Further Observations of Multiple-Quantum Transitions. Saturation Effects in Radio-Frequency Transitions

Multiple-quantum as well as the single-quantum transitions, $\Delta F=0\mathrm{}$, $\Delta m=\pm 1, 2, 3, 4$, have been observed in ${\mathrm{K}}^{39}$. In the neighborhood of the rf amplitude, required to give a maximum transition probability, the lines have the behavior predicted for transitions induced by a rectangular rf pulse. For higher rf amplitudes, the line width becomes constant or else decreases after having reached a maximum width, the line frequency is modified less rapidly than predicted and anomalous transition probabilities occur. All these effects are markedly dependent on the details of construction of the rf circuit in which transitions are induced. It is suggested that these effects may arise from the end regions of the circuit through an adiabatic traverse of the circuit by the atom.