Dipolar Broadening of the Central Line of a Magnetic Resonance for Half-integral Spin

The second moment of the central line of a magnetic resonance for half-integral spins, for which quadrupole coupling (nuclear spin case) or crystalline field effect (electronic spin case) is present, is calculated by the Van Vleck procedure. The interactions between like spins, unlike spins and semi-like spins are considered separately. The results are compared with the Van Vleck results for which no quadrupole coupling or crystalline effect is assumed.