Circular dichroism of magnetically induced transitions for D-2 lines of alkali atoms

In this letter we study magnetic circular dichroism in alkali atoms exhibiting asymmetric behaviour of magnetically induced transitions. The magnetic field B parallel to k induces transitions between Delta F = +/- 2 hyperfine levels of alkali atoms and in the range of similar to 0.1-3kG magnetic field, the intensities of these transitions experience significant enhancement. We have inferred a general rule applicable for the D-2 lines of all alkali atoms, that is the transition intensity enhancement is around four times larger for the case of sigma(+) than for sigma(-) excitation for Delta F = +2, whereas it is several hundreds of thousand times larger in the case of sigma(-) than that for sigma(+) polarization for Delta F = -2. This asymmetric behaviour results in circular dichroism. For experimental verification we employed half-wavelength-thick atomic vapor nanocells using a derivative of the selective reflection technique, which provides a sub-Doppler spectroscopic linewidth (similar to 50 MHz). The presented theoretical curves well describe the experimental results. This effect can find applications particularly in parity violation experiments. Copyright (C) EPLA, 2018