THE USE OF CAAARS (Computer Aided Assignment of Asymmetric Rotor Spectra ) IN THE ANALYSIS OF
ROTATIONAL SPECTRA.
(CAAARS)
Ivan R. Medvedev, Manfred Winnewisser, Brenda P. Winnewisser, Frank C. Delucia And Eric Herbst Department
of Physics, The Ohio State University, Columbus, OH 43210
Computer Aided Assignment of Asymmetric Rotor Spectra (CAAARS)
Journal of Molecular Structure, 742, 1-3, 229http://www.physics.ohio-state.edu/~medvedev/caaars.htm
350300250200150Frequency/GHz
FASSST spectrum~50000 peaks
236.60236.55236.50236.45236.40Frequency/GHz
http://www.physics.ohio-state.edu/~medvedev/caaars.htm
238236234232230Frequency/GHz
FASSST Spectrum of Diethyl Ether
trans-gaucheb-type rQ10 branch
trans-transb-type rQ7 branch
4. Run the fitting and prediction programs to to make new predictions.
SPFIT/SPCAT ASFIT/ASROT
1. Make an initial prediction of the spectrum.
2. Search the experimental data for matching patterns.
5. Repeat steps 2, 3 and 4.
3. Update the assigned line list.
Steps of the assignment process:
trans-gauche diethyl ether b-type transitions
http://www.physics.ohio-state.edu/~medvedev/caaars.htm
Common parameters for a near prolate asymmetric rotor “branch”:
1. Transition type (a,b,c)
2. Ka
3. J
4. Ka
5. J - Ka- Kc (asymmetry component)
http://www.physics.ohio-state.edu/~medvedev/caaars.htm
Features of CAAARS Point and click approach to line assignment
The flexible sorting principle makes CAAARS applicable to a wide range of spectroscopic problems
The organization of the predicted and assigned lines into branches allows the user to plot easily Fortrat diagrams, intensity plots, R- or P-branch clusters, (Ka or Kc vs. frequency for a given J), errors, reduced energy plots, perturbed branch behavior, and whatever else is found useful for a given spectrum.
Assignment capabilities of CAAARS are enhanced with Loomis-Wood representation of spectra