FTS BAND INTENSITY MEASUREMENTS IN NITROUS ACID

Abstract

$^{1}$ P. G. Ashmore and B. J. Tyler, J. Chem. Soc. 1017 (1961), I. R. Beattie and S. W. Bell, J. Chem. Soc. 1686 (1957), and L. Harris and K. L. Churney, J. Chem. Phys. 47, 1703 (1967).Author Institution:The infrared absorption intensities of the four in-plane fundamental bands of trans-nitrous acid (HONO) and two in-plane fundamental bands of cis-nitrous acid have been measured in the gas phase using a Fourier transform spectrometer with $0.06 cm^{-1}$ resolution. In the gas phase, nitrous acid exists in an equilibrium mixture. At room temperature $(296^{\circ})$the following equilibria must be considered: $NO+NO_{2}+H_{2}O\Leftrightarrow 2HONO, K=1.36{atm}^{-1} \\ NO+NO_{2}\Leftrightarrow N_{2}O_{3}, K=0.585 {atm}^{-1} \\ 2NO_{2}\Leftrightarrow N_{2}O_{4}, K=8.20 {atm}^{-1}$ We have used equilibrium constants from the $literature^{1}$ to determine the partial pressure of HONO over a range of conditions. In our measurements, the nitrous acid pressure was typically one torr, and the total pressure of the equilibrium mixture was typically 60 torr. The 20 cm absorption cell was pressurized to one atmosphere with dry nitrogen to minimize instrument distortion of the band shapes. Interferences in the HONO bands caused by overlapping absorptions of the other components of the mixture were digitally subtracted from the absorbance spectrum. The intensities of the $\nu_{1}$ and $\nu_{2}$ bands of $N_{2}O_{3}$ were also measured