Infrared laser absorption spectroscopy of jet -cooled biomolecules and water clusters

Both high- and low-resolution infrared laser spectroscopy techniques have been used to measure the vibrational and rovibrational spectra of nucleotide bases and water clusters entrained in molecular beams. Infrared Cavity Ringdown Laser Absorption Spectroscopy (IR-CRLAS) has been used to characterize the vibrationally resolved N-H stretching region of three nucleotide base monomers, adenine, thymine, and uracil, as well as clusters of uracil and thymine with themselves and with water. Infrared Tunable Diode Laser Spectroscopy (IR-TDLS) has been used to measure the first rotationally resolved vibrational spectrum of gas phase uracil monomer. Analysis of this spectroscopic data has provided confirmation that the dominant gas phase tautomeric structure of uracil is the diketo form. A novel new heated pulsed molecular beam source has also been developed to enable the vaporization of these solid samples without decomposition.;Terahertz Vibration-Rotation-Tunneling (VRT) Spectroscopy has been used to measure three new bands of the perdeuterated water pentamer in the 1.5 to 2 THz region. Detailed analysis of the water pentamer spectroscopic data has revealed linear Coriolis perturbations in two of the bands, and has helped to clarify the pseudorotational manifold of this cluster. In agreement with previous observations of the perdeuterated water pentamer, these three bands did not demonstrate any fine spectral splitting within individual rovibrational transitions, which would evidence possible hydrogen bond network rerrangement (HBNR) dynamics. Facilitating the measurement of this data was the use of a variable field Putley-mode (VFP) InSb photoconductive detector, which, through adjusting the cyclotron current in a superconducting solenoid, may be tuned over a range of 70 cm-1 in the 1.5 THz region. In addition, the possible observation of a rovibrational band of the cubic h16-water octamer is presented.