Objective: Demonstrate electron spin resonance in DPPH
Electron spin resonance (ESR) is based on the energy absorption by substances with unpaired electrons, which are inside an external magnetic field produced by a DC source. The energy is absorbed from a high-frequency AC-generated field which is fed in perpendicular to the field from the DC source. If the frequency of the alternating field is equal to the resonant frequency, the impedance of the transmitting coil filled with the test material changes in accordance with a resonance curve and a peak will be visible on an oscilloscope screen. One suitable material for this is diphenyl-picry-hydrazyl (DPPH).