Effect of the buffer gases on the light shift suppression possibility.

We theoretically and experimentally demonstrate that the light shift of the coherent population trapping resonance frequency depends on the buffer gases pressure. The light shift suppression becomes impossible when a certain value of the buffer gases pressure is exceeded. We estimate the minimal dimensions of an atomic cell at which the zero light shift and the lowest ground-state relaxation rate can be achieved simultaneously. A new technique of the light shift cancellation by means of a feedback utilizing the RF power modulation is proposed.