State-to-state vibrational excitation of I2 in collisions with H2 and D2

Abstract

We have measured the energy dependence of cross sections for I2 vibrational excitation in collisions with H2 and D2 over the kinetic energy range from threshold to about 0.46 eV for D2 and 0.29 eV for H2. D2 is generally less efficient than He in exciting I2, probably because of a softer repulsive wall in the effective interaction potential. An exception is the low-energy cross section for v=0→2 excitation, which might be enhanced for D2 collisions because of an accidental resonance in energy with the D2 ( j=4→2) rotational transition. The v=0→1 cross sections for H2 collisions show a sharp and as yet unexplained feature at an energy 0.014 eV above threshold.