We describe a high sensitivity and high spectral resolution laser absorption spectrometer based upon the frequency-stabilized cavity ring-down spectroscopy (FS-CRDS) technique. We used the Pound-Drever-Hall (PDH) method to lock the probe laser to the high-finesse ring-down cavity. We show that the concomitant narrowing of the probe laser line width leads to dramatically increased ring-down event acquisition rates (up to 14.3 kHz), improved spectrum signal-to-noise ratios for weak O(2) absorption spectra at λ = 687 nm and substantial increase in spectrum acquisition rates compared to implementations of FS-CRDS that do not incorporate high-bandwidth locking techniques. The minimum detectable absorption coefficient and the noise-equivalent absorption coefficient for the spectrometer are about 2×10(-10) cm(-1) and 7.5×10(-11) cm(-1)Hz(-1/2), respectively.
The carbon monoxide–water (c–w) cluster produced in an argon matrix at cryogenic temperatures has been reinvestigated by FTIR spectroscopy. In the 4.7 μm region, a line at 2149.4 cm−1 was assigned to the CO stretching mode of the CO–H2O 1–1 cluster. In the 2.7 μm region, two lines, at 3627.8 and 3723.5 cm−1, were assigned to the OH stretching modes of the CO–H2O 1–1 cluster. By the deuterium enriched experiment, the lines of the CO–D2O 1–1 cluster and the CO–HDO 1–1 cluster were identified for the CO stretching vibration and the OD stretching vibration. The tunnel splitting observed in gas phase has not been detected in the present study. Combining with the gas phase data the matrix shifts in the line positions were obtained precisely, with which we have predicted some band centers of the free complexes so far not reported in literature. Migration of trapped molecules, CO and H2O, in the argon matrix has been observed both by annealing and by high temperature deposition. The spectral behavior shows that CO can move at a lower temperature than H2O in the argon matrix.
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