Cross sections in the 2ν5 band of formaldehyde studied by cavity enhanced absorption spectroscopy near 1.76 µm
- 3 January 2002
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Physical Chemistry Chemical Physics
- Vol. 4 (3) , 445-450
- https://doi.org/10.1039/b109300m
Abstract
The 2ν 5 C–H stretching band of formaldehyde has been studied by cavity enhanced absorption spectroscopy near 1.76 μm using the output of an external cavity diode laser. Strong individual transitions have been spectroscopically identified, and the absorption cross section and air broadening parameter measured for the QR1(10) line at 5676.21 cm−1, a wavenumber at which interference from absorption by atmospheric CH4 and other constituents is minimal. The integrated cross section is found to be 5.7±0.6×10−22 cm2 cm−1, and the pressure broadening coefficient for air at 295 K is 3.93 MHz Torr−1 (half width at half maximum of the Lorentzian component). The integrated intensity of the 2ν 5 absorption band is found to be a factor of 108 smaller than that of the ν 5 fundamental. Implications of these values for the measurement of atmospheric formaldehyde by absorption near 1.76 μm are discussed.Keywords
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