Measurement of pressure-broadening and lineshift coefficients at 77 and 296 K of methane lines in the 727 nm band using intracavity laser spectroscopy

Abstract Pressure-broadening coefficients and pressure-induced lineshifts of several rotational- vibrational lines have been measured in the 727 nm absorption band of methane at temperatures of 77 and 296 K, using nitrogen, hydrogen, and helium as the foreign-gas collision partners. A technique involving intracavity laser spectroscopy is used to record the methane spectra. Average values of the broadening coefficients (cm -1 atm -1 ) at 77 K are: 0.199, 0.139, 0.055, and 0.29 for collision partners N 2 , H 2 , He, and CH 4 , respectively. Typical average values of the pressure-induced lineshifts (cm -1 atm -1 ) at 77 K and for the range of foreign gas pressures between 10 and 200 torr are -0.052 for N 2 , -0.063 for H 2 , and +0.031 for He. All the values obtained at 296 K are considerably different from the corresponding values at 77 K. This represents the first report of pressure-broadening and shifting coefficients for the methane transitions in a region where the Δ v C-H = 5 band occurs.

[1]  K. Lehmann,et al.  The high‐resolution visible overtone spectrum of CH4 and CD3H at 77 K , 1984 .

[2]  J. Bergstralh,et al.  Vertical aerosol structure of Neptune: Constraints from center-to-limb profiles , 1989 .

[3]  V. R. Mironenko,et al.  Quantum noise in intracavity laser spectroscopy , 1980 .

[4]  J. S. Neff,et al.  Absolute spectrophotometry of Neptune: 3390 to 7800 Å , 1983 .

[5]  T. Plakhotnik,et al.  Intracavity spectrometer with a ring travelling-wave dye laser: Reduction of detection limit , 1983 .

[6]  K. Baines,et al.  Absorption coefficients for the 6190-A CH4 band between 290 and 100 K with application to Uranus' atmosphere , 1990 .

[7]  J. Maillard,et al.  The region of the 3ν3 band of methane , 1980 .

[8]  G. Hunt.  The Atmospheres of the Outer Planets , 1983 .

[9]  William H. Smith,et al.  High-resolution observations of the 6815-Å band of methane in the major planets , 1983 .

[10]  A. Kachanov,et al.  Parasitic selection in intracavity laser detection spectroscopy , 1982 .

[11]  P. Varanasi,et al.  The temperature dependence of lineshifts, linewidths and line intensities of methane at low temperatures , 1990 .

[12]  K. Baines.  Interpretation of the 6818.9-Å methane feature observed on Jupiter, Saturn, and Uranus☆ , 1983 .

[13]  Uwe Fink,et al.  Methane absorption variations in the spectrum of Pluto , 1987 .

[14]  J. S. Neff,et al.  Absolute spectrophotometry of Titan, Uranus, and Neptune: 30,500–10,500 Å , 1984 .

[15]  M. E. Mickelson,et al.  NEW MEASUREMENTS OF THE 6190-A BAND OF METHANE , 1991 .

[16]  J. Lunine.  Origin and Evolution of Outer Solar System Atmospheres , 1989, Science.

[17]  F. Stoeckel,et al.  Quantitative measurements of very weak H2O absorption lines by time resolved intracavity laser spectroscopy , 1982 .

[18]  H. Hammel.  Neptune Cloud Structure at Visible Wavelengths , 1989, Science.

[19]  C. G. Stevens,et al.  Overtone spectra of C–H oscillators in cold molecules , 1988 .

[20]  J. Reilly,et al.  The Stark effect in methane’s 3ν1+ν3 vibrational overtone band , 1993 .

[21]  A. Savitzky,et al.  Smoothing and Differentiation of Data by Simplified Least Squares Procedures. , 1964 .

[22]  D. Jennings,et al.  Spectral Shifts of Methane Lines in Collisions with Hydrogen, Helium, Nitrogen, and Argon , 1989, High Resolution Fourier Transform Spectroscopy.

[23]  D. Jennings,et al.  Measurements of nitrogen-, hydrogen- and helium-broadened widths of methane lines at 9030–9120 cm-1 , 1985 .

[24]  S. Sarangi,et al.  Measurements on the infrared lines of planetary gases at low temperatures. I - Nu-3 fundamental of methane. , 1973 .

[25]  M. Tomasko,et al.  Clouds, aerosols, and photochemistry in the Jovian atmosphere , 1986 .

[26]  J. Margolis,et al.  INFRARED ABSORPTION SPECTRUM OF $CH_{4}$ AT 9050 $CM^{-1}$ , 1968 .

[27]  K. Baines,et al.  The atmospheric structure and dynamical properties of Neptune derived from ground-based and IUE spectrophotometry , 1990 .

[28]  U. Fink,et al.  Application of methane band-model parameters to the visible and near-infrared spectrum of Uranus , 1980 .

[29]  James L. Elliot,et al.  Pluto's atmosphere , 1989 .

[30]  V. R. Mironenko,et al.  Quantitative measurement of small absorption coefficients in intracavity absorption spectroscopy using a cw dye laser , 1975 .

[31]  C. E. Keffer,et al.  Limits on the intramolecular relaxation rate for high vibrational overtones of methane , 1984 .

[32]  E. Berik,et al.  Intracavity laser detection of ammonia and methane absorption spectra in the region 6000–6500 Å , 1979 .

[33]  K. Rao,et al.  Molecular Spectroscopy: Modern Research , 1972 .

[34]  D. Jennings,et al.  Measurements of argon-, helium-, hydrogen-, and nitrogen-broadened widths of methane lines near 9000 cm−1 , 1988 .

[35]  Lawrence P. Giver,et al.  Intensity measurements of the CH4 bands in the region 4350 A to 10,600 A , 1978 .

[36]  J. Margolis,et al.  The temperature dependence of the half widths of some self-and foreign-gas-broadened lines of methane , 1973 .

[37]  P. Varanasi.  Collision-broadened half-widths and shapes of methane lines , 1971 .

[38]  R. West,et al.  Voyager 1 imaging and IRIS observations of Jovian methane absorption and thermal emission - Implications for cloud structure , 1985 .

[39]  F. Stoeckel,et al.  Intracavity absorption line shapes and quantitative measurements on O2 , 1983 .

[40]  Kevin H. Baines,et al.  The structure of the Uranian atmosphere - Constraints from the geometric albedo spectrum and H2 and CH4 line profiles , 1986 .

[41]  I. N. Sarkisov,et al.  Intracavity laser spectroscopy , 1989 .

[42]  George H. Atkinson,et al.  Methane overtone absorption by intracavity laser spectroscopy , 1989 .

[43]  D. Hunten,et al.  Determination of line intensity and pressure broadening of the 619.68 nm methane overtone absorption line at low temperatures using intracavity laser spectroscopy , 1993 .

[44]  F. Stoeckel,et al.  Intracavity-laser-absorption spectroscopy of the visible overtone transition of methane in a supersonically cooled jet , 1991 .

[45]  V. Mironenko,et al.  Dependence of the sensitivity of intracavity laser spectroscopy on generation parameters , 1983 .