Knowledge Bank

Formaldehyde (H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$CO) is detected in the earth's troposphere by infrared techniques in the 3.5 and 5.7-$\mu$m regions. Recent measurements produced line positions and relative line intensities}, \textbf{221}, (2003) 192. A. Perrin, A. Valentin, and L. Daumont, \textit{J. Mol. Struct.}, \textbf{780-781}, (2006) 28.} and also IR$\iff$UV line intensity intercomparisons }, in press, (2007).}. For atmospheric retrievals absolute intensities and line broadening parameters are needed. For that, new Fourier transform spectra were recorded at high resolution (0.0035 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$) at LADIR in the 1600-3000 cm$\mathrm{<mrow\; data-mjx-texclass="ORD">-1</mrow>}$ spectral region. Low pressures (up to 0.5 torr) of H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$CO were generated by warming paraformaldehyde. An appropriate monitoring of the heating temperature ($\approx$ 40 C) avoided any polymerization and allowed to obtained a stable pressure of pure H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$CO (98 $\pm$ 1%). In this way accurate line positions and absolute intensities of H$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$CO were measured and theoretical modelled in the 3.5 and 5.7-$\mu$m regions leading also to an intercomparison of intensities between the two spectral regions. The determination of self- and N$\mathrm{<mrow\; data-mjx-texclass="ORD">2</mrow>}$-broadening coefficients is in progress.