Physical Review Letters
Tri-Level Echoes
THOMAS W. MOSSBERG, Allen M. Flusberg, Ravinder Kachru, Sven R. Hartmann
Abstract
We report a new Doppler-free rephasing effect, the tri-level echo, which we use to study Ar-Na collisional relaxation of several $3^{2}S_{\frac{1}{2}}\ensuremath{-}n^{2}D_{\frac{3}{2}}$ superpositions in atomic Na. Three excitation pulses are required: The first resonantly excites a selected state, while the others resonantly couple this state with a higher-lying state. This sequence produces a delayed rephasing on the resonance transition which radiates strongly; the radiated intensity monitors relaxation in the higher-lying stepwise-excited state.