Ultrafast spectroscopic interrogation and simulation of excited states and reactive surfaces

UnrestrictedMaking a movie of a chemical reaction requires intricate knowledge of both the chemical actors and the environment. Furthermore, the subtleties of the reactive surfaces and the effect of external forces such as solvent electrostatics and molecular collisions on these surfaces often play a major role in the reaction outcome. Many of these external effects begin influencing the reaction within tens of femtoseconds, requiring sophisticated experimental techniques in order to observe dynamics on these timescales.; Ultrafast pump-probe spectroscopy is employed to study the benchmark ICN Ã photodissociation reaction. This prototypical triatomic system is known to produce a highly non-equilibrium distribution of rotationally excited cyano radicals. The generation of these rotors comes from a non-adiabatic transition which applies extra torque to an already rapidly bending I-CN bond and leads to two product states corresponding to the I*(²P1/2) + cold CN and I(²P3/2) + hot CN channel. Simulations show that this rotationally excited CN pushes solvent molecules out of the way to create a cavity where free rotation takes place for several picoseconds. Our hypothesis is that this spinning CN resembles a gas phase molecule, and thus should have a gas phase spectral signature.; Although the relaxation of the hot CN takes place on relatively long time scales for ultrafast spectroscopists, the initial curve crossing event takes place much earlier (