Broadening and shifting coefficients of Raman isotropic Q(j)(j=0,1,2) lines for pure H2: coupled states and semiclassical calculations.: Comparison with experiments Original Research Article

Quantum coupled states (CS) and semiclassical Robert–Bonamy (RB) calculations of pure H2 broadening and shifting coefficients of Q( j) rovibrational lines have been performed using a simple atom–atom potential energy surface (PES). The main interest is to test the validity of the semiclassical method versus the CS calculation. This is the first comparison of the two methods for a diatom–diatom system for which rotation–rotation (R–R) energy transfers contribute to the broadening and shifting coefficients. Agreement between the two methods is found acceptable on the total result, but is excellent when resonant or quasi-resonant rotational energy transfer do not occur. Comparison with experiment confirms the empirical laws used to model the temperature dependence of the broadening and shifting coefficients. It also permits us to analyze through the semiclassical model, the weakness and advantages of the atom–atom PES used.