Infrared Cavity Ringdown Laser Absorption Spectroscopy of jet -cooled clusters

Infrared Cavity Ringdown Laser Absorption Spectroscopy (IR-CRLAS) employing stimulated Raman scattering (SRS) of pulsed dye lasers as the tunable IR source has been developed. This technique allows highly sensitive (ca. 1 ppm fractional absorption) direct absorption measurements to be performed in the 2--8 mum spectral range with complete wavelength coverage. Basic CR-LAS principles and essential SRS theory are reviewed. IR-CRLAS spectrometers based on both a Raman shifted dye laser and a pulsed Alexandrite ring laser are described.;The IR-CRLAS spectrometer has been used in a comparative study of the O-H-stretching vibrations of small alcohol clusters. Results indicate an increase in the hydrogen bond strength as the alcohol chain length increases. An IR-CRLAS investigation of the aromatic C-H stretches of benzene and berizene/methane mixtures, performed in an effort to provide experimental support for a theoretically proposed "antihydrogen bond", produced negative results. Similarly, negative results from a visible CRLAS search for water cluster absorptions in connection with the anomalous atmospheric absorption of solar radiation are presented.;Infrared laser spectroscopic studies of the structures and bonding in jet-cooled carbon clusters are discussed. The measurement and analysis of a rovibrational band at 2074 cm-1, tentatively assigned to linear C10 is presented. The astrophysical significance of carbon clusters is also discussed in conjunction with the first detection of a non polar molecule (C3) in a cold interstellar dust forming region, performed using far-infrared heterodyne spectroscopy aboard the Kuiper Airborne Observatory.