Multispectrum fitting of line parameters for 12C2H2 in the 3.8-μm spectral region

Using FT spectra (Bruker IFS 120, unapodized FWHM resolution approximate to 0.001 cm(-1)) of acetylene (C2H2)-C-12, absolute positions and intensities have been measured for about 250 lines between 2600 and 2800 cm(-1) in the v(2) + v(5)(1) and (3v(4) + v(5))(+)(0) cold bands, and in the v(1) - v(5)(1) v(3) - v(4)(1), and v(2) + (v(4) + v(5))(0)(+) - v(4)(1) hot bands. These measurements improve the accuracy of wavenumbers previously available and lead to individual line intensities for the first time in this spectral region. A multispectrum fitting procedure has been used to retrieve line parameters from five experimental spectra recorded at different pressures. The frequencies of the v(3) band of (CO2)-C-12-O-16 allowed to perform an absolute wavenumber calibration. The 5 and has been accuracy of the amount of (C2H2)-C-12 in the sample has been checked using the 3v(5)(1) cold band around 2100 cm(-1), estimated to be around +/- 2%. The average absolute accuracy of the line parameters obtained in this work has then been estimated to be +/- 0.0002 cm(-1) for line positions, and +/- 5% for line intensities. For each studied band, the vibrational transition dipole moment squared value has been determined, as also empirical Herman-Wallis coefficients. A complete line list containing positions and intensities for the five strongest bands around 3.8 mu m has been set up for atmospheric applications. (c) 2006 Elsevier Ltd. All rights reserved.