Semiclassical statistico-dynamical description of polyatomic photo-dissociations: State-resolved distributions

TL;DR

This paper introduces a novel quasi-classical method for analyzing polyatomic photo-dissociation processes, providing rovibrational resolution without binning, and demonstrates its effectiveness on ketene dissociation data.

Contribution

The paper presents an alternative, binning-free quasi-classical approach using inverse dynamics and angle-action variables for polyatomic dissociation analysis.

Findings

Accurate rovibrational distributions match experimental data

Method reduces computational effort by decreasing trajectory count

Provides a way to incorporate rotational structures into vibrational distributions

Abstract

An alternative methodology to investigate indirect polyatomic processes with quasi-classical trajectories is proposed, which effectively avoids any binning or weighting procedure while provides rovibrational resolution. Initial classical states are started in terms of angle-action variables to closely match the quantum experimental conditions and later transformed into Cartesian coordinates, following an algorithm very recently published [J. Chem. Phys. 130, 114103 (2009)]. Trajectories are then propagated using the 'association' picture, i.e. an inverse dynamics simulation in the spirit of the exit-channel corrected phase space theory of Hamilton and Brumer [J. Chem. Phys. 82, 595 (1985)], which is shown to be particularly convenient. Finally, an approximate quasi-classical formula is provided which under general conditions can be used to add possible rotational structures into the vibrationally-resolved quasi-classical distributions. To introduce the method and illustrate its capabilities, correlated translational energy distributions from recent experiments in the photo-dissociation of ketene at 308 nm [J. Chem. Phys. 124, 014303 (2006)] are investigated. Quite generally, the overall theoretical algorithm reduces the total number of trajectories to integrate and allows for fully theoretical predictions of experiments on polyatomics.