Rotational energy transfer in collisions of internally excited molecules. Effect of initial conditions and potential energy surface

We report quasiclassical trajectory calculations for the effect of potential energy surface, initial vibrational state, and initial translational energy on cross sections for rotational energy transfer in nonreactive collisions. We also study whether the effect of initial vibrational excitation is different for systems that allow reaction from those that do not. The systems studied are Ar+HF, Ar+H₂, and H(D)+H₂ on a total of five potential energy surfaces. The most important trend is that if rotational-translational energy-transfer cross sections are small (<4α₀²) for the ground vibrational state, then they increase markedly upon vibrational excitation; but if they are large (20-110α₀²) for the ground vibrational state, then they change very little. We present tables of the state-to-state rotational energy cross sections to illustrate finer details of the trends.