125Te NMR in TeO2 single crystal: Te–Te chemical bonding and tunneling of 5s2 electrons

The Te–O and Te–Te bonds in TeO2 have been studied from 125Te NMR single crystal data. The 125Te NMR chemical shift tensor has principal components δ11=727.5, δ22=1586.2 and δ33=2065.8 ppm. The 125Te magnetic shielding tensor is represented as a sum of constituents characterising the off-ionic parts of the separated Te–Te and Te–O interactions. It is shown that the Te–Te exchange interaction is associated with a strong polarization of the Te4+ ion under the intramolecular electric field and with tunneling of 5s2 electrons along the Te–Te bonds.