  Light induced non-equilibrium spin noise spectroscopy is theoretically and
experimentally shown to be an efficient technique to reveal the structure and
the coherent effects in the probed transition. Indeed, using metastable helium,
the spin noise spectrum is shown to exhibit a dual-peak structure around the
Larmor frequency. This previously unobserved feature is due to the light shifts
of the involved levels and strongly depends on the probe power, detuning, and
polarization orientation. Both numerical and analytical models reproduce very
well the details of the split spin noise spectra: this technique thus allows a
simple and direct measurement of the light shifts, and its polarization
dependence permits to reveal the level structure in a non ambiguous manner.
