The Energy Levels of the nu(5)/2nu(9) Dyad of HNO(3) from Millimeter and Submillimeter Rotational Spectroscopy

In this paper we show that the rotational structure of the nu(5)/2nu(9) infrared band near 11 m can be synthesized to high accuracy from pure rotational measurements in the millimeter- and submillimeter-wave region. The analysis uses an internal axis system Hamiltonian that accounts for the rotational dependence of the torsional splitting in 2nu(9), the induced torsional splitting in nu(5), and all of the infrared line positions, including those in the regions of strongest mixing and of highest excitation. This model also predicts the strength of the 2nu(9) infrared band due to the strong Fermi mixing with nu(5). The analysis is based on the 2317 millimeter/submillimeter lines and uses the well-documented SPFIT routines of JPL. Copyright 2001 Academic Press.