Dipole aggregation in LiF doped with Be2+

The thermally stimulated depolarization currents technique (TSDC) has been employed for the study of the kinetics of the aggregation of impurity-vacancy (I-V) dipoles. This study is based on the time variation of a complex band which peaks around 200 K. It is found that for ageing times up to 150min the clustering seems to follow second-order kinetics. © 1988

Dipole aggregation in LiF doped with Be2+

The thermally stimulated depolarization currents technique (TSDC) has been employed for the study of the kinetics of the aggregation of impurity-vacancy (I-V) dipoles. This study is based on the time variation of a complex band which peaks around 200 K. It is found that for ageing times up to 150min the clustering seems to follow second-order kinetics. © 1988

A radiation defect in pyromorphite and vanadinite

In a green pyromorphite from Pribram (Bohemia, Czechoslovakia) and red vanadinites from Globe (Arizona, USA) and Mibladen (Morocco), electron centres with fairly large deviations of g factors from the free electron value, as well as a septet hyperfine structure, were observed and analyzed by EPR. The latter can only arise from two at least approximately equivalent Cl nuclei, thus showing that the centres are localized on PbII sites of monoclinic site symmetry. They have an axial symmetry in pyromorphite and a triclinic one in vanadinite. The higher symmetry in pyromorphite may arise from a dynamic Jahn-Teller effect, whereas the lower one in vanadinite most likely is caused by substitution of an adjacent Pb1 by trivalent impurities. These centres are tentatively assigned to Pb+, although no hyperfine satellites due to 207Pb could be detected. -Author

An Electrolytically Generated, Localized Hole Center in Quartz

In natural smoky quartz and neutron-irradiated, initially colorless quartz a new hole center was formed electrolytically at temperatures near 1100 K in addition to the well-known smoky quartz center. Unlike the latter its electron paramagnetic resonance spectra can already be measured at room temperature due to firm localization of the hole on one oxygen. It is characterized by fairly small hyperfine splittings due to Al impurity and significant deviations of all three principal g factors from that of a free electron. A tentative model for the structure of this center is proposed. An activation energy of 215kJ/mol was determined for this electrolytic coloration from the temperature dependence of the electrolysis currents. © 1989, Verlag der Zeitschrift für Naturforschung, All rights reserved