The problem of theoretical analysis of complex spectra is outlined with attention to various methods available for the computation of the Russell-Saunders wave functions, which form a basis for most other computations. In order to investigate intensity anomalies due to interconfiguration perturbations in two electron spectra, the non-diagonal matrix elements of the electrostatic interaction, between states describable by L-S wave functions, are computed by the symbolic “spinor” formulation of Weyl's group theory as developed by Kramers and Brinkman. A closed expression is obtained which embodies the results of what would be in the Schrodinger method a sum of integrals over angular wave functions; the radial integrals are still to be evaluated. A neat graphical method for computing the radial integrals, providing Slater's approximation to the Hartree wave functions can be used, is worked out.
Transition intensities are computed using this configuration interaction, and the effect of introducing as well that of the spin-orbit term is investigated. Formulae are derived which show that the first-order term in absolute intensity anomalies is due to the interconfiguration electrostatic term alone, which however leaves relative intensities within a given multiplet transition unaffected. The first-order correction term in the latter (second-order term for absolute intensities) depends upon a product of factors depending on the electrostatic and spin-orbit interactions respectively.
