Unexpectedly large difference of the electron density at the nucleus in the 4p2 P1/2,3/2 fine-structure doublet of Ca+
C. Shi, F. Gebert, C. Gorges, S. Kaufmann, W. Nörtershäuser, B. K. Sahoo, A. Surzhykov, V. A. Yerokhin, J. C. Berengut, F. Wolf, J. C. Heip, and P. O. Schmidt
http://link.springer.com/article/10.1007%2Fs00340-016-6572-z