Collisional Narrowing of a Fine-Structure Raman Transition

The line shape of the Raman transition between metastable levels of neon (${}_{}{}^3{}_{}{}^{}p_0^{}{}_{}{}^{}\mathrm{and}{}_{}{}^3{}_{}{}^{}p_2^{}{}_{}{}^{}$) is studied as a function of the pressure of a helium buffer gas. Dicke narrowing of the Doppler-broadened nonresonant Raman signal (for large optical detunings) gives the first evidence of conservation of a fine-structure coherence by velocity-changing collisions. Pressure broadening of the resonant Raman signal gives a measurement of the velocity-changing-collision rate.