Observation of Quantum Beat in Rb by Parametric Four-Wave Mixing

Two coupled parametric four-wave-mixing processes in Rb atoms are studied using perturbation theory, which reveals clear evidence of the appearance of quantum beat at 608cm^-1, corresponding to the energy difference of the 7s-5d states of Rb atoms, in the parametric four-wave-mixing signals. A pump--probe technique is utilized to observe the quantum beat. Time-varying characteristics of the quantum beat are investigated using time-dependent Fourier transform. The results show that the time-varying characteristics of the quantum beat not only offers a sensitive detecting method for observing the decay of atomic wave packets, but also provides a potential tool for
monitoring the dissociation of molecules.