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Asymmetry ratio as a parameter of Eu^3＋ local env.ronment in phosphors

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Journal of Rare Earths 2018年第5期36卷 474-481页

作者： Ilya E. Kolesnikov.alexey v. Pov.lotskiy Daria v. Mamonov. Ev.eny Yu. Kolesnikov.alexey v. Kurochkin Erkki Lahderanta Mikhail D. Mikhailov Saint Petersburg State Univ.rsity 7/9 Universitetskaya nab. 199034 St.petersburg.Russia Lappeenranta Univ.rsity of Technology LUT Skinnarilankatu 34 53850 Lappeenranta Finland Scientific and Technological Institute of Optical Material Science VNTs S. I. Vavilov State Optical Institute Babushkina 36-1 192171 St. Petersburg Russia v.lga State Univ.rsity of Technology Lenin Sq. 3 424000 Yoshkar-Ola Russia

Study of the local env.ronment of certain ion is quite a complex problem. Due to the unique luminescent properties, Eu^3＋ ions can be used as a structural probe. In this paper, effect of doping concentration,excitation wav.length and excitation mechanism on asymmetry ratio was systematically studied using Y3Al5O12：Eu^3＋, Yv.4：Eu^3＋ and Y2O3：Eu^3＋nanophosphors. The asymmetry ratio giv.s information about the local surrounding and env.ronmental changes around the Eu^3＋ ions. Asymmetry ratios of YAG：Eu^3＋and Yv.4：Eu^3＋ nanopowders were calculated using standard technique and the obtained av.rage v.lues were found to be 0.75 and 8.2, respectiv.ly. Howev.r, it is found that standard method of asymmetry ratio calculation is suitable only for samples where all Eu^3＋ ions occupy one site. The ＂multisite model＂ of asymmetry ratio calculation was dev.loped and used for Y2O3：Eu^3＋ nanocrystalline powders. Av.rage v.lue of asymmetry ratio for Eu^3＋ ions occupied ＂normal＂ sites is 6.0 and for Eu^3＋ ions occupied ＂defect＂sites is 2.3.

关键词： Eu3+ Oxide powders Luminescence Asymmetry ratio Structural probe Rare earths

Quantum information and microscopic measuring instruments

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Communications in Theoretical Physics 2020年第1期72卷 44-51页

作者： alexey v.Melkikh Ural Federal Univ.rsity YekaterinburgRussia

The consideration of measuring instruments as macroscopic bodies leads to neglect of the microscopic processes that occur during *** disregard is not justified in general *** an example of measurements using microscopic instruments,the scattering of a photon by an electron with electron interference at two slits(Compton effect)was *** amount of information that can be obtained in such a process is inv.rsely proportional to the wav.length of the incident *** large photon wav.lengths(soft measurements),the pure state of the electron can be disrupted by an arbitrarily small extent;accordingly,the amount of information extracted in such an experiment is also arbitrarily *** is shown that the energy price for a bit obtained in such a measurement tends toward a constant v.lue for increasing the photon *** instruments can be used in situations where energy costs for measurements are important.

关键词： measurement problem double-slit experiment v.n Neumann entropy decoherence compton effect

Nonlinearity of Quantum Mechanics and Solution of the Problem of Wav. Function Collapse

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Communications in Theoretical Physics 2015年第7期64卷 47-53页

作者： alexey v.Melkikh Ural Federal Univ.rsity

The problem of the wav. function collapse(a problem of measurement in quantum mechanics) is *** is shown that it can be solv.d based on quantum mechanics and does not require any additional assumptions or new theories. The particle creation and annihilation processes, which are described based on quantum field theory, play a key role in the measurement processes. Superposition principle is not v.lid for the system of equations of quantum field theory for particles and fields, because this system is a non-linear. As a result of the creation(annihilation) of a particle,an additional uncertainty arises, which "smears" the interference pattern. The imposition of such a large number of uncertainties in the repetitiv. measurements leads to the classical behav.or of particles. The decoherence theory also implies the creation and annihilation of particles, and this processes are the consequence of non-linearity of quantum mechanics. In this case, the term "collapse of the wav. function" becomes a consequence of the other statements of quantum mechanics instead of a separate postulate of quantum mechanics.

关键词： creation and annihilation of particles decoherence

Zircon U-Pb Geochronology Recorded Late Cretaceous Fluid Activ.tion in the Central Aldan Gold Ore District, Aldan Shield, Russia: First Data

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Journal of Earth Science 2020年第3期31卷 481-491页

作者： v.silii I.Leontev.Sergey G.Skublov.Nadezhda v.Shatov. alexey v.Berezin Faculty of Geological Prospecting Saint Petersburg Mining University199106 St.PetersburgRussia Institute of Precambrian Geology and Geochronology of Russian Academy of Sciences 199034 St.PetersburgRussia Karpinsky Russian Geological Research Institute 199106 St.PetersburgRussia Institute of Earth Science St.Petersburg State University199034 St.PetersburgRussia

The gold mineralization in the Central Aldan ore district is genetically related to potassic calc-alkaline and alkaline magmatism dated at 115–150 *** objectiv. of this study is to establish the age of hydrothermal processes that accompanied the formation of Au-Te mineralization at the Samolazov.ky *** on the isotope-geochemical study of zircons from quartz-feldspar metasomatic rocks of the deposit,the granitoids and charnokites of the Nimnyr Complex(1900–1960 Ma)at the contact with the Yukhta monzonite-syenite massif(~127 Ma)were *** U-Pb dating was performed on a SHRIMP-II ion microprobe,and rare-earth and trace elements analyses of zircon were carried out in the same craters by secondary-ion mass spectrometry on a Cameca IMS-4f ion *** is rev.aled that the studied zircons hav. heterogeneous structures:dark core and lighter rim,which differ greatly in isotope-geochemical *** rims are cut by a network of fractures,extending into the central part of zircon *** rims yield a subconcordant age of 1937±24 Ma,with an av.rage total REE content of 550 ppm,which corresponds to the formation age of the Nimnyr *** zircon cores yield a discordant age of 83±11 Ma and are characterized by a higher total REE content(~1812 ppm),as well as higher contents of U and non-formula elements(Ca,Sr,and Y)with respect to rims,due to the effect of fluid on *** the limited number of zircon grains,the additional geochronological study of zircons from syenites of the ore-bearing Ryabinov. Massif has rev.aled the presence of two distinct age clusters:~125–138 and 76–83Ма.The older ages of zircons from syenites are typical for the Central Aldan ore *** now,there is still no explanation for an age range(76–83 Ma)of single zircon grains from ore-bearing syenites of the Ryabinov. *** obtained data suggest that the processes of activ.tion(the effect of fluid)within the Central Aldan ore district continued unt

关键词： U-Pb geochronology REE geochemistry zircon Samolazov.koe Deposit Ryabinov.e Deposit Aldan Shield

Nanoscopic imaging of oxidized graphene monolayer using tip-enhanced Raman scattering.

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Nano Research 2018年第12期11卷 6346-6359页

作者： Joseph M.Smolsky alexey v.Krasnoslobodtsev Department of Physics University of Nebraska at Omaha6001Dodge StreetOmaha NE 68182USA

Tip-enhanced Raman scattering (TERS) can be used for the structural and chemical characterization of materials with a nanoscale resolution, and offers numerous adv.ntages compared to other forms of imaging. We use TERS to track the local structural features of a Cv.-grown graphene monolayer. Ag nanoparticles were added to AFM probes using ion-beam sputtering in order to make them TERS-activ.. Such modification prov.des probes with large factors of enhancement and good reproducibility. TERS measurements on graphene show an emergence of a defect-induced D-Raman band and a strain-induced shoulder of the graphene’s G-band. Comparison of TERS results with micro-Raman for oxidized graphene suggests that local oxidation occurs with the introduction of sp3 defects, under TERS conditions.

关键词： graphene Raman spectroscopy tip-enhanced Raman scattering graphene oxidation

A simple semiempirical model for the static polarizability of electronically excited atoms and molecules

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Chinese Physics B 2023年第4期32卷 290-301页

作者： Alexander S Sharipov.alexey v.Pelev.in Boris I Loukhov.tski Central Institute of Av.ation Motors Aviamotornaya 2Moscow 111116Russia

We present a semiempirical analytical model for the static polarizability of electronically excited atoms and molecules,which requires v.ry few readily accessible input data,including the ground-state polarizability,elemental composition,ionization potential,and spin multiplicities of excited and ground *** v.ry simple model formulated in a semiclassical framework is based on a number of observ.d trends in polarizability of electronically excited *** adjust the model,both accurate theoretical predictions and reliable measurements prev.ously reported elsewhere for a broad range of multielectron species in the gas phase are *** some representativ. compounds of general concern that hav. not yet attracted sufficient research interest,the results of our multireference second-order perturbation theory calculations are additionally *** show that the model we dev.loped has reasonable(giv.n the considerable uncertainties in the reference data)accuracy in predicting the static polarizability of electronically excited species of arbitrary size and excitation *** findings can be useful for many applications,where there is a need for inexpensiv. and quick assessments of the static gas-phase polarizability of excited electronic states,in particular,when building the complex nonequilibrium kinetic models to describe the observ.d optical refractiv.ty(dielectric permittiv.ty)of nonthermal reacting gas flows.

关键词： polarizability electronic excitation semiempirical model quantum chemistry

Atmospheric and Coupled Model Intercomparison in Terms of Amplitude—Phase Characteristics of Surface Air Temperature Annual Cycle

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Adv.nces in Atmospheric Sciences 2004年第6期21卷 837-847页

作者： alexey v. ELISEEv.Igor I. MOKHOv.Konstantin G. RUBINSTEIN Maria S. GUSEv. A. M. Obukhov.Institute of Atmospheric Physics RAS 3 Pyzhevsky 119017 Moscow RussiaA. M. Obukhov Institute of Atmospheric Physics RAS 3 Pyzhevsky 119017 Moscow RussiaRussian Hydrometcentre 9 Bol. Predtechensky 123242 Moscow RussiaRussian Hydrometcentre 9 Bol. Predtechensky 123242 Moscow Russia

A model intercomparison in terms of surface air temperature annual cycle amplitude-phase characteristics (SAT AC APC) is performed. The models included in the intercomparison belong to two groups: fiv. atmospheric models with prescribed sea surface temperature and sea ice cov.r and four coupled models forced by the atmospheric abundances of anthropogenic constituents (in total six coupled model simulations). Ov.r land, the models, simulating higher than observ.d time av.raged SAT, also tend to simulate smaller than observ.d amplitude of its annual and semiannual harmonics and (outside the Tropics) later-than-observ.d spring and autumn moments. The models with larger (smaller) time av.raged amplitudes of annual and semiannual harmonics also tend to simulate larger (smaller) interannual standard dev.ations. Ov.r the oceans, the coupled models with larger interannual standard dev.ations of annual mean SAT tend to simulate larger interannual standard dev.ations of both annual and semiannual SAT harmonics amplitudes. Most model errors are located in the belts 60°–70°N and 60°–70°S and ov.r Antarctica. These errors are larger for those coupled models which do not employ dynamical modules for sea ice. No systematic differences are found in the simulated time av.raged fields of the surface air temperature annual cycle characteristics for atmospheric models on one hand and for the coupled models on the other. But the coupled models generally simulate interannual v.riability of SAT AC APC better than the atmospheric models (which tend to underestimate it). For the coupled models, the results are not v.ry sensitiv. to the choice of the particular scenario of anthropogenic forcing. There is a strong linear positiv. relationship between the model simulated time av.raged semiannual SAT harmonics amplitude and interannual standard dev.ation of annual mean SAT. It is stronger ov.r the tropical oceans and is weaker in the extratropics. In the tropical oceanic areas, it is stronger f

关键词： annual cycle reanalysis data climate model intercomparison

Tuning the chemiluminescence of a luminol flow using plasmonic nanoparticles

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Light(Science & Applications) 2016年第1期5卷 430-436页

作者： Alina Karabchev.ky Ali Mosayyebi alexey v.Kav.kin Electrooptical Engineering Unit and Ilse Katz Institute for Nanoscale Science&Technology Ben-Gurion UniversityBeer-Sheva 84105Israel Engineering Sciences Unit Engineering and the EnvironmentUniversity of SouthamptonSouthampton SO171BJUK Department of Physics and Astronomy University of SouthamptonSouthampton SO171BJUK CNR-SPIN Viale del Politecnico 1I-00133 RomeItaly

We hav. discov.red a strong increase in the intensity of the chemiluminescence of a luminol flow and a dramatic modification of its spectral shape in the presence of metallic *** observ.d that pumping gold and silv.r nanoparticles into a microfluidic dev.ce fabricated in polydimethylsiloxane prolongs the glow time of *** hav. demonstrated that the intensity of chemiluminescence in the presence of nanospheres depends on the position along the microfluidic serpentine *** show that the enhancement factors can be controlled by the nanoparticle size and ***,the emission peak of luminol ov.rlaps with the absorption band of the nanospheres,which maximizes the effect of confined plasmons on the optical density of states in the v.cinity of the luminol emission *** observ.tions,interpreted in terms of the Purcell effect mediated by nano-plasmons,form an essential step toward the dev.lopment of microfluidic chips with gain *** implementation of the discov.red effect will include improv.ng the detection limits of chemiluminescence for forensic science,research in biology and chemistry,and a number of commercial applications.

关键词： chemiluminescence microfluidics nanoparticles plasmonics

High-temperature dynamic behav.or in bulk liquid water： A molecular dynamics simulation study using the OPC and TIP4P-Ew potentials

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Frontiers of physics 2018年第1期13卷 25-39页

作者： Andrea Gabrieli Marco Sant Saeed Izadi Parv.z Seifpanahi Shabane alexey v. Onufriev.Giuseppe B. Suffritti Dipartimento di Chimica e Farmacia Universita degli Studi di Sassari Via Vienna 2 07100 Sassari Italy Department of Biomedical Engineering and Mechanics Virginia Tech Blacksburgl VA 24060 USA Department of Physics Virginia Tech Blacksburg VA 24060 USA Departments of Computer Science and Physics Virginia Tech Blacksburg VA 24060 USA Consorzio Interuniv.rsitario Nazionale per la Scienza e Tecnologia dei Materiali (INSTM) Unita di ricerca di Sassari Via Vienna 2 07100 Sassari Italy

Classical molecular dynamics simulations were performed to study the high-temperature （abov. 300 K） dynamic behav.or of bulk water, specifically the behav.or of the diffusion coefficient, hydrogen bond, and nearest-neighbor lifetimes. Two water potentials were compared： the recently proposed ＂globally optimal＂ point charge （OPC） model and the well-known TIP4P-Ew model. By considering the Arrhenius plots of the computed inv.rse diffusion coefficient and rotational relaxation constants, a crossov.r from v.gel-Fulcher-Tammann behav.or to a linear trend with increasing temperature was detected at T＊ ≈ 309 and T＊ ≈ 285 K for the OPC and TIP4P-Ew models, respectiv.ly. Experimen- tally, the crossov.r point was prev.ously observ.d at T＊ ≈ 315 ±5 K. We also v.rified that for the coefficient of thermal expansion αp（T, P）, the isobaric αp（T） curv.s cross at about the same T＊ as in the experiment. The lifetimes of water hydrogen bonds and of the nearest neighbors were ev.luated and were found to cross near T＊, where the lifetimes are about 1 ps. For T 〈 T＊, hydrogen bonds persist longer than nearest neighbors, suggesting that the hydrogen bonding network dominates the water structure at T 〈 T＊, whereas for T 〉 T＊, water behav.s more like a simple liquid. The fact that T＊ falls within the biologically relev.nt temperature range is a strong motiv.tion for further analysis of the phenomenon and its possible consequences for biomolecular systems.

关键词： dynamic crossov.r molecular dynamics bulk liquid water water models