ICLAS of weak transitions of water between 11300 and 12850 cm-1:: Comparison with FTS databases

Very weak water vapor absorption lines have been investigated by intracavity laser absorption spectroscopy (ICLAS) in the 11335 - 11947 and 12 336-12 843 cm(-1) spectral regions dominated by the v(1) + 3v(2) + v(3) and v(2) + 3v(3) bands, respectively. A detectivity on the order of alpha(min) similar to 10(-9) cm(-1) was achieved with an ICLAS spectrometer based on a Ti: Sapphire laser. It allowed detecting transitions with an intensity down to 5 x 10(-28) cm/molecule which is about 10 times lower than the weakest line intensities previously detected in the considered region. A line list corresponding to 1281 transitions with intensity lower than 5 x 10(-26) cm/molecule has been generated. A detailed comparison with the line lists provided by the HITRAN database and by recent investigations by Fourier transform spectroscopy associated with very long multi pass cell is presented. The rovibrational assignment performed on the basis of the ab initio calculations of Schwenke and Partridge, has allowed for determining 176 new energy levels belonging to a total of 16 vibrational states. (c) 2006 Elsevier Inc. All rights reserved.