A PROGRAMME FOR CALCULATING ATOMIC STRUCTURES

A method for calculating atomic structures, suitable for the electronic computer, is outlined; the method allows for configuration interaction in a very general way. It is based on the expansion of wave functions in terms of Slater states. All relativistic interactions are disregarded and an SL coupling scheme is used. The number of terms SL considered is that resulting from all configurations included; the configurations are the only input apart from the nuclear charge Z. The energy matrix is expressed in terms of radial integrals with purely algebraic coefficients. A scheme is described for computing these coefficients. The integrals are evaluated using radial wave functions calculated in a scaled Thomas-Fermi potential. Numerical examples for Na I and Mg I isoelectronic sequences are given. Layzer pointed out the importance of configuration interaction within a complex; his predictions for stages of high ionization are confirmed. It is shown that for stages of medium or low ionization interaction with configurations belonging to other complexes can become important.