Experimental investigation of infrared fluorescence of molecular gases under the action of CO₂-laser radiation

Abstract

In the paper, the experimental investigation is carried out of the IR fluorescence of organic substances of different classes in the range 600–3000 cm⁻¹ under the action of the continuous radiation of a CO₂ laser with a power of ∼40 W/cm². The procedure is given for obtaining the fluorescence spectra. For all the substances investigated, the magnitudes of the effective absorption cross section were determined experimentally at the generation frequency of the laser. Fluorescence is observed only in the case when σ_v ≠ 0; if σ_v ≃ 0, fluorescence is absent. It is shown that the fluorescence intensity depends significantly on the magnitude of the absorption cross section at the laser frequency. A comparison of the fluorescence and absorption spectra shows that only vibrations allowed in the IR region appear in the emission; in a number of cases, a sharp increase of the fluorescence intensity of certain overtones and compound vibrations is observed: when the frequencies are multiples of the laser emission.