Multiphoton excitation ionization of N-2 following collisional energy transfer with H2O: A potential measure of molecular mixing

摘要

A multiphoton ionization excitation of N-2 following collisional energy exchange with optically excited H2O was demonstrated, and its potential for measuring H2O-N-2 mixing at the molecular level was evaluated. In this process, N-2 is sensitized by a collisional energy exchange with H2O molecules excited by a tunable KrF laser. The sensitized N-2 molecules are further excited and ionized by two additional photons of the same laser pulse. Independent images of sensitized N-2(+) emission at 391.4 nm and by OH at 308 nm formed by the dissociation of excited H2O were obtained along a laser beam traversing slow dry-air and N,jets entering room air. Although effects of O-2 and N-2 collisional quenching were noted, such images can potentially be used to measure H2O-N-2 molecular mixing and the concentration of H2O independently. The detection of H2O nucleation by this technique suggests that imaging of H2O droplet evaporation or visualizing and monitoring H2O condensation may also be possible. (C) 1997 Optical Society of America.