Theory of dark resonances for alkali-metal vapors in a buffer-gas cell

We develop an analytical theory of dark resonances that accounts for the full atomic-level structure, as well as all field-induced effects such as coherence preparation, optical pumping, ac Stark shifts, and power broadening. The analysis uses a model based on relaxation constants, which assumes the total collisional depolarization of the excited state. A good qualitative agreement with the experiments for Cs in Ne is obtained.