Role of d$^{\mathrm{n-1}}$s configurations in hyperfine structure (hfs) of d$^{\mathrm{n}}$ levels in transition metal atoms and ions: Application to V II

Independent particle calculation of the hfs of d$^{\mathrm{n}}$ levels in transition metal atoms can lead to serious errors when there are nearby d$^{\mathrm{n-1}}$s levels. These errors can only be corrected when the latter levels are properly mixed into the d$^{\mathrm{n}}$ wave-functions along with, e.g. the usual hfs single excitations [1]. Recently hfs of 25 V II levels has been measured [2] and there is substantial disagreement with 4 of 8 previously measured hfs [3]. Preliminary RCI calculations [4] support the newer work [2].\\[4pt] [1] D.R. Beck, Phys.Rev. A45,1399 (1992).\\[0pt] [2] N.M.R. Armstrong et al, Phys.Scr.84,055301 (2011).\\[0pt] [3] K. Arvidsson, M.S. thesis, Lund Observatory (2003).\\[0pt] [4] M. Abdalmoneam and D.R. Beck, manuscript in preparation.