Fully quantum study of near resonant D2--D2 vibrational energy transfer

We have carried out a detailed theoretical study of the 02–11 and 03–12 near-resonant vibrational energy transfer processes which can occur during the collision of two D2 molecules. Assuming a collinear geometry, we have solved the collision dynamics fully quantum-mechanically, using a modified version of the Gordon program. We have investigated three different model potentials and one full ab initio potential surface. Both at high and low collision energies, the V–V transition probabilities are extremely sensitive to the particular potential surface used. We further show that nearest-atom model potentials greatly overestimate transition probabilities at high energies. Also of interest is the result that at moderate to high energies near-resonant V–V transfer probabilities are largely insensitive to the choice of a harmonic or Morse oscillator description of the two colliding molecules. Finally we show that the simple two-state approximation appears to be remarkably accurate over a wide range of energies.