Khodakovsyy V. Spectral Effects in Interaction of Continuons Wave Dye Laser Radiation with Atoms and Molecules

The thesis is devoted to the studies of spectral effects which arise when the continuous wave dye laser is tuned in the vicinity of the strong absorption line of the intracavity atomic gas, and to the development of a method of fluorescence laser spectroscopy using the narrowband dye laser. The new technique for the measurement of the value of the frequency selective reduction of losses or the narrowband additional gain in the cavity of the broadband laser is developed and experimentally realized. It is shown, that in the dye laser with interference-closed output, frequency dependent lenslike properties of the intracavity absorbing medium cause the phenomenon of frequency-locking of laser radiation, and the spectral characteristics of this laser are determined by the intracavity interferometer. On the basis of the studies of the molecular fluorescence excitation spectra of iodine isotopes 127I129I and 127I2 the selectivity of the laser-fluorescence technique of 129I registration on the background of considerably larger concentration of the stable isotope 127I2 is found. The computer-based selection of absorption lines of 127I129I, which provide the maximum ratio of 127I129I fluorescence intensity to 127I2 background fluorescence intensity, is carried out. The ultimate sensitivity of the laser fluorescence technique of the isotope 129I detection amounts to 3·10-4. The main sensitivity limitation factors are the background 127I2 fluorescence and the fluctuation of the dye laser intensity. It is shown that already at relative 129I concentration about 0,25 % of 127I2 concentration the influence of pollution of a He-Ne/127I2 absorption cell by an isotope 129I on the laser frequency reproducibility is comparable with the influence of the all other known factors. To monitor the isotope 129I pollution of the iodine absorption cells, testing of cells using the laser fluorescence technique which provides the detection sensitivity of 129I at a level of 0,03 % is suggested.