Wave packet calculations for H₂+H₂ collisions: isotopic substitution effects

Abstract

Isotopic substitution effects for H₂(v ₁ = high)+H₂(v ₂ = low) collisions are studied by means of time-dependent wave packet calculations. A three degree-of-freedom reduced dimensionality model was employed, which can account for collision-induced dissociation as well as for four centre exchange processes, for reactants in selected vibrational states. Mass effects are studied in two ways: by substituting the collider H₂(v ₂=low) by D₂ in the same vibrational state, or by substituting the target H₂(v ₁ = high) by D₂ in a state with a similar vibrational energy. For the collider in its ground vibrational state, we have found that four centre probability profiles are quite similar but, conversely, thresholds for dissociation probabilities are quite different for the different mass combinations. The H₂(v ₁ = high)+D₂(v ₂ = low) combination was found to be the most effective one for the dissociation process. In addition, the process of dissociation of the vibrationally cold diatom was found to be quite important in H₂(v ₁=14) + D₂(v ₂=1,2) collisions. These effects are analysed by means of plots of the potential energy surface using mass-scaled coordinates.

Notes

This work is dedicated to the loving memory of Daniela di Domenico, the bright young woman who carried out most of this work and sadly died in recent times.

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Notes on contributors

Daniela Di Domenico †

This work is dedicated to the loving memory of Daniela di Domenico, the bright young woman who carried out most of this work and sadly died in recent times.