PHOTODISSOCIATION DYNAMICS IN QUANTUM STATE-SELECTED CLUSTERS - A TEST OF THE ONE-ATOM CAGE EFFECT IN AR-H2O

High resolution IR overtone pumping with an injection seeded optical p arametric oscillator (OPO) is used in conjunction with excimer laser p hotolysis to investigate the state-resolved dynamics of quantum state- selected van der Waals clusters in a slit supersonic expansion. The na rrow band IR light source (160 MHz, 5 mJ) preselects a specific upper state via the internal rotor band of Ar-H2O which correlates to the \0 3](-)<--\00](+),0(00)<--1(01) transition in H2O monomer. At fixed UV p hotolysis and probe wavelength, scanning the high resolution OPO yield s the \03](-)<--\00](+),Sigma(0(00))<--Sigma(1(01)) overtone action sp ectrum of Ar-H2O complexes. Conversely, at fixed IR pump wavelength, t he state distribution of the OH photoproduct from photolysis of quantu m state selected Ar-H2O clusters can be probed by laser induced fluore scence on the A (2) Sigma(+)<--X(2)II(0,0) band. The OH distributions from H2O monomer vs Ar-H2O photolysis from the same internal rotor sta te are remarkably similar, though significant anomalies are observed f or specific K rotational levels.