Franck–Condon simulations of transition-state spectra for the OH + H₂O and OD + D₂O reactions

Abstract

We present the results of quantum wave packet calculations performed to analyze the experimental transition-state spectra for the OH + H2O and OD + D2O reactions based on photodetachment of...

Cryogenic Vibrationally Resolved Photoelectron Spectroscopy of OH–(H2O): Confirmation of Multidimensional Franck–Condon Simulation Results for the Transition State of the OH + H2O Reaction

“…27 Very recently, Sugiura and Takayanagi performed multidimensional Franck−Condon simulations for the photodetachment of OH − (H 2 O) to form • OH(H 2 O), obtained from fourdimensional quantum wave packet propagations, during which rich vibronic features were predicted. 29 Their simulations were based on the transition from the anionic structure B to the neutral transition state IV, both of which have C 2 symmetry, and are of similar geometry (cf. Figure 2 and Table 1).…”

“…Recently, Sugiura and Takayanagi conducted a groundbreaking Franck–Condon simulation on the photodetachment of OH – (H 2 O), in which four vibrational modes were explicitly taken into consideration . In their simulated spectrum, the strongest bands were due to the antisymmetric stretching of the H atom, while multiple transitions originating from other active modes and their combinations were present.…”

“…The argument of the existence of a neutral excited state was previously speculated to contribute to the rising tail near the photodetachment limit of 266 nm (4.661 eV) by Arnold et al 27 Recent ab initio calculations on the neutral radical • OH(H 2 O) at the MRCI +Q/aug-cc-pVTZ level predicted an excited state with a relative energy of 1.36 eV. 29 The predicted energy is outside the energy limit of the 266 nm photon that was used in the previous study, 27 and therefore their spectrum only recorded part of the rising edge of the transition to the neutral excited state. In contrast, our NIPE spectrum, recorded by using 193 nm (6.424 eV) photons, yields the whole band of this transition and shows excellent agreement between the observed VDE difference of 1.39 eV and the previously calculated relative energy of 1.36 eV.…”

“…27 In their study, the antisymmetric stretching mode of the H atom with a three-quanta vibrational progression was O), in which four vibrational modes were explicitly taken into consideration. 29 In their simulated spectrum, the strongest bands were due to the antisymmetric stretching of the H atom, while multiple transitions originating from other active modes and their combinations were present. When the line widths of each of the sticks in that simulation were broadened to match the experimental resolution, the simulated complex multiple transitions merged into three broad bands, 29 in qualitative accord with the previous spectra.…”

“…29 In their simulated spectrum, the strongest bands were due to the antisymmetric stretching of the H atom, while multiple transitions originating from other active modes and their combinations were present. When the line widths of each of the sticks in that simulation were broadened to match the experimental resolution, the simulated complex multiple transitions merged into three broad bands, 29 in qualitative accord with the previous spectra. 27,28 To further validate the results of the simulation by Sugiura and Takayanagi, an experimental TS NIPE spectrum obtained with higher resolution is required.…”