Suppression and Enhancement in Parametric Two-Photon Resonant Nondegenerate Four-Wave Mixing via Quantum Interference

Quantum interference may lead to suppression and enhancement of
the two-photon resonant nondegenerate four-wave mixing signal in a cascade four-level system. Such phenomena are emonstrated in Ba through inducing atomic coherence between the ground state 6s² and the doubly excited autoionizing Rydberg state 6pnd. This method can be used as a new spectroscopic tool for measuring the transition dipole moment between two highly excited atomic states.