Spin absorption of solids

A study of the spin absorption lines of all orders was made. Rules for obtaining the absorption operator of any line were found. With magnetic dipole-dipole and exchange interactions taken into account, and with the assumption that the Zeeman energy is dominant, the zeroth and the second moments of the following four lines were evaluated for powders: (1) first Larmor line, parallel field, (2) second Larmor line, parallel field, (3) second Larmor line, perpendicular field, (4) low-frequency line, perpendicular field. The contribution of exchange to the second moment was found to be the same for the four cases treated, while the total intensity has the ratio 1:1:1:3/2. Agreement with existing experimental data is good.