Zamudio-Bayer, V.; Hirsch, K.; Langenberg, A.; Niemeyer, M.; Vogel, M.; Lawicki, A.; Terasaki, A.; Lau, J.T.; Von Issendorff, B.: Maximum Spin Polarization in Chromium Dimer Cations as Demonstrated by X-ray Magnetic Circular Dichroism Spectroscopy. Angewandte Chemie - International Edition 54 (2015), p. 4498-4501
10.1002/anie.201411018
Open Access Version (externer Anbieter)
Abstract:
X-ray magnetic circular dichroism spectroscopy has been used to characterize the electronic structure and magnetic moment of Cr2+. Our results indicate that the removal of a single electron from the 4sσg bonding orbital of Cr2 drastically changes the preferred coupling of the 3d electronic spins. While the neutral molecule has a zero-spin ground state with a very short bond length, the molecular cation exhibits a ferromagnetically coupled ground state with the highest possible spin of S=11/2, and almost twice the bond length of the neutral molecule. This spin configuration can be interpreted as a result of indirect exchange coupling between the 3d electrons of the two atoms that is mediated by the single 4s electron through a strong intraatomic 3d-4s exchange interaction. Our finding allows an estimate of the relative energies of two states that are often discussed as ground-state candidates, the ferromagnetically coupled 12Σ and the low-spin 2Σ state.