Dr. Laurie Butler is supported by a Presidential Young investigator Grant form the Physical Chemistry Program to study photofragmentation of gas phase molecules which have been electronically excited with laser radiation. Dr. Butler is studying the rapid dipole-dipole induced transfer of electronic energy between two chromophores in a molecule. In particular, she is studying the nature of this energy transfer in 1,2-C2F4BrI fragmentation in which C-I and C-Br fission compete following initial excitation to the C-Br repulsive surface. This work is particularly important since, if this intramolecular energy transfer could be suppressed, one might conceive of selective excitation and fragmentation of individual bonds. Dr. Butler is also utilizing emission spectroscopy of dissociating molecules to study intersections between repulsive electronic states which alter the dissociation pathways of polyatomic molecules. Measurements made in Dr. Butler's laboratory provide detailed data on such nonadiabatic dissociations thus permitting the determination of internuclear separation, relative velocity, and electronic energy at the crossing as well as the time required to reach the crossing. Dr. Butler's research is addressing fundamental questions regarding the process by which an initial electronic excitation may result in specific dissociation channels among many energetically allowed ones. By measuring product velocities, internal energies, and angular distributions of products, she can directly address qustions regarding the redistribution of electronic energy produced by laser excitation.
