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9+
4-
4 HOT BAND OF ETHANE: EVIDENCE OF INTERACTION WITH THE
12 FUNDAMENTAL.
J. R. COOPER, N. MOAZZEN-AHMADI, Department of Physics and Astronomy, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada.
The
9 (methyl rock) fundamental band of ethane occurs in the 12 µ m region. It is the strongest band of ethane in a terrestrial window and is commonly used for the identification of ethane in the Jovian planets. The
9+
4-
4 band occurs in the same region; neither can be analysed as an isolated band, since both are embedded in the torsional bath of the ground vibrational state. We report here a global fit model including data from the
3 (C-C stretch) fundamental, the
4, 2
4-
4, and 3
4 torsional transitions, the
9 fundamental, and its
9+
4-
4 hot band. The combined data set of more than 4000 lines has been fitted to within experimental uncertainty using a model Hamiltonian which includes many terms which were important in analyzing the corresponding hot band of CD3CD3. We have therefore identified Coriolis interactions with the ground vibrational state (gs) for both the
9 and
9+
4-
4 bands, as well as gs/
3 Fermi coupling, and have determined several barrier-dependence terms which were not previously accessible. More remarkably, we have also identified a new, resonant interaction with the
12 fundamental which -- unlike terms included in previous models -- is off-diagonal in the torsional quantum number
.