ENDOR of H- and D- compensated tetragonal Ce3+ centres in CaF2

Lanthanide Ions as Local Probes in Ionic Hydrides: A Pulsed Electron Nuclear Double Resonance and Thermoluminescence Study of Eu2+-Doped Hydride Perovskites

“…Moreover, the obtained negative isotropic hfc’s indicate likewise that there is no indication of a direct spin density transfer from the 4f europium orbital to the atomic s hydride orbitals and the corresponding σ-type bonding contributions are negligible. We propose that the negative isotropic hfc’s result from the core polarization of europium 5p and 5s orbitals and their overlap with the filled 1s hydride orbitals …”

“…Consequently, the wave function of the unpaired electrons are highly localized at the Eu 2+ ion, and the application of the point dipole–dipole approximation seems to be justified. Even for the next-neighbored H – or D – , the formation of a π-type bonding with the Eu 2+ ion cannot be expected, as there are only s electrons available at the hydrides, and therefore, their anisotropic hfc with the lanthanide ion shall be of exclusively dipolar nature. Moreover, the obtained negative isotropic hfc’s indicate likewise that there is no indication of a direct spin density transfer from the 4f europium orbital to the atomic s hydride orbitals and the corresponding σ-type bonding contributions are negligible.…”

“…However, the cw EPR approach did not allow for a clear distinction of the type of surrounding atoms and, consequently, an unambiguous identification of the Eu 2+ incorporation site in these hydrides. A well-established technique for obtaining more detailed information is electron–nuclear double resonance (ENDOR), , which was, for instance, used to resolve the interaction of the paramagnetic vanadyl ion (VO 2+ ) with the surrounding nuclei. , But even though ENDOR has proven to be a very useful tool for studying Eu 2+ -doped halides, − as well as charge compensation by the introduction of hydride anions in the local environments of trivalent Nd 3+ and Ce 3+ centers in CaF 2 , , to the best of our knowledge, it has never been used to study interactions of the paramagnetic Eu 2+ ions incorporated at divalent lattice sites in a hydride material.…”

“…We propose that the negative isotropic hfc's result from the core polarization of europium 5p and 5s orbitals and their overlap with the filled 1s hydride orbitals. 44 Thermoluminescence Spectroscopy. Thermoluminescence spectroscopy is often employed to study the charge traps in a material.…”