Electron spin resonance energy level splitting and microwave absorption

[RedDelicious]

Hello,

I am learning about electron spin resonance and I just want to see if my understanding is correct. From what I gathered, if you place a paramagnetic material in a magnetic field, the electron energy levels split, and when you then apply EM radiation (generally microwave frequency) that has an energy that's equal to the energy difference between the split, the electron spins will flip. The microwaves are absorbed only when this condition is met and so the different amounts of energy needed for different frequencies that are still in the general range is able to be determined.

Thank you,
RedDeclicious

 

[kuruman]

That is mostly correct. However, you don't know beforehand at what external magnetic field your fixed microwave frequency will match the unknown energy difference between electron levels. So the external magnetic field is ramped and from the value of the field that resonance occurs one can deduce the energy split.