Infrared absorption by acetylene in the 12–14 μm region at low temperatures

Spectral transmittance measurements have been performed on N₂-broadened lines of ¹²C₂H₂ and ¹²C¹³CH₂ in the 13.7 μm region at 153,200, and 296 K. From line-by-line comparison of observed and computed spectral transmittance, line strengths, half-widths, and their dependence on temperature have been deduced for conditions relevant to the atmospheres of Jupiter, Saturn, Titan, and Earth.     

Spectral transmission measurements in the v6-fundamental of 12CH3D at 8.65 μm

Spectral transmission measurements have been performed at 300°K in the v₆-fundamental band of ¹²CH₃D. Using the measured wave numbers and the calculated relative intensities of Pinkley et al, for all of the important transitions between 1100 and 1180 cm^-1, a constant hydrogen-broadened line width of 0.075 cm^-1 -atm^-1, and S_v = 63.6 cm^-2 -atm^-1, we have obtained excellent agreement between calculated and observed spectral transmission data.     

Measurements of intensities and nitrogen-broadened linewidths in the CO fundamental at low temperatures

Intensities and nitrogen-broadened half-widths of lines R(0), R(8) and R(16) in the fundamental band of ¹²C¹⁶O have been measured at 83°K, 100°K, 150°K, 200°K and 298°K. The intensities of several other lines in the P- and R-branches of the band have also been measured at 298°K. The absolute intensity derived from the line intensity data using the Herman-Wallis formula is S^°_v = 273 ± 10 cm^-2atm^-1 at S.T.P. A separate measurement employing the Wilson-Wells-Penner-Weber method has yielded S^°_v = 277 ± 4 cm^-2 atm^-1 at S.T.P. Both of these values are within 6 per cent of most of the previously published direct measurements of this parameter. The values for the line intensities reported earlier by other authors are lower by nearly 16 per cent.     

Virgin response of field induced microwave absorption in the high Tc ceramic superconductor BSCCO — RSJ model

Field induced microwave absorption is recorded at low fields (<20mT) in a high T_c ceramic superconductor (Bi,Pb)---Sr---Ca---Cu---O, after cooling in zero field to 54,77 and 90 K at 9.9 GHz and to 77K at 36.4 GHz. The results are discussed in conjunction with the dc magnetization data obtained on the same sample. It is argued that the observed features do not follow the predictions of the flux flow model while they give qualitative evidence in support of the resistively shunted Josephson junction model.     

Collision-broadened linewidths of tetrahedral molecules—II. Computations for CH4 lines broadened by N2, O2, He,Ne and Ar

Pressure-broadened widths of CH₄ lines have been calculated, using the recent formulation for tetrahedral molecules by Varanasi in the framework of the Anderson-Tsao-Curnutte theory. The present work deals mainly with lines of the R-branch of the ν₃-fundamental at 300°K, for the range 1≤J≤30 and 0≤K≤18, and for the F species. In the case of CH₄-N₂ and CH₄-O₂ collisions, octopole-quadrupole, octopole-hexadecapole, hexadecapole-quadrupole, hexadecapole-hexadecapole, dispersion and overlap interactions have been included. Broadening by noble gases was treated in terms of dispersion and overlap interactions. The value obtained in the present work by comparing theoretical and experimental results for γ⁰_CH4?N2 is not far from the magnitude deduced in studies of the far-i.r. collision-induced absorption spectra of methane. A magnitude for the hexadecapole moment of |Φ_CH4|=3·0×10^?42 esu cm⁴ was also determined. The calculated and measured linewidths are in good agreement, except in CH₄-Ar collisions. In the latter case, the theoretical values are appreciably lower than the experimental ones, which suggests that induced interactions may have to be included.     

The ν9 fundamental of ethane: Integrated intensity and band absorption measurements with application to the atmospheres of the major planets

Measurements of the absolute intensity and integrated band absorption have been performed for the ν₉ fundamental band of ethane. The intensity is found to be 34 ± 1.6 cm^-2 atm^-1 at STP, and this is significantly higher than previous estimates. It is shown that a Gaussian profile provides an empirical representation of the apparent spectral absorption coefficient. Employing this empirical profile, a simple expression is derived for the integrated band absorption, which is in excellent agreement with experimental values. The band model is then employed to investigate the possible role of ethane as a source of thermal infrared opacity within the atmospheres of Jupiter and Saturn, and to interpret qualitatively observed brightness temperatures for Saturn.     

Theoretical line widths in N2O-N2O and N2O-air collisions

Rotational half-widths have been computed at 220°K, 250°K, 280°K, and 300°K for air-broadened absorption lines of N₂O using the Anderson-Tsao-Curnutte theory. The new results are compared with previously available estimates at 300°K. Self-broadened line widths have also been computed at 300°K; good agreement has been obtained with Goody's data.     

Intensity measurements in the v4-Fundamental of CH4 at planetary atmospheric temperatures

Measurements of spectral transmittance have been performed in the v₄-fundamental band of ¹³CH₄ at low temperatures of planetary atmospheric interest with spectral resolution of 0.06 cm^-1. Comparison of observed and computed spectral transmittance on a line-by-line basis has yielded line strengths. Best agreement between measured and computed spectra was obtained when the absolute intensity of the band was taken as 123 cm^-2 atm^-1 at 296 K.     

Measurements of nitrogen-broadened line widths of acetylene at low temperatures

Spectral transmittance measurements have been performed on N₂-broadened lines of C₂H₂ in the 7.53 μm region at 153 and 200 K with a spectral resolution of 0.06 cm^-1. The line widths have been determined as functions of temperature and rotational quantum number using line-by-line comparison of theoretical and experimental values of spectral transmittance.     

Nitrogen-broadened lines of monodeuterated methane in the 4.5 μm region at low temperatures

Nitrogen-broadened halfwidths of rotational lines of CH₃D have been deduced from spectral transmittance measurements in the v₂-fundamental at 100 and 200 K with a spectral resolution of 0.06 cm^-1. The line widths appear to be 1.5 times larger and exhibit the same 1/T dependence on temperature as lines of CH₄.