Effect of collisions on line profiles in the vibrational spectrum of molecular hydrogen

Abstract

A semiclassical calculation of density-broadening and line-shift coefficients in the vibrational-rotational spectrum of molecular hydrogen is presented. These parameters are obtained as functions of temperature and upper-state quantum numbers, and the calculated results are in good agreement with experimental values obtained from fundamental and overtone electric quadrupole spectra, except for the 4-0 overtone density-broadening coefficient. Results from Raman and electric-field-induced spectra in the fundamental band are also discussed. The calculation includes construction of an intermolecular potential for the ${\mathrm{H}}_2$-${\mathrm{H}}_2$ interaction. The vibrational phase shift resulting from collision is shown to account for the vibrational state dependence of the broadening and shift coefficients, and the observed temperature dependence of the line shift is reproduced by the calculation.