Investigation of effective line intensities of trans-HONO near 1255 cm−1 using continuous-wave quantum cascade laser spectrometers

•Effective line strengths of trans-HONO between 1251.8 and 1257.2 cm−1.•Comparison to previous line strength data reported in literature.•Synthetization and calibration of concentration of gaseous HONO samples•Sub-ppb HONO detection limit.

Effective line intensities of P branch transitions of trans-nitrous acid (HONO) in the ν3 H-O-N bending mode near 1255 cm−1 have been determined by scaling measured HONO absorption intensities by continuous-wave quantum cascade laser absorption spectroscopy to reference values. Gaseous HONO samples were synthetized in the laboratory using the reaction of H2SO4 and NaNO2 solutions and the heterogeneous formation on surfaces in the presence of ambient water vapor and NO2 gas in a sealed gas sampling bag. The quantification of HONO was performed using a denuder associated with a NOx analyzer. Observed absorption line strengths for the trans conformer are found to be by a factor of approximately 1.17 higher than previously reported line strengths.