Relativistic Corrections in a Series of Helium Excited States

The irnportance of relativistic and radiative corrections in atomic and molecular systems bas been emphasïzed by several authors [1,2] _ The usual point of departure has been the Breit equation [3], a generahzation of the Dirac equation representing two relativistic particles in an external fïeId. This theory is beheved to be correct to terms of order (v/c)~. In this paper we propose to calculate relativistic corrections for a series of excited states in helium. Thïs work is motivated in part by tbe high precision to which these energy Ievels are now known approaching one part in ten mïllion. The sequence of excited states 1~2~2 !a3P, Is3d3 ls3D, ls4f4 IJF,___ is attractive from a theoretical point of view in tbat these represent the lowest states of their respective symrnetry types_ Thus the simplest farm of the variational prïnciple is applicable. Moreover, the non-relativistic electron correlation problem is expected to be minima& particularly for the higber states in tbe sequence.