Relativistic effects on line strengths for transitions in the hydrogenic isoelectronic sequence

R e la ti vis ti c lin e s tre ngth s have bee n co mllU te d fo r a la rge num be r of tra ns iti on s u s in g Dirac wav e fun c t io ns for th e u ne-e lec tro n , h ydruge n-lik e io ns .As ex pec te d .th e res ults in d ica te th a t re la t ivi s ti c e ffect s a re qUlt es m a ll fo r l.ow s ta ges of io ni zatio n .Howe ve r , in ge n e ral , th ey a lso re ma in s m aJi thro ugho ut ,~ la rge p orti o n of th e Isoelec tro nlc sequ e nce, beco min g t yp ica ll y of th e ord e r u f 10 pe rce nt in th e vIc init y of Z =50,.a ft e r whi c h th ey gro w quit e rap idl y.T hi s s ugges ts th a t fo r multi e lec tro n io ns a b asica ll y no n re la ti vis ti c th eo ry mi g ht we ll b e a d e q ua te fo r li ght a to m is ue lec t ro ni c iu n s t h ro u" h as mu c h as 30 o r 40 s tages of io ni za ti o n. " Key word s : Dirac th eo ry ; h ydroge n ; lin e s t re n gth ; osc ill a to r s tre ngth ; re la ti vis ti c c o rrecti o ns ' s p ect ro sco py.' * S u p po rted by Energy Researc h and Develo pm e nt Admi nistration.** Pe rma ne nt address : U n iVPfl'i l V of Ma rvla nd.Co ll ege Pa r k, l\' ld .20740., Fi gures in b rac kets ind ic a te t he li t eratu-re re lere nces.