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Model prediction vs measurement
Kinetic isotope effects predicted from a vibronic model
Predicted KIE
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Measured PCET kinetic isotope effects rarely exceed ∼10². A prediction
this large usually means the parameters push the model beyond what a real
hydrogen bond would sustain.
This runs in one direction only: parameters in, predicted observables
out. Read it as “a model with these parameters would give this KIE”.
It deliberately does not run backwards. A measured number that matches the
prediction does not establish the mechanism — many parameter sets give
the same KIE, as you can confirm by moving two sliders against each other.
Same vibronic model as the overlap app, with illustrative parameters.
Electronic coupling is fixed and cancels entirely from the isotope ratio.