EPR Flashcards
Spectroscopy
Measurement and interpretation of energy differences between discrete states of atoms/ molecules
EPR
Electron paramagnetic receptor
Another name for UV/ visible spectroscopy
Electronic absorption spectroscopy
Which electromagnetic processes are in a magnetic field
NMR and ESR (electron spin resonance aka EPR)
What is EPR
Measurement and interpretation of energy differences between two states of paramagnet when in a magnetic field
Paramagnet
Atom or molecule with an unpaired electron spin
Zeeman effect
When paramagnet in magnetic field, magnetic moment will allign with magnetic field (low energy state) or against magnetic field (high energy)
What happens when energyis absorbed in EPR
Converts low energy state to high energy state - corresponds to that of the microwave photon
WHat determines the energy separating the magnetic field
Strength of magnetic field
What happens with the microwave radiation in EPR
Kept constant (fixed frequency) while magnetic field strength is swept - when energy difference matches energy of microwave radiation, absorption occurs = RESONANCE
Why is a first derivative of absorption necessary to do
Usually EPR signals are very wide
What temp do you use for EPR
Liquid nitrogen (low temp - bigger chance to see broad signals)
L band
Low resolution, resonates at 30cm - 1GHz frequency
Where can unpaired electrons be found
Free radicals, triplet states, metals and metal ions
Organic radicals
Substrate radicals, tetrapyrols, quinones, flavins, amino acids
