Subsidiary resonances in nuclear magnetic resonance

Abstract

In addition to the main resonance line at ω0, resonances at 0, 2ω0, 3ω0, etc. are possible in solids, owing to the nuclear dipolar interactions. Standard texts predict the main field dependence of both the 2ω0 and 3ω0 lines to be (HL/H0)2, where HL is the local dipolar field. In this paper the problem of the field dependence of the 2ω0 and 3ω0 lines is investigated along conventional lines and shown to be (HL/H0)2 and (HL/H0)4 respectively. These relationships are verified by means of low-field (10-50 G) experiments, utilizing an adiabatic demagnetization procedure. The measurements, on a sample of methyl anthracene which were carried out at room temperature, also confirmed the expected radio frequency field dependence of the transitions.