Rate Constants from QET

Note Thermodynamic data such as heats of formation and activation energies alone are not sufficient to adequately describe the unimolecular fragmentations of excited ions. 

QET brings the dynamic aspects of ion fragmentation into focus. It describes the rate constants for the dissociation of isolated ions as a function of internal energy, Eiiit, and activation energy of the reaction, Eq. By doing so, it compensates for the shortcomings of the merely thermodynamic treatment above. 

QET delivers the following expression for the unimolecular rate constant 

the exponent is given by the number of degrees of freedom, s, minus 1 for the breaking bond. For a strict treatment of fragmenting ions by QET one would need to know the activation energies of all reactions accessible and the probability functions describing the density of energy levels. 

In the most simplified form, the rate constant, fc(E), can be expressed as 

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