Determination of the low energy values of (CH4)-C-13 transitions in the 2 nu(3) region near 1.66 mu m from absorption spectra at 296 and 81 K

作者：Lyulin O M; Kassi S; Sung K; Brown L R; Campargue A^*

来源：Journal of Molecular Spectroscopy, 2010, 261(2): 91-100.

DOI：10.1016/j.jms.2010.03.008

• Methane
• CH4
• (CH4)-C-13
• Absorption spectroscopy
• HITRAN
• GOSAT
• Empirical lower states

The high resolution absorption spectra of (CH4)-C-13 were recorded at 81 K by differential absorption spectroscopy using a cryogenic cell and a series of distributed feed back (DFB) diode lasers and at room temperature by Fourier transform spectroscopy. The investigated spectral region corresponds to the high energy part of the (CH4)-C-13 tetradecad dominated by the 2 nu(3) overtone near 5988 cm(-1). Empirical line lists were constructed containing, respectively, 1629 (CH4)-C-13 transitions detected at 81 K (5852-6124 cm(-1)) and 3481 features (including 85 lines of (CH4)-C-12) measured at room temperature (5850-6150 cm(-1)); the smallest measured intensities are about 3 x 10(-26) and 4 x 10(-25) cm/molecule at 81 and 296 K, respectively. The lower state energy values were derived for 1196 (CH4)-C-13 transitions from the variation of the line intensities between 81 and 296 K. These transitions represent 99.2% and 84.6% of the total absorbance in the region, at 81 and 296 K. respectively. Over 400 additional weak features were measured at 81 K and could not be matched to lines observed at room temperature. The quality of the resulting empirical low energy values is demonstrated by the excellent agreement with the already-assigned transitions and the clear propensity of the empirical low values to be close to integers. The two line lists at 81 and at 296 K provided as Supplementary material will enable future theoretical analyses of the upper (CH4)-C-13 tetradecad.

• 出版日期2010-6