Multiple Quantum Transitions in Paramagnetic Resonance

At high rf fields the normal paramagnetic resonance spectrum of ${\mathrm{Mn}}^{++}$ in cubic MgO is found to be modified by the appearance of additional absorption lines which occur at the frequencies: $\frac{(E_k-E_{k-2\mathrm{}})}{2h}$. These are interpreted as double quantum transitions ($\Delta M=2\mathrm{}$) which occur between nearly equally spaced energy levels at high rf power. The transitions $M=-\frac{3}{2}\to +\frac{1}{2}$ and $M=-\frac{1}{2}\to \frac{3}{2}$ have been observed at both room and liquid nitrogen temperatures for a number of orientations of the crystal with respect to a dc magnetic field of 3400 oersteds. At 77°K evidence of the triple quantum transitions $-\frac{1}{2}\to \frac{5}{2}$, $-\frac{5}{2}\to \frac{1}{2}$ was observed.