Robert A. Toth

Molecular line parameters for the atmospheric trace molecule spectroscopy experiment

During its first mission in 1985 onboard Spacelab 3, the ATMOS (atmospheric trace molecule spectroscopy) instrument, a high speed Fourier transform spectrometer, produced a large number of high resolution infrared solar absorption spectra recorded in the occultation mode. The analysis and interpretation of these data in terms of composition, chemistry, and dynamics of the earths upper atmosphere required good knowledge of the molecular line parameters for those species giving rise to the absorptions in the atmospheric spectra. This paper describes the spectroscopic line parameter database compiled for the ATMOS experiment and referenced in other papers describing ATMOS results. With over 400,000 entries, the linelist catalogs parameters of 46 minor and trace species in the 1–10,000-cm−1 region.

Lines intensities of the CO2 Σ-Σ bands in the 1.43–1.65 μ region☆

Abstract The line intensities of the five Σ-Σ bands of CO 2 in the 1.43–1.65 μ region have been measured with relatively low sample pressures and high resolution (0.035–0.06 cm −1 ). The data are analyzed to obtain the total band intensities and dipole-moment matrix elements. At 296°K the intensity of the 3 ν 3 band is found to be 3.62 × 10 −2 cm −2 atm −1 . The intensities of four bands in the Fermitetrad in order of increasing frequency are 1.15 × 10 −3 , 1.14 × 10 −2 , 1.12 × 10 −2 , and 1.27 × 10 −3 cm −2 atm −1 at 296°K.

Wavenumbers, strengths, and self-broadened widths of CO2 at 3 μm☆

Abstract Measurements of the line strengths of the 13 1 0-00 0 0 and 14 2 0−01 1 0 bands of CO 2 have been made with high resolution. The line strengths in both bands are strongly perturbed by Coriolis interactions resulting in the R -branch strengths being, on the average, greater than the P -branch strengths for comparable values of J ″. Measurements of the Q -branch strength of the 13 1 0-00 0 0 band were also made. The strength data were analyzed to determine the vibrational-band strengths and the coefficient, ξ, of the F factor. Line-center frequencies of the 14 2 0−01 1 0 band were measured and used to determine the band-center frequency and the rotational constants. From these data, the following constants were determined for the 14 2 0 state in cm −1 : ν 0 =3340.521±0.007 , B c =0.391433±0.000004 , B d =0.391450±0.000004 , D c =D d 14.8±0.2 × 10 −s . The direct method was applied to determine the self-broadened line widths in the 13 1 0-00 0 0 band. There is good agreement between this work and the linewidth values given by Yamamoto, Tanaka, and Aoki.

Linewidths of HCl broadened by CO2 and N2 and CO broadened by CO2

Abstract High resolution measurement of the linewidths of HCl broadened by CO 2 and N 2 and CO broadened by CO 2 have been performed in both the 1-0 and 2-0 bands of HCl and the 2-0 band of CO. The data were analyzed by the direct and the peak absorption methods. Values of the linewidths obtained by the two methods are in good agreement. For | m | ≤ 3, for the case of HCl + CO 2 , the agreement is good for the values obtained in both bands of HCl. However for | m | > 3, the HCl + CO 2 linewidths in the 1-0 band are smaller than the corresponding lines in the 2-0 band by as much as 11% for | m | = 9. Lines (| m | ≤ 3) of the 1-0 and 2-0 bands of HCl broadened by CO 2 were also analyzed in terms of the super-Lorentzian line profile proposed by Varanasi, S. K. Sarangi, and G. D. T. Tejwani ( J. Quan. Spectr. Radiative Transfer 12 , 857 (1972)) and the Lorentzian profile. The results indicate that near the line center (within 3γ), the shape of HCl + CO 2 lines are Lorentzian.

Line assignments and intensities for the ν3 + ν4 − ν4 band of 12CH4

Abstract Assignments and Intensities are reported for 886 lines arising from the “hot-band” ν3 + ν4 − ν4 of 12CH4 at 3.3 μm. These are determined from spectra at 0.01–0.02 cm−1 resolution that include intensity measurements at reduced temperatures. Energy levels for the v4 = 1 state through J = 12 are also given based on the ν3 + ν4 band assignments of Hunt et al., and the wavenumbers of the hot-band lines.

Line strengths of H2O and N2O in the 1900 cm−1 region

Abstract Measurements of line strengths of water vapor and nitrous oxide in the 1900 cm−1 region have been made with moderate spectral resolution (∼0.15 cm−1). The H2O values are, on the average, 5.5 percent (standard deviation of ±10 percent) smaller than the calculated line strengths given by Benedict and Calfee. The N2O measurements were made of the Q-branch strength and the P- and R-branch line strengths of the ν 1 + ν 2 1 band. The N2O data were analyzed to obtain the vibrational band strength and the coefficient, ξ, of the F factor, from which the following constants were determined: ∑ P 1 Q,R S = 0.437±0.020 x` cm −2 atm −1 at 295 K , ξ = −0.0107±0.0022 . The Q-branch strengths of the ν 1 + 2ν 2 2 − ν 2 1 and the ν 1 + 2ν 2 0 − ν 2 1 bands of N2O were also measured and their values were found to be 0.0254 ± 0.0030 and 0.0033 ± 0.0007 cm−2 atm−1 at 295 K, respectively.

Line intensities of methane in the 2700–2862-cm−1 region☆

Abstract Individual strengths and wavenumbers of 2080 methane absorption lines have been measured between 2700 and 2862 cm−1 at an average resolution of 0.023 cm−1 using a grating spectrometer. The results include all lines with strengths greater than 3 × 10−5 cm−2 atm−1 observable at 296 K with a maximum path of 32 m and a pressure of 4 Torr.

Extended line assignments for the ν3 + ν4 band of 12CH4☆

Abstract The ν 3 + ν 4 absorption band of 12 CH 4 at 2.3 μm has been re-examined at 0.01-cm −1 resolution with a Fourier transform spectrometer in order to extend and review the line assignments of Bobin and Guelachvili. More than 300 new or revised excited-state energy levels have been determined by means of combination differences in ν 3 + ν 4 and corroborating lines in the spectrum of ν 3 + ν 4 − ν 4 at 3.3 μm.

Line assignments and intensities of the ν2 + ν3 − ν2 band of 12CH4☆

Abstract As part of a comprehensive effort to compile line parameters of methane from 2400 to 3200 cm−1, the P and R branches of the ν2 + ν3 − ν2 band of CH4 at 3010 cm−1 were assigned through upper state J = 9. The process utilized the analysis of ν2 + ν3 at 4544 cm−1 by J. C. Hilico, J. Degni, J. P. Champion, and G. Guelachvili (J. Mol. Spectrosc. 81, 277–302 (1980)) and the ν2 levels derived from the infrared spectrum by Margolis (in preparation) to predict the positions of the hot band. Experimentally determined lower-state energies were used to confirm assignments, and line intensities of the 300 transitions assigned are observed on the order of 10−3 cm−2 atm−1 or less.

Absorption strength measurement of the ν1 band of methyl chloride

Abstract The absorption strengths of the Q -branch manifolds of the ν 1 band of methyl chloride have been measured. The results have been used to deduce the band strength which is 32.1 ± 2.9 cm −2 atm −1 at 297 K. The P -branch absorptions have been investigated to determine the possibility of determining a vibration-rotation factor for the band. This factor is 1 + (2αβ + γ) ∼ 1.026.