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

Computer Aided Assignment of Asymmetric Rotor Spectra (CAAARS)

assignment window

Branch selection

Branch selection

Loomis-Wood diagram

Loomis-Wood diagram

Spectral assignment

Spectral assignment

Execution of the Fitting and Prediction Programs

Execution of the Fitting and Prediction Programs

Loading of the New Predictions

Loading of the New Predictions

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

Journal of Molecular Structure, 742, 1-3, 229http://www.physics.ohio-state.edu/~medvedev/caaars.htm