Molecular and Electronic Dynamics in Van Der Waals Cluster Spectroscopy, Hydrogen Abstraction Reactions, and Inelastic Collisions at Liquid Surfaces

Quantum mechanical measurements are essential for an understanding of collision and reaction dynamics on the molecular scale. To this end, laser induced fluorescence (LIF) is used to probe rotational, vibrational, and electronic product state distributions following various chemical events. For example, LIF on the hydroxyl radical is employed to examine the propensity to populate different levels of OH following photolysis of H2O molecules using a technique known as vibrationally mediated dissociation (VMD). VMD is also used as an indirect method for obtaining infrared spectra of water clusters (Ar-H2O, H2O-H2O, and H2-H2O), weakly bound species which are produced in the cold ( ~ 5 K) environment of a slit supersonic expansion. Peaks are then assigned with the aid of high level theoretical calculations. LIF is also performed to study systems where reactive precursors produce OH/OD radicals (F + D2O \u26rarr DF + OD and F + H2O \u26rarr HF + OH) as well as for nonreactive processes where ground state NO inelastically is scattered from liquid Ga metal or room temperature ionic liquid (RTIL) surfaces. In the reactive scattering experiments, careful examination of OH product spin-orbit branching provides an opportunity to quantify the degree of multiple surface behavior in these systems. Rotational-state-resolved scattering of nitric oxide from a molten metal provides an opportunity to directly observe thermal roughening of the liquid due to capillary wave excitations. Scattered NO electronic distributions, which are out of thermal equilibrium with rotation, are quite sensitive to surface temperature, a possible consequence of interactions with electron-hole pairs during the collision. Finally, NO is scattered from room temperature ionic liquid (RTIL) samples where branching between the two possible scattered spin orbit states (2\u26Pi2 and 2\u26Pi2) is found to be highly sensitive to surface heating and choice of ionic liquid. This may serve as a novel means for characterizing these surfaces, which are of technological interest due to their potential role as advanced solvents