Q&A_QEC: Pseudo and real resonances

Q: How to distinguishes between a real resonance and pseudo resonance in QuantemolEC results?

A: The resonance parameters are produced as a part of the #QuantemolEC output, based on RESON module results. Read more about RESON here: Tennyson, J., & Noble, C. J. (1984). “RESON – A program for the detection and fitting of Breit-Wigner resonances“. Computer Physics Communications, 33(4), 421–424).

The key aspect to look out for is the resonance energy. Pseudo resonances appear at an energy above the first excited stated omitted from the calculation.

This means for the calculation done at the Static Exchange with Polarisation level pseudo resonances will be above the first excited state.  

For the calculation done at Close Coupling level pseudo resonances will appear above ionization (or a little below that).

There, of course, could be real resonances at these energies but is less likely.

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