Knowledge Bank

Using our preliminary assignment and analysis of diode laser and Fourier transform spectra of the $12\mu m$ region of ehtane, an extended model for $\nu 9+\nu 4-\nu 4$ has been constructed and applied to the analysis. Interactions between the upper levels of $\nu 9+\nu 4$ and those of $3\nu 4,4\nu 4,5\nu 4$ and $6\nu 4$ are included in the current model. Calculated values for the interaction constants have been determined from a combination of a priori calculation results and analysis of torsional splitting data. These interaction constants as well as the calculated $\nu 4$ overtone levels are used as fixed parameters in a simultaneous 24 state analysis. The analysis of 1349 upper state energy levels of the hot band yields a standard deviation of $0.0957cm-1$. This result includes several localized resonances which are probably due to the interaction of $\nu 9+\nu 4$ levels with $\nu 12$ levels. When these locally perturbed levels are removed, the remaining 1098 levels yield a standard deviation of $0.009cm-1$. The current state of the analysis will be discussed; the analysis methods will be described.