Abstract
It is pointed out that the technique used by Dicke and Romer of pulse excitation of a volume of gas to a coherently radiating state can be applied to high-resolution spectroscopy using molecular beams. A two-cavity maser-like system without a state separator is proposed, where the molecular beam is polarized by a pump field in the first cavity and the coherent spontaneous emission radiated in a second pick-up cavity detected by a superheterodyne receiver.