Linestrengths of nitric acid from 850 to [formula omitted

Abstract

Several thousand line positions and strengths of HNO 3 in the 850– 920 cm −1 region were retrieved from spectra at low sample pressures at 299 K and high spectral resolution ( 0.0027 cm −1 ) using the McMath–Pierce Fourier transform spectrometer (FTS) at the National Solar Observatory located at Kitt Peak, AZ. Of these, 733 linestrengths of the ν 5 band and 402 lines of the 2 ν 9 band were measured with precisions of 10% or better. In addition, over 800 features with no assignments and 8–15% uncertainties in the linestrengths were obtained. The measured linestrengths of ν 5 and 2 ν 9 were compared to prior measurements and to the values given in the 2000 HITRAN compilation. The average ratios of HITRAN/present was found to be 1.14±0.06, but the relative band intensities of the fundamental and overtone were in agreement with the calculated values. The intensities of strong absorptions in the Q branch of the ν 5+ ν 9− ν 9 band (between 885.418 and 885.437 cm −1 ) were within 4% of the 2000 HITRAN values, although there was an offset in the positions. The analysis of these data was greatly hindered by the high density of transitions and the lack of knowledge about other hot bands in the region.