Photodissociation dynamics of water in the second absorption band: vibrational excitation of OH(A2Σ)

Communication: State-to-state differential cross sections for H2O($\tilde B$B̃) photodissociation

“…[21][22][23][24][25] Due to the large torque along the dissociation path, the OH(X) fragment formed via non-adiabatic transitions was found to be rotationally excited, in agreement with experimental observations. These conclusions were confirmed by a later wavepacket study on three-dimensional PESs by van Harrevelt and van Hemert, 27, 31 who reported not only the absorption spectrum, but also ro-vibrational distributions of the OH fragments as well as the electronic branching ratio.…”

“…For this reason, it has attracted intense experimental [9][10][11][12][13][14][15][16][17][18][19] and theoretical attention. 14,[20][21][22][23][24][25][26][27][28] The photodissociation of H 2 O in its B band is initiated by photoexcitation from its ground (X 1 A ) state to its second excited state (B 1 A ). The earlier studies on the potential energy surfaces (PESs) established the existence of two conical intersections (CIs) between the two electronic states, which facilitate dissociation into both the H + OH(X) and H + OH(A) channels.…”

Photodissociation of water. II. Wave packet calculations for the photofragmentation of H2O and D2O in the B̃ band

“…Several approximate twoand three-dimensional dynamical calculations, using either the adiabatic or the diabatic potential energy surfaces, have been reported. 8,9,19,[21][22][23][24][25] Whereas these studies have successfully explained the rotational distributions of OH(X 2 ⌸) and OH(A 2 ⌺ ϩ ), the calculated absorption spectra are not in satisfactory agreement with experiment, 12 and the relative fractions for different products OH(X), OH(A), H 2 ϩO( 1 D), and O( 3 P)ϩHϩH, have not yet been studied. A nonadiabatic treatment including all three internal coordinates is crucial to obtain even only qualitative agreement with experiments.…”

“…The experimental data do not give evidence for fluctuations in the vibrational distribution as a function of the energy, which is probably because of the averaging over many rotational states. The results of the calculations of Heumann et al 25 are very different: they found much less vibrational excitation, and a slow increase of the population of vibrational excited states with increasing energy.…”

Quantum Mechanical Studies of Photodissociation Dynamics Using Accurate Global Potential Energy Surfaces

“…71 Theoretical descriptions of the dissociation of water in the second absorption band have gradually improved over the past two decades. In the earliest calculations, merely theB-state PES was taken into account, [74][75][76][77] and the potential surfaces were not of high quality. Weide and Schinke 75 presented an ultra-simple model to include theB →X transition near collinear geometries: When the trajectory reached linearity, it was continued either on the upper or on the lower state.…”