Effective line strengths of trans-nitrous acid near 1275 cm−1 and cis-nitrous acid at 1660 cm−1

We determined the effective line strengths of the trans conformer of nitrous acid (HONO) near 1275 cm−1 (R-branch of ν3 mode, NOH bend) and of the cis conformer at 1660 cm−1 (R-branch of ν2 mode, NO stretch), both at a spectral resolution of 0.001 cm−1 by tunable infrared laser differential absorption spectroscopy (TILDAS) utilizing continuous-wave quantum cascade (cw-QC) lasers. Absorbance of one conformer was measured while simultaneously quantifying the mixing ratio of total HONO by catalytic conversion to nitric oxide (NO) followed by calibrated absorption spectroscopy. Line strengths obtained here are consistent with previously reported band strengths for the trans conformer but are lower by a factor of approximately 2.4 for the cis conformer.

► Effective line strengths for the cis-HONO at 1660 cm−1 was quantified. ► Effective line strengths for the trans conformer near 1275 cm−1 was also quantified. ► Results for trans-HONO are in agreement with previously published band strength. ► Previous cis band strength is high by factor of 2.4 due to spectral interference.