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ABSTRACT: Positions, intensities, self-broadened widths, and collisional narrowing coefficients of the oxygen isotopologues 16O18O, 16O17O, 17O18O, and 18O18O have been measured for the b1Σg + ← X3Σg − (0,0) band using frequency-stabilized cavity ring-down spectroscopy. Line positions of 156 P-branch transitions were referenced against the hyperfine components of the 39K D1 (4s 2S1/2 → 4p 2P1/2) and D2 (4s 2S1/2 → 4p 2P3/2) transitions, yielding precisions of 0.00005 cm−1 and absolute accuracies of 0.00030 cm−1 or better. New excited b1Σg + state molecular constants are reported for all four isotopologues. The measured line intensities of the 16O18O isotopologue are within 2% of the values currently assumed in molecular databases. However, the line intensities of the 16O17O isotopologue show a systematic, J-dependent offset between our results and the databases. Self-broadening half-widths for the various isotopologues are internally consistent to within 2%. This is the first comprehensive study of the line intensities and shapes for the 17O18O or 18O2 isotopologues of the b1Σg + ← X3Σg − (0,0) band of O2. The 16O2, 16O18O, and 16O17O line parameters for the oxygen A-band have been extensively revised in the HITRAN 2008 database using results from the present study.
11/2009;
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ABSTRACT: Frequencies for 32 P-branch transitions of the O2A-band (b1Σg+←X3Σu-) were measured between 12975 and 13115cm−1 using the frequency-stabilized cavity ring-down spectrometer located at National Institute of Standards and Technology, Gaithersburg, MD. Absolute line positions were calibrated using the hyperfine components of 39K D1 and D2 atomic transitions yielding uncertainties
Journal of Molecular Spectroscopy - J MOL SPECTROSC. 01/2008; 251(1):27-37.
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ABSTRACT: Line intensities, self- and air-broadened linewidths, pressure-induced shifts, and collisional narrowing coefficients were measured from 2 ⩽ J′ ⩽ 32 in the P branch of the O2A-band (12 975–13110 cm−1) utilizing Galatry line profiles. Spectra were recorded using the frequency-stabilized cavity ring-down spectrometer located at NIST, Gaithersburg, MD with a spectral resolution <0.0001 cm−1 and noise-equivalent absorption coefficient of 6 × 10−8 m−1 Hz−1/2. Line intensities, obtained from calibrated gas samples for 2 ⩽ J′ ⩽ 32, are ∼1% lower than the values in current spectroscopic databases. At higher J (18 ⩽ J′ ⩽ 32), the measured air- and self- broadened half widths are up to 20% lower than the extrapolated values given in HITRAN 2004, while corresponding half-widths for 2 ⩽ J′ ⩽ 15 are in better agreement. Available self-broadened half widths are fitted to empirical expressions with an rms of 0.8%. We discuss the implications of our results for accurate remote sensing of surface pressure and photon path length distributions.
Journal of Molecular Spectroscopy.
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ABSTRACT: Frequencies for 32 P-branch transitions of the O2 A-band (b1Σ+g ← Χ3Σ-u) were measured between 12975 and 13115 cm^−1 using the frequency-stabilized cavity ring-down spectrometer located at National Institute of Standards and Technology, Gaithersburg, MD. Absolute line positions were calibrated using the hyperfine components of 39K D1 and D2 atomic transitions yielding uncertainties <1 MHz (~3 × 10^−5 cm^−1). Spectroscopic parameters for the b1Σ+g(ν=0) state were calculated and compared with previously determined values. These new transition frequencies should serve as a convenient secondary calibration standard in the 760 nm region.
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ABSTRACT: We describe a high-precision method for measuring pressure shifting of absorption lines. The technique involves the acquisition of high-resolution spectra using a cavity ring-down spectrometer whose length is continuously locked to a frequency-stabilized reference laser over a range of sample pressures. We discuss a relatively large correction arising from the pressure-dependence of dispersion in the cavity modes, and we demonstrate pressure shifting measurements in air for transitions in the 16O2A-band. Pressure shifts in the range -0.011 to are reported. We measured relative positions of line centers to within 70 kHz and determined pressure shifting coefficients over a 5 kPa pressure range with relative uncertainties approximately equal to 1.0%, which constitutes a five-fold improvement over previous measurements.
Journal of Quantitative Spectroscopy and Radiative Transfer.
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ABSTRACT: Positions, intensities, self-broadened widths, and collisional narrowing coefficients of the oxygen isotopologues ^(16)O^(18)O, ^(16)O^(17)O, ^(17)O^(18)O, and ^(18)O^(18)O have been measured for the b^(1)Σg + ← X^(3)Σg − (0,0) band using frequency-stabilized cavity ring-down spectroscopy. Line positions of 156 P-branch transitions were referenced against the hyperfine components of the ^(39)K D_1 (4s ^(2)S_(1/2) → 4p ^(2)P_(1/2)) and D_2 (4s ^(2)S_(1/2) → 4p ^(2)P_(3/2)) transitions, yielding precisions of ~0.00005 cm^(−1) and absolute accuracies of 0.00030 cm^(−1) or better. New excited b^(1)Σg + state molecular constants are reported for all four isotopologues. The measured line intensities of the ^(16)O^(18)O isotopologue are within 2% of the values currently assumed in molecular databases. However, the line intensities of the ^(16)O^(17)O isotopologue show a systematic, J-dependent offset between our results and the databases. Self-broadening half-widths for the various isotopologues are internally consistent to within 2%. This is the first comprehensive study of the line intensities and shapes for the ^(17)O^(18)O or ^(18)O_2 isotopologues of the b^(1)Σg + ← X^(3)Σg − (0,0) band of O_2. The ^(16)O_2, ^(16)O^(18)O, and ^(16)O^(17)O line parameters for the oxygen A-band have been extensively revised in the HITRAN 2008 database using results from the present study.
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ABSTRACT: Frequencies for 32 P-branch transitions of the O2A-band were measured between 12 975 and 13 115 cm−1 using the frequency-stabilized cavity ring-down spectrometer located at National Institute of Standards and Technology, Gaithersburg, MD. Absolute line positions were calibrated using the hyperfine components of 39K D1 and D2 atomic transitions yielding uncertainties <1 MHz (∼3 × 10−5 cm−1). Spectroscopic parameters for the state were calculated and compared with previously determined values. These new transition frequencies should serve as a convenient secondary calibration standard in the 760 nm region.
Journal of Molecular Spectroscopy.
