Knowledge Bank

When dealing with non-closed shell states the evaluation of correlation effects peculiar to the system is vital in the theoretical prediction of various excited states as well as of transitions from ground states. This work deals with first row atoms and their ions. The levels of $\mathrm{<mrow\; data-mjx-texclass="ORD">5</mrow>}S--1S$ state of the carbon isoelectronic series and the relative positions of excited multiplets are obtained. The anomolous behavior of the correlation energy in the ionization process of inner shell electrons of rare gas atoms is resolved by the evaluation of the non-closed effects in the resultant excited states, allowing one to obtain ionization energies of inner shell electrons theoretically.