Responses of multiple quantum coherences to a double resonant irradiation

Abstract

The responses of a prepared multiple quantum (MQ) coherence, initially prepared in AX 2 and AX 3 spin systems, to a double resonant irradiation, are studied in this paper. The experiments demonstrate that the response spectra depend on the field strength of this irradiation. The response spectrum of a given multiple quantum coherence, contained all possible transitions in the system, including both the MQ and the single quantum (SQ) transitions in a rather strong irradiation, which was comparable with J, the coupling constant of the system. However, when the irradiation was weak, the response spectrum contained only these MQ transitions, up to the very order of this specific MQ coherence initially prepared, in addition to the unavoidable SQ transitions in the system. Theoretical analysis, based on a novel formalism of product operator, agreed well with the experiments, qualitatively.