Empirical line parameters of methane in the 1.63-1.48 μm transparency window by high sensitivity Cavity Ring Down Spectroscopy

The positions and intensities of methane in the 1.58 mu m transparency window have been measured by high sensitivity Cavity Ring Down Spectroscopy at room temperature. The achieved sensitivity allowed measuring intensities as small as 3 x 10(-29)cm/molecule i.e. three orders of magnitude smaller than the intensity cut off of the HITRAN line list of methane. The complete list contains a total of 16,149 transitions between 6165 and 6750 cm(-1). Their intensity values vary over six orders of magnitude from 1.6 x 10(-29) to 2.5 x 10(-23) cm/molecule. Transitions due to CH3D in "natural" abundance in our methane sample were identified using a new spectrum of CH3D recorded separately with a Fourier Transform spectrometer. From simulations of the CH3D and methane spectra at low resolution, the CH3D isotopologue has be found to contribute by up to 30% of the absorption near 1.58 mu m. (C) 2010 Elsevier B. V. All rights reserved.