An improved database for the 9μm region of the formic acid spectrum

The 9μm region of the formic acid spectrum is associated with the strong ν6 band. Located in an atmospheric window, its sharp Q-branch structure near 1105cm-1 is commonly used to probe tropospheric formic acid by infrared remote sensing techniques. Retrieval of HCOOH concentrations usually rely on spectroscopic information available in atmospheric databases such as HITRAN and GEISA. The intensity information available therein is a factor of about 2 lower than laboratory measurements. Following our recent contribution [Vander Auwera J, Didriche K, Perrin A, Keller F. Absolute line intensities for formic acid and dissociation constant of the dimer. J Chem Phys 2007;126:124311], we generated a new set of line parameters and show that it provides a significantly improved modeling of the ν6 spectral region of formic acid.