Circular Dichroism of Atomic Transitions of the Rb D-1 Line in Magnetic Fields

The circular dichroism effect has been investigated for atomic transitions of the Rb D-1 line in magnetic fields of up to 3 kG using circularly polarized sigma(+) and sigma(-) 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 (Rb-85 atoms) and four (Rb-87 atoms) transitions are formed in magnetic fields B > 0.5 kG upon sigma(+) and sigma(-) laser excitation. All transitions have been identified. It is shown that the strongest transitions for Rb-87 and Rb-85 atoms in magnetic fields of up to several kG are formed under sigma(-) 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 sigma(+) and sigma(-) excitation become identical. The theoretical model and experiment are in good agreement.