POTENTIAL-ENERGY SURFACE FOR NO-HE SYSTEM FROM THE STATE-TO-STATE RATE COEFFICIENTS

The rotationally inelastic collisions in NO - He system have been stud ied to investigate the problem of determination of the potential energ y surface from the experimental state-to-state rate coefficients. By c omparing the computed cross sections with the available experimental d ata the appropriateness of different forms and parameters of the inter molecular potentials has been explored. It is found that the pairwise Lennard-Jones potential is capable of explaining the propensity for ev en transitions in such heteronuclear diatomic molecule having atoms of nearly equal mass. It is also observed that such pairwise potential i s far better than a potential which is expressible by a product of Len nard-Jones potential as a radial term and a linear combination of Lege ndre polynomials as the angular term. The pairwise Lennard-Jones poten tial having the values of its parameters in the reasonable range is, h owever, found to be insufficient to account for the experimental rotat ional inelasticity. It is seen that a further improvement in the poten tial can be achieved by making the parameters of the pairwise Lennard- Jones potential angle dependent.