Dependence of the absorption coefficient of vibration-rotation transitions of dipole molecules on the resonance radiation polarization

The dependence of the absorption coefficient for vibration-rotation transitions in CO2 and H2O on ruby-laser pulse intensity and polarization is investigated experimentally using photoacoustic spectroscopy. For linearly polarized radiation, a decrease in absorption is found to occur as the intensity is increased. For circularly polarized radiation, no decrease is observed, even at significantly higher intensity. Possible mechanisms for the nonlinear absorption of dipole-molecule gases are discussed.