Low Frequency Resonances in the Spectra of Diatomic Molecules

The molecular beam magnetic resonance method has been used in the study of some previously unobserved resonances in NaF, NaCl, NaBr, NaI, and KBr. The frequency and intensity distribution within the resonance spectra have been studied at zero external field and the dependence of both the frequency and the shape of the resonance spectra on external magnetic field has been determined. At zero field these resonances fall in the frequency range from 0 to 157 kc and occur because of a quadrupole interaction and from a cosine interaction between $I$ and $J$. At sufficiently high field, the frequency of the maxima of the resonances is $\frac{2g_I{\mu }_{0}H}{h}$. The lines are ascribed to a transition between the levels $F=J+\frac{1}{2}$ and $F=J-\frac{1}{2}$. In most respects the lines fulfill theoretical predictions; the frequencies of the lines at zero magnetic field, however, deviate considerably from those predicted from other data.