text: To perform a pulsed EDMR experiment, the system is first initialised by placing it in a magnetic field. This orients the spins of the electrons occupying the donor and acceptor in the direction of the magnetic field. To study the donor, we apply a microwave pulse ("γ" in the diagram) at a resonant frequency of the donor. This flips the spin of the electron on the donor. The donor electron can then decay to the acceptor energy state (it was forbidden from doing that before it was flipped due to the Pauli exclusion principle) and from there to the valence band, where it recombines with a hole. With more recombination, there will be fewer conduction electrons in the conduction band and a corresponding increase in the resistance, which can be directly measured. Above-bandgap light is used throughout the experiment to ensure that there are many electrons in the conduction band.
  By scanning the frequency of the microwave pulse, we can find which frequencies are resonant, and with knowledge of the strength of the magnetic field, we can identify the donors energy levels from the resonant frequency and knowledge of the Zeeman effect. The donors energy levels act as a fingerprint by which we can identify the donor and its local electronic environment. By changing the frequency slightly, we can study the acceptor instead.