Inelastic collisions in para-H2: Translation-rotation state-to-state rate coefficients and cross sections at low temperature and energy.

We report an experimental determination of the k00→02 rate coefficient for inelastic H2:H2 collisions in the temperature range from 2 to 110 K based on Raman spectroscopy data in supersonic expansions of para-H2. For this purpose a more accurate method for inverting the master equation of rotational populations is presented. The procedure permits us to reduce the measured k00→02 rate coefficient to the corresponding σ00→02 cross section in the range of precollisional energy from 360 to 600 cm-1. Numerical calculations of σ00→02 carried out in the frame of the coupled channel method are also reported for different intermolecular potentials of H2. A good agreement is found between the experimental cross section and the numerical one derived from Diep and Johnson’s potential [J. Chem. Phys. 112, 4465 (2000)]. [ABSTRACT FROM AUTHOR]