Buffer-gas effects on dark resonances: Theory and experiment - art. no. 043813

Dark resonances with widths below 30 Hz have been observed in a rubidium ce ll filled with neon as buffer gas at room temperature. We compare an approx imate analytic solution of a Lambda system to our data and show that under our experimental conditions the presence of the buffer gas reduces the powe r broadening of the dark resonances by two orders of magnitude. We also pre sent numerical calculations that take into account the thermal motion and v elocity-changing collisions with the buffer-gas atoms. The resulting dark-r esonance features exhibit strong Dicke-type narrowing effects and thereby e xplain the elimination of Doppler shifts and Doppler broadening, leading to observation of a single ultranarrow dark line.