Fully quantum study of vibrational energy transfer between H2 and D2

We present here the results of a detailed study of the collisional transfer of vibrational energy between H2 and D2. Following our work on D2–D2 collisions [J. Chem. Phys. 59, 6254 (1973)], we carry out a fully quantum treatment of the collision dynamics, assuming a collinear geometry. We have used one fully ab initio and four different model interaction potentials. For both the 10→01 and 11→02 processes, we find that the transition probabilities are extremely sensitive to the choice of potential surface. Another result is that nearest-atom model potentials yield inelastic probabilities which are too large. We further show that long-range forces play a far less important role in the case of these off-resonant processes than for the D2–D2 near-resonant collisions. Also of interest is the result that the calculated V–V transition probabilities are largely insensitive to the choice of a harmonic or Morse oscillator description of the colliding molecules.