Eu3+ activated CaWO4 was prepared by high temperature solid state reaction technique. Red afterglow was observed for in the CaWO4∶Eu after exciting with 254 nm light due to Eu3+ transition from 5D0 to 7FJ (J=0, 1, 2,...Eu3+ activated CaWO4 was prepared by high temperature solid state reaction technique. Red afterglow was observed for in the CaWO4∶Eu after exciting with 254 nm light due to Eu3+ transition from 5D0 to 7FJ (J=0, 1, 2, 3,4). By the cal culation of the thermoluminescence spectrum of CaWO4∶Eu, we conclude that there were two types of trap centers: VCa″ was formed by substitution of Ca2+ by Eu3 + and complex traps were produced because of substitution of W6+ by Eu3+.展开更多
The Ediacaran Doushantuo Formation（ca. 635–551 Ma） deposited immediately after the last Neoproterozoic glaciations and recorded the most prominent negative excursions of carbonate carbon isotopic composition（δ^...The Ediacaran Doushantuo Formation（ca. 635–551 Ma） deposited immediately after the last Neoproterozoic glaciations and recorded the most prominent negative excursions of carbonate carbon isotopic composition（δ^（13）C（carb））. These excursions have been interpreted as a result of widespread remineralization of a large dissolved organic carbon（DOC） reservoir in the Ediacaran deep oceans. However, there is no direct evidence so far found in rocks for the proposed DOC reservoir, which devalues such an interpretation. Here, we conducted a detailed study on the glow-curves characteristics and signal origins of spurious thermoluminescence（TL） of the Doushantuo Formation at Jiulongwan in Yangtze Gorges area, South China, through sequential tests under CO2, N2 and air. Spurious TL intensities for test samples before and after removing soluble organic matter via accelerated solvent extraction（ASE） are nearly identical. Further, significant positive correlation between the spurious TL intensity and total inorganic carbon（TIC） content（R^2=0.7） indicate that the Doushantuo spurious TL with the characteristic peak at 393.5 °C from the sequential test is chemiluminescence（CL） which is derived from the oxidation of a type of non-volatile organic matter strongly associated with carbonate mineral lattice（termed as “X-OM”）. A most likely explanation is that the X-OM is a type of dissolved organic matter which co-precipitated with carbonate minerals into sediments in the Ediacaran Doushantuo Ocean. Furthermore, a significant exponential negative correlation（R^2=0.55） is observed between the CL data and the isotopic difference between carbonate and coexisting bulk organic matter（i.e., Δ^（13）C（carb-org）, a proxy for remineralization degree of DOC reservoir in proposed DOC hypothesis）, suggesting that the X-OM was derived from the oxidation of the DOC reservoir in the Ediacaran Ocean. We thus propose that the X-OM and its CL detected in our study may have recorded the e展开更多
文摘Eu3+ activated CaWO4 was prepared by high temperature solid state reaction technique. Red afterglow was observed for in the CaWO4∶Eu after exciting with 254 nm light due to Eu3+ transition from 5D0 to 7FJ (J=0, 1, 2, 3,4). By the cal culation of the thermoluminescence spectrum of CaWO4∶Eu, we conclude that there were two types of trap centers: VCa″ was formed by substitution of Ca2+ by Eu3 + and complex traps were produced because of substitution of W6+ by Eu3+.
基金supported by the Chinese 973 Program (No. 2013CB955704)the National Natural Science Foundation of China (No. 41172030)
文摘The Ediacaran Doushantuo Formation（ca. 635–551 Ma） deposited immediately after the last Neoproterozoic glaciations and recorded the most prominent negative excursions of carbonate carbon isotopic composition（δ^（13）C（carb））. These excursions have been interpreted as a result of widespread remineralization of a large dissolved organic carbon（DOC） reservoir in the Ediacaran deep oceans. However, there is no direct evidence so far found in rocks for the proposed DOC reservoir, which devalues such an interpretation. Here, we conducted a detailed study on the glow-curves characteristics and signal origins of spurious thermoluminescence（TL） of the Doushantuo Formation at Jiulongwan in Yangtze Gorges area, South China, through sequential tests under CO2, N2 and air. Spurious TL intensities for test samples before and after removing soluble organic matter via accelerated solvent extraction（ASE） are nearly identical. Further, significant positive correlation between the spurious TL intensity and total inorganic carbon（TIC） content（R^2=0.7） indicate that the Doushantuo spurious TL with the characteristic peak at 393.5 °C from the sequential test is chemiluminescence（CL） which is derived from the oxidation of a type of non-volatile organic matter strongly associated with carbonate mineral lattice（termed as “X-OM”）. A most likely explanation is that the X-OM is a type of dissolved organic matter which co-precipitated with carbonate minerals into sediments in the Ediacaran Doushantuo Ocean. Furthermore, a significant exponential negative correlation（R^2=0.55） is observed between the CL data and the isotopic difference between carbonate and coexisting bulk organic matter（i.e., Δ^（13）C（carb-org）, a proxy for remineralization degree of DOC reservoir in proposed DOC hypothesis）, suggesting that the X-OM was derived from the oxidation of the DOC reservoir in the Ediacaran Ocean. We thus propose that the X-OM and its CL detected in our study may have recorded the e
