A Density Matrix Treatment of Atomic Line Radiation

Abstract

Since the early days of quantum mechanics, the theory of atomic line radiation has been of central interest in atomic physics. Percival and Seaton¹ presented a general treatment of the subject that has been widely used by both experimentalists and theoreticians. They briefly review the “Oppenheimer-Penney (O.-P.) theory of polarization” and later criticize it for not satisfying the “principle of spectroscopic stability”. This principle requires, for example, that results obtained in a ∣J,M coupling scheme involving the total electronic angular momentum J and its component M _j with regard to a specified quantization axis, must be identical to those obtained in an ∣L,M coupling scheme (where L and S are the orbital and spin angular momenta with components M _L and M ₅ in the limit of vanishing fine-struct ure splitting in the target states. A similar argument can be made for hyperfine-structure effects due to a non-vanishing nuclear spin of the target.