Laser spectroscopy of carbon-carbon-oxygen and jet spectroscopy of isotopomers of helium-carbonyl sulfide and higher clusters

The work of this thesis includes two separate studies using tunable diode laser spectroscopy. The first was to create and study radicals, in particular C2O molecules using a hollow cathode discharge. A pulsed supersonic jet expansion used to produce weakly-bound van der Waals OCS-He complexes was the subject of the second project.; Seven rotationally resolved infrared bands in the C-C and in the C-O stretching regions of the C2O radical were measured. This includes the observation of the nu3, 2nu3 - nu3, 3nu3 - 2nu3 bands of the X˜˜ 3Sigma- state and of the nu 3 band of the a 1Delta state in the C-C stretching region. Moreover, the (nu1 + 2nu 3) - 2nu3 and (2nu1 + nu3) - (nu1 + nu3) hot bands of the C-O stretching region were observed. The C2O radical was produced using a flowing mixture of carbon suboxide and helium subjected to a hollow-cathode discharge. The spectra were recorded using a diode laser spectrometer. The measurements of these bands together with previously reported frequencies in the C-O stretching regions11, 12, 16 were analysed to determine the most comprehensive harmonic frequencies and anharmonicity constants.; Infrared spectra of the OCS-He van der Waals complex and of OCS-He N clusters were studied in the region of the OCS nu 1 fundamental band using a tunable diode laser and a pulsed supersonic slit jet. For the complex, the spectrum of the normal isotope, 16O 12C32S-4He was considerably extended and the 34S- and 13C-substituted forms were recorded for the first time. The data could be analyzed satisfactorily using a conventional asymmetric rotor Hamiltonian with sextic centrifugal distortion terms. For the higher clusters, the 34S and 13C substituted forms were observed and assigned for N = 2 to 7, including some transitions with higher J-values than previously reported for the normal isotope, e.g. R(5). The observed vibrational shifts, relative to the free OCS molecule, were very similar to those of the normal isotope, with most of the difference explained by simple scaling. These results constitute a subtle and precise probe of intermolecular forces and dynamical effects in a system which is of current interest for cluster studies.; The C2O radical and the He-OCS complex represent two examples by which the powerful tools of high resolution spectroscopy may be used to explore microworld of atoms and molecules. It also illustrates the utility of the optical spectra to extract information about structure, energy levels, electric and magnetic properties of atomic and molecular systems.