title: Narrow resonances observed with nearly degenerate light in an open two-level system.
abstract: We report the observation of narrow resonances in the optical region by using the method of separated oscillatory fields in an atomic beam. Because of optical pumping, two nearly degenerate optical fields create a time-dependent modulation of the ground-state population, which interferes with the optical fields in a second region, resulting in a fringe pattern. The width and shape of the observed fringes are the same as those observed with the usual Ramsey method, although no coherence between the two levels under investigation is needed.
authors.forename: E
authors.initials: E
authors.lastname: Marega
authors.forename: V S
authors.initials: VS
authors.lastname: Bagnato
authors.forename: S C
authors.initials: SC
authors.lastname: Zilio