Electron spin resonance(ESR).

Since electrons possess spin,they behave as spinning magnets and so will tend to orient themselves in an applied magnetic field. The spin of one election of a covalant pair and its interaction with a magnetic field is cancelled by the equal and opposite spine of its partner.An unpaired electron,however, will have an interaction that is not cancelled out.If a molecule contains only one unpaired electron, then the spin number can be either +1/2 -1/2. Thus there are only two orintations possible,