Circular Dichroism of Atomic Transitions of the Rb D1 Line in Magnetic Fields

The circular dichroism effect has been investigated for atomic transitions of the Rb D1 line in magnetic fields of up to 3 kG using circularly polarized σ+ and σ− radiation. The process of selective reflection from a 350-nm-thick nanocell has been used, which makes it possible to form narrow atomic lines and observe separately the behavior of individual transitions. Two groups consisting of six (85Rb atoms) and four (87Rb atoms) transitions are formed in magnetic fields B > 0.5 kG upon σ+ and σ− laser excitation. All transitions have been identified. It is shown that the strongest transitions for 87Rb and 85Rb atoms in magnetic fields of up to several kG are formed under σ− irradiation. A further increase in the magnetic field makes it possible to attain the Paschen–Back regime on a hyperfine structure, for which the probabilities of transitions upon σ+ and σ− excitation become identical. The theoretical model and experiment are in good agreement.