Relativistic nuclear recoil corrections to the energy levels of hydrogen-like and high ZZ lithium like atoms in all orders in αZ\alpha Z

The relativistic nuclear recoil corrections to the energy levels of low-laying states of hydrogen-like and high $Z$ lithium-like atoms in all orders in $\alpha Z$ are calculated. The calculations are carried out using the B-spline method for the Dirac equation. For low $Z$ the results of the calculation are in good agreement with the $\alpha Z$ -expansion results. It is found that the nuclear recoil contribution, additional to the Salpeter's one, to the Lamb shift ($n=2$) of hydrogen is $-1.32(6)\,kHz$. The total nuclear recoil correction to the energy of the $(1s)^{2}2p_{\frac{1}{2}}-(1s)^{2}2s$ transition in lithium-like uranium constitutes $-0.07\,eV$ and is largely made up of QED contributions.Comment: 19 pages, latex, accepted for publication in Phys. Rev.

Erosion as a Factor of Transformation of Soil Radioactive Contamination in the Basin of the Shchekino Reservoir (Tula Region)

Abstract: Redistribution of sediments and Chernobyl-derived 137Сs transported with them were estimated using a set of field methods and erosion model calculations for the Shchekino reservoir (Tula region) catchment, and changes in the contents of 137Сs in soils of various types that occurred over 1986–2018 were determined. The rate of snowmelt soil erosion on arable land during this period has decreased by about a half in comparison with that in 1960–1985 due to a reduction in soil freezing depth in winter. The rainfall erosion rate increased by about a third between 1986–2003 due to an increase in the rainfall erosivity index; after that, it tended to decrease synchronously with a decrease in the rainfall erosivity. The total average annual soil loss related to water erosion varies in the range of 1.3–1.6 t ha–1 depending on the soil type. The erosional loss of 137Сs from arable land averaged 1.5–2% of its total inventory, which decreased by more than a half in comparison with the initial inventory in May 1986 due to natural decay. On 0.4% of the arable land with maximum rates of erosion, the decrease in the 137Сs inventory reached 12–40% from the initial inventory. More than 90% of 137Сs washed away with sediments from arable lands were redeposited along the transportation pathway from arable fields to permanent streams. The total soil 137Сs inventory exceeded its initial inventory at the time of fallout from the atmosphere in May 1986 in the bottoms of hollows in areas from the lower edge of the arable land to the upper reaches of dry first-order valleys due to high sedimentation rates. The 137Сs inventory exceeded the lower threshold of permissible radioactive contamination of soils (37 kBq m–2) also in some other sediment sinks (bottoms of dry valleys, foot of plowed slopes, and a low floodplain of rivers) due to the accumulation of contaminated sediments

Using reservoir sediment deposits to determine the longer-term fate of chernobyl-derived ¹³⁷Cs fallout in the fluvial system

Vast areas of Europe were contaminated by the fallout of 137Cs and other radionuclides, as a result of the Chernobyl accident in 1986. The post-fallout redistribution of Chernobyl-derived 137Cs was associated with erosion and sediment transport processes within the fluvial system. Bottom sediments from lakes and reservoirs can provide a valuable source of information regarding the post-fallout redistribution and fate of 137Cs released by the Chernobyl accident. A detailed investigation of sediment-associated 137Cs in the bottom sediments of a reservoir in a Chernobyl-affected area in Central Russia has been undertaken. A new approach, based on the vertical distribution of 137Cs activity concentrations in the reservoir bottom sediment makes it possible to separate the initially deposited bottom sediment, where the 137Cs activity reflects the direct fallout of Chernobyl-derived 137Cs to the reservoir surface and its subsequent incorporation into sediment deposited immediately after the accident, from the sediment mobilized from the catchment deposited subsequently. The deposits representing direct fallout from the atmosphere was termed the “Chernobyl peak”. Its shape can be described by a diffusion equation and it can be distinguished from the remaining catchment-derived 137Cs associated with sediment accumulated with sediments during the post-Chernobyl period. The 137Cs depth distribution above the “Chernobyl peak” was used to provide a record of changes in the concentration of sediment-associated 137Cs transported from the upstream catchment during the post-Chernobyl period. It was found that the 137Cs activity concentration in the sediment deposited in the reservoir progressively decreased during the 30-year period after the accident due to a reduction in the contribution of sediment eroded from the arable land in the catchment. This reflects a reduction in both the area of cultivated land area and the reduced incidence of surface runoff from the slopes during spring snowmelt due to climate warming

Using reservoir sediment deposits to determine the longer-term fate of chernobyl-derived 137Cs fallout in the fluvial system

Vast areas of Europe were contaminated by the fallout of 137Cs and other radionuclides, as a result of the Chernobyl accident in 1986. The post-fallout redistribution of Chernobyl-derived 137Cs was associated with erosion and sediment transport processes within the fluvial system. Bottom sediments from lakes and reservoirs can provide a valuable source of information regarding the post-fallout redistribution and fate of 137Cs released by the Chernobyl accident. A detailed investigation of sediment-associated 137Cs in the bottom sediments of a reservoir in a Chernobyl-affected area in Central Russia has been undertaken. A new approach, based on the vertical distribution of 137Cs activity concentrations in the reservoir bottom sediment makes it possible to separate the initially deposited bottom sediment, where the 137Cs activity reflects the direct fallout of Chernobyl-derived 137Cs to the reservoir surface and its subsequent incorporation into sediment deposited immediately after the accident, from the sediment mobilized from the catchment deposited subsequently. The deposits representing direct fallout from the atmosphere was termed the “Chernobyl peak”. Its shape can be described by a diffusion equation and it can be distinguished from the remaining catchment-derived 137Cs associated with sediment accumulated with sediments during the post-Chernobyl period. The 137Cs depth distribution above the “Chernobyl peak” was used to provide a record of changes in the concentration of sediment-associated 137Cs transported from the upstream catchment during the post-Chernobyl period. It was found that the 137Cs activity concentration in the sediment deposited in the reservoir progressively decreased during the 30-year period after the accident due to a reduction in the contribution of sediment eroded from the arable land in the catchment. This reflects a reduction in both the area of cultivated land area and the reduced incidence of surface runoff from the slopes during spring snowmelt due to climate warming. © 2021 Elsevier Lt

Ferroelectric properties of strontium-bismuth tantalate thin film deposited by rf magnetron sputtering method

Исследованы характеристики сегнетоэлектрических тонких пленок танталата стронция-висмута (SBT), нанесенных методом ВЧ магнетронного распыления на Pt/TiOx/SiO2/Si подложки. Установлены зависимости диэлектрической проницаемости, остаточной поляризации и коэрцитивной силы пленок SBTот режимов последующего отжига. При температуре отжига 800° C получены пленки с остаточной поляризацией 2Pr= 3,02 мкКл/см 2 , коэрцитивной силой 2Ec= 140 кВ/см. Диэлектрическая проницаемость и тангенс угла диэлектрических потерь на частоте 1,0 МГц составляли соответствен-но = 125 и tg= 0,067. Температура Кюри пленок достигала 310–315° С.Characteristics of ferroelectric thin films of strontium-bismuth tantalate (SBT), which were deposited by means of HF magnetron sputtering on Pt/TiO2/SiO2/Si substrates, are investigated. The dependences of permittivity, residual polarization, and coercitivity of SBT films on the modes of subsequent annealing are established. Films with the residual polarization of 2Pr = 3.02 μC/cm 2 and coercitivity of 2Ec = 140 kV/cm are obtained at the annealing temperature of 800°C. The dielectric constant and loss tangent at the frequency of 1.0 MHz were accordingly equalto ε = 125 and tg= 0.067. The Curie temperature of the films reached 310–315° C