A generalization of the equations of the self-consistent field for two-electron configurations

The most successful general method so far devised for dealing with many- electron atoms is th a t of the self-consistent field (abbreviated in what follows to “ s. c. f.” ). If greater accuracy is required than is obtainable with the method as ordinarily used (either with or without exchange), either the so-called “ configuration interaction ” must be taken into account —usually a very laborious procedure—or else more complicated (variational) methods must be used, which must be designed separately for each particular case, and in which the concept of each electron being assigned to its own “ orbit” is usually abandoned. It would seem desirable, therefore, to have, if possible, somegeneral method which will increase the accuracy of the calculations without taking into account configuration interaction, and which will still allow the conceptual features of the s. c. f. method (i. e. the assignment of “ orbits” ) to be retained. In this paper such a method is developed for the case of two-electron configurations in Russell-Saunders coupling. The method consists in assuming a form for the wave function which is similar to that used in the s. c. f. method, except that the proper spatial symmetry is allowed for (which is not so in the case of the s. c. f. equationswithout exchange), and further, an adjustable function of Θ, the angle between the radii vectores to the two electrons, is inserted as a multiplying factor. The usual variational method is then applied, and yields differential equations for the two radial functions which are similar to those of the ordinary theory, together with an equation for the angular function.