Threshold electronic structure at the oxygen K edge of 3d transition metal oxides: a configuration interaction approach

It has been generally accepted that the threshold structure observed in the oxygen K edge X-ray absorption spectrum in 3d transition metal oxides represents the electronic structure of the 3d transition metal. There is, however, no consensus about the correct description. We present an interpretation, which includes both ground state hybridization and electron correlation. It is based on a configuration interaction cluster calculation using a MO6 cluster. The oxygen K edge spectrum is calculated by annihilating a ligand hole in the ground state and is compared to calculations representing inverse photoemission experiments in which a 3d transition metal electron is added. Clear differences are observed related to the amount of ligand hole created in the ground state. Two "rules" connected to this are discussed. Comparison with experimental data of some early transition metal compounds is made and shows that this simple cluster approach explains the experimental features quite well.Comment: 10 pages, submitted to Phys. Rev. B, tried to make a better PS file

Shade-induced Grass-Tetany-Prone Chemical Changes in Agropyron desertorum and Elymus cinereus

Grass tetany, a magnesium (Mg) deficiency in grazing ruminants, often occurs simultaneously with periods of reduced solar radiation levels. The objective of this study was to determine if reduced radiation levels produce a chemical composition in grass indicative of a tetany-prone forage. Two grass species were exposed to three radiation levels (8, 25, and 100% of actual) by shading with burlap cloth. The vegetatively growing forage was harvested at weekly intervals over a 5-week period during early spring. Shaded forage had higher concentrations of Mg than did unshaded forage. However, shaded forage compared to forage grown in full sunlight would likely result in less Mg being available to the animal. The hypothesized inverse relationship between radiation and the incidence of grass tetany in Idaho, Nevada, and Utah is supported by field observations.This material was digitized as part of a cooperative project between the Society for Range Management and the University of Arizona Libraries.The Journal of Range Management archives are made available by the Society for Range Management and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform August 202