15min:

V. MALATHY DEVI, D. CHRIS BENNER, Department of Physics, The College of William and Mary, Box 8795, Williamsburg, VA 23187-8795; M. A. H. SMITH, C. P. RINSLAND, Atmospheric Sciences, NASA Langley Research Center, Mail Stop 401A, Hampton, VA 23681-2199; AND L. R. BROWN, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109.

A multispectrum nonlinear least squares fitting technique has been used to determine Lorentz air-broadening coefficients and air-induced shift coefficients for transitions in the ₃ fundamental band of ¹²CH₃D in the spectral region between 1154 and 1430 cm^-1. Eleven high-resolution (0.005 cm^-1) room-temperature absorption spectra, recorded using the 1-m Fourier transform spectrometer (FTS) at the McMath-Pierce facility of the National Solar Observatory at Kitt Peak, were simultaneously analyzed. The data set included both low-pressure (1 to 3 Torr) spectra of 98% pure CH₃D and spectra of lean mixtures (~ 1%) of CH₃D in dry air at total pressures from about 100 Torr to 400 Torr. Cell path lengths of 25 and 150 cm were used.

Air-broadening coefficients were determined for for more than 360 ₃ transitions with rotational quantum numbers as high as J''=17 and K''=17. Air-induced shift coefficients were also determined for most of these transitions. The measured broadening coefficients range from 0.016 to 0.073 cm^-1 atm^-1 at 296K, and the shift coefficients range vary from about -0.0086 to +0.0058 cm^-1 atm^-1. The majority of the shifts are negative, and the positive shifts often involve transitions with J''=K''. The ^QQ sub-band J''=K'' transitions are also associated with the smallest broadening coefficients. Weak line mixing effects have been observed in a few high-J transitions with K''=3, and we have determined off-diagonal relaxation matrix element coefficients for several A⁺A^- (A1A2) split components. At low to medium values of J'', the A⁺A^- splittings are very small, and the two components are practically unresolved. Variations of the measured parameters with rotational quantum numbers and differences between the A and E symmetry species will be discussed. We will also compare our measurements with the values on the current HITRAN compilation\footnoteL.~S.~Rothman et al. , JQSRT \underline\textbf53, 665-710 (1998). and with other available measurements.