Multiphoton excitation ionization of N↓(2) following collisional energy transfer with H↓(2)O: a potential measure of molecular mixing

摘要

A multiphoton ionization excitation of N↓(2) following collisional energy exchange with optically excited H↓(2)O was demonstrated, and its potential for measuring H↓(2)O-N↓(2) mixing at the molecular level was evaluated. In this process, N↓(2) is sensitized by a collisional energy exchange with H↓(2)O 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 H↓(2)O were obtained along a laser beam traversing slow dry-air and N↓(2) jets entering room air. Although effects of O↓(2) and N↓(2) collisional quenching were noted, such images can potentially be used to measure H↓(2)O-N↓(2) molecular mixing and the concentration of H↓(2)O independently. The detection of H↓(2)O nucleation by this technique suggests that imaging of H↓(2)O droplet evaporation or visualizing and monitoring H↓(2)0 condensation may also be possible. # 1997 Optical Society of America