Frequencies
Figure: Frequency Shifts in Calculated Spectrum of Vinyl Cyanide
The power of the QM analyses (and also the reason for their necessity) is that they allow the
calculation of many spectral lines based on an accurate measurement of a smaller subset. It has long
been know that the accuracy of these calculations is much higher for lines that represent an
interpolation of quantum numbers than for those based on an extrapolation. Indeed, one of the primary
issues for laboratory spectroscopist when simulating spectra for astronomical use is how far to take
these extrapolations. In excited vibrational states that have local perturbations this problem is
exasperated even for states well within the bounds of the analyses.
Figure: Frequency Shifts in Calculated Spectrum of Vinyl Cyanide
Figure: Methanol Spectrum. A small segment of the spectrum of methanol
near 625 GHz. The blue trace is a spectrum simulated from the QM catalog and
the red trace a simulation based on the CES.