Calculation of radiation attenuation coefficients, effective atomic numbers and electron densities for some building materials

International Nuclear Information System (INIS)

Damla, N.; Baltas, H.; Celik, A.; Kiris, E.; Cevik, U.

2008-01-01

Some building materials, regularly used in Turkey, such as sand, cement, gas concrete (lightweight, aerated concrete), tile and brick, have been investigated in terms of mass attenuation coefficient, effective atomic, numbers (Z eff ), effective electron densities (N e ) and photon interaction cross section (σ a ) at 14 different energies from 81- to 1332-keV gamma-ray energies. The gamma rays were detected by using gamma-ray spectroscopy, a High Purity Germanium (HPGe) detector. The elemental compositions of samples were analysed using an energy dispersive X-ray fluorescence spectrometer. Mass attenuation coefficients of these samples have been compared with tabulations based upon the results of WinXcom. The theoretical mass attenuation coefficients were estimated using the mixture rule and the experimental values of investigated parameters were compared with the calculated values. The agreement of measured values of mass attenuation coefficient, effective atomic numbers, effective electron densities and photon interaction cross section with the theory has been found to be quite satisfactory. (authors)

Effective atomic numbers, electron densities and kinetic energy released in matter of vitamins for photon interaction

Science.gov (United States)

Shantappa, A.; Hanagodimath, S. M.

2014-01-01

Effective atomic numbers, electron densities of some vitamins (Retinol, Riboflavin, Niacin, Biotin, Folic acid, Cobalamin, Phylloquinone and Flavonoids) composed of C, H, O, N, Co, P and S have been calculated for total and partial photon interactions by the direct method for energy range 1 keV-100 GeV by using WinXCOM and kinetic energy released in matter (Kerma) relative to air is calculated in energy range of 1 keV-20 MeV. Change in effective atomic number and electron density with energy is calculated for all photon interactions. Variation of photon mass attenuation coefficients with energy are shown graphically only for total photon interaction. It is observed that change in mass attenuation coefficient with composition of different chemicals is very large below 100 keV and moderate between 100 keV and 10 MeV and negligible above 10 MeV. Behaviour of vitamins is almost indistinguishable except biotin and cobalamin because of large range of atomic numbers from 1(H) to 16 (S) and 1(H) to 27(Co) respectively. K a value shows a peak due to the photoelectric effect around K-absorption edge of high- Z constituent of compound for biotin and cobalamin.

Studies on effective atomic number, electron density and kerma for some fatty acids and carbohydrates

DEFF Research Database (Denmark)

Manohara, S.R.; Hanagodimath, S.M.; Gerward, Leif

2008-01-01

The effective atomic number, Z(eff), the effective electron density, N-el, and kerma have been calculated for some fatty acids and carbohydrates for photon interaction in the extended energy range from 1 keV to 100 GeV using an accurate database of photon-interaction cross sections and the WinXCo...

The effective atomic number for gamma ray interactions with heavy metal oxide glasses

DEFF Research Database (Denmark)

Manohara, S. R.; Hanagodimath, S.M.; Gerward, Leif

2010-01-01

The effective atomic number, Z(eff), and the effective electron density, N-el,N-eff, have been calculated at photon energies from 1 keV to 100 GeV for CaO-SrO-B2O3, ZnO-PbO-B2O3, and CdO-PbO-B2O3 glasses with potential applications as gamma ray shielding materials. Appreciable variations are noted...... glasses have gamma ray shielding properties comparable with standard shielding materials, such as concrete....

The effective atomic numbers of some biomolecules calculated by two methods: A comparative study

Energy Technology Data Exchange (ETDEWEB)

Manohara, S. R.; Hanagodimath, S. M.; Gerward, L. [Department of Physics, Gulbarga University, Gulbarga, Karnataka 585 106 (India); Department of Physics, Technical University of Denmark, Lyngby DK-2800 (Denmark)

2009-01-15

The effective atomic numbers Z{sub eff} of some fatty acids and amino acids have been calculated by two numerical methods, a direct method and an interpolation method, in the energy range of 1 keV-20 MeV. The notion of Z{sub eff} is given a new meaning by using a modern database of photon interaction cross sections (WinXCom). The results of the two methods are compared and discussed. It is shown that for all biomolecules the direct method gives larger values of Z{sub eff} than the interpolation method, in particular at low energies (1-100 keV) At medium energies (0.1-5 MeV), Z{sub eff} for both methods is about constant and equal to the mean atomic number of the material. Wherever possible, the calculated values of Z{sub eff} are compared with experimental data.

The effective atomic numbers of some biomolecules calculated by two methods: A comparative study

International Nuclear Information System (INIS)

Manohara, S. R.; Hanagodimath, S. M.; Gerward, L.

2009-01-01

The effective atomic numbers Z eff of some fatty acids and amino acids have been calculated by two numerical methods, a direct method and an interpolation method, in the energy range of 1 keV-20 MeV. The notion of Z eff is given a new meaning by using a modern database of photon interaction cross sections (WinXCom). The results of the two methods are compared and discussed. It is shown that for all biomolecules the direct method gives larger values of Z eff than the interpolation method, in particular at low energies (1-100 keV) At medium energies (0.1-5 MeV), Z eff for both methods is about constant and equal to the mean atomic number of the material. Wherever possible, the calculated values of Z eff are compared with experimental data.

The effective atomic numbers of some biomolecules calculated by two methods: A comparative study

DEFF Research Database (Denmark)

Manohara, S.R.; Hanagodimath, S.M.; Gerward, Leif

2009-01-01

The effective atomic numbers Z(eff) of some fatty acids and amino acids have been calculated by two numerical methods, a direct method and an interpolation method, in the energy range of 1 keV-20 MeV. The notion of Z(eff) is given a new meaning by using a modern database of photon interaction cro...

A non-destructive technique for assigning effective atomic number to scientific samples by scattering of 59.54 keV gamma photons

International Nuclear Information System (INIS)

Singh, M.P.; Sharma, Amandeep; Singh, Bhajan; Sandhu, B.S.

2010-01-01

The objective of present experiment, employing a scattering of 59.54 keV gamma photons, is to assign effective atomic number (Z eff ) to scientific samples (rare earths) of known composition. An HPGe semiconductor detector, placed at 90 o to the incident beam, detects gamma photons scattered from the sample under investigation. The experiment is performed on various elements with atomic number satisfying, 6≤Z≤82, for 59.54 keV incident photons. The intensity ratio of Rayleigh to Compton scattered peaks, corrected for photo-peak efficiency of gamma detector and absorption of photons in the sample and air, is plotted as a function of atomic number and constituted a best fit-curve. From this fit-curve, the respective effective atomic numbers to samples of rare earths are determined. The agreement of measured values of Z eff with theoretical calculations is quite satisfactory.

Combustor exhaust-emissions and blowout-limits with diesel number 2 and Jet A fuels utilizing air-atomizing and pressure-atomizing nozzles

Science.gov (United States)

Ingebo, R. D.; Norgren, C. T.

1975-01-01

The effect of fuel properties on exhaust emissions and blowout limits of a high-pressure combustor segment is evaluated using a splash-groove air-atomizing fuel injector and a pressure-atomizing simplex fuel nozzle to burn both diesel number 2 and Jet A fuels. Exhaust emissions and blowout data are obtained and compared on the basis of the aromatic content and volatility of the two fuels. Exhaust smoke number and emission indices for oxides of nitrogen, carbon monoxide, and unburned hydrocarbons are determined for comparison. As compared to the pressure-atomizing nozzle, the air-atomizing nozzle is found to reduce nitrogen oxides by 20%, smoke number by 30%, carbon monoxide by 70%, and unburned hydrocarbons by 50% when used with diesel number 2 fuel. The higher concentration of aromatics and lower volatility of diesel number 2 fuel as compared to Jet A fuel appears to have the most detrimental effect on exhaust emissions. Smoke number and unburned hydrocarbons are twice as high with diesel number 2 as with Jet A fuel.

Simulated mixed absorbers and effective atomic numbers for γ ...

Indian Academy of Sciences (India)

Keywords. γ-rays; γ attenuation; simulated mixed absorbers; effective atomic ... We have tried to simulate composite (mixed) absorbers ... Experimental method .... puter, Program manual, Centre for Radiation Research, National Bureau of ...

Accessing photon number via an atomic time interval

International Nuclear Information System (INIS)

Camparo, J.C.; Coffer, J.G.

2002-01-01

We show that Rabi resonances can be used to assess field strength in terms of time at the atomic level. Rabi resonances are enhancements in the amplitude of atomic population oscillations when the Rabi frequency, Ω, 'matches' a field-modulation frequency, ω m . We demonstrate that Ω=2κω m and find that κ=1.03±0.05. Since Ω is defined by field strength (i.e., photon number) through atomic constants, and ω m may be referenced to an atomic clock, our work shows that Rabi resonances provide a connection between time and photon number

Effective atomic number and effective electron densities of some inorganic compounds for Compton effect in the gamma energy range 280 keV to 1115 keV

International Nuclear Information System (INIS)

Prasannakumar, S.; Umesh, T.K.

2014-01-01

The effective atomic number and effective electron densities of some inorganic compounds for Compton effect in the gamma energy range 280 keV to 1115 keV by using Compton scattering cross sections which are determined on a goniometer assembly. An ORTEC model 23210 gamma-x high purity germanium detector (HpGe) has been used to record the data along with a personal computer based MCA in the angular region 50°-110°. The effective atomic numbers so obtained were found to be equal to the total number of electrons present in the sample in accordance with the chemical formula. The results so obtained are of first of their kind at these energies and are expected to be important in a variety of applications of radiation physics and chemistry. (author)

Effective atomic numbers (Z_e_f_f) of based calcium phosphate biomaterials: a comparative study

International Nuclear Information System (INIS)

Fernandes Zenobio, Madelon Aparecida; Gonçalves Zenobio, Elton; Silva, Teógenes Augusto da; Socorro Nogueira, Maria do

2016-01-01

This study determined the interaction of radiation parameters of four biomaterials as attenuators to measure the transmitted X-rays spectra, the mass attenuation coefficient and the effective atomic number by spectrometric system comprising the CdTe detector. The biomaterial BioOss"® presented smaller mean energy than the other biomaterials. The μ/ρ and Z_e_f_f of the biomaterials showed their dependence on photon energy. The data obtained from analytical methods of x-ray spectra, µ/ρ and Z_e_f_f_, using biomaterials as attenuators, demonstrated that these materials could be used as substitutes for dentin, enamel and bone. Further, they are determinants for the characterization of the radiation in tissues or equivalent materials. - Highlights: • Measure of the transmitted x-rays spectra using based calcium phosphate biomaterials as attenuators. • Determination effective atomic number using four dental biomaterials. • Determination of the mass attenuation coefficient (µ/ρ) of the biomaterials samples calculated by the WinXCOM software. • Determination of the chemical composition of calcium phosphate biomaterials.

Effective atomic numbers and electron densities of some biologically important compounds containing H, C, N and O in the energy range 145-1330 keV

International Nuclear Information System (INIS)

Manjunathaguru, V; Umesh, T K

2006-01-01

A semi-empirical relation which can be used to determine the total attenuation cross sections of samples containing H, C, N and O in the energy range 145-1332 keV has been derived based on the total attenuation cross sections of several sugars, amino acids and fatty acids. The cross sections have been measured by performing transmission experiments in a narrow beam good geometry set-up by employing a high-resolution hyperpure germanium detector at seven energies of biological importance such as 145.4 keV, 279.2 keV, 514 keV, 661.6 keV, 1115.5 keV, 1173.2 keV and 1332.1 keV. The semi-empirical relation can reproduce the experimental values within 1-2%. The total attenuation cross sections of five elements carbon, aluminium, titanium, copper and zirconium measured in the same experimental set-up at the energies mentioned above have been used in a new matrix method to evaluate the effective atomic numbers and the effective electron densities of samples such as cholesterol, fatty acids, sugars and amino acids containing H, C, N and O atoms from their effective atomic cross sections. The effective atomic cross sections are the total attenuation cross sections divided by the total number of atoms of all types in a particular sample. Further, a quantity called the effective atomic weight was defined as the ratio of the molecular weight of a sample to the total number of atoms of all types in it. The variation of the effective atomic number was systematically studied with respect to the effective atomic weight and a new semi-empirical relation for Z eff has been evolved. It is felt that this relation can be very useful to determine the effective atomic number of any sample having H, C, N and O atoms in the energy range 145-1332 keV irrespective of its chemical structure

Electron density and effective atomic number (Zeff) determination through x-ray Moiré deflectometry

Science.gov (United States)

Valdivia Leiva, Maria Pia; Stutman, Dan; Finkenthal, Michael

2014-10-01

Talbot-Lau based Moiré deflectometry is a powerful density diagnostic capable of delivering refraction information and attenuation from a single image, through the accurate detection of X-ray phase-shift and intensity. The technique is able to accurately measure both the real part of the index of refraction δ (directly related to electron density) and the attenuation coefficient μ of an object placed in the x-ray beam. Since the atomic number Z (or Zeff for a composite sample) is proportional to these quantities, an elemental map of the effective atomic number can be obtained with the ratio of the phase and the absorption image. The determination of Zeff from refraction and attenuation measurements with Moiré deflectometry could be of high interest in various fields of HED research such as shocked materials and ICF experiments as Zeff is linked, by definition, to the x-ray absorption properties of a specific material. This work is supported by U.S. DoE/NNSA Grant No. 435 DENA0001835.

Effective atomic numbers in some food materials and medicines for γ -ray attenuation using ^{137}Cs γ -ray

Science.gov (United States)

Revathy, J. S.; Anooja, J.; Krishnaveni, R. B.; Gangadathan, M. P.; Varier, K. M.

2018-06-01

A light-weight multichannel analyser (MCA)-based γ -ray spectrometer, developed earlier at the Inter University Accelerator Centre, New Delhi, has been used as part of the PG curriculum, to determine the effective atomic numbers for γ attenuation of ^{137}Cs γ -ray in different types of samples. The samples used are mixtures of graphite, aluminum and selenium powders in different proportions, commercial and home-made edible powders, fruit and vegetable juices as well as certain allopathic and ayurvedic medications. A narrow beam good geometry set-up has been used in the experiments. The measured attenuation coefficients have been used to extract effective atomic numbers in the samples. The results are consistent with XCOM values wherever available. The present results suggest that the γ attenuation technique can be used as an effective non-destructive method for finding adulteration of food materials.

Determination of atomic number and composition of human enamel

International Nuclear Information System (INIS)

Nogueira, M.S.; Rodas Duran, J.E.

2001-01-01

The teeth are organs of complicated structure that consist, partly, of hard tissue containing in its interior the dental pulp, rich in vases and nerves. The main mass of the tooth is constituted by the dentine, which is covered with hard tissues and of epithelial origin called enamel. The dentine of the human teeth used in this work were completely removed and the teeth were cut with a device with a diamond disc. In this work the chemical composition of the human enamel was determined, which showed a high percentage of Ca and P, in agreement with the results found in the literature. The effective atomic number of the material and the half-value layer in the energy range of diagnostic X-ray beams were determined. Teeth could be used to evaluated the public's individual doses as well as for retrospective dosimetry what confirms the importance of their effective atomic number and composition determination. (author)

A versatile atomic number correction for electron-probe microanalysis

International Nuclear Information System (INIS)

Love, G.; Cox, M.G.; Scott, V.D.

1978-01-01

A new atomic number correction is proposed for quantitative electron-probe microanalysis. Analytical expressions for the stopping power S and back-scatter R factors are derived which take into account atomic number of the target, incident electron energy and overvoltage; the latter expression is established using Monte Carlo calculations. The correct procedures for evaluating S and R for multi-element specimens are described. The new method, which overcomes some limitations inherent in earlier atomic number corrections, may readily be used where specimens are inclined to the electron beam. (author)

Quantum phase crossovers with finite atom number in the Dicke model

International Nuclear Information System (INIS)

Hirsch, J G; Castaños, O; Nahmad-Achar, E; López-Peña, R

2013-01-01

Two-level atoms interacting with a one-mode cavity field at zero temperature have order parameters which reflect the presence of a quantum phase transition at a critical value of the atom–cavity coupling strength. Two popular examples are the number of photons inside the cavity and the number of excited atoms. Coherent states provide a mean field description, which becomes exact in the thermodynamic limit. Employing symmetry-adapted (SA) SU(2) coherent states the quantum crossover, precursor of the critical behavior, can be described for a finite number of atoms. A variation after projection treatment, involving a numerical minimization of the SA energy surface, associates the quantum crossover with a discontinuity in the order parameters, which originates from competition between two local minima in the SA energy surface. Although this discontinuity is not present in finite systems, it provides a good description of 1/N effects in the observables. (paper)

Studies on effective atomic numbers and electron densities in amino acids and sugars in the energy range 30-1333 keV

International Nuclear Information System (INIS)

Gowda, Shivalinge; Krishnaveni, S.; Gowda, Ramakrishna

2005-01-01

The effective atomic numbers and electron densities of the amino acids glycine, alanine, serine, valine, threonine, leucine, isoleucine, aspartic acid, lysine, glutamic acid, histidine, phenylalanine, arginine, tyrosine, tryptophane and the sugars arabinose, ribose, glucose, galactose, mannose, fructose, rhamnose, maltose, melibiose, melezitose and raffinose at the energies 30.8, 35.0, 81.0, 145, 276.4, 302.9, 356, 383.9, 661.6, 1173 and 1332.5 keV were calculated by using the measured total attenuation cross-sections. The interpolations of total attenuation cross-sections for photons of energy E in elements of atomic number Z was performed using the logarithmic regression analysis of the XCOM data in the photon energy region 30-1500 keV. The best-fit coefficients obtained by a piece wise interpolation method were used to find the effective atomic number and electron density of the compounds. These values are found to be in good agreement with the theoretical values calculated based on XCOM data

Studies on effective atomic numbers and electron densities in amino acids and sugars in the energy range 30-1333 keV

Energy Technology Data Exchange (ETDEWEB)

Gowda, Shivalinge [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore 570 006 (India); Krishnaveni, S. [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore 570 006 (India); Gowda, Ramakrishna [Department of Studies in Physics, University of Mysore, Manasagangotri, Mysore 570 006 (India)]. E-mail: ramakrishnagowda@yahoo.com

2005-10-15

The effective atomic numbers and electron densities of the amino acids glycine, alanine, serine, valine, threonine, leucine, isoleucine, aspartic acid, lysine, glutamic acid, histidine, phenylalanine, arginine, tyrosine, tryptophane and the sugars arabinose, ribose, glucose, galactose, mannose, fructose, rhamnose, maltose, melibiose, melezitose and raffinose at the energies 30.8, 35.0, 81.0, 145, 276.4, 302.9, 356, 383.9, 661.6, 1173 and 1332.5 keV were calculated by using the measured total attenuation cross-sections. The interpolations of total attenuation cross-sections for photons of energy E in elements of atomic number Z was performed using the logarithmic regression analysis of the XCOM data in the photon energy region 30-1500 keV. The best-fit coefficients obtained by a piece wise interpolation method were used to find the effective atomic number and electron density of the compounds. These values are found to be in good agreement with the theoretical values calculated based on XCOM data.

Studies on effective atomic number, electron density and kerma for some fatty acids and carbohydrates

International Nuclear Information System (INIS)

Manohara, S R; Hanagodimath, S M; Gerward, L

2008-01-01

The effective atomic number, Z eff , the effective electron density, N el , and kerma have been calculated for some fatty acids and carbohydrates for photon interaction in the extended energy range from 1 keV to 100 GeV using an accurate database of photon-interaction cross sections and the WinXCom program. The significant variation of Z eff and N el is due to the variations in the dominance of different interaction processes in different energy regions. The maximum values of Z eff and N el are found in the low-energy range, where photoelectric absorption is the main interaction process. The minimum values of Z eff and N el are found at intermediate energies, typically 0.05 MeV eff is equal to the mean atomic number of the bio-molecule. Wherever possible, the calculations are compared with experimental results. A comparison is also made with the single values of the Z eff and N el provided by the program XMuDat. It is also observed that carbohydrates have a larger kerma than fatty acids in the low-energy region, where photoelectric absorption dominates. In contrast, fatty acids have a larger kerma than carbohydrates in the MeV range, where Compton scattering is the main interaction process. (note)

Determination numbers of ionized atoms from emission and absorption lines

International Nuclear Information System (INIS)

Alizadeh Azimi, A.; Shokouhi, N.

2002-01-01

Saha, M., (1920) estimated that salter chromosphere is not only due to radiation from neutral atoms, but from ionized atoms. The failure to observe these stellar lines in the laboratory was attributed to internal temperature and pressure about 10* E + 6 K 10* E-7 atm. In this research we found that emission lines of ionized atoms (like Cs) could be measured in laboratory condition, (about 10* E-3 atm and 2000 K) by using Graphite France Atomic Absorption with injection 124 u g C sel. We calculated the numbers of ionized atoms from Bottzman law. We also measured these numbers from area under the energy-time curve

Successive change regularity of actinide properties with atomic number

International Nuclear Information System (INIS)

Yang Xuexian

1990-08-01

The development and achievements on chemistry of actinide elements are summarised. The relations of properties of actinides to their electronic configurations of valence electronic shells are discussed. Some anomalies of solid properties, the radius contraction, the stable state effect of f 7n -orbits (n = 0, 1, 2) and the tetrad effect of oxidation states, etc., with atomic number (Z) are described. 31 figures appended show directly the successive change regularity of actinide properties with Z

Effective atomic numbers for photon energy absorption of essential amino acids in the energy range 1 keV to 20 MeV

International Nuclear Information System (INIS)

Manohara, S.R.; Hanagodimath, S.M.

2007-01-01

Effective atomic numbers for photon energy-absorption (Z PEAeff ) of essential amino acids histidine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine have been calculated by a direct method in the energy region of 1 keV to 20 MeV. The Z PEAeff values have been found to change with energy and composition of the amino acids. The variations of mass energy-absorption coefficient, effective atomic number for photon interaction (Z PIeff ) and Z PEAeff with energy are shown graphically. Significant differences exist between Z PIeff and the Z PEAeff in the energy region of 8-100 keV for histidine and threonine; 6-100 keV for leucine, lysine, tryptophan, phenylalanine and valine; 15-400 keV for methionine. The effect of absorption edge on effective atomic numbers and the possibility of defining two set values of these parameters at the K-absorption edge of high-Z element present in the amino acids are discussed. The reasons for using Z PEAeff rather than the commonly used Z PIeff in medical radiation dosimetry for the calculation of absorbed dose in radiation therapy are also discussed

Investigation of systematic errors of metastable "atomic pair" number

CERN Document Server

Yazkov, V

2015-01-01

Sources of systematic errors in analysis of data, collected in 2012, are analysed. Esti- mations of systematic errors in a number of “atomic pairs” fr om metastable π + π − atoms are presented.

Analytical dependence of effective atomic number on the elemental composition of matter and radiation energy in the range 10-1000 keV

Science.gov (United States)

Eritenko, A. N.; Tsvetiansky, A. L.; Polev, A. A.

2018-01-01

In the present paper, a universal analytical dependence of effective atomic number on the composition of matter and radiation energy is proposed. This enables one to consider the case of a strong difference in the elemental composition with respect to their atomic numbers over a wide energy range. The contribution of photoelectric absorption and incoherent and coherent scattering during the interaction between radiation and matter is considered. For energy values over 40 keV, the contribution of coherent scattering does not exceed approximately 10% that can be neglected at a further consideration. The effective atomic numbers calculated on the basis of the proposed relationships are compared to the results of calculations based on other methods considered by different authors on the basis of experimental and tabulated data on mass and atomic attenuation coefficients. The examination is carried out for both single-element (e.g., 6C, 14Si, 28Cu, 56Ba, and 82Pb) and multi-element materials. Calculations are performed for W1-xCux alloys (x = 0.35; x = 0.4), PbO, ther moluminescent dosimetry compounds (56Ba, 48Cd, 41Sr, 20Ca, 12Mg, and 11Na), and SO4 in a wide energy range. A case with radiation energy between the K- and L1-absorption edges is considered for 82Pb, 74W, 56Ba, 48Cd, and 38Sr. This enables to substantially simplify the calculation of the atomic number and will be useful in technical and scientific fields related to the interaction between X-ray/gamma radiation and matter.

Stabilization of atoms with nonzero magnetic quantum numbers

International Nuclear Information System (INIS)

Sundaram, B.; Jensen, R.V.

1993-01-01

A classical analysis of the interaction of an atomic electron with an oscillating electric field with arbitrary initial quantum number, n, magnetic quantum number, m > 0, field strength, and frequency shows that the classical, dynamics for the perturbed electron can be stabilized for large fields and high frequencies. Using a four-dimensional map approximation to the classical dynamics, explicit expressions are obtained for the full parameter dependence of the boundaries of stability surrounding the open-quotes death valleyclose quotes of rapid classical ionization. A preliminary analysis of the quantum dynamics in terms of the quasienergy states associated with the corresponding quantum map is also included with particular emphasis on the role of unstable classical structures in stabilizing atoms. Together, these results provide motivation and direction for further theoretical and experimental studies of stabilization of atoms (and molecules) in super-intense microwave and laser fields

The Atomic Number Revolution in Chemistry: A Kuhnian Analysis

DEFF Research Database (Denmark)

Wray, K. Brad

2018-01-01

This paper argues that the field of chemistry underwent a significant change of theory in the early twentieth century, when atomic number replaced atomic weight as the principle for ordering and identifying the chemical elements. It is a classic case of a Kuhnian revolution. In the process of add...

Experimental observations of electron-backscatter effects from high-atomic-number anodes in large-aspect-ratio, electron-beam diodes

Energy Technology Data Exchange (ETDEWEB)

Cooperstein, G; Mosher, D; Stephanakis, S J; Weber, B V; Young, F C [Naval Research Laboratory, Washington, DC (United States); Swanekamp, S B [JAYCOR, Vienna, VA (United States)

1997-12-31

Backscattered electrons from anodes with high-atomic-number substrates cause early-time anode-plasma formation from the surface layer leading to faster, more intense electron beam pinching, and lower diode impedance. A simple derivation of Child-Langmuir current from a thin hollow cathode shows the same dependence on the diode aspect ratio as critical current. Using this fact, it is shown that the diode voltage and current follow relativistic Child-Langmuir theory until the anode plasma is formed, and then follows critical current after the beam pinches. With thin hollow cathodes, electron beam pinching can be suppressed at low voltages (< 800 kV) even for high currents and high-atomic-number anodes. Electron beam pinching can also be suppressed at high voltages for low-atomic-number anodes as long as the electron current densities remain below the plasma turn-on threshold. (author). 8 figs., 2 refs.

Improved atom number with a dual color magneto—optical trap

International Nuclear Information System (INIS)

Cao Qiang; Luo Xin-Yu; Gao Kui-Yi; Wang Xiao-Rui; Wang Ru-Quan; Chen Dong-Min

2012-01-01

We demonstrate a novel dual color magneto—optical trap (MOT), which uses two sets of overlapping laser beams to cool and trap 87 Rb atoms. The volume of cold cloud in the dual color MOT is strongly dependent on the frequency difference of the laser beams and can be significantly larger than that in the normal MOT with single frequency MOT beams. Our experiment shows that the dual color MOT has the same loading rate as the normal MOT, but much longer loading time, leading to threefold increase in the number of trapped atoms. This indicates that the larger number is caused by reduced light induced loss. The dual color MOT is very useful in experiments where both high vacuum level and large atom number are required, such as single chamber quantum memory and Bose—Einstein condensation (BEC) experiments. Compared to the popular dark spontaneous-force optical trap (dark SPOT) technique, our approach is technically simpler and more suitable to low power laser systems. (rapid communication)

A different perspective to the effective atomic number (Zeff) for some boron compounds and trommel sieve waste (TSW) with a new computer program ZXCOM

International Nuclear Information System (INIS)

Yalçın, Zeynel; İçelli, Orhan; Okutan, Mustafa; Boncukçuoğlu, Recep; Artun, Ozan; Orak, Salim

2012-01-01

In this study, the effective atomic number (Z eff )has been calculated for some boron compounds, such as concentrate colemanite, tincal, ulexite, boric acid, probertite and TSW (Trommel Sieve Waste) by means of ZXCOM at incident beam energy (E 0 =59.543 keV) and scattering angle (θ=35°). We present and discuss the (Z eff ) obtained by Rayleigh/Compton (R/C) ratio and evaluated for the purpose of radiation shielding which contains boron compounds, which are commonly used as shield materials. -- Highlights: ► The (Z eff ) of an infinite number of compounds will be determined according to the number actually consisting of elements which correspond to an integer number at the curve of ZXCOM. ► The result of this study shows that the effective atomic number (Z eff ) is closely related to the scattering angles. ► The main objective of the study is to construct a computer program, ZXCOM, to calculate the (Z eff ) at compromise (E 0 ) and (θ) for each element, compound and mixture.

Relativistic heavy-atom effects on heavy-atom nuclear shieldings

Science.gov (United States)

Lantto, Perttu; Romero, Rodolfo H.; Gómez, Sergio S.; Aucar, Gustavo A.; Vaara, Juha

2006-11-01

The principal relativistic heavy-atom effects on the nuclear magnetic resonance (NMR) shielding tensor of the heavy atom itself (HAHA effects) are calculated using ab initio methods at the level of the Breit-Pauli Hamiltonian. This is the first systematic study of the main HAHA effects on nuclear shielding and chemical shift by perturbational relativistic approach. The dependence of the HAHA effects on the chemical environment of the heavy atom is investigated for the closed-shell X2+, X4+, XH2, and XH3- (X =Si-Pb) as well as X3+, XH3, and XF3 (X =P-Bi) systems. Fully relativistic Dirac-Hartree-Fock calculations are carried out for comparison. It is necessary in the Breit-Pauli approach to include the second-order magnetic-field-dependent spin-orbit (SO) shielding contribution as it is the larger SO term in XH3-, XH3, and XF3, and is equally large in XH2 as the conventional, third-order field-independent spin-orbit contribution. Considering the chemical shift, the third-order SO mechanism contributes two-thirds of the difference of ˜1500ppm between BiH3 and BiF3. The second-order SO mechanism and the numerically largest relativistic effect, which arises from the cross-term contribution of the Fermi contact hyperfine interaction and the relativistically modified spin-Zeeman interaction (FC/SZ-KE), are isotropic and practically independent of electron correlation effects as well as the chemical environment of the heavy atom. The third-order SO terms depend on these factors and contribute both to heavy-atom shielding anisotropy and NMR chemical shifts. While a qualitative picture of heavy-atom chemical shifts is already obtained at the nonrelativistic level of theory, reliable shifts may be expected after including the third-order SO contributions only, especially when calculations are carried out at correlated level. The FC/SZ-KE contribution to shielding is almost completely produced in the s orbitals of the heavy atom, with values diminishing with the principal

On the effective atomic number and electron density: A comprehensive set of formulas for all types of materials and energies above 1 keV

DEFF Research Database (Denmark)

Manohara, S.R.; Hanagodimath, S.M.; Thind, K.S.

2008-01-01

A comprehensive and consistent set of formulas is given for calculating the effective atomic number and electron density for all types of materials and for all photon energies greater than 1 keV. The are derived from first principles using photon interaction cross sections of the constituent atom....... The theory is illustrated by calculations and experiments for molecules of medical and biological interest, glasses for radiation shielding, alloys, minerals and liquids....

Study of mass attenuation coefficients and effective atomic numbers of bismuth-ground granulated blast furnace slag concretes

International Nuclear Information System (INIS)

Kumar, Sandeep; Singh, Sukhpal

2016-01-01

Five samples of Bismuth-Ground granulated blast furnace slag (Bi-GGBFS) concretes were prepared using composition (0.6 cement + x Bi_2O_3 + (0.4-x) GGBFS, x = 0.05, 0.10, 0.15, 0.20 and 0.25) by keeping constant water (W) cement (C) ratio. Mass attenuation coefficients (μ_m) of these prepared samples were calculated using a computer program winXCOM at different gamma ray energies, whereas effective atomic numbers (Z_e_f_f) is calculated using mathematical formulas. The radiation shielding properties of Bi-GGBFS concrete has been compared with standard radiation shielding concretes.

Atom-number squeezing and bipartite entanglement of two-component Bose-Einstein condensates: analytical results

Energy Technology Data Exchange (ETDEWEB)

Jin, G R; Wang, X W; Li, D; Lu, Y W, E-mail: grjin@bjtu.edu.c [Department of Physics, Beijing Jiaotong University, Beijing 100044 (China)

2010-02-28

We investigate spin dynamics of a two-component Bose-Einstein condensate with weak Josephson coupling. Analytical expressions of atom-number squeezing and bipartite entanglement are presented for atom-atom repulsive interactions. For attractive interactions, there is no number squeezing; however, the squeezing parameter is still useful to recognize the appearance of Schroedinger's cat state.

Maximum compression of Z-pinch in a gas with high atomic number

International Nuclear Information System (INIS)

Gerusov, A.V.

1989-01-01

An ideal system of equations with shock heating is used for describing of a Z pinch in a gas with high atomic number. In this case equations do not depend from the installation parameters. The approximate simple solution of such a system is presented. Numerical calculations of equations with radiative cooling and various dissipative effects have determined the employment conditions of ideal magnetohydrodynamic equation system. 10 refs

Magic numbers and isotopic effect of ion clusters

International Nuclear Information System (INIS)

Wang Guanghou

1989-04-01

The magic numbers and isotopic effect as well as stable configurations in relation to the charge state of the clusters are discussed. Ionic (atomic) clusters are small atomic aggregates, a physical state between gas and solid states, and have many interesting properties, some of them are more or less similar to those in nuclei

Quantification of differences in the effective atomic numbers of healthy and cancerous tissues: A discussion in the context of diagnostics and dosimetry

Energy Technology Data Exchange (ETDEWEB)

Taylor, M. L. [School of Applied Sciences and Health Innovation Research Institute, RMIT University, Melbourne 3000 (Australia); Physical Sciences, Peter MacCallum Cancer Centre, East Melbourne 3001 (Australia) and Medical Physics, WBRC, Alfred Hospital, Melbourne 3000 (Australia)

2012-09-15

Purpose: There are a range of genetic and nongenetic factors influencing the elemental composition of different human tissues. The elemental composition of cancerous tissues frequently differs from healthy tissue of the same organ, particularly in high-Z trace element concentrations. For this reason, one could suggest that this may be exploited in diagnostics and perhaps even influence dosimetry. Methods: In this work, for the first time, effective atomic numbers are computed for common cancerous and healthy tissues using a robust, energy-dependent approach between 10 keV and 100 MeV. These are then quantitatively compared within the context of diagnostics and dosimetry. Results: Differences between effective atomic numbers of healthy and diseased tissues are found to be typically less than 10%. Fibrotic tissues and calcifications of the breast exhibit substantial (tens to hundreds of percent) differences to healthy tissue. Expectedly, differences are most pronounced in the photoelectric regime and consequently most relevant for kV imaging/therapy and radionuclides with prominent low-energy peaks. Cancerous tissue of the testes and stomach have lower effective atomic numbers than corresponding healthy tissues, while diseased tissues of the other organ sites typically have higher values. Conclusions: As dose calculation approaches improve in accuracy, there may be an argument for the explicit inclusion of pathologies. This is more the case for breast, penile, prostate, nasopharyngeal, and stomach cancer, less so for testicular and kidney cancer. The calculated data suggest dual-energy computed tomography could potentially improve lesion identification in the aforementioned organs (with the exception of testicular cancer), with most import in breast imaging. Ultimately, however, the differences are very small. It is likely that the assumption of a generic 'tissue ramp' in planning will be sufficient for the foreseeable future, and that the Z differences do

Quantification of differences in the effective atomic numbers of healthy and cancerous tissues: A discussion in the context of diagnostics and dosimetry

International Nuclear Information System (INIS)

Taylor, M. L.

2012-01-01

Purpose: There are a range of genetic and nongenetic factors influencing the elemental composition of different human tissues. The elemental composition of cancerous tissues frequently differs from healthy tissue of the same organ, particularly in high-Z trace element concentrations. For this reason, one could suggest that this may be exploited in diagnostics and perhaps even influence dosimetry. Methods: In this work, for the first time, effective atomic numbers are computed for common cancerous and healthy tissues using a robust, energy-dependent approach between 10 keV and 100 MeV. These are then quantitatively compared within the context of diagnostics and dosimetry. Results: Differences between effective atomic numbers of healthy and diseased tissues are found to be typically less than 10%. Fibrotic tissues and calcifications of the breast exhibit substantial (tens to hundreds of percent) differences to healthy tissue. Expectedly, differences are most pronounced in the photoelectric regime and consequently most relevant for kV imaging/therapy and radionuclides with prominent low-energy peaks. Cancerous tissue of the testes and stomach have lower effective atomic numbers than corresponding healthy tissues, while diseased tissues of the other organ sites typically have higher values. Conclusions: As dose calculation approaches improve in accuracy, there may be an argument for the explicit inclusion of pathologies. This is more the case for breast, penile, prostate, nasopharyngeal, and stomach cancer, less so for testicular and kidney cancer. The calculated data suggest dual-energy computed tomography could potentially improve lesion identification in the aforementioned organs (with the exception of testicular cancer), with most import in breast imaging. Ultimately, however, the differences are very small. It is likely that the assumption of a generic “tissue ramp” in planning will be sufficient for the foreseeable future, and that the Z differences do not

Low atomic number coating for XEUS silicon pore optics

Science.gov (United States)

Lumb, D. H.; Jensen, C. P.; Krumrey, M.; Cibik, L.; Christensen, F.; Collon, M.; Bavdaz, M.

2008-07-01

We describe a set of measurements on coated silicon substrates that are representative of the material to be used for the XEUS High Performance Pore Optics (HPO) technology. X-ray angular reflectance measurements at 2.8 and 8 keV, and energy scans of reflectance at a fixed angle representative of XEUS graze angles are presented. Reflectance is significantly enhanced for low energies when a low atomic number over-coating is applied. Modeling of the layer thicknesses and roughness is used to investigate the dependence on the layer thicknesses, metal and over coat material choices. We compare the low energy effective area increase that could be achieved with an optimized coating design.

Nanoarchitectonics for Controlling the Number of Dopant Atoms in Solid Electrolyte Nanodots.

Science.gov (United States)

Nayak, Alpana; Unayama, Satomi; Tai, Seishiro; Tsuruoka, Tohru; Waser, Rainer; Aono, Masakazu; Valov, Ilia; Hasegawa, Tsuyoshi

2018-02-01

Controlling movements of electrons and holes is the key task in developing today's highly sophisticated information society. As transistors reach their physical limits, the semiconductor industry is seeking the next alternative to sustain its economy and to unfold a new era of human civilization. In this context, a completely new information token, i.e., ions instead of electrons, is promising. The current trend in solid-state nanoionics for applications in energy storage, sensing, and brain-type information processing, requires the ability to control the properties of matter at the ultimate atomic scale. Here, a conceptually novel nanoarchitectonic strategy is proposed for controlling the number of dopant atoms in a solid electrolyte to obtain discrete electrical properties. Using α-Ag 2+ δ S nanodots with a finite number of nonstoichiometry excess dopants as a model system, a theory matched with experiments is presented that reveals the role of physical parameters, namely, the separation between electrochemical energy levels and the cohesive energy, underlying atomic-scale manipulation of dopants in nanodots. This strategy can be applied to different nanoscale materials as their properties strongly depend on the number of doping atoms/ions, and has the potential to create a new paradigm based on controlled single atom/ion transfer. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effects of non-LTE multiplet dynamics on lumped-state modelling in moderate to high atomic number plasmas

International Nuclear Information System (INIS)

Whitney, K G; Dasgupta, A; Davis, J; Coverdale, C A

2007-01-01

Two atomic models of the population dynamics of substates within the n 4 and n = 3 multiplets of nickel-like tungsten and beryllium-like iron, respectively, are described in this paper. The flexible atomic code (FAC) is used to calculate the collisional and radiative couplings and energy levels of the excited states within these ionization stages. These atomic models are then placed within larger principal-quantum-number-based ionization dynamic models of both tungsten and iron plasmas. Collisional-radiative equilibrium calculations are then carried out using these models that demonstrate how the multiplet substates depart from local thermodynamic equilibrium (LTE) as a function of ion density. The effect of these deviations from LTE on the radiative and collisional deexcitation rates of lumped 3s, 3p, 3d, 4s, 4p, 4d and 4f states is then calculated and least-squares fits to the density dependence of these lumped-state rate coefficients are obtained. The calculations show that, with the use of lumped-state models (which are in common use), one can accurately model the L- and M-shell ionization dynamics occurring in present-day Z-pinch experiments only through the addition of these extra, non-LTE-induced, rate coefficient density dependences. However, the derivation and use of low-order polynomial fits to these density dependences makes lumped-state modelling both viable and of value for post-processing analyses

Experimental study of stopping powers for ions of intermediate atomic numbers

International Nuclear Information System (INIS)

Bucher, R.G.

1975-01-01

A technique has been developed to measure the energy loss as a function of ion atomic number for the fragments emitted by the spontaneous fission of 252 Cf; the atomic numbers of the fragments were directly measured by the detection of a characteristic K x-ray. The measured energy losses were compared with the theories of Lindhard and of Firsov, with the tabulation of Northcliffe and Schilling, and with the semiempirical formula of Moak and Brown. For the light fragments the measured values are in good agreement with the predictions of Moak--Brown and Northcliffe--Schilling; for the heavy fragments the measured values are approximately midway between the prediction of Moak--Brown and Northcliffe--Schilling and those of Lindhard for xi/sub epsilon/ = 2. The difference in the stopping powers for adjacent ion atomic numbers Z 1 was concluded to be (1.8 +- 0.2) percent for 40 less than or equal to Z 1 less than or equal to 45 at a velocity of 1.36 cm/ns and (2.0 +- 0.1) percent for 53 less than or equal to Z 1 less than or equal to 58 at a velocity of 1.04 cm/ns

Platinum clusters with precise numbers of atoms for preparative-scale catalysis.

Science.gov (United States)

Imaoka, Takane; Akanuma, Yuki; Haruta, Naoki; Tsuchiya, Shogo; Ishihara, Kentaro; Okayasu, Takeshi; Chun, Wang-Jae; Takahashi, Masaki; Yamamoto, Kimihisa

2017-09-25

Subnanometer noble metal clusters have enormous potential, mainly for catalytic applications. Because a difference of only one atom may cause significant changes in their reactivity, a preparation method with atomic-level precision is essential. Although such a precision with enough scalability has been achieved by gas-phase synthesis, large-scale preparation is still at the frontier, hampering practical applications. We now show the atom-precise and fully scalable synthesis of platinum clusters on a milligram scale from tiara-like platinum complexes with various ring numbers (n = 5-13). Low-temperature calcination of the complexes on a carbon support under hydrogen stream affords monodispersed platinum clusters, whose atomicity is equivalent to that of the precursor complex. One of the clusters (Pt 10 ) exhibits high catalytic activity in the hydrogenation of styrene compared to that of the other clusters. This method opens an avenue for the application of these clusters to preparative-scale catalysis.The catalytic activity of a noble metal nanocluster is tied to its atomicity. Here, the authors report an atom-precise, fully scalable synthesis of platinum clusters from molecular ring precursors, and show that a variation of only one atom can dramatically change a cluster's reactivity.

Mass attenuation coefficients, effective atomic and electron numbers of stainless steel and carbon steels with different energies

International Nuclear Information System (INIS)

Mohd Fakarudin Abdul Rahman; Mohd Iqbal Saripan; Nor Paiza Mohamad Hasan; Ismail Mustapha

2011-01-01

The total mass attenuation coefficients (μ/ ρ) of stainless steel (SS316L) and carbon steel (A516) that are widely used as petrochemical plant components, such as distillation column, heat exchanger, boiler and storage tank were measured at 662, 1073 and 1332 keV of photon energies. Measurements of radiation intensity for various thicknesses of steel were made by using transmission method. The γ-ray intensity were counted by using a Gamma spectrometer that contains a Hyper-pure Germanium (HPGe) detector connected with Multi Channel Analyzer (MCA). The effective numbers of atomic (Z eff ) and electron (N eff ) obtained experimentally were compared by those obtained through theoretical calculation. Both experimental and calculated values of Z eff and N eff were in good agreement. (author)

Study of effective atomic number of breast tissues determined using the elastic to inelastic scattering ratio

International Nuclear Information System (INIS)

Antoniassi, M.; Conceicao, A.L.C.; Poletti, M.E.

2011-01-01

In this work we have measured Compton and Rayleigh scattering radiation from normal (adipose and fibroglandular), benign (fibroadenoma) and malignant (ductal carcinoma) breast tissues using a monoenergetic beam of 17.44 keV and a scattering angle of 90 o (x=0.99 A -1 ). A practical method using the area of Rayleigh and Compton scattering was used for determining the effective atomic number (Z eff ) of the samples, being validated through measurements of several reference materials. The results show that there are differences in the distributions of Z eff of breast tissues, which are mainly related to the elemental composition of carbon (Z=6) and oxygen (Z=8) of each tissue type. The results suggest that is possible to use the method to characterize the breast tissues permitting study histological features of the breast tissues related to their elemental composition.

Study of effective atomic number of breast tissues determined using the elastic to inelastic scattering ratio

Science.gov (United States)

Antoniassi, M.; Conceição, A. L. C.; Poletti, M. E.

2011-10-01

In this work we have measured Compton and Rayleigh scattering radiation from normal (adipose and fibroglandular), benign (fibroadenoma) and malignant (ductal carcinoma) breast tissues using a monoenergetic beam of 17.44 keV and a scattering angle of 90° ( x=0.99 Å -1). A practical method using the area of Rayleigh and Compton scattering was used for determining the effective atomic number ( Zeff) of the samples, being validated through measurements of several reference materials. The results show that there are differences in the distributions of Zeff of breast tissues, which are mainly related to the elemental composition of carbon ( Z=6) and oxygen ( Z=8) of each tissue type. The results suggest that is possible to use the method to characterize the breast tissues permitting study histological features of the breast tissues related to their elemental composition.

Chemical effects of /sup 32/P recoil atom

Energy Technology Data Exchange (ETDEWEB)

Matsuura, N [Tokyo Univ. (Japan). Coll. of General Education

1975-06-01

Szilard-Chalmers' effect of /sup 32/P were reviewed. The concentration method using Szilard-Chalmers' effect in production of radioisotope, circumstances such as exposure time in an atomic pile, states of target substances and the yields by them were discussed. Many kinds of chemical effects, such as chemical effects of /sup 32/P recoil atom in phosphorated glass, studies of the effect of adducts, the threshold of ..gamma..-ray effect, the oxidation number of /sup 32/P in phosphorated glass by exposure time in the pile and the labelling position of /sup 32/P, are associated with caryotransformation (nuclear transformation) by environmental factors. The abovementioned articles were explained concerning /sup 32/P.

The method of intersecting spheres for determination of coordination numbers of atoms in crystal structures

International Nuclear Information System (INIS)

Serezhkin, V.N.; Buslaev, Yu.A.; Mikhajlov, Yu.N.

1997-01-01

New method for determination of coordination numbers (CN) of atoms in crystal structures, based on the model of interatomic interaction, within the frames whereof each atom is approximated by two spheres with the common center in the atom nuclei, is proposed. One of the spheres specifies conditionally isolated (chemically unbound) atom and its radius is a constant, which for atoms of the given chemical sort in the structure of any compound is equal to quasi-orbital Sleiter radius. The sphere of the other radius specifies chemically bound atom and coincides with the sphere, the volume whereof is equal to the volume of the Voronoj-Dirichlet polyhedron of the corresponding atom in the structure of the concrete crystal. Using a series of examples, workability of the given method for CN determination of atoms in structures of both simple substances and chemical compounds (alkali, transition metals, U, Th). Good agreement of the obtained results with the generally accepted CN s of atoms for the considered crystals is noted and a number of principal advantages of the new method, as compared to classical one of the CNs evaluation, is demonstrated

Study of effective atomic number of breast tissues determined using the elastic to inelastic scattering ratio

Energy Technology Data Exchange (ETDEWEB)

Antoniassi, M.; Conceicao, A.L.C. [Departamento de Fisica e Matematica, Faculdade de Filosofia Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, Ribeirao Preto, Sao Paulo (Brazil); Poletti, M.E., E-mail: poletti@ffclrp.usp.br [Departamento de Fisica e Matematica, Faculdade de Filosofia Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, Ribeirao Preto, Sao Paulo (Brazil)

2011-10-01

In this work we have measured Compton and Rayleigh scattering radiation from normal (adipose and fibroglandular), benign (fibroadenoma) and malignant (ductal carcinoma) breast tissues using a monoenergetic beam of 17.44 keV and a scattering angle of 90{sup o} (x=0.99 A{sup -1}). A practical method using the area of Rayleigh and Compton scattering was used for determining the effective atomic number (Z{sub eff}) of the samples, being validated through measurements of several reference materials. The results show that there are differences in the distributions of Z{sub eff} of breast tissues, which are mainly related to the elemental composition of carbon (Z=6) and oxygen (Z=8) of each tissue type. The results suggest that is possible to use the method to characterize the breast tissues permitting study histological features of the breast tissues related to their elemental composition.

Two-Dimensional SnO Anodes with a Tunable Number of Atomic Layers for Sodium Ion Batteries

KAUST Repository

Zhang, Fan; Zhu, Jiajie; Zhang, Daliang; Schwingenschlö gl, Udo; Alshareef, Husam N.

2017-01-01

We have systematically changed the number of atomic layers stacked in 2D SnO nanosheet anodes and studied their sodium ion battery (SIB) performance. The results indicate that as the number of atomic SnO layers in a sheet decreases, both

Calculation of the number of atoms displaced during the irradiation of monolayer graphene

International Nuclear Information System (INIS)

Daniel Codorniu Pujals; Yuri Aguilera Corrales; Francesco Baldassarre

2011-01-01

The irradiation of monolayer graphene, combined with chemical functionalization, could be an effective method for modifying its electronic structure and for achieving specific physical properties adjusted to different applications. A difficulty arising during planning and studying the irradiation in this system is that many of the models of interaction of the radiation with the substance cannot be applied to the two-dimensional structure of graphene. In particular, the mathematical expressions available to calculate the number of atoms displaced during the bombardment with particles can be applied only to 3D isotropic solids. In the present work, an alternative analytic expression is presented for the irradiation of graphene with heavy ions or with protons and other light charged particles. The expression was obtained on the basis of the classic theory of dispersion, using a Coulomb potential for the light charged particles and one of Inverse Square for heavy ions. For medium values of the energy of the incident particle a decreasing dependence of the number of displaced atoms with energy is obtained. This behavior, related with the two-dimensional structure of the target, had been observed in other authors' works using computational simulation. (author)

An x ray scatter approach for non-destructive chemical analysis of low atomic numbered elements

Science.gov (United States)

Ross, H. Richard

1993-01-01

A non-destructive x-ray scatter (XRS) approach has been developed, along with a rapid atomic scatter algorithm for the detection and analysis of low atomic-numbered elements in solids, powders, and liquids. The present method of energy dispersive x-ray fluorescence spectroscopy (EDXRF) makes the analysis of light elements (i.e., less than sodium; less than 11) extremely difficult. Detection and measurement become progressively worse as atomic numbers become smaller, due to a competing process called 'Auger Emission', which reduces fluorescent intensity, coupled with the high mass absorption coefficients exhibited by low energy x-rays, the detection and determination of low atomic-numbered elements by x-ray spectrometry is limited. However, an indirect approach based on the intensity ratio of Compton and Rayleigh scattered has been used to define light element components in alloys, plastics and other materials. This XRS technique provides qualitative and quantitative information about the overall constituents of a variety of samples.

Radio-isotopic apparatus for analyzing low atomic number elements by fluorescence

International Nuclear Information System (INIS)

Robert, Andre; Martinelli, Pierre; Daniel, Georges; Laflotte, Jean-Luc

1969-10-01

An apparatus is described for analyzing light elements of atomic number between 6 and 24 by X-fluorescence. The samples are excited by means of X or α isotopic sources. Various examples of analytical determinations are given. (author) [fr

Advances in low atomic number element analysis by wavelength dispersive x-ray fluorescence spectrometry

International Nuclear Information System (INIS)

Vrebos, B.

1996-01-01

Traditionally, the analysis of low atomic number has been a chal1enging task for wavelength dispersive x-ray fluorescence spectrometry. Among the most important factors influencing analysis of the low atomic number elements (from Z=11 downwards) are the fluorescence yield, absorption and the dispersion. The effect of each of these factors on the overall performance will be illustrated. The long wavelengths involved (longer than I nm) used to pose severe problems concerning the monochromator used. Early instruments relied on lead stearate or Blodgett Langmuir soap films for the diffraction of the characteristic radiation. Nowadays, synthetic multilayers are commonly used. The performance of these multilayers is determined by the reflectivity, the resolution and the absorption of the characteristic radiation to be diffracted. These parameters can be optimised by adequately selecting the composition of the materials involved. The sensitivity of the modem instruments is sufficient to allow quantitative analysis. However, this aspect of WDS XRF is still met with considerable scepticism. Examples of quantitative analysis will be given to illustrate the current capability

Effect of temperature on atom-atom collision chain length in metals

International Nuclear Information System (INIS)

Makarov, A.A.; Demkin, N.A.; Lyashchenko, B.G.

1981-01-01

Focused atom-atom collision chain lengths are calculated for fcc-crystals with account of thermal oscillations. The model of solid spheres with the Born-Merier potential has been used in the calculations. The dependence of chain lengths on the temperature, energy and movement direction of the first chain atom for Cu, Au, Ag, Pb, Ni is considered. The plot presented shows that the chain lengths strongly decrease with temperature growth, for example, for the gold at T=100 K the chain length equals up to 37 interatomic spacings, whereas at T=1000 K their length decreases down to 5 interatomic distances. The dependence of the energy loss by the chain atoms on the atom number in the chain is obtained in a wide range of crystal temperature and the primary chain atom energy [ru

[Measurement of atomic number of alkali vapor and pressure of buffer gas based on atomic absorption].

Science.gov (United States)

Zheng, Hui-jie; Quan, Wei; Liu, Xiang; Chen, Yao; Lu, Ji-xi

2015-02-01

High sensitivitymagnetic measurementscanbe achieved by utilizing atomic spinmanipulation in the spin-exchange-relaxation-free (SERF) regime, which uses an alkali cell as a sensing element. The atomic number density of the alkali vapor and the pressure of the buffer gasare among the most important parameters of the cell andrequire accurate measurement. A method has been proposed and developedto measure the atomic number density and the pressure based on absorption spectroscopy, by sweeping the absorption line and fittingthe experiment data with a Lorentzian profile to obtainboth parameters. Due to Doppler broadening and pressure broadening, which is mainly dominated by the temperature of the cell and the pressure of buffer gas respectively, this work demonstrates a simulation of the errorbetween the peaks of the Lorentzian profile and the Voigt profile caused by bothfactors. The results indicates that the Doppler broadening contribution is insignificant with an error less than 0.015% at 313-513 K for a 4He density of 2 amg, and an error of 0.1% in the presence of 0.6-5 amg at 393 K. We conclude that the Doppler broadening could be ignored under above conditions, and that the Lorentzianprofile is suitably applied to fit the absorption spectrumobtainingboth parameters simultaneously. In addition we discuss the resolution and the instability due to thelight source, wavelength and the temperature of the cell. We find that the cell temperature, whose uncertainty is two orders of magnitude larger than the instability of the light source and the wavelength, is one of the main factors which contributes to the error.

On the atomic-number similarity of the binding energies of electrons in filled shells of elements of the periodic table

Science.gov (United States)

Karpov, V. Ya.; Shpatakovskaya, G. V.

2017-03-01

An expression for the binding energies of electrons in the ground state of an atom is derived on the basis of the Bohr-Sommerfeld quantization rule within the Thomas-Fermi model. The validity of this relation for all elements from neon to uranium is tested within a more perfect quantum-mechanical model with and without the inclusion of relativistic effects, as well as with experimental binding energies. As a result, the ordering of electronic levels in filled atomic shells is established, manifested in an approximate atomic-number similarity. It is proposed to use this scaling property to analytically estimate the binding energies of electrons in an arbitrary atom.

On the atomic-number similarity of the binding energies of electrons in filled shells of elements of the periodic table

Energy Technology Data Exchange (ETDEWEB)

Karpov, V. Ya. [Bruk Institute of Electronic Control Machines (Russian Federation); Shpatakovskaya, G. V., E-mail: shpagalya@yandex.ru [Russian Academy of Sciences, Keldysh Institute of Applied Mathematics (Russian Federation)

2017-03-15

An expression for the binding energies of electrons in the ground state of an atom is derived on the basis of the Bohr–Sommerfeld quantization rule within the Thomas–Fermi model. The validity of this relation for all elements from neon to uranium is tested within a more perfect quantum-mechanical model with and without the inclusion of relativistic effects, as well as with experimental binding energies. As a result, the ordering of electronic levels in filled atomic shells is established, manifested in an approximate atomic-number similarity. It is proposed to use this scaling property to analytically estimate the binding energies of electrons in an arbitrary atom.

Fragmented metastable states exist in an attractive bose-einstein condensate for atom numbers well above the critical number of the Gross-Pitaevskii theory.

Science.gov (United States)

Cederbaum, Lorenz S; Streltsov, Alexej I; Alon, Ofir E

2008-02-01

It is well known that attractive condensates do not posses a stable ground state in three dimensions. The widely used Gross-Pitaevskii theory predicts the existence of metastable states up to some critical number N(cr)(GP) of atoms. It is demonstrated here that fragmented metastable states exist for atom numbers well above N(cr)(GP). The fragments are strongly overlapping in space. The results are obtained and analyzed analytically as well as numerically. The implications are discussed.

A study of energy and effective atomic number dependence of the exposure build-up factors in biological samples

International Nuclear Information System (INIS)

Sidhu, G.S.; Singh, P.S.; Mudahar, G.S.

2000-01-01

A theoretical method is presented to determine the gamma-radiation build-up factors in various biological materials. The gamma energy range is 0.015-15.0 MeV, with penetration depths up to 40 mean free paths considered. The dependence of the exposure build-up factor on incident photon energy and the effective atomic number (Z eff ) has also been assessed. In a practical analysis of dose burden to gamma-irradiated biological materials, the sophistication of Monte Carlo computer techniques would be applied, with associated detailed modelling. However, a feature of the theoretical method presented is its ability to make the consequences of the physics of the scattering process in biological materials more transparent. In addition, it can be quickly employed to give a first-pass dose estimate prior to a more detailed computer study. (author)

Critical radius and critical number of gas atoms for cavities containing a Van der Waals gas

International Nuclear Information System (INIS)

Coghlan, W.A.; Mansur, L.K.

1983-01-01

The effect of gas on void nucleation and growth is particularly important for structural materials in fusion reactors because of the high production of helium by neutron-induced transmutation reactions. Gas reduces the critical radius for bias driven growth and there is a critical number of gas atoms, n/sub g/*, at which the critical radius is reduced essentially to zero. The significance of this is that the time interval to the accumulation of n/sub g/* gas atoms may determine the time to the onset of bias driven swelling where n/sub g/* is large. In previous papers these critical quantities were given for an ideal gas. Recently, we presented the results for a Van der Waals gas. Here the derivation of these relations is presented and further results of calculations are given. At low temperatures (high pressures) the results depart from those of the ideal gas, with the critical number affected more strongly than the critical radius. Comparisons are made with earlier calculations

A study of the effective atomic number of SixPb0.7-x(Fe2O30.3 ternary alloys for photons

Directory of Open Access Journals (Sweden)

Buyukyildiz Mehmet

2016-01-01

Full Text Available The effective atomic number (Zeff of SixPb0.7-x(Fe2O30.3 ternary alloys was obtained for photons. Rayleigh to Compton scattering ratio (R/C has been determined to obtain the Zeff of SixPb0.7-x(Fe2O30.3 ternary alloys of varying Si and Pb (10 %-60 % content for scattering of 59.54 keV g-rays at an angle of 130°. The theoretical R/C ratios of elements were plotted as a function of the atomic number and fitted to a polynomial equation. Experimental R/C values of alloys were then used to obtain Zeff using this fit equation. Also, Zeff values of these alloys were determined for the first time by interpolating the R/C of the material using the R/C data of adjacent elements in between the R/C of the alloy lies. The agreement between the interpolation method and the fit equation was quite satisfactory. The obtained Zeff for photon scattering were then compared to the Zeff for total photon attenuation obtained using the Auto-Zeff program. Significant variations were observed between the Zeff for scattering and the total attenuation of gamma rays.

Cell-killing efficiency and number of platinum atoms binding to DNA, RNA and protein molecules of HeLa cells treated with combinations of hyperthermia and carboplatin

International Nuclear Information System (INIS)

Akaboshi, M.; Kawai, K.; Tanaka, Y.; Takada, J.; Sumino, T.

1999-01-01

The effect of hyperthermia on the cell killing efficiency of Pt atoms binding to DNA, RNA and protein molecules of HeLa cells treated with cis-diamine(1,1-cyclobutanedicarboxylato)platinum(II) (CBDCA) was examined. HeLa S-3 cells were treated with 195m Pt-radiolabeled CBDCA for 60 minutes at various temperatures, and the relationship between the lethal effect and the number of Pt atoms binding to DNA, RNA and proteins was examined. The mean lethal concentration (D 0 ) of carboplatin for a 60 min-treatment at 0, 25, 37, 40, 42 and 44 deg C was 671.2, 201.5, 67.3, 33.4, 20.2 and 15.6 μM, respectively. By using identically treated cells, the number of Pt-atoms combined with DNA, RNA and protein molecules were determined in the subcellular fractions. Thus, the D 0 's given as the drug concentrations were replaced with the number of Pt-atoms combined in each fraction. Then, the cell-killing efficiency of the Pt atom was expressed as the reciprocal of the number of Pt-atoms combined and was calculated for each molecule. The efficiency for DNA molecules was 0.699, 1.42, 2.65, 4.84, 7.74 and 8.28x10 4 nucleotides, respectively, for the conditions described above. From 0 to 44 deg C, the cell-killing efficiency of Pt atoms increased by a factor of 11.9. (author)

Effect of atomic disorder on the magnetic phase separation

Science.gov (United States)

Groshev, A. G.; Arzhnikov, A. K.

2018-05-01

The effect of disorder on the magnetic phase separation between the antiferromagnetic and incommensurate helical and phases is investigated. The study is based on the quasi-two-dimensional single-band Hubbard model in the presence of atomic disorder (the Anderson–Hubbard model). A model of binary alloy disorder is considered, in which the disorder is determined by the difference in energy between the host and impurity atomic levels at a fixed impurity concentration. The problem is solved within the theory of functional integration in static approximation. Magnetic phase diagrams are obtained as functions of the temperature, the number of electrons and impurity concentration with allowance for phase separation. It is shown that for the model parameters chosen, the disorder caused by impurities whose atomic-level energy is greater than that of the host atomic levels, leads to qualitative changes in the phase diagram of the impurity-free system. In the opposite case, only quantitative changes occur. The peculiarities of the effect of disorder on the phase separation regions of the quasi-two-dimensional Hubbard model are discussed.

Importance of the effective atomic number (Zeff) of TL materials for radiation dosimetry in clinical applications

International Nuclear Information System (INIS)

Gonzalez M, P.R.

2008-01-01

The electric power generation, it has been one of the radiation applications of bigger weight, mainly in developed countries. Another sector of more impact is without a doubt that of the medicine. However, for a sure operation with radiations, those international organisms of radiological safety, exist every time more precise detection systems. The thermoluminescent dosimetry is one of the more reliable methods for this purpose, for that several groups of investigators from different parts of the world, they have guided its investigations in the development of new TL materials. However, to avoid underestimate or overestimation of the measured dose with the use of these materials, it should take into account it effective atomic number (Z eff ) it is well known that some TL materials considered as equivalent to the tissue, presents smaller TL intensity when being irradiated with low energy photons, while the TL material known as not equivalent to the tissue, they present the supra sensitivity effect for this radiation type. Nowadays, the estimate of the Z eff has not been clear, in this work the Z eff is determined by means of the traditional methods and an own method is presented for its determination. The results of the TL signal of different materials, when being irradiated with photons of effective energy between 24 keV and 1.25 MeV and their relationship with their calculated Z eff are also presented. (Author)

Determination of atomic number and composition of human enamel; Determinacao da composicao e numero atomico efetivo do esmalte humano

Energy Technology Data Exchange (ETDEWEB)

Nogueira, M.S. [Centro Regional de Ciencias Nucleares (CRCN), Recife, PE (Brazil); Rodas Duran, J.E. [Sao Paulo Univ., Ribeirao Preto, SP (Brazil). Faculdade de Filosofia, Ciencias e Letras. Dept. de Fisica e Matematica

2001-07-01

The teeth are organs of complicated structure that consist, partly, of hard tissue containing in its interior the dental pulp, rich in vases and nerves. The main mass of the tooth is constituted by the dentine, which is covered with hard tissues and of epithelial origin called enamel. The dentine of the human teeth used in this work were completely removed and the teeth were cut with a device with a diamond disc. In this work the chemical composition of the human enamel was determined, which showed a high percentage of Ca and P, in agreement with the results found in the literature. The effective atomic number of the material and the half-value layer in the energy range of diagnostic X-ray beams were determined. Teeth could be used to evaluated the public's individual doses as well as for retrospective dosimetry what confirms the importance of their effective atomic number and composition determination. (author)

Synthesis of a New Element with Atomic Number Z=117

International Nuclear Information System (INIS)

Oganessian, Yu. Ts.; Abdullin, F. Sh.; Dmitriev, S. N.; Itkis, M. G.; Lobanov, Yu. V.; Mezentsev, A. N.; Polyakov, A. N.; Sagaidak, R. N.; Shirokovsky, I. V.; Subbotin, V. G.; Sukhov, A. M.; Tsyganov, Yu. S.; Utyonkov, V. K.; Voinov, A. A.; Vostokin, G. K.; Bailey, P. D.; Benker, D. E.; Ezold, J. G.; Porter, C. E.; Riley, F. D.

2010-01-01

The discovery of a new chemical element with atomic number Z=117 is reported. The isotopes 293 117 and 294 117 were produced in fusion reactions between 48 Ca and 249 Bk. Decay chains involving 11 new nuclei were identified by means of the Dubna gas-filled recoil separator. The measured decay properties show a strong rise of stability for heavier isotopes with Z≥111, validating the concept of the long sought island of enhanced stability for superheavy nuclei.

Low atomic number coating for XEUS silicon pore optics

DEFF Research Database (Denmark)

Lumb, D.H.; Cooper-Jensen, Carsten P.; Krumrey, M.

2008-01-01

We describe a set of measurements on coated silicon substrates that are representative of the material to be used for the XEUS High Performance Pore Optics (HPO) technology. X-ray angular reflectance measurements at 2.8 and 8 keV, and energy scans of reflectance at a fixed angle representative...... of XEUS graze angles are presented. Reflectance is significantly enhanced for low energies when a low atomic number over-coating is applied. Modeling of the layer thicknesses and roughness is used to investigate the dependence on the layer thicknesses, metal and over coat material choices. We compare...

Multielectron effects in atomic processes

International Nuclear Information System (INIS)

Amusia, M.Ya.; Chernysheva, L.V.

1999-01-01

One demonstrates a prominent role of electron collectivization in atoms and quasi-atomic formations. Paper discusses in detail the approximation of random phases with exchange enabling to take account of these effects. One points out the necessity to go outside the terms of the approximation when studying some processes via combination of the approximation with the theory of disturbances. The results of the recently conducted estimations of cross sections of photoionization of atomic iodine and of its positive and negative ions, Xe + single-electron photoionization, resonance-amplified emission of photons in electron collisions with atoms and quasi-atomic formations, non-dipole corrections to the angular distribution of photoelectrons, probabilities of two electron transitions where the whole amount of energy releases in the form of one photon, illustrate the role of the collective effects [ru

Study of the relationship between peaks scattering Rayleigh to Compton ratio and effective atomic number in biological samples

International Nuclear Information System (INIS)

Pereira, Marcelo O.; Conti, Claudio de Carvalho; Anjos, Marcelino J.; Lopes, Ricardo T.

2011-01-01

The aim of this work was to develop a new method to correct the absorbed radiation (the mass attenuation coefficient curve) in low energy (E B O 3 , Na 2 CO 3 , CaCO 3 , Al 2 O 3 , K 2 SO 4 and MgO) of radiation produced by a gamma-ray source of Am-241(59.54 keV) also applied to certified biological samples of milk powder, hay powder and bovine liver (NIST 155 7B). In addition, six methods of effective atomic number determination were used as described in literature to determinate the Rayleigh to Compton scattering ratio (R/C) , in order to calculate the mass attenuation coefficient. The results obtained by the proposed method were compared with those obtained using the transmission method. The experimental results were in good agreement with transmission values suggesting that the method to correct radiation absorption presented in this paper is adequate for biological samples. (author)

Effective atomic numbers, electron densities, and tissue equivalence of some gases and mixtures for dosimetry of radiation detectors

Directory of Open Access Journals (Sweden)

Singh Vishwanath P.

2012-01-01

Full Text Available Total mass attenuation coefficients, µm, effective atomic number, Zeff, and effective electron density, Neff, of different gases - carbon dioxide, methane, acetylene, propane, butane, and pentane used in radiation detectors, have been calculated for the photon energy of 1 keV to 100 GeV. Each gas has constant Zeff values between 0.10 to 10 MeV photon energies; however, these values are way far away from ICRU tissue. Carbon dioxide gas shows the closest tissue equivalence in the entire photon energy spectrum. Relative tissue equivalences of the mixtures of gases with respect to ICRU tissue are in the range of 0.998-1.041 for air, argon (4.5% + methane (95.5%, argon (0.5% + carbon dioxide (99.5%, and nitrogen (5% + methane (7% + carbon dioxide (88%. The gas composition of xenon (0.5% + carbon dioxide (99.5% shows 1.605 times higher tissue equivalence compared to the ICRU tissue. The investigated photon interaction parameters are useful for exposure and energy absorption buildup factors calculation and design, and fabrication of gaseous detectors for ambient radiation measurement by the Geiger-Muller detector, ionization chambers and proportional counters.

QED effects on individual atomic orbital energies

Science.gov (United States)

Kozioł, Karol; Aucar, Gustavo A.

2018-04-01

Several issues, concerning QED corrections, that are important in precise atomic calculations are presented. The leading QED corrections, self-energy and vacuum polarization, to the orbital energy for selected atoms with 30 ≤ Z ≤ 118 have been calculated. The sum of QED and Breit contributions to the orbital energy is analyzed. It has been found that for ns subshells the Breit and QED contributions are of comparative size, but for np and nd subshells the Breit contribution takes a major part of the QED+Breit sum. It has also, been found that the Breit to leading QED contributions ratio for ns subshells is almost independent of Z. The Z-dependence of QED and Breit+QED contributions per subshell is shown. The fitting coefficients may be used to estimate QED effects on inner molecular orbitals. We present results of our calculations for QED contributions to orbital energy of valence ns-subshell for group 1 and 11 atoms and discuss about the reliability of these numbers by comparing them with experimental first ionization potential data.

Reconstruction of atomic effective potentials from isotropic scattering factors

International Nuclear Information System (INIS)

Romera, E.; Angulo, J.C.; Torres, J.J.

2002-01-01

We present a method for the approximate determination of one-electron effective potentials of many-electron systems from a finite number of values of the isotropic scattering factor. The method is based on the minimum cross-entropy technique. An application to some neutral ground-state atomic systems has been done within a Hartree-Fock framework

Tomography of atomic number and density of materials using dual-energy imaging and the Alvarez and Macovski attenuation model

Energy Technology Data Exchange (ETDEWEB)

Paziresh, M.; Kingston, A. M., E-mail: andrew.kingston@anu.edu.au; Latham, S. J.; Fullagar, W. K.; Myers, G. M. [Department of Applied Mathematics, Research School of physics and Engineering, The Australian National University, Canberra 2601 (Australia)

2016-06-07

Dual-energy computed tomography and the Alvarez and Macovski [Phys. Med. Biol. 21, 733 (1976)] transmitted intensity (AMTI) model were used in this study to estimate the maps of density (ρ) and atomic number (Z) of mineralogical samples. In this method, the attenuation coefficients are represented [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)] in the form of the two most important interactions of X-rays with atoms that is, photoelectric absorption (PE) and Compton scattering (CS). This enables material discrimination as PE and CS are, respectively, dependent on the atomic number (Z) and density (ρ) of materials [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976)]. Dual-energy imaging is able to identify sample materials even if the materials have similar attenuation coefficients at single-energy spectrum. We use the full model rather than applying one of several applied simplified forms [Alvarez and Macovski, Phys. Med. Biol. 21, 733 (1976); Siddiqui et al., SPE Annual Technical Conference and Exhibition (Society of Petroleum Engineers, 2004); Derzhi, U.S. patent application 13/527,660 (2012); Heismann et al., J. Appl. Phys. 94, 2073–2079 (2003); Park and Kim, J. Korean Phys. Soc. 59, 2709 (2011); Abudurexiti et al., Radiol. Phys. Technol. 3, 127–135 (2010); and Kaewkhao et al., J. Quant. Spectrosc. Radiat. Transfer 109, 1260–1265 (2008)]. This paper describes the tomographic reconstruction of ρ and Z maps of mineralogical samples using the AMTI model. The full model requires precise knowledge of the X-ray energy spectra and calibration of PE and CS constants and exponents of atomic number and energy that were estimated based on fits to simulations and calibration measurements. The estimated ρ and Z images of the samples used in this paper yield average relative errors of 2.62% and 1.19% and maximum relative errors of 2.64% and 7.85%, respectively. Furthermore, we demonstrate that the method accounts for the beam hardening effect in density (�

Atomic effect algebras with compression bases

International Nuclear Information System (INIS)

Caragheorgheopol, Dan; Tkadlec, Josef

2011-01-01

Compression base effect algebras were recently introduced by Gudder [Demonstr. Math. 39, 43 (2006)]. They generalize sequential effect algebras [Rep. Math. Phys. 49, 87 (2002)] and compressible effect algebras [Rep. Math. Phys. 54, 93 (2004)]. The present paper focuses on atomic compression base effect algebras and the consequences of atoms being foci (so-called projections) of the compressions in the compression base. Part of our work generalizes results obtained in atomic sequential effect algebras by Tkadlec [Int. J. Theor. Phys. 47, 185 (2008)]. The notion of projection-atomicity is introduced and studied, and several conditions that force a compression base effect algebra or the set of its projections to be Boolean are found. Finally, we apply some of these results to sequential effect algebras and strengthen a previously established result concerning a sufficient condition for them to be Boolean.

Collective effects in isolated atoms (many-body aspects of photoionization process)

International Nuclear Information System (INIS)

Amusia, M.Y.

1983-01-01

This chapter examines outer and intermediate many-electron shells and demonstrates that photoionization is of collective nature because in the atomic reaction to the external electromagnetic field at least all electrons of the ionized subshell take part. Performs the calculation of complex atom photoionization using random phase approximation with exchange (RPAE). Explains that in RPAE the ionization amplitude is presented as a sum of two terms, describing the direct knock-out and the induced one which is connected with a variation of the self-consistent field, caused by polarization of atomic shells under the action of the external field. Discusses collective effects in outer shells; deviation from RPAE prediction in outer shells; excitations ''two electrons-two holes'' and autoionizing states; collective effects in inner shells; and bremsstrahlung. Observes a large number of many-particle effects which manifest themselves practically in all atomic processes. Finds that by correcting and improving the one-electron approximation it becomes possible even in its frame to include much of what seems to be many-electron corrections

A practical relation between atomic numbers and alpha coefficients

International Nuclear Information System (INIS)

Lachance, G.R.

1980-01-01

A first approximation indicates that fundamental alpha coefficients for a given analyte vary as a function of the ratio of their respective atomic number raised to a power. This simple rule applies mainly at the limits (i.e., when the weight fraction of analyte i, Wsub(i) is of the order of 0.0 or 1.0) in cases of absorption and weak enhancement. The relation thus provides a means of generating coefficients for the system i-k from experimental data obtained on system i-j and a means of verifying experimental alphas, since arrays of coefficients must show a high degree of concordance. (author)

Internal conversion coefficients for atomic numbers Z less than or equal to 30

International Nuclear Information System (INIS)

Band, I.M.; Trzhaskovskaya, M.B.; Listengarten, M.A.

1976-01-01

Presented here are internal conversion coefficients (ICC) of gamma rays for 20 values of atomic number, Z, in the range 3 less than or equal to Z less than or equal to 30, including all Z greater than or equal to 14. The tables provide the previously missing data for light elements. Coefficients are given for 19 values of gamma-ray transition energies up to 6 MeV for the K-electron shell and 18 values up to 2 MeV for three L-subshells. The minimum enegy is 15 keV. The first five electric and magnetic nuclear transition multipolarities are covered. The calculations are relativistic, with screening and finite nuclear size effect taken into account

Hadronic atoms and ticklish nuclei: the E2 nuclear resonance effect

International Nuclear Information System (INIS)

Leon, M.

1975-06-01

The E2 nuclear resonance effect in hadronic atoms offers a way to increase the hadronic information that can be obtained from hadronic x-ray experiments. The effect occurs when an atomic deexcitation energy closely matches a nuclear excitation energy, so that some configuration mixing occurs. It shows up as an attenuation of some of the hadronic x-ray lines from a resonant versus a normal isotope target. The effect was observed very clearly in pionic cadmium in a recent LAMPF experiment. A planned LAMPF experiment will use the nuclear resonance effect to determine whether the p-wave π-nucleus interaction does indeed become repulsive for Z greater than or equal to 35 as predicted. The effect also appears in the kaonic molybdenum data taken at LBL because several of the stable molybdenum isotopes are resonant. A number of promising cases for π - , K - , anti p, and Σ - atoms are discussed and a spectacular and potentially very informative experiment on anti p- 100 Mo is proposed. (9 figures, 9 tables) (U.S.)

Effect of the nuclear charge of a fast structural ion on its internal effective stopping in collisions with atoms

Energy Technology Data Exchange (ETDEWEB)

Gusarevich, E. S., E-mail: gusarevich@gmail.com [Lomonosov Nothern (Arctic) Federal University (Russian Federation)

2017-02-15

The energy losses of fast structural ions in collisions with atoms have been considered in the eikonal approximation. The structural ions are ions consisting of a nucleus and a certain number of electrons bound to it. The effect of nuclear charge Z of the ion on its effective deceleration κ{sup (p)} (energy losses associated with excitation of only intrinsic ion shells) has been analyzed. It is shown that the allowance for the interaction of an atom with the ion nucleus for Z{sub a}Z/v > 1, where Z{sub a} is the charge of the atomic nucleus and v is the velocity of collisions in atomic units, considerably affects the value of κ{sup (p)}, which generally necessitates taking into account nonperturbatively the effect of both charges Z{sub a} and Z on κ{sup (p)}.

Methodology for attainment of density and effective atomic number through dual energy technique using microtomographic images

International Nuclear Information System (INIS)

Alves, H.; Lima, I.; Lopes, R.T.

2014-01-01

Dual energy technique for computerized microtomography shows itself as a promising method for identification of mineralogy on geological samples of heterogeneous composition. It can also assist with differentiating very similar objects regarding the attenuation coefficient, which are usually not separable during image processing and analysis of microtomographic data. Therefore, the development of a feasible and applicable methodology of dual energy in the analysis of microtomographic images was sought. - Highlights: • Dual energy technique is promising for identification of distribution of minerals. • A feasible methodology of dual energy in analysis of tomographic images was sought. • The dual energy technique is efficient for density and atomic number identification. • Simulation showed that the proposed methodology agrees with theoretical data. • Nondestructive characterization of distribution of density and chemical composition

Does the number of nitrogen atoms have an influence on the conducting properties of diphenylazines? A DFT insight

International Nuclear Information System (INIS)

Moral, Monica; Granadino-Roldan, Jose Manuel; Garzon, Andres; Garcia, Gregorio; Fernandez-Gomez, Manuel

2011-01-01

Research highlights: → Planarity and aromaticity increase when increasing the number of N atoms. → HOMO → LUMO excitation energy decreases when increasing the number of N atoms. → AEA increases stepwise with the number of N atoms up to 1.51 eV for Ph 2 Tz. → Ph 2 Tz becomes the best candidate of the series in terms of electron injection. → Ph 2 T N3 seems to be the best candidate in terms of electron transport. - Abstract: The present study reports on the variation of some structural and electronic properties related to the electron conductivity for the series of diphenylazines represented by the formula Ph-(C 2+n N 4-n H n )-Ph, n = 0 - 4. Properties such as planarity, aromaticity, HOMO → LUMO excitation energy, electron affinity, LUMO level energy, reorganization energy and electron coupling between neighboring molecules in the crystal were analyzed from a theoretical perspective as a function of the number of nitrogen atoms in the molecular structure. As a result, the planarity, aromaticity and electron affinity increase with the number of N atoms in the central ring while the HOMO → LUMO excitation energy and LUMO levels diminish. It is worth noting that up to n = 3, the frontier orbitals appear delocalized throughout the whole system while for n = 4 the localized character of the LUMO might explain the increase in the reorganization energy and thus the higher difficulty to delocalize the excess of negative charge. Electron coupling between neighboring molecules was also estimated on the basis of the energy splitting in dimer method and the reported crystal structures for some of the studied molecules. Accordingly, the highest |t 12 | value was obtained for Ph 2 T N3 (0.06 eV) while Ph 2 Tz should be the most advantageous candidate of the series in terms of electron injection.

Atomic-scale friction : thermal effects and capillary condensation

NARCIS (Netherlands)

Jinesh, Kochupurackal Balakrishna Pillai

2006-01-01

This work entitled as "Atomic-scale friction: thermal effects and capillary condensation" is a study on the fundamental aspects of the origin of friction from the atomic-scale. We study two realistic aspects of atomic-scale friction, namely the effect of temperature and the effect of relative

Atomic squeezed states on an atom-chip

International Nuclear Information System (INIS)

Maussang, Kenneth

2010-01-01

In this thesis, we describe the construction of an experiment, allowing to produce 87 Rb Bose-Einstein condensates on an atom chip, and then split them in a double well potential. An accurate imaging system has been developed, in order to be able to measure the absolute value of the populations of the double well within a very low noise level, almost limited by the optical shot noise. We measure atom number statistics after splitting, and directly observe number squeezed states, down to -4.9 dB at low temperatures, compared to a classical gas, of independent particles. The dependence in temperature of fluctuations has been also studied. For a thermal gas, Poissonian fluctuations are given by the probability distribution of the macroscopic configurations with a given atom number difference. In the degenerate regime, the entropy effect which favors small number differences vanishes, leading to super-Poissonian fluctuations, to more than +3.8 dB close to transition temperature. At low temperatures, the interaction energy cost associated with number fluctuations exceeds the available thermal energy, leading to sub-Poissonian fluctuations. Those two behaviours have been theoretically explained, both with a simple analytical model and a numerical one. We also measured the evolution of the relative phase between the two clouds, and its collapse due to interactions, allowing us to claim that this splitter is a coherent one. (author)

Atomic effects in tritium beta-decay. II. Muon to electron conversion in atoms

International Nuclear Information System (INIS)

Wampler, K.D.

1989-01-01

I. The final-state, atomic effects in the low energy end of the tritium beta decay spectrum are studied in detail. The author treats the instantaneous, two-electron repulsion in the final state, effectively to all orders in perturbation theory, by solving the eigenvalue problem with a discretized and truncated form of the Hamiltonian. He finds that these effects fail to explain the distortion in the spectrum observed by Simpson (Phys. Rev. Lett. 54, 649 (1985)). Simpson attributed this distortion to the admixture of a heavy mass antineutrino in the outgoing electron antineutrino state. In fact, the final-state Coulomb effects enhance the distortion. This calculation clears up some of the ambiguities of other theoretical analyses based on considerations of screening functions and perturbation theory. II. He presents a phenomenological study of separate lepton number violating muon to electron conversion in atoms. Previous work on this process has concentrated on elastic transitions where the nucleus characteristics have the gate on the substrate and the source-drain contacts on the top of the sample. The first use as an FET dielectric is reported of hydrogenated amorphous silicon-carbon (prepared from silane and propane mixture), photo-oxidised by UV lamp or laser. These FETs have similar characteristics to those with silicon nitride gate insulator but without the difficulties of preparing good insulator/semiconductor interfaces. Using the same materials attempts have been made to produce charge coupled devices

Cold Incineration of Chlorophenols in Aqueous Solution by Advanced Electrochemical Process Electro-Fenton. Effect of Number and Position of Chlorine Atoms on the Degradation Kinetics

Science.gov (United States)

Oturan, Nihal; Panizza, Marco; Oturan, Mehmet A.

2009-09-01

This study reports the kinetics of the degradation of several chlorophenols (CPs), such as monochlorophenols (2-chlorophenol and 4-chlorophenol), dichlorophenols (2,4-dichlorophenol and 2,6- dichlorophenol), trichlorophenols (2,3,5- trichlorophenol and 2,4,5-trichlorophenol), 2,3,5,6-tetrachlorophenol, and pentachlorophenol, by the electro-Fenton process using a carbon felt cathode and a Pt anode. The effect of number and the position of the chlorine atoms in the aromatic ring on the oxidative degradation rate was evaluated and discussed. The oxidation reaction of all the CPs with hydroxyl radicals evidenced a pseudo-first-order kinetics and the rate constant decreased with increasing the number of chlorine atoms. The absolute rate constant of second-order reaction kinetics between CPs and •OH was determined by the competition kinetics method in the range of (3.56-7.75) × 109 M-1 s-1 and follows the same sequence of the apparent rate constants. The mineralization of several CPs and of a mixture of all CPs under study was monitored by the total organic carbon (TOC) removal and the chlorine release during mineralization was followed by ion chromatography. Our results demonstrated that more chlorinated phenols are more difficult to mineralize; however for all the tested CPs, almost quantitative release of chloride ions was obtained after 6 h of treatment.

Two-Dimensional SnO Anodes with a Tunable Number of Atomic Layers for Sodium Ion Batteries

KAUST Repository

Zhang, Fan

2017-01-18

We have systematically changed the number of atomic layers stacked in 2D SnO nanosheet anodes and studied their sodium ion battery (SIB) performance. The results indicate that as the number of atomic SnO layers in a sheet decreases, both the capacity and cycling stability of the Na ion battery improve. The thinnest SnO nanosheet anodes (two to six SnO monolayers) exhibited the best performance. Specifically, an initial discharge and charge capacity of 1072 and 848 mAh g-1 were observed, respectively, at 0.1 A g-1. In addition, an impressive reversible capacity of 665 mAh g-1 after 100 cycles at 0.1 A g-1 and 452 mAh g-1 after 1000 cycles at a high current density of 1.0 A g-1 was observed, with excellent rate performance. As the average number of atomic layers in the anode sheets increased, the battery performance degraded significantly. For example, for the anode sheets with 10-20 atomic layers, only a reversible capacity of 389 mAh g-1 could be obtained after 100 cycles at 0.1 A g-1. Density functional theory calculations coupled with experimental results were used to elucidate the sodiation mechanism of the SnO nanosheets. This systematic study of monolayer-dependent physical and electrochemical properties of 2D anodes shows a promising pathway to engineering and mitigating volume changes in 2D anode materials for sodium ion batteries. It also demonstrates that ultrathin SnO nanosheets are promising SIB anode materials with high specific capacity, stable cyclability, and excellent rate performance.

Mass attenuation coefficient (μ/ρ), effective atomic number (Zeff) and measurement of x-ray energy spectra using based calcium phosphate biomaterials: a comparative study

International Nuclear Information System (INIS)

Fernandes Z, M. A.; Da Silva, T. A.; Nogueira, M. S.; Goncalves Z, E.

2015-10-01

In dentistry, alveolar bone regeneration procedures using based calcium phosphate biomaterials have been shown effective. However,there are not reports in the literature of studies the interaction of low energy radiation in these biomaterials used as attenuator and not being then allowed a comparison between the theoretical values and experimental.The objective of this study was to determine the interaction of radiation parameters of four dental biomaterials - BioOss, Cerasorb M Dental, Straumann Boneceramic and Osteogen for diagnostic radiology qualities. As a material and methods, the composition of the biomaterials was determined by the analytical techniques. The samples with 0.181 cm to 0,297 cm thickness were experimentally used as attenuators for the measurement of the transmitted X-rays spectra in X-ray equipment with 50 to 90 kV range by spectrometric system comprising the Cd Te detector. After this procedure, the mass attenuation coefficient, the effective atomic number were determined and compared between all the specimens analyzed, using the program WinXCOM in the range of 10 to 200 keV. In all strains examined observed that the energy spectrum of x-rays transmitted through the BioOss has the mean energy slightly smaller than the others biomaterials for close thickness. The μ/ρ and Z eff of the biomaterials showed its dependence on photon energy and atomic number of the elements of the material analyzed. It is concluded according to the methodology employed in this study that the measurements of x-ray spectrum, μ/ρ and Z eff using biomaterials as attenuators confirmed that the thickness, density, composition of the samples, the incident photon energy are factors that determine the characteristics of radiation in a tissue or equivalent material. (Author)

Electronic structure of atoms: atomic spectroscopy information system

International Nuclear Information System (INIS)

Kazakov, V V; Kazakov, V G; Kovalev, V S; Meshkov, O I; Yatsenko, A S

2017-01-01

The article presents a Russian atomic spectroscopy, information system electronic structure of atoms (IS ESA) (http://grotrian.nsu.ru), and describes its main features and options to support research and training. The database contains over 234 000 records, great attention paid to experimental data and uniform filling of the database for all atomic numbers Z, including classified levels and transitions of rare earth and transuranic elements and their ions. Original means of visualization of scientific data in the form of spectrograms and Grotrian diagrams have been proposed. Presentation of spectral data in the form of interactive color charts facilitates understanding and analysis of properties of atomic systems. The use of the spectral data of the IS ESA together with its functionality is effective for solving various scientific problems and training of specialists. (paper)

Electronic structure of atoms: atomic spectroscopy information system

Science.gov (United States)

Kazakov, V. V.; Kazakov, V. G.; Kovalev, V. S.; Meshkov, O. I.; Yatsenko, A. S.

2017-10-01

The article presents a Russian atomic spectroscopy, information system electronic structure of atoms (IS ESA) (http://grotrian.nsu.ru), and describes its main features and options to support research and training. The database contains over 234 000 records, great attention paid to experimental data and uniform filling of the database for all atomic numbers Z, including classified levels and transitions of rare earth and transuranic elements and their ions. Original means of visualization of scientific data in the form of spectrograms and Grotrian diagrams have been proposed. Presentation of spectral data in the form of interactive color charts facilitates understanding and analysis of properties of atomic systems. The use of the spectral data of the IS ESA together with its functionality is effective for solving various scientific problems and training of specialists.

Enhancement of phase space density by increasing trap anisotropy in a magneto-optical trap with a large number of atoms

International Nuclear Information System (INIS)

Vengalattore, M.; Conroy, R.S.; Prentiss, M.G.

2004-01-01

The phase space density of dense, cylindrical clouds of atoms in a 2D magneto-optic trap is investigated. For a large number of trapped atoms (>10 8 ), the density of a spherical cloud is limited by photon reabsorption. However, as the atom cloud is deformed to reduce the radial optical density, the temperature of the atoms decreases due to the suppression of multiple scattering leading to an increase in the phase space density. A density of 2x10 -4 has been achieved in a magneto-optic trap containing 2x10 8 atoms

The influence of atomic number on the complex formation constants by visible spectrophotometric method

International Nuclear Information System (INIS)

Samin; Kris-Tri-Basuki; Farida-Ernawati

1996-01-01

The influence of atomic number on the complex formation constants and it's application by visible spectrophotometric method has been carried out. The complex compound have been made of Y, Nd, Sm and Gd with alizarin red sulfonic in the mole fraction range of 0.20 - 0.53 and pH range of 3.5 - 5. The optimum condition of complex formation was found in the mole fraction range of 0.30 - 0.53, range of pH 3.75 - 5, and the total concentration was 0.00030 M. It was found that the formation constant (β) of alizarin red S. complex by continued variation and matrix disintegration techniques were β : (7.00 ± 0.64).10 9 of complex 3 9γ,β : (4.09±0.34).10 8 of 6 0Nd, β : (7.26 ± 0.42).10 8 of 62 S m and β : (8.38 ± 0.70).10 8 of 64 G d. It can be concluded that the atomic number of Nd is bigger than Sm which is bigger than Gd. The atomic number of Y is the smallest. (39) and the complex formation constant is a biggest. The complex compound can be used for sample analysis with limit detection of Y : 2.2 .10 -5 M, Nd : 2.9 .10 -5 M, Sm : 2.6 .10 -5 M and Gd : 2.4 .10 -5 M. The sensitivity of analysis are Y>Gd>Sm>Nd. The Y 2 O 3 sample of product result from xenotime sand contains Y 2 O 3 : 98.96 ± 1.40 % and in the filtrate (product of monazite sand) contains Nd : 0.27 ± 0.002 M

Teleportation of two-atom entangled state in resonant cavity quantum electrodynamics

Institute of Scientific and Technical Information of China (English)

Yang Zhen-Biao

2007-01-01

An alternative scheme is presented for teleportation of a two-atom entangled state in cavity quantum electrodynamics (QED). It is based on the resonant atom-cavity field interaction. In the scheme, only one cavity is involved, and the number of the atoms needed to be detected is decreased compared with the previous scheme. Since the resonant atom-cavity field interaction greatly reduces the interaction time, the decoherence effect can be effectively suppressed during the teleportation process. The experimental feasibility of the scheme is discussed. The scheme can easily be generalized to the teleportation of N-atom Greeninger-Horne-Zeilinger (GHZ) entangled states. The number of atoms needed to be detected does not increase as the number of the atoms in the GHZ state increases.

Experimental research on the contrast production of the chemical elements with the atomic numbers 1-83 in a computer-totalbody-tomogram

International Nuclear Information System (INIS)

Kirschner, H.; Burmester, U.; Stringaris, K.

1979-01-01

The contrast production for the chemical elements with the atomic numbers Z=1-83 were determined by computer-tomography. With the formula relation of the Δ-number and the atomic number can one compute the contrast production of any chosen chemical compound. Iodine-free and inorganic iodine-containing contrast media are examined for their contrast production and compared with presently used organic iodine-containing contrast media. The contrast enhancement of organic contrast media in tissue are discussed. (orig.) [de

SU-C-BRC-05: Monte Carlo Calculations to Establish a Simple Relation of Backscatter Dose Enhancement Around High-Z Dental Alloy to Its Atomic Number

Energy Technology Data Exchange (ETDEWEB)

Utsunomiya, S; Kushima, N; Katsura, K; Tanabe, S; Hayakawa, T; Sakai, H; Yamada, T; Takahashi, H; Abe, E; Wada, S; Aoyama, H [Niigata University, Niigata (Japan)

2016-06-15

Purpose: To establish a simple relation of backscatter dose enhancement around a high-Z dental alloy in head and neck radiation therapy to its average atomic number based on Monte Carlo calculations. Methods: The PHITS Monte Carlo code was used to calculate dose enhancement, which is quantified by the backscatter dose factor (BSDF). The accuracy of the beam modeling with PHITS was verified by comparing with basic measured data namely PDDs and dose profiles. In the simulation, a high-Z alloy of 1 cm cube was embedded into a tough water phantom irradiated by a 6-MV (nominal) X-ray beam of 10 cm × 10 cm field size of Novalis TX (Brainlab). The ten different materials of high-Z alloys (Al, Ti, Cu, Ag, Au-Pd-Ag, I, Ba, W, Au, Pb) were considered. The accuracy of calculated BSDF was verified by comparing with measured data by Gafchromic EBT3 films placed at from 0 to 10 mm away from a high-Z alloy (Au-Pd-Ag). We derived an approximate equation to determine the relation of BSDF and range of backscatter to average atomic number of high-Z alloy. Results: The calculated BSDF showed excellent agreement with measured one by Gafchromic EBT3 films at from 0 to 10 mm away from the high-Z alloy. We found the simple linear relation of BSDF and range of backscatter to average atomic number of dental alloys. The latter relation was proven by the fact that energy spectrum of backscatter electrons strongly depend on average atomic number. Conclusion: We found a simple relation of backscatter dose enhancement around high-Z alloys to its average atomic number based on Monte Carlo calculations. This work provides a simple and useful method to estimate backscatter dose enhancement from dental alloys and corresponding optimal thickness of dental spacer to prevent mucositis effectively.

Determination of the number density of excited and ground Zn atoms during rf magnetron sputtering of ZnO target

Energy Technology Data Exchange (ETDEWEB)

Maaloul, L.; Gangwar, R. K.; Stafford, L., E-mail: luc.stafford@umontreal.ca [Département de Physique, Université de Montréal, Montréal, Québec H3C 3J7 (Canada)

2015-07-15

A combination of optical absorption spectroscopy (OAS) and optical emission spectroscopy measurements was used to monitor the number density of Zn atoms in excited 4s4p ({sup 3}P{sub 2} and {sup 3}P{sub 0}) metastable states as well as in ground 4s{sup 2} ({sup 1}S{sub 0}) state in a 5 mTorr Ar radio-frequency (RF) magnetron sputtering plasma used for the deposition of ZnO-based thin films. OAS measurements revealed an increase by about one order of magnitude of Zn {sup 3}P{sub 2} and {sup 3}P{sub 0} metastable atoms by varying the self-bias voltage on the ZnO target from −115 to −300 V. Over the whole range of experimental conditions investigated, the triplet-to-singlet metastable density ratio was 5 ± 1, which matches the statistical weight ratio of these states in Boltzmann equilibrium. Construction of a Boltzmann plot using all Zn I emission lines in the 200–500 nm revealed a constant excitation temperature of 0.33 ± 0.04 eV. In combination with measured populations of Zn {sup 3}P{sub 2} and {sup 3}P{sub 0} metastable atoms, this temperature was used to extrapolate the absolute number density of ground state Zn atoms. The results were found to be in excellent agreement with those obtained previously by actinometry on Zn atoms using Ar as the actinometer gas [L. Maaloul and L. Stafford, J. Vac. Sci. Technol., A 31, 061306 (2013)]. This set of data was then correlated to spectroscopic ellipsometry measurements of the deposition rate of Zn atoms on a Si substrate positioned at 12 cm away from the ZnO target. The deposition rate scaled linearly with the number density of Zn atoms. In sharp contrast with previous studies on RF magnetron sputtering of Cu targets, these findings indicate that metastable atoms play a negligible role on the plasma deposition dynamics of Zn-based coatings.

Spectral effects on some physical coefficients of x-Ray interaction with materials of low atomic number

International Nuclear Information System (INIS)

EL-Kazzaz, S.A.; Youssef, M.; EL-Hadad, S.; and EL-Nadi, L.M.

1988-01-01

X-ray spectra were measured before and after passing through some materials of medical importance applying X-ray diffraction. The mass absorption coefficients of these materials were determined at X-ray peak voltages 27, 30 and 42 kV-p making use the measured spectrum and also by using the direct beam absorption. It has been found that the mass absorption coefficients calculated from the X-ray spectral distribution analysis are in general lower than those obtained considering the direct beam method. From the study of the atomic number and energy dependence of the mass absorption coefficients it has been found that the dependence of the coefficients calculated from the spectral distribution is good agreement with the previously studied data for monoenergetic x-ray beam. Also the roentgen - to - Rad conversion factors were determined at the different used energies and materials. The value of the mass absorption coefficients calculated from the spectral distribution is recommended for use in dose calculation

Cheminoes: A Didactic Game to Learn Chemical Relationships between Valence, Atomic Number, and Symbol

Science.gov (United States)

Moreno, Luis F.; Hincapié, Gina; Alzate, María Victoria

2014-01-01

Cheminoes is a didactic game that enables the meaningful learning of some relations between concepts such as chemical element, valence, atomic number, and chemical symbol for the first 36 chemical elements of the periodic system. Among the students who have played the game, their opinions of the activity were positive, considering the game to be a…

Cold experiment of slag centrifugal granulation by rotary atomizer: Effect of atomizer configuration

International Nuclear Information System (INIS)

Wu, Jun-Jun; Wang, Hong; Zhu, Xun; Liao, Qiang; Li, Kai

2017-01-01

Centrifugal granulation has recently been employed to produce small blast furnace slag particles, so as to recover the waste heat from the high-temperature molten blast furnace slag. An appropriate atomizer enables centrifugal granulation to become a better cost-effective process for particle production. Thus, increasing emphasis has been placed on influence of atomizer configuration on granulation. In present study, three groups of atomizers were specially designed and the granulation performance of each atomizer was experimentally tested during cold experiments. The influences of atomizer configuration on granulation modes and droplet characteristics were investigated visually. Two modified correlations were proposed to predict the granulating droplet size by means of data fitting. The results indicated that the rotary cup atomizers can inhibit the film formation in contrast to rotary disc atomizer. Moreover, atomizers with outer angle of 90° was capable of producing smaller droplets. The revised correlation as well as the newly-developed correlation including the influence of atomizer configurations, presented in good agreement with the experiment data. In addition, an analysis on atomizer design was conducted to provide a good insight for industrialization. It was recommended to adopt cup-like atomizer in granulation for its ability to produce fine particles with smaller atomizer size.

Resonance effects in projectile-electron loss in relativistic collisions with excited atoms

International Nuclear Information System (INIS)

Voitkiv, A B

2005-01-01

The theory of electron loss from projectile-ions in relativistic ion-atom collisions is extended to the case of collisions with excited atoms. The main feature of such collisions is a resonance which can emerge between electron transitions in the ion and atom. The resonance becomes possible due to the Doppler effect and has a well-defined impact energy threshold. In the resonance case, the ion-atom interaction is transmitted by the radiation field and the range of this interaction becomes extremely long. Because of this the presence of other atoms in the target medium and the size of the space occupied by the medium have to be taken into account and it turns out that microscopic loss cross sections may be strongly dependent on such macroscopic parameters as the target density, temperature and size. We consider both the total and differential loss cross sections and show that the resonance can have a strong impact on the angular and energy distributions of electrons emitted from the projectiles and the total number of electron loss events

The UKB prescription and the heavy atom effects on the nuclear magnetic shielding of vicinal heavy atoms.

Science.gov (United States)

Maldonado, Alejandro F; Aucar, Gustavo A

2009-07-21

Fully relativistic calculations of NMR magnetic shielding on XYH3 (X = C, Si, Ge and Sn; Y = Br, I), XHn (n = 1-4) molecular systems and noble gases performed with a fully relativistic polarization propagator formalism at the RPA level of approach are presented. The rate of convergence (size of basis set and time involved) for calculations with both kinetic balance prescriptions, RKB and UKB, were investigated. Calculations with UKB makes it feasible to obtain reliable results for two or more heavy-atom-containing molecules. For such XYH3 systems, the influence of heavy vicinal halogen atoms on sigma(X) is such that heavy atom effects on heavy atoms (vicinal plus their own effects or HAVHA + HAHA effects) amount to 30.50% for X = Sn and Y = I; being the HAHA effect of the order of 25%. So the vicinal effect alone is of the order of 5.5%. The vicinal heavy atom effect on light atoms (HALA effect) is of the order of 28% for X = C and Y = I. A similar behaviour, but of opposite sign, is observed for sigma(Y) for which sigmaR-NR (I; X = C) (HAHA effect) is around 27% and sigmaR-NR(I; X = Sn) (HAVHA + HAHA effects) is close to 21%. Its electronic origin is paramagnetic for halogen atoms but both dia- and paramagnetic for central atoms. The effect on two bond distant hydrogen atoms is such that the largest variation of sigma(H) within the same family of XYH3 molecules appears for X = Si and Y = I: around 20%. In this case sigma(H; X = Sn, Y = I) = 33.45 ppm and sigma(H; X = Sn, Y = H) = 27.82 ppm.

Energy dependence of effective atomic numbers for photon energy absorption and photon interaction: Studies of some biological molecules in the energy range 1 keV-20 MeV

DEFF Research Database (Denmark)

Manohara, S.R.; Hanagodimath, S.M.; Gerward, Leif

2008-01-01

Effective atomic numbers for photon energy absorption, Z(PEA,eff), and for photon interaction, Z(PI,eff), have been calculated by a direct method in the photon-energy region from 1 keV to 20 MeV for biological molecules, such as fatty acids (lauric, myristic, palmitic, stearic, oleic, linoleic......, linolenic, arachidonic, and arachidic acids), nucleotide bases (adenine, guanine, cytosine, uracil, and thymine), and carbohydrates (glucose, sucrose, raffinose, and starch). The Z(PEA, eff) and Z(PI, eff) values have been found to change with energy and composition of the biological molecules. The energy...

Radiation shielding and effective atomic number studies in different types of shielding concretes, lead base and non-lead base glass systems for total electron interaction: A comparative study

International Nuclear Information System (INIS)

Kurudirek, Murat

2014-01-01

Highlights: • Radiation shielding calculations for concretes and glass systems. • Assigning effective atomic number for the given materials for total electron interaction. • Glass systems generally have better shielding ability than concretes. - Abstract: Concrete has been widely used as a radiation shielding material due to its extremely low cost. On the other hand, glass systems, which make everything inside visible to observers, are considered as promising shielding materials as well. In the present work, the effective atomic numbers, Z eff of some concretes and glass systems (industrial waste containing glass, Pb base glass and non-Pb base glass) have been calculated for total electron interaction in the energy region of 10 keV–1 GeV. Also, the continuous slowing down approximation (CSDA) ranges for the given materials have been calculated in the wide energy region to show the shielding effectiveness of the given materials. The glass systems are not only compared to different types of concretes but also compared to the lead base glass systems in terms of shielding. Moreover, the obtained results for total electron interaction have been compared to the results for total photon interaction wherever possible. In general, it has been observed that the glass systems have superior properties than most of the concretes over the high-energy region with respect to the electron interaction. Also, glass systems without lead show better electron stopping than lead base glasses at some energy regions as well. Along with the photon attenuation capability, it is seen that Fly Ash base glass systems have not only greater electron stopping capability but also have greater photon attenuation especially in high energy region when compared with standard shielding concretes

Radiation shielding and effective atomic number studies in different types of shielding concretes, lead base and non-lead base glass systems for total electron interaction: A comparative study

Energy Technology Data Exchange (ETDEWEB)

Kurudirek, Murat, E-mail: mkurudirek@gmail.com

2014-12-15

Highlights: • Radiation shielding calculations for concretes and glass systems. • Assigning effective atomic number for the given materials for total electron interaction. • Glass systems generally have better shielding ability than concretes. - Abstract: Concrete has been widely used as a radiation shielding material due to its extremely low cost. On the other hand, glass systems, which make everything inside visible to observers, are considered as promising shielding materials as well. In the present work, the effective atomic numbers, Z{sub eff} of some concretes and glass systems (industrial waste containing glass, Pb base glass and non-Pb base glass) have been calculated for total electron interaction in the energy region of 10 keV–1 GeV. Also, the continuous slowing down approximation (CSDA) ranges for the given materials have been calculated in the wide energy region to show the shielding effectiveness of the given materials. The glass systems are not only compared to different types of concretes but also compared to the lead base glass systems in terms of shielding. Moreover, the obtained results for total electron interaction have been compared to the results for total photon interaction wherever possible. In general, it has been observed that the glass systems have superior properties than most of the concretes over the high-energy region with respect to the electron interaction. Also, glass systems without lead show better electron stopping than lead base glasses at some energy regions as well. Along with the photon attenuation capability, it is seen that Fly Ash base glass systems have not only greater electron stopping capability but also have greater photon attenuation especially in high energy region when compared with standard shielding concretes.

Thermal effects on the stability of excited atoms in cavities

International Nuclear Information System (INIS)

Khanna, F. C.; Malbouisson, A. P. C.; Malbouisson, J. M. C.; Santana, A. E.

2010-01-01

An atom, coupled linearly to an environment, is considered in a harmonic approximation in thermal equilibrium inside a cavity. The environment is modeled by an infinite set of harmonic oscillators. We employ the notion of dressed states to investigate the time evolution of the atom initially in the first excited level. In a very large cavity (free space) for a long elapsed time, the atom decays and the value of its occupation number is the physically expected one at a given temperature. For a small cavity the excited atom never completely decays and the stability rate depends on temperature.

Effective oscillator strength distributions of spherically symmetric atoms for calculating polarizabilities and long-range atom–atom interactions

Energy Technology Data Exchange (ETDEWEB)

Jiang, Jun, E-mail: phyjiang@yeah.net [Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province, College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070 (China); School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Cheng, Yongjun, E-mail: cyj83mail@gmail.com [School of Engineering, Charles Darwin University, Darwin, Northern Territory, 0909 (Australia); Academy of Fundamental and Interdisciplinary Science, Harbin Institute of Technology, Harbin 150080 (China); Bromley, M.W.J., E-mail: brom@physics.uq.edu.au [School of Mathematics and Physics, The University of Queensland, Brisbane, Queensland 4075 (Australia)

2015-01-15

Effective oscillator strength distributions are systematically generated and tabulated for the alkali atoms, the alkaline-earth atoms, the alkaline-earth ions, the rare gases and some miscellaneous atoms. These effective distributions are used to compute the dipole, quadrupole and octupole static polarizabilities, and are then applied to the calculation of the dynamic polarizabilities at imaginary frequencies. These polarizabilities can be used to determine the long-range C{sub 6}, C{sub 8} and C{sub 10} atom–atom interactions for the dimers formed from any of these atoms and ions, and we present tables covering all of these combinations.

Effective oscillator strength distributions of spherically symmetric atoms for calculating polarizabilities and long-range atom–atom interactions

International Nuclear Information System (INIS)

Jiang, Jun; Mitroy, J.; Cheng, Yongjun; Bromley, M.W.J.

2015-01-01

Effective oscillator strength distributions are systematically generated and tabulated for the alkali atoms, the alkaline-earth atoms, the alkaline-earth ions, the rare gases and some miscellaneous atoms. These effective distributions are used to compute the dipole, quadrupole and octupole static polarizabilities, and are then applied to the calculation of the dynamic polarizabilities at imaginary frequencies. These polarizabilities can be used to determine the long-range C 6 , C 8 and C 10 atom–atom interactions for the dimers formed from any of these atoms and ions, and we present tables covering all of these combinations

Atomic diffusion in stars

CERN Document Server

Michaud, Georges; Richer, Jacques

2015-01-01

This book gives an overview of atomic diffusion, a fundamental physical process, as applied to all types of stars, from the main sequence to neutron stars. The superficial abundances of stars as well as their evolution can be significantly affected. The authors show where atomic diffusion plays an essential role and how it can be implemented in modelling.  In Part I, the authors describe the tools that are required to include atomic diffusion in models of stellar interiors and atmospheres. An important role is played by the gradient of partial radiative pressure, or radiative acceleration, which is usually neglected in stellar evolution. In Part II, the authors systematically review the contribution of atomic diffusion to each evolutionary step. The dominant effects of atomic diffusion are accompanied by more subtle effects on a large number of structural properties throughout evolution. One of the goals of this book is to provide the means for the astrophysicist or graduate student to evaluate the importanc...

Mass attenuation coefficient (μ/ρ), effective atomic number (Z{sub eff}) and measurement of x-ray energy spectra using based calcium phosphate biomaterials: a comparative study

Energy Technology Data Exchange (ETDEWEB)

Fernandes Z, M. A.; Da Silva, T. A.; Nogueira, M. S. [Centro de Desenvolvimento da Tecnologia Nuclear / CNEN, Pte. Antonio Carlos 6627, Belo Horizonte 31270-901, Minas Gerais (Brazil); Goncalves Z, E., E-mail: madelon@cdtn.br [Pontifice Catholic University of Minas Gerais, Av. Dom Jose Gaspar 500, Belo Horizonte 30535-901, Minas Gerais (Brazil)

2015-10-15

In dentistry, alveolar bone regeneration procedures using based calcium phosphate biomaterials have been shown effective. However,there are not reports in the literature of studies the interaction of low energy radiation in these biomaterials used as attenuator and not being then allowed a comparison between the theoretical values and experimental.The objective of this study was to determine the interaction of radiation parameters of four dental biomaterials - BioOss, Cerasorb M Dental, Straumann Boneceramic and Osteogen for diagnostic radiology qualities. As a material and methods, the composition of the biomaterials was determined by the analytical techniques. The samples with 0.181 cm to 0,297 cm thickness were experimentally used as attenuators for the measurement of the transmitted X-rays spectra in X-ray equipment with 50 to 90 kV range by spectrometric system comprising the Cd Te detector. After this procedure, the mass attenuation coefficient, the effective atomic number were determined and compared between all the specimens analyzed, using the program WinXCOM in the range of 10 to 200 keV. In all strains examined observed that the energy spectrum of x-rays transmitted through the BioOss has the mean energy slightly smaller than the others biomaterials for close thickness. The μ/ρ and Z{sub eff} of the biomaterials showed its dependence on photon energy and atomic number of the elements of the material analyzed. It is concluded according to the methodology employed in this study that the measurements of x-ray spectrum, μ/ρ and Z{sub eff} using biomaterials as attenuators confirmed that the thickness, density, composition of the samples, the incident photon energy are factors that determine the characteristics of radiation in a tissue or equivalent material. (Author)

Number-phase entropic squeezing and nonclassical properties of a three-level atom interacting with a two-mode field: intensity-dependent coupling, deformed Kerr medium, and detuning effects

Science.gov (United States)

Faghihi, Mohammad Javad; Tavassoly, Mohammad Kazem

2013-11-01

In this paper, we follow our presented model in J. Opt. Soc. Am. B {\\bf 30}, 1109--1117 (2013), in which the interaction between a $\\Lambda$-type three-level atom and a quantized two-mode radiation field in a cavity in the presence of nonlinearities is studied. After giving a brief review on the procedure of obtaining the state vector of the atom-field system, some further interesting and important physical features (which are of particular interest in the quantum optics field of research) of the whole system state, i.e., the number-phase entropic uncertainty relation (based on the two-mode Pegg-Barnett formalism) and some of the nonclassicality signs consist of sub-Poissonian statistics, Cauchy-Schwartz inequality and two kinds of squeezing phenomenon are investigated. During our presentation, the effects of intensity-dependent coupling, deformed Kerr medium and the detuning parameters on the depth and domain of each of the mentioned nonclassical criteria of the considered quantum system are studied, in detail. It is shown that each of the mentioned nonclassicality aspects can be obtained by appropriately choosing the related parameters.

A simple formulation for deriving effective atomic numbers via electron density calibration from dual-energy CT data in the human body.

Science.gov (United States)

Saito, Masatoshi; Sagara, Shota

2017-06-01

The main objective of this study is to propose a simple formulation (which we called DEEDZ) for deriving effective atomic numbers (Z eff ) via electron density (ρ e ) calibration from dual-energy (DE) CT data. We carried out numerical analysis of this DEEDZ method for a large variety of materials with known elemental compositions and mass densities using an available photon cross sections database. The new conversion approach was also applied to previously published experimental DECT data to validate its practical feasibility. We performed numerical analysis of the DEEDZ conversion method for tissue surrogates that have the same chemical compositions and mass densities as a commercial tissue-characterization phantom in order to determine the parameters necessary for the ρ e and Z eff calibrations in the DEEDZ conversion. These parameters were then applied to the human-body-equivalent tissues of ICRU Report 46 as objects of interest with unknown ρ e and Z eff . The attenuation coefficients of these materials were calculated using the XCOM photon cross sections database. We also applied the DEEDZ conversion to experimental DECT data available in the literature, which was measured for two commercial phantoms of different shapes and sizes using a dual-source CT scanner at 80 kV and 140 kV/Sn. The simulated Z eff 's were in excellent agreement with the reference values for almost all of the ICRU-46 human tissues over the Z eff range from 5.83 (gallstones-cholesterol) to 16.11 (bone mineral-hydroxyapatite). The relative deviations from the reference Z eff were within ± 0.3% for all materials, except for one outlier that presented a -3.1% deviation, namely, the thyroid. The reason for this discrepancy is that the thyroid contains a small amount of iodine, an element with a large atomic number (Z = 53). In the experimental case, we confirmed that the simple formulation with less fit parameters enable to calibrate Z eff as accurately as the existing calibration

Measuring air core characteristics of a pressure-swirl atomizer via a transparent acrylic nozzle at various Reynolds numbers

Energy Technology Data Exchange (ETDEWEB)

Lee, Eun J.; Oh, Sang Youp; Kim, Ho Y.; Yoon, Sam S. [Dept. of Mechanical, Korea University Anamdong, 5-Ga, Sungbukgu, 136-713 Seoul (Korea); James, Scott C. [Thermal/Fluid Science and Engineering, Sandia National Labs, PO Box 969, Livermore, CA 94551 (United States)

2010-11-15

Because of thermal fluid-property dependence, atomization stability (or flow regime) can change even at fixed operating conditions when subject to temperature change. Particularly at low temperatures, fuel's high viscosity can prevent a pressure-swirl (or simplex) atomizer from sustaining a centrifugal-driven air core within the fuel injector. During disruption of the air core inside an injector, spray characteristics outside the nozzle reflect a highly unstable, nonlinear mode where air core length, Sauter mean diameter (SMD), cone angle, and discharge coefficient variability. To better understand injector performance, these characteristics of the pressure-swirl atomizer were experimentally investigated and data were correlated to Reynolds numbers (Re). Using a transparent acrylic nozzle, the air core length, SMD, cone angle, and discharge coefficient are observed as a function of Re. The critical Reynolds numbers that distinguish the transition from unstable mode to transitional mode and eventually to a stable mode are reported. The working fluids are diesel and a kerosene-based fuel, referred to as bunker-A. (author)

Effective atomic numbers and electron densities of bacteriorhodopsin and its comprising amino acids in the energy range 1 keV–100 GeV

Energy Technology Data Exchange (ETDEWEB)

Ahmadi, Morteza; Lunscher, Nolan [Waterloo Institute for Nanotechnology and Department of Systems Design Engineering, University of Waterloo, 200 University Ave., W., Waterloo, Ontario, Canada N2L 3G1 (Canada); Yeow, John T.W., E-mail: jyeow@uwaterloo.ca [Waterloo Institute for Nanotechnology and Department of Systems Design Engineering, University of Waterloo, 200 University Ave., W., Waterloo, Ontario, Canada N2L 3G1 (Canada)

2013-04-01

Recently, there has been an interest in fabrication of X-ray sensors based on bacteriorhodopsin, a proton pump protein in cell membrane of Halobacterium salinarium. Therefore, a better understanding of interaction of X-ray photons with bacteriorhodopsin is required. We use WinXCom program to calculate the mass attenuation coefficient of bacteriorhodopsin and its comprising amino acids for photon energies from 1 keV to 100 GeV. These amino acids include alanine, arginine, asparagine, aspartic acid, glutamine, glutamic acid, glycine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, Asx1, Asx2, Glx1 and Glx2. We then use that data to calculate effective atomic number and electron densities for the same range of energy. We also emphasize on two ranges of energies (10–200 keV and 1–20 MeV) in which X-ray imaging and radiotherapy machines work.

Quantum atom-heteronuclear molecule dark state: Role of population imbalance

International Nuclear Information System (INIS)

Jing Hui; Cui Shuai

2010-01-01

Recently, the finite-number effect of initial atoms in coherent atom-molecule conversion was investigated by Zhao et al. [Phys. Rev. Lett. 101, 010401 (2008)]. Here, by extending to the atom-heteronuclear molecule dark state, we find that the initial populations imbalance of the atoms plays a significant role in quantum conversion rate and adiabatic fidelity. In particular, even for the finite total number of imbalanced two-species atoms, the mean-field conversion rate, contrary to the general belief, still can be remarkably close to the exact quantum results.

Effect of solute atoms on swelling in Ni alloys and pure Ni under He + ion irradiation

Science.gov (United States)

Wakai, E.; Ezawa, T.; Imamura, J.; Takenaka, T.; Tanabe, T.; Oshima, R.

2002-12-01

The effects of solute atoms on microstructural evolutions have been investigated using Ni alloys under 25 keV He + irradiation at 500 °C. The specimens used were pure Ni, Ni-Si, Ni-Co, Ni-Cu, Ni-Mn and Ni-Pd alloys with different volume size factors. The high number densities of dislocation loops about 1.5×10 22 m -3 were formed in the specimens irradiated to 1×10 19 ions/m 2, and they were approximately equivalent, except for Ni-Si. The mean size of loops tended to increase with the volume size factor of solute atoms. In a dose of 4×10 20 ions/m 2, the swelling was changed from 0.2% to 4.5%, depending on the volume size factors. The number densities of bubbles tended to increase with the absolute values of the volume size factor, and the swelling increased with the volume size factors. This suggests that the mobility of helium and vacancy atoms may be influenced by the interaction of solute atoms with them.

PubChem atom environments.

Science.gov (United States)

Hähnke, Volker D; Bolton, Evan E; Bryant, Stephen H

2015-01-01

seemingly due to erroneous interpretation of structures from patent data. Compared to fragmentation statistics published 40 years ago, the exponential growth in chemistry is mirrored in a nearly eightfold increase in the number of unique chemical fragments; however, this result is clearly an upper bound estimate as earlier studies employed structure sampling approaches and this study shows that a relatively high rate of atom fragments are found in only a single chemical structure (singletons). In addition, the percentage of singletons grows as the size of the chemical fragment is increased. The observed growth of the numbers of unique fragments over time suggests that many chemically possible connections of atom types to larger fragments have yet to be explored by chemists. A dramatic drop in the relative rate of increase of atom environments from smaller to larger fragments shows that larger fragments mainly consist of diverse combinations of a limited subset of smaller fragments. This is further supported by the observed concomitant increase of singleton atom environments. Combined, these findings suggest that there is considerable opportunity for chemists to combine known fragments to novel chemical compounds. The comparison of PubChem to an older study of known chemical structures shows noticeable differences. The changes suggest advances in synthetic capabilities of chemists to combine atoms in new patterns. Log-log plots of fragment incidence show small numbers of fragments are found in many structures and that large numbers of fragments are found in very few structures, with nearly half being novel using the methods in this work. The relative decrease in the count of new fragments as a function of size further suggests considerable opportunity for more novel chemicals exists. Lastly, the differences in atom environment diversity between PubChem Substance and Compound showcase the effect of PubChem standardization protocols, but also indicate that a normalization

Electron scattering by trapped fermionic atoms

International Nuclear Information System (INIS)

Wang Haijun; Jhe, Wonho

2002-01-01

Considering the Fermi gases of alkali-metal atoms that are trapped in a harmonic potential, we study theoretically the elastic and inelastic scattering of the electrons by the trapped Fermi atoms and present the corresponding differential cross sections. We also obtain the stopping power for the cases that the electronic state as well as the center-of-mass state are excited both separately and simultaneously. It is shown that the elastic scattering process is no longer coherent in contrast to the electron scattering by the atomic Bose-Einstein condensate (BEC). For the inelastic scattering process, on the other hand, the differential cross section is found to be proportional to the 2/3 power of the number of the trapped atoms. In particular, the trapped fermionic atoms display the effect of ''Fermi surface,'' that is, only the energy levels near the Fermi energy have dominant contributions to the scattering process. Moreover, it is found that the stopping power scales as the 7/6 power of the atomic number. These results are fundamentally different from those of the electron scattering by the atomic BEC, mainly due to the different statistics obeyed by the trapped atomic systems

Derivation of linear attenuation coefficients from CT numbers for low-energy photons

International Nuclear Information System (INIS)

Watanabe, Y.

1999-01-01

One can estimate photon attenuation properties from the CT number. In a standard method one assumes that the linear attenuation coefficient is proportional to electron density and ignores its nonlinear dependence on atomic number. When the photon energy is lower than about 50 keV, such as for brachytherapy applications, however, photoelectric absorption and Rayleigh scattering become important. Hence the atomic number must be explicitly considered in estimating the linear attenuation coefficient. In this study we propose a method to more accurately estimate the linear attenuation coefficient of low-energy photons from CT numbers. We formulate an equation that relates the CT number to the electron density and the effective atomic number. We use a CT calibration phantom to determine unknown coefficients in the equation. The equation with a given CT number is then solved for the effective atomic number, which in turn is used to calculate the linear attenuation coefficient for low-energy photons. We use the CT phantom to test the new method. The method significantly improves the standard method in estimating the attenuation coefficient at low photon energies (20keV≤E≤40keV) for materials with high atomic numbers. (author)

Angular momentum coupling in atom-atom collisions

International Nuclear Information System (INIS)

Grosser, J.

1986-01-01

The coupling between the electronic angular momentum and the rotating atom-atom axis in the initial or the final phase of an atom-atom collision is discussed, making use of the concepts of radial and rotational (Coriolis) coupling between different molecular states. The description is based on a limited number of well-understood approximations, and it allows an illustrative geometric representation of the transition from the body fixed to the space fixed motion of the electrons. (orig.)

Multi-atom Jaynes-Cummings model with nonlinear effects

International Nuclear Information System (INIS)

Aleixo, Armando Nazareno Faria; Balantekin, Akif Baha; Ribeiro, Marco Antonio Candido

2001-01-01

The standard Jaynes-Cummings (JC) model and its extensions, normally used in quantum optics, idealizes the interaction of matter with electromagnetic radiation by a simple Hamiltonian of a two-level atom coupled to a single bosonic mode. This Hamiltonian has a fundamental importance to the field of quantum optics and it is a central ingredient in the quantized description of any optical system involving the interaction between light and atoms. The JC Hamiltonian defines a molecule, a composite system formed from the coupling of a two-state system and a quantized harmonic oscillator. For this Hamiltonian, mostly the single-particle situation has been studied. This model can also be extended for the situation where one has N two-level systems, which interact only with the electromagnetic radiation. In this case the effects of the spatial distribution of the particles it is not taken into account and the spin angular momentum S-circumflex i of each particle contributes to form a total angular momentum J-circumflex of the system. When one considers the effects due to the spatial variation in the field intensity in a nonlinear medium it is necessary to further add a Kerr term to the standard JC Hamiltonian. This kind of nonlinear JC Hamiltonian is used in the study of micro masers. Another nonlinear variant of the JC model takes the coupling between matter and the radiation to depend on the intensity of the electromagnetic field. This model is interesting since this kind of interaction means that effectively the coupling is proportional to the amplitude of the field representing a very simple case of a nonlinear interaction corresponding to a more realistic physical situation. In this work we solve exactly the problem of the interaction of a N two-level atoms with an electromagnetic radiation when nonlinear effects due to the spatial variation in the field intensity in a nonlinear Kerr medium and the dependence on the intensity of the electromagnetic field on the matter

Squeezing effects of an atom laser: Beyond the linear model

International Nuclear Information System (INIS)

Jing Hui; Ge Molin; Chen Jingling

2002-01-01

We investigate the quantum dynamics and statistics of an atom laser by taking into account binary atom-atom collisions. The rotating wave approximation Hamiltonian of the system is solved analytically . We show that the nonlinear atom-atom interactions could yield periodic quadrature squeezing effects in the atom laser output beam, although the input radio frequency field is in a Glauber coherent state

System and process for determining the basis weight of a low atomic number material in a mixture with a higher atomic number material

International Nuclear Information System (INIS)

Hegland, P.; Dahlquist, J.

1985-01-01

A process for determining the relative quantity of low atomic energy material mixed with a higher atomic energy material is carried out by directing a first and second beam of x-rays into the mixture. The process includes transmitting x-rays directly to detectors to set one criterion, shielding the detectors from the x-ray sources to set another criterion and then passing samples of known relative composition to provide data for storage and calibration carrying out the process of mixtures to be measured

Ionization effects in electronic inner-shells of ionized atoms

International Nuclear Information System (INIS)

Shchornak, G.

1983-01-01

A review of the atomic physics of ionization atoms has been presented. Interaction and structure effects in atomic shells, correlated to the occurrence of vacancies in several subshells of the atom have been considered. The methods of calculations of atomic states and wave functions have been reviewed. The energy shift of characteristic X-rays is discussed as a function of the ionization stage of the atom. The influence of inner and outer-shell vacancies on the energy of the X-rays is shown in detail. The influence of chemical effects on the parameters of X-rays is also taken into account. Further on, the change of transition probabilities in radiative and non-radiative transitions by changing stage of ionization is discussed; and among them the leading part of Auger and Coster-Kronig transitions by the arearrangement of the atomic states is shown. The influence of non-radiative electronic transitions on ionization cross-sections for multiple ionization is discussed. Using these results, ionization cross-sections for direct and indirect processes for several ionization stages are given

Leukemia in atomic bomb survivors. 1. General observations. Leukemia in survivors of atomic bombing. Cytologic and biochemical studies on the granulocytes in early leukemia among atomic bomb survivors. Leukemogenic effects of ionizing radiation on atomic bomb survivors in Hiroshima City

Energy Technology Data Exchange (ETDEWEB)

Lange, R D; Moloney, W C; Yamawaki, Tokuso; Kastenbaum, M A

1959-01-01

This document contains 4 separate reports on leukemia in survivals of the atomic explosions in Hiroshima and Nagasaki. In the first report, observations on seventy-five established cases of leukemia occurring in people exposed to atomic bomb radiation are presented. These data indicate a great increase in the incidence of leukemia among atomic bomb survivors due to a single massive exposure to ionizing radiation. The leukemogenic effects of radiation are manifested equally in both sexes and at all age levels represented in this series. The striking preponderance of chronic myelogenous leukemia compared to chronic lymphatic leukemia has been noted in exposed individuals but it is pointed out that chronic lymphatic leukemia is comparatively rare among the Japanese. Cases of leukemia are still appearing in atomic bomb survivors. However, since 1950 there has been a steady decline in the number of cases. The second report consists of a review of all cases of leukemia referred to the ABCC from 1948 to April 1952, a total of 75 cases. In the third report, hematological and biochemical findings in separated leukocytes of four cases of preclinical myelogenous leukemia developing in atomic bomb survivors are described. The incidence of leukemia among survivors in Hiroshima is the topic of the fourth report. 38 references, 8 figures, 10 tables.

Quantum coherent tractor beam effect for atoms trapped near a nanowaveguide

Science.gov (United States)

Sadgrove, Mark; Wimberger, Sandro; Nic Chormaic, Síle

2016-01-01

We propose several schemes to realize a tractor beam effect for ultracold atoms in the vicinity of a few-mode nanowaveguide. Atoms trapped near the waveguide are transported in a direction opposite to the guided mode propagation direction. We analyse three specific examples for ultracold 23Na atoms trapped near a specific nanowaveguide (i.e. an optical nanofibre): (i) a conveyor belt-type tractor beam effect, (ii) an accelerator tractor beam effect, and (iii) a quantum coherent tractor beam effect, all of which can effectively pull atoms along the nanofibre toward the light source. This technique provides a new tool for controlling the motion of particles near nanowaveguides with potential applications in the study of particle transport and binding as well as atom interferometry. PMID:27440516

Single atom spectroscopy: Decreased scattering delocalization at high energy losses, effects of atomic movement and X-ray fluorescence yield

International Nuclear Information System (INIS)

Tizei, Luiz H.G.; Iizumi, Yoko; Okazaki, Toshiya; Nakanishi, Ryo; Kitaura, Ryo; Shinohara, Hisanori; Suenaga, Kazu

2016-01-01

Single atom localization and identification is crucial in understanding effects which depend on the specific local environment of atoms. In advanced nanometer scale materials, the characteristics of individual atoms may play an important role. Here, we describe spectroscopic experiments (electron energy loss spectroscopy, EELS, and Energy Dispersed X-ray spectroscopy, EDX) using a low voltage transmission electron microscope designed towards single atom analysis. For EELS, we discuss the advantages of using lower primary electron energy (30 keV and 60 keV) and higher energy losses (above 800 eV). The effect of atomic movement is considered. Finally, we discuss the possibility of using atomically resolved EELS and EDX data to measure the fluorescence yield for X-ray emission.

Determination of the Rb atomic number density in dense rubidium vapors by absorption measurements of Rb2 triplet bands

International Nuclear Information System (INIS)

Horvatic, Vlasta; Veza, Damir; Niemax, Kay; Vadla, Cedomil

2008-01-01

A simple and accurate way of determining atom number densities in dense rubidium vapors is presented. The method relies on the experimental finding that the reduced absorption coefficients of the Rb triplet satellite bands between 740 nm and 750 nm and the triplet diffuse band between 600 nm and 610 nm are not temperature dependent in the range between 600 K and 800 K. Therefore, the absolute values of the reduced absorption coefficients of these molecular bands can provide accurate information about atomic number density of the vapor. The rubidium absorption spectrum was measured by spatially resolved white-light absorption in overheated rubidium vapor generated in a heat pipe oven. The absolute values for the reduced absorption coefficients of the triplet bands were determined at lower vapor densities, by using an accurate expression for the reduced absorption coefficient in the quasistatic wing of the Rb D1 line, and measured triplet satellite bands to the resonance wing optical depth ratio. These triplet satellite band data were used to calibrate in absolute scale the reduced absorption coefficients of the triplet diffuse band at higher temperatures. The obtained values for the reduced absorption coefficient of these Rb molecular features can be used for accurate determination of rubidium atomic number densities in the range from about 5 x 10 16 cm -3 to 1 x 10 18 cm -3

Chemical composition, effective atomic number and electron density study of trommel sieve waste (TSW), Portland cement, lime, pointing and their admixtures with TSW in different proportions

International Nuclear Information System (INIS)

Kurudirek, Murat; Aygun, Murat; Erzeneoglu, Salih Zeki

2010-01-01

The trommel sieve waste (TSW) which forms during the boron ore production is considered to be a promising building material with its use as an admixture with Portland cement and is considered to be an alternative radiation shielding material, also. Thus, having knowledge on the chemical composition and radiation interaction properties of TSW as compared to other building materials is of importance. In the present study, chemical compositions of the materials used have been determined using a wavelength dispersive X-ray fluorescence spectrometer (WDXRFS). Also, TSW, some commonly used building materials (Portland cement, lime and pointing) and their admixtures with TSW have been investigated in terms of total mass attenuation coefficients (μ/ρ), photon interaction cross sections (σ t ), effective atomic numbers (Z eff ) and effective electron densities (N e ) by using X-rays at 22.1, 25 keV and γ-rays at 88 keV photon energies. Possible conclusions were drawn with respect to the variations in photon energy and chemical composition.

Studies on effective atomic numbers for photon energy absorption and electron density of some narcotic drugs in the energy range 1 keV-20 MeV

Science.gov (United States)

Gounhalli, Shivraj G.; Shantappa, Anil; Hanagodimath, S. M.

2013-04-01

Effective atomic numbers for photon energy absorption ZPEA,eff, photon interaction ZPI,eff and for electron density Nel, have been calculated by a direct method in the photon-energy region from 1 keV to 20 MeV for narcotic drugs, such as Heroin (H), Cocaine (CO), Caffeine (CA), Tetrahydrocannabinol (THC), Cannabinol (CBD), Tetrahydrocannabivarin (THCV). The ZPEA,eff, ZPI,eff and Nel values have been found to change with energy and composition of the narcotic drugs. The energy dependence ZPEA,eff, ZPI,eff and Nel is shown graphically. The maximum difference between the values of ZPEA,eff, and ZPI,eff occurs at 30 keV and the significant difference of 2 to 33% for the energy region 5-100 keV for all drugs. The reason for these differences is discussed.

Experimental measurement of effective atomic number of composite ...

Indian Academy of Sciences (India)

2011-08-02

Aug 2, 2011 ... composite materials for Compton effect in the γ-ray region ... range. The method was employed to evaluate Zeff for different inorganic ... cations of radiation such as dosimetry, shielding, industrial radiography etc., in the photon.

Effect of mode–mode competition on atom–atom entanglement

International Nuclear Information System (INIS)

Qin, Wu; Mao-Fa, Fang; Jian-Wu, Cai

2010-01-01

A system consisting of two atoms interacting with a two-mode vacuum is considered, where each atom is resonant with the two cavity modes through two different competing transitions. The effect of mode–mode competition on the atom–atom entanglement is investigated. We find that the entanglement between the two atoms can be induced by the mode–mode competition. For the initial atomic state |Ψ(0)}, whether the atoms are initially separated or entangled, a large or even maximal entanglement between them can be obtained periodically by introducing the mode–mode competition. For the initial atomic state |Φ(0)}, the strong mode–mode competition can prevent the two atoms entangled initially from suffering entanglement sudden death; besides, it makes them in a more stable and longer-lived entanglement than in the non-competition case. (classical areas of phenomenology)

Topics relating to atomic collisions in dilute Bose-Einstein condensates

International Nuclear Information System (INIS)

Roberts, David C.

2002-01-01

In this thesis, we investigate various aspects of applications and limitations arising from atomic collisions in dilute Bose-Einstein condensates. First, we investigate the relative particle number squeezing produced in the excited states of a dilute condensate at zero temperature using stimulated light scattering. We show that a modest number of relative number squeezed particles can be achieved when atoms, produced in pairs through collisions in the condensate, are scattered out by their interaction with the lasers. This squeezing is optimal when the momentum is larger than the inverse healing length. This modest number of relative number squeezed particles has the potential to be amplified in four-wave-mixing experiments. We study the limitations on the relative number squeezing between photons and atoms coupled out from a homogeneous Bose-Einstein condensate. We consider the coupling between the translational atomic states by two photon Bragg processes, one of the photon modes involved in the Bragg process being in a coherent state, and the other initially unpopulated. We start with an interacting condensate at zero temperature and compute the time evolution for the system. We discuss how collisions between the atoms and photon rescattering affect the degree of squeezing which may be reached in such experiments. We investigate the limitations arising from atomic collisions on the storage and delay times of probe pulses in EIT experiments. We find that the atomic collisions can be described by an effective decay rate that limits storage and delay times. We calculate the momentum and temperature dependence of the decay rate and find that it is necessary to excite atoms to a particular momentum depending on temperature and spacing of the energy levels involved in order to minimize the decoherence effects of atomic collisions. Finally, we propose a method to probe states in the Mott insulator regime produced from a condensate in an optical lattice. We consider a

Phosphorus {delta}-doped silicon: mixed-atom pseudopotentials and dopant disorder effects

Energy Technology Data Exchange (ETDEWEB)

Carter, Damien J; Marks, Nigel A [Nanochemistry Research Institute, Curtin University, PO Box U1987, Perth WA 6845 (Australia); Warschkow, Oliver; McKenzie, David R, E-mail: d.carter@curtin.edu.au [Centre for Quantum Computer Technology, School of Physics, University of Sydney, Sydney, NSW 2006 (Australia)

2011-02-11

Within a full density functional theory framework we calculate the band structure and doping potential for phosphorus {delta}-doped silicon. We compare two different representations of the dopant plane; pseudo-atoms in which the nuclear charge is fractional between silicon and phosphorus, and explicit arrangements employing distinct silicon and phosphorus atoms. While the pseudo-atom approach offers several computational advantages, the explicit model calculations differ in a number of key points, including the valley splitting, the Fermi level and the width of the doping potential. These findings have implications for parameters used in device modelling.

Atomic structures and mechanical properties of single-crystal GaN nanotubes

International Nuclear Information System (INIS)

Xu, B.; Lu, A.J.; Pan, B.C.; Yu, Q.X.

2005-01-01

An approach is proposed to theoretically construct a realistic single-crystal GaN nanotube at atomic scale. The generated atomic structures of the single-crystal GaN nanotubes match the structural aspects from experiment very well. Our energetic calculations show that a single-crystal GaN nanotube with [100]-oriented lateral facets is more stable than that with [110]-oriented lateral facets, when they have around the same wall thickness. For a specified orientation of the lateral facets on the single-crystal GaN nanotubes, the energetic stabilities of the tubes obey a P rule, in which P is the ratio of the number of four-coordinated atoms to the number of three-coordinated atoms. Furthermore, the Young's modulus of the considered GaN nanotubes decrease with increasing the ratio of the number of bulk atoms to the number of surface atoms in each type of tube. Our calculations and analysis demonstrate that the surface effect of a single-crystal nanotube enhances its Young's modulus significantly

Modification of diode characteristics by electron back-scatter from high-atomic-number anodes

International Nuclear Information System (INIS)

Mosher, D.; Cooperstein, G.; Rose, D.V.; Swanekamp, S.B.

1996-01-01

In high-power vacuum diodes with high-atomic-number anodes, back-scattered electrons alter the vacuum space charge and resulting electron and ion currents. Electron multiple back-scattering was studied through equilibrium solutions of the Poisson equation for 1-dimensional, bipolar diodes in order to predict their early-time behavior. Before ion turn-on, back-scattered electrons from high-Z anodes suppress the diode current by about 10%. After ion turn-on in the same diodes, electron back-scatter leads to substantial enhancements of both the electron and ion currents above the Child-Langmuir values. Current enhancements with ion flow from low-Z anodes are small. (author). 5 figs., 7 refs

Modification of diode characteristics by electron back-scatter from high-atomic-number anodes

Energy Technology Data Exchange (ETDEWEB)

Mosher, D; Cooperstein, G [Naval Research Laboratory, Washington, DC (United States); Rose, D V; Swanekamp, S B [JAYCOR, Vienna, VA (United States)

1997-12-31

In high-power vacuum diodes with high-atomic-number anodes, back-scattered electrons alter the vacuum space charge and resulting electron and ion currents. Electron multiple back-scattering was studied through equilibrium solutions of the Poisson equation for 1-dimensional, bipolar diodes in order to predict their early-time behavior. Before ion turn-on, back-scattered electrons from high-Z anodes suppress the diode current by about 10%. After ion turn-on in the same diodes, electron back-scatter leads to substantial enhancements of both the electron and ion currents above the Child-Langmuir values. Current enhancements with ion flow from low-Z anodes are small. (author). 5 figs., 7 refs.

AtomPy: An Open Atomic Data Curation Environment for Astrophysical Applications

Directory of Open Access Journals (Sweden)

Claudio Mendoza

2014-05-01

Full Text Available We present a cloud-computing environment, referred to as AtomPy, based on Google-Drive Sheets and Pandas (Python Data Analysis Library DataFrames to promote community-driven curation of atomic data for astrophysical applications, a stage beyond database development. The atomic model for each ionic species is contained in a multi-sheet workbook, tabulating representative sets of energy levels, A-values and electron impact effective collision strengths from different sources. The relevant issues that AtomPy intends to address are: (i data quality by allowing open access to both data producers and users; (ii comparisons of different datasets to facilitate accuracy assessments; (iii downloading to local data structures (i.e., Pandas DataFrames for further manipulation and analysis by prospective users; and (iv data preservation by avoiding the discard of outdated sets. Data processing workflows are implemented by means of IPython Notebooks, and collaborative software developments are encouraged and managed within the GitHub social network. The facilities of AtomPy are illustrated with the critical assessment of the transition probabilities for ions in the hydrogen and helium isoelectronic sequences with atomic number Z ≤ 10.

Single atom spectroscopy: Decreased scattering delocalization at high energy losses, effects of atomic movement and X-ray fluorescence yield.

Science.gov (United States)

Tizei, Luiz H G; Iizumi, Yoko; Okazaki, Toshiya; Nakanishi, Ryo; Kitaura, Ryo; Shinohara, Hisanori; Suenaga, Kazu

2016-01-01

Single atom localization and identification is crucial in understanding effects which depend on the specific local environment of atoms. In advanced nanometer scale materials, the characteristics of individual atoms may play an important role. Here, we describe spectroscopic experiments (electron energy loss spectroscopy, EELS, and Energy Dispersed X-ray spectroscopy, EDX) using a low voltage transmission electron microscope designed towards single atom analysis. For EELS, we discuss the advantages of using lower primary electron energy (30 keV and 60 keV) and higher energy losses (above 800 eV). The effect of atomic movement is considered. Finally, we discuss the possibility of using atomically resolved EELS and EDX data to measure the fluorescence yield for X-ray emission. Copyright © 2015 Elsevier B.V. All rights reserved.

Atomic polarizabilities

International Nuclear Information System (INIS)

Safronova, M. S.; Mitroy, J.; Clark, Charles W.; Kozlov, M. G.

2015-01-01

The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed

Atomic polarizabilities

Energy Technology Data Exchange (ETDEWEB)

Safronova, M. S. [Department of Physics and Astronomy, University of Delaware, Newark, DE 19716 (United States); Mitroy, J. [School of Engineering, Charles Darwin University, Darwin NT 0909 (Australia); Clark, Charles W. [Joint Quantum Institute, National Institute of Standards and Technology and the University of Maryland, Gaithersburg, Maryland 20899-8410 (United States); Kozlov, M. G. [Petersburg Nuclear Physics Institute, Gatchina 188300 (Russian Federation)

2015-01-22

The atomic dipole polarizability governs the first-order response of an atom to an applied electric field. Atomic polarization phenomena impinge upon a number of areas and processes in physics and have been the subject of considerable interest and heightened importance in recent years. In this paper, we will summarize some of the recent applications of atomic polarizability studies. A summary of results for polarizabilities of noble gases, monovalent, and divalent atoms is given. The development of the CI+all-order method that combines configuration interaction and linearized coupled-cluster approaches is discussed.

Development of a standard data base for FBR core nuclear design. 10. Reevaluation of atomic number density of JOYO Mk-II core

Energy Technology Data Exchange (ETDEWEB)

Numata, Kazuyuki; Sato, Wakaei [Japan Nuclear Cycle Development Inst., Oarai, Ibaraki (Japan). Oarai Engineering Center; Ishikawa, Makoto; Arii, Yoshio [Nuclear Energy System Incorporation, Tokyo (Japan)

1999-07-01

The material composition of JOYO Mk-II core components in its initial core was reevaluated as a part of the effort for developing a standard data base for FBR core nuclear design. The special feature of the reevaluation is to treat the decay of Pu-241 isotope, so that the atomic number densities of Pu-241 and Am-241 in fuel assemblies can be exactly evaluated on the initial critical date, Nov. 22nd, 1982. Further, the atomic number densities of other core components were also evaluated to improve the analytical accuracy. Those include the control rods which were not so strictly evaluated in the past, and the dummy fuels and the neutron sources which were not treated in the analytical model so far. The results of the present reevaluation were as follows: (1) The changes of atomic number densities of the major nuclides such as Pu-239, U-235 and U-238 were about {+-}0.2 to 0.3%. On the other hand, the number density of Pu-241, which was the motivation of the present work, was reduced by 12%. From the fact, the number densities in the past analysis might be based on the isotope measurement of the manufacturing point of time without considering the decay of Pu-241. (2) As the other core components, the number densities of control rods and outer reflector-type A were largely improved. (author)

High fidelity simulation and analysis of liquid jet atomization in a gaseous crossflow at intermediate Weber numbers

Energy Technology Data Exchange (ETDEWEB)

Li, Xiaoyi, E-mail: lixy2@utrc.utc.com; Soteriou, Marios C. [United Technologies Research Center, East Hartford, Connecticut 06108 (United States)

2016-08-15

Recent advances in numerical methods coupled with the substantial enhancements in computing power and the advent of high performance computing have presented first principle, high fidelity simulation as a viable tool in the prediction and analysis of spray atomization processes. The credibility and potential impact of such simulations, however, has been hampered by the relative absence of detailed validation against experimental evidence. The numerical stability and accuracy challenges arising from the need to simulate the high liquid-gas density ratio across the sharp interfaces encountered in these flows are key reasons for this. In this work we challenge this status quo by presenting a numerical model able to deal with these challenges, employing it in simulations of liquid jet in crossflow atomization and performing extensive validation of its results against a carefully executed experiment with detailed measurements in the atomization region. We then proceed to the detailed analysis of the flow physics. The computational model employs the coupled level set and volume of fluid approach to directly capture the spatiotemporal evolution of the liquid-gas interface and the sharp-interface ghost fluid method to stably handle high liquid-air density ratio. Adaptive mesh refinement and Lagrangian droplet models are shown to be viable options for computational cost reduction. Moreover, high performance computing is leveraged to manage the computational cost. The experiment selected for validation eliminates the impact of inlet liquid and gas turbulence and focuses on the impact of the crossflow aerodynamic forces on the atomization physics. Validation is demonstrated by comparing column surface wavelengths, deformation, breakup locations, column trajectories and droplet sizes, velocities, and mass rates for a range of intermediate Weber numbers. Analysis of the physics is performed in terms of the instability and breakup characteristics and the features of downstream

A method to determine exactly the effective atomic number, electron density and absorbtion coefficient of materials from two Computer-Tomography measurement

International Nuclear Information System (INIS)

Christ, G.

1981-01-01

By the method of computer tomography, which is in use since about 10 years, X-ray images of a layer of interest can be produced without interference from the material present above this layer. An integral measurement of the attenuation of continuous X-radiation is sufficient to record the different attenuation behaviour in a layer for the purpose of image formation. For more information, however, can be obtained by taking into account the spectral distribution of the X-ray source and the energy dependence of the attenuation, which varies for different materials. In the experimental part of this work the measurement of the spectral distribution is described together with the necessary corrections, and the possible application of the cross sections for the relevant interaction processes, which are known from the literature is studied. As shown in the theoretical part, the attenuation coefficient can be described by an effective atomic number and the electron density of the absorber in the case of an arbitrary mixture of absorbing materials and a continuous X-ray spectrum. These two unknown material parameters can be determined by a method based on the measurement of two spectra with different spectral distribution. This is demonstrated by a one-dimensional and a two-dimensional computer simulation. (orig./WU) [de

Analysis of a single-atom dipole trap

International Nuclear Information System (INIS)

Weber, Markus; Volz, Juergen; Saucke, Karen; Kurtsiefer, Christian; Weinfurter, Harald

2006-01-01

We describe a simple experimental technique which allows us to store a single 87 Rb atom in an optical dipole trap. Due to light-induced two-body collisions during the loading stage of the trap the maximum number of captured atoms is locked to one. This collisional blockade effect is confirmed by the observation of photon antibunching in the detected fluorescence light. The spectral properties of single photons emitted by the atom were studied with a narrow-band scanning cavity. We find that the atomic fluorescence spectrum is dominated by the spectral width of the exciting laser light field. In addition we observe a spectral broadening of the atomic fluorescence light due to the Doppler effect. This allows us to determine the mean kinetic energy of the trapped atom corresponding to a temperature of 105 μK. This simple single-atom trap is the key element for the generation of atom-photon entanglement required for future applications in quantum communication and a first loophole-free test of Bell's inequality

Ultracold atoms in a cavity-mediated double-well system

International Nuclear Information System (INIS)

Larson, Jonas; Martikainen, Jani-Petri

2010-01-01

We study ground-state properties and dynamics of a dilute ultracold atomic gas in a double-well potential. The Gaussian barrier separating the two wells derives from the interaction between the atoms and a quantized field of a driven Fabry-Perot cavity. Due to intrinsic atom-field nonlinearity, several interesting phenomena arise which are the focus of this work. For the ground state, there is a critical pumping amplitude in which the atoms self-organize and the intra-cavity-field amplitude drastically increases. In the dynamical analysis, we show that the Josephson oscillations depend strongly on the atomic density and may be greatly suppressed within certain regimes, reminiscent of self-trapping of Bose-Einstein condensates in double-well setups. This pseudo-self-trapping effect is studied within a mean-field treatment valid for large atom numbers. For small numbers of atoms, we consider the analogous many-body problem and demonstrate a collapse-revival structure in the Josephson oscillations.

Spin valve effect in single-atom contacts

International Nuclear Information System (INIS)

Ziegler, M; Neel, N; Berndt, R; Lazo, C; Ferriani, P; Heinze, S; Kroeger, J

2011-01-01

Magnetic single-atom contacts have been controllably fabricated with a scanning tunnelling microscope. A voltage-dependent spin valve effect with conductance variations of ∼40% is reproducibly observed from contacts comprising a Cr-covered tip and Co and Cr atoms on ferromagnetic nanoscale islands on W(110) with opposite magnetization. The spin-dependent conductances are interpreted from first-principles calculations in terms of the orbital character of the relevant electronic states of the junction.

Effect of finite detection efficiency on the observation of the dipole-dipole interaction of a few Rydberg atoms

International Nuclear Information System (INIS)

Ryabtsev, I. I.; Tretyakov, D. B.; Beterov, I. I.; Entin, V. M.

2007-01-01

We have developed a simple analytical model describing multiatom signals that are measured in experiments on dipole-dipole interaction at resonant collisions of a few Rydberg atoms. It has been shown that finite efficiency of the selective field-ionization detector leads to the mixing up of the spectra of resonant collisions registered for various numbers of Rydberg atoms. The formulas which help to estimate an appropriate mean Rydberg atom number for a given detection efficiency are presented. We have found that a measurement of the relation between the amplitudes of collisional resonances observed in the one- and two-atom signals provides a straightforward determination of the absolute detection efficiency and mean Rydberg atom number. We also performed a testing experiment on resonant collisions in a small excitation volume of a sodium atomic beam. The resonances observed for 1-4 detected Rydberg atoms have been analyzed and compared with theory

Effects of radiation on hetero-atom-containing polyacetylenes

International Nuclear Information System (INIS)

Yamaoka, H.; Matsuyama, T.; Masuda, T.; Higashimura, T.

1991-01-01

The effects of radiation on several substituted polyacetylenes containing hetero-atoms such as silicon and chlorine were studied. All the polymers containing silicon atoms degraded in the presence of air, whereas no degradation proceeded in vacuo. In the case of polymers containing chlorine atoms, degradation and crosslinking occurred simultaneously, both in air and in vacuo. The reaction mode of these polymers was found to be strongly dependent on the nature of the substituents. The relationship between the radiation sensitivity and thermal stability of substituted polyacetylenes is discussed on the basis of the obtained results. (author)

Cancer and non-cancer effects in Japanese atomic bomb survivors

International Nuclear Information System (INIS)

Little, M P

2009-01-01

factors may contribute, such as the generally higher underlying cancer risks in the medical series than in the Japanese atomic bomb survivors. Risks among occupationally exposed groups such as nuclear workforces and underground miners are generally consistent with those observed in the Japanese atomic bomb survivors. In general, consistent patterns of variation of risk with age at exposure are also seen in all studies-risks for all cancer types diminish with increasing age at exposure. There are also excess risks of various types of non-malignant disease in the Japanese atomic bomb survivors, in particular cardiovascular, respiratory and digestive diseases. Indeed, risks are elevated to much the same degree for a number of non-malignant disease endpoints, suggestive of bias. However, in contrast with the cancer data, there is much less consistency in the pattern of risk between the atomic bomb survivors and other exposed groups; for example, radiation-associated respiratory and digestive diseases have not been seen in these other groups. Although cardiovascular risks have been seen elsewhere, particularly in medically exposed groups, in contrast with the cancer data there is much less consistency in risk between studies: risks per unit dose in epidemiological studies vary over at least two orders of magnitude, possibly as a result of confounding factors. In the absence of a convincing mechanistic explanation of epidemiological evidence, at present a cause-and-effect interpretation of the reported statistical associations for cardiovascular disease is unreliable but cannot be excluded. Further epidemiological and biological evidence will allow a firmer conclusion to be drawn.

Radiation Build-Up Of High Energy Gamma In Shielding Of High Atomic Number

International Nuclear Information System (INIS)

Yuliati, Helfi; Akhadi, Mukhlis

2000-01-01

Research to observe effect of radiation build-up factor (b) in iron (Fe) and lead (Pb) for high energy gamma shielding from exp.137 Cs (E gamma : 662 keV) and exp.60 Co (E gamma : 1332 keV) sources has been carried out. Research was conducted bt counting of radiation intensity behind shielding with its thickness vary from 1 to 5 times of half value thickness (HVT). NaI (TI) detector which connected to multi channel analyzer (MCA) was used for the counting. Calculation result show that all of b value are near to 1 (b∼1) both for Fe and Pb. Without inserting b in calculation, from the experiment it was obtained HVT value of Fe for high gamma radiation of 662 and 1332 keV were : (12,94 n 0,03) mm and (17,33 n 0,01) mm with their deviation standards were 0,2% and 0,06% respectively. Value of HVT for Pb with the same energy were : (6,31 n 0,03) mm and (11,86 n 0,03) mm with their deviation standars were : 0,48% and 0,25% respectively. HVL concept could be applied directly to estimate shielding thickness of high atomic number of high energy gamma radiation, without inserting correction of radiation build-up factor

Semiclassical approach to atomic decoherence by gravitational waves

Science.gov (United States)

Quiñones, D. A.; Varcoe, B. T. H.

2018-01-01

A new heuristic model of interaction of an atomic system with a gravitational wave (GW) is proposed. In it, the GW alters the local electromagnetic field of the atomic nucleus, as perceived by the electron, changing the state of the system. The spectral decomposition of the wave function is calculated, from which the energy is obtained. The results suggest a shift in the difference of the atomic energy levels, which will induce a small detuning to a resonant transition. The detuning increases with the quantum numbers of the levels, making the effect more prominent for Rydberg states. We performed calculations on the Rabi oscillations of atomic transitions, estimating how they would vary as a result of the proposed effect.

Suppression and enhancement of decoherence in an atomic Josephson junction

Science.gov (United States)

Japha, Yonathan; Zhou, Shuyu; Keil, Mark; Folman, Ron; Henkel, Carsten; Vardi, Amichay

2016-05-01

We investigate the role of interatomic interactions when a Bose gas, in a double-well potential with a finite tunneling probability (a ‘Bose-Josephson junction’), is exposed to external noise. We examine the rate of decoherence of a system initially in its ground state with equal probability amplitudes in both sites. The noise may induce two kinds of effects: firstly, random shifts in the relative phase or number difference between the two wells and secondly, loss of atoms from the trap. The effects of induced phase fluctuations are mitigated by atom-atom interactions and tunneling, such that the dephasing rate may be suppressed by half its single-atom value. Random fluctuations may also be induced in the population difference between the wells, in which case atom-atom interactions considerably enhance the decoherence rate. A similar scenario is predicted for the case of atom loss, even if the loss rates from the two sites are equal. We find that if the initial state is number-squeezed due to interactions, then the loss process induces population fluctuations that reduce the coherence across the junction. We examine the parameters relevant for these effects in a typical atom chip device, using a simple model of the trapping potential, experimental data, and the theory of magnetic field fluctuations near metallic conductors. These results provide a framework for mapping the dynamical range of barriers engineered for specific applications and set the stage for more complex atom circuits (‘atomtronics’).

Calculation of effective atomic number and electron density of essential biomolecules for electron, proton, alpha particle and multi-energetic photon interactions

Science.gov (United States)

Kurudirek, Murat; Onaran, Tayfur

2015-07-01

Effective atomic numbers (Zeff) and electron densities (Ne) of some essential biomolecules have been calculated for total electron interaction, total proton interaction and total alpha particle interaction using an interpolation method in the energy region 10 keV-1 GeV. Also, the spectrum weighted Zeff for multi-energetic photons has been calculated using Auto-Zeff program. Biomolecules consist of fatty acids, amino acids, carbohydrates and basic nucleotides of DNA and RNA. Variations of Zeff and Ne with kinetic energy of ionizing charged particles and effective photon energies of heterogeneous sources have been studied for the given materials. Significant variations in Zeff and Ne have been observed through the entire energy region for electron, proton and alpha particle interactions. Non-uniform variation has been observed for protons and alpha particles in low and intermediate energy regions, respectively. The maximum values of Zeff have found to be in higher energies for total electron interaction whereas maximum values have found to be in relatively low energies for total proton and total alpha particle interactions. When it comes to the multi-energetic photon sources, it has to be noted that the highest Zeff values were found at low energy region where photoelectric absorption is the pre-dominant interaction process. The lowest values of Zeff have been shown in biomolecules such as stearic acid, leucine, mannitol and thymine, which have highest H content in their groups. Variation in Ne seems to be more or less the same with the variation in Zeff for the given materials as expected.

Atomic physics constraints on the X boson

Science.gov (United States)

Jentschura, Ulrich D.; Nándori, István

2018-04-01

Recently, a peak in the light fermion pair spectrum at invariant q2≈(16.7MeV ) 2 has been observed in the bombardment of 7Li by protons. This peak has been interpreted in terms of a protophobic interaction of fermions with a gauge boson (X boson) of invariant mass ≈16.7 MeV which couples mainly to neutrons. High-precision atomic physics experiments aimed at observing the protophobic interaction need to separate the X boson effect from the nuclear-size effect, which is a problem because of the short range of the interaction (11.8 fm), which is commensurate with a "nuclear halo." Here we analyze the X boson in terms of its consequences for both electronic atoms as well as muonic hydrogen and deuterium. We find that the most promising atomic systems where the X boson has an appreciable effect, distinguishable from a finite-nuclear-size effect, are muonic atoms of low and intermediate nuclear charge numbers.

Atomic size effect on critical cooling rate and glass formation

International Nuclear Information System (INIS)

Jalali, Payman; Li Mo

2005-01-01

Atomic size effect on critical cooling rate and glass formability in a model binary system is investigated using molecular dynamics simulation. To isolate atomic size effect from the rest of the factors that critically influence the glass formation, a hard sphere model is employed in conjunction with a newly developed densification method. The glass formability is defined as a set of optimal conditions that result in the slowest cooling rate of the glass-forming liquid. Critical cooling rates are identified from extensive molecular dynamics simulations. A kinetic glass-forming diagram is mapped out that marks the boundary between the glass-forming regions and competing crystalline phases in terms of the parameters of the atomic size ratio and alloy concentration. It is found that the potency of the atomic size difference on glass formation is influenced greatly by the competing metastable and equilibrium crystalline phases in the system, and the kinetic processes leading to the formation of these phases. The mechanisms of the atomic size effect on topological instability of crystal packing and glass formation are discussed

A study of effective atomic numbers and electron densities of some vitamins for electron, H, He and C ion interactions

Science.gov (United States)

Büyükyıldız, M.

2017-09-01

The radiological properties of some vitamins such as Retinol, Beta-carotene, Riboflavin, Niacin, Niacinamide, Pantothenic acid, Pyridoxine, Pyridoxamine, Pyridoxal, Biotin, Folic acid, Ascorbic acid, Cholecalciferol, Alpha-tocopherol, Gamma-tocopherol, Phylloquinone have been investigated with respect to total electron interaction and some heavy charged particle interaction as means of effective atomic numbers (Z_{eff}) and electron densities (N_{eff}) for the first time. Calculations were performed for total electron interaction and heavy ions such as H, He and C ion interactions in the energy region 10keV-10MeV by using a logarithmic interpolation method. Variations in Z_{eff}'s and N_{eff}'s of given vitamins have been studied according to the energy of electron or heavy charged particles, and significant variations have been observed for all types of interaction in the given energy region. The maximum values of Z_{eff} have been found in the different energy regions for different interactions remarkably and variations in N_{eff} seem approximately to be the same with variation in Z_{eff} for the given vitamins as expected. Z_{eff} values of some vitamins were plotted together and compared with each other for electron, H, He and C interactions and the ratios of Z_{eff}/ have been changed in the range of 0.25-0.36, 0.20-0.36, 0.22-0.35 and 0.20-0.35 for electron, H, He and C interactions, respectively.

Defect-induced conductance oscillations in short atomic chains

International Nuclear Information System (INIS)

Wawrzyniak-Adamczewska, M; Kostyrko, T

2012-01-01

Electronic transport through a junction made of two gold electrodes connected with a gold chain containing a silver impurity is analyzed with a tight binding model and the density-functional theory. It is shown that the conductance depends in a simple way on the position of the impurity in the chain and the parity of the total number of atoms of the chain. For an odd chain the conductance takes on a higher value when the Ag impurity substitutes an even Au atom in the chain, and a lower one for an odd position of the Ag atom. In the case of an even chain the conductance hardly depends on the position of the Ag atom. This new kind of a defect-induced parity oscillation of the conductance is significantly more prominent than the well-known even-odd effect related to the dependence of the conductance on the parity of number of atoms in perfect chains. (paper)

On the bosonic atoms

Science.gov (United States)

Amusia, M. Ya.; Chernysheva, L. V.

2018-01-01

We investigate ground state properties of atoms, in which substitute fermions - electrons by bosons, namely π --mesons. We perform some calculations in the frame of modified Hartree-Fock (HF) equation. The modification takes into account symmetry, instead of anti-symmetry of the pair identical bosons wave function. The modified HF approach thus enhances (doubles) the effect of self-action for the boson case. Therefore, we accordingly modify the HF equations by eliminating the self-action terms "by hand". The contribution of meson-meson and meson-nucleon non-Coulomb interaction is inessential at least for atoms with low and intermediate nuclear charge, which is our main subject. We found that the binding energy of pion negative ions A π - , pion atoms A π , and the number of extra bound pions ΔN π increases with the growth of nuclear charge Z. For e.g. Xe ΔN π = 4. As an example of a simple process with a pion atom, we consider photoionization that differs essentially from that for electron atoms. Namely, it is not monotonic decreasing from the threshold but has instead a prominent maximum above threshold. We study also elastic scattering of pions by pion atoms.

Atomic physics

International Nuclear Information System (INIS)

Armbruster, P.; Beyer, H.; Bosch, F.; Dohmann, H.D.; Kozhuharov, C.; Liesen, D.; Mann, R.; Mokler, P.H.

1984-01-01

The heavy ion accelerator UNILAC is well suited to experiments in the field of atomic physics because, with the aid of high-energy heavy ions atoms can be produced in exotic states - that is, heavy atoms with only a few electrons. Also, in close collisions of heavy ions (atomic number Z 1 ) and heavy target atoms (Z 2 ) short-lived quasi-atomic 'superheavy' systems will be formed - huge 'atoms', where the inner electrons are bound in the field of the combined charge Z 1 + Z 2 , which exceeds by far the charge of the known elements (Z <= 109). Those exotic or transient superheavy atoms delivered from the heavy ion accelerator make it possible to study for the first time in a terrestrial laboratory exotic, but fundamental, processes, which occur only inside stars. Some of the basic research carried out with the UNILAC is discussed. This includes investigation of highly charged heavy atoms with the beam-foil method, the spectroscopy of highly charged slow-recoil ions, atomic collision studies with highly ionised, decelerated ions and investigations of super-heavy quasi-atoms. (U.K.)

Emission spectrum of a harmonically trapped Λ-type three-level atom

International Nuclear Information System (INIS)

Guo Hong; Tang Pei

2013-01-01

We theoretically investigate the emission spectrum for a Λ-type three-level atom trapped in the node of a standing wave. We show that the atomic center-of-mass motion not only directly affects the peak number, peak position, and peak height in the atomic emission spectrum, but also influences the effects of the cavity field and the atomic initial state on atomic emission spectrum. (electromagnetism, optics, acoustics, heat transfer, classical mechanics, and fluid dynamics)

Charge states of fast heavy ions in solids; target atomic number dependence

International Nuclear Information System (INIS)

Shima, Kunihiro

1985-01-01

Discussions were carried out on the origin of Z 2 (atomic number) dependent charge states with respect to projectile electron loss and capture process, and on relationship between the Z 2 dependence and that of mean charge states for heavy ions of 1 MeV/u energy region. Present and previously reported results were examined on the equilibrium charge distributions, 9-bar, of 120 MeV 63 Cu, 25 and 40 MeV 35 Cl, 109 MeV Si and 59 MeV F ions. It was clarified that 9-bar became generally higher for lower Z 2 depending on increasing energy, and osillatory behavior with energy-depending amplitude was seen in 9-bar vs Z 2 . Discussions were carrid out on these phenomena and related matters. Z 2 oscillations of 9-bar of fast heavy ions might be due to those of electron capture cross section into projectile K and L vacancies for high and intermediate charge states, respectively. A quantitative interpretation of the Z 2 -dependent 9-bar values is in progress based on collision process and observation of projectile x-ray. The 9-bar value dependency on Z 2 in ion passing foils and decrease of Z 2 oscillation amplitude with increasing collision energy were quite similar to the Z 2 dependence in stopping powers or in effective charge states estimated from stopping powers. But there was some discrepancies in the Z 2 oscillation of 9-bar and that of stopping powers. (Takagi, S.)

Atomic hydrogen effects on high-Tc superconductors

International Nuclear Information System (INIS)

Frantskevich, N.V.; Ulyashin, A.G.; Alifanov, A.V.; Stepanenko, A.V.; Fedotova, V.V.

1999-01-01

The atomic hydrogen effects on the properties of bulk high-temperature superconductors were investigated. It is shown that the insertion of the atomic hydrogen into the bulk of these materials from a DC plasma leads to the increase of the critical current density J c for YBaCuO(123) as well as for BiSrCaCuO(2223) high-temperature superconductors. It is found that the hydrogenation of the He implanted samples with following annealing leads to the optically detected blistering on the surface. It means that the textured thin subsurface layers of high-temperature superconductors can be formed by this method. The improvement of superconductivity by atomic hydrogen can be explained by the passivation of dangling bonds and defects on grain boundaries of these materials

Computational analysis of the atomic size effect in bulk metallic glasses and their liquid precursors

International Nuclear Information System (INIS)

Kokotin, V.; Hermann, H.

2008-01-01

The atomic size effect and its consequences for the ability of multicomponent liquid alloys to form bulk metallic glasses are analyzed in terms of the generalized Bernal's model for liquids, following the hypothesis that maximum density in the liquid state improves the glass-forming ability. The maximum density that can be achieved in the liquid state is studied in the 2(N-1) dimensional parameter space of N-component systems. Computer simulations reveal that the size ratio of largest to smallest atoms are most relevant for achieving the maximum packing for N = 3-5, whereas the number of components plays a minor role. At small size ratio, the maximum packing density can be achieved by different atomic size distributions, whereas for medium size ratios the maximum density is always correlated to a concave size distribution. The relationship of the results to Miracle's efficient cluster packing model is also discussed

Atomic-fluorescence spectrophotometry

International Nuclear Information System (INIS)

Bakhturova, N.F.; Yudelevich, I.G.

1975-01-01

Atomic-fluorescence spectrophotometry, a comparatively new method for the analysis of trace quantities, has developed rapidly in the past ten years. Theoretical and experimental studies by many workers have shown that atomic-fluorescence spectrophotometry (AFS) is capable of achieving a better limit than atomic absorption for a large number of elements. The present review examines briefly the principles of atomic-fluorescence spectrophotometry and the types of fluorescent transition. The excitation sources, flame and nonflame atomizers, used in AFS are described. The limits of detection achieved up to the present, using flame and nonflame methods of atomization are given

Electromagnetically Induced Transparency In Rydberg Atomic Medium

Science.gov (United States)

Deng, Li; Cong, Lu; Chen, Ai-Xi

2018-03-01

Due to possessing big principal quantum number, Rydberg atom has some unique properties, for example: its radiative lifetime is long, dipole moment is large, and interaction between atoms is strong and so on. These properties make one pay attention to Rydberg atoms. In this paper we investigate the effects of Rydberg dipole-dipole interactions on electromagnetically induced transparency (EIT) schemes and group velocity in three-level systems of ladder type, which provides theoretical foundation for exploring the linear and nonlinear characteristics of light in a Rydberg electromagnetically-induced-transparency medium.

Topics in atomic physics

CERN Document Server

Burkhardt, Charles E

2006-01-01

The study of atomic physics propelled us into the quantum age in the early twentieth century and carried us into the twenty-first century with a wealth of new and, in some cases, unexplained phenomena. Topics in Atomic Physics provides a foundation for students to begin research in modern atomic physics. It can also serve as a reference because it contains material that is not easily located in other sources. A distinguishing feature is the thorough exposition of the quantum mechanical hydrogen atom using both the traditional formulation and an alternative treatment not usually found in textbooks. The alternative treatment exploits the preeminent nature of the pure Coulomb potential and places the Lenz vector operator on an equal footing with other operators corresponding to classically conserved quantities. A number of difficult to find proofs and derivations are included as is development of operator formalism that permits facile solution of the Stark effect in hydrogen. Discussion of the classical hydrogen...

Differential cross sections for inelastic scattering of electrons on Kr and Xe atoms at intermediate energies

International Nuclear Information System (INIS)

Filipovic, D.M.

1989-01-01

Electron-impact excitation of the larger- number noble-gas atoms is a way of understanding excitation mechanisms in atomic collisional processes. Krypton and xenon have the largest atomic number of all the stable noble gases. Therefore, effects dependent on the size of a target atom, such as alignment and orientation of the atomic outer shell charge cloud after collisional excitation, are best observed by studying these atoms. Normalized, absolute differential cross sections (DCS's) for the lowest electronic states of Kr and Xe atoms, at intermediate energies, are the subject of this report

De Haas-van Alphen effect of a two-dimensional ultracold atomic gas

Science.gov (United States)

Farias, B.; Furtado, C.

2016-01-01

In this paper, we show how the ultracold atom analogue of the two-dimensional de Haas-van Alphen effect in electronic condensed matter systems can be induced by optical fields in a neutral atomic system. The interaction between the suitable spatially varying laser fields and tripod-type trapped atoms generates a synthetic magnetic field which leads the particles to organize themselves in Landau levels. Initially, with the atomic gas in a regime of lowest Landau level, we display the oscillatory behaviour of the atomic energy and its derivative with respect to the effective magnetic field (B) as a function of 1/B. Furthermore, we estimate the area of the Fermi circle of the two-dimensional atomic gas.

Atomic final-state effects in nuclear transitions

International Nuclear Information System (INIS)

Griffiths, A.; Vogel, P.

1991-01-01

The interaction of a nuclear gamma radiation with the atomic electron cloud gives rise to a phase shift in the nuclear electromagnetic transition amplitude. The resulting interference parameters ξ(πL) are of significance to the analysis of time-reversal experiments. We calculate these parameters for E1, E2, E3, M1, and M2 gamma transitions in a number of nuclei. We also discuss the implication of these results for simultaneous parity- and time-reversal-violating experiments

CrossRef Large numbers of cold positronium atoms created in laser-selected Rydberg states using resonant charge exchange

CERN Document Server

McConnell, R; Kolthammer, WS; Richerme, P; Müllers, A; Walz, J; Grzonka, D; Zielinski, M; Fitzakerley, D; George, MC; Hessels, EA; Storry, CH; Weel, M

2016-01-01

Lasers are used to control the production of highly excited positronium atoms (Ps*). The laser light excites Cs atoms to Rydberg states that have a large cross section for resonant charge-exchange collisions with cold trapped positrons. For each trial with 30 million trapped positrons, more than 700 000 of the created Ps* have trajectories near the axis of the apparatus, and are detected using Stark ionization. This number of Ps* is 500 times higher than realized in an earlier proof-of-principle demonstration (2004 Phys. Lett. B 597 257). A second charge exchange of these near-axis Ps* with trapped antiprotons could be used to produce cold antihydrogen, and this antihydrogen production is expected to be increased by a similar factor.

Understanding Atomic Structure: Is There a More Direct and Compelling Connection between Atomic Line Spectra and the Quantization of an Atom's Energy?

Science.gov (United States)

Rittenhouse, Robert C.

2015-01-01

The "atoms first" philosophy, adopted by a growing number of General Chemistry textbook authors, places greater emphasis on atomic structure as a key to a deeper understanding of the field of chemistry. A pivotal concept needed to understand the behavior of atoms is the restriction of an atom's energy to specific allowed values. However,…

Stop Band Gap in Periodic Layers of Confined Atomic Vapor/Dielectric Medium

International Nuclear Information System (INIS)

Li Yuan-Yuan; Li Li; Lu Yi-Xin; Zhang Yan-Peng; Xu Ke-Wei

2013-01-01

A stop band gap is predicted in periodic layers of a confined atomic vapor/dielectric medium. Reflection and transmission profile of the layers over the band gap can be dramatically modified by the confined atoms and the number of layer periods. These gap and line features can be ascribed to the enhanced contribution of slow atoms induced by atom-wall collision, transient behavior of atom-light interaction and Fabry—Pérot effects in a thermal confined atomic system

Relativistic effects in atomic inner-shell transitions

International Nuclear Information System (INIS)

Chen, M.H.

1982-01-01

Theoretical calculations of atomic inner-shell transition rates based on independent-particle models are reviewed. Factors affecting inner-shell transition rates are examined, particularly the effects of relativity. 48 references, 5 figures

Angular momentum effects in electron scattering from atoms

International Nuclear Information System (INIS)

Williams, J F; Cvejanovie, D; Samarin, S; Pravica, L; Napier, S; Sergeant, A

2007-01-01

This paper concerns angular momentum-dependent phenomena in excited gas-phase atoms using incident photons or electrons in scattering experiments. A brief overview indicates the main capabilities of experimental techniques and the information which can be deduced about atomic structure and dynamics from conservation of momenta with measurement of polarization and detection of the number of emerging electrons, photons and ions. Maximum information may be obtained when the incident particles and the targets are state-selected both before and after scattering. The fundamental scattering amplitudes and their relative phases, and consequently derived quantities such as the parameters describing the electron charge cloud of the atomic target, have enabled significant advances of understanding of collision mechanisms. The angular momentum-dependent scattering probabilities change when, for example, the spin-orbit interaction for the target electrons becomes large compared with the Coulomb electron-electron interactions and also when electron exchange and the relative orientation of the electron spins change. Several examples are discussed to indicate significant principles and recent advances. Major contributions to this field from the technology associated with electron spin production and detection time, as well as time-coincidence detection, are discussed. New results from the authors' laboratory are presented

Atom-surface potentials and atom interferometry

International Nuclear Information System (INIS)

Babb, J.F.

1998-01-01

Long-range atom-surface potentials characterize the physics of many actual systems and are now measurable spectroscopically in deflection of atomic beams in cavities or in reflection of atoms in atomic fountains. For a ground state, spherically symmetric atom the potential varies as -1/R 3 near the wall, where R is the atom-surface distance. For asymptotically large distances the potential is weaker and goes as -1/R 4 due to retardation arising from the finite speed of light. This diminished interaction can also be interpreted as a Casimir effect. The possibility of measuring atom-surface potentials using atomic interferometry is explored. The particular cases studied are the interactions of a ground-state alkali-metal atom and a dielectric or a conducting wall. Accurate descriptions of atom-surface potentials in theories of evanescent-wave atomic mirrors and evanescent wave-guided atoms are also discussed. (author)

Cold atoms in optical cavities and lattices

International Nuclear Information System (INIS)

Horak, P.

1996-11-01

The thesis is organized in three chapters covering different aspects of the interaction of atoms and light in the framework of theoretical quantum optics. In chapter 1 a special case of a microscopic laser where one or two atoms interact with several quantized cavity modes is discussed. In particular I investigate the properties of the light field created in one of the cavity modes. It is shown that a single-atom model already predicts average photon numbers in agreement with a semiclassical many-atom theory. The two-atom model exhibits additional collective features, such as superradiance and subradiance. In chapter 2 effects of the photon recoil on cold atoms in the limit of long-lived atomic transitions are investigated. First, I demonstrate that, in principle, relying on this scheme, a continuous-wave laser in the ultraviolet frequency domain could be established. Second, the splitting of an atomic beam into two coherent subbeams is discussed within the same scheme. Such beamsplitters play an important role in high-precision measurements using atomic interferometers. Finally, chapter 3 deals with cooling and trapping of atoms by the interaction with laser light. I discuss the properties and the light scattering of atoms trapped in a new light field configuration, a so-called dark optical superlattice. In principle, such systems allow the trapping of more than one atom in the ground state of a single optical potential well. This could give rise to the observation of e.g. atom-atom interactions and quantum statistical effects. (author)

Entanglement for a Bimodal Cavity Field Interacting with a Two-Level Atom

International Nuclear Information System (INIS)

Liu Jia; Chen Ziyu; Bu Shenping; Zhang Guofeng

2009-01-01

Negativity has been adopted to investigate the entanglement in a system composed of a two-level atom and a two-mode cavity field. Effects of Kerr-like medium and the number of photon inside the cavity on the entanglement are studied. Our results show that atomic initial state must be superposed, so that the two cavity field modes can be entangled. Moreover, we also conclude that the number of photon in the two cavity mode should be equal. The interaction between modes, namely, the Kerr effect, has a significant negative contribution. Note that the atom frequency and the cavity frequency have an indistinguishable effect, so a corresponding approximation has been made in this article. These results may be useful for quantum information in optics systems.

Atomic processes in matter-antimatter interactions

International Nuclear Information System (INIS)

Morgan, D.L.

1988-01-01

Atomic processes dominate antiproton stopping in matter at nearly all energies of interest. They significantly influence or determine the antiproton annihilation rate at all energies around or below several MeV. This article reviews what is known about these atomic processes. For stopping above about 10 eV the processes are antiproton-electron collisions, effective at medium keV through high MeV energies, and elastic collisions with atoms and adiabatic ionization of atoms, effective from medium eV through low keB energies. For annihilation above about 10 eV is the enhancement of the antiproton annihilation rate due to the antiproton-nucleus coulomb attraction, effective around and below a few tens of MeV. At about 10 eV and below, the atomic rearrangement/annihilation process determines both the stopping and annihilation rates. Although a fair amount of theoretical and some experimental work relevant to these processes exist, there are a number of energy ranges and material types for which experimental data does not exist and for which the theoretical information is not as well grounded or as accurate as desired. Additional experimental and theoretical work is required for accurate prediction of antiproton stopping and annihilation for energies and material relevant to antiproton experimentation and application

X-ray fluorescence from the element with atomic number Z=120

International Nuclear Information System (INIS)

Fregeau, M.O.; Morjean, M.; Bonnet, E.; Chbihi, A.; Frankland, J.D.; Jacquet, D.; Rivet, M.F.; Tassan-Got, L.; Dechery, F.; Drouart, A.; Nalpas, L.; Ledoux, X.; Parlog, M.; Parlog, M.; Ciortea, C.; Dumitriu, D.; Fluerasu, D.; Gugiu, M.; Gramegna, F.; Kravchuk, V.L.; Marchi, T.; Marchi, T.; Fabris, D.; Corsi, A.; Barlini, S.

2012-01-01

An atomic clock based on x-ray fluorescence yields has been used to estimate the mean characteristic time for fusion followed by fission in reactions 238 U + 64 Ni at 6.6 MeV/A. Inner shell vacancies are created during the collisions in the electronic structure of the possibly formed Z = 120 compound nuclei. The filling of these vacancies accompanied by a x-ray emission with energies characteristic of Z = 120 can take place only if the atomic transitions occur before nuclear fission. Therefore, the x-ray yield characteristic of the united atom with 120 protons is strongly related to the fission time and to the vacancy lifetimes. K x rays from the element with Z = 120 have been unambiguously identified from a coupled analysis of the involved nuclear reaction mechanisms and of the measured photon spectra. A minimum mean fission time τ f = 2.5 * 10 -18 s has been deduced for Z = 120 from the measured x-ray multiplicity. (authors)

Bibliography on atomic energy levels and spectra. Special pub., Jul 1971--Jun 1975

International Nuclear Information System (INIS)

Hagan, L.

1977-01-01

This is the first supplement to the NBS Special Publication 363, 'Bibliography on Atomic Energy Levels and Spectra, July 1968 through June 1971,' and it covers the most recent literature from July 1971 through June 1975. It contains approximately 2150 references classified by subject for individual atoms and atomic ions. A number index identifies the references. An author index is included. References included contain data on energy levels, classified lines, wavelengths, Zeeman effect, Stark effect, hyperfine structure, isotope shift, ionization potentials, or theory which gives results for specific atoms or atomic ions

Evolution Properties of Atomic Fidelity in the Combined Multi-Atom-Cavity Field System

International Nuclear Information System (INIS)

Wang Ju-Xia; Zhang Xiao-Juan; Zhang Xiu-Xing

2015-01-01

The atom fidelity is investigated in a system consisting of Mtwo-level atoms and M single-mode fields by use of complete quantum theory and numerical evaluation method. The influences of various system parameters on the evolution of atomic fidelity are studied. The results show that the atomic fidelity evolves in a Rabi oscillation manner. The oscillation frequency is mainly modulated by the coupling strength between atoms and light field, the atomic transition probabilities and the average photon numbers. Other factors hardly impact on the atomic fidelity. The present results may provide a useful approach to the maintenance of the atomic fidelity in the atom cavity field systems. (paper)

Atomic and molecular effects in the VUV spectra of solids

International Nuclear Information System (INIS)

Sonntag, B.

1977-10-01

The VUV spectra of solids are often dominated by atomic or molecular effects, which clearly manifest themselves in the gross features of the spectra and the fine structure at inner shell excitation thresholds. Evidence for the influence of atomic and molecular matrix elements, multiplet-splitting and correlation is presented. Special emphasis is given to the direct experimental verification based on the comparison of atomic and solid state spectra. (orig.) [de

Mechanical properties of cancer cells depend on number of passages: Atomic force microscopy indentation study

Science.gov (United States)

Dokukin, Maxim E.; Guz, Natalia V.; Sokolov, Igor

2017-08-01

Here we investigate one of the key questions in cell biology, if the properties of cell lines depend on the number of passages in-vitro. It is generally assumed that the change of cell properties (phenotypic drift) is insignificant when the number of passages is low (cell body and parameters of the pericellular brush layer from indentation force curves, which are recorded by means of atomic force microscopy (AFM). Using this method, we tested the change of the cell properties of human cancer breast epithelial cell line, MCF-7 (ATCC® HTB-22™), within the passages between 2 and 10. In contrast to the previous expectations, we observed a substantial transient change of the elastic modulus of the cell body during the first four passages (up to 4 times). The changes in the parameters of the pericellular coat were less dramatic (up to 2 times) but still statistically significant.

Effective atomic number, electron density and kerma of gamma ...

Indian Academy of Sciences (India)

rare element optical glass with oxides of tungsten, tantalum and thorium. ... Similarly, gadolinium and lutetium exhibit only +3 oxidation state because .... (σa) and effective molecular cross-section (σm) are related by the following equation: σa =.

Effect of flow conditions on spray cone angle of a two-fluid atomizer

Energy Technology Data Exchange (ETDEWEB)

Shafaee, Maziar; Banitabaei, Sayed Abdolhossein; Ashjaee, Mehdi; Esfahanian, Vahid [Tehran University, Tehran (Iran, Islamic Republic of)

2011-02-15

A visual study is conducted to determine the effects of operating conditions on the spray cone angle of a two-fluid atomizer. The liquid (water) jets exit from peripheral inclined orifices and are introduced into a high-speed gas (air) stream in the gravitational direction. Using a high-speed imaging system, the spray cone angle is determined for Reynolds numbers ranging from 4x10{sup 4} to 9x10{sup 4} and different Weber numbers up to 140. The droplet sizes (Sauter mean diameter) and their distributions are determined using a Malvern Mastersizer X. The results show that the spray cone angle depends on the operating conditions, especially in lower values of Reynolds and Weber numbers. An empirical correlation is also obtained to predict the spray cone angle in terms of these two parameters.

Effects of cetane number on HCCI combustion efficiency and emissions

Energy Technology Data Exchange (ETDEWEB)

Hosseini, V.; Neill, W.S.; Guo, H.; Chippior, W.L. [National Research Council of Canada, Ottawa, ON (Canada); Fairbridge, C. [Natural Resources Canada, Ottawa, ON (Canada); Mitchell, K. [Shell Canada Ltd., Calgary, AB (Canada)

2009-07-01

Homogeneous charge compression ignition (HCCI) is a form of internal combustion in which well-mixed fuel and oxidizer are compressed to the point of auto-ignition. This exothermic reaction releases chemical energy into a sensible form that can be transformed in an engine into work and heat. The effects of cetane number on HCCI combustion efficiency and emissions were examined in this presentation. The presentation discussed the experimental setup, fuels, experimental procedures, and results. The setup included an enhanced fuel injector/vaporizer consisting of an OEM gasoline port fuel injector, air blast for improved atomization, and heated section to improved vaporization. A minimally processed and low cetane number fuel derived from oil sands was used as the base fuel in the study. Two sets of experiments were devised and described to evaluate each test fuel. One set used controlled input conditions exhaust gas recirculation (EGR)-air-fuel ratio (AFR) while the other set employed controlled engine outputs (such as speed and load). Results were presented for hydroprocessing; cetane improver addition; blending with supercetane renewable diesel; and a comparison of fuels with similar cetane numbers. It was concluded that increasing the fuel cetane number shifted the AFR-EGR operating window for HCCI combustion towards higher AFT (leaner mixtures) and reduced the cyclic variations. tabs., figs.

Nonlinear spectroscopy of the Rydberg atoms

International Nuclear Information System (INIS)

Delone, N.B.; Krajnov, V.P.; Shepelyanskij, D.L.

1984-01-01

The results of investigation into perturbation of Rydberg states (RS) of atoms in an outer alternating field (OAF) are discussed. Both highly excited states of hydrogen atom at the energy Esub(n)=-1/2n -2 (n>>1 - basic quantum number) and excited states of compound atoms with energy Esub(nl)=-1/2(n*) -2 where n*=n-delta sub(e)-effective basic quantum number, delta sub(e)-quantum defect, are implied by RS. Perturbation of atomic state in the OAF is determined not only by field strength E, but by its frequency ω as well. During OAF inclusion the initial state Esub(lambda) transits to quasienergetic at the energy Esub(lambda)(E)+-kω, where K=0, +-1, +-2, .... Solutions of the problem of quasienergetic level population is obtained only for some simple particular cases. A simple case, when a real multilevel atom is replaced by a model system comprising one bound electron state with the basic quantum number n-model of the insulated level (MIL) is considered. Conditions of MIL applicability are discussed. Estimation of critical OAF strength at which MIL approximation becomes faulty are discussed. It is stated that any consideration of RS perturbation in OAF claiming to exceeding MIL frames should comprise consideration of ionization processes. If one keeps to the frames of OAF; the strength of which is lower than the determined critical values then MIL is true and use of this model permits to correctly describe the main features of RS perturbation in an alternating field

Efficiency of ablative plasma energy transfer into a massive aluminum target using different atomic number ablators

Czech Academy of Sciences Publication Activity Database

Kasperczuk, A.; Pisarczyk, T.; Chodukowski, T.; Kalinowska, Z.; Stepniewski, W.; Jach, K.; Swierczynski, R.; Renner, Oldřich; Šmíd, Michal; Ullschmied, Jiří; Cikhart, J.; Klír, D.; Kubeš, P.; Řezáč, K.; Krouský, Eduard; Pfeifer, Miroslav; Skála, Jiří

2015-01-01

Roč. 33, č. 3 (2015), s. 379-386 ISSN 0263-0346 R&D Projects: GA MŠk ED1.1.00/02.0061; GA MŠk(CZ) LD14089 EU Projects: European Commission(XE) 284464 - LASERLAB-EUROPE Grant - others:ELI Beamlines(XE) CZ.1.05/1.1.00/02.0061; AVČR(CZ) M100101208 Institutional support: RVO:68378271 ; RVO:61389021 Keywords : ablator atomic number * crater volume * laser energy transfer * plasma ablative pressure Subject RIV: BL - Plasma and Gas Discharge Physics; BH - Optics, Masers, Lasers (UFP-V) Impact factor: 1.649, year: 2015

Influence of operating conditions and atomizer design on circumferential liquid distribution from small pressure-swirl atomizer

Science.gov (United States)

Malý, Milan; Janáčková, Lada; Jedelský, Jan; Jícha, Miroslav

The spray symmetry is an important aspect in most practical applications. However, it is often an overlooked parameter. A measurement of circumferential distribution was carried out by a circular-sectored vessel on several pressure-swirl atomizers with spill-line over a wide range of injection pressure. The obtained results show that the spray uniformity improves markedly with the injection pressure. The increase in a number of tangential entry ports has only a minor effect on the spray uniformity. Even a small mechanical corruption of the atomizer internal parts negatively affects the spray patternation.

Determination of effective atomic number of breast tissues using scattered radiation; Determinacao do numero atomico efetivo de tecidos mamarios usando a radiacao espalhada

Energy Technology Data Exchange (ETDEWEB)

Antoniassi, M.; Conceicao, A.L.C.; Poletti, M.E. [Universidade de Sao Paulo (USP), Ribeirao Preto, SP (Brazil). Fac. de Filosofia, Ciencias e Letras. Dept. de Fisica e Matematica

2010-07-01

The scattered radiation has been used in several industrial and clinical applications since it permits to characterize the scattering material. Several types of information can be extracted from the spectrum of scattered radiation which can be used to characterization of biological tissues such as breast tissues. In this work we have measured Compton and Rayleigh scattering radiation from normal (adipose), benign (fibroadenoma) and malignant (carcinoma) neoplastic breast tissues using a monoenergetic beam of 17.44 keV and a scattering angle of 90 deg C (x = 0.99 angstrom-1). A practical method using the area of elastic and inelastic scattering was used for determining the effective atomic number (Z{sub eff}) of the samples, being validated comparing the experimental obtained values of Z{sub eff} of several standard materials with calculated values using traditional method based on total cross-section of compounds. The obtained results show that exist differences in the distributions of Z{sub eff} of breast tissues, which are related to the content of carbon (Z=6) and oxygen (Z=8) in each tissue type. The results suggest that is possible to use this parameter for characterizing breast tissues, pointing the possibility of its use as a complementary tool for the diagnosis of the breast cancer. (author)

Individual Tracer Atoms in an Ultracold Dilute Gas

Science.gov (United States)

Hohmann, Michael; Kindermann, Farina; Lausch, Tobias; Mayer, Daniel; Schmidt, Felix; Lutz, Eric; Widera, Artur

2017-06-01

We report on the experimental investigation of individual Cs atoms impinging on a dilute cloud of ultracold Rb atoms with variable density. We study the relaxation of the initial nonthermal state and detect the effect of single collisions which has so far eluded observation. We show that, after few collisions, the measured spatial distribution of the tracer atoms is correctly described by a Langevin equation with a velocity-dependent friction coefficient, over a large range of Knudsen numbers. Our results extend the simple and effective Langevin treatment to the realm of light particles in dilute gases. The experimental technique developed opens up the microscopic exploration of a novel regime of diffusion at the level of individual collisions.

Wavefunction effects in inner shell ionization of light atoms by protons

International Nuclear Information System (INIS)

Aashamar, K.; Amundsen, P.A.

An efficient computer code for calculating the impact parameter distribution of atomic ionization probabilities caused by charged particle impact, has been developed. The programme is based on the semiclassical approximation, and it allows the use of an arbitrary atomic central potential for deriving the one-electron orbitals that form the basis for the description of the atomic states. Extensive calculations are reported for proton induced K-shell ionization in carbon and neon, covering energies in the range 0.1-10 MeV. Some calculations on proton-argon L-shell ionization are also reported. Comparison of the results obtained using (screened) hydrogenic potentials and the recently reported energy- optimized effective atomic central potentials, respectively demonstrates that wavefunction effects are generally important for inner-shell ionization of light atoms. The agreement between theory and experiment in the K-shell case is improved for fast collisions upon using better wavefunctions. (Auth.)

Enhancing optical nonreciprocity by an atomic ensemble in two coupled cavities

Science.gov (United States)

Song, L. N.; Wang, Z. H.; Li, Yong

2018-05-01

We study the optical nonreciprocal propagation in an optical molecule of two coupled cavities with one of them interacting with a two-level atomic ensemble. The effect of increasing the number of atoms on the optical isolation ratio of the system is studied. We demonstrate that the significant nonlinearity supplied by the coupling of the atomic ensemble with the cavity leads to the realization of greatly-enhanced optical nonreciprocity compared with the case of single atom.

Proceedings of the NASA workshop on atomic oxygen effects

International Nuclear Information System (INIS)

Brinza, D.E.

1987-06-01

A workshop was held to address the scientific issues concerning the effects of atomic oxygen on materials in the low Earth orbital (LEO) environment. The program included 18 invited speakers plus contributed posters covering topics such as LEO spaceflight experiments, interaction mechanisms, and atomic oxygen source development. Discussion sessions were also held to organize a test program to evaluate atomic oxygen exposure facilities. The key issues raised in the workshop were: (1) the need to develop a reliable predictive model of the effects of long-term exposure of materials to the LEO environment; (2) the ability of ground-based exposure facilities to provide useful data for development of durable materials; and (3) accurate determination of the composition of the LEO environment. These proceedings include the invited papers, the abstracts for the contributed posters, and an account of the test program discussion sessions

Study on the fine control of atoms by coherent interaction

International Nuclear Information System (INIS)

Han, Jae Min; Rho, S. P.; Park, H. M.; Lee, K. S.; Rhee, Y. J.; Yi, J. H.; Jeong, D. Y.; Ko, K. H.; Lee, J. M.; Kim, M.K.

2000-01-01

Study on one dimensional atom cooling and trapping process which is basic to the development of atom manipulation technology has been performed. A Zeeman slower has been designed and manufactured for efficient cooling of atoms. The speed of atoms finally achieved is as slow as 15 m/s with proper cooling conditions. By six circularly-polarized laser beams and quadrupole magnetic field, the atoms which have been slowed down by zeeman slower have been trapped in a small spatial region inside MOT. The higher the intensity of the slowing laser is the more is the number of atoms slowed and the maximum number of atoms trapped has been 10 8 . The atoms of several tens of μK degree have been trapped by controlling the intensity of trapping laser and intensity gradient of magnetic field. EIT phenomena caused by atomic coherent interaction has been studied for the development of atom optical elements. For the investigation of the focusing phenomena induced by the coherent interaction, experimental measurements and theoretical analysis have been performed. Spatial dependency of spectrum and double distribution signal of coupling laser have been obtained. The deflection of laser beams utilizing the EIT effects has also been considered. (author)

Heat conduction in double-walled carbon nanotubes with intertube additional carbon atoms.

Science.gov (United States)

Cui, Liu; Feng, Yanhui; Tan, Peng; Zhang, Xinxin

2015-07-07

Heat conduction of double-walled carbon nanotubes (DWCNTs) with intertube additional carbon atoms was investigated for the first time using a molecular dynamics method. By analyzing the phonon vibrational density of states (VDOS), we revealed that the intertube additional atoms weak the heat conduction along the tube axis. Moreover, the phonon participation ratio (PR) demonstrates that the heat transfer in DWCNTs is dominated by low frequency modes. The added atoms cause the mode weight factor (MWF) of the outer tube to decrease and that of the inner tube to increase, which implies a lower thermal conductivity. The effects of temperature, tube length, and the number and distribution of added atoms were studied. Furthermore, an orthogonal array testing strategy was designed to identify the most important structural factor. It is indicated that the tendencies of thermal conductivity of DWCNTs with added atoms change with temperature and length are similar to bare ones. In addition, thermal conductivity decreases with the increasing number of added atoms, more evidently for atom addition concentrated at some cross-sections rather than uniform addition along the tube length. Simultaneously, the number of added atoms at each cross-section has a considerably more remarkable impact, compared to the tube length and the density of chosen cross-sections to add atoms.

First-Order Quantum Phase Transition for Dicke Model Induced by Atom-Atom Interaction

International Nuclear Information System (INIS)

Zhao Xiu-Qin; Liu Ni; Liang Jiu-Qing

2017-01-01

In this article, we use the spin coherent state transformation and the ground state variational method to theoretically calculate the ground function. In order to consider the influence of the atom-atom interaction on the extended Dicke model’s ground state properties, the mean photon number, the scaled atomic population and the average ground energy are displayed. Using the self-consistent field theory to solve the atom-atom interaction, we discover the system undergoes a first-order quantum phase transition from the normal phase to the superradiant phase, but a famous Dicke-type second-order quantum phase transition without the atom-atom interaction. Meanwhile, the atom-atom interaction makes the phase transition point shift to the lower atom-photon collective coupling strength. (paper)

Atomic hydrogen reactor

International Nuclear Information System (INIS)

Massip de Turville, C.M.D.

1982-01-01

Methods are discussed of generating heat in an atomic hydrogen reactor which involve; the production of atomic hydrogen by an electrical discharge, the capture of nascent neutrons from atomic hydrogen in a number of surrounding steel alloy tubes having a high manganese content to produce 56 Mn, the irradiation of atomic hydrogen by the high energy antineutrinos from the beta decay of 56 Mn to yield nascent neutrons, and the removal of the heat generated by the capture of nascent neutrons by 55 Mn and the beta decay of 56 Mn. (U.K.)

Mechanical torques generated by optically pumped atomic spin relaxation at surfaces

International Nuclear Information System (INIS)

Herman, R.M.

1982-01-01

It is argued that a valuable method of observing certain types of surface-atom interactions may lie in mechanical torques generated through the spin-orbit relaxation of valence electronic spins of optically pumped atoms at surfaces. The unusual feature of this phenomenon is that the less probable spin-orbit relaxation becomes highly visible as compared with the much more rapid paramagnetic relaxation, because of an enhancement, typically by as much as a factor 10 9 , in the torques delivered to mechanical structures, by virtue of a very large effective moment arm. Spin-orbit relaxation operates through an exchange of translational momentum which, in turn, can be identified with the delivery of a gigantic angular momentum (in units of h) relative to a distant axis about which mechanical motion is referred. The spin-orbit relaxation strongly depends upon the atomic number of the surface atoms and the strength of interaction with the optically pumped atoms. Being dominated by high-atomic-number surface atoms, spin-orbit relaxation rates may not be too strongly influenced by minor surface contamination of lighter-weight optically active atoms

Mechanical torques generated by optically pumped atomic spin relaxation at surfaces

Science.gov (United States)

Herman, R. M.

1982-03-01

It is argued that a valuable method of observing certain types of surface-atom interactions may lie in mechanical torques generated through the spin-orbit relaxation of valence electronic spins of optically pumped atoms at surfaces. The unusual feature of this phenomenon is that the less probable spin-orbit relaxation becomes highly visible as compared with the much more rapid paramagnetic relaxation, because of an enhancement, typically by as much as a factor 109, in the torques delivered to mechanical structures, by virtue of a very large effective moment arm. Spin-orbit relaxation operates through an exchange of translational momentum which, in turn, can be identified with the delivery of a gigantic angular momentum (in units of ℏ) relative to a distant axis about which mechanical motion is referred. The spin-orbit relaxation strongly depends upon the atomic number of the surface atoms and the strength of interaction with the optically pumped atoms. Being dominated by high-atomic-number surface atoms, spin-orbit-relaxation rates may not be too strongly influenced by minor surface contamination of lighter-weight optically active atoms.

Nuclear electric dipole moment with relativistic effects in Xe and Hg atoms

International Nuclear Information System (INIS)

Oshima, Sachiko; Fujita, Takehisa; Asaga, Tomoko

2007-01-01

The atomic electric dipole moment (EDM) is evaluated by considering the relativistic effects as well as nuclear finite size effects in Xe and Hg atomic systems. Due to Schiff's theorem, the first order perturbation energy of EDM is canceled out by the second order perturbation energy for the point nucleus. The nuclear finite size effects arising from the intermediate atomic excitations may be finite for deformed nucleus but it is extremely small. The finite size contribution of the intermediate nuclear excitations in the second order perturbation energy is completely canceled by the third order perturbation energy. As the results, the finite contribution to the atomic EDM comes from the first order perturbation energy of relativistic effects, and it amounts to around 0.3 and 0.4 percents of the neutron EDM d n for Xe and Hg, respectively, though the calculations are carried out with a simplified single-particle nuclear model. From this relation in Hg atomic system, we can extract the neutron EDM which is found to be just comparable with the direct neutron EDM measurement

Atomic properties in hot plasmas from levels to superconfigurations

CERN Document Server

Bauche, Jacques; Peyrusse, Olivier

2015-01-01

This book is devoted to the calculation of hot-plasma properties which generally requires a huge number of atomic data. It is the first book that combines information on the details of the basic atomic physics and its application to atomic spectroscopy with the use of the relevant statistical approaches. Information like energy levels, radiative rates, collisional and radiative cross-sections, etc., must be included in equilibrium or non-equilibrium models in order to describe both the atomic-population kinetics and the radiative properties. From the very large number of levels and transitions involved in complex ions, some statistical (global) properties emerge. The book presents a coherent set of concepts and compact formulas suitable for tractable and accurate calculations. The topics addressed are: radiative emission and absorption, and a dozen of other collisional and radiative processes; transition arrays between level ensembles (configurations, superconfigurations); effective temperatures of configurat...

Strong coupling effects between a meta-atom and MIM nanocavity

Directory of Open Access Journals (Sweden)

San Chen

2012-09-01

Full Text Available In this paper, we investigate the strong coupling effects between a meta-atom and a metal-insulator-metal (MIM nanocavity. By changing the meta-atom sizes, we achieve the meta-atomic electric dipole, quadrupole or multipole interaction with the plasmonic nanocavity, in which characteristic anticrossing behaviors demonstrate the occurrence of the strong coupling. The various interactions present obviously different splitting values and behaviors of dependence on the meta-atomic position. The largest Rabi-type splittings, about 360.0 meV and 306.1 meV, have been obtained for electric dipole and quadrupole interaction, respectively. We attribute the large splitting to the highly-confined cavity mode and the large transition dipole of the meta-atom. Also the Rabi-type oscillation in time domain is given.

Positronium-alkali atom scattering at medium energies

International Nuclear Information System (INIS)

Chakraborty, Ajoy; Basu, Arindam; Sarkar, Nirmal K; Sinha, Prabal K

2004-01-01

We investigate the scattering of orthopositronium (o-Ps) atom off different atomic alkali targets (Na to Cs) at low and medium energies (up to 120 eV). Projectile-elastic and target-elastic close-coupling models have been employed to investigate the systems in addition to the static-exchange model. Elastic, excitation and total cross sections have been reported for all four systems. The magnitude of the alkali excitation cross section increases with increasing atomic number of the target atom while the position of the peak value shifts towards lower incident energies. The magnitudes of the Ps excitation and ionization cross sections increase steadily with atomic number with no change in the peak position. The reported results show regular behaviour with increasing atomic number of the target atom. Scattering parameters for the Ps-Rb and Ps-Cs systems are being reported for the first time

Theoretical Calculation of Absolute Radii of Atoms and Ions. Part 1. The Atomic Radii

Directory of Open Access Journals (Sweden)

Raka Biswas

2002-02-01

Full Text Available Abstract. A set of theoretical atomic radii corresponding to the principal maximum in the radial distribution function, 4πr2R2 for the outermost orbital has been calculated for the ground state of 103 elements of the periodic table using Slater orbitals. The set of theoretical radii are found to reproduce the periodic law and the Lother Meyer’s atomic volume curve and reproduce the expected vertical and horizontal trend of variation in atomic size in the periodic table. The d-block and f-block contractions are distinct in the calculated sizes. The computed sizes qualitatively correlate with the absolute size dependent properties like ionization potentials and electronegativity of elements. The radii are used to calculate a number of size dependent periodic physical properties of isolated atoms viz., the diamagnetic part of the atomic susceptibility, atomic polarizability and the chemical hardness. The calculated global hardness and atomic polarizability of a number of atoms are found to be close to the available experimental values and the profiles of the physical properties computed in terms of the theoretical atomic radii exhibit their inherent periodicity. A simple method of computing the absolute size of atoms has been explored and a large body of known material has been brought together to reveal how many different properties correlate with atomic size.

Quantum chaos in atom optics

International Nuclear Information System (INIS)

D'Arcy, Michael Brendan

2002-01-01

This thesis presents an account of experimental and numerical investigations of two quantum systems whose respective classical analogues are chaotic. These are the δ-kicked rotor, a paradigm in classical chaos theory, and the novel δ-kicked accelerator, created by application of a constant external acceleration or torque to the rotor. The experimental realisation of these systems has been achieved by the exposure of laser-cooled caesium atoms to approximate δ-kicks from a pulsed, high-intensity, vertical standing wave of laser light. Gravity's effect on the atoms can be controlled by appropriate shifting of the profile of the standing wave. Numerical simulations of the systems are based on a diffractive model of the potential's effect. Each system's dynamics are characterised by the final form of the momentum distribution and the dependence of the atoms' mean kinetic energy on the number and time period of the δ-kicks. The phenomena of dynamical localisation and quantum resonances in the δ-kicked rotor, which have no counterparts in the system's classical analogue, are observed and investigated. Similar experiments on the δ-kicked accelerator reveal the striking phenomenon of the quantum accelerator mode, in which a large momentum is transferred to a substantial fraction of the atomic ensemble. This feature, absent in the system's classical analogue, is characterised and an analytic explanation is presented. The effect on each quantum system of decoherence, introduced through spontaneous emission in the atoms, is examined and comparison is made with the results of classical simulations. While having little effect on the classical systems, the level of decoherence used is found to degrade quantum signatures of behaviour. Classical-like behaviour is, to some extent, restored, although significant quantum features remain. Possible applications of the quantum accelerator mode are discussed. These include use as a tool in atom optics and interferometry, a

Representation-free description of light-pulse atom interferometry including non-inertial effects

Energy Technology Data Exchange (ETDEWEB)

Kleinert, Stephan, E-mail: stephan.kleinert@uni-ulm.de [Institut für Quantenphysik and Center for Integrated Quantum Science and Technology (IQST), Universität Ulm, Albert-Einstein-Allee 11, D-89081 Ulm (Germany); Kajari, Endre; Roura, Albert [Institut für Quantenphysik and Center for Integrated Quantum Science and Technology (IQST), Universität Ulm, Albert-Einstein-Allee 11, D-89081 Ulm (Germany); Schleich, Wolfgang P. [Institut für Quantenphysik and Center for Integrated Quantum Science and Technology (IQST), Universität Ulm, Albert-Einstein-Allee 11, D-89081 Ulm (Germany); Texas A& M University Institute for Advanced Study (TIAS), Institute for Quantum Science and Engineering (IQSE) and Department of Physics and Astronomy, Texas A& M University College Station, TX 77843-4242 (United States)

2015-12-30

Light-pulse atom interferometers rely on the wave nature of matter and its manipulation with coherent laser pulses. They are used for precise gravimetry and inertial sensing as well as for accurate measurements of fundamental constants. Reaching higher precision requires longer interferometer times which are naturally encountered in microgravity environments such as drop-tower facilities, sounding rockets and dedicated satellite missions aiming at fundamental quantum physics in space. In all those cases, it is necessary to consider arbitrary trajectories and varying orientations of the interferometer set-up in non-inertial frames of reference. Here we provide a versatile representation-free description of atom interferometry entirely based on operator algebra to address this general situation. We show how to analytically determine the phase shift as well as the visibility of interferometers with an arbitrary number of pulses including the effects of local gravitational accelerations, gravity gradients, the rotation of the lasers and non-inertial frames of reference. Our method conveniently unifies previous results and facilitates the investigation of novel interferometer geometries.

A correlation between isomer shifts of 237Np Moessbauer spectra and coordination numbers of Np atoms in neptunyl(V) compounds

International Nuclear Information System (INIS)

Saeki, M.; Nakada, M.; Nakamoto, T.; Yamashita, T.; Masaki, N.M.; Krot, N.N.

1999-01-01

Five neptunyl(V) compounds were synthesized and studied by 237 Np Moessbauer spectroscopy. The isomer shifts (δ) of the Moessbauer spectra ranged from -18.6 to -19.1 mm/s for the compounds with Np atoms surrounded by 7 oxygen atoms (coordination number (CN) 7). On the other hand, the larger value of δ was obtained for the compound with CN 8. From the comparison of the present results with those reported on neptunyl(V) and (VI) compounds, it is concluded that there is a correlation between the δ and the CN for neptunyl(V) compounds, and the distribution of δ is narrower for neptunyl(V) compounds than that of neptunyl(VI) compounds. (author)

Ozone depletion, greenhouse effect and atomic energy

International Nuclear Information System (INIS)

Adzersen, K.H.

1991-01-01

After describing the causes and effects of ozone depletion and the greenhouse effect, the author discusses the alternative offered by the nuclear industry. In his opinion, a worldwide energy strategy of risk minimisation will not be possible unless efficient energy use is introduced immediately, efficiently and on a reliable basis. Atomic energy is not viewed as an acceptable means of preventing the threatening climate change. (DG) [de

Stability investigation of a high number density Pt1/Fe2O3 single-atom catalyst under different gas environments by HAADF-STEM

Science.gov (United States)

Duan, Sibin; Wang, Rongming; Liu, Jingyue

2018-05-01

Catalysis by supported single metal atoms has demonstrated tremendous potential for practical applications due to their unique catalytic properties. Unless they are strongly anchored to the support surfaces, supported single atoms, however, are thermodynamically unstable, which poses a major obstacle for broad applications of single-atom catalysts (SACs). In order to develop strategies to improve the stability of SACs, we need to understand the intrinsic nature of the sintering processes of supported single metal atoms, especially under various gas environments that are relevant to important catalytic reactions. We report on the synthesis of high number density Pt1/Fe2O3 SACs using a facial strong adsorption method and the study of the mobility of these supported Pt single atoms at 250 °C under various gas environments that are relevant to CO oxidation, water–gas shift, and hydrogenation reactions. Under the oxidative gas environment, Fe2O3 supported Pt single atoms are stable even at high temperatures. The presence of either CO or H2 molecules in the gas environment, however, facilitates the movement of the Pt atoms. The strong interaction between CO and Pt weakens the binding between the Pt atoms and the support, facilitating the movement of the Pt single atoms. The dissociation of H2 molecules on the Pt atoms and their subsequent interaction with the oxygen species of the support surfaces dislodge the surface oxygen anchored Pt atoms, resulting in the formation of Pt clusters. The addition of H2O molecules to the CO or H2 significantly accelerates the sintering of the Fe2O3 supported Pt single atoms. An anchoring-site determined sintering mechanism is further proposed, which is related to the metal–support interaction.

Atomic Number Dependence of Hadron Production at Large Transverse Momentum in 300 GeV Proton--Nucleus Collisions

Science.gov (United States)

Cronin, J. W.; Frisch, H. J.; Shochet, M. J.; Boymond, J. P.; Mermod, R.; Piroue, P. A.; Sumner, R. L.

1974-07-15

In an experiment at the Fermi National Accelerator Laboratory we have compared the production of large transverse momentum hadrons from targets of W, Ti, and Be bombarded by 300 GeV protons. The hadron yields were measured at 90 degrees in the proton-nucleon c.m. system with a magnetic spectrometer equipped with 2 Cerenkov counters and a hadron calorimeter. The production cross-sections have a dependence on the atomic number A that grows with P{sub 1}, eventually leveling off proportional to A{sup 1.1}.

Accelerators for atomic energy research

International Nuclear Information System (INIS)

Shibata, Tokushi

1999-01-01

The research and educational activities accomplished using accelerators for atomic energy research were studied. The studied items are research subjects, facility operation, the number of master theses and doctor theses on atomic energy research using accelerators and the future role of accelerators in atomic energy research. The strategy for promotion of the accelerator facility for atomic energy research is discussed. (author)

Atomic absorption spectrometry using tungsten and molybdenum tubes as metal atomizer

International Nuclear Information System (INIS)

Kaneco, Satoshi; Katsumata, Hideyuki; Ohta, Kiyohisa; Suzuki, Tohru

2007-01-01

We have developed a metal tube atomizer for the electrothermal atomization atomic absorption spectrometry (ETA-AAS). Tungsten, molybdenum, platinum tube atomizers were used as the metal atomizer for ETA-AAS. The atomization characteristics of various metals using these metal tube atomizers were investigated. The effects of heating rate of atomizer, atomization temperature, pyrolysis temperature, argon purge gas flow rate and hydrogen addition on the atomic absorption signal were investigated for the evaluation of atomization characteristics. Moreover, ETA-AAS with metal tube atomizer has been combined with the slurry-sampling techniques. Ultrasonic slurry-sampling ETA-AAS with metal tube atomizer were effective for the determination of trace metal elements in biological materials, calcium drug samples, herbal medicine samples, vegetable samples and fish samples. Furthermore, a preconcentration method of trace metals involving adsorption on a metal wire has been applied to ETA-AAS with metal tube atomizer. (author)

Influence of operating conditions and atomizer design on circumferential liquid distribution from small pressure-swirl atomizer

Directory of Open Access Journals (Sweden)

Malý Milan

2017-01-01

Full Text Available The spray symmetry is an important aspect in most practical applications. However, it is often an overlooked parameter. A measurement of circumferential distribution was carried out by a circular-sectored vessel on several pressure-swirl atomizers with spill-line over a wide range of injection pressure. The obtained results show that the spray uniformity improves markedly with the injection pressure. The increase in a number of tangential entry ports has only a minor effect on the spray uniformity. Even a small mechanical corruption of the atomizer internal parts negatively affects the spray patternation.

Curious behavior of optically trapped neutral atoms

International Nuclear Information System (INIS)

Wieman, C.; Walker, T.; Sesko, D.; Monroe, C.

1991-01-01

We have studied the behavior of clouds of neutral atoms contained in a spontaneous force optical trap. Because of the low temperatures of the atoms ( 5 atoms. These include the expansion of the cloud as the number is increased and dramatic changes in the distribution of the atoms at higher numbers. We can explain much of the collective behavior using a simple model that includes a 1/r 2 force between the atoms arising from the multiple scattering of photons. Finally, we discuss the optical trapping of atoms directly from a low pressure vapor in a small glass cell. We have used these optically trapped atoms to load a magnetostatic trap in the same cell. This provided a high density sample of atoms with a temperature of less than 2 μK

Matrix effect on hydrogen-atom tunneling of organic molecules in cryogenic solids

International Nuclear Information System (INIS)

Ichikawa, Tsuneki

2000-01-01

tunneling of hydrogen atoms. Since the tunneling rate depends not on the peak height of the potential barrier but on the area of the barrier, the restriction of molecular motion by rigid matrices causes the retardation of the hydrogen-atom tunneling. The steric hindrance increases with increasing number and length of alkyl chains attached to a carbon atom to be hydrogen-abstracted. The Penultimate secondary carbon therefore shows the highest reaction rate. (author)

Effect of inelastic energy losses on development of atom-atom collision cascades

International Nuclear Information System (INIS)

Marinyuk, V.V.; Remizovich, V.S.

2001-01-01

The problem of influence of inelastic energy losses (ionization braking) of particles on the development of atom-atom collision cascades in infinite medium was studied theoretically. Main attention was paid to study of angular and energy distributions of primary ions and cascade atoms in the presence of braking. Analytical calculations were made in the assumption that single scattering of particles occurs by solid balls law, while the value of electron braking ability of a medium is determined by the Lindhard formula. It is shown that account of braking (directly when solving the Boltzmann transport equation) changes in principle the previously obtained angular and energy spectra of ions and cascade atoms. Moreover, it is the braking that is the determining factor responsible for anisotropy of angular distributions of low-energy primary ions and cascade atoms [ru

An Estimation of the Number and Size of Atoms in a Printed Period

Science.gov (United States)

Schaefer, Beth; Collett, Edward; Tabor-Morris, Anne; Croman, Joseph

2011-01-01

Elementary school students learn that atoms are very, very small. Students are also taught that atoms (and molecules) are the fundamental constituents of the material world. Numerical values of their size are often given, but, nevertheless, it is difficult to imagine their size relative to one's everyday surroundings. In order for students to…

Nonclassical Effects of a Four-Level Excited-Doublet Atom Model

International Nuclear Information System (INIS)

Zhang Jiansong; Xu Jingbo

2006-01-01

We adopt a dynamical algebraic method to study a four-level excited-doublet atom model and obtain the explicit expressions of the time-evolution operator and the density operator for the system. The nonclassical effects of the system, such as collapses and revivals of the atomic inversion and squeezing of the radiation field, are also discussed.

Influence of average ion energy and atomic oxygen flux per Si atom on the formation of silicon oxide permeation barrier coatings on PET

Science.gov (United States)

Mitschker, F.; Wißing, J.; Hoppe, Ch; de los Arcos, T.; Grundmeier, G.; Awakowicz, P.

2018-04-01

The respective effect of average incorporated ion energy and impinging atomic oxygen flux on the deposition of silicon oxide (SiO x ) barrier coatings for polymers is studied in a microwave driven low pressure discharge with additional variable RF bias. Under consideration of plasma parameters, bias voltage, film density, chemical composition and particle fluxes, both are determined relative to the effective flux of Si atoms contributing to film growth. Subsequently, a correlation with barrier performance and chemical structure is achieved by measuring the oxygen transmission rate (OTR) and by performing x-ray photoelectron spectroscopy. It is observed that an increase in incorporated energy to 160 eV per deposited Si atom result in an enhanced cross-linking of the SiO x network and, therefore, an improved barrier performance by almost two orders of magnitude. Furthermore, independently increasing the number of oxygen atoms to 10 500 per deposited Si atom also lead to a comparable barrier improvement by an enhanced cross-linking.

Effective atomic number, energy loss and radiation damage studies in some materials commonly used in nuclear applications for heavy charged particles such as H, C, Mg, Fe, Te, Pb and U

Science.gov (United States)

Kurudirek, Murat

2016-05-01

Commonly used nuclear physics materials such as water, concrete, Pb-glass, paraffin, freon and P 10 gases, some alloys such as brass, bronze, stainless-steel and some scintillators such as anthracene, stilbene and toluene have been investigated with respect to the heavy charged particle interaction as means of projected range and effective atomic number (Zeff) in the energy region 10 keV to 10 MeV. Calculations were performed for heavy ions such as H, C, Mg, Fe, Te, Pb and U. Also, the energy loss and radiation damage were studied using SRIM Monte Carlo code for anthracene for different heavy ions of 100 keV kinetic energy. It has been observed that the variation in Zeff becomes less when the atomic number of the ions increase. Glass-Pb, bronze, brass, stainless-steel and Freon gas were found to vary less than 10% in the energy region 10 keV to 10 MeV. For total proton interaction, discrepancies up to 10% and 18% between two databases namely PSTAR and SRIM were noted in mass stopping power and Zeff of water, respectively. The range calculations resulted with a conclusion that the metal alloys and glass-Pb have lowest values of ranges confirming best shielding against energetic heavy ions whereas freon and P 10 gases have the highest values of ranges in the entire energy region. The simulation results showed that the energy loss (%) to target electrons decreases as the Z of the incident ion increases. Also, it was observed that the radiation damage first increases with Z of the ion and then keeps almost constant for ions with Z≥52.

Atomic Parity Violation Overview and Perspectives

CERN Document Server

CERN. Geneva. Audiovisual Unit

2002-01-01

Optical experiments have demonstrated cases in which mirror symmetry in stable atoms is broken during absorption or emission of light. Such results are in conflict with standard electromagnetic (EM) theory, but can be explained within the unified electroweak theory. Their interpretation is based on exchanges of virtual weak neutral Z_0 bosons between the electrons and the atomic nucleus. These effects were predicted to increase in heavy atoms a little faster than the cube of the atomic number. Moreover, in a highly forbidden transition, like the 6S-7S transition in cesium, the EM interaction is suppressed, leaving the Z_0 exchange a chance to show up. For achieving the determination of the Cs nucleus weak charge, Q_W(Cs), the basic experimental parameter playing in Z_0, exchange the same role as the nuclear charge in the Coulomb interaction, both experimental and theoretical hurdles had to be overcome: first, the excitation and detection of an atomic line with a transition rate about 10^{14} times less than a...

Teleportation of atomic states with a weak coherent cavity field

Institute of Scientific and Technical Information of China (English)

Zheng Shi-Biao

2005-01-01

A scheme is proposed for the teleportation of an unknown atomic state. The scheme is based on the resonant interaction of atoms with a coherent cavity field. The mean photon-number of the cavity field is much smaller than one and thus the cavity decay can be effectively suppressed. Another adwntage of the scheme is that only one cavity is required.

Light pionic atoms perspectives for precision experiments

International Nuclear Information System (INIS)

Gotta, D.

2005-01-01

During the last decades high-precision spectroscopy of exotic-atom x-rays profited in particular in the case of pions from the increasing number of stopped particles provided by the cyclotron trap at the accelerator facility of the Paul-Scherrer-Institut (PSI) together with modern detector concepts like charge-coupled devices (CCDs) and crystal spectrometers. Presently, priority is given to the study of the strong-interaction effects in the most elementary system - pionic hydrogen. However, the systems with two or more nucleons are as fundamental for the development of a theoretical description of hadronic matter. Furthermore, the de-excitation of exotic atoms involves a variety of atomic processes, which become accessible in detail due to the high resolution achievable with crystal spectrometers, e. g., parallel transitions, line splittings, broadenings and intensity distributions. In addition, first successful attempts for a microscopic description of the atomic cascade are available now, which should be subject to stringent tests both for atoms and molecules. (author)

Atomic mean-square displacements and the critical-voltage effect in cubic solid solutions

International Nuclear Information System (INIS)

Shirley, C.G.; Fisher, R.M.

1979-01-01

The critical-voltage phenomena observed in high-voltage electron microscope images of bend contours as well as in corresponding Kikuchi or convergent-beam diffraction patterns provide sensitive methods of determining submicroscopic alloy parameters such as Debye temperatures, short-range order, and atomic scattering factors. Only a very limited number of critical voltages can be observed in metal crystals in the voltage range usually available, 100 to 1200 kV, so that quantitative interpretation of the data must be based on a few-parameter model which incorporates all the pertinent factors. A satisfactory two-parameter model has been developed which can be used to interpret or compute the critical voltages of substitutional solid solutions as functions of composition, temperature and short-range order. In the alloy systems Fe-Cr, Ni-Au, Cu-Au and Cu-Al, sufficient critical voltage data are available to derive the model parameters which pertain to atomic bonding in the lattice. In addition to atomic scattering amplitudes, the critical voltage depends strongly on the atomic mean-square displacements. The static contribution to the mean-square displacements is large in alloys with large atomic-radius disparity, and is especially sensitive to short-range order in f.c.c. solid solutions. Well-defined best estimates for the model parameters are used to predict the critical voltage and its sensitivity to composition, temperature and short-range order for a large number of solid solutions. Systems for which critical-voltage studies may be of considerable interest are indicated. (author)

Does the number of nitrogen atoms have an influence on the conducting properties of diphenylazines? A DFT insight

Science.gov (United States)

Moral, Mónica; Granadino-Roldán, José Manuel; Garzón, Andrés; García, Gregorio; Fernández-Gómez, Manuel

2011-01-01

The present study reports on the variation of some structural and electronic properties related to the electron conductivity for the series of diphenylazines represented by the formula Ph sbnd (C 2+nN 4-nH n) sbnd Ph, n = 0 - 4. Properties such as planarity, aromaticity, HOMO → LUMO excitation energy, electron affinity, LUMO level energy, reorganization energy and electron coupling between neighboring molecules in the crystal were analyzed from a theoretical perspective as a function of the number of nitrogen atoms in the molecular structure. As a result, the planarity, aromaticity and electron affinity increase with the number of N atoms in the central ring while the HOMO → LUMO excitation energy and LUMO levels diminish. It is worth noting that up to n = 3, the frontier orbitals appear delocalized throughout the whole system while for n = 4 the localized character of the LUMO might explain the increase in the reorganization energy and thus the higher difficulty to delocalize the excess of negative charge. Electron coupling between neighboring molecules was also estimated on the basis of the energy splitting in dimer method and the reported crystal structures for some of the studied molecules. Accordingly, the highest | t12| value was obtained for Ph 2T N3 (0.06 eV) while Ph 2Tz should be the most advantageous candidate of the series in terms of electron injection.

Experimental physics. Vol. 5. Quanta, atoms, nuclei, particles; Experimentalphysik. Bd. 5. Quanten, Atome, Kerne, Teilchen

Energy Technology Data Exchange (ETDEWEB)

Pfeiler, Wolfgang [Wien Univ. (Austria). Fakultaet fuer Physik

2017-07-01

The following topics are dealt with: Photo- and Compton effect, photon, particle as wave, de Broglie wavelength, self-interference, dispersion relation, wavepacket, probability interpretation, uncertainty relations, occupation inversion, laser condition, tunnel effect, harmonic oscillator, hydrogen atom, quantum numbers, energy levels, electron spin, fine structure, Zeeman effect, periodic system, nuclear properties, binding energy, nuclear magnetism, nuclear models, radioactive decay, nuclear reactions, nuclear fission, nuclear energy, nuclear fusion, dosimetry, elementary particles, conservation laws, quark model, standard model, cosmology (Hubble law, cosmic background radiation, darkmatter, critical mass density, cosmological standard model), Moessbauer effect.

Atom-atom collision cascades localization

International Nuclear Information System (INIS)

Kirsanov, V.V.

1980-01-01

The presence of an impurity and thermal vibration influence on the atom-atom collision cascade development is analysed by the computer simulation method (the modificated dynamic model). It is discovered that the relatively low energetic cascades are localized with the temperature increase of an irradiated crystal. On the basis of the given effect the mechanism of splitting of the high energetic cascades into subcascades is proposed. It accounts for two factors: the primary knocked atom energy and the irradiated crystal temperature. Introduction of an impurity also localizes the cascades independently from the impurity atom mass. The cascades localization leads to intensification of the process of annealing in the cascades and reduction of the post-cascade vacancy cluster sizes. (author)

The Effect of Vibration Characteristics on the Atomization Rate in a Micro-Tapered Aperture Atomizer

Directory of Open Access Journals (Sweden)

Qiufeng Yan

2018-03-01

Full Text Available Because little is known about the atomization theory of a micro-tapered aperture atomizer, we investigated the vibration characteristics of this type of atomizer. The atomization mechanism of a micro-tapered aperture atomizer was described, and the atomization rate equation was deduced. As observed via microscopy, the angle of the micro-tapered aperture changes with the applied voltage, which proved the existence of a dynamic cone angle. The forward and reverse atomization rates were measured at various voltages, and the influence of the micro-tapered aperture and its variation on the atomization rate was characterized. The resonance frequency of the piezoelectric vibrator was obtained using a laser vibrometer, and the atomization rates were measured at each resonance frequency. From experiments, we found that the atomization rates at the first five resonance frequencies increased as the working frequency increased. At the fifth resonance frequency (121.1 kHz, the atomization rate was maximized (0.561 mL/min, and at the sixth resonance frequency (148.3 kHz, the atomization rate decreased significantly (0.198 mL/min. The experimental results show that the vibration characteristics of the piezoelectric vibrator have a relatively strong impact on the atomization rate. This research is expected to contribute to the manufacture of micro-tapered aperture atomizers.

The Effect of Vibration Characteristics on the Atomization Rate in a Micro-Tapered Aperture Atomizer.

Science.gov (United States)

Yan, Qiufeng; Zhang, Jianhui; Huang, Jun; Wang, Ying

2018-03-21

Because little is known about the atomization theory of a micro-tapered aperture atomizer, we investigated the vibration characteristics of this type of atomizer. The atomization mechanism of a micro-tapered aperture atomizer was described, and the atomization rate equation was deduced. As observed via microscopy, the angle of the micro-tapered aperture changes with the applied voltage, which proved the existence of a dynamic cone angle. The forward and reverse atomization rates were measured at various voltages, and the influence of the micro-tapered aperture and its variation on the atomization rate was characterized. The resonance frequency of the piezoelectric vibrator was obtained using a laser vibrometer, and the atomization rates were measured at each resonance frequency. From experiments, we found that the atomization rates at the first five resonance frequencies increased as the working frequency increased. At the fifth resonance frequency (121.1 kHz), the atomization rate was maximized (0.561 mL/min), and at the sixth resonance frequency (148.3 kHz), the atomization rate decreased significantly (0.198 mL/min). The experimental results show that the vibration characteristics of the piezoelectric vibrator have a relatively strong impact on the atomization rate. This research is expected to contribute to the manufacture of micro-tapered aperture atomizers.

Measurement of mass attenuation coefficients of moderate-to-high atomic-number elements at low photon energies

International Nuclear Information System (INIS)

Tajuddin, A.A.; Chong, C.S.; Shukri, A.; Bradley, D.A.

1995-01-01

Mass attenuation coefficients for 12 selected moderate-to-high atomic-number elements have been obtained from good-geometry measurements made at five 241 Am photon energies of significant emission intensity. Particular interest focuses on measured values for photon energies close to absorption edges. Comparisons with renormalized cross-section predictions indicate agreement to within stated error limits for the majority of cases. Significant discrepancies (> 10%) are noted for Ta at 17.8 and 26.3 keV and W at 59.5 keV. Some support for a discrepancy between measurement and theory for W in the region of 60 keV is found in the reported measurements of others. (author)

Strong enhancement of Penning ionization for asymmetric atom pairs in cold Rydberg gases: the Tom and Jerry effect

KAUST Repository

Efimov, D K

2016-05-18

We consider Penning ionization of Rydberg atom pairs as an Auger-type process induced by the dipole-dipole interaction and employ semiclassical formulae for dipole transitions to calculate the autoionization width as a function of the principal quantum numbers, n d, n i, of both atoms. While for symmetric atom pairs with the well-known increase of the autoionization width with increasing n 0 is obtained, the result for asymmetric pairs is counterintuitive - for a fixed n i of the ionizing atom of the pair, the autoionization width strongly increases with decreasing n d of the de-excited atom. For H Rydberg atoms this increase reaches two orders of magnitude at the maximum of the n d dependence, and the same type of counterintuitive behavior is exhibited also by Na, Rb and Cs atoms. This is a purely quantum-mechanical effect, which points towards existence of optimal (we call them \\'Tom\\' and \\'Jerry\\' for \\'big\\' and \\'small\\') pairs of Rydberg atoms with respect to autoionization efficiency. Building on the model of population redistribution in cold Rydberg gases proposed in [1], we demonstrate that population evolution following the initial laser excitation of Rydberg atoms in state n 0 would eventually lead to the formation of such Tom-Jerry pairs with which feature autoionization widths that are enhanced by several orders of magnitude compared to that of two atoms in the initial laser-excited state n 0. We also show that in the high-density regime of cold Rydberg gas experiments the ionization rate of Tom-Jerry pairs can be substantially larger than the blackbody radiation-induced photoionization rate. © 2016 IOP Publishing Ltd.

The Effect of Vibration Characteristics on the Atomization Rate in a Micro-Tapered Aperture Atomizer

OpenAIRE

Qiufeng Yan; Jianhui Zhang; Jun Huang; Ying Wang

2018-01-01

Because little is known about the atomization theory of a micro-tapered aperture atomizer, we investigated the vibration characteristics of this type of atomizer. The atomization mechanism of a micro-tapered aperture atomizer was described, and the atomization rate equation was deduced. As observed via microscopy, the angle of the micro-tapered aperture changes with the applied voltage, which proved the existence of a dynamic cone angle. The forward and reverse atomization rates were measured...

Preparation of Ultracold Atom Clouds at the Shot Noise Level

DEFF Research Database (Denmark)

Gajdacz, M.; Hilliard, A. J.; Kristensen, Mick

2016-01-01

We prepare number stabilized ultracold atom clouds through the real-time analysis of nondestructive images and the application of feedback. In our experiments, the atom number N∼10^6 is determined by high precision Faraday imaging with uncertainty ΔN below the shot noise level, i.e., ΔN... on this measurement, feedback is applied to reduce the atom number to a user-defined target, whereupon a second imaging series probes the number stabilized cloud. By this method, we show that the atom number in ultracold clouds can be prepared below the shot noise level....

Effect of heavy atoms on photochemically induced dynamic nuclear polarization in liquids

Science.gov (United States)

Okuno, Yusuke; Cavagnero, Silvia

2018-01-01

Given its short hyperpolarization time (∼10-6 s) and mostly non-perturbative nature, photo-chemically induced dynamic nuclear polarization (photo-CIDNP) is a powerful tool for sensitivity enhancement in nuclear magnetic resonance. In this study, we explore the extent of 1H-detected 13C nuclear hyperpolarization that can be gained via photo-CIDNP in the presence of small-molecule additives containing a heavy atom. The underlying rationale for this methodology is the well-known external-heavy-atom (EHA) effect, which leads to significant enhancements in the intersystem-crossing rate of selected photosensitizer dyes from photoexcited singlet to triplet. We exploited the EHA effect upon addition of moderate amounts of halogen-atom-containing cosolutes. The resulting increase in the transient triplet-state population of the photo-CIDNP sensitizer fluorescein resulted in a significant increase in the nuclear hyperpolarization achievable via photo-CIDNP in liquids. We also explored the internal-heavy-atom (IHA) effect, which is mediated by halogen atoms covalently incorporated into the photosensitizer dye. Widely different outcomes were achieved in the case of EHA and IHA, with EHA being largely preferable in terms of net hyperpolarization.

Systematic measurements of opacity dependence on temperature, density, and atomic number at stellar interior conditions

Science.gov (United States)

Nagayama, Taisuke

2017-10-01

Model predictions for iron opacity are notably different from measurements performed at matter conditions similar to the boundary between the solar radiation and convection zones. The calculated iron opacities have narrower spectral lines, weaker quasi-continuum at short wavelength, and deeper opacity windows than the measurements. If correct, these measurements help resolve a decade old problem in solar physics. A key question is therefore: What is responsible for the model-data discrepancy? The answer is complex because the experiments are challenging and opacity theories depend on multiple entangled physical processes such as the influence of completeness and accuracy of atomic states, line broadening, contributions from myriad transitions from excited states, and multi-photon absorption processes. To help determine the cause of this discrepancy, a systematic study of opacity variation with temperature, density, and atomic number is underway. Measurements of chromium, iron, and nickel opacities have been performed at two different temperatures and densities. The collection of measured opacities provides constraints on hypotheses to explain the discrepancy. We will discuss implications of measured opacities, experimental errors, and possible opacity model refinements. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-NA0003525.

The effect of atoms excited by electron beam on metal evaporation

CERN Document Server

Xie Guo Feng; Ying Chun Tong

2002-01-01

In atomic vapor laser isotope separation (AVLIS), the metal is heated to melt by electron beams. The vapor atoms may be excited by electrons when flying through the electron beam. The excited atoms may be deexcited by inelastic collision during expansion. The electronic energy transfers translational energy. In order to analyse the effect of reaction between atoms and electron beams on vapor physical parameters, such as density, velocity and temperature, direct-simulation Monte Carlo method (DSMC) is used to simulate the 2-D gadolinium evaporation from long and narrow crucible. The simulation results show that the velocity and temperature of vapor increase, and the density decreases

Interference effects on the photoionization cross sections between two neighbouring atoms: nitrogen as an example

International Nuclear Information System (INIS)

Jian-Hua, Wu; Jian-Min, Yuan

2009-01-01

Interference effects on the photoionization cross sections between two neighbouring atoms are considered based on the coherent scattering of the ionized electrons by the two nuclei when their separation is less than or comparable to the de Broglie wave length of the ionized electrons. As an example, the single atomic nitrogen ionization cross section and the total cross sections of two nitrogen atoms with coherently added photoionization amplitudes are calculated from the threshold to about 60 Å (1 Å = 0.1 nm) of the photon energy. The photoionization cross sections of atomic nitrogen are obtained by using the close-coupling R-matrix method. In the calculation 19 states are included. The ionization energy of the atomic nitrogen and the photoionization cross sections agree well with the experimental results. Based on the R-matrix results of atomic nitrogen, the interference effects between two neighbouring nitrogen atoms are obtained. It is shown that the interference effects are considerable when electrons are ionized just above the threshold, even for the separations between the two atoms are larger than two times of the bond length of N 2 molecules. Therefore, in hot and dense samples, effects caused by the coherent interference between the neighbours are expected to be observable for the total photoionization cross sections. (atomic and molecular physics)

Energy Dependence of Measured CT Numbers on Substituted Materials Used for CT Number Calibration of Radiotherapy Treatment Planning Systems.

Directory of Open Access Journals (Sweden)

Reza Mahmoudi

Full Text Available For accurate dose calculations, it is necessary to provide a correct relationship between the CT numbers and electron density in radiotherapy treatment planning systems (TPSs. The purpose of this study was to investigate the energy dependence of measured CT numbers on substituted materials used for CT number calibration of radiotherapy TPSs and the resulting errors in the treatment planning calculation doses.In this study, we designed a cylindrical water phantom with different materials used as tissue equivalent materials for the simulation of tissues and obtaining the related CT numbers. For evaluating the effect of CT number variations of substituted materials due to energy changing of scanner (kVp on the dose calculation of TPS, the slices of the scanned phantom at three kVp's were imported into the desired TPSs (MIRS and CorePLAN. Dose calculations were performed on two TPSs.The mean absolute percentage differences between the CT numbers of CT scanner and two treatment planning systems for all the samples were 3.22%±2.57% for CorePLAN and 2.88%±2.11% for MIRS. It was also found that the maximum absolute percentage difference between all of the calculated doses from each photon beam of linac (6 and 15 MV at three kVp's was less than 1.2%.The present study revealed that, for the materials with effective low atomic number, the mean CT number increased with increasing energy, which was opposite for the materials with an effective high atomic number. We concluded that the tissue substitute materials had a different behavior in the energy ranges from 80 to 130 kVp. So, it is necessary to consider the energy dependence of the substitute materials used for the measurement or calibration of CT number for radiotherapy treatment planning systems.

Number-unconstrained quantum sensing

Science.gov (United States)

Mitchell, Morgan W.

2017-12-01

Quantum sensing is commonly described as a constrained optimization problem: maximize the information gained about an unknown quantity using a limited number of particles. Important sensors including gravitational wave interferometers and some atomic sensors do not appear to fit this description, because there is no external constraint on particle number. Here, we develop the theory of particle-number-unconstrained quantum sensing, and describe how optimal particle numbers emerge from the competition of particle-environment and particle-particle interactions. We apply the theory to optical probing of an atomic medium modeled as a resonant, saturable absorber, and observe the emergence of well-defined finite optima without external constraints. The results contradict some expectations from number-constrained quantum sensing and show that probing with squeezed beams can give a large sensitivity advantage over classical strategies when each is optimized for particle number.

Atomic inner-shell physics

International Nuclear Information System (INIS)

Crasemann, B.

1985-01-01

This book discusses: relativistic and quantum electrodynamic effects on atomic inner shells; relativistic calculation of atomic transition probabilities; many-body effects in energetic atomic transitions; Auger Electron spectrometry of core levels of atoms; experimental evaluation of inner-vacancy level energies for comparison with theory; mechanisms for energy shifts of atomic K-X rays; atomic physics research with synchrotron radiation; investigations of inner-shell states by the electron energy-loss technique at high resolution; coherence effects in electron emission by atoms; inelastic X-ray scattering including resonance phenomena; Rayleigh scattering: elastic photon scattering by bound electrons; electron-atom bremsstrahlung; X-ray and bremsstrahlung production in nuclear reactions; positron production in heavy-ion collisions, and X-ray processes in heavy-ion collisions

The Belgian repository of fundamental atomic data and stellar spectra (BRASS). I. Cross-matching atomic databases of astrophysical interest

Science.gov (United States)

Laverick, M.; Lobel, A.; Merle, T.; Royer, P.; Martayan, C.; David, M.; Hensberge, H.; Thienpont, E.

2018-04-01

Context. Fundamental atomic parameters, such as oscillator strengths, play a key role in modelling and understanding the chemical composition of stars in the Universe. Despite the significant work underway to produce these parameters for many astrophysically important ions, uncertainties in these parameters remain large and can propagate throughout the entire field of astronomy. Aims: The Belgian repository of fundamental atomic data and stellar spectra (BRASS) aims to provide the largest systematic and homogeneous quality assessment of atomic data to date in terms of wavelength, atomic and stellar parameter coverage. To prepare for it, we first compiled multiple literature occurrences of many individual atomic transitions, from several atomic databases of astrophysical interest, and assessed their agreement. In a second step synthetic spectra will be compared against extremely high-quality observed spectra, for a large number of BAFGK spectral type stars, in order to critically evaluate the atomic data of a large number of important stellar lines. Methods: Several atomic repositories were searched and their data retrieved and formatted in a consistent manner. Data entries from all repositories were cross-matched against our initial BRASS atomic line list to find multiple occurrences of the same transition. Where possible we used a new non-parametric cross-match depending only on electronic configurations and total angular momentum values. We also checked for duplicate entries of the same physical transition, within each retrieved repository, using the non-parametric cross-match. Results: We report on the number of cross-matched transitions for each repository and compare their fundamental atomic parameters. We find differences in log(gf) values of up to 2 dex or more. We also find and report that 2% of our line list and Vienna atomic line database retrievals are composed of duplicate transitions. Finally we provide a number of examples of atomic spectral lines

Efficient Atomic One-Qubit Phase Gate Realized by a Cavity QED and Identical Atoms System

International Nuclear Information System (INIS)

He Yong; Jiang Nianquan

2010-01-01

We present a scheme to implement a one-qubit phase gate with a two-level atom crossing an optical cavity in which some identical atoms are trapped. One can conveniently acquire an arbitrary phase shift of the gate by properly choosing the number of atoms trapped in the cavity and the velocity of the atom crossing the cavity. The present scheme provides a very simple and efficient way for implementing one-qubit phase gate. (general)

Resonant atom-field interaction in large-size coupled-cavity arrays

International Nuclear Information System (INIS)

Ciccarello, Francesco

2011-01-01

We consider an array of coupled cavities with staggered intercavity couplings, where each cavity mode interacts with an atom. In contrast to large-size arrays with uniform hopping rates where the atomic dynamics is known to be frozen in the strong-hopping regime, we show that resonant atom-field dynamics with significant energy exchange can occur in the case of staggered hopping rates even in the thermodynamic limit. This effect arises from the joint emergence of an energy gap in the free photonic dispersion relation and a discrete frequency at the gap's center. The latter corresponds to a bound normal mode stemming solely from the finiteness of the array length. Depending on which cavity is excited, either the atomic dynamics is frozen or a Jaynes-Cummings-like energy exchange is triggered between the bound photonic mode and its atomic analog. As these phenomena are effective with any number of cavities, they are prone to be experimentally observed even in small-size arrays.

The A Theory Of Magnitude (ATOM) model in temporal perception and reproduction tasks.

Science.gov (United States)

Fabbri, Marco; Cancellieri, Jennifer; Natale, Vincenzo

2012-01-01

According to the A Theory of Magnitude (ATOM) model, time, numbers and space are processed by a common analog magnitude system. The model proposes that time, numbers and space are influenced by each other. Indeed, spatial-temporal (STEARC effect), spatial-numerical (SNARC effect) and temporal-numerical (TiNARC effect) interactions have been observed. However, the processing of time, numbers and space has not yet been studied within the same experimental procedure. The goal of this study is to test the ATOM model using a procedure in which time, numbers and space are all present. The participants were asked to perform temporal estimation (Experiment 1) and reproduction (Experiment 2) tasks in two different conditions, with either numbers or letters as stimuli. In Experiment 1, significant STEARC, SNARC and TiNARC effects were found in general and when numbers were presented. Moreover, a significant triple interaction between space, time and magnitude was observed, indicating associations between the left key, short duration and small magnitudes, as well as between the right key, long duration and large magnitudes. These results were similar in reaction times and accuracy. In Experiment 2, the results of reproduction times mirrored the previous data but the triple interaction was not found on reproduction times. Considering the temporal accuracy, the STEARC, SNARC and TiNARC effects as well as triple interaction were found. The results seem to partially confirm the ATOM model, even if differences between temporal tasks should be posited. Copyright © 2011 Elsevier B.V. All rights reserved.

Atomic structure in black hole

International Nuclear Information System (INIS)

Nagatani, Yukinori

2006-01-01

We propose that any black hole has atomic structure in its inside and has no horizon as a model of black holes. Our proposal is founded on a mean field approximation of gravity. The structure of our model consists of a (charged) singularity at the center and quantum fluctuations of fields around the singularity, namely, it is quite similar to that of atoms. Any properties of black holes, e.g. entropy, can be explained by the model. The model naturally quantizes black holes. In particular, we find the minimum black hole, whose structure is similar to that of the hydrogen atom and whose Schwarzschild radius is approximately 1.1287 times the Planck length. Our approach is conceptually similar to Bohr's model of the atomic structure, and the concept of the minimum Schwarzschild radius is similar to that of the Bohr radius. The model predicts that black holes carry baryon number, and the baryon number is rapidly violated. This baryon number violation can be used as verification of the model. (author)

Stable atomic hydrogen: Polarized atomic beam source

International Nuclear Information System (INIS)

Niinikoski, T.O.; Penttilae, S.; Rieubland, J.M.; Rijllart, A.

1984-01-01

We have carried out experiments with stable atomic hydrogen with a view to possible applications in polarized targets or polarized atomic beam sources. Recent results from the stabilization apparatus are described. The first stable atomic hydrogen beam source based on the microwave extraction method (which is being tested ) is presented. The effect of the stabilized hydrogen gas density on the properties of the source is discussed. (orig.)

Progress in Visualizing Atomic Size Effects with DFT-Chemical Pressure Analysis: From Isolated Atoms to Trends in AB5 Intermetallics.

Science.gov (United States)

Berns, Veronica M; Engelkemier, Joshua; Guo, Yiming; Kilduff, Brandon J; Fredrickson, Daniel C

2014-08-12

The notion of atomic size poses an important challenge to chemical theory: empirical evidence has long established that atoms have spatial requirements, which are summarized in tables of covalent, ionic, metallic, and van der Waals radii. Considerations based on these radii play a central role in the design and interpretation of experiments, but few methods are available to directly support arguments based on atomic size using electronic structure methods. Recently, we described an approach to elucidating atomic size effects using theoretical calculations: the DFT-Chemical Pressure analysis, which visualizes the local pressures arising in crystal structures from the interactions of atomic size and electronic effects. Using this approach, a variety of structural phenomena in intermetallic phases have already been understood in terms that provide guidance to new synthetic experiments. However, the applicability of the DFT-CP method to the broad range of the structures encountered in the solid state is limited by two issues: (1) the difficulty of interpreting the intense pressure features that appear in atomic core regions and (2) the need to divide space among pairs of interacting atoms in a meaningful way. In this article, we describe general solutions to these issues. In addressing the first issue, we explore the CP analysis of a test case in which no core pressures would be expected to arise: isolated atoms in large boxes. Our calculations reveal that intense core pressures do indeed arise in these virtually pressure-less model systems and allow us to trace the issue to the shifts in the voxel positions relative to atomic centers upon expanding and contracting the unit cell. A compensatory grid unwarping procedure is introduced to remedy this artifact. The second issue revolves around the difficulty of interpreting the pressure map in terms of interatomic interactions in a way that respects the size differences of the atoms and avoids artificial geometrical

Spectroscopy of systems of two identical atoms: effects of quantum interference

International Nuclear Information System (INIS)

Makarov, A.A.; Yudson, V.I.

2017-01-01

Several effects of quantum interference in spectroscopy of a system of two atoms are discussed. (i) In the system of spatially separated atoms in a one-dimensional (1D) geometry (a single-mode waveguide or photon crystal), a (meta)stable excited entangled state can be formed, its decay being very sensitive to the distance between the atoms and to perturbations which cause a difference between their resonance frequencies. (ii) In a system of closely located atoms in 3D space, the extreme sensitivity of absorption and fluorescence spectra to the direction of the applied magnetic field is demonstrated. These theoretical predictions can be useful for the quantum information processing and ultrasensitive measurements.

Information entropy properties of the atoms in the system of coupled Λ-type three-level atoms interacting with coherent field in Kerr medium

International Nuclear Information System (INIS)

Li Ke; Ling Weijun

2011-01-01

The information entropy properties of the atoms of coupled Λ-type three-level atoms interacting with coherent field are studied by means of quantum theory, and discussed the time evolutions of the information entropy of the atoms via the average photon number, initial state of the atoms, detuning, coupling constant between the atoms and the coefficient of Kerr medium. Numerical calculation results show that the time evolutions of the information entropy properties of the atoms strongly dependent on the initial state of the system and the average photon number. Detuning, coupling constant between the atoms and the Kerr coefficient still make influence on the information entropy of the atoms. (authors)

Code ATOM for calculation of atomic characteristics

International Nuclear Information System (INIS)

Vainshtein, L.A.

1990-01-01

In applying atomic physics to problems of plasma diagnostics, it is necessary to determine some atomic characteristics, including energies and transition probabilities, for very many atoms and ions. Development of general codes for calculation of many types of atomic characteristics has been based on general but comparatively simple approximate methods. The program ATOM represents an attempt at effective use of such a general code. This report gives a brief description of the methods used, and the possibilities of and limitations to the code are discussed. Characteristics of the following processes can be calculated by ATOM: radiative transitions between discrete levels, radiative ionization and recombination, collisional excitation and ionization by electron impact, collisional excitation and ionization by point heavy particle (Born approximation only), dielectronic recombination, and autoionization. ATOM explores Born (for z=1) or Coulomb-Born (for z>1) approximations. In both cases exchange and normalization can be included. (N.K.)

Fidelity imaging for atomic force microscopy

Energy Technology Data Exchange (ETDEWEB)

Ghosal, Sayan, E-mail: ghos0087@umn.edu; Salapaka, Murti, E-mail: murtis@umn.edu [Nanodynamics Systems Laboratory, Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2015-01-05

Atomic force microscopy is widely employed for imaging material at the nanoscale. However, real-time measures on image reliability are lacking in contemporary atomic force microscopy literature. In this article, we present a real-time technique that provides an image of fidelity for a high bandwidth dynamic mode imaging scheme. The fidelity images define channels that allow the user to have additional authority over the choice of decision threshold that facilitates where the emphasis is desired, on discovering most true features on the sample with the possible detection of high number of false features, or emphasizing minimizing instances of false detections. Simulation and experimental results demonstrate the effectiveness of fidelity imaging.

Four shells atomic model to computer the counting efficiency of electron-capture nuclides

International Nuclear Information System (INIS)

Grau Malonda, A.; Fernandez Martinez, A.

1985-01-01

The present paper develops a four-shells atomic model in order to obtain the efficiency of detection in liquid scintillation courting, Mathematical expressions are given to calculate the probabilities of the 229 different atomic rearrangements so as the corresponding effective energies. This new model will permit the study of the influence of the different parameters upon the counting efficiency for nuclides of high atomic number. (Author) 7 refs

Atomization of volatile compounds for atomic absorption and atomic fluorescence spectrometry: On the way towards the ideal atomizer

International Nuclear Information System (INIS)

Dedina, Jiri

2007-01-01

This review summarizes and discusses the individual atomizers of volatile compounds. A set of criteria important for analytical praxis is used to rank all the currently existing approaches to the atomization based on on-line atomization for atomic absorption (AAS) and atomic fluorescence spectrometry (AFS) as well as on in-atomizer trapping for AAS. Regarding on-line atomization for AAS, conventional quartz tubes are currently the most commonly used devices. They provide high sensitivity and low baseline noise. Running and investment costs are low. The most serious disadvantage is the poor resistance against atomization interferences and often unsatisfactory linearity of calibration graphs. Miniature diffusion flame (MDF) is extremely resistant to interferences, simple, cheap and user-friendly. Its essential disadvantage is low sensitivity. A novel device, known as a multiatomizer, was designed to overcome disadvantages of previous atomizers. It matches performance of conventional quartz tubes in terms of sensitivity and baseline noise as well as in running and investment costs. The multiatomizer, however, provides much better (i) resistance against atomization interferences and (ii) linearity of calibration graphs. In-atomizer trapping enhances the sensitivity of the determination and eliminates the effect of the generation kinetics and of surges in gas flow on the signal shape. This is beneficial for the accuracy of the determination. It could also be an effective tool for reducing some interferences in the liquid phase. In-situ trapping in graphite furnaces (GF) is presently by far the most popular approach to the in-atomizer trapping. Its resistance against interferences is reasonably good and it can be easily automated. In-situ trapping in GF is a mature method well established in various application fields. These are the reasons to rank in-situ trapping in GF as currently the most convenient approach to hydride atomization for AAS. The recently suggested

Short-channel field-effect transistors with 9-atom and 13-atom wide graphene nanoribbons.

Science.gov (United States)

Llinas, Juan Pablo; Fairbrother, Andrew; Borin Barin, Gabriela; Shi, Wu; Lee, Kyunghoon; Wu, Shuang; Yong Choi, Byung; Braganza, Rohit; Lear, Jordan; Kau, Nicholas; Choi, Wonwoo; Chen, Chen; Pedramrazi, Zahra; Dumslaff, Tim; Narita, Akimitsu; Feng, Xinliang; Müllen, Klaus; Fischer, Felix; Zettl, Alex; Ruffieux, Pascal; Yablonovitch, Eli; Crommie, Michael; Fasel, Roman; Bokor, Jeffrey

2017-09-21

Bottom-up synthesized graphene nanoribbons and graphene nanoribbon heterostructures have promising electronic properties for high-performance field-effect transistors and ultra-low power devices such as tunneling field-effect transistors. However, the short length and wide band gap of these graphene nanoribbons have prevented the fabrication of devices with the desired performance and switching behavior. Here, by fabricating short channel (L ch  ~ 20 nm) devices with a thin, high-κ gate dielectric and a 9-atom wide (0.95 nm) armchair graphene nanoribbon as the channel material, we demonstrate field-effect transistors with high on-current (I on  > 1 μA at V d  = -1 V) and high I on /I off  ~ 10 5 at room temperature. We find that the performance of these devices is limited by tunneling through the Schottky barrier at the contacts and we observe an increase in the transparency of the barrier by increasing the gate field near the contacts. Our results thus demonstrate successful fabrication of high-performance short-channel field-effect transistors with bottom-up synthesized armchair graphene nanoribbons.Graphene nanoribbons show promise for high-performance field-effect transistors, however they often suffer from short lengths and wide band gaps. Here, the authors use a bottom-up synthesis approach to fabricate 9- and 13-atom wide ribbons, enabling short-channel transistors with 10 5 on-off current ratio.

Entanglement properties between two atoms in the binomial optical field interacting with two entangled atoms

International Nuclear Information System (INIS)

Liu Tang-Kun; Zhang Kang-Long; Tao Yu; Shan Chuan-Jia; Liu Ji-Bing

2016-01-01

The temporal evolution of the degree of entanglement between two atoms in a system of the binomial optical field interacting with two arbitrary entangled atoms is investigated. The influence of the strength of the dipole–dipole interaction between two atoms, probabilities of the Bernoulli trial, and particle number of the binomial optical field on the temporal evolution of the atomic entanglement are discussed. The result shows that the two atoms are always in the entanglement state. Moreover, if and only if the two atoms are initially in the maximally entangled state, the entanglement evolution is not affected by the parameters, and the degree of entanglement is always kept as 1. (paper)

A cellular automata simulation study of surface roughening resulting from multi-atom etch pit generation during sputtering

Energy Technology Data Exchange (ETDEWEB)

Toh, Y S; Nobes, M J; Carter, G [Dept. of Electronic and Electrical Engineering, Univ. of Salford (United Kingdom)

1992-04-01

A two-dimensional square matrix of pseudo-atomic positions is erected and atom removal from the ''surface'' is effected randomly. Either single atoms or groups of atoms (to simulate multi-atom pit generation) are removed. The characteristics of the evolving roughened, terraced ''surface'' are evaluated as a function of the total number of atoms, or equivalent numbers of atomic layers, removed. These characteristics include the ''mean'' position of the sputtered surface, the standard deviation of terrace length about the mean and the form of the terrace length distributions. The results of the single-atom removal mode compare exactly with theoretical predictions in that, for large numbers of atoms removed the depth position of the mean of the terrace length distribution is identical to the mean sputtered depth and the standard deviation increases as the square root of this depth. For multi-atom removal modes (which cannot be predicted theoretically) the standard deviation also increases as the square root of the mean sputtered depth but with a larger proportionality constant. The implications of these observations for the evolution of surface morphology during high yield sputtering is discussed. (orig.).

Effects of relativistic small radial component on atomic photoionization cross sections

International Nuclear Information System (INIS)

Liu Xiaobin; Xing Yongzhong; Sun Xiaowei

2008-01-01

The effects of relativistic small radial component on atomic photoionization cross sections have been studied within relativistic average self-consistent field theory. Relativistic effects are relatively unimportant for low photon energy, along with a review of high-energy photoionization the relativistic effects are quite important. The effects of relativistic small radial component on photoionization process should show breakdown when the nuclear finite-size effects is taken into account. The compression of wavefunction into the space near nucleus is so strong in highly charged ions that the electronic radius greatly decreases, and the effects of relativistic small radial component on photoionization cross sections turn to stronger than ordinary atoms. Since relativistic effects are extremely sensitive to the behavior of small radial component, the results are in good agreement with relativistic effects on photoionization cross section. (authors)

A Molecular Dynamics of Cold Neutral Atoms Captured by Carbon Nanotube Under Electric Field and Thermal Effect as a Selective Atoms Sensor.

Science.gov (United States)

Santos, Elson C; Neto, Abel F G; Maneschy, Carlos E; Chen, James; Ramalho, Teodorico C; Neto, A M J C

2015-05-01

Here we analyzed several physical behaviors through computational simulation of systems consisting of a zig-zag type carbon nanotube and relaxed cold atoms (Rb, Au, Si and Ar). These atoms were chosen due to their different chemical properties. The atoms individually were relaxed on the outside of the nanotube during the simulations. Each system was found under the influence of a uniform electric field parallel to the carbon nanotube and under the thermal effect of the initial temperature at the simulations. Because of the electric field, the cold atoms orbited the carbon nanotube while increasing the initial temperature allowed the variation of the radius of the orbiting atoms. We calculated the following quantities: kinetic energy, potential energy and total energy and in situ temperature, molar entropy variation and average radius of the orbit of the atoms. Our data suggest that only the action of electric field is enough to generate the attractive potential and this system could be used as a selected atoms sensor.

Plasma screening effects on the energies of hydrogen atom

International Nuclear Information System (INIS)

Soylu, A.

2012-01-01

A more general exponential cosine screened Coulomb potential is used for the first time to investigate the screening effects on the hydrogen atom in plasmas. This potential is examined for four different cases that correspond to four different type potentials when the different parameters are used in the potential within the framework of the well-known asymptotic iteration method. By solving the corresponding the radial Schrödinger equation with the screened and exponential cosine screened Coulomb potentials and comparing the obtained energy eigenvalues with the results of other studies, the applicability of the method to this kind of plasma physics problem is shown. The energy values of more general exponential cosine screened Coulomb potential are presented for various parameters in the potential. One of the advantages of the present potential is that it exhibits stronger screening effect than that of the exponential cosine screened Coulomb potential and it is also reduced to screened Coulomb and exponential cosine screened Coulomb as well as Coulomb potentials for special values of parameters. The parameters in the potential would be useful to model screening effects which cause an increase or decrease in the energy values of hydrogen atom in both Debye and quantum plasmas and in this manner this potential would be useful for the investigations of the atomic structure and collisions in plasmas.

Coherence effects in atomic impact processes

International Nuclear Information System (INIS)

Blum, K.

1980-01-01

The author considers excitation of target atoms by projectile particles and the coincident detection of the scattered projectiles and the photons emitted in the subsequent decay by the target atoms. The observation is restricted to radiation emitted by those atoms only which 'scattered' the projectiles with a given energy in a given direction defined by the particle detector. Thus, a certain subensemble of atoms is selected in the experiment. The author reviews the theoretical scheme used for the description of the excited subensemble with the emphasis on the coherence properties. The author reviews developments of the Fano-Macek theory concerning the description of coherently excited states with different angular momenta and parities. A comprehensive expression for the angular distribution of the emitted radiation, including all possible interference terms is given. (Auth.)

Cancer risk among children of atomic bomb survivors. A review of RERF epidemiologic studies. Radiation Effects Research Foundation

International Nuclear Information System (INIS)

Yoshimoto, Y.

1990-01-01

This article summarizes recent epidemiologic studies of cancer risk among the children of atomic bomb survivors conducted at the Radiation Effects Research Foundation. These children include two groups: (1) the in utero-exposed children (ie, those born to mothers who had been pregnant at the time of the bombings of Hiroshima and Nagasaki) and (2) the F1 population, which was conceived after the atomic-bombings and born to parents of whom one or both were atomic bomb survivors. Although from 1950 to 1984 only 18 cancer cases were identified among the in utero sample, cancer risk did appear to significantly increase as maternal uterine dose increased. However, since the observed cases are too few in number to allow a site-specific review, the increased cancer risk cannot be definitively attributed to atomic bomb radiation, as yet. For those members of the F1 population who were less than 20 years old between 1946 and 1982, cancer risk did not appear to increase significantly as parental gonadal dose increased. Follow-up of this population will continue to determine if the patterns of adult-onset cancer are altered

Stanford polarized atomic beam target

International Nuclear Information System (INIS)

Mavis, D.G.; Dunham, J.S.; Hugg, J.W.; Glavish, H.F.

1976-01-01

A polarized atomic beam source was used to produce an atomic hydrogen beam which was in turn used as a polarized proton target. A target density of 2 x 10'' atoms/cm 3 and a target polarization of 0.37 without the use of rf transitions were measured. These measurements indicate that a number of experiments are currently feasible with a variety of polarized target beams

Extreme electron correlation effects on the electric properties of atomic anions

International Nuclear Information System (INIS)

Canuto, S.

1994-01-01

The contribution of the electron correlation effects to the calculated dipole polarizability and hyper-polarizability of the first-row atomic anions is calculated and analyzed. It is shown that the total correlation contribution to the dipole hyperpolarizability is extremely large with the Hartree-Fock model accounting for only a small fraction of the accurate result. The linear and, more pronounced, the nonlinear response of atomic anions to the application of an electric field emphatically shows the effects of the correlated motion of the electrons

Charge degeneracy removal in the screened hydrogen atom

International Nuclear Information System (INIS)

Penna, Andre L A; Diniz, Joao B; Oliveira, Fernando A

2009-01-01

We derive an analytical model for the states of the screened hydrogen atom by using a new charge degeneracy removal approach. Starting from the nonzero Thomas-Fermi parameter q, we show that screening effect is due to breaks of the charge degeneracy in each quantum level of the hydrogen atom. The charge degeneracy removal reparametrizes the atomic system through the effective nuclear charge α n,l and the appearance of a dual charge γ n,l for each quantum level. In this approach, we show that the screening of a quantum state depends hierarchically on the screening from all previous quantum states with the same angular quantum numbers. The excited state energies E n,l (q) are analytically found taking into account the contribution of this new charge degeneracy for each quantum level. Finally, we also have estimated accurate critical screening parameters q* n,l for the bound-unbound transition.

Strong interaction effects in hadronic atoms

International Nuclear Information System (INIS)

Kaufmann, W.B.

1977-01-01

The WKB method is applied to the calculation of strong interaction-induced level widths and shifts of hadronic atoms. The calculation, while elementary enough for undergraduate quantum mechanics students, gives a good account of kaonic and antiprotonic atom data

Inner shells as a link between atomic and nuclear physics

International Nuclear Information System (INIS)

Merzbacher, E.

1982-01-01

Nuclear decay and reaction processes generally take place in neutral or partially ionized atoms. The effects of static nuclear properties (size, shape, moments) on atomic spectra are well known, as are electronic transitions accompanying nuclear transitions, e.g. K capture and internal conversion. Excitation or ionization of initially filled inner shells, really or virtually, may modify nuclear Q values, will require correction to measured beta-decay endpoint energies, and can permit the use of inner-shell transitions in the determination of nuclear widths. Improvements in resolution continue to enhance the importance of these effects. There is also beginning to appear experimental evidence of the dynamical effects of atomic electrons on the course of nuclear reactions. The dynamics of a nuclear reaction, which influences and may in turn be influenced by atomic electrons in inner shells, offers instructive examples of the interplay between strong and electromagnetic interactions and raises interesting questions about coherence properties of particle beams. A variety of significantly different collision regimes, depending on the atomic numbers of the collision partners and the collision velocity, will be discussed and illustrated. 21 References, 5 figures

Atoms in strong laser fields

International Nuclear Information System (INIS)

L'Huillier, A.

2002-01-01

When a high-power laser focuses into a gas of atoms, the electromagnetic field becomes of the same magnitude as the Coulomb field which binds a 1s electron in a hydrogen atom. 3 highly non-linear phenomena can happen: 1) ATI (above threshold ionization): electrons initially in the ground state absorb a large number of photons, many more than the minimum number required for ionization; 2) multiple ionization: many electrons can be emitted one at a time, in a sequential process, or simultaneously in a mechanism called direct or non-sequential; and 3) high order harmonic generation (HHG): efficient photon emission in the extreme ultraviolet range, in the form of high-order harmonics of the fundamental laser field can occur. The theoretical problem consists in solving the time dependent Schroedinger equation (TDSE) that describes the interaction of a many-electron atom with a laser field. A number of methods have been proposed to solve this problem in the case of a hydrogen atom or a single-active electron atom in a strong laser field. A large effort is presently being devoted to go beyond the single-active approximation. The understanding of the physics of the interaction between atoms and strong laser fields has been provided by a very simple model called ''simple man's theory''. A unified view of HHG, ATI, and non-sequential ionization, originating from the simple man's model and the strong field approximation, expressed in terms of electrons trajectories or quantum paths is slowly emerging. (A.C.)

Highly excited atoms

International Nuclear Information System (INIS)

Kleppner, D.; Littman, M.G.; Zimmerman, M.L.

1981-01-01

Highly excited atoms are often called Rydberg atoms. These atoms have a wealth of exotic properties which are discussed. Of special interest, are the effects of electric and magnetic fields on Rydberg atoms. Ordinary atoms are scarcely affected by an applied electric or magnetic field; Rydberg atoms can be strongly distorted and even pulled apart by a relatively weak electric field, and they can be squeezed into unexpected shapes by a magnetic field. Studies of the structure of Rydberg atoms in electric and magnetic fields have revealed dramatic atomic phenomena that had not been observed before

Non-destructive Faraday imaging of dynamically controlled ultracold atoms

Science.gov (United States)

Gajdacz, Miroslav; Pedersen, Poul; Mørch, Troels; Hilliard, Andrew; Arlt, Jan; Sherson, Jacob

2013-05-01

We investigate non-destructive measurements of ultra-cold atomic clouds based on dark field imaging of spatially resolved Faraday rotation. In particular, we pursue applications to dynamically controlled ultracold atoms. The dependence of the Faraday signal on laser detuning, atomic density and temperature is characterized in a detailed comparison with theory. In particular the destructivity per measurement is extremely low and we illustrate this by imaging the same cloud up to 2000 times. The technique is applied to avoid the effect of shot-to-shot fluctuations in atom number calibration. Adding dynamic changes to system parameters, we demonstrate single-run vector magnetic field imaging and single-run spatial imaging of the system's dynamic behavior. The method can be implemented particularly easily in standard imaging systems by the insertion of an extra polarizing beam splitter. These results are steps towards quantum state engineering using feedback control of ultracold atoms.

Interferometry with atoms

International Nuclear Information System (INIS)

Helmcke, J.; Riehle, F.; Witte, A.; Kisters, T.

1992-01-01

Physics and experimental results of atom interferometry are reviewed and several realizations of atom interferometers are summarized. As a typical example of an atom interferometer utilizing the internal degrees of freedom of the atom, we discuss the separated field excitation of a calcium atomic beam using four traveling laser fields and demonstrate the Sagnac effect in a rotating interferometer. The sensitivity of this interferometer can be largely increased by use of slow atoms with narrow velocity distribution. We therefore furthermore report on the preparation of a laser cooled and deflected calcium atomic beam. (orig.)

The Josephson effect in atomic contacts

International Nuclear Information System (INIS)

Chauvin, M.

2005-11-01

The Josephson effect appears when a weak-link establishes phase coherence between two superconductors. A unifying theory of this effect emerged in the 90's within the framework of mesoscopic physics. Based on two cornerstone concepts, conduction channels and Andreev reflection, it predicts the current-phase relation for the most basic weak-link: a single conduction channel of arbitrary transmission. This thesis illustrates this mesoscopic point of view with experiments on superconducting atomic size contacts. In particular, we have focused on the supercurrent peak around zero voltage, put into evidence the ac Josephson currents in a contact under constant bias voltage (Shapiro resonances and photon assisted multiple Andreev reflections), and performed direct measurements of the current-phase relation. (author)

X-ray spectrum determination of elements with low atomic number with use of electron microscope

International Nuclear Information System (INIS)

Smirnov, V.N.

1982-01-01

Separate assemblies of a commercial analytical electron microscope-microanalyzer EMMA-2 have been modified to study objects, containing elements with the atomic number Z=5-9, in particular: 1) the range of changing the accelerating voltages is expanded to be in the range of 25 down to 10 kV with 5 kV interval. 2) image intensifier using microchannel plate MKP-40-19 is applied; 3) for elements of carbon, oxygen, boron, nitrogen type a unit with flow-type proportional counter is used. The sensitivity of carbon- and oxygen determination in carbides and oxides is 0.15-0.3% at the measurement time of 100 s. Results of microanalysis of the particles of B 2 O 3 , Al 2 O 3 , SiO 2 , Fe 2 O 3 , Fe 3 C, WC for the contents of oxygen and carbon are presented

Investigation of the self tempering effect of martensite by means of atom probe tomography

International Nuclear Information System (INIS)

Sackl, Stephanie; Clemens, Helmut; Primig, Sophie

2015-01-01

Self-tempering effects can be observed in steels with relatively high martensite start temperatures. After the formation of the first martensitic laths, carbon is able to diffuse in these laths during cooling, which can be attributed to sufficiently high temperatures. This effect cannot be observed in laths formed at lower temperatures. In steels containing up to 0.2 m.-% carbon, up to 90 % of the carbon atoms in the martensite segregate to dislocations during quenching. Due to its atomic resolution and sensitivity with respect to light elements, atom probe tomography is very well suited for the investigation of this phenomenon. In this study, the self-tempering effect in a quenched and tempered steel 42CrMo4 with a martensite start temperature of 310 C is investigated by means of atom probe tomography.

Quantum information with Rydberg atoms

DEFF Research Database (Denmark)

Saffman, Mark; Walker, T.G.; Mølmer, Klaus

2010-01-01

Rydberg atoms with principal quantum number n»1 have exaggerated atomic properties including dipole-dipole interactions that scale as n4 and radiative lifetimes that scale as n3. It was proposed a decade ago to take advantage of these properties to implement quantum gates between neutral atom...... of multiqubit registers, implementation of robust light-atom quantum interfaces, and the potential for simulating quantum many-body physics. The advances of the last decade are reviewed, covering both theoretical and experimental aspects of Rydberg-mediated quantum information processing....

Correlation between catalytic activity and bonding and coordination number of atoms and molecules on transition metal surfaces: theory and experimental evidence

International Nuclear Information System (INIS)

Falicov, L.M.; Somorjai, G.A.

1985-01-01

Correlation between catalytic activity and low-energy local electronic fluctuation in transition metals is proposed. A theory and calculations are presented which indicate that maximum electronic fluctuants take place at high-coordination metal sites. Either (i) atomically rough surfaces that expose to the reactant molecules atoms with large numbers of nonmagnetic or weakly magnetic neighbors in the first or second layer at the surface or (ii) stepped and kinked surfaces are the most active in carrying out structure-sensitive catalytic reactions. The synthesis of ammonia from N 2 and H 2 over iron and rhenium surfaces, 1 H 2 / 2 H 2 exchange over stepped platinum crystal surfaces at low pressures, and the hydrogenolysis (C - C bond breaking) of isobutane at kinked platinum crystal surfaces are presented as experimental evidence in support of the theory

Atom chip gravimeter

Science.gov (United States)

Schubert, Christian; Abend, Sven; Gebbe, Martina; Gersemann, Matthias; Ahlers, Holger; Müntinga, Hauke; Matthias, Jonas; Sahelgozin, Maral; Herr, Waldemar; Lämmerzahl, Claus; Ertmer, Wolfgang; Rasel, Ernst

2016-04-01

Atom interferometry has developed into a tool for measuring rotations [1], accelerations [2], and testing fundamental physics [3]. Gravimeters based on laser cooled atoms demonstrated residual uncertainties of few microgal [2,4] and were simplified for field applications [5]. Atomic gravimeters rely on the interference of matter waves which are coherently manipulated by laser light fields. The latter can be interpreted as rulers to which the position of the atoms is compared. At three points in time separated by a free evolution, the light fields are pulsed onto the atoms. First, a coherent superposition of two momentum states is produced, then the momentum is inverted, and finally the two trajectories are recombined. Depending on the acceleration the atoms experienced, the number of atoms detected in the output ports will change. Consequently, the acceleration can be determined from the output signal. The laser cooled atoms with microkelvin temperatures used in state-of-the-art gravimeters impose limits on the accuracy [4]. Therefore, ultra-cold atoms generated by Bose-Einstein condensation and delta-kick collimation [6,7] are expected to be the key for further improvements. These sources suffered from a low flux implying an incompatible noise floor, but a competitive performance was demonstrated recently with atom chips [8]. In the compact and robust setup constructed for operation in the drop tower [6] we demonstrated all steps necessary for an atom chip gravimeter with Bose-Einstein condensates in a ground based operation. We will discuss the principle of operation, the current performance, and the perspectives to supersede the state of the art. The authors thank the QUANTUS cooperation for contributions to the drop tower project in the earlier stages. This work is supported by the German Space Agency (DLR) with funds provided by the Federal Ministry for Economic Affairs and Energy (BMWi) due to an enactment of the German Bundestag under grant numbers DLR 50WM

The effect of the cranial bone CT numbers on the brain CT numbers

Energy Technology Data Exchange (ETDEWEB)

Fukuda, Hitoshi; Kobayashi, Shotai; Koide, Hiromi; Yamaguchi, Shuhei; Okada, Kazunori; Shimote, Koichi; Tsunematsu, Tokugoro (Shimane Medical Univ., Izumo (Japan))

1989-06-01

The effects of the cranial size and the computed tomography (CT) numbers of the cranial bone on that of the brain were studied in 70 subjects, aged from 30 to 94 years. The subjects had no histories of cerebrovascular accidents and showed no abnormalities in the central nervous system upon physical examinations and a CT scan. We measured the average attenuation values (CT numbers) of each elliptical region (165 pixels, 0.39 cm{sup 2}) at the bilateral thalamus and at twelve areas of the deep white matter. Multiple regression analysis was used to assess the effects of age, cranial size, and cranial bone CT numbers on the brain CT numbers. The effect of the cranial bone CT numbers on the brain CT numbers was statistically significant. The brain CT numbers increased with the increase in the cranial bone CT numbers. There was, however, no significant correlation between brain CT numbers and cranial size. In measuring the brain CT numbers, it is desirable that consideration be given to the cranial bone CT numbers. (author).

The adsorption of helium atoms on coronene cations

Energy Technology Data Exchange (ETDEWEB)

Kurzthaler, Thomas; Rasul, Bilal; Kuhn, Martin; Scheier, Paul, E-mail: Paul.Scheier@uibk.ac.at, E-mail: andrew.ellis@le.ac.uk [Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25, A-6020 Innsbruck (Austria); Lindinger, Albrecht [Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin (Germany); Ellis, Andrew M., E-mail: Paul.Scheier@uibk.ac.at, E-mail: andrew.ellis@le.ac.uk [Department of Chemistry, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom)

2016-08-14

We report the first experimental study of the attachment of multiple foreign atoms to a cationic polycyclic aromatic hydrocarbon (PAH). The chosen PAH was coronene, C{sub 24}H{sub 12}, which was added to liquid helium nanodroplets and then subjected to electron bombardment. Using mass spectrometry, coronene cations decorated with helium atoms were clearly seen and the spectrum shows peaks with anomalously high intensities (“magic number” peaks), which represent ion-helium complexes with added stability. The data suggest the formation of a rigid helium layer consisting of 38 helium atoms that completely cover both faces of the coronene ion. Additional magic numbers can be seen for the further addition of 3 and 6 helium atoms, which are thought to attach to the edge of the coronene. The observation of magic numbers for the addition of 38 and 44 helium atoms is in good agreement with a recent path integral Monte Carlo prediction for helium atoms on neutral coronene. An understanding of how atoms and molecules attach to PAH ions is important for a number of reasons including the potential role such complexes might play in the chemistry of the interstellar medium.

Optical polarization modulation by competing atomic coherence effects in a degenerate four-level Yb atomic system

International Nuclear Information System (INIS)

Park, Sung Jong; Park, Chang Yong; Yoon, Tai Hyun

2005-01-01

A scheme of optical polarization modulation of a linearly polarized infrared probe field is studied in a degenerate four-level Yb atomic system. We have observed an anomalous transmission spectra of two circular polarization components of the probe field exhibiting an enhanced two-photon absorption and a three-photon gain with comparable magnitude, leading to the lossless transmission and enhanced circular dichroism. We carried out a proof-of-principle experiment of fast optical polarization modulation in such a system by modulating the polarization state of the coupling field. The observed enhanced two-photon absorption and three-photon gain of the probe field are due to the result of competing atomic coherence effects

Three-atom clusters

International Nuclear Information System (INIS)

Pen'kov, F.M.

1998-01-01

The Born-Oppenheimer approximation is used to obtain an equation for the effective interaction in three atoms bound by a single electron. For low binding energies in an 'electron + atom' pair, long-range forces arise between the atoms, leading to bound states when the size of the three-atom cluster is a few tens of angstrom. A system made of alkali-metal atoms is considered as an example

Gauss Sum Factorization with Cold Atoms

International Nuclear Information System (INIS)

Gilowski, M.; Wendrich, T.; Mueller, T.; Ertmer, W.; Rasel, E. M.; Jentsch, Ch.; Schleich, W. P.

2008-01-01

We report the first implementation of a Gauss sum factorization algorithm by an internal state Ramsey interferometer using cold atoms. A sequence of appropriately designed light pulses interacts with an ensemble of cold rubidium atoms. The final population in the involved atomic levels determines a Gauss sum. With this technique we factor the number N=263193

Resonance ionization spectroscopy: Counting noble gas atoms

International Nuclear Information System (INIS)

Hurst, G.S.; Payne, M.G.; Chen, C.H.; Willis, R.D.; Lehmann, B.E.; Kramer, S.D.

1981-01-01

The purpose of this paper is to describe new work on the counting of noble gas atoms, using lasers for the selective ionization and detectors for counting individual particles (electrons or positive ions). When positive ions are counted, various kinds of mass analyzers (magnetic, quadrupole, or time-of-flight) can be incorporated to provide A selectivity. We show that a variety of interesting and important applications can be made with atom-counting techniques which are both atomic number (Z) and mass number (A) selective. (orig./FKS)

Hot atom chemistry of monovalent atoms in organic condensed phases

International Nuclear Information System (INIS)

Stoecklin, G.

1975-01-01

The advantages and disadvantages of hot atom studies in condensed organic phases are considered, and recent advances in condensed phase organic hot atom chemistry of recoil tritium and halogen atoms are discussed. Details are presented of the present status and understanding of liquid phase hot atom chemistry and also that of organic solids. The consequences of the Auger effect in condensed organic systems are also considered. (author)

Hiroshima - the effects of the atom bomb

International Nuclear Information System (INIS)

McClelland, M.

1977-01-01

The author, a nurse, describes her personal impressions of a visit to Hiroshima in 1977 and of the medical and nursing facilities available for atomic bomb survivors in Japan. The findings of the Radiation Effects Research Foundation are briefly summarized. Hiroshima's Red Cross Hospital, recently re-built, cares for some of the survivors. The problems of discrimination against the survivors in employment and in society are discussed. (U.K.)

Fluorine Gauche Effect Explained by Electrostatic Polarization Instead of Hyperconjugation: An Interacting Quantum Atoms (IQA) and Relative Energy Gradient (REG) Study.

Science.gov (United States)

Thacker, Joseph C R; Popelier, Paul L A

2018-02-08

We present an interacting quantum atoms (IQA) study of the gauche effect by comparing 1,2-difluoroethane, 1,2-dichloroethane, and three conformers of 1,2,3,4,5,6-hexafluorocyclohexane. In the 1,2-difluoroethane, the gauche effect is observed in that the gauche conformation is more stable than the anti, whereas in 1,2-dichloroethane the opposite is true. The analysis performed here is exhaustive and unbiased thanks to using the recently introduced relative energy gradient (REG) method [ Thacker , J. C. R. ; Popelier , P. L. A. Theor. Chem. Acc . 2017 , 136 , 86 ], as implemented in the in-house program ANANKE. We challenge the common explanation that hyperconjugation is responsible for the gauche stability in 1,2-difluoroethane and instead present electrostatics as the cause of gauche stability. Our explanation of the gauche effect is also is seen in other molecules displaying local gauche conformations, such as the recently synthesized "all-cis" hexafluorocyclohexane and its conformers where all the fluorine atoms are in the equatorial positions. Using our extension of the traditional IQA methodology that allows for the partitioning of electrostatic terms into polarization and charge transfer, we propose that the cause of gauche stability is 1,3 C···F electrostatic polarization interactions. In other words, if a number of fluorine atoms are aligned, then the stability due to polarization of nearby carbon atoms is increased.

Microwave multiphoton excitation of helium Rydberg atoms: The analogy with atomic collisions

International Nuclear Information System (INIS)

van de Water, W.; van Leeuwen, K.A.H.; Yoakum, S.; Galvez, E.J.; Moorman, L.; Bergeman, T.; Sauer, B.E.; Koch, P.M.

1989-01-01

We study multiphoton transitions in helium Rydberg atoms subjected to a microwave electric field of fixed frequency but varying intensity. For each principal quantum number in the range n=25--32, the n 3 S to n 3 (L>2), n=25--32, transition probability exhibits very sharp structures as a function of the field amplitude. Their positions could be reproduced precisely using a Floquet Hamiltonian for the interaction between atom and field. Their shapes are determined by the transients of field turn-on and turn-off in a way that makes a close analogy with the theory of slow atomic collisions

Differential cross section of atomic hydrogen photoionization

International Nuclear Information System (INIS)

Kondratovich, V.D.; Ostrovskij, V.N.

1986-01-01

Differential cross-section of atomic hydrogen photoeffect in external electric field was investigated in semiclassical approximation. Interference was described. It occurred due to the fact that infinite number of photoelectron trajectories leads to any point of classically accessible motion region. Interference picture can reach macroscopic sizes. The picture is determined by location of function nodes, describing finite electron motion along one of parabolic coordinates. The squares of external picture rings are determined only by electric field intensity in the general case at rather high energies. Quantum expression for photocurrent density was obtained using Green function in superposition of Coulomb and uniform field as well as semiclassical approximation. Possible applications of macroscopic interference picture to specification of atom ionization potentials, selective detection of atoms or particular molecules, as well as weak magnetic field and observation of Aaronov-Bom effect are discussed

Theory of inelastic effects in resonant atom-surface scattering

International Nuclear Information System (INIS)

Evans, D.K.

1983-01-01

The progress of theoretical and experimental developments in atom-surface scattering is briefly reviewed. The formal theory of atom-surface resonant scattering is reviewed and expanded, with both S and T matrix approaches being explained. The two-potential formalism is shown to be useful for dealing with the problem in question. A detailed theory based on the S-matrix and the two-potential formalism is presented. This theory takes account of interactions between the incident atoms and the surface phonons, with resonant effects being displayed explicitly. The Debye-Waller attenuation is also studied. The case in which the atom-surface potential is divided into an attractive part V/sub a/ and a repulsive part V/sub r/ is considered at length. Several techniques are presented for handling the scattering due to V/sub r/, for the case in which V/sub r/ is taken to be the hard corrugated surface potential. The theory is used to calculate the scattered intensities for the system 4 He/LiF(001). A detailed comparison with experiment is made, with polar scans, azimuthal scans, and time-of-flight measurements being considered. The theory is seen to explain the location and signature of resonant features, and to provide reasonable overall agreement with the experimental results

Two-dimensional atom localization via two standing-wave fields in a four-level atomic system

International Nuclear Information System (INIS)

Zhang Hongtao; Wang Hui; Wang Zhiping

2011-01-01

We propose a scheme for the two-dimensional (2D) localization of an atom in a four-level Y-type atomic system. By applying two orthogonal standing-wave fields, the atoms can be localized at some special positions, leading to the formation of sub-wavelength 2D periodic spatial distributions. The localization peak position and number as well as the conditional position probability can be controlled by the intensities and detunings of optical fields.

Lamb shift of Rydberg atoms in a resonator

International Nuclear Information System (INIS)

Belov, A.A.; Lozovik, Yu.E.; Pokrovsky, V.L.

1988-08-01

The Lamb shift of a Rydberg atom in a cavity is shown to be enhanced with the resonance interaction of a virtual atomic transition and cavity modes. The dependence of the Lamb shift on quantum numbers and atomic number changes drastically. Shifting cavity walls and scanning the atomic beam one can vary the Lamb shift. The value of the Lamb shift in a cavity may exceed a typical magnitude of the fine structure energy. For a rough resonance tuning the Coulumb multiplet occurs to be strongly mixed and a novel classification is necessary. (author). 8 refs, 2 figs

Polarizational radiation or 'atomic' bremsstrahlung

International Nuclear Information System (INIS)

Ya Amusia, M.

1992-01-01

It is demonstrated that a new kind of continuum spectrum radiation exists, where the mechanism of formation is quite different from that of ordinary bremsstrahlung. The latter originates due to slowing down of the charged projectile in the target field, while the former, called polarization radiation or 'atomic' bremsstrahlung, is a result of radiation either of the target or the projectile particles dipolarly polarized during the collision process. Not only general formulae, but also results of concrete calculations are presented. These demonstrate, that for electron-atom collisions the atomic contribution to the total bremsstrahlung spectrum becomes dominant for photon energies near and above the atomic ionization potential. As to atom-atom or ion-atom collisions, the bremsstrahlung spectrum is completely determined by the atomic contribution. The specific features of the case when the incoming particles are relativistic are discussed at length. A number of examples of colliding pairs are considered, for which the atomic bremsstrahlung process is quite essential: A bare nucleus and an atom, pair of atoms, at least one of which is excited, electron, or atom interacting with a molecule. The same mechanism is essential also in formation of radiation in nuclear and elementary particle collisions. (orig.)

Theoretical evaluation of matrix effects on trapped atomic levels

Energy Technology Data Exchange (ETDEWEB)

Das, G.P.; Gruen, D.M.

1986-06-01

We suggest a theoretical model for calculating the matrix perturbation on the spectra of atoms trapped in rare gas systems. The model requires the ''potential curves'' of the diatomic system consisting of the trapped atom interacting with one from the matrix and relies on the approximation that the total matrix perturbation is a scalar sum of the pairwise interactions with each of the lattice sites. Calculations are presented for the prototype systems Na in Ar. Attempts are made to obtain ab initio estimates of the Jahn-Teller effects for excited states. Comparison is made with our recent Matrix-Isolation Spectroscopic (MIS) data. 10 refs., 3 tabs.

Theoretical evaluation of matrix effects on trapped atomic levels

International Nuclear Information System (INIS)

Das, G.P.; Gruen, D.M.

1986-06-01

We suggest a theoretical model for calculating the matrix perturbation on the spectra of atoms trapped in rare gas systems. The model requires the ''potential curves'' of the diatomic system consisting of the trapped atom interacting with one from the matrix and relies on the approximation that the total matrix perturbation is a scalar sum of the pairwise interactions with each of the lattice sites. Calculations are presented for the prototype systems Na in Ar. Attempts are made to obtain ab initio estimates of the Jahn-Teller effects for excited states. Comparison is made with our recent Matrix-Isolation Spectroscopic (MIS) data. 10 refs., 3 tabs

Charge transfer rates for xenon Rydberg atoms at metal and semiconductor surfaces

Energy Technology Data Exchange (ETDEWEB)

Dunning, F.B. [Department of Physics and Astronomy, Rice University, MS 61, 6100 Main Street, Houston, TX 77005-1892 (United States)]. E-mail: fbd@rice.edu; Wethekam, S. [Institut fuer Physik der Humboldt-Universitaet zu Berlin, Newtonstr. 15, D-12489 Berlin (Germany); Dunham, H.R. [Department of Physics and Astronomy, Rice University, MS 61, 6100 Main Street, Houston, TX 77005-1892 (United States); Lancaster, J.C. [Department of Physics and Astronomy, Rice University, MS 61, 6100 Main Street, Houston, TX 77005-1892 (United States)

2007-05-15

Recent progress in the study of charge exchange between xenon Rydberg atoms and surfaces is reviewed. Experiments using Au(1 1 1) surfaces show that under appropriate conditions each incident atom can be detected as an ion. The ionization dynamics, however, are strongly influenced by the perturbations in the energies and structure of the atomic states that occur as the ion collection field is applied and as the atom approaches the surface. These lead to avoided crossings between different atomic levels causing the atom to successively assume the character of a number of different states and lose much of its initial identity. The effects of this mixing are discussed. Efficient surface ionization is also observed at Si(1 0 0) surfaces although the ion signal is influenced by stray fields present at the surface.

Universal Four-Boson System: Dimer-Atom-Atom Efimov Effect and Recombination Reactions

International Nuclear Information System (INIS)

Deltuva, A.

2013-01-01

Recent theoretical developments in the four-boson system with resonant interactions are described. Momentum-space scattering equations for the four-particle transition operators are used. The properties of unstable tetramers with approximate dimer-atom-atom structure are determined. In addition, the three- and four-cluster recombination processes in the four-boson system are studied. (author)

Effects of the Substituents of Boron Atoms on Conjugated Polymers Containing B←N Units.

Science.gov (United States)

Liu, Jun; Wang, Tao; Dou, Chuandong; Wang, Lixiang

2018-06-15

Organoboron chemistry is a new tool to tune the electronic structures and properties of conjugated polymers, which are important for applications in organic opto-electronic devices. To investigate the effects of substituents of boron atoms on conjugated polymers, we synthesized three conjugated polymers based on double B←N bridged bipyridine (BNBP) with various substituents on the boron atoms. By changing the substituents from four phenyl groups and two phenyl groups/two fluorine atoms to four fluorine atoms, the BNBP-based polymers show the blue-shifted absorption spectra, decreased LUMO/HOMO energy levels and enhanced electron affinities, as well as the increased electron mobilities. Moreover, these BNBP-based polymers can be used as electron acceptors for all-polymer solar cells. These results demonstrate that the substituents of boron atoms can effectively modulate the electronic properties and applications of conjugated polymers. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Ubiquitous atom

International Nuclear Information System (INIS)

Spruch, G.M.; Spruch, L.

1974-01-01

The fundamentals of modern physics, including the basic physics and chemistry of the atom, elementary particles, cosmology, periodicity, and recent advances, are surveyed. The biology and chemistry of the life process is discussed to provide a background for considering the effects of atomic particles on living things. The uses of atomic power in space travel, merchant shipping, food preservation, desalination, and nuclear clocks are explored. (Pollut. Abstr.)

Nonlinear effects in defect production by atomic and molecular ion implantation

International Nuclear Information System (INIS)

David, C.; Dholakia, Manan; Chandra, Sharat; Nair, K. G. M.; Panigrahi, B. K.; Amirthapandian, S.; Amarendra, G.; Varghese Anto, C.; Santhana Raman, P.; Kennedy, John

2015-01-01

This report deals with studies concerning vacancy related defects created in silicon due to implantation of 200 keV per atom aluminium and its molecular ions up to a plurality of 4. The depth profiles of vacancy defects in samples in their as implanted condition are carried out by Doppler broadening spectroscopy using low energy positron beams. In contrast to studies in the literature reporting a progressive increase in damage with plurality, implantation of aluminium atomic and molecular ions up to Al 3 , resulted in production of similar concentration of vacancy defects. However, a drastic increase in vacancy defects is observed due to Al 4 implantation. The observed behavioural trend with respect to plurality has even translated to the number of vacancies locked in vacancy clusters, as determined through gold labelling experiments. The impact of aluminium atomic and molecular ions simulated using MD showed a monotonic increase in production of vacancy defects for cluster sizes up to 4. The trend in damage production with plurality has been explained on the basis of a defect evolution scheme in which for medium defect concentrations, there is a saturation of the as-implanted damage and an increase for higher defect concentrations

Dissipative Double-Well Potential for Cold Atoms: Kramers Rate and Stochastic Resonance.

Science.gov (United States)

Stroescu, Ion; Hume, David B; Oberthaler, Markus K

2016-12-09

We experimentally study particle exchange in a dissipative double-well potential using laser-cooled atoms in a hybrid trap. We measure the particle hopping rate as a function of barrier height, temperature, and atom number. Single-particle resolution allows us to measure rates over more than 4 orders of magnitude and distinguish the effects of loss and hopping. Deviations from the Arrhenius-law scaling at high barrier heights occur due to cold collisions between atoms within a well. By driving the system periodically, we characterize the phenomenon of stochastic resonance in the system response.

Study of inter sub-shell and inter shell electron correlations in 4d open-shell heavy atomic ions

International Nuclear Information System (INIS)

Koike, Fumihiro

2009-01-01

The effect of correlations between 4p, 4d, and 4f has been studied extensively. The characteristic spectral structures of 4p - 4d and 4d - 4f optical transitions, due to the unique structures of N = 4 open sub-shells in heavy atomic ions, have been studied theoretically. To gain an insight of this effect, a series of careful MCDF calculations for 4d q (q = 0 to 10) atomic ions with atomic numbers Z = 48 to 56 has been carried out. The difference of orbital energy differences between 4p and 4d orbitals and 4d and 4f orbitals coincidently falls within the range of a few % for almost all the atomic ions investigated. The 4p 6 4d4f and 4p 5 4d 3 configurations may mix strongly, and the optical 4p - 4d and 4d - 4f transitions may take place coherently, providing us with quite a peculiar EUV emission spectrum. The effect of spectral narrowing and shift is expected to be quite common to the atomic specieds with the atomic numbers in the range Z = 48 to 56.

Push-Pull Laser-Atomic Oscillator

International Nuclear Information System (INIS)

Jau, Y.-Y.; Happer, W.

2007-01-01

A vapor of alkali-metal atoms in the external cavity of a semiconductor laser, pumped with a time-independent injection current, can cause the laser to self-modulate at the 'field-independent 0-0 frequency' of the atoms. Push-pull optical pumping by the modulated light drives most of the atoms into a coherent superposition of the two atomic sublevels with an azimuthal quantum number m=0. The atoms modulate the optical loss of the cavity at the sharply defined 0-0 hyperfine frequency. As in a maser, the system is not driven by an external source of microwaves, but a very stable microwave signal can be recovered from the modulated light or from the modulated voltage drop across the laser diode. Potential applications for this new phenomenon include atomic clocks, the production of long-lived coherent atomic states, and the generation of coherent optical combs

Genetic radiation effects of Hiroshima and Nagasaki atomic bombs

International Nuclear Information System (INIS)

Srsen, S.

1984-01-01

A group of researchers examined persons who had survived the Hiroshima and Nagasaki bombs and were irradiated and their progeny with the aim of getting an idea of the genetic effects of these explosions. Teratogenic effects are not discussed. In the lymphocytes of the peripheral blood of persons who had been exposed to high dose irradiation the researchers found a significant increase in chromosomal aberrations by conventional and more recent methods of chromosomal analysis. In parents who had survived the atomic holocaust there were no significant deviations as against the rest of the population in still births, neonatal defects, infant mortality, and mortality of first generation progeny, in neonate weight, the sex ratio, increased occurence of leukosis and chromosomal aberrations in their children. These negative findings in the first generation do not signify that there is no danger from atomic bomb blasts for human kind. They only indicate that the effects of radiation were to small to be found by routine methods or that the methods used were not suitable

Genetic radiation effects of Hiroshima and Nagasaki atomic bombs

Energy Technology Data Exchange (ETDEWEB)

Srsen, S. (Komenskeho Univ., Bratislava (Czechoslovakia). Lekarska Fakulta)

1984-05-01

A group of researchers examined persons who had survived the Hiroshima and Nagasaki bombs and were irradiated and their progeny with the aim of getting an idea of the genetic effects of these explosions. Teratogenic effects are not discussed. In the lymphocytes of the peripheral blood of persons who had been exposed to high dose irradiation the researchers found a significant increase in chromosomal aberrations by conventional and more recent methods of chromosomal analysis. In parents who had survived the atomic holocaust there were no significant deviations as against the rest of the population in still births, neonatal defects, infant mortality, and mortality of first generation progeny, in neonate weight, the sex ratio, increased occurence of leukosis and chromosomal aberrations in their children. These negative findings in the first generation do not signify that there is no danger from atomic bomb blasts for human kind. They only indicate that the effects of radiation were too small to be found by routine methods or that the methods used were not suitable.

On the Zeeman Effect in highly excited atoms: 2. Three-dimensional case

International Nuclear Information System (INIS)

Baseia, B.; Medeiros e Silva Filho, J.

1984-01-01

A previous result, found in two-dimensional hydrogen-atoms, is extended to the three-dimensional case. A mapping of a four-dimensional space R 4 onto R 3 , that establishes an equivalence between Coulomb and harmonic potentials, is used to show that the exact solution of the Zeeman effect in highly excited atoms, cannot be reached. (Author) [pt

Optimal control of complex atomic quantum systems.

Science.gov (United States)

van Frank, S; Bonneau, M; Schmiedmayer, J; Hild, S; Gross, C; Cheneau, M; Bloch, I; Pichler, T; Negretti, A; Calarco, T; Montangero, S

2016-10-11

Quantum technologies will ultimately require manipulating many-body quantum systems with high precision. Cold atom experiments represent a stepping stone in that direction: a high degree of control has been achieved on systems of increasing complexity. However, this control is still sub-optimal. In many scenarios, achieving a fast transformation is crucial to fight against decoherence and imperfection effects. Optimal control theory is believed to be the ideal candidate to bridge the gap between early stage proof-of-principle demonstrations and experimental protocols suitable for practical applications. Indeed, it can engineer protocols at the quantum speed limit - the fastest achievable timescale of the transformation. Here, we demonstrate such potential by computing theoretically and verifying experimentally the optimal transformations in two very different interacting systems: the coherent manipulation of motional states of an atomic Bose-Einstein condensate and the crossing of a quantum phase transition in small systems of cold atoms in optical lattices. We also show that such processes are robust with respect to perturbations, including temperature and atom number fluctuations.

Black-body radiation effects and light shifts in atomic frequency standards

Energy Technology Data Exchange (ETDEWEB)

Pal' chikov, V G; Domnin, Yu S; Novoselov, A V [Institute of Metrology for Time and Space at National Research Institute for Physical-Technical and Radiotechnical Measurements - IMVP GP VNIIFTRI, Mendeleevo, Moscow Region, 141570 (Russian Federation)

2003-04-01

A general method is presented for calculating the higher-order terms of series in powers of the black-body radiation field for the Stark-state wavefunctions, dipole transition matrix elements and corresponding frequency shifts of hyperfine splitting in the ground states for Cs and Rb atoms. A numerical method for calculating the light shifts in Sr atoms is described. It is based on the Green function method for summation over all intermediate states and exact Dirac-Fock wavefunctions for the resonant transitions to the first excited s-, p- and d-states. By comparing the calculated Stark shift with results of measurements employing atomic frequency standards, the black-body radiation effects on the ground state are analysed.

Generation of Exotic Quantum States of a Cold Atomic Ensemble

DEFF Research Database (Denmark)

Christensen, Stefan Lund

Over the last decades quantum effects have become more and more controllable, leading to the implementations of various quantum information protocols. These protocols are all based on utilizing quantum correlation. In this thesis we consider how states of an atomic ensemble with such correlations...... can be created and characterized. First we consider a spin-squeezed state. This state is generated by performing quantum non-demolition measurements of the atomic population difference. We show a spectroscopically relevant noise reduction of -1.7dB, the ensemble is in a many-body entangled state...... — a nanofiber based light-atom interface. Using a dual-frequency probing method we measure and prepare an ensemble with a sub-Poissonian atom number distribution. This is a first step towards the implementation of more exotic quantum states....

Angular distribution and atomic effects in condensed phase photoelectron spectroscopy

International Nuclear Information System (INIS)

Davis, R.F.

1981-11-01

A general concept of condensed phase photoelectron spectroscopy is that angular distribution and atomic effects in the photoemission intensity are determined by different mechanisms, the former being determined largely by ordering phenomena such as crystal momentum conservation and photoelectron diffraction while the latter are manifested in the total (angle-integrated) cross section. In this work, the physics of the photoemission process is investigated in several very different experiments to elucidate the mechanisms of, and correlation between, atomic and angular distribution effects. Theoretical models are discussed and the connection betweeen the two effects is clearly established. The remainder of this thesis, which describes experiments utilizing both angle-resolved and angle-integrated photoemission in conjunction with synchrotron radiation in the energy range 6 eV less than or equal to h ν less than or equal to 360 eV and laboratory sources, is divided into three parts

Number series of atoms, interatomic bonds and interface bonds defining zinc-blende nanocrystals as function of size, shape and surface orientation: Analytic tools to interpret solid state spectroscopy data

Directory of Open Access Journals (Sweden)

Dirk König

2016-08-01

Full Text Available Semiconductor nanocrystals (NCs experience stress and charge transfer by embedding materials or ligands and impurity atoms. In return, the environment of NCs experiences a NC stress response which may lead to matrix deformation and propagated strain. Up to now, there is no universal gauge to evaluate the stress impact on NCs and their response as a function of NC size dNC. I deduce geometrical number series as analytical tools to obtain the number of NC atoms NNC(dNC[i], bonds between NC atoms Nbnd(dNC[i] and interface bonds NIF(dNC[i] for seven high symmetry zinc-blende (zb NCs with low-index faceting: {001} cubes, {111} octahedra, {110} dodecahedra, {001}-{111} pyramids, {111} tetrahedra, {111}-{001} quatrodecahedra and {001}-{111} quadrodecahedra. The fundamental insights into NC structures revealed here allow for major advancements in data interpretation and understanding of zb- and diamond-lattice based nanomaterials. The analytical number series can serve as a standard procedure for stress evaluation in solid state spectroscopy due to their deterministic nature, easy use and general applicability over a wide range of spectroscopy methods as well as NC sizes, forms and materials.

Collective excitations in circular atomic configurations and single-photon traps

International Nuclear Information System (INIS)

Hammer, Hanno

2004-01-01

Correlated excitations in a plane circular configuration of identical atoms with parallel dipole moments are investigated. The collective energy eigenstates, which are formally identical to Frenkel excitons, can be computed together with their level shifts and decay rates by decomposing the atomic state space into carrier spaces for the irreducible representations of the symmetry group Z N of the circle. It is shown that the index p of these representations can be used as a quantum number analogously to the orbital angular momentum quantum number l in hydrogenlike systems. Just as the hydrogen s states are the only electronic wave functions which can occupy the central region of the Coulomb potential, the quasiparticle corresponding to a collective excitation of the atoms in the circle can occupy the central atom only for vanishing Z N quantum number p. If a central atom is present, the p=0 state splits into two and shows level crossing at certain radii; in the regions between these radii, damped quantum beats between two 'extreme' p=0 configurations occur. The physical mechanisms behind super- and subradiance at a given radius are discussed. It is shown that, beyond a certain critical number of atoms in the circle, the lifetime of the maximally subradiant state increases exponentially with the number of atoms in the configuration, making the system a natural candidate for a single-photon trap

Influence of atomic ordering on elastocaloric and magnetocaloric effects of a Ni–Cu–Mn–Ga ferromagnetic shape memory alloy

International Nuclear Information System (INIS)

Huang, Chonghui; Wang, Yu; Tang, Zhao; Liao, Xiaoqi; Yang, Sen; Song, Xiaoping

2015-01-01

Highlights: • Ni 51 Cu 4 Mn 20 Ga 25 alloy exhibits normal elastocaloric and magnetocaloric effects. • L2 1 atomic order of the alloy is increased after annealing at 773 K for 10 h. • Increasing L2 1 atomic order improves its elastocaloric and magnetocaloric effects. • Atomic ordering modifies the magnetic and martensitic transitions of the system. - Abstract: The coexisting elastocaloric and magnetocaloric effects in ferromagnetic shape memory alloys have attracted much attention for the potential application in solid state refrigeration. Previous studies show that the L2 1 atomic ordering of Heusler ferromagnetic shape memory alloys plays important role on their magnetocaloric effect. However, no research work investigates the effect of atomic ordering on their elastocaloric effect yet. In this study, we investigated the influence of atomic ordering on the elastocaloric and magnetocaloric effects of a Ni 51 Cu 4 Mn 20 Ga 25 ferromagnetic shape memory alloy. The alloy exhibits normal elastocaloric effect and normal magnetocaloric effect near room temperature. Moreover, we found that the enhancement of atomic order in this alloy can greatly increase the entropy change and refrigeration capacity of its elastocaloric and magnetocaloric effects. This is attributed to that the atomic ordering modifies the magnetic and martensitic transitions of the system

Cancer risk among atomic bomb survivors. The RERF Life Span Study. Radiation Effects Research Foundation

International Nuclear Information System (INIS)

Shimizu, Y.; Schull, W.J.; Kato, H.

1990-01-01

This article summarizes the risk of cancer among the survivors of the atomic bombing of Hiroshima and Nagasaki. We focus primarily on the risk of death from cancer among individuals in the Life Span Study sample of the Radiation Effects Research Foundation from 1950 through 1985 based on recently revised dosimetry procedures. We report the risk of cancer other than leukemia among the atomic bomb survivors. We note that the number of excess deaths of radiation-induced malignant tumors other than leukemia increases with age. Survivors who were exposed in the first or second decade of life have just entered the cancer-prone age and have so far exhibited a high relative risk in association with radiation dose. Whether the elevated risk will continue or will fall with time is not yet clear, although some evidence suggests that the risk may be declining. It is important to continue long-term follow-up of this cohort to document the changes with time since exposure and to provide direct rather than projected risks over the lifetime of an exposed individual

Effects of a static electric field on two-color photoassociation between different atoms

International Nuclear Information System (INIS)

Chakraborty, Debashree; Deb, Bimalendu

2014-01-01

We study non-perturbative effects of a static electric field on two-color photoassociation of different atoms. A static electric field induces anisotropy in scattering between two different atoms and hybridizes field-free rotational states of heteronuclear dimers or polar molecules. In a previous paper [D. Chakraborty et al., J. Phys. B 44, 095201 (2011)], the effects of a static electric field on one-color photoassociation between different atoms has been described through field-modified ground-state scattering states, neglecting electric field effects on heteronuclear diatomic bound states. To study the effects of a static electric field on heteronuclear bound states, and the resulting influence on Raman-type two-color photoassociation between different atoms in the presence of a static electric field, we develop a non-perturbative numerical method to calculate static electric field-dressed heteronuclear bound states. We show that the static electric field induced scattering anisotropy as well as hybridization of rotational states strongly influence two-color photoassociation spectra, leading to significant enhancement in PA rate and large shift. In particular, for static electric field strengths of a few hundred kV/cm, two-color PA rate involving high-lying bound states in electronic ground-state increases by several orders of magnitude even in the weak photoassociative coupling regime

Engineering the Dynamics of Effective Spin-Chain Models for Strongly Interacting Atomic Gases

DEFF Research Database (Denmark)

Volosniev, A. G.; Petrosyan, D.; Valiente, M.

2015-01-01

We consider a one-dimensional gas of cold atoms with strong contact interactions and construct an effective spin-chain Hamiltonian for a two-component system. The resulting Heisenberg spin model can be engineered by manipulating the shape of the external confining potential of the atomic gas. We...

Enhancement of Continuous Variable Entanglement in Four-Wave Mixing due to Atomic Memory Effects

International Nuclear Information System (INIS)

Yu-Zhu, Zhu; Xiang-Ming, Hu; Fei, Wang; Jing-Yan, Li

2010-01-01

We explore the effects of atomic memory on quantum correlations of two-mode light fields from four-wave mixing. A three-level atomic system in Λ configuration is considered, in which the atomic relaxation times are comparable to or longer than the cavity relaxation times and thus there exists the atomic memory. The quantum correlation spectrum in the output is calculated without the adiabatic elimination of atomic variables. It is shown that the continuous variable entanglement is enhanced over a wide range of the normalized detuning in the intermediate and bad cavity cases compared with the good cavity case. In some situations more significant enhancement occurs at sidebands

Cooperatively enhanced dipole forces from artificial atoms in trapped nanodiamonds

Science.gov (United States)

Juan, Mathieu L.; Bradac, Carlo; Besga, Benjamin; Johnsson, Mattias; Brennen, Gavin; Molina-Terriza, Gabriel; Volz, Thomas

2017-03-01

Optical trapping is a powerful tool to manipulate small particles, from micrometre-size beads in liquid environments to single atoms in vacuum. The trapping mechanism relies on the interaction between a dipole and the electric field of laser light. In atom trapping, the dominant contribution to the associated force typically comes from the allowed optical transition closest to the laser wavelength, whereas for mesoscopic particles it is given by the polarizability of the bulk material. Here, we show that for nanoscale diamond crystals containing a large number of artificial atoms, nitrogen-vacancy colour centres, the contributions from both the nanodiamond and the colour centres to the optical trapping strength can be simultaneously observed in a noisy liquid environment. For wavelengths around the zero-phonon line transition of the colour centres, we observe a 10% increase of overall trapping strength. The magnitude of this effect suggests that due to the large density of centres, cooperative effects between the artificial atoms contribute to the observed modification of the trapping strength. Our approach may enable the study of cooperativity in nanoscale solid-state systems and the use of atomic physics techniques in the field of nano-manipulation.

A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms.

Science.gov (United States)

Huo, Ming-Xia; Nie, Wei; Hutchinson, David A W; Kwek, Leong Chuan

2014-08-08

Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a "hairline" solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions.

A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms

Science.gov (United States)

Huo, Ming-Xia; Nie, Wei; Hutchinson, David A. W.; Kwek, Leong Chuan

2014-08-01

Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a ``hairline'' solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions.

Dynamical Evolution of Properties for Atom and Field in the Process of Two-Photon Absorption and Emission Between Atomic Levels

Science.gov (United States)

Wang, Jian-ming; Xu, Xue-xiang

2018-04-01

Using dressed state method, we cleverly solve the dynamics of atom-field interaction in the process of two-photon absorption and emission between atomic levels. Here we suppose that the atom is initially in the ground state and the optical field is initially in Fock state, coherent state or thermal state, respectively. The properties of the atom, including the population in excited state and ground state, the atom inversion, and the properties for optical field, including the photon number distribution, the mean photon number, the second-order correlation function and the Wigner function, are discussed in detail. We derive their analytical expressions and then make numerical analysis for them. In contrast with Jaynes-Cummings model, some similar results, such as quantum Rabi oscillation, revival and collapse, are also exhibit in our considered model. Besides, some novel nonclassical states are generated.

Governing parameters and dynamics of turbulent spray atomization from modern GDI injectors

International Nuclear Information System (INIS)

Moon, Seoksu; Li, Tianyun; Sato, Kiyotaka; Yokohata, Hideaki

2017-01-01

Understanding the governing parameters and dynamics of turbulent spray atomization is essential for the advancement of fuel injection technologies, but no concrete understandings have been derived previously. The current study investigates the governing parameters and dynamics of turbulent spray atomization by experimental observations of near-nozzle spray phenomena using an X-ray imaging technique. The effects of critical injection parameters such as fuel property, injection pressure and ambient density on near-nozzle liquid feature size and velocity distributions were extensively studied using three injection nozzles having different levels of initial flow turbulence and dispersion. Based on the results, the governing parameters and dynamics of turbulent spray atomization and the issues on the advanced fuel injection control of modern engines were thoroughly discussed. The results showed that fuel and injection pressure effects on spray atomization became insignificant from a critical Weber number which decreased upon the increase in initial flow turbulence and dispersion. The increase in ambient density increased the resultant droplet size at downstream due to the faster deceleration of spray which brought the atomization termination location closer to the nozzle exit. The spray atomization was terminated at the location of ca. 72% exit velocity regardless of the injection condition. - Highlights: • Governing parameters and dynamics of turbulent spray atomization are investigated. • Fuel and injection pressure effects on atomization are saturated from critical We. • High ambient density increases drop sizes due to faster termination of atomization. • Atomization terminates when the spray velocity decays to ca. 72% of exit velocity. • Strategies for improvement of current injection technologies are discussed.

Atom diffraction with a 'natural' metastable atom nozzle beam

International Nuclear Information System (INIS)

Karam, J-C; Wipf, N; Grucker, J; Perales, F; Boustimi, M; Vassilev, G; Bocvarski, V; Mainos, C; Baudon, J; Robert, J

2005-01-01

The resonant metastability-exchange process is used to obtain a metastable atom beam with intrinsic properties close to those of a ground-state atom nozzle beam (small angular aperture, narrow velocity distribution). The estimated effective source diameter (15 μm) is small enough to provide at a distance of 597 mm a transverse coherence radius of about 873 nm for argon, 1236 nm for neon and 1660 nm for helium. It is demonstrated both by experiment and numerical calculations with He*, Ne* and Ar* metastable atoms, that this beam gives rise to diffraction effects on the transmitted angular pattern of a silicon-nitride nano-slit grating (period 100 nm). Observed patterns are in good agreement with previous measurements with He* and Ne* metastable atoms. For argon, a calculation taking into account the angular aperture of the beam (0.35 mrad) and the effect of the van der Waals interaction-the van der Waals constant C 3 1.83 +0.1 -0.15 au being derived from spectroscopic data-leads to a good agreement with experiment

For seeing atoms: tunnel effect microscopy

International Nuclear Information System (INIS)

Stoll, E.; Humbert, A.

1985-01-01

A new technique, Scanning Tunneling Microscopy (STM) is described, which allows surface detail to be resolved at atomic level. The principles are described, together with an account of a recent experiment; various theoretical considerations are examined. Samples of recorded topographies are depicted and analysed. It is concluded that the technique is of value for chemical studies of surfaces on an atomic scale. (D.A.J.)

Atomic bomb cataracts

International Nuclear Information System (INIS)

Shiraeda, Kanji

1992-01-01

Eye disturbance caused by atomic bomb radiation can be divided into three groups: direct injury immediately after exposure, eye lesions associated with radiation syndrome, and delayed disturbance. The crystalline lens of the eye is the most radiosensitive. Atomic bomb cataract has been investigated in a number of studies. The first section of this chapter discusses radiation cataract in terms of the incidence and characteristics. The second section deals with atomic bomb cataract, which can be diagnosed based on the four criteria: (1) opacity of the crystalline lens, (2) a history of proximal exposure, (3) lack of eye disease complicating cataract, and (4) non-exposure to radiation other than atomic bombing. The prevalence of cataract and severity of opacity are found to correlate with exposure doses and age at the time of exposure. Furthermore, it is found to correlate with distance from the hypocenter, the condition of shielding, epilation, and the presence or absence or degree of radiation syndrome. (N.K.)

Quantum Electronics for Atomic Physics

CERN Document Server

Nagourney, Warren

2010-01-01

Quantum Electronics for Atomic Physics provides a course in quantum electronics for researchers in atomic physics. The book covers the usual topics, such as Gaussian beams, cavities, lasers, nonlinear optics and modulation techniques, but also includes a number of areas not usually found in a textbook on quantum electronics. It includes such practical matters as the enhancement of nonlinear processes in a build-up cavity, impedance matching into a cavity, laser frequencystabilization (including servomechanism theory), astigmatism in ring cavities, and atomic/molecular spectroscopic techniques

Atom counting in HAADF STEM using a statistical model-based approach: methodology, possibilities, and inherent limitations.

Science.gov (United States)

De Backer, A; Martinez, G T; Rosenauer, A; Van Aert, S

2013-11-01

In the present paper, a statistical model-based method to count the number of atoms of monotype crystalline nanostructures from high resolution high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) images is discussed in detail together with a thorough study on the possibilities and inherent limitations. In order to count the number of atoms, it is assumed that the total scattered intensity scales with the number of atoms per atom column. These intensities are quantitatively determined using model-based statistical parameter estimation theory. The distribution describing the probability that intensity values are generated by atomic columns containing a specific number of atoms is inferred on the basis of the experimental scattered intensities. Finally, the number of atoms per atom column is quantified using this estimated probability distribution. The number of atom columns available in the observed STEM image, the number of components in the estimated probability distribution, the width of the components of the probability distribution, and the typical shape of a criterion to assess the number of components in the probability distribution directly affect the accuracy and precision with which the number of atoms in a particular atom column can be estimated. It is shown that single atom sensitivity is feasible taking the latter aspects into consideration. © 2013 Elsevier B.V. All rights reserved.

Progress in atomic spectroscopy

International Nuclear Information System (INIS)

Beyer, H.J.; Kleinpoppen, H.

1984-01-01

This book presents reviews by leading experts in the field covering areas of research at the forefront of atomic spectroscopy. Topics considered include the k ordering of atomic structure, multiconfiguration Hartree-Fock calculations for complex atoms, new methods in high-resolution laser spectroscopy, resonance ionization spectroscopy (inert atom detection), trapped ion spectroscopy, high-magnetic-field atomic physics, the effects of magnetic and electric fields on highly excited atoms, x rays from superheavy collision systems, recoil ion spectroscopy with heavy ions, investigations of superheavy quasi-atoms via spectroscopy of electron rays and positrons, impact ionization by fast projectiles, and amplitudes and state parameters from ion- and atom-atom excitation processes

Influence of atomic ordering on elastocaloric and magnetocaloric effects of a Ni–Cu–Mn–Ga ferromagnetic shape memory alloy

Energy Technology Data Exchange (ETDEWEB)

Huang, Chonghui [MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter and State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China); Wang, Yu, E-mail: yuwang@mail.xjtu.edu.cn [MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter and State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China); Multi-disciplinary Materials Research Center, Frontier Institute of Science and Technology, Xi’an Jiaotong University, Xi’an 710049 (China); Tang, Zhao; Liao, Xiaoqi; Yang, Sen; Song, Xiaoping [MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter and State Key Laboratory for Mechanical Behavior of Materials, Xi’an Jiaotong University, Xi’an 710049 (China)

2015-05-05

Highlights: • Ni{sub 51}Cu{sub 4}Mn{sub 20}Ga{sub 25} alloy exhibits normal elastocaloric and magnetocaloric effects. • L2{sub 1} atomic order of the alloy is increased after annealing at 773 K for 10 h. • Increasing L2{sub 1} atomic order improves its elastocaloric and magnetocaloric effects. • Atomic ordering modifies the magnetic and martensitic transitions of the system. - Abstract: The coexisting elastocaloric and magnetocaloric effects in ferromagnetic shape memory alloys have attracted much attention for the potential application in solid state refrigeration. Previous studies show that the L2{sub 1} atomic ordering of Heusler ferromagnetic shape memory alloys plays important role on their magnetocaloric effect. However, no research work investigates the effect of atomic ordering on their elastocaloric effect yet. In this study, we investigated the influence of atomic ordering on the elastocaloric and magnetocaloric effects of a Ni{sub 51}Cu{sub 4}Mn{sub 20}Ga{sub 25} ferromagnetic shape memory alloy. The alloy exhibits normal elastocaloric effect and normal magnetocaloric effect near room temperature. Moreover, we found that the enhancement of atomic order in this alloy can greatly increase the entropy change and refrigeration capacity of its elastocaloric and magnetocaloric effects. This is attributed to that the atomic ordering modifies the magnetic and martensitic transitions of the system.

Thoughts on Documentation of Atomic Power Technology

International Nuclear Information System (INIS)

Oh, Jeong Hoon; Lee, Hee Won; Song, Ki Chan

2012-01-01

Korean Atomic Energy Research Institute (KAERI) has accumulated a number of technology development and research outcomes, including its representative achievements such as atomic energy technology independence and the first export of atomic energy system, since it was established in 1959. With its long history of over 50 years, KAERI has produced a large amount of information and explicit knowledge such as experiment data, database, design data, report, instructions, and operation data at each stage of its research and development process as it has performed various researches since its establishment. Also, a lot of tacit knowledge has been produced both knowingly and not unknowingly based on the experience of researchers who have participated in many projects. However, in the research environment in Korea where they focus overly on the output, tacit knowledge has not been managed properly compared to explicit knowledge. This tacit knowledge is as an important asset as explicit knowledge for an effective research and development. Moreover, as the first generation of atomic energy independence and research manpower retire, their accumulated experience and knowledge are in danger of disappearing. Therefore, in this study, we sought how to take a whole view and to document atomic energy technology researched and developed by KAERI, from the background to achievement of each field of the technology. Comprehensive and systematic documentation of atomic energy technology will establish a comprehensive management system of national atomic energy technology record to make a foundation of technical advancement and development of atomic energy technology. Also, it is expected to be used as an important knowledge and information resource of atomic energy knowledge management system

Combined aerodynamic and electrostatic atomization of dielectric liquid jets

Science.gov (United States)

Kourmatzis, Agissilaos; Ergene, Egemen L.; Shrimpton, John S.; Kyritsis, Dimitrios C.; Mashayek, Farzad; Huo, Ming

2012-07-01

The electrical and atomization performance of a plane-plane charge injection atomizer using a dielectric liquid, and operating at pump pressures ranging from 15 to 35 bar corresponding to injection velocities of up to 50 m/s, is explored via low current electrical measurements, spray imaging and phase Doppler anemometry. The work is aimed at understanding the contribution of electrostatic charging relevant to typical higher pressure fuel injection systems such as those employed in the aeronautical, automotive and marine sectors. Results show that mean-specific charge increases with injection velocity significantly. The effect of electrostatic charge is advantageous at the 15-35 bar range, and an arithmetic mean diameter D 10 as low as 0.2 d is achievable in the spray core and lower still in the periphery where d is the orifice diameter. Using the data available from this higher pressure system and from previous high Reynolds number systems (Shrimpton and Yule Exp Fluids 26:460-469, 1999), the promotion of primary atomization has been analysed by examining the effect that charge has on liquid jet surface and liquid jet bulk instability. The results suggest that for the low charge density Q v ~ 2 C/m3 cases under consideration here, a significant increase in primary atomization is observed due to a combination of electrical and aerodynamic forces acting on the jet surface, attributed to the significantly higher jet Weber number ( We j) when compared to low injection pressure cases. Analysis of Sauter mean diameter results shows that for jets with elevated specific charge density of the order Q v ~ 6 C/m3, the jet creates droplets that a conventional turbulent jet would, but with a significantly lower power requirement. This suggests that `turbulent' primary atomization, the turbulence being induced by electrical forces, may be achieved under injection pressures that would produce laminar jets.

The photonics collapse-revival's of intensity-dependent coupling of lambda atoms and fields

International Nuclear Information System (INIS)

Hajivandi, J.; Golshan, M. M.

2007-01-01

In this paper, we extend the intensity-dependent coupling of the interaction of two-level atoms and an electromagnetic field, originated by Sivakumar, to that of Λ-type atoms. In addition, we assume that the interaction occurs in a Kerr medium. In the present model we allow the Λ-type atom to interact with two quantized electromagnetic fields, one of which is initially coherent while the other one is not. We thus report the effect of such coupling and the medium on the collapse-revival's of the photonic mean numbers.

Rapid prototyping of versatile atom chips for atom interferometry applications.

Science.gov (United States)

Kasch, Brian; Squires, Matthew; Olson, Spencer; Kroese, Bethany; Imhof, Eric; Kohn, Rudolph; Stuhl, Benjamin; Schramm, Stacy; Stickney, James

2016-05-01

We present recent advances in the manipulation of ultracold atoms with ex-vacuo atom chips (i.e. atom chips that are not inside to the UHV chamber). Details will be presented of an experimental system that allows direct bonded copper (DBC) atom chips to be removed and replaced in minutes, requiring minimal re-optimization of parameters. This system has been used to create Bose-Einstein condensates, as well as magnetic waveguides with precisely tunable axial parameters, allowing double wells, pure harmonic confinement, and modified harmonic traps. We investigate the effects of higher order magnetic field contributions to the waveguide, and the implications for confined atom interferometry.

Hanbury Brown and Twiss and other atom-atom correlations: advances in quantum atom optics

CERN Multimedia

CERN. Geneva

2008-01-01

Fifty years ago, two astronomers, R. Hanbury Brown and R. Q. Twiss, invented a new method to measure the angular diameter of stars, in spite of the atmospheric fluctuations. Their proposal prompted a hot debate among physicists : how might two particles (photons), emitted independently (at opposite extremities of a star) , behave in a correlated way when detected ? It was only after the development of R Glauber's full quantum analysis that the effect was understood as a two particle quantum interference effect. From a modern perspective, it can be viewed as an early example of the amazing properties of pairs of entangled particles. The effect has now been observed with bosonic and fermionic atoms, stressing its fully quantum character. After putting these experiments in a historical perspective, I will present recent results, and comment on their significance. I will also show how our single atom detection scheme has allowed us to demonstrate the creation of atom pairs by non linear mixing of matter wa...

The abnormal increase of the leukocyte number observed in the inhabitants of Nishiyama area, Nagasaki Prefecture

International Nuclear Information System (INIS)

Honda, Koya

2013-01-01

The Nishiyama area, Nagasaki Prefecture has been known by that the black rain fell after dropping atomic bomb. The abnormal increase of the leukocyte number was measured in the inhabitants of Nishiyama area, Nagasaki Prefecture after dropping atomic bomb. This phenomenon differs from the general knowledge that the leukocyte number decreases by the radiation exposure. This has been noticed as a rare record confirmed by the residual radiation effect to the human body using the group data. (M.H.)

Calculations with the quasirelativistic local-spin-density-functional theory for high-Z atoms

International Nuclear Information System (INIS)

Guo, Y.; Whitehead, M.A.

1988-01-01

The generalized-exchange local-spin-density-functional theory (LSD-GX) with relativistic corrections of the mass velocity and Darwin terms has been used to calculate statistical total energies for the neutral atoms, the positive ions, and the negative ions for high-Z elements. The effect of the correlation and relaxation correction on the statistical total energy is discussed. Comparing the calculated results for the ionization potentials and electron affinities for the atoms (atomic number Z from 37 to 56 and 72 to 80) with experiment, shows that for the atoms rubidium to barium both the LSD-GX and the quasirelativistic LSD-GX, with self-interaction correction, Gopinathan, Whitehead, and Bogdanovic's Fermi-hole parameters [Phys. Rev. A 14, 1 (1976)], and Vosko, Wilk, and Nusair's correlation correction [Can. J. Phys. 58, 1200 (1980)], are very good methods for calculating ionization potentials and electron affinities. For the atoms hafnium to mercury the relativistic effect has to be considered

Mechanism of cluster DNA damage repair in response to high-atomic number and energy particles radiation

Energy Technology Data Exchange (ETDEWEB)

Asaithamby, Aroumougame, E-mail: Aroumougame.Asaithamy@UTsouthwestern.edu [Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390 (United States); Chen, David J., E-mail: David.Chen@UTsouthwestern.edu [Division of Molecular Radiation Biology, Department of Radiation Oncology, University of Texas Southwestern Medical Center at Dallas, Dallas, TX 75390 (United States)

2011-06-03

Low-linear energy transfer (LET) radiation (i.e., {gamma}- and X-rays) induces DNA double-strand breaks (DSBs) that are rapidly repaired (rejoined). In contrast, DNA damage induced by the dense ionizing track of high-atomic number and energy (HZE) particles is slowly repaired or is irreparable. These unrepaired and/or misrepaired DNA lesions may contribute to the observed higher relative biological effectiveness for cell killing, chromosomal aberrations, mutagenesis, and carcinogenesis in HZE particle irradiated cells compared to those treated with low-LET radiation. The types of DNA lesions induced by HZE particles have been characterized in vitro and usually consist of two or more closely spaced strand breaks, abasic sites, or oxidized bases on opposing strands. It is unclear why these lesions are difficult to repair. In this review, we highlight the potential of a new technology allowing direct visualization of different types of DNA lesions in human cells and document the emerging significance of live-cell imaging for elucidation of the spatio-temporal characterization of complex DNA damage. We focus on the recent insights into the molecular pathways that participate in the repair of HZE particle-induced DSBs. We also discuss recent advances in our understanding of how different end-processing nucleases aid in repair of DSBs with complicated ends generated by HZE particles. Understanding the mechanism underlying the repair of DNA damage induced by HZE particles will have important implications for estimating the risks to human health associated with HZE particle exposure.

Mechanism of cluster DNA damage repair in response to high-atomic number and energy particles radiation

International Nuclear Information System (INIS)

Asaithamby, Aroumougame; Chen, David J.

2011-01-01

Low-linear energy transfer (LET) radiation (i.e., γ- and X-rays) induces DNA double-strand breaks (DSBs) that are rapidly repaired (rejoined). In contrast, DNA damage induced by the dense ionizing track of high-atomic number and energy (HZE) particles is slowly repaired or is irreparable. These unrepaired and/or misrepaired DNA lesions may contribute to the observed higher relative biological effectiveness for cell killing, chromosomal aberrations, mutagenesis, and carcinogenesis in HZE particle irradiated cells compared to those treated with low-LET radiation. The types of DNA lesions induced by HZE particles have been characterized in vitro and usually consist of two or more closely spaced strand breaks, abasic sites, or oxidized bases on opposing strands. It is unclear why these lesions are difficult to repair. In this review, we highlight the potential of a new technology allowing direct visualization of different types of DNA lesions in human cells and document the emerging significance of live-cell imaging for elucidation of the spatio-temporal characterization of complex DNA damage. We focus on the recent insights into the molecular pathways that participate in the repair of HZE particle-induced DSBs. We also discuss recent advances in our understanding of how different end-processing nucleases aid in repair of DSBs with complicated ends generated by HZE particles. Understanding the mechanism underlying the repair of DNA damage induced by HZE particles will have important implications for estimating the risks to human health associated with HZE particle exposure.

Investigation of the effective atomic numbers of dosimetric materials for electrons, protons and alpha particles using a direct method in the energy region 10 keV-1 GeV: a comparative study.

Science.gov (United States)

Kurudirek, Murat; Aksakal, Oğuz; Akkuş, Tuba

2015-11-01

A direct method has been used for the first time, to compute effective atomic numbers (Z eff) of water, air, human tissues, and some organic and inorganic compounds, for total electron proton and alpha particle interaction in the energy region 10 keV-1 GeV. The obtained values for Z eff were then compared to those obtained using an interpolation procedure. In general, good agreement has been observed for electrons, and the difference (%) in Z eff between the results of the direct and the interpolation method was found to be energy range from 10 keV to 1 MeV. More specifically, results of the two methods were found to agree well (Dif. energy region with respect to the total electron interaction. On the other hand, values for Z eff calculated using both methods for protons and alpha particles generally agree with each other in the high-energy region above 10 MeV.

Effective field theory for cold atoms

International Nuclear Information System (INIS)

Hammer, H.-W.

2005-01-01

Effective Field Theory (EFT) provides a powerful framework that exploits a separation of scales in physical systems to perform systematically improvable, model-independent calculations. Particularly interesting are few-body systems with short-range interactions and large two-body scattering length. Such systems display remarkable universal features. In systems with more than two particles, a three-body force with limit cycle behavior is required for consistent renormalization already at leading order. We will review this EFT and some of its applications in the physics of cold atoms. Recent extensions of this approach to the four-body system and N-boson droplets in two spatial dimensions will also be discussed

Variable scaling method and Stark effect in hydrogen atom

International Nuclear Information System (INIS)

Choudhury, R.K.R.; Ghosh, B.

1983-09-01

By relating the Stark effect problem in hydrogen-like atoms to that of the spherical anharmonic oscillator we have found simple formulas for energy eigenvalues for the Stark effect. Matrix elements have been calculated using 0(2,1) algebra technique after Armstrong and then the variable scaling method has been used to find optimal solutions. Our numerical results are compared with those of Hioe and Yoo and also with the results obtained by Lanczos. (author)

The Population Inversion and the Entropy of a Moving Two-Level Atom in Interaction with a Quantized Field

Science.gov (United States)

Abo-Kahla, D. A. M.; Abdel-Aty, M.; Farouk, A.

2018-05-01

An atom with only two energy eigenvalues is described by a two-dimensional state space spanned by the two energy eigenstates is called a two-level atom. We consider the interaction between a two-level atom system with a constant velocity. An analytic solution of the systems which interacts with a quantized field is provided. Furthermore, the significant effect of the temperature on the atomic inversion, the purity and the information entropy are discussed in case of the initial state either an exited state or a maximally mixed state. Additionally, the effect of the half wavelengths number of the field-mode is investigated.

Atom chips in the real world: the effects of wire corrugation

Science.gov (United States)

Schumm, T.; Estève, J.; Figl, C.; Trebbia, J.-B.; Aussibal, C.; Nguyen, H.; Mailly, D.; Bouchoule, I.; Westbrook, C. I.; Aspect, A.

2005-02-01

We present a detailed model describing the effects of wire corrugation on the trapping potential experienced by a cloud of atoms above a current carrying micro wire. We calculate the distortion of the current distribution due to corrugation and then derive the corresponding roughness in the magnetic field above the wire. Scaling laws are derived for the roughness as a function of height above a ribbon shaped wire. We also present experimental data on micro wire traps using cold atoms which complement some previously published measurements [CITE] and which demonstrate that wire corrugation can satisfactorily explain our observations of atom cloud fragmentation above electroplated gold wires. Finally, we present measurements of the corrugation of new wires fabricated by electron beam lithography and evaporation of gold. These wires appear to be substantially smoother than electroplated wires.

Atom-by-atom assembly

International Nuclear Information System (INIS)

Hla, Saw Wai

2014-01-01

Atomic manipulation using a scanning tunneling microscope (STM) tip enables the construction of quantum structures on an atom-by-atom basis, as well as the investigation of the electronic and dynamical properties of individual atoms on a one-atom-at-a-time basis. An STM is not only an instrument that is used to ‘see’ individual atoms by means of imaging, but is also a tool that is used to ‘touch’ and ‘take’ the atoms, or to ‘hear’ their movements. Therefore, the STM can be considered as the ‘eyes’, ‘hands’ and ‘ears’ of the scientists, connecting our macroscopic world to the exciting atomic world. In this article, various STM atom manipulation schemes and their example applications are described. The future directions of atomic level assembly on surfaces using scanning probe tips are also discussed. (review article)

Analysis of the physical atomic forces between noble gas atoms, alkali ions and halogen ions

Science.gov (United States)

Wilson, J. W.; Heinbockel, J. H.; Outlaw, R. A.

1986-01-01

The physical forces between atoms and molecules are important in a number of processes of practical importance, including line broadening in radiative processes, gas and crystal properties, adhesion, and thin films. The components of the physical forces between noble gas atoms, alkali ions, and halogen ions are analyzed and a data base for the dispersion forces is developed from the literature based on evaluations with the harmonic oscillator dispersion model for higher order coefficients. The Zener model of the repulsive core is used in the context of the recent asymptotic wave functions of Handler and Smith; and an effective ionization potential within the Handler and Smith wave functions is defined to analyze the two body potential data of Waldman and Gordon, the alkali-halide molecular data, and the noble gas crystal and salt crystal data. A satisfactory global fit to this molecular and crystal data is then reproduced by the model to within several percent. Surface potentials are evaluated for noble gas atoms on noble gas and salt crystal surfaces with surface tension neglected. Within this context, the noble gas surface potentials on noble gas and salt crystals are considered to be accurate to within several percent.

Atoms in Flight: The Remarkable Connections between Atomic and Hadronic Physics

Energy Technology Data Exchange (ETDEWEB)

Brodsky, Stanley J.; /SLAC

2012-02-16

Atomic physics and hadron physics are both based on Yang Mills gauge theory; in fact, quantum electrodynamics can be regarded as the zero-color limit of quantum chromodynamics. I review a number of areas where the techniques of atomic physics provide important insight into the theory of hadrons in QCD. For example, the Dirac-Coulomb equation, which predicts the spectroscopy and structure of hydrogenic atoms, has an analog in hadron physics in the form of light-front relativistic equations of motion which give a remarkable first approximation to the spectroscopy, dynamics, and structure of light hadrons. The renormalization scale for the running coupling, which is unambiguously set in QED, leads to a method for setting the renormalization scale in QCD. The production of atoms in flight provides a method for computing the formation of hadrons at the amplitude level. Conversely, many techniques which have been developed for hadron physics, such as scaling laws, evolution equations, and light-front quantization have equal utility for atomic physics, especially in the relativistic domain. I also present a new perspective for understanding the contributions to the cosmological constant from QED and QCD.

Matter, energy, and heat transfer in a classical ballistic atom pump.

Science.gov (United States)

Byrd, Tommy A; Das, Kunal K; Mitchell, Kevin A; Aubin, Seth; Delos, John B

2014-11-01

A ballistic atom pump is a system containing two reservoirs of neutral atoms or molecules and a junction connecting them containing a localized time-varying potential. Atoms move through the pump as independent particles. Under certain conditions, these pumps can create net transport of atoms from one reservoir to the other. While such systems are sometimes called "quantum pumps," they are also models of classical chaotic transport, and their quantum behavior cannot be understood without study of the corresponding classical behavior. Here we examine classically such a pump's effect on energy and temperature in the reservoirs, in addition to net particle transport. We show that the changes in particle number, of energy in each reservoir, and of temperature in each reservoir vary in unexpected ways as the incident particle energy is varied.

Atom dynamics in laser fields

International Nuclear Information System (INIS)

Jang, Su; Mi, No Gin

2004-12-01

This book introduces coherent dynamics of internal state, spread of atoms wave speed, semiclassical atoms density matrix such as dynamics equation in both still and moving atoms, excitation of atoms in movement by light, dipole radiating power, quantum statistical mechanics by atoms in movement, semiclassical atoms in movement, atoms in movement in the uniform magnetic field including effects of uniform magnetic field, atom cooling using laser such as Doppler cooling, atom traps using laser and mirrors, radiant heat which particles receive, and near field interactions among atoms in laser light.

Number series of atoms, interatomic bonds and interface bonds defining zinc-blende nanocrystals as function of size, shape and surface orientation: Analytic tools to interpret solid state spectroscopy data

Energy Technology Data Exchange (ETDEWEB)

König, Dirk, E-mail: dirk.koenig@unsw.edu.au [Integrated Materials Design Centre (IMDC) and School of Photovoltaic and Renewable Energy Engineering (SPREE), University of New South Wales, Sydney (Australia)

2016-08-15

Semiconductor nanocrystals (NCs) experience stress and charge transfer by embedding materials or ligands and impurity atoms. In return, the environment of NCs experiences a NC stress response which may lead to matrix deformation and propagated strain. Up to now, there is no universal gauge to evaluate the stress impact on NCs and their response as a function of NC size d{sub NC}. I deduce geometrical number series as analytical tools to obtain the number of NC atoms N{sub NC}(d{sub NC}[i]), bonds between NC atoms N{sub bnd}(d{sub NC}[i]) and interface bonds N{sub IF}(d{sub NC}[i]) for seven high symmetry zinc-blende (zb) NCs with low-index faceting: {001} cubes, {111} octahedra, {110} dodecahedra, {001}-{111} pyramids, {111} tetrahedra, {111}-{001} quatrodecahedra and {001}-{111} quadrodecahedra. The fundamental insights into NC structures revealed here allow for major advancements in data interpretation and understanding of zb- and diamond-lattice based nanomaterials. The analytical number series can serve as a standard procedure for stress evaluation in solid state spectroscopy due to their deterministic nature, easy use and general applicability over a wide range of spectroscopy methods as well as NC sizes, forms and materials.

Design considerations regarding an atomizer for multi-element electrothermal atomic absorption spectrometry

Energy Technology Data Exchange (ETDEWEB)

Katskov, Dmitri A., E-mail: katskovda@tut.ac.za [Department of Chemistry, Tshwane University of Technology, Private Bag X680, Pretoria 0001 (South Africa); Sadagov, Yuri M. [All-Russian Scientific Research Institute of Optical and Physical Measurements (VNIIOFI), Ozernaya St. 46, Moscow 119361 (Russian Federation)

2011-06-15

The methodology of simultaneous multi-element electrothermal atomic absorption spectrometry (ETAAS-Electrothermal Atomic Absorption Spectrometry) stipulates rigid requirements to the design and operation of the atomizer. It must provide high degree of atomization for the group of analytes, invariant respective to the vaporization kinetics and heating ramp residence time of atoms in the absorption volume and absence of memory effects from major sample components. For the low resolution spectrometer with a continuum radiation source the reduced compared to traditional ETAAS (Electrothermal Atomic Absorption Spectrometry) sensitivity should be, at least partially, compensated by creating high density of atomic vapor in the absorption pulse. The sought-for characteristics were obtained for the 18 mm in length and 2.5 mm in internal diameter longitudinally heated graphite tube atomizer furnished with 2-4.5 mg of ring shaped carbon fiber yarn collector. The collector located next to the sampling port provides large substrate area that helps to keep the sample and its residue in the central part of the tube after drying. The collector also provides a 'platform' effect that delays the vaporization and stipulates vapor release into absorption volume having already stabilized gas temperature. Due to the shape of external surface of the tube, presence of collector and rapid (about 10 {sup o}C/ms) heating, an inverse temperature distribution along the tube is attained at the beginnings of the atomization and cleaning steps. The effect is employed for cleaning of the atomizer using the set of short maximum power heating pulses. Preparation, optimal maintenance of the atomizer and its compliance to the multi-element determination requirements are evaluated and discussed. The experimental setup provides direct simultaneous determination of large group of element within 3-4 order concentration range. Limits of detection are close to those for sequential single element

Effects impeding the observation of weak neutral interaction between muons and nuclei in light mesic atoms

International Nuclear Information System (INIS)

Grechukhin, D.P.; Soldatov, A.A.

1977-01-01

The intensity of the satellite lines of the 2s1/2→1s1/2 radiative transition in a mesic atom due to configurational interaction between the meson and shell electrons of the mesic atom is estimated. The intensity of these satellite lines is shown to be about six orders of magnitude greater than the intensity of the emission in the 2s1/2→1s1/2 meson transition. Configurational interaction between the meson and conductivity band electrons in metals precludes the usage of a metal target for stopping the mesons in the experiment. Estimates show that for mesic atoms produced in a gas the Stark effect of the electric dipole field induced in collisions between atoms of the medium and a mesic atom (Z>=2) stripped of electrons significantly restricts the density of the medium from above such that the density is 14 at/cm 3 ; in the case of the Stark effect of the intra-atomic field and collisions between a μH atom and atoms of the medium the corresponding value is 11 at/cm 3

An investigation on effect of geometrical parameters on spray cone angle and droplet size distribution of a two-fluid atomizer

Energy Technology Data Exchange (ETDEWEB)

Shafaee, Maziar; Banitabaei, Sayed Abdolhossein; Esfahanian, Vahid; Ashjaee, Mehdi [Tehran University, Tehran (Iran, Islamic Republic of)

2011-12-15

A visual study is conducted to determine the effect of geometrical parameters of a two-fluid atomizer on its spray cone angle. The liquid (water) jets exit from six peripheral inclined orifices and are introduced to a high speed gas (air) stream in the gravitational direction. Using a high speed imaging system, the spray cone angle has been determined in constant operational conditions, i.e., Reynolds and Weber numbers for different nozzle geometries. Also, the droplet sizes (Sauter mean diameter) and their distributions have been determined using Malvern Master Sizer x. The investigated geometrical parameters are the liquid jet diameter, liquid port angle and the length of the gas-liquid mixing chamber. The results show that among these parameters, the liquid jet diameter has a significant effect on spray cone angle. In addition, an empirical correlation has been obtained to predict the spray cone angle of the present two-fluid atomizer in terms of nozzle geometries.

Disorder effect on heat capacity, self-diffusion coefficient, and choosing best potential model for melting temperature, in gold–copper bimetallic nanocluster with 55 atoms

International Nuclear Information System (INIS)

Taherkhani, Farid; Akbarzadeh, Hamed; Feyzi, Mostafa; Rafiee, Hamid Reza

2015-01-01

Molecular dynamics simulation has been implemented for doping effect on melting temperature, heat capacity, self-diffusion coefficient of gold–copper bimetallic nanostructure with 55 total gold and copper atom numbers and its bulk alloy. Trend of melting temperature for gold–copper bimetallic nanocluster is not same as melting temperature copper–gold bulk alloy. Molecular dynamics simulation of our result regarding bulk melting temperature is consistence with available experimental data. Molecular dynamics simulation shows that melting temperature of gold–copper bimetallic nanocluster increases with copper atom fraction. Semi-empirical potential model and quantum Sutton–Chen potential models do not change melting temperature trend with copper doping of gold–copper bimetallic nanocluster. Self-diffusion coefficient of copper atom is greater than gold atom in gold–copper bimetallic nanocluster. Semi-empirical potential within the tight-binding second moment approximation as new application potential model for melting temperature of gold–copper bulk structure shows better result in comparison with EAM, Sutton–Chen potential, and quantum Sutton–Chen potential models

Disorder effect on heat capacity, self-diffusion coefficient, and choosing best potential model for melting temperature, in gold–copper bimetallic nanocluster with 55 atoms

Energy Technology Data Exchange (ETDEWEB)

Taherkhani, Farid, E-mail: faridtaherkhani@gmail.com, E-mail: f.taherkhani@razi.ac.ir [Razi University, Department of Physical Chemistry (Iran, Islamic Republic of); Akbarzadeh, Hamed [Hakim Sabzevari University, Department of Chemistry (Iran, Islamic Republic of); Feyzi, Mostafa; Rafiee, Hamid Reza [Razi University, Department of Physical Chemistry (Iran, Islamic Republic of)

2015-01-15

Molecular dynamics simulation has been implemented for doping effect on melting temperature, heat capacity, self-diffusion coefficient of gold–copper bimetallic nanostructure with 55 total gold and copper atom numbers and its bulk alloy. Trend of melting temperature for gold–copper bimetallic nanocluster is not same as melting temperature copper–gold bulk alloy. Molecular dynamics simulation of our result regarding bulk melting temperature is consistence with available experimental data. Molecular dynamics simulation shows that melting temperature of gold–copper bimetallic nanocluster increases with copper atom fraction. Semi-empirical potential model and quantum Sutton–Chen potential models do not change melting temperature trend with copper doping of gold–copper bimetallic nanocluster. Self-diffusion coefficient of copper atom is greater than gold atom in gold–copper bimetallic nanocluster. Semi-empirical potential within the tight-binding second moment approximation as new application potential model for melting temperature of gold–copper bulk structure shows better result in comparison with EAM, Sutton–Chen potential, and quantum Sutton–Chen potential models.

Determination of Atomic Number Exponent for Elemental Absorber at Am-241 Energy in X-Ray Attenuation Experiments

International Nuclear Information System (INIS)

Najim, L.A.; Shamoon, S.K.; Atalah, S.T.

2012-01-01

In X-ray absorption experiment, the dependence of the photoelectric absorption cross-section varied with atomic number Z.In this paper, the dependence on Z of the cross-section or coefficient of photoelectric absorption is first evaluated from published data for (20) elements ranging from Al-Sn, and then the cross-section for Fe is obtained experimentally by measuring the X-ray intensity with and without the Fe absorber and compared with the theoretical value, the variation of the photoelectric absorption coefficient (μ/ρ m ) showed less dependence on Z for the two tested of Z regions.This is because of the inclusion of mass density (ρ m ) of the absorber in the coefficient.The values of m obtained in the present work increases linearly with energy for both ranges of elements

Variation of the binary encounter peak energy as a function of projectile atomic number

International Nuclear Information System (INIS)

Sanders, J.M.

1994-01-01

The energy of the binary encounter peak, in spectra of electrons emitted at 0 degrees with respect to the projectile beam direction, has been studied to investigate its dependence on the atomic number of the projectile ion. The projectiles all had the same squared velocity of 0.6 MeV/u, and all had the same charge q=7. The Z of the projectiles ranged from 8 to 35, and the target was H 2 . The Energy E BEP of the binary encounter peak and also the energy t of the cusp formed by electron loss or electron capture to the projectile continuum (ELC or ECC) were obtained from fits to the spectra. Considerable care was required in fitting the cusp in order to properly ascertain the cusp energy. The energy shift ΔE, defined as the difference between 4t and E BEP , was obtained for each projectile. It is found that the energy shift decreases as the projectile Z increases. This trend is the opposite of that seen for projectile charge where the shift increases as q increases. Such a trend is not well described by the simple elastic scattering model of binary encounter electron production

Medical exposure assessment: the global approach of the United Nations Scientific Committee on the Effects of Atomic Radiation

International Nuclear Information System (INIS)

Shannoun, F.

2015-01-01

The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) was established in 1955 to systematically collect, evaluate, publish and share data on the global levels and effects of ionizing radiation from natural and artificial sources. Regular surveys have been conducted to determinate the frequencies of medical radiological procedure, the number of equipment and staffing and the level of global exposure using the health care level (HCL) extrapolation model. UNSCEAR surveys revealed a range of issues relating to participation, survey process, data quality and analysis. Thus, UNSCEAR developed an improvement strategy to address the existing deficiencies in data quality and collection. The major element of this strategy is the introduction of an on-line platform to facilitate the data collection and archiving process. It is anticipated that the number of countries participating in UNSCEAR's surveys will increase in the future, particularly from HCL II -IV countries. (authors)

Effect of local atomic and electronic structures on thermoelectric properties of chemically substituted CoSi

Science.gov (United States)

Hsu, C. C.; Pao, C. W.; Chen, J. L.; Chen, C. L.; Dong, C. L.; Liu, Y. S.; Lee, J. F.; Chan, T. S.; Chang, C. L.; Kuo, Y. K.; Lue, C. S.

2014-05-01

We report the effects of Ge partial substitution for Si on local atomic and electronic structures of thermoelectric materials in binary compound cobalt monosilicides (\\text{CoSi}_{1-x}\\text{Ge}_{x}\\text{:}\\ 0 \\le x \\le 0.15 ). Correlations between local atomic/electronic structure and thermoelectric properties are investigated by means of X-ray absorption spectroscopy. The spectroscopic results indicate that as Ge is partially substituted onto Si sites at x \\le 0.05 , Co in CoSi1-xGex gains a certain amount of charge in its 3d orbitals. Contrarily, upon further replacing Si with Ge at x \\ge 0.05 , the Co 3d orbitals start to lose some of their charge. Notably, thermopower is strongly correlated with charge redistribution in the Co 3d orbital, and the observed charge transfer between Ge and Co is responsible for the variation of Co 3d occupancy number. In addition to Seebeck coefficient, which can be modified by tailoring the Co 3d states, local lattice disorder may also be beneficial in enhancing the thermoelectric properties. Extended X-ray absorption fine structure spectrum results further demonstrate that the lattice phonons can be enhanced by Ge doping, which results in the formation of the disordered Co-Co pair. Improvements in the thermoelectric properties are interpreted based on the variation of local atomic and electronic structure induced by lattice distortion through chemical substitution.

Description of atomic burials in compact globular proteins by Fermi-Dirac probability distributions.

Science.gov (United States)

Gomes, Antonio L C; de Rezende, Júlia R; Pereira de Araújo, Antônio F; Shakhnovich, Eugene I

2007-02-01

We perform a statistical analysis of atomic distributions as a function of the distance R from the molecular geometrical center in a nonredundant set of compact globular proteins. The number of atoms increases quadratically for small R, indicating a constant average density inside the core, reaches a maximum at a size-dependent distance R(max), and falls rapidly for larger R. The empirical curves turn out to be consistent with the volume increase of spherical concentric solid shells and a Fermi-Dirac distribution in which the distance R plays the role of an effective atomic energy epsilon(R) = R. The effective chemical potential mu governing the distribution increases with the number of residues, reflecting the size of the protein globule, while the temperature parameter beta decreases. Interestingly, betamu is not as strongly dependent on protein size and appears to be tuned to maintain approximately half of the atoms in the high density interior and the other half in the exterior region of rapidly decreasing density. A normalized size-independent distribution was obtained for the atomic probability as a function of the reduced distance, r = R/R(g), where R(g) is the radius of gyration. The global normalized Fermi distribution, F(r), can be reasonably decomposed in Fermi-like subdistributions for different atomic types tau, F(tau)(r), with Sigma(tau)F(tau)(r) = F(r), which depend on two additional parameters mu(tau) and h(tau). The chemical potential mu(tau) affects a scaling prefactor and depends on the overall frequency of the corresponding atomic type, while the maximum position of the subdistribution is determined by h(tau), which appears in a type-dependent atomic effective energy, epsilon(tau)(r) = h(tau)r, and is strongly correlated to available hydrophobicity scales. Better adjustments are obtained when the effective energy is not assumed to be necessarily linear, or epsilon(tau)*(r) = h(tau)*r(alpha,), in which case a correlation with hydrophobicity

Symmetric Atom–Atom and Ion–Atom Processes in Stellar Atmospheres

Directory of Open Access Journals (Sweden)

Vladimir A. Srećković

2017-12-01

Full Text Available We present the results of the influence of two groups of collisional processes (atom–atom and ion–atom on the optical and kinetic properties of weakly ionized stellar atmospheres layers. The first type includes radiative processes of the photodissociation/association and radiative charge exchange, the second one the chemi-ionisation/recombination processes with participation of only hydrogen and helium atoms and ions. The quantitative estimation of the rate coefficients of the mentioned processes were made. The effect of the radiative processes is estimated by comparing their intensities with those of the known concurrent processes in application to the solar photosphere and to the photospheres of DB white dwarfs. The investigated chemi-ionisation/recombination processes are considered from the viewpoint of their influence on the populations of the excited states of the hydrogen atom (the Sun and an M-type red dwarf and helium atom (DB white dwarfs. The effect of these processes on the populations of the excited states of the hydrogen atom has been studied using the general stellar atmosphere code, which generates the model. The presented results demonstrate the undoubted influence of the considered radiative and chemi- ionisation/recombination processes on the optical properties and on the kinetics of the weakly ionized layers in stellar atmospheres.

Photoionization dynamics of excited Ne, Ar, Kr and Xe atoms near threshold

International Nuclear Information System (INIS)

Sukhorukov, V L; Petrov, I D; Schäfer, M; Merkt, F; Ruf, M-W; Hotop, H

2012-01-01

A review of experimental and theoretical studies of the threshold photoionization of the heavier rare-gas atoms is presented, with particular emphasis on the autoionization resonances in the spectral region between the lowest two ionization thresholds 2 P 3/2 and 2 P 1/2 , accessed from the ground or excited states. Observed trends in the positions, widths and shapes of the autoionization resonances depending on the atomic number, the principal quantum number n, the orbital angular momentum quantum number ℓ and further quantum numbers specifying the fine- and hyperfine-structure levels are summarized and discussed in the light of ab initio and multichannel quantum defect theory calculations. The dependence of the photoionization spectra on the initially prepared neutral state are also discussed, including results on the photoionization cross sections and photoelectron angular distributions of polarized excited states. The effects of various approximations in the theoretical treatment of photoionization in these systems are analysed. The very large diversity of observed phenomena and the numerous anomalies in spectral structures associated with the threshold ionization of the rare-gas atoms can be described in terms of a limited set of interactions and dynamical processes. Examples are provided illustrating characteristic aspects of the photoionization, and sets of recommended parameters describing the energy-level structure and photoionization dynamics of the rare-gas atoms are presented which were extracted in a critical analysis of the very large body of experimental and theoretical data available on these systems in the literature. (topical review)

Effects of finite temperature on two-photon transitions in a Rydberg atom in a high-Q cavity

International Nuclear Information System (INIS)

Puri, R.R.; Joshi, A.

1989-01-01

The effects of cavity temperature on an effective two-level atom undergoing two-photon transitions in a high-Q cavity are investigated. The quantum statistical properties of the field and the dynamical properties of the atom in this case are studied and compared with those for an atom making one-photon transitions between the two levels. The analysis is based on the solution of the equation for the density matrix in the secular approximation which is known to be a valid approximation in the case of a Rydberg atom in a high-Q cavity. (orig.)

Orbital alignment effects in near-resonant Rydberg atoms-rare gas collisions

International Nuclear Information System (INIS)

Isaacs, W.A.; Morrison, M.A.

1993-01-01

Recent experimental and theoretical studies of near-resonant energy transfer collisions involving rare-gas atoms and alkali or alkaline earth atoms which have been initially excited to an aligned state via one or more linearly polarized rasters have yielded a wealth of insight into orbital alignment and related effects. We have extended this inquiry to initially aligned Rydberg states, examining state-to-state and alignment-selected cross sections using quantum collision theory augmented by approximations appropriate to the special characteristics of the Rydberg state (e.g., the quasi-free-electron model and the impulse approximation)

Effect of atomic initial phase difference on spontaneous emission of an atom embedded in photonic crystal

International Nuclear Information System (INIS)

Bing, Zhang; Xiu-Dong, Sun; Xiang-Qian, Jiang

2010-01-01

We investigate the effect of initial phase difference between the two excited states of a V-type three-level atom on its steady state behaviour of spontaneous emission. A modified density of modes is introduced to calculate the spontaneous emission spectra in photonic crystal. Spectra in free space are also shown to compare with that in photonic crystal with different relative positions of the excited levels from upper band-edge frequency. It is found that the initial phase difference plays an important role in the quantum interference property between the two decay channels. For a zero initial phase, destructive property is presented in the spectra. With the increase of initial phase difference, quantum interference between the two decay channels from upper levels to ground level turns to be constructive. Furthermore, we give an interpretation for the property of these spectra. (atomic and molecular physics)

Transient localization in the kicked Rydberg atom

OpenAIRE

Persson, E.; Fürthauer, S.; Wimberger, S.; Burgdörfer, J.

2006-01-01

We investigate the long-time limit of quantum localization of the kicked Rydberg atom. The kicked Rydberg atom is shown to possess in addition to the quantum localization time $\\tau_L$ a second cross-over time $t_D$ where quantum dynamics diverges from classical dynamics towards increased instability. The quantum localization is shown to vanish as either the strength of the kicks at fixed principal quantum number or the quantum number at fixed kick strength increases. The survival probability...

AtomDB: Expanding an Accessible and Accurate Atomic Database for X-ray Astronomy

Science.gov (United States)

Smith, Randall

Since its inception in 2001, the AtomDB has become the standard repository of accurate and accessible atomic data for the X-ray astrophysics community, including laboratory astrophysicists, observers, and modelers. Modern calculations of collisional excitation rates now exist - and are in AtomDB - for all abundant ions in a hot plasma. AtomDB has expanded beyond providing just a collisional model, and now also contains photoionization data from XSTAR as well as a charge exchange model, amongst others. However, building and maintaining an accurate and complete database that can fully exploit the diagnostic potential of high-resolution X-ray spectra requires further work. The Hitomi results, sadly limited as they were, demonstrated the urgent need for the best possible wavelength and rate data, not merely for the strongest lines but for the diagnostic features that may have 1% or less of the flux of the strong lines. In particular, incorporation of weak but powerfully diagnostic satellite lines will be crucial to understanding the spectra expected from upcoming deep observations with Chandra and XMM-Newton, as well as the XARM and Athena satellites. Beyond incorporating this new data, a number of groups, both experimental and theoretical, have begun to produce data with errors and/or sensitivity estimates. We plan to use this to create statistically meaningful spectral errors on collisional plasmas, providing practical uncertainties together with model spectra. We propose to continue to (1) engage the X-ray astrophysics community regarding their issues and needs, notably by a critical comparison with other related databases and tools, (2) enhance AtomDB to incorporate a large number of satellite lines as well as updated wavelengths with error estimates, (3) continue to update the AtomDB with the latest calculations and laboratory measurements, in particular velocity-dependent charge exchange rates, and (4) enhance existing tools, and create new ones as needed to

Atomic theory of viscoelastic response and memory effects in metallic glasses

Science.gov (United States)

Cui, Bingyu; Yang, Jie; Qiao, Jichao; Jiang, Minqiang; Dai, Lanhong; Wang, Yun-Jiang; Zaccone, Alessio

2017-09-01

An atomic-scale theory of the viscoelastic response of metallic glasses is derived from first principles, using a Zwanzig-Caldeira-Leggett system-bath Hamiltonian as a starting point within the framework of nonaffine linear response to mechanical deformation. This approach provides a generalized Langevin equation (GLE) as the average equation of motion for an atom or ion in the material, from which non-Markovian nonaffine viscoelastic moduli are extracted. These can be evaluated using the vibrational density of states (DOS) as input, where the boson peak plays a prominent role in the mechanics. To compare with experimental data for binary ZrCu alloys, a numerical DOS was obtained from simulations of this system, which also take electronic degrees of freedom into account via the embedded-atom method for the interatomic potential. It is shown that the viscoelastic α -relaxation, including the α -wing asymmetry in the loss modulus, can be very well described by the theory if the memory kernel (the non-Markovian friction) in the GLE is taken to be a stretched-exponential decaying function of time. This finding directly implies strong memory effects in the atomic-scale dynamics and suggests that the α -relaxation time is related to the characteristic time scale over which atoms retain memory of their previous collision history. This memory time grows dramatically below the glass transition.

Coherent control and storage of a microwave pulse in a one-dimensional array of artificial atoms using the Autler-Townes effect and electromagnetically induced transparency

Science.gov (United States)

Ayaz, M. Q.; Waqas, Mohsin; Qamar, Sajid; Qamar, Shahid

2018-02-01

In this paper we propose a scheme for coherent control and storage of a microwave pulse in superconducting circuits exploiting the idea of electromagnetically induced transparency (EIT) and the Aulter-Townes (AT) effect. We show that superconducting artificial atoms in a four-level tripod configuration act as EIT based coherent microwave (μ w ) memories with gain features, when they are attached to a one-dimensional transmission line. These atoms are allowed to interact with three microwave fields, such that there are two control fields and one probe field. Our proposed system works in such a way that one control field with large Rabi frequency when interacting with atoms, produces the AT effect. While the second control field with relatively small Rabi frequency produces EIT in one of the absorption windows produced due to the AT splitting for the weak probe field. The group velocity of the probe pulse reduces significantly through this EIT window. Interestingly, the output intensity of the probe pulse increases as we increase the number of artificial atoms. Our results show that the probe microwave pulse can be stored and retrieved with high fidelity.

Atom-probe field-ion-microscope mass spectrometer

International Nuclear Information System (INIS)

Nishikawa, Osamu

1983-01-01

The titled analyzer, called simply atom-probe, has been developed by combining a field ion microscope (FIM) and a mass spectrometer, and is divided into the time-of-flight type, magnetic sector type, and quadrupole type depending on the types of mass spectrometers. In this paper, the author first describes on the principle and construction of a high resolution, time-of-flight atom-probe developed and fabricated in his laboratory. The feature of the atom-probe lies in the analysis of atoms and molecules in hyper-fine structure region one by one utilizing the high resolution of FIM. It also has the advantages of directly determining the composition by a ratio of the numbers of respective ions because of a constant detection sensitivity regardless of mass numbers, of the resolution as high as single atom layer in depth direction, and of detecting the positional relationship among detected ions by the order of detection in a sample. To determine the composition in a hyperfine structure region, the limited small number of atoms and molecules in the region must be identified distinctly one by one. In the analyzed result of Ni-silicide formed by heating Si evaporated on a Ni tip at 1000 K for 5 minutes, each isotope was not only clearly separated, but also their abundance ratio was very close to the natural abundance ratio. The second half of the paper reports on the analysis of TiC promising for a cold cathode material, adsorption of CO and alcohol, and the composition and structure of silicides, as a few application examples. (Wakatsuki, Y.)

The effect of carbon nanotube chirality on the spiral flow of copper atoms in their cores

International Nuclear Information System (INIS)

Lim, M.C.G.; Zhong, Z.W.

2012-01-01

The effect of carbon nanotube (CNT) chirality on the flow of copper atoms along its core has been investigated using molecular dynamics simulations. The investigation is conducted using CNTs of different chirality, and different flow conditions such as temperatures, bias voltages and the initial positions of the copper atoms. The results show that the atoms flow in a spiral fashion along the CNT channels. The effect is most evident in the CNT channel with zigzag CNTs. The movement of the copper atoms is more erratic when the temperature is increased at a low biased voltage, regardless of the types of channel used. The initial positions of the copper atoms affect the way they converge as they move downstream along the channel. A bias voltage of 4 V favours the initiation of a spiral flow, especially when the position of the copper atoms is far from the central axis of the channel. -- Highlights: ► We model the transportation of copper atoms in armchair and zigzag CNT channels. ► The spiral flow of copper atoms occurs in a semiconductor–semiconductor CNT. ► The compact copper mass is predicted to occur at 673 K with a 4 V bias voltage.

Atomic Oxygen Treatment and Its Effect on a Variety of Artist's Media

Science.gov (United States)

Miller, Sharon K. R.; Banks, Bruce A.; Waters, Deborah L.

2005-01-01

Atomic oxygen treatment has been investigated as an unconventional option for art restoration where conventional methods have not been effective. Exposure of surfaces to atomic oxygen was first performed to investigate the durability of materials in the low Earth orbit environment of space. The use of the ground based environmental simulation chambers, developed for atomic oxygen exposure testing, has been investigated in collaboration with conservators at a variety of institutions, as a method to clean the surfaces of works of art. The atomic oxygen treatment technique has been evaluated as a method to remove soot and char from the surface of oil paint (both varnished and unvarnished), watercolors, acrylic paint, and fabric as well as the removal of graffiti and other marks from surfaces which are too porous to lend themselves to conventional solvent removal techniques. This paper will discuss the treatment of these surfaces giving an example of each and a discussion of the treatment results.

Electron population uncertainty and atomic covalency

International Nuclear Information System (INIS)

Chesnut, D.B.

2006-01-01

The atoms-in-molecules (AIM) index of atomic covalency is directly related to the AIM atomic population uncertainty. The covalent bond order, delocalization index, and, therefore, the atomic covalency are maximal when electron pairs are equally shared by the atoms involved. When polarization effects are present, these measures of covalent bond character decrease. We present atomic covalences for the single- and double-heavy atom hydrides of elements of the first and second low rows of the periodic table to illustrate these effects. Some usual behavior is seen in hydrogen-bridged species due in some cases to stronger than expected multicenter bonds and in other cases to many atoms contributing to the covalency index

Use of pseudopotentials in atom-atom (or molecule) collisions

International Nuclear Information System (INIS)

Pascale, J.

1985-09-01

Knowledge of interactions between ions, atoms or molecules is fundamental for interpretating or predicting collisional processes which may occur under various circumstances. The aim of this paper is to demonstrate the usefulness of using semiempirical effective interactions (more particularly, emphasis will be put on the pseudopotential approach) in the study of atom-atom (or molecule) collisions. We would like to show that if the semiempirical effective interactions are carefully defined, their use in molecular-structure calculations and in collision problems can give quite accurate results. We will limit our examples to one-electron systems. We consider the M-atom-He systems as a first example. For these systems, recent molecular-structure calculations have been carried out using an 1-dependent semiempirical pseudopotential approach and they have been tested against numerous experimental data in extensive calculations of cross sections for intra-and-inter-doublet transitions in the M-atom in collisions with He. Our second example will concern the M-H 2 systems, for which semiempirical pseudopotential molecular-structure calculations have been performed very recently using an one-electron two-center model. The results of these calculations are quite encouraging and we foresee the use of the pseudopotential approach in future studies of some reactive scattering processes

Study on Droplet Size and Velocity Distributions of a Pressure Swirl Atomizer Based on the Maximum Entropy Formalism

Directory of Open Access Journals (Sweden)

Kai Yan

2015-01-01

Full Text Available A predictive model for droplet size and velocity distributions of a pressure swirl atomizer has been proposed based on the maximum entropy formalism (MEF. The constraint conditions of the MEF model include the conservation laws of mass, momentum, and energy. The effects of liquid swirling strength, Weber number, gas-to-liquid axial velocity ratio and gas-to-liquid density ratio on the droplet size and velocity distributions of a pressure swirl atomizer are investigated. Results show that model based on maximum entropy formalism works well to predict droplet size and velocity distributions under different spray conditions. Liquid swirling strength, Weber number, gas-to-liquid axial velocity ratio and gas-to-liquid density ratio have different effects on droplet size and velocity distributions of a pressure swirl atomizer.

Improvement of analysis precision upon the atomic number and electron density measurement by the dual x-ray CT

Science.gov (United States)

Imura, Yukino; Morii, Hisashi; Koike, Akifumi; Okunoyama, Takaharu; Neo, Yoichiro; Mimura, Hidenori; Aoki, Toru

2010-08-01

To identify the factor impairing the material identification parameters, which is provided by the dual-energy X-ray computed tomography method using a conventional X-ray tube and a CdTe detector, linear attenuation coefficient was measured by the radioactivity of radio isotopes and compared with theoretical figure. In our study, the atomic number and the electron density is calculated from the linear attenuation coefficient obtained in CT measurement by 64-channel CdTe line detector. To estimate accuracy of CdTe line sensor, it is needed to obtain the linear attenuation coefficient accurately. Using a single detector, the linear attenuation coefficient is verified for accuracy. The energy resolution of CdTe detectors and the method of reconstruction are discussed.

Bloch oscillations of ultracold atoms and measurement of the fine structure constant; Oscillations de Bloch d'atomes ultrafroids et mesure de la constante de structure fine

Energy Technology Data Exchange (ETDEWEB)

Clade, P

2005-10-15

From a measurement of the recoil velocity of an atom absorbing a photon, it is possible to deduce a determination of the ratio h/m between the Planck constant and the mass of the atoms and then to deduce a value of the fine structure constant alpha. To do this measurement, we use the technique of Bloch oscillations, which allows us to transfer a large number of recoils to atoms. A velocity sensor, based on velocity selective Raman transition, enables us to measure the momentum transferred to the atoms. A measurement with a statistical uncertainty of 4.4 10{sup -9}, in conjunction with a careful study of systematic effects (5 10{sup -9}), has led us to a determination of alpha with an uncertainty of 6.7 10{sup -9}: {alpha}{sup -1}(Rb) = 137.03599878 (91). This uncertainty is similar to the uncertainty of the best determinations of alpha based on atom interferometry. (author)

Antiprotonic-hydrogen atoms

International Nuclear Information System (INIS)

Batty, C.J.

1989-07-01

Experimental studies of antiprotonic-hydrogen atoms have recently made great progress following the commissioning of the low energy antiproton facility (LEAR) at CERN in 1983. At the same time our understanding of the atomic cascade has increased considerably through measurements of the X-ray spectra. The life history of the p-bar-p atom is considered in some detail, from the initial capture of the antiproton when stopping in hydrogen, through the atomic cascade with the emission of X-rays, to the final antiproton annihilation and production of mesons. The experiments carried out at LEAR are described and the results compared with atomic cascade calculations and predictions of strong interaction effects. (author)

Charge exchange effect on laser isotope separation of atomic uranium

International Nuclear Information System (INIS)

Niki, Hideaki; Izawa, Yasukazu; Otani, Hiroyasu; Yamanaka, Chiyoe

1982-01-01

Uranium isotope separating experiment was performed using the two-step photoionization technique with dye laser and nitrogen laser by heating uranium metal with electron beam and producing atomic beam using generated vapour. The experimental results are described after explaining the two-step photoionization by laser, experimental apparatus, the selection of exciting wavelength and others. Enrichment factor depends largely on the spectrum purity of dye laser which is the exciting source. A large enrichment factor of 48.3 times was obtained for spectrum width 0.03A. To put the uranium isotope separation with laser into practice, the increase of uranium atomic density is considered to be necessary for improving the yield. Experimental investigation was first carried out on the charge exchange effect that seems most likely to affect the decrease of enrichment factor, and the charge exchange cross-section was determined. The charge exchange cross-section depends on the relative kinetic energy between ions and atoms. The experimental result showed that the cross-section was about 5 x 10 -13 cm 2 at 1 eV and 10 -13 cm 2 at 90 eV. These values are roughly ten times as great as those calculated in Lawrence Livermore Laboratory, and it is expected that they become the greatest factor for giving the upper limit of uranium atomic density in a process of practical application. (Wakatsuki, Y.)

The effect of the electronic structure, phase transition, and localized dynamics of atoms in the formation of tiny particles of gold

Energy Technology Data Exchange (ETDEWEB)

Ali, Mubarak, E-mail: mubarak74@comsats.edu.pk, E-mail: mubarak74@mail.com [COMSATS Institute of Information Technology, Department of Physics (Pakistan); Lin, I-Nan [Tamkang University, Department of Physics (China)

2017-01-15

In addition to self-governing properties, tiny-sized particles of metallic colloids are the building blocks of large-sized particles; thus, their study has been the subject of a large number of publications. In the present work, it has been discussed that geometry structure of tiny particle made through atom-to-atom amalgamation depends on attained dynamics of gold atoms along with protruded orientations. The localized process conditions direct two-dimensional structure of a tiny particle at atomically flat air-solution interface while heating locally dynamically approached atoms, thus, negate the role of van der Waals interactions. At electronphoton-solution interface, impinging electrons stretch or deform atoms of tiny particles depending on the mechanism of impingement. In addition, to strike regular grid of electrons ejected on split of atoms not executing excitations and de-excitations of their electrons, atoms of tiny particles also deform or stretch while occupying various sites depending on the process of synergy. Under suitable impinging electron streams, those tiny particles in monolayer two-dimensional structure electron states of their atoms are diffused in the direction of transferred energy, thus, coincide to the next adjacent atoms in each one-dimensional array dealing the same sort of behavior. Instantaneously, photons of adequate energy propagate on the surfaces of such electronic structures and modify those into smooth elements, thus, disregard the phenomenon of localized surface plasmons. This study highlights the fundamental process of formation of tiny particles where the role of localized dynamics of atoms and their electronic structure along with interaction to light are discussed. Such a tool of processing materials, in nonequilibrium pulse-based process, opens a number of possibilities to develop engineered materials with specific chemical, optical, and electronic properties.

Powerful effective one-electron Hamiltonian for describing many-atom interacting systems

International Nuclear Information System (INIS)

Lugo, J.O.; Vergara, L.I.; Bolcatto, P.G.; Goldberg, E.C.

2002-01-01

In this paper, we present an alternative way to build the effective one-electron picture of a many-atom interacting system. By simplifying the many-body general problem we present two different options for the bond-pair model Hamiltonian. We have found that the successive approximations in order to achieve the effective description have a dramatic influence on the result. Thus, only the model that introduces the correct renormalization in the diagonal term due to the overlap is able to reproduce, even in a quantitative fashion, the main properties of simple homonuclear diatomic molecules. The success of the model resides in the accurate definitions (free of parametrization) of the Hamiltonian terms, which, therefore, could be used to describe more complex interacting systems such as polyatomic molecules, adsorbed species, or atoms scattered by a surface

Mass defect effects in atomic clocks

Science.gov (United States)

Yudin, Valeriy; Taichenachev, Alexey

2018-03-01

We consider some implications of the mass defect on the frequency of atomic transitions. We have found that some well-known frequency shifts (the gravitational shift and motion-induced shifts such as quadratic Doppler and micromotion shifts) can be interpreted as consequences of the mass defect in quantum atomic physics, i.e. without the need for the concept of time dilation used in special and general relativity theories. Moreover, we show that the inclusion of the mass defect leads to previously unknown shifts for clocks based on trapped ions.

Working group written presentation: Atomic oxygen

International Nuclear Information System (INIS)

Leger, L.J.; Visentine, J.T.

1989-01-01

Earlier Shuttle flight experiments have shown NASA and SDIO spacecraft designed for operation in low-Earth orbit (LEO) must take into consideration the highly oxidative characteristics of the ambient flight environment. Materials most adversely affected by atomic oxygen interactions include organic films, advanced (carbon-based) composites, thermal control coatings, organic-based paints, optical coatings, and thermal control blankets commonly used in spacecraft applications. Earlier results of NASA flight experiments have shown prolonged exposure of sensitive spacecraft materials to the LEO environment will result in degraded systems performance or, more importantly, lead to requirements for excessive on-orbit maintenance, with both conditions contributing significantly to increased mission costs and reduced mission objectives. Flight data obtained from previous Space Shuttle missions and results of the Solar Max recovery mission are limited in terms of atomic oxygen exposure and accuracy of fluence estimates. The results of laboratory studies to investigate the long-term (15 to 30 yrs) effects of AO exposure on spacecraft surfaces are only recently available, and qualitative correlations of laboratory results with flight results have been obtained for only a limited number of materials. The working group recommended the most promising ground-based laboratories now under development be made operational as soon as possible to study the full-life effects of atomic oxygen exposure on spacecraft systems

STIR-Physics: Cold Atoms and Nanocrystals in Tapered Nanofiber and High-Q Resonator Potentials

Science.gov (United States)

2016-11-02

STIR- Physics : Cold Atoms and Nanocrystals in Tapered Nanofiber and High-Q Resonator Potentials We worked on a tapered fiber in cold atomic cloud...reviewed journals: Number of Papers published in non peer-reviewed journals: Final Report: STIR- Physics : Cold Atoms and Nanocrystals in Tapered Nanofiber...other than abstracts): Number of Peer-Reviewed Conference Proceeding publications (other than abstracts): Books Number of Manuscripts: 0.00Number of

Josephson current at atomic scale: Tunneling and nanocontacts using a STM

International Nuclear Information System (INIS)

Rodrigo, J.G.; Crespo, V.; Vieira, S.

2006-01-01

Using a scanning tunneling microscope, STM, with a superconducting tip, we have measured the Josephson current in atomic size tunnel junctions and contacts with a small number of quantum channels of conduction. We analyze our results in terms of the Ivanchenko and Zil'berman model for phase diffusion. The effect of the thermal energy and the electromagnetic environment on the Josephson current is discussed in terms of the transmissions of the individual quantum channels. These results suppose an initial step to the control of Scanning Josephson Spectroscopy at atomic level

The effect of substrate temperature on atomic layer deposited zinc tin oxide

Energy Technology Data Exchange (ETDEWEB)

Lindahl, Johan, E-mail: johan.lindahl@angstrom.uu.se; Hägglund, Carl, E-mail: carl.hagglund@angstrom.uu.se; Wätjen, J. Timo, E-mail: timo.watjen@angstrom.uu.se; Edoff, Marika, E-mail: marika.edoff@angstrom.uu.se; Törndahl, Tobias, E-mail: tobias.torndahl@angstrom.uu.se

2015-07-01

Zinc tin oxide (ZTO) thin films were deposited on glass substrates by atomic layer deposition (ALD), and the film properties were investigated for varying deposition temperatures in the range of 90 to 180 °C. It was found that the [Sn]/([Sn] + [Zn]) composition is only slightly temperature dependent, while properties such as growth rate, film density, material structure and band gap are more strongly affected. The growth rate dependence on deposition temperature varies with the relative number of zinc or tin containing precursor pulses and it correlates with the growth rate behavior of pure ZnO and SnO{sub x} ALD. In contrast to the pure ZnO phase, the density of the mixed ZTO films is found to depend on the deposition temperature and it increases linearly with about 1 g/cm{sup 3} in total over the investigated range. Characterization by transmission electron microscopy suggests that zinc rich ZTO films contain small (~ 10 nm) ZnO or ZnO(Sn) crystallites embedded in an amorphous matrix, and that these crystallites increase in size with increasing zinc content and deposition temperature. These crystallites are small enough for quantum confinement effects to reduce the optical band gap of the ZTO films as they grow in size with increasing deposition temperature. - Highlights: • Zinc tin oxide thin films were deposited by atomic layer deposition. • The structure and optical properties were studied at different growth temperatures. • The growth temperature had only a small effect on the composition of the films. • Small ZnO or ZnO(Sn) crystallites were observed by TEM in zinc rich ZTO films. • The growth temperature affects the crystallite size, which influences the band gap.