Zamudio-Bayer, V.; Lindblad, R.; Bülow, C.; Leistner, G.; Terasaki, A.; von Issendorff, B.; Lau, J. T.: Electronic ground state of Ni2+. The Journal of Chemical Physics 145 (2016), p. 194392/1-7

The Φ9/24 ground state of the Ni+2 diatomic molecular cation is determined experimentally from temperature and magnetic-field-dependent x-ray magnetic circular dichroism spectroscopy in a cryogenic ion trap, where an electronic and rotational temperature of 7.4±0.2 K was reached by buffer gas cooling of the molecular ion. The contribution of the spin dipole operator to the x-ray magnetic circular dichroism spin sum rule amounts to 7Tz=0.17±0.06μB per atom, approximately 11% of the spin magnetic moment. We find that, in general, homonuclear diatomic molecular cations of 3d transition metals seem to adopt maximum spin magnetic moments in their electronic ground states.