Knowledge Bank

The shift and pressure broadening due to helium of the fundamental and overtones of certain of the $H2$ isotropic Raman, and quadrupole-absorption, vibration-rotation transitions were $obtained2$ via S-matrix elements which were computed using close-coupling and semi-classical techniques. S-matrix elements were computed using an ab initio system $potential1$ with the range in relative kinetic energies of $10-1000cm-1$ and up to fifty partial waves. The S-matrix elements were incorporated into a theoretical $expression2$ for the line shape which was thermally averaged to obtain results. The calculated isotropic Raman $Q1(1)$ line shift at room temperature is in excellent agreement with experiment. The results of these calculations, along with very high resolution laboratory measurements to be done, should provide a stringent test of the potential surface.