Multiquantum nutation in two-level spin systems

R. Boscaino, F. M. Gelardi, G. Messina

R. Boscaino, F. M. Gelardi, Rosario N. Mantegna

Jacques M. Courtieu, Nguyen Thoi Lai, Larry G. Werbelow

V. P. Belavkin

Г. Г. Федорук

Two-photon transient nutation is observed in a two-level spin system ( E ′ 1 centers in crystalline quartz) using a transverse microwave field and a linearly polarized rf field oriented along a static magnetic field in the electron paramagnetic resonance. Nutation is excited when the sum of the energies of a microwave photon and a rf photon is equal to the energy difference between two spin states. The two-photon nature of nutation is confirmed by measuring its frequency as a function of the amplitude and frequency of the rf field as well as the amplitude of the microwave field. The amplitude of the effective field of two-photon transitions is measured. It is shown that the decay rate of two-photon nutation is close to the decay rate for one-photon nutation and is determined by the spin-spin interaction between E ′ 1 centers.

Małgorzata Jeleń, Wojciech Froncisz

A method to excite multiquantum transitions in a two-level system by application of continuous irradiation with a four-frequency microwave field is presented. The generated signal is composed of many intermodulation sidebands at different frequencies, which arise from the multiquantum transitions. These processes involve an odd number of photons, that are absorbed from, or emitted to two, three, or four fields. The correspondence between the frequency spectrum of the signal and possible pathways of multiquantum processes is found with recourse to the many mode Floquet theory. The reported experiments demonstrate the multiquantum origin of the detected intermodulation sidebands and their properties.