Experimental Observation of Constructive Quantum Interference via Hybrid Excitation in an Na₂-Na System

We report on an experimental observation of constructive quantum interference between two atomic transition pathways 3P_1/2-5S (or 4D) and 3P_3/2-5S (or 4D) via equal-frequency hybrid excitation and collision-aided radiative excitation in an Na₂-Na system. Through the special excitation processes, constructive quantum interference is realized for a Λ-type quantum-beat configuration with a widely-spaced doublet (about 17 cm^-1) in the excited sodium atom driven by one laser. The dependences of quantum interference on the argon buffer gas pressure and sample temperature are also examined.