Magnetically Induced Anomalous Dichroism of Atomic Transitions of the Cesium D-2 Line

Transitions F (e) - F (g) = Delta F = +/- 2 between the excited and ground levels of the hyperfine structure of the Cs D-2 atomic line in an external magnetic field of 300-3000 G have been studied for the first time with the use of sigma(+) and sigma(-) circularly polarized radiation. Selection rules forbid these transitions in zero magnetic field. At the same time, the probabilities of these transitions in a magnetic field increase significantly; for this reason, we refer to these transitions as magnetically induced transitions. The following rule has been found for the intensities of 24 magnetically induced F (g) = 3 -> F (e) = 5 and F (g) = 4 -> F (e) = 2 transitions: the intensities of magnetically induced transitions with Delta F = +2 are maximal (the number of such magnetically induced transitions is also maximal) in the case of sigma(+) polarized radiation, whereas the intensities of magnetically induced transitions with Delta F = -2 are maximal (the number of such transitions is also maximal) in the case of sigma(-) sigma(+) and sigma(-) polarized radiation can reach several orders of magnitude; i.e., anomalous circular dichroism is observed. For an experimental test, absorption spectra of a Cs-filled nanocell with the thickness equal to half the wavelength of resonant laser radiation = 852 nm have been analyzed in order to separately detect magnetically induced transitions. The experiment is in good agreement with the theory. Possible applications have been discussed.