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The photodissociation of H2O in the first absorption band is studied from single rotational states of vibrationally excited water. A tunable IR laser is used to prepare single rotational states in the asymmetric stretch mode. The subsequent photodissociation at 193 nm favors product formation from these single prepared states. The formation of the OH product in different rotational, Λ-doublet, and spin states is analyzed for a series of initial rotational states of H2O. This is the first direct photodissociation studied on a state to state level. The product state distributions depend sensitively upon the prepared state in the parent molecule H2O and exhibit pronounced quantum structure. The experimental results are understood almost quantitatively in terms of theory. The photodissociation of water turns out to be a limiting case of a dissociation which is governed by transfer of parent motion to products. The experiment leads to a highly improved understanding for the selective population of Λ-doublet states.

Photoexcitation is used to prepare species whose subsequent fragmentation can be exploited for the purposes of studying, controlling and manipulating different kinds of molecular processes. First, we show how a form of sub-Doppler resolution spectroscopy can be used to determine centre-ofmass kinetic energy distributions, thereby enabling internal energy distributions to be obtained for elementary processes which occur at a fixed total energy. We present data for H atoms monitored at the Lyman-a wavelength. Secondly, we show how such processes can be used to study binary interactions by preparing van der Waals complexes (e.g. C0,HBr

The development of a simultaneous on-line detector for metal species separated by effective molecular size is described. A new spray chamber to facilitate this analysis In relatively hlgh-volatllity organic solvents and to serve as the Interface between a liquid chromatography (LC) and an inductively coupled plasma atomic emission spectrometer (ICP-AES) is evaluated. Detection limits In toluence are comparable to those found in aqueous static operation of ICP-AES. The requirements of computer-based data output and examples of the output developed are presented. The LC-ICP Interface Is demonstrated by size separation of three synthetic mixtures. Two of the mixtures are Iron and silicon organometallic species with different ligands attached, while the third mixture consists of aproximately 20 different metals in essentially the same ligand environment.

The selective population of rotational, spin, and Λ-doublet states of OH(2Π,v=0,1) by inelastic collisions with H2 and D2 is investigated in two experiments. In the first experiment OH radicals are generated by photolysis inside a pulsed nozzle beam source and prepared in the ground state j=1.5, v=0, 2Π3/2 with equal amounts in both Λ-doublets by rotational cooling in the subsequent expansion. The collisional excitation of OH by the secondary beam is probed via laser-induced fluorescence selectively for the Λ-doublet states for the different rotational levels in both spin manifolds of v=0. Integral cross sections σ(j=1.5,Ω̄=1.5→j ′,Ω̄′,ε′) averaged over the Λ-doublet substates in the input channel, but Λ-doublet substate resolved in the output channel are obtained in this case. In contrast to some previous predictions the Π(A′) Λ-doublet substate is preferentially populated. This implies a population inversion in the Λ-doublets for 2Π1/2 and an anti-inversion for 2Π3/2, which rules out previously proposed pump mechanisms for astronomical OH masers. In the second experiment OH is generated also by photolysis, in this case however in a flow system. Single Λ-doublet states are prepared by infrared excitation of the thermally relaxed OH in 2Π3/2, v=1 for two rotational states (j=1.5,4.5). The redistribution in v=1 induced by collisions with H2 is probed by laser-induced fluorescence. Rate constants are obtained for transitions from the initially prepared Λ-doublet states to the other Λ-doublet of the same j and also for transitions to other rotational states.