DIODE LASER SPECTROSCOPY OF Q-BRANCHES AT $662-661 cm^{-1}$, OF $CO_{2}$ ENCRICHED IN $^{18}O$ AND $^{17}O$
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Date
1979
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Ohio State University
Abstract
Measurements have been made of the absorption of the absorption of $CO_{2}$ samples enriched in 18O and 17O by tunable diode lasers in the wave number region 662.2-$666.1 cm^{-1}$. The fundamental Q-branches of the $^{16}O^{12}C^{18}O, ^{16}O^{12}C^{17}O$ and $^{17}O^{12}C^{17}O$ molecules are well resolved, together with ``hot’’ Q branches and various R and P branch lines of other isotopic species; notably $^{18}O^{12}C^{18}$ and $^{17}O^{12}C^{18}O$. The molecular constants for the Q-branch $01^{1}0 \leftarrow 00^{0}0$ of $^{16}O^{12}C^{18}O$ have been calculated by a least mean square fit to lines j=1 to 16 to be: $\nu_{o}=662.3717 \pm 0.0003\ cm^{-1}$, $\Delta B=9.65 + 0.02 \times 10^{-4} cm^{-1}$ where $\nu_{o}$ has been fixed in absolute magnitude by assuming the $^{16}O^{12}C^{16}O$ line, $02^{2}0 \leftarrow 01^{10}$ P7, as a reference standard at $662.325 cm^{-1}$. More accurate values for $\Delta B$ and $\Delta D$ can be obtained by using the separation between several R lines and adjacent Q lines, and the known positions of the R lines relative to the origin to obtain: $\Delta B=9.685 \pm 0.002 \times 10^{-4} cm^{-1}$ and $\Delta D=2.2 \pm 0.1 \times 10^{-9} cm^{-1}$. Other molecular constant can be determined with highest precision by using low J, R and P branch lines as calibration standards, together with etalon spacing. The calculated line positions of the fundamental Q branch can be used as secondary standards to fit the hot bands.
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Author Institution: Applied Photochemistry Division, Los Alamos Scientific Laboratory, University of California; Molecular Physics Building, Institute for Physical Science and Technology, University of Maryland