Theory of dark resonances for alkali atom vapors in a buffered cell

Summary form only given. We develop a new analytical theory, which takes into account the full atomic level structure (both Zeeman and hyperfine) as well as all field-induced effects such as coherence preparation, optical pumping, ac Stark shifts, and power broadening. The crucial assumption is the total collisional depolarization in the excited state. In addition, we add the (optional) approximations of homogeneous broadening and low-saturation. With these approximations, we get a quite general analytical result for the atomic response, which holds for arbitrary excitation schemes (D2 as well as D1 lines), field polarizations, and magnetic field directions. Specifically, in the case of sufficiently large magnetic field, when only two states participate in the coherence preparation, analytical lineshapes coincide exactly with the Lorentz-Lorentz model heuristically introduced to fit experimental data.