High resolution dye laser photoacoustic spectroscopy of visible wavelength vibrational-rotational transitions in molecules important to the study of planetary atmospheres

The study of planetary atmospheres requires the use of laboratory data in order to interpret properly the astronomical observations that have been made. Methane, ammonia, and deuterium hydride are all known to be present in the outer planets of our solar system. This thesis describes the acquisition of spectra for these molecules under conditions which are appropriate for use in modeling the atmospheres of the outer planets. Spectroscopic measurements for methane, ammonia, and deuterium hydride were obtained using a computer-controlled ring dye laser and a variable-temperature cryogenic photoacoustic detector both constructed in this laboratory. All spectra have been acquired at a spectral resolution sufficient to reproduce the line profiles with minimal distortion. The Voigt function was fit to each methane and ammonia line profile and the Galatry function was fit to all HF line profiles. Pressure broadening coefficients were determined from these least squares fits. Pressure broadening coefficients have been obtained from isolated methane lines at 6196.83 A in the 6190 A band and at 6818.84 A in the 6825 A band. Methane, nitrogen, hydrogen, and helium were all used as broadening gases