Magnetic Resonance for Nonrotating Fields

Abstract

A treatment of the magnetic resonance is given for a particle with spin \textonehalf{} in a constant field ${H}_{0}$ and under the action of an arbitrary alternating field with circular frequency $\ensuremath{\omega}$ perpendicular to ${H}_{0}$. A method of finding a solution, valid at any time, is given which converges the better the smaller the deviations from a rotating field or the larger ${H}_{0}$. It is shown that in the lowest order correction the shape of the resonance curve is unchanged but that it is shifted by a percentage amount $\frac{{{H}_{1}}^{2}}{16 {{H}_{0}}^{2}}$ where ${H}_{1}$ is the effective amplitude of the oscillating field. This also involves a correction in the values of the magnetic moments thus obtained towards smaller values which however in all practical cases is negligibly small.