Self-trapped electrons and holes in PbBr2_2 crystals

We have directly observed self-trapped electrons and holes in PbBr$_{2}$ crystals with electron-spin-resonance (ESR) technique. The self-trapped states are induced below 8 K by two-photon interband excitation with pulsed 120-fs-width laser light at 3.10 eV. Spin-Hamiltonian analyses of the ESR signals have revealed that the self-trapping electron centers are the dimer molecules of Pb$_2$$^{3+}$ along the crystallographic a axis and the self-trapping hole centers are those of Br$_2$$^-$ with two possible configurations in the unit cell of the crystal. Thermal stability of the self-trapped electrons and holes suggests that both of them are related to the blue-green luminescence band at 2.55 eV coming from recombination of spatially separated electron-hole pairs.Comment: 8 pages (7 figures, 2 tables), ReVTEX; revised the text and figures 1, 4, and

Self-trapped states and the related luminescence in PbCl2_2 crystals

We have comprehensively investigated localized states of photoinduced electron-hole pairs with electron-spin-resonance technique and photoluminescence (PL) in a wide temperature range of 5-200 K. At low temperatures below 70 K, holes localize on Pb$^{2+}$ ions and form self-trapping hole centers of Pb$^{3+}$. The holes transfer to other trapping centers above 70 K. On the other hand, electrons localize on two Pb$^{2+}$ ions at higher than 50 K and form self-trapping electron centers of Pb$_2$$^{3+}$. From the thermal stability of the localized states and PL, we clarify that blue-green PL band at 2.50 eV is closely related to the self-trapped holes.Comment: 8 pages (10 figures), ReVTEX; removal of one figure, Fig. 3 in the version

Electronic dipole resonance in smoky quartz

Microwave absorption in smoky quartz mono-crystal is ascribed to resonance transitions of trapped electrons between initially configurational degenerated states, which are Stark-splitted by a polarizing electric field

Luminescence of PbCl2 and PbBr2 single crystals II. Luminescence and EPR of uv irradiated crystals

PbCl2 and PbBr2 single crystals show a red luminescence under uv excitation at temperatures below 200°K. Furthermore, PbCl2 shows a yellow emission at temperatures below 40°K. The centers responsible for these emissions have been investigated by EPR measurements. These measurements indicate that due to uv irradiation Pb′Pb, (Pb′Pb)2 and lead colloids are created. In PbCl2, a hole center, possibly Cl·cl, is created at temperatures below 50°K. Both the concentration of the Pb′Pb and the (Pb′Pb)2 centers in PbCl2 depends on the irradiation intensity; the concentration of the pair-centers increases with time after the irradiation is stopped. A similar dependence has been observed on PbBr2 crystals cleaved and mounted in the dark, but in this case the influence of the irradiation appears to be smaller. The defects responsible for the red and yellow luminescence could be identified on the basis of temperature dependence measurements. The red luminescence of both halides is ascribed to excitation and decay of Pb′Pb or (Pb′Pb)2 centers, and the yellow luminescence of PbCl2 is associated with Cl·Cl centers

EPR and luminescence of u.v. irradiated PbCl2 and PbBr2 crystals

Results are presented of EPR-measurements on PbCl2 and PbBr2 single crystals at low temperatures. Pb+, Pb+-pairs and colloidal lead particles are formed during u.v. irradiation. The concentration of the Pb+-pairs increases after the irradiation is stopped. The red luminescence of both lead halides is associated with the Pb+ centres

Electric dipole centres and colour centres in natural sodalite

Experiments on an electric dipole centre, exhibiting multiple relaxation, in the natural mineral sodalite, are described. The concentration of the dipole centres is reduced upon X irradiation, whereas simultaneously colour centres and paramagnetic centres arise. Thermal bleaching restores the original concentrations. The interrelationships between these centres are established. A model is proposed in which the dipole centre is ascribed to an interstitial monovalent metal ion (say a Na+ ion) acting as a charge compensator for an Al3+ ion, substituted for a Si4+ ion. This Al-Na complex may be destroyed by X rays, yielding an electron trapped at the sodium ion and a hole trapped at a nonbridging oxygen ion, adjacent to the Al3+ ion, to which both the optical and paramagnetic properties of the X ray induced centres are attributed

Genetic Analyses of Sow Longevity Traits, Age at First Farrowing and First-Litter Characteristics

Sow longevity is a vital trait in the pig production sector because of its economic and welfare importance. However, this trait is recorded late in a sow’s life and early selection criteria associated with sow longevity are beneficial for genetic improvement of sow longevity. The aim of this study was to estimate genetic parameters of sow longevity and other sow reproduction traits. Data included 14,284 purebred sows recorded from 1996 to 2016 in 7 commercial herds across Australia. Traits describing sow longevity included the number of maximum parities reached, length of productive lifetime in days, total number of piglets born alive per sow over her lifetime, and stayability from parity 1 to parity 4. Further traits considered were number of piglets born alive (litter size) and average piglet birth weight (both recorded in the first litter), and age at first farrowing. Sow longevity traits were genetically the same traits and had low heritabilities (0.07 to 0.13). Genetic correlations were lowly negative between sow longevity and age at first farrowing (-0.13 to -0.22), and between sow longevity and average piglet birth weight (-0.19 to -0.26). First litter size had positive genetic correlations with sow longevity traits (0.49 to 0.65). This study showed favourable genetic correlations of the traits first litter size and age at first farrowing with sow longevity, suggesting that these two traits could be suitable genetic indicators for sow longevity