Kerr dispersion of atomic sodium and lithium

Abstract

A detailed theory of the frequency dependence of the electro-optical Kerr effect of an atom in the region of absorption lines is presented and applied to the particular case of ² P←² S doublets of sodium and lithium vapours. Doppler broadening is taken into account. With electric dipole matrix elements derived from the Coulomb approximation for both discrete and continuum states, the molar Kerr constant, _m K(3² P←3² S), of atomic sodium vapour in the D-line absorption region is calculated to ±30 per cent; the calculations indicate that _m K in the vicinity of the D₂ line (3² P _3/2←3² S _1/2) should be very much greater than near the D₁ line (3² P _1/2←3² S _1/2) in qualitative agreement with the experiments of Kopfermann and Ladenburg Qualitative consideration is also given to dispersion of magnetic birefringence; in contrast with electric birefringence strong dispersion is expected near both lines of alkali metal ² P←² S doublets.