MULTIQUANTUM ELECTRON-PARAMAGNETIC-RESONANCE TRANSITIONS EXCITED IN A2-LEVEL SYSTEM BY TETRACHROMATIC MICROWAVE IRRADIATION

A method to excite multiquantum transitions in a two-level system by a pplication of continuous irradiation with a four-frequency microwave f ield is presented. The generated signal is composed of many intermodul ation sidebands at different frequencies, which arise from the multiqu antum transitions. These processes involve an odd number of photons, t hat are absorbed from, or emitted to two, three, or four fields. The c orrespondence between the frequency spectrum of the signal and possibl e pathways of multiquantum processes is found with recourse to the man y mode Floquet theory. The reported experiments demonstrate the multiq uantum origin of the detected intermodulation sidebands and their prop erties. (C) 1998 American Institute of Physics. [S0021-9606(98)01345-2 ].