TORSIONAL SPLITTING IN THE 2-NU(9), AND NU(5) VIBRATIONAL BAND OF HNO3

Torsional splittings in both the 2 nu(9) and nu(5) vibrational states have been resolved and observed in the millimeter/submillimeter spectr um of HNO3. The former splitting is due to the torsional motion of H a round the NO bond in the vg mode, whereas the latter is due to the lar ge mixing which results from the near degeneracy (17.34 cm(-1)) of the two vibrational modes. It is possible to use these data in the contex t of a very simple model to quantitatively predict the observed intens ity of the 2 nu(9) infrared band. Furthermore, these data remove the f itting indeterminacy which exists in the rotation-vibration data betwe en the difference in the vibrational energy of the two states and the Fermi interaction term. (C) 1994 Academic Press, inc.