In this letter we study magnetic circular dichroism in alkali atoms exhibiting asymmetric behaviour of magnetically induced transitions. The magnetic field B ∥ k induces transitions between Δ F = ± 2 hyperfine levels of alkali atoms and in the range of ∼ 0.1 -- 3 kG 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 σ + than for σ − excitation for Δ F = + 2 , whereas it is several hundreds of thousand times larger in the case of σ − than that for σ + polarization for Δ 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 ( ∼ 50 MHz ). The presented theoretical curves well describe the experimental results. This effect can find applications particularly in parity violation experiments.
Magnetic field-induced symmetry breaking exhibited by explicit circular dichroism for
ΔF=±2 transitions of D
2 lines of all alkali atoms
In this letter we demonstrate universal symmetry breaking by means of magnetically induced circular dichroism. Magnetic field induces forbidden at zero field atomic transitions between
ΔF=±2 hyperfine levels. In a particular range of magnetic field, intensities of these transitions experience significant enhancement. We have deduced a general rule applicable for the
D2 lines of all bosonic alkali atoms, that is transition intensity enhancement is larger for the case of
σ+ than for
σ− excitation for
ΔF=+2, whereas it is larger (e.g. up to
1011 times for
85Rb atoms) in the case of
σ− than for
σ+ polarization for
ΔF=−2. This asymmetric behaviour results in an explicit circular dichroism. For experimental verification we employed half-wavelength-thick atomic vapor nanocells using a derivative of selective reflection technique, which provides sub-Doppler spectroscopic linewidth ($\sim$50 MHz). The presented theoretical curves well describe the experimental results. This effect can find applications particularly in parity violation experiments.