The rotationally-resolved absorption spectrum of formaldehyde from 6547 to 6804cm−1

Abstract

Access to the full text of the published version may require a subscription. Rights AbstractThe room temperature absorption spectrum of formaldehyde, H 2 CO, from 6547 to 6804 cm −1 (1527 to 1470 nm) is reported with a spectral resolution of 0.001 cm −1 . The spectrum was measured using cavity-enhanced absorption spectroscopy (CEAS) and absorption cross-sections were calculated after calibrating the system using known absorption lines of H 2 O and CO 2 . Several vibrational combination bands occur in this region and give rise to a congested spectrum with over 8000 lines observed. Pressure broadening coefficients in N 2 , O 2 , and H 2 CO are reported for an absorption line at 6780.871 cm −1 , and in N 2 for an absorption line at 6684.053 cm −1 .

Absolute absorption cross sections for two selected lines of formaldehyde around 6625cm−1

“…CH 2 O has been quantified using cw-CRDS at around 6600 cm À1 in two recent publications [27,28] and both studies were in rather large disagreement with the absorption cross sections reported by Staak et al [24]. CH 2 O has been identified by Djehiche et al [27] as a product in the photolysis of CH 3 ONO.…”

“…They have determined the absorption cross section of one absorption line under their experimental conditions (24 mbar air) using a commercial, calibrated standard cylinder of CH 2 O (Air Liquide): the cylinder was labeled at 100 ppm, however an analysis using the well-known DNPH/ HPLC method revealed a concentration of only 40 ± 4 ppm. Extrapolation of the obtained absorption cross section to the conditions used by Staak et al [24] (2 mbar CH 2 O), assuming a Voigt profile and applying the broadening coefficients for N 2 and CH 2 O such as obtained by Staak et al [24], leads to a line strength a factor of 2 smaller. However, broadening coefficients for the different bath gases are not known with high precision, so the comparison is somewhat arguable.…”

“…They have reported a good agreement between the absorption cross sections obtained by the two different methods. In a more recent work, Staak et al [24] measured the absorption spectrum of CH 2 O in the range 6547-6804 cm À1 , where transitions of several combination bands can be found [25]. They employed CEAS for their measurements and have obtained absolute absorption cross sections by calibrating the mirror reflectivity by determining the line strengths of selected absorption lines of CO 2 and H 2 O, obtained from the HITRAN data base [26].…”

Division Xii / Commission 14 / Working Group Collision Processes

“…H 2 CO lines broadened by H 2 CO, N 2 and O 2 (E) (Staak et al 2005). HCO + lines broadened by He and Ar (T) (Buffa 2007).…”

The near infrared cavity-enhanced absorption spectrum of methyl cyanide

“…The experimental off-axis CEAS set-up is essentially the same as the one described in [58], [59]. The length of the optical cavity (Layertec mirrors: r = -2 m, R ~ 0.997) was 113 cm and the volume enclosed by the sample chamber was approximately 2 dm 3 .…”