THE $11 \mu m$ AND $7.6 \mu m$ BANDS OF $HN0_{3}$: LINE POSITIONS AND INTENSITIES

Abstract

A number of important bands of nitric acid have recently been analysed yielding significant progress for isolated bands with regards to the line positions and intensities. The situation was less satisfactory for the ${\nu_{s}, 2\nu_{9}}$ and ${\nu_{3},\nu_{4}}$ interacting bands located at $11 \mu m$ and $7.6 \mu m$ respectively, and this was rather unfortunate because these bands are commonly used for remote atmospheric measurements of $HNO_{3}$. The present work deals with new line position and intensity measurements and calculations. The measurements were performed allowing to cover simultaneously the two regions of interest in the $500-1360 cm^{-1}$ spectral range using high-resolution Fourier transform spectra. The calculations use a Hamiltonian matrix which takes into account for the first time both the Fermi- and Coriolis-type resonances. In this way, it has been possible to reproduce very satisfactorily the experimental data in the P, R and Q branches. Finally, synthetic spectra (line positions and intensities) in the $11 \mu m$ and $7.6 \mu m$ bands of $HNO_{3}$ have been generated.