S. Chudamani

The temperature dependence of lineshifts, linewidths and line intensities of methane at low temperatures

Abstract Employing the techniques that we have described previously for measuring infrared (i.r.) lineshifts, linewidths and line intensities with a tunable diode laser, we have measured these parameters for lines in the R(4) and R(7) multiplets of the v4-fundamental band of 12CH4 at 161, 209 (or 218) and 295 K using He, Ne, Ar, H2, N2, O2, and air as the perturbers. The temperature dependence of the collision-induced lineshift is markedly different from that of the corresponding collision-broadened linewidth.

Measurements of collision-broadened line widths in the v4-fundamental band of 12CH4 at low temperatures

Abstract Collision-broadened half-widths of several lines in the v4-fundamental band of 12CH4 have been measured at low temperatures between 130 and 295 K using a tunable diode laser and the sweep integration technique. The broadening gases are H2, N2, He, and Ar. The temperature dependence of the measured line widths is described in terms of an exponent n, which is shown not only to be different for each broadening gas but also to depend upon the tetrahedral symmetry identification of the lines of CH4.

Diode laser measurements of CO line widths at planetary atmospheric temperatures

Abstract Hydrogen-broadened half-widths and nitrogen-broadened half-widths of eight lines between P(1) and P(15) in the CO fundamental have been measured at several temperatures between 94 and 298 K using a tunable diode laser spectrometer and the sweep integration technique.

Nitrogen-broadened lines of ethane at 150 K☆

Abstract Spectral transmittance has been measured in the v9 fundamental band of C2H6 at 150 K using a Fourier transform spectrometer with apodized spectral resolution of 0.06 cm-1. Comparison of observed spectral transmittance with a line-by-line computation using the spectral catalog of Atakan et al. has yielded N2-broadened half-widths at 150 K.

Measurements on 4.7 μm CH3D lines broadened by H2 and N2 at temperatures relevant to planetary atmospheres

Abstract Absolute intensities, H2-broadened half-widths and N2-broadened half-widths of P(5, 2), P(5, 3), P(7, 2), P(7, 3) and P(8, 3) in the v2-fundamental band of 12CH3D have been measured at several temperatures between 94 and 300 K using a tunable diode laser and the sweep integration technique.

Self- and N2-broadened spectra of water vapor between 7.5 and 14.5 μm☆

Abstract Self- and N 2 -broadened absorption spectra of water vapor have been measured in the infrared between 7.5 and 14.5 μm at 294, 311, 333 and 339 K. The so-called continuum aspect of the observed absorption coefficients is interpreted in terms of existing theoretical models.

Measurement of pressure-induced shifts of infrared lines with a tunable diode laser

Abstract A simple technique for measuring pressure-induced shifts of infrared (i.r.) spectral lines using a tunable diode laser is described. The technique, which works best when lines belonging to different molecules are separated by only a few multiples of the free spectral range of the etalon used, has been employed to determine the shifts of lines in the ν4-fundamental bands of 12CH4 and 13CH4 and in the ν1-fundamental band of 14N2 16O at 295 K.

Remeasurement of the absolute intensities of CFC11 (CFCl3) and CFC12 (CF2Cl2)

Abstract The absolute intensities of the strong absorption bands of CFC11 (CFCl 3 ) and CFC12 (CF 2 Cl 2 ) have been remeasured at 300 K in view of their importance in global climatic impact and ozone depletion studies. For CFC11, our new values are 1718 ± 17 cm −2 atm −1 (846 cm −1 band) and 671 ± 8 cm −2 atm −1 (1085 cm −1 band). The values we have now obtained for the CFC12 intensities are 1421 ± 12 cm −2 atm −1 (923 cm −1 band), 1129 ± 11 cm −2 atm −1 (1102 cm −1 band), and 717 ± 14 cm −2 atm −1 (1161 cm −1 band).

Intensities and H2-broadened half-widths of Germane lines around 4.7 μm at temperatures relevant to Jupiter's atmosphere☆

Abstract Absolute intensities and H 2 -broadened half-widths of R(0) and R(1) of 72 GeH 4 have been measured at 119.5, 150.3, 199.0, 250.0, and 296.0 K using a tunable diode laser and the sweep integration technique. The combined intensity of the v 3 bands of all of the five isotopic species of GeH 4 as well as that of the Q-branches alone have been measured independently at 294 K using the Wilson-Wells-Penner-Weber technique.

Absolute intensity measurements in the v4-fundamental band of 12CH4 at planetary atmospheric temperatures

Abstract Absolute intensities of several lines in the v 4 -fundamental band of 12 CH 4 have been measured at several temperatures between 130 and 295 K using a tunable diode laser and the sweep integration technique.