Magic frequencies for probing of the density matrix

We analyze theoretically and demonstrate experimentally the existence of a magic frequency for which the absorption of a linearly polarized light beam by a vapor of alkali metal atoms is independent of the population distribution among the Zeeman sublevels and the angle between the beam and an external magnetic o eld which defines the quantization axis From a fundamental point of view the magic frequency represents a unique cancellation of the contributions of higher moments of the atomic density matrix to light absorption so that light matter inter