Absolute room temperature (294 ± 2 K) absorption cross sections for the Ã 1A 2-X̃ 1A 1 electronic transition of formaldehyde have been measured over the spectral range 30285-32890 cm -1 (304-330 nm) using ultraviolet (UV) laser absorption spectroscopy. Accurate high-resolution absorption cross sections are essential for atmospheric monitoring and understanding the photochemistry of this important atmospheric compound. Absorption cross sections were obtained at an instrumental resolution better than 0.09 cm -1, which is slightly broader than the Doppler width of a rotational line of formaldehyde at 300 K (∼0.07 cm -1) and so we were able to resolve all but the most closely spaced lines. Comparisons with previous data as well as with computer simulations have been made. Pressure broadening was studied for the collision partners He, O 2, N 2, and H 2O and the resulting broadening parameters have been measured and increase with the strength of intermolecular interaction between formaldehyde and the collision partner. The pressure broadening coefficient for H 2O is an order of magnitude larger than the coefficients for O 2 and N 2 and will contribute significantly to spectral line broadening in the lower atmosphere. Spectral data are made available as Supporting Information.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry