We report on the observation of novel Ramsey-type resonances due to collisional velocity diffusion in atomic samarium vapor in the presence of rare-gas perturbers. The experimental technique uses counterpropagating laser fields and relies on coherent resonance Raman processes to optically excite and detect sublevel coherence within the Doppler-broadened ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$ $\lambda =570.68\mathrm{}$-nm ${}_{}{}^7{}_{}{}^{}F_1^{}{}_{}{}^{}-{}_{}{}^7{}_{}{}^{}F_0^{}{}_{}{}^{}$ transition. The experimental findings are in good agreement with theoretical predictions based on a Fokker-Planck equation; time constants for the collisional thermalization of Sm in He and Ne atmospheres are derived from our data.

• Received 22 May 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.1300