INFRARED-SPECTRA OF RETARDED MOLECULAR OSCILLATOR

Theoretical interpretation is proposed for the inhomogeneous broadenin g of the infrared line shapes of high harmonics of hydrogen containing modes observed by the optoacoustic and thermal lensing spectroscopy i n the liquid phase of benzene and other organic transparent liquids. A ttention is focused on the experimental fact that both line width and asymmetry factors of the harmonic series increase linearly with the ha rmonic number for which fact no satisfactory theoretical understanding was still available. This interpretation is based on recently propose d new approach to separation of electronic and nuclear movements accou nting for the finite velocity of the pi electronic cloud of vicinal mo lecules and its retardation in following the protonic motion. This ret ardation leads to the time dependence of molecular oscillator which ma y be viewed as anharmonic. The experimental results concerning the lin ear increase in the line width and the asymmetry factor with increasin g order of the harmonic are well represented.