The existence of a novel resonance in the modulation of the fluorescen
ce light emitted by an atom or a molecule when coherently excited by a
rapidly rotating linearly polarized light beam is predicted. Such res
onances are experimentally observed due to a transfer of coherence fro
m light to atoms or molecules, via either stimulated emission or absor
ption of light, without having to shift the positions of the levels by
an external perturbation. These resonances directly permit the measur
ement of energy level lifetimes, even in the case where usual magnetic
resonance methods would require the use of large magnetic fields.