Lattice sites of Cd in ferroelectric BaTiO3_3

The radioactive isotope 111mCd was implanted into BaTiO3 in order to measure electric field gradients with Perturbed Angular Correlation spectroscopy (PAC). It is possible to anneal the implantation induced lattice damage to a certain extent. Then, 111mCd probes are positioned at two sites with distinct axially symmetric electric field gradients characterized by the quadrupole coupling constants of 33.9(9) and 69.8(9) MHz. These electric field gradients can be assigned to 111mCd at the Ti- and the Ba-sites

Identification of Ag-acceptors in 111 ⁣^{111}\!Ag 111 ⁣^{111}\!Cd doped ZnTe and CdTe

Nominally undoped ZnTe and CdTe crystals were implanted with radioactive $^{111}\!$Ag, which decays to $^{111}\!$Cd, and investigated by photoluminescence spectroscopy (PL). In ZnTe, the PL lines caused by an acceptor level at 121 meV are observed: the principal bound exciton (PBE) line, the donor-acceptor pair (DAP) band, and the two-hole transition lines. In CdTe, the PBE line and the DAP band that correspond to an acceptor level at 108 meV appear. Since the intensities of all these PL lines decrease in good agreement with the half-life of $^{111}\!$Ag of 178.8 h, both acceptor levels are concluded to be associated with defects containing a single Ag atom. Therefore, the earlier assignments to substitutional Ag on Zn- and Cd-lattice sites in the respective II-VI semiconductors are confirmed. The assignments in the literature of the S$_1$, S$_2$, and S$_3$ lines in ZnTe and the X$\scriptstyle^\textrm{Ag}_{1}\,\,,$ X$\scriptstyle^\textrm{Ag}_{2}$/ C$\scriptstyle^\textrm{Ag}_{1}\,$ and C$\scriptstyle^\textrm{Ag}_{2}\,$ lines in CdTe to Ag-related defect complexes are not confirmed

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

Defects in CdS: In detected by peturbed angular correlation spectroscopy (PAC)

Magerle R, Deicher M, Desnica U, et al. Defects in CdS: In detected by peturbed angular correlation spectroscopy (PAC). Appl. Surf. Sci. 1991;50(1-4):159-164.The local lattice environment of the donor In in CdS is investigated measuring the electric-field gradient at the site of the radioactive probe atom In-111 by the perturbed gamma-gamma angular correlation technique. It is shown that implantation of In into CdS with subsequent annealing drives 100% of the In atoms to Cd lattice sites. Diffusion of In into CdS under S overpressure results in the formation of In(Cd)-V(Cd) pairs which seem to be responsible for the self-compensation of In donors in CdS

Luminescence and influence of defect concentration on excitons in 197 ⁣^{197}\!Hg / 197 ⁣^{197}\!Au-doped CdTe

CdTe, implanted with $^{197}\!$Hg ions, which decay to $^{197}\!$Au with a half-life of 64.1 h, was investigated by photoluminescence (PL) spectroscopy. The results unambiguously verify the assignments of both, the donor–acceptor pair transition at 1.335 eV, which corresponds to an acceptor level with E$\scriptstyle_{A}$=263 meV, and the recombination of excitons bound to neutral acceptors at 1.57606 eV to single Au atoms on Cd sites. In addition, the dependence of the intensities of excitonic lines on the defect concentration was investigated quantitatively. The observed intensities are well explained, assuming that a defect can only bind an exciton if there is no additional defect within the volume of the bound exciton. The ratio between the exciton radii of the Cu and Au-bound excitons R$\scriptscriptstyle^\textrm{Cu}_{exc}$ / R$\scriptscriptstyle^\textrm{Au}_{exc}$ = 1.2$\pm$0.2 obtained from this model is in good agreement with the ratio derived from the diamagnetic shift parameters of the two corresponding PL lines