry’ - Molecular Motions in Space and Time
Department of Chemistry, Brown University, Providence, RI 02912 USA
Molecules can display a fascinatingly complex array of dynamical motions, giving rise to a multitude of chemical reactions and functional properties. Two new highly time-resolved methods have been developed to track molecules as they perform their intricate structural motions: a gas-phase x-ray diffraction experiment uses the ultrashort x-ray pulses from SLAC’s Linac Coherent Light Source to record time-dependent scattering signals that can be analyzed to yield the time-dependent molecular structures, i.e. a ‘molecular movie’. And time-resolved photoionization through Rydberg states provides a structural-spectroscopic view that is complementary to the scattering picture. The methods are used to explore and illustrate different types of molecular reaction dynamics phenomena: direct dissociations along repulsive surfaces; photochemically induced electrocyclic ring opening reactions; conformeric motions in tertiary amines; charge delocalization phenomena; and coherent motions and dephasing of wavepackets in polyatomic systems.