Field Dependence of Mobility in p-Type Germanium

Pulsed EPR investigations of systems modeling molybdenum enzymes: hyperfine and quadrupole parameters of oxo-17O in [Mo 17O(SPh)4]-

Ka band ESEEM spectroscopy was used to determine the hyperfine (hfi) and nuclear quadrupole (nqi) interaction parameters for the oxo-17O ligand in [Mo 17O(SPh)4]-, a spectroscopic model of the oxo-Mo(V) centers of enzymes. The isotropic hfi constant of 6.5 MHz found for the oxo-17O is much smaller than the values of approximately 20-40 MHz typical for the 17O nucleus of an equatorial OH(2) ligand in molybdenum enzymes. The 17O nqi parameter (e2qQ/h = 1.45 MHz, eta approximately = 0) is the first to be obtained for an oxo group in a metal complex. The parameters of the oxo-17O ligand, as well as other magnetic resonance parameters of [Mo 17O(SPh)4]- predicted by quasi-relativistic DFT calculations, were in good agreement with those obtained in experiment. From the electronic structure of the complex revealed by DFT, it follows that the SOMO is almost entirely molybdenum d(xy) and sulfur p, while the spin density on the oxo-17O is negative, determined by spin polarization mechanisms. The results of this work will enable direct experimental identification of the oxo ligand in a variety of chemical and biological systems.

The influence of interelectronic collisions on conduction and breakdown in polar crystals

The variation of the electron mobility with an increasing applied field and also the collective dielectric breakdown field, are calculated assuming that interelectronic collisions are sufficiently frequent to determine the energy and momentum distributions of the electron gas. At high temperatures a small increase (by a factor less than 2) and at low temperatures a large decrease (by a factor greater than 10) in the mobility should be observed as the field approaches the breakdown value. It is also shown that the mobility variation at high temperatures will be substantially the same if interelectronic collisions are not predominant, but at low temperatures there will be no variation at all. The application of these results to semi-conductors where the electron scattering mechanism is uncertain is discussed with special reference to indium antimonide.