Approach towards the critical charge of some excited states of the Be isoelectronic series.

A definitive determination of the nature of the approach to the critical charge is illustrated for the (1S²2S3S)1,3 S and the (1S²2S3p)1,3P states of the Be isoelectronic series. The features that conclusively indicate that the outermost orbital becomes an infinitely diffuse hydrogenlike orbital upon approaching the critical charge Zc = 3 are the asymptotic proportionality of the ionization energy to (Z -- 3)² and the approach of the corresponding quantum defect to an integer which is equal to the number of orbitals of the same symmetry in the atomic core. [ABSTRACT FROM AUTHOR]