Instrumentation for the study of jet-cooled molecules and spectroscopic investigation of low-frequency vibrations

For the past twenty years laser spectroscopists have utilized supersonic jet expansions in order to cool molecules to very low levels. This decreases the number of hot bands in the spectra resulting in a great degree of simplification of the data. Several techniques have been developed in order to study molecules under such cooled conditions. These include laser-induced fluorescence (LIF), single vibronic level fluorescence (SVLF), laser-induced phosphorescence (LIP) and resonance enhanced multiphoton ionization (REMPI) using time of flight mass spectroscopy for detection. A new apparatus for the measurement of these phenomena has been constructed and it has been utilized to record various spectra thereby demonstrating its utility.; In addition, the high-temperature vapor-phase Raman spectra of 9,10-dihydroanthracene has been recorded along with infrared results. There has been some controversy as to whether this molecule possesses a planar (D2h) or bent (C2v) structure in its ground state. A vibrational analysis using principles of symmetry has demonstrated that the molecule does exhibit a bent structure in its ground state.