Collisional perturbation of quantum regular and irregular intramolecular states: State-to-state study of a model

Abstract

Abstract State-to-state analysis is presented of collisional energy transfer in quantum-mechanical collinear collisions between an atom and a triatomic molecule. The molecular potential was that of Henon and Heiles, while the interaction was modelled by both a soft, exponential repulsive potential and a Morse potential. This analysis emphasizes how different categories of molecular states (normal mode, local mode, or mode mixed) are influenced by the collision perturbation. The discussion centers around plots showing the energy dependence of P ??? ( X ), the probability that initial state i ends up in category X , and contour maps of state-to-state transition probabilities, P ??? ( E ). For the exponential repulsive model, there is a resistance to alteration of the molecular energy; “horizontal” transitions occur within bands of quasi-resonant states. By way of contrast, the Morse interaction model exhibits many vertical transitions, with many low-intensity transitions to a large number of final states. The special role played by extreme motion states, emphasized in recent studies by Hose and Taylor, is discussed in relation to their survivability. Finally, these results are related to trends that we found earlier in the energy dependence of the average energy transfer.