Hot methane spectra for astrophysical applications

We have recorded laboratory high resolution Fourier transform spectra of methane (CH4) emission at 800, 1000 and 1273 K with an effective hot path length of 51 cm. The spectra span 2000-5000 cm(-1) (resolution 0.020 cm(-1), nominal pressure 16.3 Torr) and 5000-6400 cm(-1) (resolution 0.040 cm(-1), nominal pressure 79 Torr) for each temperature. We have determined line positions and intensities for 15 434, 22 163 and 25 727 emission lines in the 800, 1000 and 1273 K spectra, respectively. Positions have been calibrated to a la accuracy of better than 0.001 cm(-1) in the 2000-5000 cm(-1) spectra and 0.003 cm(-1) in the 5000-6400 cm(-1) spectra based on the 2001 methane line list update in the HITRAN database. We have calculated absolute line intensity calibration factors for these lines based on HITRAN intensities scaled to the appropriate temperature. In addition, since some methane lines in our spectra appeared in absorption, we have directly used intensities calculated from HITRAN for 757, 839 and 1094 additional lines in the 800, 1000 and 1273 K spectra, respectively. We expect our new hot methane line lists to be useful for direct comparison and simulation of the spectral energy distribution from brown dwarfs and hot extrasolar giant planets, and may also be used for comparison with line lists generated by both ab initio quantum chemists and more traditional theoretical spectroscopists. Furthermore, the method we have developed for obtaining high temperature line lists can be, applied to other molecules in the HITRAN database. (C) 2003 Elsevier Ltd. All rights reserved.