Cross sections in the 2ν5 band of formaldehyde studied by cavity enhanced absorption spectroscopy near 1.76 µm

High-Resolution Absorption Studies of the Ã1A2−X̃1A1202401Band of Formaldehyde

“…On closer inspection of Figure 3 however, it appears that some of the deviation between our data and the simulations may be due to such perturbations. Two of the upper rotational states found by Birss et al to be perturbed by the triplet state are (in the notation J K c ,K a ) 20 4,17 and 11 9,2 . Weak lines probing these states appear in the simulation at 30634.52 cm -1 and 30636.83 cm -1 , respectively, and show relatively poor agreement with our data compared to the surrounding features.…”

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

“…Such an analysis is beyond the scope of this study. The strongest absorption lines in the spectrum (those with absorption cross-sections greater than 5 × 10 transition of the 2ν 5 overtone, and over 4000 times weaker than the ν 1 C-H stretch [2].…”

“…The photolysis of formaldehyde, H 2 CO: H 2 CO + hν → H + HCO and the subsequent formation of the hydroperoxyl radical, HO 2 , in the presence of oxygen: play a key role in oxidation chain reactions. The importance of these reactions has encouraged efforts to improve the spectroscopic data on H 2 CO and HO 2 for use in field studies and laboratory experiments [2][3][4][5][6][7][8].…”

“…Barry et al reported the 2ν 5 overtone band (around 5676 cm −1 ) using CEAS [2], and have shown that the results from CEAS closely match those from CRDS [11]. For applying absorption spectroscopy to trace measurements of H 2 CO, the stronger fundamental vibration bands have usually been used.…”

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

“…The absorption cross sections in this wavelength range are rather small, but the high sensitivity of cavity enhanced techniques can compensate for this drawback. As for absorption features of CH 2 O in this wavelength range, Barry et al [21][22][23] have measured absolute absorption cross sections of selected lines in the 2m 5 transition using two methods, cavity ring down spectroscopy, CRDS, and cavity enhanced absorption spectroscopy (CEAS). They have reported a good agreement between the absorption cross sections obtained by the two different methods.…”