Cavity Ring-Down Absorption of O in Air as a Temperature Sensor for an Open and a Cryogenic Optical Cavity.

The A-band of oxygen has been measured at low resolution at temperatures between 90 K and 373 K using the phase shift cavity ring down (PS-CRD) technique. For temperatures between 90 K and 295 K, the PS-CRD technique presented here involves an optical cavity attached to a cryostat. The static cell and mirrors of the optical cavity are all inside a vacuum chamber at the same temperature of the cryostat.

Phase shift cavity ring down and Fourier transform infrared measurements of C-H vibrational transitions, energy levels, and intensities of (CH3)3Si-C≡C-H.

Phase shift cavity ring down and Fourier transform IR techniques have been used to observe the C-H stretch fundamental and overtone absorptions of the acetylenic (Δυ = 1-5) and methyl (Δυ = 1-6) C-H bonds of trimethyl-silyl-acetylene [(CH3)3CSi≡CH] at 295 K. Harmonic frequencies ω(ν1), ω(a), and ω(s) and anharmonicities x(ν1), ω(a)x(a), ω(s)x(s) were calculated for the acetylenic, methyl out-of-plane, and methyl in-plane C-H bonds, respectively. The harmonically coupled anharmonic oscillator (HCAO) model was used to determine the overtone energy levels and assign the absorption bands to vibrational transitions of methyl C-H bonds.

Vibrational overtone spectroscopy, energy levels, and intensities of (CH3)3C-C≡C-H.

The vibrational overtone spectra of the acetylenic (Δυ = 4, 5) and methyl (Δυ = 5, 6) C-H stretch transitions of tert-butyl acetylene [(CH(3))(3)C-C≡C-H] were obtained using the phase shift cavity ring down (PS-CRD) technique at 295 K. The C-H stretch fundamental and overtone absorptions of the acetylenic (Δυ = 2 and 3) and methyl (Δυ = 2-4) C-H bonds have been obtained using a Fourier transform infrared and near-infrared spectrophotometer. Harmonic frequency ω(ν(1)) and anharmonicities x(ν(1)) and x(ν(1), ν(24)) are reported for the acetylenic C-H bond.

Cavity ring down and Fourier transform infrared spectroscopy at low temperatures (84-297 K): Fermi resonance and intensities of the C-H fundamental and overtone (Delta(upsilon) = 1-6) transitions of CHD(3).

The C-H stretch fundamental and overtone absorptions of CHD(3) have been obtained using Fourier transform infrared (FTIR), near-infrared, and phase shift and pulsed cavity ring down (CRD) techniques at temperatures between 84 and 297 K. The partially resolved rotational-vibrational spectra of CHD(3) that included the fundamental transition nu(1), the overtone transitions, and combination bands 5nu(1) and 4nu(1) + 2nu(5) and 6nu(1) and 5nu(1) + 2nu(5) were obtained and compared with the simulated spectra at the corresponding temperature. The strength of the Fermi resonance between levels upsilonnu(1) and (upsilon - 1)nu(1) + 2nu(5) with upsilon = 2-6 was calculated using the experimental perturbed energies and relative peak intensities.