A NEW IMPROVED EMPIRICAL POTENTIAL ENERGY SURFACE FOR WATER

Author Institution: Department of Physics, Ohio State University; Department of Physics and Astronomy, University College LondonA new method for refining potential energy surfaces in triatomic molecules via nonlinear least squares has been applied to water in its ground electronic state. Experimental rovibrational energy levels with $J<10$ and band origins observed below $20,000 cm^{-1}$ have been used to improve upon Jensen's $surface^{1}$ in a fully variational calculation. The new surface does a much better job at reproducing rotational energies with large values of $K_{A}$ than those available in the literature, while at the same time maintaining physically meaningful values for all of the parameters involved. The results should be of general interest, however they will be discussed in terms of their relavence to searches for spectral lines in the microwave and infrared. $^{1}$ Per Jensen, J. Mol. Spectrosc. 133, 438-460 (1989)

THE MILLIMETER AND SUBMILLIMETER-WAVE SPECTRUM OF THE ν5\nu_{5} AND 2ν92\nu_{9} VIBRATIONAL STATES OF NITRIC ACID: HNO3HNO_{3}

Author Institution: Department of Physics, The Ohio State University; Department of Physics, University of South AlabamaThe millimeter-wave spectrum of nitric acid ($HNO_{3}$) in its $\nu_{5}$ and $2\nu_{9}$ vibrational states has been studied. Data were taken using a TWT based broadband spectrometer. The $\nu_{5}$ and $2\nu_{9}$ states exhibit a large perturbation from the ordinary Watson Hamiltonian due to a Fermi interaction between the energy levels. The results of an analysis will be presented in which the data from both states were fit simultaneously to a Hamiltonian in which the Fermi interaction is taken into account. The data from both states include a wide range of quantum numbers on both sides of the perturbation and a large number of data points in regions where the perturbation interaction is very large. We find that the transitions which show the largest perturbation can be accurately predicted with the Hamiltonian used for the analysis. The results of this analysis will be compared with the results of previous studies in the infrared frequency region

THE MILLIMETER AND SUBMILLIMETER-WAVE SPECTRUM OF THE ν5\nu_{5} AND 2ν92\nu_{9} VIBRATIONAL STATES OF NITRIC ACID: HNO3HNO_{3}

Author Institution: Department of Physics, The Ohio State University; Department of Physics, University of South AlabamaThe millimeter-wave spectrum of nitric acid ($HNO_{3}$) in its $\nu_{5}$ and $2 \nu_{9}$ vibrational states has been studied. Data were taken using a TWT based broadband spectrometer. The $\nu_{5}$ and $2 \nu_{9}$ states exhibit a large perturbation from the ordinary Watson Hamiltonian due to a Fermi interaction between the energy levels. Additionally, the large torsional splitting of transitions following b-type selection rules was observed for the $2 \nu_{9}$ vibrational state. An interesting effect arising from the mixing of the $2 \nu_{9}$ and $\nu_{5}$ energy levels is the large splitting of the b-type transitions of the $\nu_{5}$ vibrational state. A smaller torsional splitting was observed for transitions following a-type selection rules inn the Q-branch transitions of both $\nu_{5}$ and $2 \nu_{9}$. The results of our analysis will be presented and compared with the results of previous studies