In EPR, what does a higher frequency indicate when an electron is ejected?

In Electron Paramagnetic Resonance (EPR), a higher frequency correlates with an increased energy transition of the electrons involved in the process. When an electron is ejected and the energy associated with that ejection is higher, this can suggest that the electron was removed from an anti-bonding orbital.

Anti-bonding orbitals are higher in energy compared to bonding orbitals. Consequently, when an electron transitions out of an anti-bonding orbital due to the application of microwaves in EPR, it requires a significant amount of energy to overcome the stability imparted by the bonding interactions in the molecule. This is why the frequency of the applied radiation is higher for transitions involving electrons from anti-bonding orbitals.

In contrast, electrons from bonding orbitals would generally require lower energy transitions, leading to lower frequency emissions. Therefore, the association of higher frequency with electrons coming from an anti-bonding orbital is valid due to the energetic considerations and the inherent stability of such orbitals in the electronic structure of molecules.