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Sample records for atom probe field

  1. Atom probe field ion microscopy of high resistivity materials

    Energy Technology Data Exchange (ETDEWEB)

    Sibrandij, S.J.; Larson, D.J.; Miller, M.K.

    1998-02-01

    Over the last 30 years the atom probe has proved to be a powerful tool for studying nanometer-sized compositional fluctuations in a wide range of metallic alloys but has had only limited applications to semiconductors and ceramics. One of the primary reasons for this difference is the higher resistivity of semiconducting and ceramic specimens. Because of this high resistivity, the high voltage field evaporation pulse is attenuated before it reaches the apex of the specimen thereby making the pulse ineffective for field evaporation. Experiments have demonstrated that both variants of the voltage-pulsed atom probe (i.e., those instruments in which the field evaporation pulse is applied directly to the specimen and those in which the negative pulse is applied to a counter electrode in front of the specimen) are equally affected. In this overview, the limits of applicability of the voltage-pulsed atom probe to high resistivity materials are examined. In this study, a wide range of materials have been examined to determine whether field ion microscopy and voltage-pulsed field evaporation can be achieved and the results are summarized in the report. Field ion microscopy including dc field evaporation was possible for all materials except bulk ceramic insulators and glasses. Field ion microscopy requires some conductivity both to achieve a high electric field at the apex of the specimen, and also to support the field ion current. In contrast, voltage-pulsed field evaporation requires transmission of the pulse to the apex of the specimen. All metallic alloys including high resistance alloys and metallic glasses were successfully field evaporated with a voltage pulse. Specimens that were produced from bulk material of several conducting ceramics including MoSi, TiB and TiC were also successfully field evaporated with a voltage pulse.

  2. Clustered field evaporation of metallic glasses in atom probe tomography.

    Science.gov (United States)

    Zemp, J; Gerstl, S S A; Löffler, J F; Schönfeld, B

    2016-03-01

    Field evaporation of metallic glasses is a stochastic process combined with spatially and temporally correlated events, which are referred to as clustered evaporation (CE). This phenomenon is investigated by studying the distance between consecutive detector hits. CE is found to be a strongly localized phenomenon (up to 3nm in range) which also depends on the type of evaporating ions. While a similar effect in crystals is attributed to the evaporation of crystalline layers, CE of metallic glasses presumably has a different - as yet unknown - physical origin. The present work provides new perspectives on quantification methods for atom probe tomography of metallic glasses.

  3. Atom probe field ion microscopy and related topics: A bibliography 1992

    Energy Technology Data Exchange (ETDEWEB)

    Russell, K.F.; Godfrey, R.D.; Miller, M.K.

    1993-12-01

    This bibliography contains citations of books, conference proceedings, journals, and patents published in 1992 on the following types of microscopy: atom probe field ion microscopy (108 items); field emission microscopy (101 items); and field ion microscopy (48 items). An addendum of 34 items missed in previous bibliographies is included.

  4. Atom probe field ion microscopy and related topics: A bibliography 1989

    Energy Technology Data Exchange (ETDEWEB)

    Miller, M.K.; Hawkins, A.R.; Russell, K.F.

    1990-12-01

    This bibliography includes references related to the following topics: atom probe field ion microscopy (APFIM), field ion spectroscopy (FIM), field emission microscopy (FEM), liquid metal ion sources (LMIS), scanning tunneling microscopy (STM), and theory. Technique-orientated studies and applications are included. This bibliography covers the period 1989. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications.

  5. Atom probe field ion microscopy and related topics: A bibliography 1990

    Energy Technology Data Exchange (ETDEWEB)

    Russell, K.F.; Miller, M.K.

    1991-12-01

    This bibliography includes references related to the following topics: atom probe field ion microscopy (APFIM), field ion microscopy (FIM), field emission (FE), ion sources, and field desorption mass microscopy (FDMM). Technique-orientated studies and applications are included. The bibliography covers the period 1990. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications. To reduce the length of this document, the references have been reduced to the minimum necessary to locate the articles. The references, listed alphabetically by authors, are subdivided into the categories listed in paragraph one above. An Addendum of references missed in previous bibliographies is included.

  6. Atom probe field ion microscopy and related topics: A bibliography 1993

    Energy Technology Data Exchange (ETDEWEB)

    Godfrey, R.D.; Miller, M.K.; Russell, K.F.

    1994-10-01

    This bibliography, covering the period 1993, includes references related to the following topics: atom probe field ion microscopy (APFIM), field emission (FE), and field ion microscopy (FIM). Technique-oriented studies and applications are included. The references contained in this document were compiled from a variety of sources including computer searches and personal lists of publications. To reduce the length of this document, the references have been reduced to the minimum necessary to locate the articles. The references are listed alphabetically by authors, an Addendum of references missed in previous bibliographies is included.

  7. Atom Probe Tomography 2012

    Science.gov (United States)

    Kelly, Thomas F.; Larson, David J.

    2012-08-01

    In the world of tomographic imaging, atom probe tomography (APT) occupies the high-spatial-resolution end of the spectrum. It is highly complementary to electron tomography and is applicable to a wide range of materials. The current state of APT is reviewed. Emphasis is placed on applications and data analysis as they apply to many fields of research and development including metals, semiconductors, ceramics, and organic materials. We also provide a brief review of the history and the instrumentation associated with APT and an assessment of the existing challenges in the field.

  8. Probing three-dimensional surface force fields with atomic resolution: Measurement strategies, limitations, and artifact reduction

    Directory of Open Access Journals (Sweden)

    Mehmet Z. Baykara

    2012-09-01

    Full Text Available Noncontact atomic force microscopy (NC-AFM is being increasingly used to measure the interaction force between an atomically sharp probe tip and surfaces of interest, as a function of the three spatial dimensions, with picometer and piconewton accuracy. Since the results of such measurements may be affected by piezo nonlinearities, thermal and electronic drift, tip asymmetries, and elastic deformation of the tip apex, these effects need to be considered during image interpretation.In this paper, we analyze their impact on the acquired data, compare different methods to record atomic-resolution surface force fields, and determine the approaches that suffer the least from the associated artifacts. The related discussion underscores the idea that since force fields recorded by using NC-AFM always reflect the properties of both the sample and the probe tip, efforts to reduce unwanted effects of the tip on recorded data are indispensable for the extraction of detailed information about the atomic-scale properties of the surface.

  9. Atom probe field ion microscope study of the range and diffusivity of helium in tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, A.

    1978-08-01

    A time-of-flight (TOF) atom-probe field-ion microscope (FIM) specifically designed for the study of defects in metals is described. With this automated system 600 TOF min/sup -1/ can be recorded and analyzed. Performance tests of the instrument demonstrated that (1) the seven isotopes of molybdenum and the five isotopes of tungsten can be clearly resolved; and (2) the concentration and spatial distribution of all constitutents present at levels greater than 0.05 at. % in a W--25 at. % Re, Mo--1.0 at. % Ti, Mo--1.0 at. % Ti--0.08 at. % Zr (TZM), a low swelling stainless steel (LS1A) and a metallic glass (Metglas 2826) can be measured. The effect of the rate of field evaporation on the quantitative atom probe analysis of a Mo--1.0 at. % Ti alloy and a Mo--1.0 at. % Ti--0.08 at. % Zr alloy was investigated. As the field evaporation rate increased the measured Ti concentration was found to also increase. A simple qualitative model was proposed to explain the observation. The spatial distribution of titanium in a fast neutron irradiated Mo--1.0 at. % Ti alloy has been investigated. No evidence of Ti segregation to the voids was detected nor has any evidence of significant resolution of Ti from the TiC precipitates been detected. A small amount of segregation of carbon to a void was detected.

  10. Specimen preparation and atom probe field ion microscopy of BSCCO-2212 superconductors

    Energy Technology Data Exchange (ETDEWEB)

    Larson, D.J. [Wisconsin Univ., Madison, WI (United States). Mater. Sci. Program]|[Applied Superconductivity Center, Univ. of Wisconsin, Madison, WI (United States); Camus, P.P. [Applied Superconductivity Center, Univ. of Wisconsin, Madison, WI (United States)]|[Wisconsin Univ., Madison, WI (United States). Dept. of Materials Sciences and Engineering; Vargas, J.L. [Applied Superconductivity Center, Univ. of Wisconsin, Madison, WI (United States); Kelly, T.F. [Wisconsin Univ., Madison, WI (United States). Mater. Sci. Program]|[Applied Superconductivity Center, Univ. of Wisconsin, Madison, WI (United States)]|[Wisconsin Univ., Madison, WI (United States). Dept. of Materials Sciences and Engineering; Miller, M.K. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

    1996-09-01

    Field ion specimens of Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub x} (BSCCO) high temperature superconductor (HTS) materials have been prepared using a combination of three different preparation techniques: the method of sharp shards, electropolishing and ion milling. Field ion microscopy (FIM) has demonstrated that samples which exhibit the ``striped``-image contrast characteristic of HTS materials can be successfully fabricated using this combination. FIM images have been obtained which show the striped-image contrast much clearer than any previously published images of Pb-free BSCCO. Preliminary atom probe (AP) chemical analysis of the material was also performed. Analytical electron microscopy was used to confirm the existence of both the correct crystallographic structure and nominal composition in the near-apex region of the specimen after preparation and FIM. (orig.).

  11. Atom probe tomography today

    Directory of Open Access Journals (Sweden)

    Alfred Cerezo

    2007-12-01

    Full Text Available This review aims to describe and illustrate the advances in the application of atom probe tomography that have been made possible by recent developments, particularly in specimen preparation techniques (using dual-beam focused-ion beam instruments but also of the more routine use of laser pulsing. The combination of these two developments now permits atomic-scale investigation of site-specific regions within engineering alloys (e.g. at grain boundaries and in the vicinity of cracks and also the atomic-level characterization of interfaces in multilayers, oxide films, and semiconductor materials and devices.

  12. Interpretation of atom probe tomography data for the intermetallic TiAl+Nb by means of field evaporation simulation

    KAUST Repository

    Boll, Torben

    2013-01-01

    In this paper simulations of the field evaporation process during field ion microscopy (FIM) and atom probe tomography (APT) are presented and compared with experimental data. The Müller-Schottky-model [1] was extended to include the local atomic arrangement on the evaporation process of atoms. This arrangement was described by the sum of the next-neighbor-binding-energies, which differ for an atom of type A, depending on how many A-A, B-B or A-B bonds are present. Thus simulations of APT-data of intermetallic phases become feasible. In this study simulations of L10-TiAl with additions of Nb are compared with experimental data. Certain artifacts, which appear for experimental data are treated as well. © 2012 Elsevier B.V.

  13. Probing Matter-Field and Atom-Number Correlations in Optical Lattices by Global Nondestructive Addressing

    CERN Document Server

    Kozlowski, Wojciech; Mekhov, Igor B

    2014-01-01

    We show that light scattering from an ultracold gas reveals not only density correlations, but also matter-field interference at its shortest possible distance in an optical lattice, which defines key properties such as tunneling and matter-field phase gradients. This signal can be enhanced by concentrating probe light between lattice sites rather than at density maxima. As addressing between two single sites is challenging, we focus on global nondestructive scattering, allowing probing order parameters, matter-field quadratures and their squeezing. The scattering angular distribution displays peaks even if classical diffraction is forbidden and we derive generalized Bragg conditions. Light scattering distinguishes all phases in the Mott insulator - superfluid - Bose glass phase transition.

  14. The response of a neutral atom to a strong laser field probed by transient absorption near the ionisation threshold

    CERN Document Server

    Simpson, E R; Austin, D R; Diveki, Z; Hutchinson, S E E; Siegel, T; Ruberti, M; Averbukh, V; Miseikis, L; Strüber, C; Chipperfield, L; Marangos, J P

    2015-01-01

    We present transient absorption spectra of an extreme ultraviolet attosecond pulse train in helium dressed by an 800 nm laser field with intensity ranging from $2\\times10^{12}$ W/cm$^2$ to $2\\times10^{14}$ W/cm$^2$. The energy range probed spans 16-42 eV, straddling the first ionisation energy of helium (24.59 eV). By changing the relative polarisation of the dressing field with respect to the attosecond pulse train polarisation we observe a large change in the modulation of the absorption reflecting the vectorial response to the dressing field. With parallel polarized dressing and probing fields, we observe significant modulations with periods of one half and one quarter of the dressing field period. With perpendicularly polarized dressing and probing fields, the modulations of the harmonics above the ionisation threshold are significantly suppressed. A full-dimensionality solution of the single-atom time-dependent Schr\\"odinger equation obtained using the recently developed ab-initio time-dependent B-spline...

  15. Understanding Atom Probe Tomography of Oxide-Supported Metal Nanoparticles by Correlation with Atomic-Resolution Electron Microscopy and Field Evaporation Simulation.

    Science.gov (United States)

    Devaraj, Arun; Colby, Robert; Vurpillot, François; Thevuthasan, Suntharampillai

    2014-04-17

    Oxide-supported metal nanoparticles are widely used in heterogeneous catalysis. The increasingly detailed design of such catalysts necessitates three-dimensional characterization with high spatial resolution and elemental selectivity. Laser-assisted atom probe tomography (APT) is uniquely suited to the task but faces challenges with the evaporation of metal/insulator systems. Correlation of APT with aberration-corrected scanning transmission electron microscopy (STEM), for Au nanoparticles embedded in MgO, reveals preferential evaporation of the MgO and an inaccurate assessment of nanoparticle composition. Finite element field evaporation modeling is used to illustrate the evolution of the evaporation front. Nanoparticle composition is most accurately predicted when the MgO is treated as having a locally variable evaporation field, indicating the importance of considering laser-oxide interactions and the evaporation of various molecular oxide ions. These results demonstrate the viability of APT for analysis of oxide-supported metal nanoparticles, highlighting the need for developing a theoretical framework for the evaporation of heterogeneous materials.

  16. HAADF-STEM atom counting in atom probe tomography specimens: Towards quantitative correlative microscopy.

    Science.gov (United States)

    Lefebvre, W; Hernandez-Maldonado, D; Moyon, F; Cuvilly, F; Vaudolon, C; Shinde, D; Vurpillot, F

    2015-12-01

    The geometry of atom probe tomography tips strongly differs from standard scanning transmission electron microscopy foils. Whereas the later are rather flat and thin (atom probe tomography specimens. Based on simulations (electron probe propagation and image simulations), the possibility to apply quantitative high angle annular dark field scanning transmission electron microscopy to of atom probe tomography specimens has been tested. The influence of electron probe convergence and the benefice of deconvolution of electron probe point spread function electron have been established. Atom counting in atom probe tomography specimens is for the first time reported in this present work. It is demonstrated that, based on single projections of high angle annular dark field imaging, significant quantitative information can be used as additional input for refining the data obtained by correlative analysis of the specimen in APT, therefore opening new perspectives in the field of atomic scale tomography.

  17. In Situ Atom Probe Deintercalation of Lithium-Manganese-Oxide.

    Science.gov (United States)

    Pfeiffer, Björn; Maier, Johannes; Arlt, Jonas; Nowak, Carsten

    2017-01-30

    Atom probe tomography is routinely used for the characterization of materials microstructures, usually assuming that the microstructure is unaltered by the analysis. When analyzing ionic conductors, however, gradients in the chemical potential and the electric field penetrating dielectric atom probe specimens can cause significant ionic mobility. Although ionic mobility is undesirable when aiming for materials characterization, it offers a strategy to manipulate materials directly in situ in the atom probe. Here, we present experimental results on the analysis of the ionic conductor lithium-manganese-oxide with different atom probe techniques. We demonstrate that, at a temperature of 30 K, characterization of the materials microstructure is possible without measurable Li mobility. Also, we show that at 298 K the material can be deintercalated, in situ in the atom probe, without changing the manganese-oxide host structure. Combining in situ atom probe deintercalation and subsequent conventional characterization, we demonstrate a new methodological approach to study ionic conductors even in early stages of deintercalation.

  18. Two-dimensional atom localization via probe absorption in a four-level atomic system

    Institute of Scientific and Technical Information of China (English)

    Wang Zhi-Ping; Ge Qiang; Ruan Yu-Hua; Yu Ben-Li

    2013-01-01

    We have investigated the two-dimensional (2D) atom localization via probe absorption in a coherently driven fourlevel atomic system by means of a radio-frequency field driving a hyperfine transition.It is found that the detecting probability and precision of 2D atom localization can be significantly improved via adjusting the system parameters.As a result,our scheme may be helpful in laser cooling or the atom nano-lithography via atom localization.

  19. Characterization of Akiyama probe applied to dual-probes atomic force microscope

    Science.gov (United States)

    Wang, Hequn; Gao, Sitian; Li, Wei; Shi, Yushu; Li, Qi; Li, Shi; Zhu, Zhendong

    2016-10-01

    The measurement of nano-scale line-width has always been important and difficult in the field of nanometer measurements, while the rapid development of integrated circuit greatly raises the demand again. As one kind of scanning probe microscope (SPM), atomic force microscope (AFM) can realize quasi three-dimensional measurement, which is widely used in nanometer scale line-width measurement. Our team researched a dual-probes atomic force microscope, which can eliminate the prevalent effect of probe width on measurement results. In dual-probes AFM system, a novel head are newly designed. A kind of self-sensing and self-exciting probes which is Nanosensors cooperation's patented probe—Akiyama probe, is used in this novel head. The Akiyama probe applied to dual-probe atomic force microscope is one of the most important issues. The characterization of Akiyama probe would affect performance and accuracy of the whole system. The fundamental features of the Akiyama probe are electrically and optically characterized in "approach-withdraw" experiments. Further investigations include the frequency response of an Akiyama probe to small mechanical vibrations externally applied to the tip and the effective loading force yielding between the tip and the sample during the periodic contact. We hope that the characterization of the Akiyama probe described in this paper will guide application for dual-probe atomic force microscope.

  20. Atom probe tomography of lithium-doped network glasses

    Energy Technology Data Exchange (ETDEWEB)

    Greiwe, Gerd-Hendrik, E-mail: g_grei01@uni-muenster.de [Institute of Materials Physics, University of Münster, Wilhelm-Klemm-Str. 10, D-48149 Münster (Germany); Balogh, Zoltan; Schmitz, Guido [Institute of Material Science, University of Stuttgart, Heisenberg Straße 3, D-70569 Stuttgart (Germany)

    2014-06-01

    Li-doped silicate and borate glasses are electronically insulating, but provide considerable ionic conductivity. Under measurement conditions of laser-assisted atom probe tomography, mobile Li ions are redistributed in response to high electric fields. In consequence, the direct interpretation of measured composition profiles is prevented. It is demonstrated that composition profiles are nevertheless well understood by a complex model taking into account the electronic structure of dielectric materials, ionic mobility and field screening. Quantitative data on band bending and field penetration during measurement are derived which are important in understanding laser-assisted atom probe tomography of dielectric materials. - Highlights: • Atom probe tomography is performed on ion conducting glasses. • Redistribution of ions during the measurement is observed. • An electrostatic model is applied to describe the electric field and ion diffusion. • Measurement is conducted of the absolute temperature during laser pulses.

  1. The future of atom probe tomography

    Directory of Open Access Journals (Sweden)

    Michael K. Miller

    2012-04-01

    Full Text Available The dream of the microscopy and materials science communities is to see, identify, accurately locate, and determine the fundamental physical properties of every atom in a specimen. With this knowledge together with modern computer models and simulations, a full understanding of the properties of a material can be determined. This fundamental knowledge leads to the design and development of more advanced materials for solving the needs of society. The technique of atom probe tomography is the closest to fulfilling this dream but is still significantly short of the goal. The future of atom probe tomography, and the prospects for achieving this ultimate goal are outlined.

  2. Comparison of the quantitative analysis performance between pulsed voltage atom probe and pulsed laser atom probe.

    Science.gov (United States)

    Takahashi, J; Kawakami, K; Raabe, D

    2017-01-31

    The difference in quantitative analysis performance between the voltage-mode and laser-mode of a local electrode atom probe (LEAP3000X HR) was investigated using a Fe-Cu binary model alloy. Solute copper atoms in ferritic iron preferentially field evaporate because of their significantly lower evaporation field than the matrix iron, and thus, the apparent concentration of solute copper tends to be lower than the actual concentration. However, in voltage-mode, the apparent concentration was higher than the actual concentration at 40K or less due to a detection loss of matrix iron, and the concentration decreased with increasing specimen temperature due to the preferential evaporation of solute copper. On the other hand, in laser-mode, the apparent concentration never exceeded the actual concentration, even at lower temperatures (20K), and this mode showed better quantitative performance over a wide range of specimen temperatures. These results indicate that the pulsed laser atom probe prevents both detection loss and preferential evaporation under a wide range of measurement conditions.

  3. Imaging of microwave fields using ultracold atoms

    CERN Document Server

    Boehi, Pascal; Haensch, Theodor W; Treutlein, Philipp; 10.1063/1.3470591

    2010-01-01

    We report a technique that uses clouds of ultracold atoms as sensitive, tunable, and non-invasive probes for microwave field imaging with micrometer spatial resolution. The microwave magnetic field components drive Rabi oscillations on atomic hyperfine transitions whose frequency can be tuned with a static magnetic field. Readout is accomplished using state-selective absorption imaging. Quantitative data extraction is simple and it is possible to reconstruct the distribution of microwave magnetic field amplitudes and phases. While we demonstrate 2d imaging, an extension to 3d imaging is straightforward. We use the method to determine the microwave near-field distribution around a coplanar waveguide integrated on an atom chip.

  4. Reflections on the projection of ions in atom probe tomography

    OpenAIRE

    De Geuser, Frédéric; Gault, Baptiste

    2016-01-01

    There are two main projections used to transform, and reconstruct, field ion micrographs or atom probe tomography data into atomic coordinates at the specimen surface and, subsequently, in three-dimensions. In this article, we present a perspective on the strength of the azimuthal equidistant projection in comparison to the more widely used and well-established point-projection(or pseudo-stereographic projection), which underpins data reconstruction in most software packages currently in use ...

  5. Encapsulation method for atom probe tomography analysis of nanoparticles

    NARCIS (Netherlands)

    Larson, D.J.; Giddings, A.D.; Wub, Y.; Verheijen, M.A.; Prosa, T.J.; Roozeboom, F.; Rice, K.P.; Kessels, W.M.M.; Geiser, B.P.; Kelly, T.F.

    2015-01-01

    Open-space nanomaterials are a widespread class of technologically important materials that are generally incompatible with analysis by atom probe tomography (APT) due to issues with specimen preparation, field evaporation and data reconstruction. The feasibility of encapsulating such non-compact ma

  6. Atom Probe Tomography of Nanoscale Electronic Materials

    Energy Technology Data Exchange (ETDEWEB)

    Larson, David J.; Prosa, Ty J.; Perea, Daniel E.; Inoue, Hidekazu; Mangelinck, D.

    2016-01-01

    Atom probe tomography (APT) is a mass spectrometry based on time-of-flight measurements which also concurrently produces 3D spatial information. The reader is referred to any of the other papers in this volume or to the following references for further information 4–8. The current capabilities of APT, such as detecting a low number of dopant atoms in nanoscale devices or segregation at a nanoparticle interface, make this technique an important component in the nanoscale metrology toolbox. In this manuscript, we review some of the applications of APT to nanoscale electronic materials, including transistors and finFETs, silicide contact microstructures, nanowires, and nanoparticles.

  7. Toward atom probe tomography of microelectronic devices

    Science.gov (United States)

    Larson, D. J.; Lawrence, D.; Lefebvre, W.; Olson, D.; Prosa, T. J.; Reinhard, D. A.; Ulfig, R. M.; Clifton, P. H.; Bunton, J. H.; Lenz, D.; Olson, J. D.; Renaud, L.; Martin, I.; Kelly, T. F.

    2011-11-01

    Atom probe tomography and scanning transmission electron microscopy has been used to analyze a commercial microelectronics device prepared by depackaging and focused ion beam milling. Chemical and morphological data are presented from the source, drain and channel regions, and part of the gate oxide region of an Intel® i5-650 p-FET device demonstrating feasibility in using these techniques to investigate commercial chips.

  8. Probing Dark Energy with Atom Interferometry

    CERN Document Server

    Burrage, Clare; Hinds, E A

    2015-01-01

    Theories of dark energy require a screening mechanism to explain why the associated scalar fields do not mediate observable long range fifth forces. The archetype of this is the chameleon field. Here we show that individual atoms are too small to screen the chameleon field inside a large high-vacuum chamber, and therefore can detect the field with high sensitivity. We derive new limits on the chameleon parameters from existing experiments, and show that most of the remaining chameleon parameter space is readily accessible using atom interferometry.

  9. Toward the Atomic-Level Mass Analysis of Biomolecules by the Scanning Atom Probe.

    Science.gov (United States)

    Nishikawa, Osamu; Taniguchi, Masahiro

    2016-12-22

    In 1994, a new type of atom probe instrument, named the scanning atom probe (SAP), was proposed. The unique feature of the SAP is the introduction of a small extraction electrode, which scans over a specimen surface and confines the high field, required for field evaporation of surface atoms in a small space, between the specimen and the electrode. Thus, the SAP does not require a sharp specimen tip. This indicates that the SAP can mass analyze the specimens which are difficult to form in a sharp tip, such as organic materials and biomolecules. Clean single wall carbon nanotubes (CNT), made by high-pressure carbon monoxide process are found to be the best substrates for biomolecules. Various amino acids and dipeptide biomolecules were successfully mass analyzed, revealing characteristic clusters formed by strongly bound atoms in the specimens. The mass analysis indicates that SAP analysis of biomolecules is not only qualitative, but also quantitative.

  10. Mining information from atom probe data.

    Science.gov (United States)

    Cairney, Julie M; Rajan, Krishna; Haley, Daniel; Gault, Baptiste; Bagot, Paul A J; Choi, Pyuck-Pa; Felfer, Peter J; Ringer, Simon P; Marceau, Ross K W; Moody, Michael P

    2015-12-01

    Whilst atom probe tomography (APT) is a powerful technique with the capacity to gather information containing hundreds of millions of atoms from a single specimen, the ability to effectively use this information creates significant challenges. The main technological bottleneck lies in handling the extremely large amounts of data on spatial-chemical correlations, as well as developing new quantitative computational foundations for image reconstruction that target critical and transformative problems in materials science. The power to explore materials at the atomic scale with the extraordinary level of sensitivity of detection offered by atom probe tomography has not been not fully harnessed due to the challenges of dealing with missing, sparse and often noisy data. Hence there is a profound need to couple the analytical tools to deal with the data challenges with the experimental issues associated with this instrument. In this paper we provide a summary of some key issues associated with the challenges, and solutions to extract or "mine" fundamental materials science information from that data.

  11. Spatial resolution in atom probe tomography

    CERN Document Server

    Gault, Baptiste; de Geuser, Frederic; La Fontaine, Alex; Stephenson, Leigh T; Haley, Daniel; Ringer, Simon P

    2015-01-01

    This article addresses gaps in definitions and a lack of standard measurement techniques to assess the spatial resolution in atom probe tomography. This resolution is known to be anisotropic, being better in the depth than laterally. Generally the presence of atomic planes in the tomographic reconstruction is considered as being a sufficient proof of the quality of the spatial resolution of the instrument. Based on advanced spatial distribution maps, an analysis methodology that interrogates the local neighborhood of the atoms within the tomographic reconstruction, it is shown how both the in-depth and the lateral resolution can be quantified. The influences of the crystallography and the temperature are investigated, and models are proposed to explain the observed results. We demonstrate that the absolute value of resolution is specimenspecific.

  12. Atom probe analysis of titanium hydride precipitates.

    Science.gov (United States)

    Takahashi, J; Kawakami, K; Otsuka, H; Fujii, H

    2009-04-01

    It is expected that the three-dimensional atom probe (3DAP) will be used as a tool to visualize the atomic scale of hydrogen atoms in steel is expected, due to its high spatial resolution and very low detection limit. In this paper, the first 3DAP analysis of titanium hydride precipitates in metal titanium is reported in terms of the quantitative detection of hydrogen. FIB fabrication techniques using the lift-out method have enabled the production of needle tips of hydride precipitates, of several tens of microns in size, within a titanium matrix. The hydrogen concentration estimated from 3DAP analysis was slightly smaller than that of the hydride phase predicted from the phase diagram. We discuss the origin of the difference between the experimental and predicted values and the performance of 3DAP for the quantitative detection of hydrogen.

  13. Formation of field induced absorption in the probe response signal of a four-level V type atomic system a theoretical study

    CERN Document Server

    Islam, Khairul; Bhattacharyya, Dipankar; Bandyopadhyay, Amitava

    2016-01-01

    A density matrix based analytical model is developed to study the coherent probe field propagation through a four-level V type system in presence of a coherent control field. The model allows coupling of the probe field from the upper ground level to both of the excited levels keeping the control field locked to a particular transition. The addition of an extra ground level to a conventional three-level V type system creates extra decay paths to the ground levels for the upper level population. A set of sixteen density matrix based equations are formed and then solved analytically under rotating wave approximation to study the probe response under steady state condition. The simulated probe absorption spectra shows absorption dip at the centre of a transparency window only under Doppler broadened condition although the conventional EIT window appears under Doppler free condition. The dependence of the field induced absorption signal on the Rabi frequency of the control field, population transfer rate among th...

  14. Mapping interfacial excess in atom probe data

    Energy Technology Data Exchange (ETDEWEB)

    Felfer, Peter, E-mail: peter.felfer@sydney.edu.au [School of Aerospace Mechanical and Mechatronic Engineering, The University of Sydney (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney (Australia); Scherrer, Barbara [Australian Centre for Microscopy and Microanalysis, The University of Sydney (Australia); Eidgenossische Technische Hochschule Zürich (Switzerland); Demeulemeester, Jelle [Imec vzw, Kapeldreef 75, Heverlee 3001 (Belgium); Vandervorst, Wilfried [Imec vzw, Kapeldreef 75, Heverlee 3001 (Belgium); Instituut voor Kern- en Stralingsfysica, KU Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium); Cairney, Julie M. [School of Aerospace Mechanical and Mechatronic Engineering, The University of Sydney (Australia); Australian Centre for Microscopy and Microanalysis, The University of Sydney (Australia)

    2015-12-15

    Using modern wide-angle atom probes, it is possible to acquire atomic scale 3D data containing 1000 s of nm{sup 2} of interfaces. It is therefore possible to probe the distribution of segregated species across these interfaces. Here, we present techniques that allow the production of models for interfacial excess (IE) mapping and discuss the underlying considerations and sampling statistics. We also show, how the same principles can be used to achieve thickness mapping of thin films. We demonstrate the effectiveness on example applications, including the analysis of segregation to a phase boundary in stainless steel, segregation to a metal–ceramic interface and the assessment of thickness variations of the gate oxide in a fin-FET. - Highlights: • Using computational geometry, interfacial excess can be mapped for various features in APT. • Suitable analysis models can be created by combining manual modelling and mesh generation algorithms. • Thin film thickness can be mapped with high accuracy using this technique.

  15. Atom-probe investigations of TiAl alloys

    Energy Technology Data Exchange (ETDEWEB)

    Menand, A.; Zapolsky-Tatarenko, H.; Nerac-Partaix, A. [Rouen Univ., Mont-Saint-Aignan (France). Fac. des Sci.

    1998-07-15

    Atom probe field ion microscopy (APFIM) and tomographic atom probe (TAP) have been used to study TiAl-based alloys. The element concentrations, the influence of additional elements such as Cr or Nb as well as the solubility of oxygen in {alpha}{sub 2} (Ti{sub 3}Al) and {gamma} (TiAl) phases in compounds with nominal concentration Ti{sub 54}Al{sub 46} and Ti{sub 58}Al{sub 42} have been determined. By using the detection of oxygen atoms as a very local probe, the present investigation revealed the existence of some intermediate phases during the phase transformation {alpha}{yields}{gamma}. The presence of the oxygen atoms during this transformation gives some peculiarities on the transformation path. The appearance of some metastable phases may be explained by the existence of the homologous series Ti{sub 2n-1}Al{sub n} where n is an integer varying from 1 (stoichiometry TiAl) to {infinity} (phase {alpha}{sub 3} Ti{sub 2}Al). (orig.) 35 refs.

  16. Nanometer-scale isotope analysis of bulk diamond by atom probe tomography

    NARCIS (Netherlands)

    Schirhagl, R.; Raatz, N.; Meijer, J.; Markham, M.; Gerstl, S. S. A.; Degen, C. L.

    2015-01-01

    Atom-probe tomography (APT) combines field emission of atoms with mass spectrometry to reconstruct three-dimensional tomograms of materials with atomic resolution and isotope specificity. Despite significant recent progress in APT technology, application to wide-bandgap materials with strong covalen

  17. Microwave electric field sensing with Rydberg atoms

    Science.gov (United States)

    Stack, Daniel T.; Kunz, Paul D.; Meyer, David H.; Solmeyer, Neal

    2016-05-01

    Atoms form the basis of precise measurement for many quantities (time, acceleration, rotation, magnetic field, etc.). Measurements of microwave frequency electric fields by traditional methods (i.e. engineered antennas) have limited sensitivity and can be difficult to calibrate properly. Highly-excited (Rydberg) neutral atoms have very large electric-dipole moments and many dipole allowed transitions in the range of 1 - 500 GHz. It is possible to sensitively probe the electric field in this range using the combination of two quantum interference phenomena: electromagnetically induced transparency and the Autler-Townes effect. This technique allows for very sensitive field amplitude, polarization, and sub-wavelength imaging measurements. These quantities can be extracted by measuring properties of a probe laser beam as it passes through a warm rubidium vapor cell. Thus far, Rydberg microwave electrometry has relied upon the absorption of the probe laser. We report on our use of polarization rotation, which corresponds to the real part of the susceptibility, for measuring the properties of microwave frequency electric fields. Our simulations show that when a magnetic field is present and directed along the optical propagation direction a polarization rotation signal exists and can be used for microwave electrometry. One central advantage in using the polarization rotation signal rather than the absorption signal is that common mode laser noise is naturally eliminated leading to a potentially dramatic increase in signal-to-noise ratio.

  18. Encapsulation method for atom probe tomography analysis of nanoparticles.

    Science.gov (United States)

    Larson, D J; Giddings, A D; Wu, Y; Verheijen, M A; Prosa, T J; Roozeboom, F; Rice, K P; Kessels, W M M; Geiser, B P; Kelly, T F

    2015-12-01

    Open-space nanomaterials are a widespread class of technologically important materials that are generally incompatible with analysis by atom probe tomography (APT) due to issues with specimen preparation, field evaporation and data reconstruction. The feasibility of encapsulating such non-compact matter in a matrix to enable APT measurements is investigated using nanoparticles as an example. Simulations of field evaporation of a void, and the resulting artifacts in ion trajectory, underpin the requirement that no voids remain after encapsulation. The approach is demonstrated by encapsulating Pt nanoparticles in an ZnO:Al matrix created by atomic layer deposition, a growth technique which offers very high surface coverage and conformality. APT measurements of the Pt nanoparticles are correlated with transmission electron microscopy images and numerical simulations in order to evaluate the accuracy of the APT reconstruction.

  19. Reflections on the projection of ions in atom probe tomography

    CERN Document Server

    De Geuser, Frédéric

    2016-01-01

    There are two main projections used to transform, and reconstruct, field ion micrographs or atom probe tomography data into atomic coordinates at the specimen surface and, subsequently, in three-dimensions. In this article, we present a perspective on the strength of the azimuthal equidistant projection in comparison to the more widely used and well-established point-projection, which underpins data reconstruction in the only commercial software package available currently. After an overview of the reconstruction methodology, we demonstrate that the azimuthal equidistant is not only more accurate, but also more robust with regards to errors on the parameters used to perform the reconstruction and is therefore more likely to yield more accurate tomographic reconstructions.

  20. Phosphorus and boron diffusion paths in polycrystalline silicon gate of a trench-type three-dimensional metal-oxide-semiconductor field effect transistor investigated by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Han, Bin, E-mail: hanbin@imr.tohoku.ac.jp; Takamizawa, Hisashi, E-mail: takamizawa.hisashi@jaea.go.jp; Shimizu, Yasuo; Inoue, Koji; Nagai, Yasuyoshi [The Oarai Center, Institute for Materials Research, Tohoku University, 2145-2 Narita, Oarai, Ibaraki 311-1313 (Japan); Yano, Fumiko [Department of Electrical Engineering, Faculty of Engineering, Tokyo City University, 1-28-1 Tamazutsumi, Setagaya-ku, Tokyo 158-8557 (Japan); Kunimune, Yorinobu [Renesas Semiconductor Manufacturing Co., Ltd., 1120 Shimokuzawa, Sagamihara, Kanagawa 252-5298 (Japan); Inoue, Masao; Nishida, Akio [Renesas Electronics Corporation, 751 Horiguchi, Hitachinaka, Ibaraki 312-8504 (Japan)

    2015-07-13

    The dopant (P and B) diffusion path in n- and p-types polycrystalline-Si gates of trench-type three-dimensional (3D) metal-oxide-semiconductor field-effect transistors (MOSFETs) were investigated using atom probe tomography, based on the annealing time dependence of the dopant distribution at 900 °C. Remarkable differences were observed between P and B diffusion behavior. In the initial stage of diffusion, P atoms diffuse into deeper regions from the implanted region along grain boundaries in the n-type polycrystalline-Si gate. With longer annealing times, segregation of P on the grain boundaries was observed; however, few P atoms were observed within the large grains or on the gate/gate oxide interface distant from grain boundaries. These results indicate that P atoms diffuse along grain boundaries much faster than through the bulk or along the gate/gate oxide interface. On the other hand, in the p-type polycrystalline-Si gate, segregation of B was observed only at the initial stage of diffusion. After further annealing, the B atoms became uniformly distributed, and no clear segregation of B was observed. Therefore, B atoms diffuse not only along the grain boundary but also through the bulk. Furthermore, B atoms diffused deeper than P atoms along the grain boundaries under the same annealing conditions. This information on the diffusion behavior of P and B is essential for optimizing annealing conditions in order to control the P and B distributions in the polycrystalline-Si gates of trench-type 3D MOSFETs.

  1. Characterization of near-field optical probes

    DEFF Research Database (Denmark)

    Vohnsen, Brian; Bozhevolnyi, Sergey I.

    1999-01-01

    Radiation and collection characteristics of four different near-field optical-fiber probes, namely, three uncoated probes and an aluminium-coated small-aperture probe, are investigated and compared. Their radiation properties are characterized by observation of light-induced topography changes...... in a photo-sensitive film illuminated with the probes, and it is confirmed that the radiated optical field is unambigiously confined only for the coated probe. Near-field optical imaging of a standing evanescent-wave pattern is used to compare the detection characteristics of the probes, and it is concluded...... that, for the imaging of optical-field intensity distributions containing predominantly evanescent-wave components, a sharp uncoated tip is the probe of choice. Complementary results obtained with optical phase-conjugation experiments with he uncoated probes are discussed in relation to the probe...

  2. Probing modified gravity with atom-interferometry: A numerical approach

    Science.gov (United States)

    Schlögel, Sandrine; Clesse, Sébastien; Füzfa, André

    2016-05-01

    Refined constraints on chameleon theories are calculated for atom-interferometry experiments, using a numerical approach consisting in solving for a four-region model the static and spherically symmetric Klein-Gordon equation for the chameleon field. By modeling not only the test mass and the vacuum chamber but also its walls and the exterior environment, the method allows one to probe new effects on the scalar field profile and the induced acceleration of atoms. In the case of a weakly perturbing test mass, the effect of the wall is to enhance the field profile and to lower the acceleration inside the chamber by up to 1 order of magnitude. In the thin-shell regime, results are found to be in good agreement with the analytical estimations, when measurements are realized in the immediate vicinity of the test mass. Close to the vacuum chamber wall, the acceleration becomes negative and potentially measurable. This prediction could be used to discriminate between fifth-force effects and systematic experimental uncertainties, by doing the experiment at several key positions inside the vacuum chamber. For the chameleon potential V (ϕ )=Λ4 +α/ϕα and a coupling function A (ϕ )=exp (ϕ /M ), one finds M ≳7 ×1016 GeV , independently of the power-law index. For V (ϕ )=Λ4(1 +Λ /ϕ ), one finds M ≳1014 GeV . A sensitivity of a ˜10-11 m /s2 would probe the model up to the Planck scale. Finally, a proposal for a second experimental setup, in a vacuum room, is presented. In this case, Planckian values of M could be probed provided that a ˜10-10 m /s2 , a limit reachable by future experiments. Our method can easily be extended to constrain other models with a screening mechanism, such as symmetron, dilaton and f(R) theories.

  3. Atomic quantum superposition state generation via optical probing

    DEFF Research Database (Denmark)

    Nielsen, Anne Ersbak Bang; Poulsen, Uffe Vestergaard; Negretti, Antonio;

    2009-01-01

    investigate cavity enhanced probing with continuous beams of both coherent and squeezed light. The stochastic master equations used in the analysis are expressed in terms of the Hamiltonian of the probed system and the interaction between the probed system and the probe field and are thus quite generally...

  4. Estimation of the reconstruction parameters for Atom Probe Tomography

    CERN Document Server

    Gault, Baptiste; Stephenson, Leigh T; Moody, Michael P; Muddle, Barry C; Ringer, Simon P

    2015-01-01

    The application of wide field-of-view detection systems to atom probe experiments emphasizes the importance of careful parameter selection in the tomographic reconstruction of the analysed volume, as the sensitivity to errors rises steeply with increases in analysis dimensions. In this paper, a self-consistent method is presented for the systematic determination of the main reconstruction parameters. In the proposed approach, the compression factor and the field factor are determined using geometrical projections from the desorption images. A 3D Fourier transform is then applied to a series of reconstructions and, comparing to the known material crystallography, the efficiency of the detector is estimated. The final results demonstrate a significant improvement in the accuracy of the reconstructed volumes.

  5. Fabrication of an all-metal atomic force microscope probe

    DEFF Research Database (Denmark)

    Rasmussen, Jan Pihl; Tang, Peter Torben; Hansen, Ole

    1997-01-01

    This paper presents a method for fabrication of an all-metal atomic force microscope probe (tip, cantilever and support) for optical read-out, using a combination of silicon micro-machining and electroforming. The paper describes the entire fabrication process for a nickel AFM-probe. In addition...

  6. Probing Modified Gravity with Atom-Interferometry: a Numerical Approach

    CERN Document Server

    Schlogel, Sandrine; Fuzfa, Andre

    2015-01-01

    Refined constraints on chameleon theories are calculated for atom-interferometry experiments, using a numerical approach consisting in solving for a four-region model the static and spherically symmetric Klein-Gordon equation for the chameleon field. By modeling not only the test mass and the vacuum chamber but also its walls and the exterior environment, the method allows to probe new effects on the scalar field profile and the induced acceleration of atoms. In the case of a weakly perturbing test mass, the effect of the wall is to enhance the field profile and to lower the acceleration inside the chamber by up to one order of magnitude. In the thin-shell regime, significant deviations from the analytical estimations are found, even when measurements are realized in the immediate vicinity of the test mass. Close to the vacuum chamber wall, the acceleration becomes negative and potentially measurable. This prediction could be used to discriminate between fifth-force effects and systematic experimental uncerta...

  7. Atom probe tomography of a commercial light emitting diode

    Science.gov (United States)

    Larson, D. J.; Prosa, T. J.; Olson, D.; Lefebvre, W.; Lawrence, D.; Clifton, P. H.; Kelly, T. F.

    2013-11-01

    The atomic-scale analysis of a commercial light emitting diode device purchased at retail is demonstrated using a local electrode atom probe. Some of the features are correlated with transmission electron microscopy imaging. Subtle details of the structure that are revealed have potential significance for the design and performance of this device.

  8. Correlating Atom Probe Crystallographic Measurements with Transmission Kikuchi Diffraction Data.

    Science.gov (United States)

    Breen, Andrew J; Babinsky, Katharina; Day, Alec C; Eder, K; Oakman, Connor J; Trimby, Patrick W; Primig, Sophie; Cairney, Julie M; Ringer, Simon P

    2017-03-14

    Correlative microscopy approaches offer synergistic solutions to many research problems. One such combination, that has been studied in limited detail, is the use of atom probe tomography (APT) and transmission Kikuchi diffraction (TKD) on the same tip specimen. By combining these two powerful microscopy techniques, the microstructure of important engineering alloys can be studied in greater detail. For the first time, the accuracy of crystallographic measurements made using APT will be independently verified using TKD. Experimental data from two atom probe tips, one a nanocrystalline Al-0.5Ag alloy specimen collected on a straight flight-path atom probe and the other a high purity Mo specimen collected on a reflectron-fitted instrument, will be compared. We find that the average minimum misorientation angle, calculated from calibrated atom probe reconstructions with two different pole combinations, deviate 0.7° and 1.4°, respectively, from the TKD results. The type of atom probe and experimental conditions appear to have some impact on this accuracy and the reconstruction and measurement procedures are likely to contribute further to degradation in angular resolution. The challenges and implications of this correlative approach will also be discussed.

  9. Hollow-atom probing of surfaces

    NARCIS (Netherlands)

    Limburg, J.

    1997-01-01

    This paper discusses the mechanisms governing the formation and decay of hollow atoms in front of (semi) conducting and insulating surfaces. First, the primary neutralization of the highly charged ions is treated in terms of the classical overbarrier model. Different views are presented. Then the mo

  10. Field enhancement effect of metal probe in evanescent field

    Institute of Scientific and Technical Information of China (English)

    Xiaogang Hong; Wendong Xu; Xiaogang Li; Chengqiang Zhao; Xiaodong Tang

    2009-01-01

    Field enhancement effect of metal probe in evanescent field, induced by using a multi-layers structure for exciting surface plasmon resonance (SPR), is analyzed numerically by utilizing two-dimensional (2D) TM wave finite difference time-domain (FDTD) method. In this letter, we used a fundamental mode Gaussian beam to induce evanescent field, and calculated the electric intensity. The results show that compared with the nonmetal probe, the metal probe has a larger field enhancement effect, and its scattering wave induced by field enhancement has a bigger decay coefficient. The field enhancement effect should conclude that the metal probe has an important application in nanolithography.

  11. Atomic scale structure of amorphous aluminum oxyhydroxide, oxide and oxycarbide films probed by very high field (27)Al nuclear magnetic resonance.

    Science.gov (United States)

    Baggetto, L; Sarou-Kanian, V; Florian, P; Gleizes, A N; Massiot, D; Vahlas, C

    2017-03-15

    The atomic scale structure of aluminum in amorphous alumina films processed by direct liquid injection chemical vapor deposition from aluminum tri-isopropoxide (ATI) and dimethyl isopropoxide (DMAI) is investigated by solid-state (27)Al nuclear magnetic resonance (SSNMR) using a very high magnetic field of 20.0 T. This study is performed as a function of the deposition temperature in the range 300-560 °C, 150-450 °C, and 500-700 °C, for the films processed from ATI, DMAI (+H2O), and DMAI (+O2), respectively. While the majority of the films are composed of stoichiometric aluminum oxide, other samples are partially or fully hydroxylated at low temperature, or contain carbidic carbon when processed from DMAI above 500 °C. The quantitative analysis of the SSNMR experiments reveals that the local structure of these films is built from AlO4, AlO5, AlO6 and Al(O,C)4 units with minor proportions of the 6-fold aluminum coordination and significant amounts of oxycarbides in the films processed from DMAI (+O2). The aluminum coordination distribution as well as the chemical shift distribution indicate that the films processed from DMAI present a higher degree of structural disorder compared to the films processed from ATI. Hydroxylation leads to an increase of the 6-fold coordination resulting from the trend of OH groups to integrate into AlO6 units. The evidence of an additional environment in films processed from DMAI (+O2) by (27)Al SSNMR and first-principle NMR calculations on Al4C3 and Al4O4C crystal structures supports that carbon is located in Al(O,C)4 units. The concentration of this coordination environment strongly increases with increasing process temperature from 600 to 700 °C favoring a highly disordered structure and preventing from crystallizing into γ-alumina. The obtained results are a valuable guide to the selection of process conditions for the CVD of amorphous alumina films with regard to targeted applications.

  12. Probing atomic and molecular dynamics from within

    Energy Technology Data Exchange (ETDEWEB)

    Berrah, N. E-mail: berrah@wmich.edu; Bilodeau, R.C.; Ackerman, G.; Bozek, J.D.; Turri, G.; Kukk, E.; Cheng, W.T.; Snell, G

    2004-08-01

    We have investigated with unprecedented levels of detail photodetachment of negative ions and photoionization of molecules using the brightness, spectral resolution, and tunability of the Advanced Light Source at Lawrence Berkeley National Laboratory. In particular, we report here on investigations carried out in K-shell photodetachment of atomic Li{sup -} and He{sup -}. We also report on angular distribution of core-level iodine 4d photoelectrons from the HI molecule. In both cases comparison with calculations is discussed.

  13. Nanoscale Probe of Magnetism Based on Artificial Atoms in Diamond

    Science.gov (United States)

    2014-07-18

    AFRL-OSR-VA-TR-2014-0165 ( YIP 11) Nanoscale probe of magnetism based on artificial atoms in diamond Ania Bleszynski Jayich UNIVERSITY OF CALIFORNIA...center Ania Bleszynski Jayihc (805) 893 8089 AFOSR   YIP  Report     Ania  Bleszynski  Jayich   Nanoscale probe of magnetism based on...dramatically affected by proximal Gd ions. Gd ions are commonly used spin labels for biological imaging. AFOSR   YIP  Report     Ania

  14. Manipulating collective quantum states of ultracold atoms by probing

    DEFF Research Database (Denmark)

    Wade, Andrew Christopher James

    2015-01-01

    nature of the measurement interaction and backaction is yet to be realised. This dissertation is concerned with ultracold atoms and their control via fully quantum mechanical probes. Nonclassical, squeezed and entangled states of matter and single photon sources are important for fundamental studies...

  15. Atom-Probe Measurements of Meteoritic Nanodiamonds and Terrestrial Standards

    Science.gov (United States)

    Lewis, J. B.; Isheim, D.; Floss, C.; Daulton, T. L.; Seidman, D. N.; Heck, P. R.; Davis, A. M.; Pellin, M. J.; Savina, M. R.; Hiller, J.; Mane, A.; Elam, J. W.; Stephan, T.

    2013-09-01

    We present new data from the novel application of atom-probe tomography to the study of nanodiamonds from the meteorite Allende. The mean meteoritic ^12C/^13C peak ratio is higher than that of our standards, but there are instrumental artifacts.

  16. Development of atomic beam probe for tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Berta, M., E-mail: bertam@sze.hu [Széchenyi István University, EURATOM Association, Győr (Hungary); Institute of Plasma Physics AS CR, v.v.i., Prague (Czech Republic); Anda, G.; Aradi, M.; Bencze, A.; Buday, Cs.; Kiss, I.G.; Tulipán, Sz.; Veres, G.; Zoletnik, S. [Wigner – RCP, HAS, EURATOM Association, Budapest (Hungary); Havlícek, J.; Háček, P. [Institute of Plasma Physics AS CR, v.v.i., Prague (Czech Republic); Charles University in Prague, Faculty of Mathematics and Physics (Czech Republic)

    2013-11-15

    Highlights: • ABP is newly developed diagnostic. • Unique measurement method for the determination of plasma edge current variations caused by different transient events such as ELMs. • The design process has been fruitfully supported by the physically motivated computer simulations. • Li-BES system has been modified accordingly to the needs of the ABP. -- Abstract: The concept and development of a new detection method for light alkali ions stemming from diagnostic beams installed on medium size tokamak is described. The method allows us the simultaneous measurement of plasma density fluctuations and fast variations in poloidal magnetic field, therefore one can infer the fast changes in edge plasma current. The concept has been worked out and the whole design process has been done at Wigner RCP. The test detector with appropriate mechanics and electronics is already installed on COMPASS tokamak. General ion trajectory calculation code (ABPIons) has also been developed. Detailed calculations show the possibility of reconstruction of edge plasma current density profile changes with high temporal resolution, and the possibility of density profile reconstruction with better spatial resolution compared to standard Li-BES measurement, this is important for pedestal studies.

  17. New approaches to nanoparticle sample fabrication for atom probe tomography.

    Science.gov (United States)

    Felfer, P; Li, T; Eder, K; Galinski, H; Magyar, A P; Bell, D C; Smith, G D W; Kruse, N; Ringer, S P; Cairney, J M

    2015-12-01

    Due to their unique properties, nano-sized materials such as nanoparticles and nanowires are receiving considerable attention. However, little data is available about their chemical makeup at the atomic scale, especially in three dimensions (3D). Atom probe tomography is able to answer many important questions about these materials if the challenge of producing a suitable sample can be overcome. In order to achieve this, the nanomaterial needs to be positioned within the end of a tip and fixed there so the sample possesses sufficient structural integrity for analysis. Here we provide a detailed description of various techniques that have been used to position nanoparticles on substrates for atom probe analysis. In some of the approaches, this is combined with deposition techniques to incorporate the particles into a solid matrix, and focused ion beam processing is then used to fabricate atom probe samples from this composite. Using these approaches, data has been achieved from 10-20 nm core-shell nanoparticles that were extracted directly from suspension (i.e. with no chemical modification) with a resolution of better than ± 1 nm.

  18. Atomic excitation and recombination in external fields

    Energy Technology Data Exchange (ETDEWEB)

    Nayfeh, M.H.; Clark, C.W.

    1985-01-01

    This volume offers a timely look at Rydberg states of atoms in external fields and dielectronic recombination. Each topic provides authoritative coverage, presents a fresh account of a flourishing field of current atomic physics and introduces new opportunities for discovery and development. Topics considered include electron-atom scattering in external fields; observations of regular and irregular motion as exemplified by the quadratic zeeman effect and other systems; Rydberg atoms in external fields and the Coulomb geometry; crossed-field effects in the absorption spectrum of lithium in a magnetic field; precise studies of static electric field ionization; widths and shapes of stark resonances in sodium above the saddle point; studies of electric field effects and barium autoionizing resonances; autoionization and dielectronic recombination in plasma electric microfields; dielectronic recombination measurements on multicharged ions; merged beam studies of dielectronic recombination; Rydberg atoms and dielectronic recombination in astrophysics; and observations on dielectronic recombination.

  19. High sensitivity probe absorption technique for time-of-flight measurements on cold atoms

    Indian Academy of Sciences (India)

    A K Mohapatra; C S Unnikrishnan

    2006-06-01

    We report on a phase-sensitive probe absorption technique with high sensitivity, capable of detecting a few hundred ultra-cold atoms in flight in an observation time of a few milliseconds. The large signal-to-noise ratio achieved is sufficient for reliable measurements on low intensity beams of cold atoms. We demonstrate the high sensitivity and figure of merit of the simple method by measuring the time-of-flight of atoms moving upwards from a magneto-optical trap released in the gravitational field.

  20. Isotropic Broadband E-Field Probe

    Directory of Open Access Journals (Sweden)

    Béla Szentpáli

    2008-01-01

    Full Text Available An E-field probe has been developed for EMC immunity tests performed in closed space. The leads are flexible resistive transmission lines. Their influence on the field distribution is negligible. The probe has an isotropic reception from 100 MHz to 18 GHz; the sensitivity is in the 3 V/m–10 V/m range. The device is an accessory of the EMC test chamber. The readout of the field magnitude is carried out by personal computer, which fulfils also the required corrections of the raw data.

  1. Visualization of deuterium dead layer by atom probe tomography

    KAUST Repository

    Gemma, Ryota

    2012-12-01

    The first direct observation, by atom probe tomography, of a deuterium dead layer is reported for Fe/V multilayered film loaded with D solute atoms. The thickness of the dead layers was measured to be 0.4-0.5 nm. The dead layers could be distinguished from chemically intermixed layers. The results suggest that the dead layer effect occurs even near the interface of the mixing layers, supporting an interpretation that the dead layer effect cannot be explained solely by electronic charge transfer but also involves a modulation of rigidity. © 2012 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  2. Fast electromagnetic field strength probes

    NARCIS (Netherlands)

    Leferink, Frank; Serra, Ramiro

    2013-01-01

    Diode detectors and thermocouple detectors are conventionally used to measure electromagnetic field strength. Both detectors have some disadvantages for applications where a fast response and a high dynamic range is required. The diode detector is limited in dynamic range. The dynamic range is impor

  3. Probing stem cell differentiation using atomic force microscopy

    Science.gov (United States)

    Liang, Xiaobin; Shi, Xuetao; Ostrovidov, Serge; Wu, Hongkai; Nakajima, Ken

    2016-03-01

    A real-time method using atomic force microscopy (AFM) was developed to probe stem cell differentiation by measuring the mechanical properties of cells and the extracellular matrix (ECM). The mechanical properties of stem cells and their ECMs can be used to clearly distinguish specific stem cell-differentiated lineages. It is clear that AFM is a facile and useful tool for monitoring the differentiation of stem cells in a non-invasive manner.

  4. Detecting and extracting clusters in atom probe data: A simple, automated method using Voronoi cells

    Energy Technology Data Exchange (ETDEWEB)

    Felfer, P., E-mail: peter.felfer@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Ceguerra, A.V., E-mail: anna.ceguerra@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Ringer, S.P., E-mail: simon.ringer@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Cairney, J.M., E-mail: julie.cairney@sydney.edu.au [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia)

    2015-03-15

    The analysis of the formation of clusters in solid solutions is one of the most common uses of atom probe tomography. Here, we present a method where we use the Voronoi tessellation of the solute atoms and its geometric dual, the Delaunay triangulation to test for spatial/chemical randomness of the solid solution as well as extracting the clusters themselves. We show how the parameters necessary for cluster extraction can be determined automatically, i.e. without user interaction, making it an ideal tool for the screening of datasets and the pre-filtering of structures for other spatial analysis techniques. Since the Voronoi volumes are closely related to atomic concentrations, the parameters resulting from this analysis can also be used for other concentration based methods such as iso-surfaces. - Highlights: • Cluster analysis of atom probe data can be significantly simplified by using the Voronoi cell volumes of the atomic distribution. • Concentration fields are defined on a single atomic basis using Voronoi cells. • All parameters for the analysis are determined by optimizing the separation probability of bulk atoms vs clustered atoms.

  5. Sensitivity of atom interferometry to ultralight scalar field dark matter

    CERN Document Server

    Geraci, Andrew A

    2016-01-01

    We discuss the use of atom interferometry as a tool to search for Dark Matter (DM) composed of ultra-light scalar fields. Previous work on ultra-light DM detection using accelerometers has considered the possibility of equivalence principle violating effects whereby gradients in the dark matter field can directly produce relative accelerations between media of differing composition. In atom interferometers, we find that time-varying phase signals from oscillatory, or dilaton-like, DM can also arise due to changes in the atom rest mass that can occur between light-pulses throughout the interferometer sequence as well as changes in the earth's gravitational field. We estimate that several orders of magnitude of unexplored phase space for light DM fields can be probed with our proposed method.

  6. Sensitivity of Atom Interferometry to Ultralight Scalar Field Dark Matter.

    Science.gov (United States)

    Geraci, Andrew A; Derevianko, Andrei

    2016-12-23

    We discuss the use of atom interferometry as a tool to search for dark matter (DM) composed of virialized ultralight fields (VULFs). Previous work on VULF DM detection using accelerometers has considered the possibility of equivalence-principle-violating effects whereby gradients in the dark matter field can directly produce relative accelerations between media of differing composition. In atom interferometers, we find that time-varying phase signals induced by coherent oscillations of DM fields can also arise due to changes in the atom rest mass that can occur between light pulses throughout the interferometer sequence as well as changes in Earth's gravitational field. We estimate that several orders of magnitude of unexplored phase space for VULF DM couplings can be probed due to these new effects.

  7. Probe Amplification with or without Population Inversion in a Five-Level Atomic System with Double-Dark Resonances

    Institute of Scientific and Technical Information of China (English)

    LI Jia-Hua; XIE Xiao-Tao; LUO Jin-Ming; LIU Ji-Bing

    2006-01-01

    @@ We theoretically investigate the response of the probe amplification in a five-level atomic system in the presence of interacting double-dark resonances disturbed by introducing an additional signal field. It is found that a large enhancement of the probe amplification with or without population inversion can be achieved by properly adjusting the strengths of the microwave driving field and the signal laser field. From viewpoint of physics, we qualitatively explain these results in terms of quantum interference and dressed states.

  8. Atomic electric fields revealed by a quantum mechanical approach to electron picodiffraction.

    Science.gov (United States)

    Müller, Knut; Krause, Florian F; Béché, Armand; Schowalter, Marco; Galioit, Vincent; Löffler, Stefan; Verbeeck, Johan; Zweck, Josef; Schattschneider, Peter; Rosenauer, Andreas

    2014-12-15

    By focusing electrons on probes with a diameter of 50 pm, aberration-corrected scanning transmission electron microscopy (STEM) is currently crossing the border to probing subatomic details. A major challenge is the measurement of atomic electric fields using differential phase contrast (DPC) microscopy, traditionally exploiting the concept of a field-induced shift of diffraction patterns. Here we present a simplified quantum theoretical interpretation of DPC. This enables us to calculate the momentum transferred to the STEM probe from diffracted intensities recorded on a pixel array instead of conventional segmented bright-field detectors. The methodical development yielding atomic electric field, charge and electron density is performed using simulations for binary GaN as an ideal model system. We then present a detailed experimental study of SrTiO3 yielding atomic electric fields, validated by comprehensive simulations. With this interpretation and upgraded instrumentation, STEM is capable of quantifying atomic electric fields and high-contrast imaging of light atoms.

  9. Contact resonances of U-shaped atomic force microscope probes

    Energy Technology Data Exchange (ETDEWEB)

    Rezaei, E.; Turner, J. A., E-mail: jaturner@unl.edu [Mechanical and Materials Engineering, University of Nebraska-Lincoln, W342 Nebraska Hall, Lincoln, Nebraska 68588 (United States)

    2016-01-21

    Recent approaches used to characterize the elastic or viscoelastic properties of materials with nanoscale resolution have focused on the contact resonances of atomic force microscope (CR-AFM) probes. The experiments for these CR-AFM methods involve measurement of several contact resonances from which the resonant frequency and peak width are found. The contact resonance values are then compared with the noncontact values in order for the sample properties to be evaluated. The data analysis requires vibration models associated with the probe during contact in order for the beam response to be deconvolved from the measured spectra. To date, the majority of CR-AFM research has used rectangular probes that have a relatively simple vibration response. Recently, U-shaped AFM probes have created much interest because they allow local sample heating. However, the vibration response of these probes is much more complex such that CR-AFM is still in its infancy. In this article, a simplified analytical model of U-shaped probes is evaluated for contact resonance applications relative to a more complex finite element (FE) computational model. The tip-sample contact is modeled using three orthogonal Kelvin-Voigt elements such that the resonant frequency and peak width of each mode are functions of the contact conditions. For the purely elastic case, the frequency results of the simple model are within 8% of the FE model for the lowest six modes over a wide range of contact stiffness values. Results for the viscoelastic contact problem for which the quality factor of the lowest six modes is compared show agreement to within 13%. These results suggest that this simple model can be used effectively to evaluate CR-AFM experimental results during AFM scanning such that quantitative mapping of viscoelastic properties may be possible using U-shaped probes.

  10. Quantification of in-contact probe-sample electrostatic forces with dynamic atomic force microscopy

    Science.gov (United States)

    Balke, Nina; Jesse, Stephen; Carmichael, Ben; Baris Okatan, M.; Kravchenko, Ivan I.; Kalinin, Sergei V.; Tselev, Alexander

    2017-02-01

    Atomic force microscopy (AFM) methods utilizing resonant mechanical vibrations of cantilevers in contact with a sample surface have shown sensitivities as high as few picometers for detecting surface displacements. Such a high sensitivity is harnessed in several AFM imaging modes. Here, we demonstrate a cantilever-resonance-based method to quantify electrostatic forces on a probe in the probe-sample junction in the presence of a surface potential or when a bias voltage is applied to the AFM probe. We find that the electrostatic forces acting on the probe tip apex can produce signals equivalent to a few pm of surface displacement. In combination with modeling, the measurements of the force were used to access the strength of the electrical field at the probe tip apex in contact with a sample. We find an evidence that the electric field strength in the junction can reach ca. 1 V nm-1 at a bias voltage of a few volts and is limited by non-ideality of the tip-sample contact. This field is sufficiently strong to significantly influence material states and kinetic processes through charge injection, Maxwell stress, shifts of phase equilibria, and reduction of energy barriers for activated processes. Besides, the results provide a baseline for accounting for the effects of local electrostatic forces in electromechanical AFM measurements as well as offer additional means to probe ionic mobility and field-induced phenomena in solids.

  11. Control of Goos-Hänchen shift via input probe field intensity

    Science.gov (United States)

    Ziauddin; Lee, Ray-Kuang; Qamar, Sajid

    2016-11-01

    We suggest a scheme to control Goos-Hänchen (GH) shift in an ensemble of strongly interacting Rydberg atoms, which act as super-atoms due to the dipole blockade mechanism. The ensemble of three-level cold Rydberg-dressed (87Rb) atoms follows a cascade configurations where two fields, i.e, a strong control and a weak field are employed [D. Petrosyan, J. Otterbach, and M. Fleischhauer, Phys. Rev. Lett. 107, 213601 (2011)]. The propagation of probe field is influenced by two-photon correlation within the blockade distance, which are damped due to the saturation of super-atoms. The amplitude of GH shift in the reflected light depends on the intensity of probe field. We observe large negative GH shift in the reflected light for small values of the probe field intensities.

  12. Antenna Near-Field Probe Station Scanner

    Science.gov (United States)

    Zaman, Afroz J. (Inventor); Lee, Richard Q. (Inventor); Darby, William G. (Inventor); Barr, Philip J. (Inventor); Lambert, Kevin M (Inventor); Miranda, Felix A. (Inventor)

    2011-01-01

    A miniaturized antenna system is characterized non-destructively through the use of a scanner that measures its near-field radiated power performance. When taking measurements, the scanner can be moved linearly along the x, y and z axis, as well as rotationally relative to the antenna. The data obtained from the characterization are processed to determine the far-field properties of the system and to optimize the system. Each antenna is excited using a probe station system while a scanning probe scans the space above the antenna to measure the near field signals. Upon completion of the scan, the near-field patterns are transformed into far-field patterns. Along with taking data, this system also allows for extensive graphing and analysis of both the near-field and far-field data. The details of the probe station as well as the procedures for setting up a test, conducting a test, and analyzing the resulting data are also described.

  13. New atom probe approaches to studying segregation in nanocrystalline materials.

    Science.gov (United States)

    Samudrala, S K; Felfer, P J; Araullo-Peters, V J; Cao, Y; Liao, X Z; Cairney, J M

    2013-09-01

    Atom probe is a technique that is highly suited to the study of nanocrystalline materials. It can provide accurate atomic-scale information about the composition of grain boundaries in three dimensions. In this paper we have analysed the microstructure of a nanocrystalline super-duplex stainless steel prepared by high pressure torsion (HPT). Not all of the grain boundaries in this alloy display obvious segregation, making visualisation of the microstructure challenging. In addition, the grain boundaries present in the atom probe data acquired from this alloy have complex shapes that are curved at the scale of the dataset and the interfacial excess varies considerably over the boundaries, making the accurate characterisation of the distribution of solute challenging using existing analysis techniques. In this paper we present two new data treatment methods that allow the visualisation of boundaries with little or no segregation, the delineation of boundaries for further analysis and the quantitative analysis of Gibbsian interfacial excess at boundaries, including the capability of excess mapping.

  14. New atom probe approaches to studying segregation in nanocrystalline materials

    Energy Technology Data Exchange (ETDEWEB)

    Samudrala, S.K.; Felfer, P.J.; Araullo-Peters, V.J. [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006 (Australia); The Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); Cao, Y.; Liao, X.Z. [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006 (Australia); Cairney, J.M., E-mail: julie.cairney@sydney.edu.au [School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney, NSW 2006 (Australia); The Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia)

    2013-09-15

    Atom probe is a technique that is highly suited to the study of nanocrystalline materials. It can provide accurate atomic-scale information about the composition of grain boundaries in three dimensions. In this paper we have analysed the microstructure of a nanocrystalline super-duplex stainless steel prepared by high pressure torsion (HPT). Not all of the grain boundaries in this alloy display obvious segregation, making visualisation of the microstructure challenging. In addition, the grain boundaries present in the atom probe data acquired from this alloy have complex shapes that are curved at the scale of the dataset and the interfacial excess varies considerably over the boundaries, making the accurate characterisation of the distribution of solute challenging using existing analysis techniques. In this paper we present two new data treatment methods that allow the visualisation of boundaries with little or no segregation, the delineation of boundaries for further analysis and the quantitative analysis of Gibbsian interfacial excess at boundaries, including the capability of excess mapping. - Highlights: ► New data treatment methods allow delineation of grain boundaries, even without segregation. ► Proxigrams calculated from the surfaces accurately show the extent of segregation. ► Tessellation of the data volume can be used to map the Gibbsian interfacial excess.

  15. Pulsed-laser atom probe studies of a precipitation hardened maraging TRIP steel.

    Science.gov (United States)

    Dmitrieva, O; Choi, P; Gerstl, S S A; Ponge, D; Raabe, D

    2011-05-01

    A precipitation hardened maraging TRIP steel was analyzed using a pulsed laser atom probe. The laser pulse energy was varied from 0.3 to 1.9 nJ to study its effect on the measured chemical compositions and spatial resolution. Compositional analyses using proximity histograms did not show any significant variations in the average matrix and precipitate compositions. The only remarkable change in the atom probe data was a decrease in the ++/+ charge state ratios of the elements. The values of the evaporation field used for the reconstructions exhibit a linear dependence on the laser pulse energy. The adjustment of the evaporation fields used in the reconstructions for different laser pulse energies was based on the correlation of the obtained cluster shapes to the TEM observations. No influence of laser pulse energy on chemical composition of the precipitates and on the chemical sharpness of their interfaces was detected.

  16. Multifunctional hydrogel nano-probes for atomic force microscopy

    Science.gov (United States)

    Lee, Jae Seol; Song, Jungki; Kim, Seong Oh; Kim, Seokbeom; Lee, Wooju; Jackman, Joshua A.; Kim, Dongchoul; Cho, Nam-Joon; Lee, Jungchul

    2016-05-01

    Since the invention of the atomic force microscope (AFM) three decades ago, there have been numerous advances in its measurement capabilities. Curiously, throughout these developments, the fundamental nature of the force-sensing probe--the key actuating element--has remained largely unchanged. It is produced by long-established microfabrication etching strategies and typically composed of silicon-based materials. Here, we report a new class of photopolymerizable hydrogel nano-probes that are produced by bottom-up fabrication with compressible replica moulding. The hydrogel probes demonstrate excellent capabilities for AFM imaging and force measurement applications while enabling programmable, multifunctional capabilities based on compositionally adjustable mechanical properties and facile encapsulation of various nanomaterials. Taken together, the simple, fast and affordable manufacturing route and multifunctional capabilities of hydrogel AFM nano-probes highlight the potential of soft matter mechanical transducers in nanotechnology applications. The fabrication scheme can also be readily utilized to prepare hydrogel cantilevers, including in parallel arrays, for nanomechanical sensor devices.

  17. Interface study of FeMgOFe magnetic tunnel junctions using 3D Atom Probe

    CERN Document Server

    Mazumder, B; Vella, A; Vurpillot, F; Deconihout, B

    2011-01-01

    A detailed interface study was conducted on a Fe/MgO/Fe system using laser assisted 3D atom probe. It exhibits an additional oxide formation at the second interface of the multilayer structure independent of laser wavelength, laser fluence and the thickness of the tunnel barrier. We have shown with the help of simulation that this phenomena is caused by the field evaporation of two layers having two different evaporation

  18. Design of cantilever probes for Atomic Force Microscopy (AFM)

    DEFF Research Database (Denmark)

    Pedersen, Niels Leergaard

    2000-01-01

    A cantilever beam used in an Atomic Force Microscope is optimized with respect to two different objectives. The first goal is to maximize the first eigenfrequency while keeping the stiffness of the probe constant. The second goal is to maximize the tip angle of the first eigenmode while again...... keeping the stiffness constant. The resulting design of the beam from the latter optimization gives almost the same result as when maximizing the first eigenfrequency. Adding a restriction on the second eigenfrequency result in a significant change of the optimal design. The beam is modelled with 12 DOF...

  19. Towards an accurate volume reconstruction in atom probe tomography.

    Science.gov (United States)

    Beinke, Daniel; Oberdorfer, Christian; Schmitz, Guido

    2016-06-01

    An alternative concept for the reconstruction of atom probe data is outlined. It is based on the calculation of realistic trajectories of the evaporated ions in a recursive refinement process. To this end, the electrostatic problem is solved on a Delaunay tessellation. To enable the trajectory calculation, the order of reconstruction is inverted with respect to previous reconstruction schemes: the last atom detected is reconstructed first. In this way, the emitter shape, which controls the trajectory, can be defined throughout the duration of the reconstruction. A proof of concept is presented for 3D model tips, containing spherical precipitates or embedded layers of strongly contrasting evaporation thresholds. While the traditional method following Bas et al. generates serious distortions in these cases, a reconstruction with the proposed electrostatically informed approach improves the geometry of layers and particles significantly.

  20. Pulsed-laser atom probe studies of a precipitation hardened maraging TRIP steel

    Energy Technology Data Exchange (ETDEWEB)

    Dmitrieva, O., E-mail: o.dmitrieva@mpie.de [Max-Planck-Institute for Iron Research, Max-Planck-Str. 1, 40237 Duesseldorf (Germany); Choi, P., E-mail: p.choi@mpie.de [Max-Planck-Institute for Iron Research, Max-Planck-Str. 1, 40237 Duesseldorf (Germany); Gerstl, S.S.A. [Imago Scientific Instruments, Madison, WI 53711 (United States); Ponge, D.; Raabe, D. [Max-Planck-Institute for Iron Research, Max-Planck-Str. 1, 40237 Duesseldorf (Germany)

    2011-05-15

    A precipitation hardened maraging TRIP steel was analyzed using a pulsed laser atom probe. The laser pulse energy was varied from 0.3 to 1.9 nJ to study its effect on the measured chemical compositions and spatial resolution. Compositional analyses using proximity histograms did not show any significant variations in the average matrix and precipitate compositions. The only remarkable change in the atom probe data was a decrease in the ++/+ charge state ratios of the elements. The values of the evaporation field used for the reconstructions exhibit a linear dependence on the laser pulse energy. The adjustment of the evaporation fields used in the reconstructions for different laser pulse energies was based on the correlation of the obtained cluster shapes to the TEM observations. No influence of laser pulse energy on chemical composition of the precipitates and on the chemical sharpness of their interfaces was detected. -- Research highlights: {yields} Changing the laser pulse energy in pulsed-laser atom probe could induce some changes in the analysis results of complex steels. {yields} Decreases in the evaporation fields and the ++/+ charge state ratios were detected with raising laser energy. {yields} Chemical composition of the intermetallic precipitates and the interface sharpness were not influenced by changing the laser energy.

  1. Atom probe tomography simulations and density functional theory calculations of bonding energies in Cu3Au

    KAUST Repository

    Boll, Torben

    2012-10-01

    In this article the Cu-Au binding energy in Cu3Au is determined by comparing experimental atom probe tomography (APT) results to simulations. The resulting bonding energy is supported by density functional theory calculations. The APT simulations are based on the Müller-Schottky equation, which is modified to include different atomic neighborhoods and their characteristic bonds. The local environment is considered up to the fifth next nearest neighbors. To compare the experimental with simulated APT data, the AtomVicinity algorithm, which provides statistical information about the positions of the neighboring atoms, is applied. The quality of this information is influenced by the field evaporation behavior of the different species, which is connected to the bonding energies. © Microscopy Society of America 2012.

  2. Materials applications of an advanced 3-dimensional atom probe

    Energy Technology Data Exchange (ETDEWEB)

    Cerezo, A. [Oxford Univ. (United Kingdom). Dept. of Materials; Gibuoin, D. [Oxford Univ. (United Kingdom). Dept. of Materials; Kim, S. [Oxford Univ. (United Kingdom). Dept. of Materials; Sijbrandij, S.J. [Oxford Univ. (United Kingdom). Dept. of Materials; Venker, F.M. [Oxford Univ. (United Kingdom). Dept. of Materials]|[Rijksuniversiteit Groningen (Netherlands). Dept. of Applied Physics; Warren, P.J. [Oxford Univ. (United Kingdom). Dept. of Materials; Wilde, J. [Oxford Univ. (United Kingdom). Dept. of Materials; Smith, G.D.W. [Oxford Univ. (United Kingdom). Dept. of Materials

    1996-09-01

    An advanced 3-dimensional atom probe system has been constructed, based on an optical position-sensitive atom probe (OPoSAP) detector with energy compensation using a reflectron lens. The multi-hit detection capability of the OPoSAP leads to significant improvements in the efficiency of the instrument over the earlier serial position-sensing system. Further gains in efficiency are obtained by using a biassed grid in front of the detector to collect secondary electrons generated when ions strike the interchannel area. The improvement in detection efficiency gives enhanced performance in the studies of ordered materials and the determination of site occupation. Energy compensation leads to a much improved mass resolution (m/{Delta}m=500 full width at half maximum) making it possible to map out the 3-dimensional spatial distributions of all the elements in complex engineering alloys, even when elements lie close together in the mass spectrum. For example, in the analysis of a maraging steel, this allows separation between the {sup 61}Ni{sup 2+} and {sup 92}Mo{sup 3+} peaks, which are only 1/6 of a mass unit apart. (orig.).

  3. Probing the energy flow in Bessel light beams using atomic photoionization

    Science.gov (United States)

    Surzhykov, A.; Seipt, D.; Fritzsche, S.

    2016-09-01

    The growing interest in twisted light beams also requires a better understanding of their complex internal structure. Particular attention is currently being given to the energy circulation in these beams as usually described by the Poynting vector field. In the present study we propose to use the photoionization of alkali-metal atoms as a probe process to measure (and visualize) the energy flow in twisted light fields. Such measurements are possible since the angular distribution of photoelectrons, emitted from a small atomic target, appears sensitive to and is determined by the local direction of the Poynting vector. To illustrate the feasibility of the proposed method, detailed calculations were performed for the ionization of sodium atoms by nondiffractive Bessel beams.

  4. Atom-probe for FinFET dopant characterization

    Energy Technology Data Exchange (ETDEWEB)

    Kambham, A.K., E-mail: kambham@imec.be [K.U.Leuven, Instituut voor Kern-en Stralings fysika, Celestijnenlaan 200D, B-3001, Leuven (Belgium); IMEC, Kapeldreef 75, B-3001 Leuven (Belgium); Mody, J.; Gilbert, M.; Koelling, S.; Vandervorst, W. [K.U.Leuven, Instituut voor Kern-en Stralings fysika, Celestijnenlaan 200D, B-3001, Leuven (Belgium); IMEC, Kapeldreef 75, B-3001 Leuven (Belgium)

    2011-05-15

    With the continuous shrinking of transistors and advent of new transistor architectures to keep in pace with Moore's law and ITRS goals, there is a rising interest in multigate 3D-devices like FinFETs where the channel is surrounded by gates on multiple surfaces. The performance of these devices depends on the dimensions and the spatial distribution of dopants in source/drain regions of the device. As a result there is a need for new metrology approach/technique to characterize quantitatively the dopant distribution in these devices with nanometer precision in 3D. In recent years, atom probe tomography (APT) has shown its ability to analyze semiconductor and thin insulator materials effectively with sub-nm resolution in 3D. In this paper we will discuss the methodology used to study FinFET-based structures using APT. Whereas challenges and solutions for sample preparation linked to the limited fin dimensions already have been reported before, we report here an approach to prepare fin structures for APT, which based on their processing history (trenches filled with Si) are in principle invisible in FIB and SEM. Hence alternative solutions in locating and positioning them on the APT-tip are presented. We also report on the use of the atom probe results on FinFETs to understand the role of different dopant implantation angles (10{sup o} and 45{sup o}) when attempting conformal doping of FinFETs and provide a quantitative comparison with alternative approaches such as 1D secondary ion mass spectrometry (SIMS) and theoretical model values. -- Research highlights: {yields} This paper provides the information on how to characterize the FinFET devices using atom probe tomography (APT). {yields} Importance of this work is to assess the performance of these devices at different processing conditions by extracting the compositional profiles. {yields} The performance of these devices depends on the dimensions and the spatial distribution of dopants in source/drain regions

  5. Role of strongly modulated coherence in transient evolution dynamics of probe absorption in a three-level atomic system

    Science.gov (United States)

    Panchadhyayee, Pradipta

    2013-11-01

    We investigate the dynamical behaviour of atomic response in a closed three-level V-type atomic system with the variation of different relevant parameters to exhibit transient evolution of absorption, gain and transparency in the probe response. The oscillations in probe absorption and gain can be efficiently modulated by changing the values of the Rabi frequency, detuning and the collective phase involved in the system. The interesting outcome of the work is the generation of coherence controlled loop-structure with varying amplitudes in the oscillatory probe response of the probe field at various parameter conditions. The prominence of these structures is observed when the coherence induced in a one-photon excitation path is strongly modified by two-step excitations driven by the coherent fields operating in closed interaction contour. In contrast to purely resonant case, the time interval between two successive loops gets significantly reduced with the application of non-zero detuning in the coherent fields.

  6. Train of high-power femtosecond pulses: Probe wave in a gas of prepared atoms

    Science.gov (United States)

    Muradyan, Gevorg; Muradyan, Atom Zh.

    2009-09-01

    We present a method for generating a regular train of ultrashort optical pulses in a prepared two-level medium. The train develops from incident monochromatic probe radiation traveling in a medium of atoms, which are in a quantum mechanical superposition of dressed internal states. In the frame of linear theory for the probe radiation, the energy of individual pulses is an exponentially growing function of atom density and of interaction cross section. Pulse repetition rate is determined by the pump field’s generalized Rabi frequency and can be around 1 THz and greater. We also show that the terms, extra to the dipole approximation, endow the gas by a new property: nonsaturating dependence of refractive index on dressing monochromatic field intensity. Contribution of these nonsaturating terms can be compatible with the main dipole approximation term contribution in the wavelength region of about ten micrometers (the range of CO2 laser) or larger.

  7. A computational geometry framework for the optimisation of atom probe reconstructions.

    Science.gov (United States)

    Felfer, Peter; Cairney, Julie

    2016-10-01

    In this paper, we present pathways for improving the reconstruction of atom probe data on a coarse (>10nm) scale, based on computational geometry. We introduce a way to iteratively improve an atom probe reconstruction by adjusting it, so that certain known shape criteria are fulfilled. This is achieved by creating an implicit approximation of the reconstruction through a barycentric coordinate transform. We demonstrate the application of these techniques to the compensation of trajectory aberrations and the iterative improvement of the reconstruction of a dataset containing a grain boundary. We also present a method for obtaining a hull of the dataset in both detector and reconstruction space. This maximises data utilisation, and can be used to compensate for ion trajectory aberrations caused by residual fields in the ion flight path through a 'master curve' and correct for overall shape deviations in the data.

  8. Atom-probe for FinFET dopant characterization.

    Science.gov (United States)

    Kambham, A K; Mody, J; Gilbert, M; Koelling, S; Vandervorst, W

    2011-05-01

    With the continuous shrinking of transistors and advent of new transistor architectures to keep in pace with Moore's law and ITRS goals, there is a rising interest in multigate 3D-devices like FinFETs where the channel is surrounded by gates on multiple surfaces. The performance of these devices depends on the dimensions and the spatial distribution of dopants in source/drain regions of the device. As a result there is a need for new metrology approach/technique to characterize quantitatively the dopant distribution in these devices with nanometer precision in 3D. In recent years, atom probe tomography (APT) has shown its ability to analyze semiconductor and thin insulator materials effectively with sub-nm resolution in 3D. In this paper we will discuss the methodology used to study FinFET-based structures using APT. Whereas challenges and solutions for sample preparation linked to the limited fin dimensions already have been reported before, we report here an approach to prepare fin structures for APT, which based on their processing history (trenches filled with Si) are in principle invisible in FIB and SEM. Hence alternative solutions in locating and positioning them on the APT-tip are presented. We also report on the use of the atom probe results on FinFETs to understand the role of different dopant implantation angles (10° and 45°) when attempting conformal doping of FinFETs and provide a quantitative comparison with alternative approaches such as 1D secondary ion mass spectrometry (SIMS) and theoretical model values.

  9. Controlling residual hydrogen gas in mass spectra during pulsed laser atom probe tomography.

    Science.gov (United States)

    Kolli, R Prakash

    2017-01-01

    Residual hydrogen (H2) gas in the analysis chamber of an atom probe instrument limits the ability to measure H concentration in metals and alloys. Measuring H concentration would permit quantification of important physical phenomena, such as hydrogen embrittlement, corrosion, hydrogen trapping, and grain boundary segregation. Increased insight into the behavior of residual H2 gas on the specimen tip surface in atom probe instruments could help reduce these limitations. The influence of user-selected experimental parameters on the field adsorption and desorption of residual H2 gas on nominally pure copper (Cu) was studied during ultraviolet pulsed laser atom probe tomography. The results indicate that the total residual hydrogen concentration, HTOT, in the mass spectra exhibits a generally decreasing trend with increasing laser pulse energy and increasing laser pulse frequency. Second-order interaction effects are also important. The pulse energy has the greatest influence on the quantity HTOT, which is consistently less than 0.1 at.% at a value of 80 pJ.

  10. Field theory for trapped atomic gases

    NARCIS (Netherlands)

    Stoof, H.T.C.

    2001-01-01

    In this course we give a selfcontained introduction to the quantum field theory for trapped atomic gases, using functional methods throughout. We consider both equilibrium and nonequilibrium phenomena. In the equilibrium case, we first derive the appropriate Hartree-Fock theory for the properties of

  11. Field theory for trapped atomic gases

    NARCIS (Netherlands)

    Stoof, H.T.C.

    2001-01-01

    In this course we give a selfcontained introduction to the quantum field theory for trapped atomic gases, using functional methods throughout. We consider both equilibrium and nonequilibrium phenomena. In the equilibrium case, we first derive the appropriate Hartree—Fock theory for the properties of

  12. Aspects of probe correction for odd-order probes in spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Laitinen, Tommi; Pivnenko, Sergey N.; Breinbjerg, Olav

    2004-01-01

    Probe correction aspects for the spherical near-field antenna measurements are investigated. First, the spherical mode analyses of the radiated fields of several antennas are performed. It is shown that many common antennas are essentially so-called odd-order antennas. Second, the errors caused...... by the use of the first-order probe correction [1] for a rectangular waveguide probe, that is an odd-order antenna, are demonstrated. Third, a recently developed probe correction technique for odd-order probes is applied for the rectangular waveguide probe and shown to provide accurate results....

  13. Magnetoencephalography with a two-color pump probe atomic magnetometer.

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Cort N.

    2010-07-01

    The authors have detected magnetic fields from the human brain with a compact, fiber-coupled rubidium spin-exchange-relaxation-free magnetometer. Optical pumping is performed on the D1 transition and Faraday rotation is measured on the D2 transition. The beams share an optical axis, with dichroic optics preparing beam polarizations appropriately. A sensitivity of <5 fT/{radical}Hz is achieved. Evoked responses resulting from median nerve and auditory stimulation were recorded with the atomic magnetometer. Recordings were validated by comparison with those taken by a commercial magnetoencephalography system. The design is amenable to arraying sensors around the head, providing a framework for noncryogenic, whole-head magnetoencephalography.

  14. Atomic parity violation in one single trapped radium ion as a probe of electroweak running

    Energy Technology Data Exchange (ETDEWEB)

    Wansbeek, Lotje; Versolato, Oscar; Willmann, Lorenz; Timmermans, Rob; Jungmann, Klaus [KVI, University of Groningen (Netherlands)

    2008-07-01

    In a single trapped and laser cooled radium ion we investigate atomic parity violation by probing the differential splitting (*light shifts*) of the 7S and 6D Zeeman levels, which is caused by the interaction of the ion with an off-resonant laser light field. This experiment serves as a low-energy test of the electroweak Standard Model of particle physics. With precision RF spectroscopy and subsequent monitoring of quantum jumps, this splitting can be determined to sub-Hertz accuracy. A proof-of-principle has recently been given for the barium ion, and crucial ideas are being extended to Ra{sup +} which is a superior candidate.

  15. Mapping energetics of atom probe evaporation events through first principles calculations.

    Science.gov (United States)

    Peralta, Joaquín; Broderick, Scott R; Rajan, Krishna

    2013-09-01

    The purpose of this work is to use atomistic modeling to determine accurate inputs into the atom probe tomography (APT) reconstruction process. One of these inputs is evaporation field; however, a challenge occurs because single ions and dimers have different evaporation fields. We have calculated the evaporation field of Al and Sc ions and Al-Al and Al-Sc dimers from an L1₂-Al₃Sc surface using ab initio calculations and with a high electric field applied to the surface. The evaporation field is defined as the electric field at which the energy barrier size is calculated as zero, corresponding to the minimum field that atoms from the surface can break their bonds and evaporate from the surface. The evaporation field of the surface atoms are ranked from least to greatest as: Al-Al dimer, Al ion, Sc ion, and Al-Sc dimer. The first principles results were compared with experimental data in the form of an ion evaporation map, which maps multi-ion evaporations. From the ion evaporation map of L1₂-Al₃Sc, we extract relative evaporation fields and identify that an Al-Al dimer has a lower evaporation field than an Al-Sc dimer. Additionally, comparatively an Al-Al surface dimer is more likely to evaporate as a dimer, while an Al-Sc surface dimer is more likely to evaporate as single ions. These conclusions from the experiment agree with the ab initio calculations, validating the use of this approach for modeling APT energetics.

  16. Probing non-Hermitian physics with flying atoms

    Science.gov (United States)

    Wen, Jianming; Xiao, Yanhong; Peng, Peng; Cao, Wanxia; Shen, Ce; Qu, Weizhi; Jiang, Liang

    2016-05-01

    Non-Hermtian optical systems with parity-time (PT) symmetry provide new means for light manipulation and control. To date, most of experimental demonstrations on PT symmetry rely on advanced nanotechnologies and sophisticated fabrication techniques to manmade solid-state materials. Here, we report the first experimental realization of optical anti-PT symmetry, a counterpart of conventional PT symmetry, in a warm atomic-vapor cell. By exploiting rapid coherence transport via flying atoms, we observe essential features of anti-PT symmetry with an unprecedented precision on phase-transition threshold. Moreover, our system allows nonlocal interference of two spatially-separated fields as well as anti-PT assisted four-wave mixing. Besides, another intriguing feature offered by the system is refractionless (or unit-refraction) light propagation. Our results thus represent a significant advance in non-Hermitian physics by bridging a firm connection with the AMO field, where novel phenomena and applications in quantum and nonlinear optics aided by (anti-)PT symmetry can be anticipated.

  17. Multiple membrane tethers probed by atomic force microscopy.

    Science.gov (United States)

    Sun, Mingzhai; Graham, John S; Hegedüs, Balazs; Marga, Françoise; Zhang, Ying; Forgacs, Gabor; Grandbois, Michel

    2005-12-01

    Using the atomic force microscope to locally probe the cell membrane, we observed the formation of multiple tethers (thin nanotubes, each requiring a similar pulling force) as reproducible features within force profiles recorded on individual cells. Forces obtained with Chinese hamster ovary cells, a malignant human brain tumor cell line, and human endothelial cells (EA hy926) were found to be 28 +/- 10 pN, 29 +/- 9 pN, and 29 +/- 10 pN, respectively, independent of the nature of attachment to the cantilever. The rather large variation of the tether pulling forces measured at several locations on individual cells points to the existence of heterogeneity in the membrane properties of a morphologically homogeneous cell. Measurement of the summary lengths of the simultaneously extracted tethers provides a measure of the size of the available membrane reservoir through which co-existing tethers are associated. As expected, partial disruption of the actin cytoskeleton and removal of the hyaluronan backbone of the glycocalyx were observed to result in a marked decrease (30-50%) in the magnitude and a significant sharpening of the force distribution indicating reduced heterogeneity of membrane properties. Taken together, our results demonstrate the ability of the plasma membrane to locally produce multiple interdependent tethers-a process that could play an important role in the mechanical association of cells with their environment.

  18. Atom-probe tomography analyses of niobium superconducting RF cavity materials

    Energy Technology Data Exchange (ETDEWEB)

    Sebastian, J.T. [Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108 (United States); Seidman, D.N. [Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108 (United States); Yoon, K.E. [Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208-3108 (United States)]. E-mail: megabass@northwestern.edu; Bauer, P. [Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Reid, T. [Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Boffo, C. [Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States); Norem, J. [Argonne National Laboratory, Argonne, IL 60439 (United States)

    2006-07-15

    We present the first atom-probe tomographic (APT) measurements of niobium superconducting RF (SCRF) cavity materials. APT involves the atom-by-atom dissection of sharply pointed niobium tips, along with their niobium oxide coatings, via the application of a high-pulsed electric field and the measurement of each ion's mass-to-charge state ratio (m/n) with time-of-flight (TOF) mass spectrometry. The resulting atomic reconstructions, typically containing at least 10{sup 5} atoms and with typical dimensions of 10{sup 5} nm{sup 3} (or less), show the detailed, nanoscale chemistry of the niobium oxide coatings, and of the underlying high-purity niobium metal. Our initial results show a nanochemically smooth transition through the oxide layer from near-stoichiometric Nb{sub 2}O{sub 5} at the surface to near-stoichiometric Nb{sub 2}O as the underlying metal is approached (after {approx}10 nm of surface oxide). The underlying metal, in the near-oxide region, contains a significant amount of interstitially dissolved oxygen ({approx}5-10 at.%), as well as a considerable amount of dissolved hydrogen. The experimental results are interpreted in light of current models of oxide and sub-oxide formation in the Nb-O system.

  19. Boosting the local anodic oxidation of silicon through carbon nanofiber atomic force microscopy probes

    Directory of Open Access Journals (Sweden)

    Gemma Rius

    2015-01-01

    Full Text Available Many nanofabrication methods based on scanning probe microscopy have been developed during the last decades. Local anodic oxidation (LAO is one of such methods: Upon application of an electric field between tip and surface under ambient conditions, oxide patterning with nanometer-scale resolution can be performed with good control of dimensions and placement. LAO through the non-contact mode of atomic force microscopy (AFM has proven to yield a better resolution and tip preservation than the contact mode and it can be effectively performed in the dynamic mode of AFM. The tip plays a crucial role for the LAO-AFM, because it regulates the minimum feature size and the electric field. For instance, the feasibility of carbon nanotube (CNT-functionalized tips showed great promise for LAO-AFM, yet, the fabrication of CNT tips presents difficulties. Here, we explore the use of a carbon nanofiber (CNF as the tip apex of AFM probes for the application of LAO on silicon substrates in the AFM amplitude modulation dynamic mode of operation. We show the good performance of CNF-AFM probes in terms of resolution and reproducibility, as well as demonstration that the CNF apex provides enhanced conditions in terms of field-induced, chemical process efficiency.

  20. Boosting the local anodic oxidation of silicon through carbon nanofiber atomic force microscopy probes.

    Science.gov (United States)

    Rius, Gemma; Lorenzoni, Matteo; Matsui, Soichiro; Tanemura, Masaki; Perez-Murano, Francesc

    2015-01-01

    Many nanofabrication methods based on scanning probe microscopy have been developed during the last decades. Local anodic oxidation (LAO) is one of such methods: Upon application of an electric field between tip and surface under ambient conditions, oxide patterning with nanometer-scale resolution can be performed with good control of dimensions and placement. LAO through the non-contact mode of atomic force microscopy (AFM) has proven to yield a better resolution and tip preservation than the contact mode and it can be effectively performed in the dynamic mode of AFM. The tip plays a crucial role for the LAO-AFM, because it regulates the minimum feature size and the electric field. For instance, the feasibility of carbon nanotube (CNT)-functionalized tips showed great promise for LAO-AFM, yet, the fabrication of CNT tips presents difficulties. Here, we explore the use of a carbon nanofiber (CNF) as the tip apex of AFM probes for the application of LAO on silicon substrates in the AFM amplitude modulation dynamic mode of operation. We show the good performance of CNF-AFM probes in terms of resolution and reproducibility, as well as demonstration that the CNF apex provides enhanced conditions in terms of field-induced, chemical process efficiency.

  1. Wideband scalable probe for Spherical Near-Field Antenna measurements

    DEFF Research Database (Denmark)

    Kim, Oleksiy S.; Pivnenko, Sergey; Breinbjerg, Olav

    2011-01-01

    The paper presents a design of an open-boundary quad-ridged horn to be used as a wideband scalable dual-linearly polarized probe for spherical near-field antenna measurements. With a new higher-order probe correction technique developed at the Technical University of Denmark, the probe will enabl...

  2. Attosecond probing of state-resolved ionization and superpositions of atoms and molecules

    Science.gov (United States)

    Leone, Stephen

    2016-05-01

    Isolated attosecond pulses in the extreme ultraviolet are used to probe strong field ionization and to initiate electronic and vibrational superpositions in atoms and small molecules. Few-cycle 800 nm pulses produce strong-field ionization of Xe atoms, and the attosecond probe is used to measure the risetimes of the two spin orbit states of the ion on the 4d inner shell transitions to the 5p vacancies in the valence shell. Step-like features in the risetimes due to the subcycles of the 800 nm pulse are observed and compared with theory to elucidate the instantaneous and effective hole dynamics. Isolated attosecond pulses create massive superpositions of electronic states in Ar and nitrogen as well as vibrational superpositions among electronic states in nitrogen. An 800 nm pulse manipulates the superpositions, and specific subcycle interferences, level shifting, and quantum beats are imprinted onto the attosecond pulse as a function of time delay. Detailed outcomes are compared to theory for measurements of time-dynamic superpositions by attosecond transient absorption. Supported by DOE, NSF, ARO, AFOSR, and DARPA.

  3. Effective field theory for deformed atomic nuclei

    CERN Document Server

    Papenbrock, T

    2015-01-01

    We present an effective field theory (EFT) for a model-independent description of deformed atomic nuclei. In leading order this approach recovers the well-known results from the collective model by Bohr and Mottelson. When higher-order corrections are computed, the EFT accounts for finer details such as the variation of the moment of inertia with the band head and the small magnitudes of interband $E2$ transitions. For rotational bands with a finite spin of the band head, the EFT is equivalent to the theory of a charged particle on the sphere subject to a magnetic monopole field.

  4. Effective field theory for deformed atomic nuclei

    Science.gov (United States)

    Papenbrock, T.; Weidenmüller, H. A.

    2016-05-01

    We present an effective field theory (EFT) for a model-independent description of deformed atomic nuclei. In leading order this approach recovers the well-known results from the collective model by Bohr and Mottelson. When higher-order corrections are computed, the EFT accounts for finer details such as the variation of the moment of inertia with the band head and the small magnitudes of interband E2 transitions. For rotational bands with a finite spin of the band head, the EFT is equivalent to the theory of a charged particle on the sphere subject to a magnetic monopole field.

  5. A theoretical study of dopant atom detection and probe behavior in STEM

    Science.gov (United States)

    Mittal, Anudha

    Very detailed information about the atomic and electronic structure of materials can be obtained via atomic-scale resolution scanning transmission electron microscopy (STEM). These experiments reach the limits of current microscopes, which means that optimal experimental design is a key ingredient in success. The step following experiment, extraction of information from experimental data is also complex. Comprehension of experimental data depends on comparison with simulated data and on fundamental understanding of aspects of scattering behavior. The research projects discussed in this thesis are formulated within three large concepts. 1. Usage of simulation to suggest experimental technique for observation of a particular structural feature.. Two specific structural features are explored. One is the characterization of a substitutional dopant atom in a crystal. Annular dark field scanning transmission electron microscope (ADF-STEM) images allow detection of individual dopant atoms in a crystal based on contrast between intensities of doped and non-doped column in the image. The magnitude of the said contrast is heavily influenced by specimen and microscope parameters. Analysis of multislice-based simulations of ADF-STEM images of crystals doped with one substitutional dopant atom for a wide range of crystal thicknesses, types and locations of dopant atom inside the crystal, and crystals with different atoms revealed trends and non-intuitive behaviors in visibility of the dopant atom. The results provide practical guidelines for the optimal experimental setup regarding both the microscope and specimen conditions in order to characterize the presence and location of a dopant atom. Furthermore, the simulations help in recognizing the cases where detecting a single dopant atom via ADF-STEM imaging is not possible. The second is a more specific case of detecting intrinsic twist in MoS2 nanotubes. Objective molecular dynamics simulations coupled with a density

  6. Test of Nonlocality with an Atom-Field Entangled State

    Institute of Scientific and Technical Information of China (English)

    ZHENG Shi-Biao

    2002-01-01

    We propose a scheme for the test of nonlocality with atom-field entanglement. An atom is sent through a cavity filled with a coherent field with a small amplitude. The dispersive interaction leads to atom-field entanglement.Then the field is driven by a classical current. The Bell inequality can be tested by the joint measurement of the parity of the field and the atomic state.

  7. C12/C13-ratio determination in nanodiamonds by atom-probe tomography.

    Science.gov (United States)

    Lewis, Josiah B; Isheim, Dieter; Floss, Christine; Seidman, David N

    2015-12-01

    The astrophysical origins of ∼ 3 nm-diameter meteoritic nanodiamonds can be inferred from the ratio of C12/C13. It is essential to achieve high spatial and mass resolving power and minimize all sources of signal loss in order to obtain statistically significant measurements. We conducted atom-probe tomography on meteoritic nanodiamonds embedded between layers of Pt. We describe sample preparation, atom-probe tomography analysis, 3D reconstruction, and bias correction. We present new data from meteoritic nanodiamonds and terrestrial standards and discuss methods to correct isotopic measurements made with the atom-probe tomograph.

  8. On the energy of electric field in hydrogen atom

    OpenAIRE

    Kornyushin, Yuri

    2009-01-01

    It is shown that hydrogen atom is a unique object in physics having negative energy of electric field, which is present in the atom. This refers also to some hydrogen-type atoms: hydrogen anti-atom, atom composed of proton and antiproton, and positronium.

  9. Contribution of Electromagnetic Field to Atomic Spin

    Institute of Scientific and Technical Information of China (English)

    DU Tao; LIANG Wen-Feng; WU Xiao-Hua

    2011-01-01

    We examine the contribution of electromagnetic field to the atomic spin, by adopting two different, both gauge invariant definitions of the electromagnetic angular momentum: →JI≡ ∫ d3x∈0→γ× (→E × →B) and →JII ≡ ∫ d3x(∈0→E × A→⊥ + ∈0Ei→ γ× ▽A⊥i). Notably, at the classical level, J→II gives an exactly null result while →JI gives a finite value.This suggests that JII leads to a simpler and more reasonable picture of the atomic spin, therefore qualifies as a more appropriate definition of the electromagnetic angular momentum. Our observation gives important hint on the delicate issue of gluon contribution to the nucleon spin.

  10. Probing Local Ionic Dynamics in Functional Oxides: From Nanometer to Atomic Scale

    Science.gov (United States)

    Kalinin, Sergei

    2014-03-01

    Vacancy-mediated electrochemical reactions in oxides underpin multiple applications ranging from electroresistive memories, to chemical sensors to energy conversion systems such as fuel cells. Understanding the functionality in these systems requires probing reversible (oxygen reduction/evolution reaction) and irreversible (cathode degradation and activation, formation of conductive filaments) electrochemical processes. In this talk, I summarize recent advances in probing and controlling these transformations locally on nanometer level using scanning probe microscopy. The localized tip concentrates the electric field in the nanometer scale volume of material, inducing local transition. Measured simultaneously electromechanical response (piezoresponse) or current (conductive AFM) provides the information on the bias-induced changes in material. Here, I illustrate how these methods can be extended to study local electrochemical transformations, including vacancy dynamics in oxides such as titanates, LaxSr1-xCoO3, BiFeO3, and YxZr1-xO2. The formation of electromechanical hysteresis loops and their bias-, temperature- and environment dependences provide insight into local electrochemical mechanisms. In materials such as lanthanum-strontium cobaltite, mapping both reversible vacancy motion and vacancy ordering and static deformation is possible, and can be corroborated by post mortem STEM/EELS studies. In ceria, a broad gamut of electrochemical behaviors is observed as a function of temperature and humidity. The possible strategies for elucidation ionic motion at the electroactive interfaces in oxides using high-resolution electron microscopy and combined ex-situ and in-situ STEM-SPM studies are discussed. In the second part of the talk, probing electrochemical phenomena on in-situ grown surfaces with atomic resolution is illustrated. I present an approach based on the multivariate statistical analysis of the coordination spheres of individual atoms to reveal

  11. A Tuning Fork with a Short Fibre Probe Sensor for a Near-FieldScanning Optical Microscope

    Institute of Scientific and Technical Information of China (English)

    王沛; 鲁拥华; 章江英; 明海; 谢建平; 黄建文; 高宗圣; 蔡定平

    2002-01-01

    We report on a tapping-mode tuning fork with a short fibre probe sensor for a near-field scanning optical microscope. The method demonstrates how to fabricate the short fibre probe. This tapping-mode tuning fork with a short fibre probe can provide stable and high Q at the tapping frequency of the tuning fork, and can give high-quality near-field scanning optical microscope and atomic force microscope images of samples. We present the results of using the tapping-mode tuning fork with a short fibre probe sensor for a near-field scanning optical microscope performed on an eight-channel silica waveguide.

  12. Simulating compact quantum electrodynamics with ultracold atoms: probing confinement and nonperturbative effects.

    Science.gov (United States)

    Zohar, Erez; Cirac, J Ignacio; Reznik, Benni

    2012-09-21

    Recently, there has been much interest in simulating quantum field theory effects of matter and gauge fields. In a recent work, a method for simulating compact quantum electrodynamics (CQED) using Bose-Einstein condensates has been suggested. We suggest an alternative approach, which relies on single atoms in an optical lattice, carrying 2l + 1 internal levels, which converges rapidly to CQED as l increases. That enables the simulation of CQED in 2 + 1 dimensions in both the weak and the strong coupling regimes, hence, allowing us to probe confinement as well as other nonperturbative effects of the theory. We provide an explicit construction for the case l = 1 which is sufficient for simulating the effect of confinement between two external static charges.

  13. Laser-material interaction during atom probe tomography of oxides with embedded metal nanoparticles

    Science.gov (United States)

    Shinde, D.; Arnoldi, L.; Devaraj, A.; Vella, A.

    2016-10-01

    Oxide-supported metal nano-particles are of great interest in catalysis but also in the development of new large-spectrum-absorption materials. The design of such nano materials requires three-dimensional characterization with a high spatial resolution and elemental selectivity. The laser assisted Atom Probe Tomography (La-APT) presents both these capacities if an accurate understanding of laser-material interaction is developed. In this paper, we focus on the fundamental physics of field evaporation as a function of sample geometry, laser power, and DC electric field for Au nanoparticles embedded in MgO. By understanding the laser-material interaction through experiments and a theoretical model of heat diffusion inside the sample after the interaction with laser pulse, we point out the physical origin of the noise and determine the conditions to reduce it by more than one order of magnitude, improving the sensitivity of the La-APT for metal-dielectric composites.

  14. Magnetic probe array with high sensitivity for fluctuating field.

    Science.gov (United States)

    Kanamaru, Yuki; Gota, Hiroshi; Fujimoto, Kayoko; Ikeyama, Taeko; Asai, Tomohiko; Takahashi, Tsutomu; Nogi, Yasuyuki

    2007-03-01

    A magnetic probe array is constructed to measure precisely the spatial structure of a small fluctuating field included in a strong confinement field that varies with time. To exclude the effect of the confinement field, the magnetic probes consisting of figure-eight-wound coils are prepared. The spatial structure of the fluctuating field is obtained from a Fourier analysis of the probe signal. It is found that the probe array is more sensitive to the fluctuating field with a high mode number than that with a low mode number. An experimental demonstration of the present method is attempted using a field-reversed configuration plasma, where the fluctuating field with 0.1% of the confinement field is successfully detected.

  15. Probing into Magnetic Field and Initial Period of Neutron Star

    Institute of Scientific and Technical Information of China (English)

    BAI Hua; PENG Qiu-He

    2004-01-01

    Using the hybrid model and the neutrino jet rocket model, we calculate the magnetic fields and the initial periods of 72 pulsars. We probe into the possible connection among magnetic field, initial period, and initial quantum number.

  16. Atom Probe Insights into U-Pb Age Resetting in Baddeleyite

    Science.gov (United States)

    White, L. F.; Reinhard, D.; Moser, D.; Darling, J. R.; Bullen, D.; Prosa, T. J.; Olson, D.; Larson, D. J.; Clifton, P. H.; Lawrence, D.; Martin, I.

    2016-08-01

    Atom probe analysis of highly shocked baddeleyite suggests that igneous crystallisation ages can be isolated from 'partially reset' grains through careful segregation and rejection of planar features known to induce post-impact Pb-diffusion.

  17. Laser-assisted atom probe tomography investigation of magnetic FePt nanoclusters: First experiments

    Energy Technology Data Exchange (ETDEWEB)

    Folcke, E.; Larde, R. [Groupe de Physique des Materiaux, UMR CNRS 6634, Universite de Rouen, 76801 Saint Etienne du Rouvray (France); Le Breton, J.M., E-mail: jean-marie.lebreton@univ-rouen.fr [Groupe de Physique des Materiaux, UMR CNRS 6634, Universite de Rouen, 76801 Saint Etienne du Rouvray (France); Gruber, M.; Vurpillot, F. [Groupe de Physique des Materiaux, UMR CNRS 6634, Universite de Rouen, 76801 Saint Etienne du Rouvray (France); Shield, J.E.; Rui, X. [Department of Mechanical and Materials Engineering, Nebraska Center for Materials and Nanoscience, University of Nebraska, N104 WSEC, Lincoln, NE 68588 (United States); Patterson, M.M. [Department of Physics, University of Wisconsin-Stout, Menomonie, WI 54751 (United States)

    2012-03-15

    Highlights: Black-Right-Pointing-Pointer FePt nanoclusters dispersed in a Cr matrix were studied by atom probe tomography. Black-Right-Pointing-Pointer Simulated experiments were conducted to study the artefacts of the analysis. Black-Right-Pointing-Pointer In FePt nanoclusters, Fe and Pt are present in equiatomic proportions. Black-Right-Pointing-Pointer FePt nanoclusters are homogeneous, no core-shell structure is observed. - Abstract: FePt nanoclusters dispersed in a Cr matrix have been investigated by laser-assisted atom probe tomography. The results were analysed according to simulated evaporation experiments. Three-dimensional (3D) reconstructions reveal the presence of nanoclusters roughly spherical in shape, with a size in good agreement with previous transmission electron microscopy observations. Some clusters appear to be broken up after the evaporation process due to the fact that the Cr matrix has a lower evaporation field than Fe and Pt. It is thus shown that the observed FePt nanoclusters are chemically homogeneous. They contain Fe and Pt in equiatomic proportions, with no core-shell structure observed.

  18. Solid-state electrochemistry on the nanometer and atomic scales: the scanning probe microscopy approach

    Science.gov (United States)

    Strelcov, Evgheni; Yang, Sang Mo; Jesse, Stephen; Balke, Nina; Vasudevan, Rama K.; Kalinin, Sergei V.

    2016-07-01

    Energy technologies of the 21st century require an understanding and precise control over ion transport and electrochemistry at all length scales - from single atoms to macroscopic devices. This short review provides a summary of recent studies dedicated to methods of advanced scanning probe microscopy for probing electrochemical transformations in solids at the meso-, nano- and atomic scales. The discussion presents the advantages and limitations of several techniques and a wealth of examples highlighting peculiarities of nanoscale electrochemistry.

  19. Probe spectrum of a four-level atom in a double-band photonic crystal

    Institute of Scientific and Technical Information of China (English)

    Wen Qing-Bo; Wang Jian; Zhang Han-Zhuang

    2004-01-01

    In this paper, the probe absorption spectrum of an atom in a double-band photonic crystal have been studied. In the modes, we assume that one of the two atomic transitions in a A-type atomic system is interacting with free vacuum modes, and another transition is interacting with free vacuum modes, isotropic photonic band gap (PBG) modes and anisotropic PBG modes, separately. The effects of the fine structure of the atomic lower levels on the probe absorption spectrum are investigated in detail in the three cases. The most interesting thing is that the two (four) transparencies at one (two) probe absorption peak(s), caused by the fine structure of the lower levels of an atom, are predicted in the case of isotropic PBG modes.

  20. Probing the conformal Calabrese-Cardy scaling with cold atoms

    CERN Document Server

    Unmuth-Yockey, J; Preiss, P M; Yang, Li-Ping; Tsai, S -W; Meurice, Y

    2016-01-01

    We demonstrate that current experiments using cold bosonic atoms trapped in one-dimensional optical lattices and designed to measure the second-order Renyi entanglement entropy S_2, can be used to verify detailed predictions of conformal field theory (CFT) and estimate the central charge c. We discuss the adiabatic preparation of the ground state at half-filling where we expect a CFT with c=1. This can be accomplished with a very small hoping parameter J, in contrast to existing studies with density one where a much larger J is needed. We provide two complementary methods to estimate and subtract the classical entropy generated by the experimental preparation and imaging processes. We compare numerical calculations for the classical O(2) model with a chemical potential on a 1+1 dimensional lattice, and the quantum Bose-Hubbard Hamiltonian implemented in the experiments. S_2 is very similar for the two models and follows closely the Calabrese-Cardy scaling, (c/8)\\ln(N_s), for N_s sites with open boundary condi...

  1. The effect orientation of features in reconstructed atom probe data on the resolution and measured composition of T1 plates in an A2198 aluminium alloy.

    Science.gov (United States)

    Mullin, Maria A; Araullo-Peters, Vicente J; Gault, Baptiste; Cairney, Julie M

    2015-12-01

    Artefacts in atom probe tomography can impact the compositional analysis of microstructure in atom probe studies. To determine the integrity of information obtained, it is essential to understand how the positioning of features influences compositional analysis. By investigating the influence of feature orientation within atom probe data on measured composition in microstructural features within an AA2198 Al alloy, this study shows differences in the composition of T1 (Al2CuLi) plates that indicates imperfections in atom probe reconstructions. The data fits a model of an exponentially-modified Gaussian that scales with the difference in evaporation field between solutes and matrix. This information provides a guide for obtaining the most accurate information possible.

  2. Preparation of nanowire specimens for laser-assisted atom probe tomography.

    Science.gov (United States)

    Blumtritt, H; Isheim, D; Senz, S; Seidman, D N; Moutanabbir, O

    2014-10-31

    The availability of reliable and well-engineered commercial instruments and data analysis software has led to development in recent years of robust and ergonomic atom-probe tomographs. Indeed, atom-probe tomography (APT) is now being applied to a broader range of materials classes that involve highly important scientific and technological problems in materials science and engineering. Dual-beam focused-ion beam microscopy and its application to the fabrication of APT microtip specimens have dramatically improved the ability to probe a variety of systems. However, the sample preparation is still challenging especially for emerging nanomaterials such as epitaxial nanowires which typically grow vertically on a substrate through metal-catalyzed vapor phase epitaxy. The size, morphology, density, and sensitivity to radiation damage are the most influential parameters in the preparation of nanowire specimens for APT. In this paper, we describe a step-by-step process methodology to allow a precisely controlled, damage-free transfer of individual, short silicon nanowires onto atom probe microposts. Starting with a dense array of tiny nanowires and using focused ion beam, we employed a sequence of protective layers and markers to identify the nanowire to be transferred and probed while protecting it against Ga ions during lift-off processing and tip sharpening. Based on this approach, high-quality three-dimensional atom-by-atom maps of single aluminum-catalyzed silicon nanowires are obtained using a highly focused ultraviolet laser-assisted local electrode atom probe tomograph.

  3. Laser-Assisted Atom Probe Tomography of Deformed Minerals: A Zircon Case Study.

    Science.gov (United States)

    La Fontaine, Alexandre; Piazolo, Sandra; Trimby, Patrick; Yang, Limei; Cairney, Julie M

    2017-01-30

    The application of atom probe tomography to the study of minerals is a rapidly growing area. Picosecond-pulsed, ultraviolet laser (UV-355 nm) assisted atom probe tomography has been used to analyze trace element mobility within dislocations and low-angle boundaries in plastically deformed specimens of the nonconductive mineral zircon (ZrSiO4), a key material to date the earth's geological events. Here we discuss important experimental aspects inherent in the atom probe tomography investigation of this important mineral, providing insights into the challenges in atom probe tomography characterization of minerals as a whole. We studied the influence of atom probe tomography analysis parameters on features of the mass spectra, such as the thermal tail, as well as the overall data quality. Three zircon samples with different uranium and lead content were analyzed, and particular attention was paid to ion identification in the mass spectra and detection limits of the key trace elements, lead and uranium. We also discuss the correlative use of electron backscattered diffraction in a scanning electron microscope to map the deformation in the zircon grains, and the combined use of transmission Kikuchi diffraction and focused ion beam sample preparation to assist preparation of the final atom probe tip.

  4. Scanned Probe Oxidation onp-GaAs(100 Surface with an Atomic Force Microscopy

    Directory of Open Access Journals (Sweden)

    Juang Jenh-Yih

    2008-01-01

    Full Text Available AbstractLocally anodic oxidation has been performed to fabricate the nanoscale oxide structures onp-GaAs(100 surface, by using an atomic force microscopy (AFM with the conventional and carbon nanotube (CNT-attached probes. The results can be utilized to fabricate the oxide nanodots under ambient conditions in noncontact mode. To investigate the conversion of GaAs to oxides, micro-Auger analysis was employed to analyze the chemical compositions. The growth kinetics and the associated mechanism of the oxide nanodots were studied under DC voltages. With the CNT-attached probe the initial growth rate of oxide nanodots is in the order of ~300 nm/s, which is ~15 times larger than that obtained by using the conventional one. The oxide nanodots cease to grow practically as the electric field strength is reduced to the threshold value of ~2 × 107 V cm−1. In addition, results indicate that the height of oxide nanodots is significantly enhanced with an AC voltage for both types of probes. The influence of the AC voltages on controlling the dynamics of the AFM-induced nanooxidation is discussed.

  5. Probing angular momentum coherence in a twin-atom interferometer

    CERN Document Server

    de Carvalho, Carlos R; Impens, François; Robert, J; Medina, Aline; Zappa, F; Faria, N V de Castro

    2014-01-01

    We propose to use a double longitudinal Stern-Gerlach atom interferometer in order to investigate quantitatively the angular momentum coherence of molecular fragments. Assuming that the dissociated molecule has a null total angular momentum, we investigate the propagation of the corresponding atomic fragments in the apparatus. We show that the envisioned interferometer enables one to distinguish unambiguously a spin-coherent from a spin-incoherent dissociation, as well as to estimate the purity of the angular momentum density matrix associated with the fragments. This setup, which may be seen as an atomic analogue of a twin-photon interferometer, can be used to investigate the suitability of molecule dissociation processes -- such as the metastable hydrogen atoms H($2^2 S$)-H($2^2 S$) dissociation - for coherent twin-atom optics.

  6. Probing Structure and Composition of Nickel/Titanium Carbide Hybrid Interfaces at the Atomic Scale (Preprint)

    Science.gov (United States)

    2010-01-01

    The transition in structure and composition across the titanium carbide /nickel hybrid interface has been determined at near atomic resolution by...coupling high-resolution transmission electron microscopy with three-dimensional atom probe tomography. The titanium carbide phase adopts a rocksalt-type

  7. Near-field Electrodynamics of Atomically Doped Carbon Nanotubes

    OpenAIRE

    Bondarev, Igor V.; Lambin, Philippe

    2005-01-01

    We develop a quantum theory of near-field electrodynamical properties of carbon nanotubes and investigate spontaneous decay dynamics of excited states and van der Waals attraction of the ground state of an atomic system close to a single-wall nanotube surface. Atomic spontaneous decay exhibits vacuum-field Rabi oscillations -- a principal signature of strong atom-vacuum-field coupling. The strongly coupled atomic state is nothing but a 'quasi-1D cavity polariton'. Its stability is mainly dete...

  8. Quantitative analysis of doped/undoped ZnO nanomaterials using laser assisted atom probe tomography: Influence of the analysis parameters

    Energy Technology Data Exchange (ETDEWEB)

    Amirifar, Nooshin; Lardé, Rodrigue, E-mail: rodrigue.larde@univ-rouen.fr; Talbot, Etienne; Pareige, Philippe; Rigutti, Lorenzo; Mancini, Lorenzo; Houard, Jonathan; Castro, Celia [Groupe de Physique des Matériaux, UMR CNRS 6634, Université et INSA de Rouen, Avenue de l' Université, BP 12, 76801 Saint Etienne du Rouvray (France); Sallet, Vincent; Zehani, Emir; Hassani, Said; Sartel, Corine [Groupe d' étude de la Matière Condensée (GEMAC), CNRS Université de Versailles St Quentin, 45 Avenue des Etats-Unis, 78035 Versailles Cedex (France); Ziani, Ahmed; Portier, Xavier [Centre de Recherche sur les Ions, les Matériaux et la Photonique (CIMAP), UMR 6252 CEA-CNRS-ENSICAEN, Université de Caen, 14050 Caen (France)

    2015-12-07

    In the last decade, atom probe tomography has become a powerful tool to investigate semiconductor and insulator nanomaterials in microelectronics, spintronics, and optoelectronics. In this paper, we report an investigation of zinc oxide nanostructures using atom probe tomography. We observed that the chemical composition of zinc oxide is strongly dependent on the analysis parameters used for atom probe experiments. It was observed that at high laser pulse energies, the electric field at the specimen surface is strongly dependent on the crystallographic directions. This dependence leads to an inhomogeneous field evaporation of the surface atoms, resulting in unreliable measurements. We show that the laser pulse energy has to be well tuned to obtain reliable quantitative chemical composition measurements of undoped and doped ZnO nanomaterials.

  9. Understanding proton-conducting perovskite interfaces using atom probe tomography

    Science.gov (United States)

    Clark, Daniel R.

    Proton-conducting ceramics are under intense scientific investigation for a number of exciting applications, including fuel cells, electrolyzers, hydrogen separation membranes, membrane reactors, and sensors. However, commercial application requires deeper understanding and improvement of proton conductivity in these materials. It is well-known that proton conductivity in these materials is often limited by highly resistive grain boundaries (GBs). While these conductivity-limiting GBs are still not well understood, it is hypothesized that their blocking nature stems from the formation of a positive (proton-repelling) space-charge zone. Furthermore, it has been observed that the strength of the blocking behavior can change dramatically depending on the fabrication process used to make the ceramic. This thesis applies laser-assisted atom probe tomography (LAAPT) to provide new insights into the GB chemistry and resulting space-charge behavior of BaZr0.9Y0.1O 3--delta (BZY10), a prototypical proton-conducting ceramic. LAAPT is an exciting characterization technique that allows for three-dimensional nm-scale spatial resolution and very high chemical resolution (up to parts-per-million). While it is challenging to quantitatively apply LAAPT to complex, multi-cation oxide materials, this thesis successfully develops a method to accurately quantify the stoichiometry of BZY10 and maintain minimal quantitative cationic deviation at a laser energies of approximately 10--20 pJ. With the analysis technique specifically optimized for BZY10, GB chemistry is then examined for BZY10 samples prepared using four differing processing methods: (1) spark plasma sintering (SPS), (2) conventional sintering using powder prepared by solid-state reaction followed by high-temperature annealing (HT), (3) conventional sintering using powder prepared by solid-state reaction with NiO used as a sintering aid (SSR-Ni), and (4) solid-state reactive sintering directly from BaCO3, ZrO2, and Y2O3

  10. Magnetic field concentrator for probing optical magnetic metamaterials.

    Science.gov (United States)

    Antosiewicz, Tomasz J; Wróbel, Piotr; Szoplik, Tomasz

    2010-12-01

    Development of all dielectric and plasmonic metamaterials with a tunable optical frequency magnetic response creates a need for new inspection techniques. We propose a method of measuring magnetic responses of such metamaterials within a wide range of optical frequencies with a single probe. A tapered fiber probe with a radially corrugated metal coating concentrates azimuthally polarized light in the near-field into a subwavelength spot the longitudinal magnetic field component which is much stronger than the perpendicular electric one. The active probe may be used in a future scanning near-field magnetic microscope for studies of magnetic responses of subwavelength elementary cells of metamaterials.

  11. Evaporation mechanisms of MgO in laser assisted atom probe tomography

    KAUST Repository

    Mazumder, Baishakhi

    2011-05-01

    In this paper the field evaporation properties of bulk MgO and sandwiched MgO layers in Fe are compared using laser assisted Atom Probe Tomography. The comparison of flight time spectra gives an estimate of the evaporation times as a function of the wavelength and the laser energy. It is shown that the evaporation takes place in two steps on two different time scales in MgO. It is also shown that as long as the MgO layer is buried in Fe, the evaporation is dominated by the photon absorption in Fe layer at the tip apex. Eventually the evaporation process of MgO is discussed based on the difference between the bulk materials and the multilayer samples. © 2010 Elsevier B.V.

  12. Restoring the lattice of Si-based atom probe reconstructions for enhanced information on dopant positioning.

    Science.gov (United States)

    Breen, Andrew J; Moody, Michael P; Ceguerra, Anna V; Gault, Baptiste; Araullo-Peters, Vicente J; Ringer, Simon P

    2015-12-01

    The following manuscript presents a novel approach for creating lattice based models of Sb-doped Si directly from atom probe reconstructions for the purposes of improving information on dopant positioning and directly informing quantum mechanics based materials modeling approaches. Sophisticated crystallographic analysis techniques are used to detect latent crystal structure within the atom probe reconstructions with unprecedented accuracy. A distortion correction algorithm is then developed to precisely calibrate the detected crystal structure to the theoretically known diamond cubic lattice. The reconstructed atoms are then positioned on their most likely lattice positions. Simulations are then used to determine the accuracy of such an approach and show that improvements to short-range order measurements are possible for noise levels and detector efficiencies comparable with experimentally collected atom probe data.

  13. Atom Probe Analysis of Ex Situ Gas-Charged Stable Hydrides.

    Science.gov (United States)

    Haley, Daniel; Bagot, Paul A J; Moody, Michael P

    2017-01-30

    In this work, we report on the atom probe tomography analysis of two metallic hydrides formed by pressurized charging using an ex situ hydrogen charging cell, in the pressure range of 200-500 kPa (2-5 bar). Specifically we report on the deuterium charging of Pd/Rh and V systems. Using this ex situ system, we demonstrate the successful loading and subsequent atom probe analysis of deuterium within a Pd/Rh alloy, and demonstrate that deuterium is likely present within the oxide-metal interface of a native oxide formed on vanadium. Through these experiments, we demonstrate the feasibility of ex situ hydrogen analysis for hydrides via atom probe tomography, and thus a practical route to three-dimensional imaging of hydrogen in hydrides at the atomic scale.

  14. Atom probe tomography of Ni-base superalloys Allvac 718Plus and Alloy 718.

    Science.gov (United States)

    Viskari, L; Stiller, K

    2011-05-01

    Atom probe tomography (APT) allows near atomic scale compositional- and morphological studies of, e.g. matrix, precipitates and interfaces in a wide range of materials. In this work two Ni-base superalloys with similar compositions, Alloy 718 and its derivative Allvac 718Plus, are subject for investigation with special emphasis on the latter alloy. The structural and chemical nuances of these alloys are important for their properties. Of special interest are grain boundaries as their structure and chemistry are important for the materials' ability to resist rapid environmentally induced crack propagation. APT has proved to be suitable for analyses of these types of alloys using voltage pulsed APT. However, for investigations of specimens containing grain boundaries and other interfaces the risk for early specimen fracture is high. Analyses using laser pulsing impose lower electrical field on the specimen thereby significantly increasing the success rate of investigations. Here, the effect of laser pulsing was studied and the derived appropriate acquisition parameters were then applied for microstructural studies, from which initial results are shown. Furthermore, the influence of the higher evaporation field experienced by the hardening γ' Ni(3)(Al,Nb) precipitates on the obtained results is discussed.

  15. Electric field sensing near the surface microstructure of an atom chip using cold Rydberg atoms

    CERN Document Server

    Carter, J D; Martin, J D D

    2012-01-01

    The electric fields near the heterogeneous metal/dielectric surface of an atom chip were measured using cold atoms. The atomic sensitivity to electric fields was enhanced by exciting the atoms to Rydberg states that are 10^8 times more polarizable than the ground state. We attribute the measured fields to charging of the insulators between the atom chip wires. Surprisingly, it is observed that these fields may be dramatically lowered with appropriate voltage biasing, suggesting configurations for the future development of hybrid quantum systems.

  16. Quantitative binomial distribution analyses of nanoscale like-solute atom clustering and segregation in atom probe tomography data.

    Science.gov (United States)

    Moody, Michael P; Stephenson, Leigh T; Ceguerra, Anna V; Ringer, Simon P

    2008-07-01

    The applicability of the binomial frequency distribution is outlined for the analysis of the evolution nanoscale atomic clustering of dilute solute in an alloy subject to thermal ageing in 3D atom probe data. The conventional chi(2) statistics and significance testing are demonstrated to be inappropriate for comparison of quantity of solute segregation present in two or more different sized system. Pearson coefficient, mu, is shown to normalize chi(2) with respect to sample size over an order of magnitude. A simple computer simulation is implemented to investigate the binomial analysis and infer meaning in the measured value of mu over a series of systems at different solute concentrations and degree of clustering. The simulations replicate the form of experimental data and demonstrate the effect of detector efficiency to significantly underestimate the measured segregation. The binomial analysis is applied to experimental atom probe data sets and complementary simulations are used to interpret the results.

  17. State Feedback Control for Adjusting the Dynamic Behavior of a Piezoactuated Bimorph Atomic Force Microscopy Probe

    CERN Document Server

    Orun, Bilal; Basdogan, Cagatay; Guvenc, Levent

    2012-01-01

    We adjust the transient dynamics of a piezo-actuated bimorph Atomic Force Microscopy (AFM) probe using a state feedback controller. This approach enables us to adjust the quality factor and the resonance frequency of the probe simultaneously. First, we first investigate the effect of feedback gains on dynamic response of the probe and then show that the time constant of the probe can be reduced by reducing its quality factor and/or increasing its resonance frequency to reduce the scan error in tapping mode AFM.

  18. Generating and probing entangled states for optical atomic clocks

    Science.gov (United States)

    Braverman, Boris; Kawasaki, Akio; Vuletic, Vladan

    2016-05-01

    The precision of quantum measurements is inherently limited by projection noise caused by the measurement process itself. Spin squeezing and more complex forms of entanglement have been proposed as ways of surpassing this limitation. In our system, a high-finesse asymmetric micromirror-based optical cavity can mediate the atom-atom interaction necessary for generating entanglement in an 171 Yb optical lattice clock. I will discuss approaches for creating, characterizing, and optimally utilizing these nonclassical states for precision measurement, as well as recent progress toward their realization. This research is supported by DARPA QuASAR, NSF, and NSERC.

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

    Institute of Scientific and Technical Information of China (English)

    刘堂昆; 张康隆; 陶宇; 单传家; 刘继兵

    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.

  20. IMPROVED FABRICATION METHOD FOR CARBON NANOTUBE PROBE OF ATOMIC FORCE MICROSCOPY(AFM)

    Institute of Scientific and Technical Information of China (English)

    XU Zongwei; DONG Shen; GUO Liqiu; ZHAO Qingliang

    2006-01-01

    An improved arc discharge method is developed to fabricate carbon nanotube probe of atomic force microscopy (AFM) here. First, silicon probe and carbon nanotube are manipulated under an optical microscope by two high precision microtranslators. When silicon probe and carbon nanotube are very close, several tens voltage is applied between them. And carbon nanotube is divided and attached to the end of silicon probe, which mainly due to the arc welding function.Comparing with the arc discharge method before, the new method here needs no coat silicon probe with metal film in advance, which can greatly reduce the fabrication's difficulty. The fabricated carbon nanotube probe shows good property of higher aspect ratio and can more accurately reflect the true topography of silicon grating than silicon probe. Under the same image drive force, carbon nanotube probe had less indentation depth on soft triblock copolymer sample than silicon probe. This showed that carbon nanotube probe has lower spring constant and less damage to the scan sample than silicon probe.

  1. Nonlocal response of metallic nanospheres probed by light, electrons, and atoms.

    Science.gov (United States)

    Christensen, Thomas; Yan, Wei; Raza, Søren; Jauho, Antti-Pekka; Mortensen, N Asger; Wubs, Martijn

    2014-02-25

    Inspired by recent measurements on individual metallic nanospheres that cannot be explained with traditional classical electrodynamics, we theoretically investigate the effects of nonlocal response by metallic nanospheres in three distinct settings: atomic spontaneous emission, electron energy loss spectroscopy, and light scattering. These constitute two near-field and one far-field measurements, with zero-, one-, and two-dimensional excitation sources, respectively. We search for the clearest signatures of hydrodynamic pressure waves in nanospheres. We employ a linearized hydrodynamic model, and Mie-Lorenz theory is applied for each case. Nonlocal response shows its mark in all three configurations, but for the two near-field measurements, we predict especially pronounced nonlocal effects that are not exhibited in far-field measurements. Associated with every multipole order is not only a single blueshifted surface plasmon but also an infinite series of bulk plasmons that have no counterpart in a local-response approximation. We show that these increasingly blueshifted multipole plasmons become spectrally more prominent at shorter probe-to-surface separations and for decreasing nanosphere radii. For selected metals, we predict hydrodynamic multipolar plasmons to be measurable on single nanospheres.

  2. Hidden Markov Model of atomic quantum jump dynamics in an optically probed cavity

    DEFF Research Database (Denmark)

    Gammelmark, S.; Molmer, K.; Alt, W.

    2014-01-01

    We analyze the quantum jumps of an atom interacting with a cavity field. The strong atom- field interaction makes the cavity transmission depend on the time dependent atomic state, and we present a Hidden Markov Model description of the atomic state dynamics which is conditioned in a Bayesian......, the atomic state is determined in a Bayesian manner from the measurement data, and we present an iterative protocol, which determines both the atomic state and the model parameters. As a new element in the treatment of observed quantum systems, we employ a Bayesian approach that conditions the atomic state...... manner on the detected signal. We suggest that small variations in the observed signal may be due to spatial motion of the atom within the cavity, and we represent the atomic system by a number of hidden states to account for both the small variations and the internal state jump dynamics. In our theory...

  3. Atomic resolution in noncontact AFM by probing cantilever frequency shifts

    Institute of Scientific and Technical Information of China (English)

    Hong Yong Xie

    2007-01-01

    Rutile TiO2(001) quantum dots (or nano-marks) in different shapes were used to imitate uncleaved material surfaces or materials with rough surfaces. By numerical integration of the equation of motion of cantilever for silicon tip scanning along the [110] direction over the rutile TiO2 (001) quantum dots in ultra high vacuum (UHV), scanning routes were explored to achieve atomic resolution from frequency shift image. The tip-surface interaction forces were calculated from Lennard-Jones (12-6) potential by the Hamaker summation method. The calculated results showed that atomic resolution could be achieved by frequency shift image for TiO2 (001) surfaces of rhombohedral quantum dot scanning in a vertical route, and spherical cap quantum dot scanning in a superposition route.

  4. Preparation and Analysis of Atom Probe Tips by Xenon Focused Ion Beam Milling.

    Science.gov (United States)

    Estivill, Robert; Audoit, Guillaume; Barnes, Jean-Paul; Grenier, Adeline; Blavette, Didier

    2016-06-01

    The damage and ion distribution induced in Si by an inductively coupled plasma Xe focused ion beam was investigated by atom probe tomography. By using predefined patterns it was possible to prepare the atom probe tips with a sub 50 nm end radius in the ion beam microscope. The atom probe reconstruction shows good agreement with simulated implantation profiles and interplanar distances extracted from spatial distribution maps. The elemental profiles of O and C indicate co-implantation during the milling process. The presence of small disc-shaped Xe clusters are also found in the three-dimensional reconstruction. These are attributed to the presence of Xe nanocrystals or bubbles that open during the evaporation process. The expected accumulated dose points to a loss of >95% of the Xe during analysis, which escapes undetected.

  5. Atom probe tomography study of GaMnN thin films

    Energy Technology Data Exchange (ETDEWEB)

    Nicholas, Robert; Kane, Matthew [School of Electrical and Computer Engineering, University of Oklahoma, 110 W Boyd St Rm 150, Norman, OK 73019 (United States); Diercks, David [Center for Advanced Research and Technology, University of North Texas, Denton, TX 76203 (United States)

    2012-03-15

    Determining the nanoscale atomic distribution of transition metals is essential for understanding the magnetic behavior of III-nitride semiconductors. Atom probe tomography is a characterization technique that can provide direct physical detection of the location of atoms and thus is ideal for investigating nanoscale atomic ordering in these materials. This work presents a study of GaMnN thin films grown bymetalorganic chemical vapor deposition that are characterized utilizing the state of the art local electrode atom probe (LEAP trademark) to determine the atomic ordering of Mn in an effort to help understand the nanoclustering behaviour which leads to observed room-temperature ferromagnetic behaviour in GaMnN. The distribution of Mn on the atomic scale was found to be random in nature in the bulk of the thin film where the analysis was performed with no evidence for the predisposition of Mn to form dimers, trimers or clusters. Other sources of clustering must lead to the room-temperature ferromagnetic behaviour that has been observed in these samples, such as surface segregation of Mn during the growth process. This work proves consistent with prior magnetic analysis in that most atoms in the crystal are isolated Mn atoms which result in a paramagnetic signal. This work is a first step towards the ultimate goal of understanding the structure-property-growth condition relationships for the tailoring of specific MOCVD processes in nitride semiconductors. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Noncontact atomic force microscopy in liquid environment with quartz tuning fork and carbon nanotube probe

    DEFF Research Database (Denmark)

    Kageshima, M.; Jensenius, Henriette; Dienwiebel, M.

    2002-01-01

    A force sensor for noncontact atomic force microscopy in liquid environment was developed by combining a multiwalled carbon nanotube (MWNT) probe with a quartz tuning fork. Solvation shells of octamethylcyclotetrasiloxane surface were detected both in the frequency shift and dissipation. Due...... to the high aspect ratio of the CNT probe, the long-range background force was barely detectable in the solvation region. (C) 2002 Elsevier Science B.V. All rights reserved....

  7. Tailored probes for atomic force microscopy fabricated by two-photon polymerization

    Science.gov (United States)

    Göring, Gerald; Dietrich, Philipp-Immanuel; Blaicher, Matthias; Sharma, Swati; Korvink, Jan G.; Schimmel, Thomas; Koos, Christian; Hölscher, Hendrik

    2016-08-01

    3D direct laser writing based on two-photon polymerization is considered as a tool to fabricate tailored probes for atomic force microscopy. Tips with radii of 25 nm and arbitrary shape are attached to conventionally shaped micro-machined cantilevers. Long-term scanning measurements reveal low wear rates and demonstrate the reliability of such tips. Furthermore, we show that the resonance spectrum of the probe can be tuned for multi-frequency applications by adding rebar structures to the cantilever.

  8. High Field Seeking State Atom Laser and Properties of Flux

    Institute of Scientific and Technical Information of China (English)

    XIA Lin; XIONG Wei; YANG Fan; YI Lin; ZHOU Xiao-Ji; CHEN Xu-Zong

    2008-01-01

    We present an experimental study on the continuous atom laser. The experiments show that a high field seeking state atom laser with stable flux can be formed by increasing the strength of outcoupling before large density fluctuations appear. It is easy to obtain a long length or high speed output with this kind of atom laser.

  9. A First/Third-Order Probe Correction Technique for Spherical Near-Field Antenna Measurements Using Three Probe Orientations

    DEFF Research Database (Denmark)

    Laitinen, Tommi; Breinbjerg, Olav

    2008-01-01

    A probe correction technique is described for spherical near-field antenna measurements based on sampling the near field for three probe orientations in each measurement direction. The technique applies to odd-order probes whose radiated field contains (significant) power only in the first (µ=±1)...

  10. Atoms in static fields Chaos or Diffraction?

    CERN Document Server

    Dando, P A

    1998-01-01

    A brief review of the manifestations of classical chaos observed in atomic systems is presented. Particular attention is paid to the analysis of atomic spectra by periodic orbit-type theories. For diamagnetic non-hydrogenic Rydberg atoms, the dynamical explanation for observed spectral features has been disputed. By building on our previous work on the photoabsorption spectrum, we show how, by the addition of diffractive terms, the spectral fluctuations in the energy level spectrum of general Rydberg atoms can be obtained with remarkable precision from the Gutzwiller trace formula. This provides further evidence that non-hydrogenic systems are most naturally described in terms of diffraction rather than classical chaos.

  11. Atomic-scale investigations of grain boundary segregation in astrology with a three dimensional atom-probe

    Energy Technology Data Exchange (ETDEWEB)

    Blavette, D. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique]|[Institut Universitaire de France (France); Letellier, L. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique; Duval, P. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique; Guttmann, M. [Rouen Univ., 76 - Mont-Saint-Aignan (France). Lab. de Microscopie Electronique]|[Institut de Recherches de la Siderurgie Francaise (IRSID), 57 - Maizieres-les-Metz (France)

    1996-08-01

    Both conventional and 3D atom-probes were applied to the investigation of grain-boundary (GB) segregation phenomena in two-phase nickel base superalloys Astroloy. 3D images as provided by the tomographic atom-probe reveal the presence of a strong segregation of both boron and molybdenum at grain-boundaries. Slight carbon enrichment is also detected. Considerable chromium segregation is exhibited at {gamma}`-{gamma}` grain-boundaries. All these segregants are distributed in a continuous manner along the boundary over a width close to 0.5 nm. Experiments show that segregation occurs during cooling and more probably between 1000 C and 800 C. Boron and molybdenum GB enrichments are interpreted as due to an equilibrium type-segregation while chromium segregation is thought to be induced by {gamma}` precipitation at GB`s and stabilised by the presence of boron. No segregation of zirconium is detected. (orig.)

  12. Single molecule mapping of the optical field distribution of probes for near-field microscopy

    NARCIS (Netherlands)

    Veerman, J.A.; Garcia-Parajo, M.F.; Kuipers, L.; Hulst, van N.F.

    1999-01-01

    The most difficult task in near-field scanning optical microscopy (NSOM) is to make a high quality subwavelength aperture probe, Recently we have developed high definition NSOM probes by focused ion beam (FIB) milling. These probes have a higher brightness, better polarization characteristics, bette

  13. A new systematic framework for crystallographic analysis of atom probe data

    Energy Technology Data Exchange (ETDEWEB)

    Araullo-Peters, Vicente J., E-mail: vicente.araullopeters@gmail.com [Australian Centre for Microscopy and Microanalysis, University of Sydney (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney (Australia); Breen, Andrew; Ceguerra, Anna V. [Australian Centre for Microscopy and Microanalysis, University of Sydney (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney (Australia); Gault, Baptiste [Department of Materials, University of Oxford, Parks Road, Oxford (United Kingdom); Ringer, Simon P.; Cairney, Julie M. [Australian Centre for Microscopy and Microanalysis, University of Sydney (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, University of Sydney (Australia)

    2015-07-15

    In this article, after a brief introduction to the principles behind atom probe crystallography, we introduce methods for unambiguously determining the presence of crystal planes within atom probe datasets, as well as their characteristics: location; orientation and interplanar spacing. These methods, which we refer to as plane orientation extraction (POE) and local crystallography mapping (LCM) make use of real-space data and allow for systematic analyses. We present here application of POE and LCM to datasets of pure Al, industrial aluminium alloys and doped-silicon. Data was collected both in DC voltage mode and laser-assisted mode (in the latter of which extracting crystallographic information is known to be more difficult due to distortions). The nature of the atomic planes in both datasets was extracted and analysed. - Highlights: • A new analysis method was designed that determines if reconstructed planes are present in atom probe data. • The location, orientation, and planar spacing of these planes are obtained. • This method was applied to simulated, aluminium alloy and silicon data where the extent of planes was shown to vary considerably. • This method can be used to examine atom probe reconstruction quality.

  14. Atomic parity violation as a probe of new physics

    Science.gov (United States)

    Marciano, William J.; Rosner, Jonathan L.

    1990-12-01

    Effects of physics beyond the standard model on electroweak observables ares studied using the Peskin-Takeuchi isospin-conserving, S, and -breaking, T, parametrization of ``new'' quantum loop corrections. Experimental constraints on S and T are presented. Atomic parity-violating experiments are shown to be particularly sensitive to S with existing data giving S=-2.7+/-2.0+/-1.1. That constraint has important implications for generic technicolor models which predict S~=0.1NTND (NT is the number of technicolors, ND is the number of technidoublets).

  15. Theory of Near-Field Scanning with a Probe Array

    Science.gov (United States)

    2014-01-01

    performing near-field measurement using an array of probes for antenna and bistatic radar cross section (RCS) applications. 15. SUBJECT TERMS...electromagnetic near-field measurement, antenna measurement, bistatic RCS measurement 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT... SAR 18. NUMBER OF PAGES 84 19a. NAME OF RESPONSIBLE PERSON (Monitor) a. REPORT Unclassified b. ABSTRACT Unclassified c. THIS PAGE

  16. Preparation of Entangled Atomic States Through Resonant Atom-Field Interaction

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    A scheme is proposed for the generation of two-atom maximally entangled states and multi-atom maximally entangled states of W class. The scheme is based on the simultaneous resonant interaction of atoms with a single-mode cavity field. It does not require accurate adjustment of the interaction time. The time needed to complete the generation does not increase with the number of the atom.

  17. Probing Field Emission from Boron Carbide Nanowires

    Institute of Scientific and Technical Information of China (English)

    TIAN Ji-Fa; GAO Hong-Jun; BAO Li-Hong; WANG Xing-Jun; HUI Chao; LIU Fei; LI Chen; SHEN Cheng-Min; WANG Zong-Li; GU Chang-Zhi

    2008-01-01

    High density boron carbide nanowires are grown by an improved carbon thermal reduction technique. Transmission electron microscopy and electron energy lose spectroscopy of the sample show that the synthesized nanowires are B4 C with good crystallization. The field emission measurement for an individual boron nanowire is performed by using a Pt tip installed in the focused ion beam system. A field emission current with enhancement factor of 106 is observed and the evolution process during emission is also carefully studied. Furthermore, a two-step field emission with stable emission current density is found from the high-density nanowire film. Our results together suggest that boron carbide nanowires are promising candidates for electron emission nanodevices.

  18. Probing Andreev bound states in one-atom superconducting contacts

    Energy Technology Data Exchange (ETDEWEB)

    Pothier, Hugues; Janvier, Camille; Tosi, Leandro; Girit, Caglar; Goffman, Marcelo; Esteve, Daniel; Urbina, Cristian [Quantronics Group, SPEC, CEA-Saclay (France)

    2015-07-01

    Superconductors are characterized by a dissipationless current. Since the work of Josephson 50 years ago, it is known that a supercurrent can even flow through tunnel junctions between superconductors. This Josephson effect also occurs through any type of ''weak links'' between superconductors: non-superconducting materials, constrictions,.. A unified understanding of the Josephson effect has emerged from a mesoscopic description of weak links. It relies on the existence of doublets of localized states that have energies below the superconducting gap: the Andreev bound states. I will present experiments performed on the simplest conductor possible, a single-atom contact between superconductors, that illustrate these concepts. The most recent work demonstrates time-domain manipulation of quantum superpositions of Andreev bound states.

  19. Atomic resolution probe for allostery in the regulatory thin filament

    Science.gov (United States)

    Williams, Michael R.; Lehman, Sarah J.; Tardiff, Jil C.; Schwartz, Steven D.

    2016-01-01

    Calcium binding and dissociation within the cardiac thin filament (CTF) is a fundamental regulator of normal contraction and relaxation. Although the disruption of this complex, allosterically mediated process has long been implicated in human disease, the precise atomic-level mechanisms remain opaque, greatly hampering the development of novel targeted therapies. To address this question, we used a fully atomistic CTF model to test both Ca2+ binding strength and the energy required to remove Ca2+ from the N-lobe binding site in WT and mutant troponin complexes that have been linked to genetic cardiomyopathies. This computational approach is combined with measurements of in vitro Ca2+ dissociation rates in fully reconstituted WT and cardiac troponin T R92L and R92W thin filaments. These human disease mutations represent known substitutions at the same residue, reside at a significant distance from the calcium binding site in cardiac troponin C, and do not affect either the binding pocket affinity or EF-hand structure of the binding domain. Both have been shown to have significantly different effects on cardiac function in vivo. We now show that these mutations independently alter the interaction between the Ca2+ ion and cardiac troponin I subunit. This interaction is a previously unidentified mechanism, in which mutations in one protein of a complex indirectly affect a third via structural and dynamic changes in a second to yield a pathogenic change in thin filament function that results in mutation-specific disease states. We can now provide atom-level insight that is potentially highly actionable in drug design. PMID:26957598

  20. Dynamics of atom-field entanglement in a bimodal cavity

    CERN Document Server

    Deçordi, G L

    2015-01-01

    We investigate some aspects of the dynamics and entanglement of bipartite quantum system (atom-quantized field), coupled to a third ``external" subsystem (quantized field). We make use of the Raman coupled model; a three-level atom in a lambda configuration interacting with two modes of the quantized cavity field. We consider the far off resonance limit, which allows the derivation of an effective Hamiltonian of a two-level atom coupled to the fields. We also make a comparison with the situation in which one of the modes is treated classically rather than prepared in a quantum field (coherent state).

  1. Atomic hydrogen storage. [cryotrapping and magnetic field strength

    Science.gov (United States)

    Woollam, J. A. (Inventor)

    1980-01-01

    Atomic hydrogen, for use as a fuel or as an explosive, is stored in the presence of a strong magnetic field in exfoliated layered compounds such as molybdenum disulfide or an elemental layer material such as graphite. The compound is maintained at liquid temperatures and the atomic hydrogen is collected on the surfaces of the layered compound which are exposed during delamination (exfoliation). The strong magnetic field and the low temperature combine to prevent the atoms of hydrogen from recombining to form molecules.

  2. 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.

  3. Design, fabrication, and control of scanning plasmonic probe for near-field photolithographic applications

    Science.gov (United States)

    Huang, Yu-Yen; Wang, Yuyan; Hoshino, Kazunori; Giese, David; Shrestha, Yujan; Zhang, Xiaojing

    2010-02-01

    We report the design, fabrication and operation of a scanning plasmonic probe compatible with a fully customized Near-field Scanning Microscope system. The probe is a silicon cantilever with a hollow pyramidal probe tip. A silicon dioxide layer was thermally grown to form the probe. A 100 nm thick aluminum layer was then e-beam evaporated onto the released probe tip to form the metal-dielectric interface for surface plasmonic wave propagation. A 500 nm diameter aperture was subsequently milled with the Focus Ion Beam. The probe was controlled with a built-in scanning controller for the probe-sample distance using a force sensing tuning fork. A tapered optical fiber, connected to 405 nm wavelength laser source, was aligned to the backside of the probe tip to serve as the light source. The transmitted light through the aperture was used to expose the photoresist (AZ 5209E), on a piece of cover glass attached on the tuning fork. The probe was controlled for near-field photolithography, where a series of 15 exposures, varied from 0 to 8 minutes, were carried out on the photoresist stepwise at 6.5 μm separation with subsequent 60 seconds development time. The transmitted light beam spot was simulated with a Full Width Half Maximum of 227 nm. Atomic Force Microscope measurement showed a 200 nm lateral resolution for the photolithography. The depths and widths of the developed patterns were linearly correlated with increasing exposure time, showing slopes of 0.76 nm/second and 1.4 nm/second respectively.

  4. Single Cs Atoms as Collisional Probes in a large Rb Magneto-Optical Trap

    CERN Document Server

    Weber, Claudia; Spethmann, Nicolas; Meschede, Dieter; Widera, Artur

    2010-01-01

    We study cold inter-species collisions of Caesium and Rubidium in a strongly imbalanced system with single and few Cs atoms. Observation of the single atom fuorescence dynamics yields insight into light-induced loss mechanisms, while both subsystems can remain in steady-state. This significantly simplifies the analysis of the dynamics, as Cs-Cs collisions are effectively absent and the majority component remains unaffected, allowing us to extract a precise value of the Rb-Cs collision parameter. Extending our results to ground state collisions would allow to use single neutral atoms as coherent probes for larger quantum systems.

  5. Entropy of Field Interacting With Two Atoms in Bell State

    Institute of Scientific and Technical Information of China (English)

    JIAO Zhi-Yong; MA Jun-Mao; LI Ning; FU Xia

    2009-01-01

    In this paper, we investigate entropy properties of the single-mode coherent optical field interacting with the two two-level atoms initially in one of the four Bell states. It is found that the different initial states of the two atoms lead to different evolutions of field entropy and the intensity of the field plays an important role for the evolution properties of field entropy.

  6. Laser-material interaction during atom probe tomography of oxides with embedded metal nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Shinde, D.; Arnoldi, L.; Devaraj, A.; Vella, A.

    2016-10-28

    Oxide-supported metal nano-particles are of great interest in catalysis but also in the development of new large-spectrum-absorption materials. The design of such nano materials requires three-dimensional characterization with a high spatial resolution and elemental selectivity. The laser assisted Atom Probe Tomography (La-APT) presents both these capacities if an accurate understanding of laser-material interaction is developed. In this paper, we focus on the fundamental physics of field evaporation as a function of sample geometry, laser power, and DC electric field for Au nanoparticles embedded in MgO. By understanding the laser-material interaction through experiments and a theoretical model of heat diffusion inside the sample after the interaction with laser pulse, we point out the physical origin of the noise and determine the conditions to reduce it by more than one order of magnitude, improving the sensitivity of the La-APT for metal-dielectric composites. Published by AIP Publishing.

  7. Field enhancement analysis of an apertureless near field scanning optical microscope probe with finite element method

    Institute of Scientific and Technical Information of China (English)

    Weibin Chen; Qiwen Zhan

    2007-01-01

    Plasmonic field enhancement in a fully coated dielectric near field scanning optical microscope (NSOM)probe under radial polarization illumination is analyzed using an axially symmetric three-dimensional (3D)finite element method (FEM) model. The enhancement factor strongly depends on the illumination spot size, taper angle of the probe, and the metal film thickness. The tolerance of the alignment angle is investigated. Probe designs with different metal coatings and their enhancement performance are studied as well. The nanometric spot size at the tip apex and high field enhancement of the apertureless NSOM probe have important potential application in semiconductor metrology.

  8. Probing magnetic fields with Square Kilometre array and its precursors

    CERN Document Server

    Roy, Subhashis; Subramanian, Kandaswamy; Mangalam, Arun; Seshadri, TR; Chand, Hum

    2016-01-01

    Origin of magnetic fields, its structure and effects on dynamical processes in stars to galaxies are not well understood. Lack of a direct probe has hampered its study. The first phase of Square Kilometre Array (SKA-I), will have more than an order of magnitude higher sensitivity than existing radio telescopes. In this contribution, we discuss specific science cases that are of interest to the Indian community concerned with astrophysical turbulence and magnetic fields. The SKA-I will allow observations of a large number of background sources with detectable polarisation and measure their Faraday depths (FDs) through the Milky Way, other galaxies and their circum-galactic medium. This will probe line-of-sight magnetic fields in these objects well and provide field configurations. Detailed comparison of observational data with models which consider various processes giving rise to field amplification and maintenance will then be possible. Such observations will also provide the coherence scale of the fields an...

  9. A Study of the Probe Effect on the Apparent Image of Biological Atomic Force Microscopy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The probe effect on the apparent image of biological atomic force microscopy was explored in this study, and the potential of AFM in conformational study of gene related biological processes was illustrated by the specific nanostructural information of a new antitumor drug binding to DNA.

  10. Modern Focused-Ion-Beam-Based Site-Specific Specimen Preparation for Atom Probe Tomography.

    Science.gov (United States)

    Prosa, Ty J; Larson, David J

    2017-02-06

    Approximately 30 years after the first use of focused ion beam (FIB) instruments to prepare atom probe tomography specimens, this technique has grown to be used by hundreds of researchers around the world. This past decade has seen tremendous advances in atom probe applications, enabled by the continued development of FIB-based specimen preparation methodologies. In this work, we provide a short review of the origin of the FIB method and the standard methods used today for lift-out and sharpening, using the annular milling method as applied to atom probe tomography specimens. Key steps for enabling correlative analysis with transmission electron-beam backscatter diffraction, transmission electron microscopy, and atom probe tomography are presented, and strategies for preparing specimens for modern microelectronic device structures are reviewed and discussed in detail. Examples are used for discussion of the steps for each of these methods. We conclude with examples of the challenges presented by complex topologies such as nanowires, nanoparticles, and organic materials.

  11. Probing atomic structure and Majorana wavefunctions in mono-atomic Fe chains on superconducting Pb surface

    Science.gov (United States)

    Pawlak, Rémy; Kisiel, Marcin; Klinovaja, Jelena; Meier, Tobias; Kawai, Shigeki; Glatzel, Thilo; Loss, Daniel; Meyer, Ernst

    2016-11-01

    Motivated by the striking promise of quantum computation, Majorana bound states (MBSs) in solid-state systems have attracted wide attention in recent years. In particular, the wavefunction localisation of MBSs is a key feature and is crucial for their future implementation as qubits. Here we investigate the spatial and electronic characteristics of topological superconducting chains of iron atoms on the surface of Pb(110) by combining scanning tunnelling microscopy and atomic force microscopy. We demonstrate that the Fe chains are mono-atomic, structured in a linear manner and exhibit zero-bias conductance peaks at their ends, which we interpret as signature for a MBS. Spatially resolved conductance maps of the atomic chains reveal that the MBSs are well localised at the chain ends (≲25 nm), with two localisation lengths as predicted by theory. Our observation lends strong support to use MBSs in Fe chains as qubits for quantum-computing devices.

  12. Laser terahertz emission microscopy with near-field probes

    DEFF Research Database (Denmark)

    Pedersen, Pernille Klarskov; Mittleman, Daniel M.

    2016-01-01

    Using an AFM, an optical near-field image at 800 nm of a dipole antenna for THz emission is measured, and by simultaneously collecting the emitted THz radiation, the laser light confined under the AFM probe gives a THz emission resolution of less than 50 nm.......Using an AFM, an optical near-field image at 800 nm of a dipole antenna for THz emission is measured, and by simultaneously collecting the emitted THz radiation, the laser light confined under the AFM probe gives a THz emission resolution of less than 50 nm....

  13. Advanced fabrication process for combined atomic force-scanning electrochemical microscopy (AFM-SECM) probes.

    Science.gov (United States)

    Eifert, Alexander; Mizaikoff, Boris; Kranz, Christine

    2015-01-01

    An advanced software-controlled focused ion beam (FIB) patterning process for the fabrication of combined atomic force-scanning electrochemical microscopy (AFM-SECM) probes is reported. FIB milling is a standard process in scanning probe microscopy (SPM) for specialized SPM probe fabrication. For AFM-SECM, milling of bifunctional probes usually requires several milling steps. Milling such complex multi-layer/multi-material structures using a single milling routine leads to significantly reduced fabrication times and costs. Based on an advanced patterning routine, a semi-automated FIB milling routine for fabricating combined AFM-SECM probes with high reproducibility is presented with future potential for processing at a wafer level. The fabricated bifunctional probes were electrochemically characterized using cyclic voltammetry, and their performance for AFM-SECM imaging experiments was tested. Different insulation materials (Parylene-C and SixNy) have been evaluated with respect to facilitating the overall milling process, the influence on the electrochemical behavior and the long-term stability of the obtained probes. Furthermore, the influence of material composition and layer sequence to the overall shape and properties of the combined probes were evaluated.

  14. Cold atom trap with zero residual magnetic field: the ac magneto-optical trap.

    Science.gov (United States)

    Harvey, Matthew; Murray, Andrew James

    2008-10-24

    A novel atom trap is described using alternating current to generate the magnetic B field, together with high speed polarization switching of the damping laser field. This combination produces a trap as effective as a standard magneto-optical trap (MOT), with the advantage that the average B field is zero. No net current is hence induced in surrounding conductive elements, and the B field produced by the ac MOT is found to switch off >300 times faster than a conventional MOT. New experiments can hence be performed, including charged particle probing or detection of the cold target ensemble.

  15. Design and optimization of a harmonic probe with step cross section in multifrequency atomic force microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Cai, Jiandong; Zhang, Li [Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Wang, Michael Yu, E-mail: michael.wang@nus.edu.sg [Department of Mechanical and Automation Engineering, The Chinese University of Hong Kong, Shatin, NT (Hong Kong); Department of Mechanical Engineering, National University of Singapore, Singapore 117575 (Singapore)

    2015-12-15

    In multifrequency atomic force microscopy (AFM), probe’s characteristic of assigning resonance frequencies to integer harmonics results in a remarkable improvement of detection sensitivity at specific harmonic components. The selection criterion of harmonic order is based on its amplitude’s sensitivity on material properties, e.g., elasticity. Previous studies on designing harmonic probe are unable to provide a large design capability along with maintaining the structural integrity. Herein, we propose a harmonic probe with step cross section, in which it has variable width in top and bottom steps, while the middle step in cross section is kept constant. Higher order resonance frequencies are tailored to be integer times of fundamental resonance frequency. The probe design is implemented within a structural optimization framework. The optimally designed probe is micromachined using focused ion beam milling technique, and then measured with an AFM. The measurement results agree well with our resonance frequency assignment requirement.

  16. Mapping and correcting respiration-induced field changes in the brain using fluorine field probes

    DEFF Research Database (Denmark)

    Andersen, Mads; Madsen, Kristoffer; Hanson, Lars G.;

    2014-01-01

    lacking. In this study a comparison between scanner-acquired field maps of the head, and corresponding field probe measurements is presented both during in- and expiration. In addition, the field probe measurements have been used to perform real-time updating of the linear shim- settings. Methods. Setup...... slice of one of the volunteers. Field probe fits, scanner B0 maps, and corrected B0 maps are shown for the case of fitting up to first and second order. The tables show p-values from statistical tests over entire volumes. Discussion: Using a significance level of 0.05, the p-values in table 1 show...

  17. Near-Field Photothermal Heating with a Plasmonic Nanofocusing Probe

    Science.gov (United States)

    Chen, Xiang; Dong, Biqing; Balogun, Oluwaseyi

    2016-03-01

    Noble metal nanostructures support plasmon resonances—collective oscillation of charge carriers at optical frequencies—and serve as effective tools to create bright light sources at the nanoscale. These sources are useful in broad application areas including, super-resolution imaging and spectroscopy, nanolithography, and near-field optomechanical transducers. The feasibility of these applications relies on efficient conversion of free-space propagating light to plasmons. Recently, we demonstrated a hybrid nanofocusing scheme for efficient coupling of light to plasmons at the apex of a scanning probe. In the approach, free-space light is coupled to propagating surface plasmon polaritons (SPPs) on the tapered shaft of the scanning probe. The SPPs propagate adiabatically towards the probe tip where they are coupled to localized plasmons (LSPs). The nanofocusing scheme was explored in a near-field scanning optical microscope for super-resolution imaging, near-field transduction of nanomechanical vibrations, and local detection of ultrasound. Owing to the strong concentration of light at the probe, significant heating of the tip and a sample positioned in the optical near-field is expected. This paper investigates the local heating produced by the plasmonic nanofocusing probe under steady-state conditions using the tip-enhanced Raman scattering approach. In addition, a finite element model is explored to study the coupling of free propagating light to LSPs, and to estimate the temperature rise expected in a halfspace heated by absorption of the LSPs. This study has implications for exploring the plasmonic nanofocusing probe in heat-assisted nanofabrication and fundamental studies of nanoscale heat transport in materials.

  18. Nanoscale magnetic field mapping with a single spin scanning probe magnetometer

    Energy Technology Data Exchange (ETDEWEB)

    Rondin, L.; Tetienne, J.-P.; Spinicelli, P.; Roch, J.-F.; Jacques, V. [Laboratoire de Photonique Quantique et Moleculaire, Ecole Normale Superieure de Cachan and CNRS UMR 8537, 94235 Cachan Cedex (France); Dal Savio, C.; Karrai, K. [Attocube systems AG, Koeniginstrasse 11A RGB, Munich 80539 (Germany); Dantelle, G. [Laboratoire de Physique de la Matiere Condensee, Ecole Polytechnique and CNRS UMR 7643, 91128 Palaiseau (France); Thiaville, A.; Rohart, S. [Laboratoire de Physique des Solides, Universite Paris-Sud and CNRS UMR 8502, 91405 Orsay (France)

    2012-04-09

    We demonstrate quantitative magnetic field mapping with nanoscale resolution, by applying a lock-in technique on the electron spin resonance frequency of a single nitrogen-vacancy defect placed at the apex of an atomic force microscope tip. In addition, we report an all-optical magnetic imaging technique which is sensitive to large off-axis magnetic fields, thus extending the operation range of diamond-based magnetometry. Both techniques are illustrated by using a magnetic hard disk as a test sample. Owing to the non-perturbing and quantitative nature of the magnetic probe, this work should open up numerous perspectives in nanomagnetism and spintronics.

  19. Constraining symmetron fields with atom interferometry

    CERN Document Server

    Burrage, Clare; Stevenson, James; Thrussell, Ben

    2016-01-01

    We apply the new constraints from atom-interferometry searches for screening mechanisms to the symmetron model, finding that these experiments exclude a previously unexplored region of parameter space. We discuss the possibility of networks of domain walls forming in the vacuum chamber, and how this could be used to discriminate between models of screening.

  20. Probe Station and Near-Field Scanner for Testing Antennas

    Science.gov (United States)

    Zaman, Afroz; Lee, Richard Q.; Darby, William G.; Barr, Philip J.; Miranda, Felix A.; Lambert, Kevin

    2006-01-01

    A facility that includes a probe station and a scanning open-ended waveguide probe for measuring near electromagnetic fields has been added to Glenn Research Center's suite of antenna-testing facilities, at a small fraction of the cost of the other facilities. This facility is designed specifically for nondestructive characterization of the radiation patterns of miniaturized microwave antennas fabricated on semiconductor and dielectric wafer substrates, including active antennas that are difficult to test in traditional antenna-testing ranges because of fragility, smallness, or severity of DC-bias or test-fixture requirements. By virtue of the simple fact that a greater fraction of radiated power can be captured in a near-field measurement than in a conventional far-field measurement, this near-field facility is convenient for testing miniaturized antennas with low gains.

  1. Near-Field Optical Microscopy and Spectroscopy with Pointed Probes

    Science.gov (United States)

    2006-01-01

    metal nanostructure can be viewed as an optical antenna . Of course, the efficiency depends on the material composition and the geometry of the...nanostructure. A simple form of optical antenna is a single ellipsoidal particle. This particle ex- hibits a distinct resonance for which the field...Grober RD, Schoelkopf RJ, Prober DE. 1997. Optical antenna : towards a unity efficiency near-field optical probe. Appl. Phys. Lett. 70:1354 54. Farahani

  2. Production and detection of atomic hexadecapole at Earth's magnetic field.

    Science.gov (United States)

    Acosta, V M; Auzinsh, M; Gawlik, W; Grisins, P; Higbie, J M; Jackson Kimball, D F; Krzemien, L; Ledbetter, M P; Pustelny, S; Rochester, S M; Yashchuk, V V; Budker, D

    2008-07-21

    Optical magnetometers measure magnetic fields with extremely high precision and without cryogenics. However, at geomagnetic fields, important for applications from landmine removal to archaeology, they suffer from nonlinear Zeeman splitting, leading to systematic dependence on sensor orientation. We present experimental results on a method of eliminating this systematic error, using the hexadecapole atomic polarization moment. In particular, we demonstrate selective production of the atomic hexadecapole moment at Earth's magnetic field and verify its immunity to nonlinear Zeeman splitting. This technique promises to eliminate directional errors in all-optical atomic magnetometers, potentially improving their measurement accuracy by several orders of magnitude.

  3. Effect of atomization gas pressure variation on gas flow field in supersonic gas atomization

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In this paper, a computational fluid flow model was adopted to investigate the effect of varying atomization gas pressure (P0) on the gas flow field in supersonic gas atomization. The influence of P0 on static pressure and velocity magnitude of the central axis of the flow field was also examined. The numerical results indicate that the maximum gas velocity within the gas field increases with increasing P0. The aspiration pressure (ΔP) is found to decrease as P0 increases at a lower atomization gas pressure. However, at a higher atomization gas pressure increasing P0 causes the opposite: the higher atomization gas pressure, the higher aspiration pressure. The alternation of ΔP is caused by the variations of stagnation point pressure and location of Mach disk, while hardly by the location of stagnation point. A radical pressure gradient is formed along the tip of the delivery tube and increases as P0 increases.

  4. A filtering method to reveal crystalline patterns from atom probe microscopy desorption maps.

    Science.gov (United States)

    Yao, Lan

    2016-01-01

    A filtering method to reveal the crystallographic information present in Atom Probe Microscopy (APM) data is presented. The method filters atoms based on the time difference between their evaporation and the evaporation of the previous atom. Since this time difference correlates with the location and the local structure of the evaporating atoms on the surface, it can be used to reveal any crystallographic information contained within APM data. The demonstration of this method is illustrated on: •A pure Al specimen for which crystallographic poles are clearly visible on the desorption patterns easily indexed.•Three Fe-15at.% Cr datasets where crystallographic patterns are less obvious and require this filtering method.

  5. Probing Magnetic Fields with Square Kilometre Array and its Precursors

    Indian Academy of Sciences (India)

    Subhashis Roy; Sharanya Sur; Kandaswamy Subramanian; Arun Mangalam; T. R. Seshadri; Hum Chand

    2016-12-01

    Origin of magnetic fields, its structure and effects on dynamical processes in stars to galaxies are not well understood. Lack of a direct probe has remained a problem for its study. The first phase of Square Kilometre Array (SKA-I), will have almost an order of magnitude higher sensitivity than the best existing radio telescope at GHz frequencies. In this contribution, we discuss specific science cases that are of interest to the Indian community concerned with astrophysical turbulence and magnetic fields. The SKA-I will allow observations of a large number of background sources with detectable polarization and measure their Faraday depths (FDs) through the Milky Way, other galaxies and their circum-galactic mediums. This will probe line-of-sight magnetic fields in these objects well and provide field configurations. Detailed comparison of observational data (e.g., pitch angles in spirals) with models which consider various processes giving rise to field amplification and maintenance (e.g., various types of dynamo models) will then be possible. Such observations will also provide the coherence scale of the fields and its random component through RM structure function. Measuring the random component is important to characterize turbulence in the medium. Observations of FDs with redshift will provide important information on magnetic field evolution as a function of redshift. The background sources could also be used to probe magnetic fields and its coherent scale in galaxy clusters and in bridges formed between interacting galaxies. Other than FDs, sensitive observations of synchrotron emission from galaxies will provide complimentary information on their magnetic field strengths in the sky plane. The core shift measurements of AGNs can provide more precise measurements of magnetic field in the sub parsec region near the black hole and its evolution. The low band of SKA-I will also be useful to study circularly polarized emission from Sun and comparing various

  6. Towards a quantum Hall effect for atoms using electric fields

    CERN Document Server

    Ericsson, M; Ericsson, Marie; Sjoqvist, Erik

    2002-01-01

    An atomic analogue of Landau quantization based on the Aharonov-Casher (AC) interaction is developed. The effect provides a first step towards an atomic quantum Hall system using electric fields, which may be realized in a Bose-Einstein condensate.

  7. Classical stabilization of the hydrogen atom in a monochromatic field

    Energy Technology Data Exchange (ETDEWEB)

    Benvenuto, F.; Casati, G. (Dipartimento di Fisica dell' Universita, Via Castelnuovo 7, 22100 Como (Italy)); Shepelyansky, D.L. (Laboratoire de Physique Quantique, Universite Paul Sabatier, 31062, Toulouse (France))

    1993-02-01

    We report the results of analytical and numerical investigations on the ionization of a classical atom in a strong, linearly polarized, monochromatic field. We show that the ionization probability decreases with increasing field intensity at field amplitudes much larger than the classical chaos border. This effect should be observable in real laboratory experiments.

  8. Light-induced gauge fields for ultracold atoms

    Science.gov (United States)

    Goldman, N.; Juzeliūnas, G.; Öhberg, P.; Spielman, I. B.

    2014-12-01

    Gauge fields are central in our modern understanding of physics at all scales. At the highest energy scales known, the microscopic universe is governed by particles interacting with each other through the exchange of gauge bosons. At the largest length scales, our Universe is ruled by gravity, whose gauge structure suggests the existence of a particle—the graviton—that mediates the gravitational force. At the mesoscopic scale, solid-state systems are subjected to gauge fields of different nature: materials can be immersed in external electromagnetic fields, but they can also feature emerging gauge fields in their low-energy description. In this review, we focus on another kind of gauge field: those engineered in systems of ultracold neutral atoms. In these setups, atoms are suitably coupled to laser fields that generate effective gauge potentials in their description. Neutral atoms ‘feeling’ laser-induced gauge potentials can potentially mimic the behavior of an electron gas subjected to a magnetic field, but also, the interaction of elementary particles with non-Abelian gauge fields. Here, we review different realized and proposed techniques for creating gauge potentials—both Abelian and non-Abelian—in atomic systems and discuss their implication in the context of quantum simulation. While most of these setups concern the realization of background and classical gauge potentials, we conclude with more exotic proposals where these synthetic fields might be made dynamical, in view of simulating interacting gauge theories with cold atoms.

  9. Light-induced gauge fields for ultracold atoms.

    Science.gov (United States)

    Goldman, N; Juzeliūnas, G; Öhberg, P; Spielman, I B

    2014-12-01

    Gauge fields are central in our modern understanding of physics at all scales. At the highest energy scales known, the microscopic universe is governed by particles interacting with each other through the exchange of gauge bosons. At the largest length scales, our Universe is ruled by gravity, whose gauge structure suggests the existence of a particle-the graviton-that mediates the gravitational force. At the mesoscopic scale, solid-state systems are subjected to gauge fields of different nature: materials can be immersed in external electromagnetic fields, but they can also feature emerging gauge fields in their low-energy description. In this review, we focus on another kind of gauge field: those engineered in systems of ultracold neutral atoms. In these setups, atoms are suitably coupled to laser fields that generate effective gauge potentials in their description. Neutral atoms 'feeling' laser-induced gauge potentials can potentially mimic the behavior of an electron gas subjected to a magnetic field, but also, the interaction of elementary particles with non-Abelian gauge fields. Here, we review different realized and proposed techniques for creating gauge potentials-both Abelian and non-Abelian-in atomic systems and discuss their implication in the context of quantum simulation. While most of these setups concern the realization of background and classical gauge potentials, we conclude with more exotic proposals where these synthetic fields might be made dynamical, in view of simulating interacting gauge theories with cold atoms.

  10. Generating Entanglement between Atomic Spins with Low-Noise Probing of an Optical Cavity

    CERN Document Server

    Cox, Kevin C; Greve, Graham P; Thompson, James K

    2015-01-01

    Atomic projection noise limits the ultimate precision of all atomic sensors, including clocks, inertial sensors, magnetometers, etc. The independent quantum collapse of $N$ atoms into a definite state (for example spin up or down) leads to an uncertainty $\\Delta \\theta_{SQL}=1/\\sqrt{N}$ in the estimate of the quantum phase accumulated during a Ramsey sequence or its many generalizations. This phase uncertainty is referred to as the standard quantum limit. Creating quantum entanglement between the $N$ atoms can allow the atoms to partially cancel each other's quantum noise, leading to reduced noise in the phase estimate below the standard quantum limit. Recent experiments have demonstrated up to $10$~dB of phase noise reduction relative to the SQL by making collective spin measurements. This is achieved by trapping laser-cooled Rb atoms in an optical cavity and precisely measuring the shift of the cavity resonance frequency by an amount that depends on the number of atoms in spin up. Detecting the probe light ...

  11. Phase decomposition and ordering in Ni-11.3 at.% Ti studied with atom probe tomography

    KAUST Repository

    Al-Kassab, Talaat

    2014-09-01

    The decomposition behavior of Ni-rich Ni-Ti was reassessed using Tomographic Atom Probe (TAP) and Laser Assisted Wide Angle Tomographic Atom Probe. Single crystalline specimens of Ni-11.3at.% Ti were investigated, the states selected from the decomposition path were the metastable γ″ and γ\\' states introduced on the basis of small-angle neutron scattering (SANS) and the two-phase model for evaluation. The composition values of the precipitates in these states could not be confirmed by APT data as the interface of the ordered precipitates may not be neglected. The present results rather suggest to apply a three-phase model for the interpretation of SANS measurements, in which the width of the interface remains nearly unchanged and the L12 structure close to 3:1 stoichiometry is maintained in the core of the precipitates from the γ″ to the γ\\' state. © 2014 Elsevier Ltd.

  12. Electron spin polarization in strong-field ionization of xenon atoms

    Science.gov (United States)

    Hartung, Alexander; Morales, Felipe; Kunitski, Maksim; Henrichs, Kevin; Laucke, Alina; Richter, Martin; Jahnke, Till; Kalinin, Anton; Schöffler, Markus; Schmidt, Lothar Ph. H.; Ivanov, Misha; Smirnova, Olga; Dörner, Reinhard

    2016-08-01

    As a fundamental property of the electron, the spin plays a decisive role in the electronic structure of matter, from solids to molecules and atoms, for example, by causing magnetism. Yet, despite its importance, the spin dynamics of the electrons released during the interaction of atoms with strong ultrashort laser pulses has remained experimentally unexplored. Here, we report the experimental detection of electron spin polarization by the strong-field ionization of xenon atoms and support our results with theoretical analysis. We found up to 30% spin polarization changing its sign with electron energy. This work opens the new dimension of spin to strong-field physics. It paves the way to the production of sub-femtosecond spin-polarized electron pulses with applications ranging from probing the magnetic properties of matter at ultrafast timescales to testing chiral molecular systems with sub-femtosecond temporal and sub-ångström spatial resolutions.

  13. Atom-probe tomography of tribological boundary films resulting from boron-based oil additives

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yoon-Jun; Baik, Sung-Il; Bertolucci-Coelho, Leonardo; Mazzaferro, Lucca; Ramirez, Giovanni; Erdemir, Ali; Seidman, D K

    2016-01-15

    Correlative characterization using atom-probe tomography (APT) and transmission electron microscopy (TEM) was performed on a tribofilm formed during sliding frictional testing with a fully formulated engine oil, which also contains a boron-based additive. The tribofilm formed is ~15 nm thick and consists of oxides of iron and compounds of B, Ca, P, and S, which are present in the additive. This study provides strong evidence for boron being embedded in the tribofilm, which effectively reduces friction and wear losses.

  14. Influence of atomic force microscope (AFM) probe shape on adhesion force measured in humidity environment

    Institute of Scientific and Technical Information of China (English)

    阳丽; 涂育松; 谭惠丽

    2014-01-01

    In micro-manipulation, the adhesion force has very important influence on behaviors of micro-objects. Here, a theoretical study on the effects of humidity on the adhesion force is presented between atomic force microscope (AFM) tips and substrate. The analysis shows that the precise tip geometry plays a critical role on humidity depen-dence of the adhesion force, which is the dominant factor in manipulating micro-objects in AFM experiments. For a blunt (paraboloid) tip, the adhesion force versus humidity curves tends to the apparent contrast (peak-to-valley corrugation) with a broad range. This paper demonstrates that the abrupt change of the adhesion force has high correla-tion with probe curvatures, which is mediated by coordinates of solid-liquid-vapor contact lines (triple point) on the probe profiles. The study provides insights for further under-standing nanoscale adhesion forces and the way to choose probe shapes in manipulating micro-objects in AFM experiments.

  15. Microstructural characterization of an Al-li-mg-cu alloy by correlative electron tomography and atom probe tomography.

    Science.gov (United States)

    Xiong, Xiangyuan; Weyland, Matthew

    2014-08-01

    Correlative electron tomography and atom probe tomography have been carried out successfully on the same region of a commercial 8090 aluminum alloy (Al-Li-Mg-Cu). The combination of the two techniques allows accurate geometric reconstruction of the atom probe tomography data verified by crystallographic information retrieved from the reconstruction. Quantitative analysis of the precipitate phase compositions and volume fractions of each phase have been obtained from the atom probe tomography and electron tomography at various scales, showing strong agreement between both techniques.

  16. Dynamical properties of moving atom–atom entanglement and entanglement between two atoms with optical field

    Indian Academy of Sciences (India)

    S Abdel-Khalek; S H A Halawani

    2015-12-01

    Quantum information technology largely relies on a sophisticated and fragile resource, called quantum entanglement, which exhibits a highly nontrivial manifestation of the coherent superposition of the states of composite quantum systems. In this paper, we study the interaction between the general and even coherent fields with moving and stationary two two-level atoms. In this regard, this paper investigates the von Neumann entropy and the atoms–field tangle as a measure of entanglement between the general and even coherent fields with the two atoms. Also, the entanglement between the two atoms using concurrence and negativity during time evolution is discussed. This paper examines the effects of multiphoton transitions and initial state setting on the entanglement for the system under consideration. Finally, the results demonstrate an important phenomenon such as the sudden death and birth of entanglement when the two atoms are initially in entangled states.

  17. NMR Probe as a Field Marker in a Quadrupole

    CERN Document Server

    Caspers, Friedhelm; CERN. Geneva. SPS and LEP Division

    1999-01-01

    A study has started to improve the reproducibility of the focusing elements of the SPS for its operation as LHC injector. This note is a copy of the oral presentation to the IMMW11 seminar, which took place at Brookhaven National Laboratory in September 1999. It indicates the feasibility of the creation of a "G-Train" via a NMR probe used as a field marker in a reference quadrupole.

  18. Atomic species recognition on oxide surfaces using low temperature scanning probe microscopy

    Science.gov (United States)

    Ma, Zong Min; Shi, Yun Bo; Mu, Ji Liang; Qu, Zhang; Zhang, Xiao Ming; Qin, Li; Liu, Jun

    2017-02-01

    In scanning probe microscopy (SPM), the chemical properties and sharpness of the tips of the cantilever greatly influence the scanning of a sample surface. Variation in the chemical properties of the sharp tip apex can induce transformation of the SPM images. In this research, we explore the relationship between the tip and the structure of a sample surface using dynamic atomic force microscopy (AFM) on a Cu(110)-O surface under ultra-high vacuum (UHV) at low temperature (78 K). We observed two different c(6 × 2) phase types in which super-Cu atoms show as a bright spot when the tip apex is of O atoms and O atoms show as a bright spot when the tip apex is of Cu atoms. We also found that the electronic state of the tip has a serious effect on the resolution and stability of the sample surface, and provide an explanation for these phenomena. This technique can be used to identify atom species on sample surfaces, and represents an important development in the SPM technique.

  19. Atom-column distinction by Kikuchi pattern observed by an aberration-corrected convergent electron probe.

    Science.gov (United States)

    Saitoh, Koh; Tatara, Yoshihide; Tanaka, Nobuo

    2010-01-01

    Kikuchi patterns of an MgO crystal at the [110] incidence have been taken by a sub-angstrom electron beam focused on the single atom-column. A significant change in intensity has been observed in the 111 band; that is, the contrast in the central and side bands is reversed depending on the illuminated atom-column. The contrast reversal in the 111 band has been reproduced by multislice simulation using the frozen-phonon approach. The beam-position dependence of the 111 band intensity can be interpreted by electron channelling and the reciprocity theorem. The anomalous Kikuchi pattern can be a probe for identifying the illuminated atom-column, which is useful for column-by-column electron energy-loss spectroscopy and X-ray emission spectroscopy.

  20. Pulsed beams as field probes for precision measurement

    OpenAIRE

    Hudson, J. J.; Ashworth, H. T.; Kara, D. M.; Tarbutt, M. R.; Sauer, B.E.; Hinds, E. A.

    2007-01-01

    We describe a technique for mapping the spatial variation of static electric, static magnetic, and rf magnetic fields using a pulsed atomic or molecular beam. The method is demonstrated using a beam designed to measure the electric dipole moment of the electron. We present maps of the interaction region, showing sensitivity to (i) electric field variation of 1.5 V/cm at 3.3 kV/cm with a spatial resolution of 15 mm; (ii) magnetic field variation of 5 nT with 25 mm resolution; (iii) radio-frequ...

  1. Bow-tie optical antenna probes for single-emitter scanning near-field optical microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Farahani, Javad N [Nano-Optics Group, National Center of Competence for Research in Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Eisler, Hans-Juergen [Nano-Optics Group, National Center of Competence for Research in Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Pohl, Dieter W [Nano-Optics Group, National Center of Competence for Research in Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland); Pavius, Michael [Center of MicroNanoTechnology (CMI), Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Flueckiger, Philippe [Center of MicroNanoTechnology (CMI), Ecole Polytechnique Federale de Lausanne (EPFL), CH-1015 Lausanne (Switzerland); Gasser, Philippe [EMPA, Swiss Federal Laboratories for Materials Testing and Research, Electronics/Metrology Laboratory, Ueberlandstrasse 129, CH-8600 Duebendorf (Switzerland); Hecht, Bert [Nano-Optics Group, National Center of Competence for Research in Nanoscale Science, Institute of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel (Switzerland)

    2007-03-28

    A method for the fabrication of bow-tie optical antennas at the apex of pyramidal Si{sub 3}N{sub 4} atomic force microscopy tips is described. We demonstrate that these novel optical probes are capable of sub-wavelength imaging of single quantum dots at room temperature. The enhanced and confined optical near-field at the antenna feed gap leads to locally enhanced photoluminescence (PL) of single quantum dots. Photoluminescence quenching due to the proximity of metal is found to be insignificant. The method holds promise for single quantum emitter imaging and spectroscopy at spatial resolution limited by the engineered antenna gap width exclusively.

  2. Non—conservation of energy arising from atomic dipole interactions and its effects on light field and coupled atoms

    Institute of Scientific and Technical Information of China (English)

    DongChuan-Hua

    2003-01-01

    The interactions between coulpled atoms and a single mode of a quantized electromagnetic field, which involve the terms originating from the dipole interactions, are discussed. In the usual Jaynes-Cummings model for coupled atoms, the terms of non-conservation of energy originating from dipole interactions are neglected, however, we take them into consideration in this paper. The effects of these terms on the evolutions of quantum statistic properties and squeezing of the field, the squeezing of atomic dipole moments and atomic population inversion are investigated. It has been shown that the coupling between atoms modulates these evolutions of fields and atoms. The terms of non-conservation of energy affect these evolutions of field and atoms slightly. They also have effects on the squeezing of the field, the squeezing of atomic dipole and atomic population inversions. The initial states of atoms also affect these properties.

  3. Non-conservation of energy arising from atomic dipole interactions and its effects on light field and coupled atoms

    Institute of Scientific and Technical Information of China (English)

    董传华

    2003-01-01

    The interactions between coupled atoms and a single mode of a quantized electromagnetic field, which involve the terms originating from the dipole interactions, are discussed. In the usual Jaynes Cummings model for coupled atoms,the terms of non-conservation of energy originating from dipole interactions are neglected, however, we take them into consideration in this paper. The effects of these terms on the evolutions of quantum statistic properties and squeezing of the field, the squeezing of atomic dipole moments and atomic population inversion are investigated. It has been shown that the coupling between atoms modulates these evolutions of fields and atoms. The terms of non-conservation of energy affect these evolutions of fields and atoms slightly. They also have effects on the squeezing of the field, the squeezing of atomic dipole and atomic population inversions. The initial states of atoms also affect these properties.

  4. A new probe of magnetic fields in the pre-reionization epoch: I. Formalism

    CERN Document Server

    Venumadhav, Tejaswi; Gluscevic, Vera; Mishra, Abhilash; Hirata, Christopher M

    2014-01-01

    We propose a method of measuring extremely weak magnetic fields in the inter galactic medium prior to and during the epoch of cosmic reionization. The method utilizes the Larmor precession of spin-polarized neutral hydrogen in the triplet state of the hyperfine transition. The resulting change in the brightness temperature fluctuations encodes information about the magnetic field the atoms are immersed in. The method is most suited to probing fields that are coherent on large scales. Due to the long lifetime of the triplet state of the 21-cm transition, this technique is naturally sensitive to extremely weak field strengths, of order $10^{-19}$ G (or $10^{-21}$ G if scaled to the present day). Therefore, this might open up the possibility of probing primordial magnetic fields just prior to reionization. Moreover, such measurements are unaffected by later magnetic fields since 21-cm observations preserve redshift information. If the magnetic fields are much stronger, it is still possible to recover information...

  5. Construction of a New Atom-Probe and its Application to Study of Solute Behavior in Dilute Iron Base Alloys.

    Science.gov (United States)

    Al-Saleh, Kamal Amein

    An ultra-high-vacuum (UHC) time-of-flight atom -probe field ion microscope (ToF atom-probe) has been designed, constructed and operated successfully. The new ToF atom -probe is equipped with the following: (1) A poschenrieder electrostatic focusing lens for high mass resolution and noise-free performance, (2) a second chevron-channel plate -phosphor screen assembly in front of the Poschenrieder lens to be used for precise determination of the probing area and detection efficiency, (3) a quick-sample change chamber with a vacuum lock which is also used as a reaction chamber, (4) a closed-cycle liquid He refrigeration unit to cool a specimen tip down to 25 K for a better quality image, and (5) an automated data acquisition system which consists of an 8-channel digital timer with a 200 MHz internal clock and a DEC MINCII minicomputer which is capable of performing data collection at a pulse repetition rate up to 100/sec, with a mass resolution m/(DELTA)m of (TURN)1200. Using this instrument, the following alloys have been investigated: (1) Fe-0.29; 0.64; and 1.46 wt % Ti alloys. It was found that Ti segregates to the surface upon annealing the tip in vacuum at and above 650(DEGREES)C and its concentration is approximately 90% at the first layer, 20% at the second layer, 10% at the third layer and the bulk value thereafter. CO and H(,2) alone appear to have no effect at all on the segregation of Ti. However, oxygen has had profound effect on the behavior of Ti, demonstrating the initial stages of both oxidation (TiO scale formation) and internal oxidation (TiO, FeO clusters in Fe matrix) for the first time on an atomic scale. (2) Fe-0.17 wt % P alloy: P segregation to the interface was studied at the temperatures of 300 to 600(DEGREES)C. In one of the samples a carbide precipitate was found with an approximate composition of M(,5)C, where phosphorus was rejected by the M(,5)C precipitate and upon annealing the tip in vacuum P segregated at the interface.

  6. Using Jupiter's gravitational field to probe the Jovian convective dynamo.

    Science.gov (United States)

    Kong, Dali; Zhang, Keke; Schubert, Gerald

    2016-03-23

    Convective motion in the deep metallic hydrogen region of Jupiter is believed to generate its magnetic field, the strongest in the solar system. The amplitude, structure and depth of the convective motion are unknown. A promising way of probing the Jovian convective dynamo is to measure its effect on the external gravitational field, a task to be soon undertaken by the Juno spacecraft. We calculate the gravitational signature of non-axisymmetric convective motion in the Jovian metallic hydrogen region and show that with sufficiently accurate measurements it can reveal the nature of the deep convection.

  7. Determination of hyperfine fields orientation in nuclear probe techniques

    Science.gov (United States)

    Szymański, K.; Olszewski, W.; Satuła, D.; Gawryluk, D. J.; Krzton-Maziopa, A.; Kalska-Szostko, B.

    2017-02-01

    One of the most popular nuclear probes, 57Fe is used for the investigation of orientations of hyperfine fields and also for the determination of other important properties. In particular, the orientation of iron magnetic moments can be unambiguously determined, including its signs. Experiments with polarized radiation are presented with regard to selected systems. Orientation of electric field gradient is used for acquiring information about the shape of the texture-free spectra. Applications on the analysis of iron-based superconductors are presented.

  8. Resonances of the helium atom in a strong magnetic field

    DEFF Research Database (Denmark)

    Lühr, Armin Christian; Al-Hujaj, Omar-Alexander; Schmelcher, Peter

    2007-01-01

    We present an investigation of the resonances of a doubly excited helium atom in a strong magnetic field covering the regime B=0–100  a.u. A full-interaction approach which is based on an anisotropic Gaussian basis set of one-particle functions being nonlinearly optimized for each field strength...

  9. Real-time near-field terahertz imaging with atomic optical fluorescence

    Science.gov (United States)

    Wade, C. G.; Šibalić, N.; de Melo, N. R.; Kondo, J. M.; Adams, C. S.; Weatherill, K. J.

    2017-01-01

    Terahertz (THz) near-field imaging is a flourishing discipline, with applications from fundamental studies of beam propagation to the characterization of metamaterials and waveguides. Beating the diffraction limit typically involves rastering structures or detectors with length scale shorter than the radiation wavelength; in the THz domain this has been achieved using a number of techniques including scattering tips and apertures. Alternatively, mapping THz fields onto an optical wavelength and imaging the visible light removes the requirement for scanning a local probe, speeding up image collection times. Here, we report THz-to-optical conversion using a gas of highly excited Rydberg atoms. By collecting THz-induced optical fluorescence we demonstrate a real-time image of a THz standing wave and use well-known atomic properties to calibrate the THz field strength.

  10. Atom probe tomography characterisation of a laser diode structure grown by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, Samantha E.; Humphreys, Colin J.; Oliver, Rachel A. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge, CB2 3QZ (United Kingdom); Smeeton, Tim M.; Hooper, Stewart E.; Heffernan, Jonathan [Sharp Laboratories of Europe Limited, Edmund Halley Road, Oxford Science Park, Oxford, OX4 4GB (United Kingdom); Saxey, David W.; Smith, George D. W. [Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH (United Kingdom)

    2012-03-01

    Atom probe tomography (APT) has been used to achieve three-dimensional characterization of a III-nitride laser diode (LD) structure grown by molecular beam epitaxy (MBE). Four APT data sets have been obtained, with fields of view up to 400 nm in depth and 120 nm in diameter. These data sets contain material from the InGaN quantum well (QW) active region, as well as the surrounding p- and n-doped waveguide and cladding layers, enabling comprehensive study of the structure and composition of the LD structure. Two regions of the same sample, with different average indium contents (18% and 16%) in the QW region, were studied. The APT data are shown to provide easy access to the p-type dopant levels, and the composition of a thin AlGaN barrier layer. Next, the distribution of indium within the InGaN QW was analyzed, to assess any possible inhomogeneity of the distribution of indium (''indium clustering''). No evidence for a statistically significant deviation from a random distribution was found, indicating that these MBE-grown InGaN QWs do not require indium clusters for carrier localization. However, the APT data show steps in the QW interfaces, leading to well-width fluctuations, which may act to localize carriers. Additionally, the unexpected presence of a small amount (x = 0.005) of indium in a layer grown intentionally as GaN was revealed. Finally, the same statistical method applied to the QW was used to show that the indium distribution within a thick InGaN waveguide layer in the n-doped region did not show any deviation from randomness.

  11. Atomic-Scale Confinement of Resonant Optical Fields

    Science.gov (United States)

    Kern, Johannes; Großmann, Swen; Tarakina, Nadezda V.; Häckel, Tim; Emmerling, Monika; Kamp, Martin; Huang, Jer-Shing; Biagioni, Paolo; Prangsma, Jord C.; Hecht, Bert

    2012-11-01

    In the presence of matter there is no fundamental limit preventing confinement of visible light even down to atomic scales. Achieving such confinement and the corresponding intensity enhancement inevitably requires simultaneous control over atomic-scale details of material structures and over the optical modes that such structures support. By means of self-assembly we have obtained side-by-side aligned gold nanorod dimers with robust atomically-defined gaps reaching below 0.5 nm. The existence of atomically-confined light fields in these gaps is demonstrated by observing extreme Coulomb splitting of corresponding symmetric and anti-symmetric dimer eigenmodes of more than 800 meV in white-light scattering experiments. Our results open new perspectives for atomically-resolved spectroscopic imaging, deeply nonlinear optics, ultra-sensing, cavity optomechanics as well as for the realization of novel quantum-optical devices.

  12. Spectroscopy of cesium Rydberg atoms in strong radio-frequency fields

    CERN Document Server

    Jiao, Yuechun; Li, Jingkui; Raithel, Georg; Zhao, Jianming; Jia, Suotang

    2016-01-01

    We study Rydberg atoms modulated by strong radio-frequency (RF) fields with a frequency of 70 MHz. The Rydberg atoms are prepared in a room temperature cesium cell, and their level structure is probed using electromagnetically induced transparency (EIT). As the RF field increases from the weak- into the strong-field regime, the range of observed RF-induced phenomena progresses from AC level shifts through increasingly pronounced and numerous RF-modulation sidebands to complex state-mixing and level-crossings with high-l hydrogen-like states. Weak anharmonic admixtures in the RF field generate clearly visible modifications in the Rydberg-EIT spectra. A Floquet analysis is employed to model the Rydberg spectra, and good agreement with the experimental observations is found. Our results show that all-optical spectroscopy of Rydberg atoms in vapor cells can serve as an antenna-free, atom-based and calibration-free technique to measure and map RF electric fields and to analyze their higher-harmonic contents.

  13. Field testing the prototype BNL fan-atomized oil burner

    Energy Technology Data Exchange (ETDEWEB)

    McDonald, R.; Celebi, Y. [Brookhaven National Lab., Upton, NY (United States)

    1995-04-01

    BNL has developed a new oil burner design referred to as the Fan Atomized burner System. The primary objective of the field study was to evaluate and demonstrate the reliable operation of the Fan Atomized Burner. The secondary objective was to establish and validate the ability of a low firing rate burner (0.3-0.4 gph) to fully satisfy the heating and domestic hot water load demands of an average household in a climate zone with over 5,000 heating-degree-days. The field activity was also used to evaluate the practicality of side-wall venting with the Fan Atomized Burner with a low stack temperature (300F) and illustrate the potential for very high efficiency with an integrated heating system approach based on the Fan Atomized Burner.

  14. Atom Probe Tomography Characterization of the Solute Distributions in a Neutron-Irradiated and Annealed Pressure Vessel Steel Weld

    Energy Technology Data Exchange (ETDEWEB)

    Miller, M.K.

    2001-01-30

    A combined atom probe tomography and atom probe field ion microscopy study has been performed on a submerged arc weld irradiated to high fluence in the Heavy-Section Steel irradiation (HSSI) fifth irradiation series (Weld 73W). The composition of this weld is Fe - 0.27 at. % Cu, 1.58% Mn, 0.57% Ni, 0.34% MO, 0.27% Cr, 0.58% Si, 0.003% V, 0.45% C, 0.009% P, and 0.009% S. The material was examined after five conditions: after a typical stress relief treatment of 40 h at 607 C, after neutron irradiation to a fluence of 2 x 10{sup 23} n m{sup {minus}2} (E > 1 MeV), and after irradiation and isothermal anneals of 0.5, 1, and 168 h at 454 C. This report describes the matrix composition and the size, composition, and number density of the ultrafine copper-enriched precipitates that formed under neutron irradiation and the change in these parameters with post-irradiation annealing treatments.

  15. Dipolar relaxation of cold sodium atoms in a magnetic field

    CERN Document Server

    Zygelman, B

    2002-01-01

    A quantum mechanical close coupling theory of spin relaxation in the stretched hyperfine level of sodium is presented. We calculate the dipolar relaxation rate of magnetically trapped cold sodium atoms in the magnetic field. The influence of shape resonances and the anisotropy of the dipolar interaction on the collision dynamics are explored. We examine the sensitivity of the calculated cross sections on the choice of asymptotic atomic state basis.

  16. Periodic Orbit Theory for Rydberg Atoms in External Fields

    Science.gov (United States)

    Dando, P. A.; Monteiro, T. S.; Owen, S. M.

    1998-03-01

    Although hydrogen in external fields is a paradigm for the application of periodic orbits and the Gutzwiller trace formula to a real system, the trace formula has never been applied successfully to other Rydberg atoms. We show that spectral fluctuations of general Rydberg atoms are given with remarkable precision by the addition of diffractive terms. Previously unknown features in atomic spectra are exposed: there are new modulations that are neither periodic orbits nor combinations of periodic orbits; ``core shadowing'' generally decreases primitive periodic orbit amplitudes but can also lead to increases.

  17. Periodic Orbit Theory for Rydberg Atoms in External Fields

    CERN Document Server

    Dando, P A; Owen, S M

    1998-01-01

    Although hydrogen in external fields is a paradigm for the application of periodic orbits and the Gutzwiller trace formula to a real system, the trace formula has never been applied successfully to other Rydberg atoms. We show that spectral fluctuations of general Rydberg atoms are given with remarkable precision by the addition of diffractive terms. Previously unknown features in atomic spectra are exposed: there are new modulations that are neither periodic orbits nor combinations of periodic orbits; `core-shadowing' generally decreases primitive periodic orbit amplitudes but can also lead to increases.

  18. Probing magnetic fields with multi-frequency polarized synchrotron emission

    CERN Document Server

    Thiebaut, Jerome; Pichon, Christophe; Thiébaut, Eric

    2009-01-01

    We investigate the problem of probing the local spatial structure of the magnetic field of the interstellar medium using multi-frequency polarized maps of the synchrotron emission at radio wavelengths. We focus in this paper on the three-dimensional reconstruction of the largest scales of the magnetic field, relying on the internal depolarization (due to differential Faraday rotation) of the emitting medium as a function of electromagnetic frequency. We argue that multi-band spectroscopy in the radio wavelengths, developed in the context of high-redshift extragalactic HI lines, can be a very useful probe of the 3D magnetic field structure of our Galaxy when combined with a Maximum A Posteriori reconstruction technique. When starting from a fair approximation of the magnetic field, we are able to recover the true one by using a linearized version of the corresponding inverse problem. The spectral analysis of this problem allows us to specify the best sampling strategy in electromagnetic frequency and predicts ...

  19. The Wide-Field Imager for Solar Probe Plus (WISPR)

    Science.gov (United States)

    Vourlidas, Angelos; Howard, Russell A.; Plunkett, Simon P.; Korendyke, Clarence M.; Thernisien, Arnaud F. R.; Wang, Dennis; Rich, Nathan; Carter, Michael T.; Chua, Damien H.; Socker, Dennis G.; Linton, Mark G.; Morrill, Jeff S.; Lynch, Sean; Thurn, Adam; Van Duyne, Peter; Hagood, Robert; Clifford, Greg; Grey, Phares J.; Velli, Marco; Liewer, Paulett C.; Hall, Jeffrey R.; DeJong, Eric M.; Mikic, Zoran; Rochus, Pierre; Mazy, Emanuel; Bothmer, Volker; Rodmann, Jens

    2016-12-01

    The Wide-field Imager for Solar PRobe Plus (WISPR) is the sole imager aboard the Solar Probe Plus (SPP) mission scheduled for launch in 2018. SPP will be a unique mission designed to orbit as close as 7 million km (9.86 solar radii) from Sun center. WISPR employs a 95∘ radial by 58∘ transverse field of view to image the fine-scale structure of the solar corona, derive the 3D structure of the large-scale corona, and determine whether a dust-free zone exists near the Sun. WISPR is the smallest heliospheric imager to date yet it comprises two nested wide-field telescopes with large-format (2 K × 2 K) APS CMOS detectors to optimize the performance for their respective fields of view and to minimize the risk of dust damage, which may be considerable close to the Sun. The WISPR electronics are very flexible allowing the collection of individual images at cadences up to 1 second at perihelion or the summing of multiple images to increase the signal-to-noise when the spacecraft is further from the Sun. The dependency of the Thomson scattering emission of the corona on the imaging geometry dictates that WISPR will be very sensitive to the emission from plasma close to the spacecraft in contrast to the situation for imaging from Earth orbit. WISPR will be the first `local' imager providing a crucial link between the large-scale corona and the in-situ measurements.

  20. Atomic force microscope controlled topographical imaging and proximal probe thermal desorption/ionization mass spectrometry imaging.

    Science.gov (United States)

    Ovchinnikova, Olga S; Kjoller, Kevin; Hurst, Gregory B; Pelletier, Dale A; Van Berkel, Gary J

    2014-01-21

    This paper reports on the development of a hybrid atmospheric pressure atomic force microscopy/mass spectrometry imaging system utilizing nanothermal analysis probes for thermal desorption surface sampling with subsequent atmospheric pressure chemical ionization and mass analysis. The basic instrumental setup and the general operation of the system were discussed, and optimized performance metrics were presented. The ability to correlate topographic images of a surface with atomic force microscopy and a mass spectral chemical image of the same surface, utilizing the same probe without moving the sample from the system, was demonstrated. Co-registered mass spectral chemical images and atomic force microscopy topographical images were obtained from inked patterns on paper as well as from a living bacterial colony on an agar gel. Spatial resolution of the topography images based on pixel size (0.2 μm × 0.8 μm) was better than the resolution of the mass spectral images (2.5 μm × 2.0 μm), which were limited by current mass spectral data acquisition rate and system detection levels.

  1. NATO Advanced Study Institute on Atoms in Strong Fields

    CERN Document Server

    Clark, Charles; Nayfeh, Munir

    1990-01-01

    This book collects the lectures given at the NATO Advanced Study Institute on "Atoms in Strong Fields", which took place on the island of Kos, Greece, during the two weeks of October 9-21,1988. The designation "strong field" applies here to an external electromagnetic field that is sufficiently strong to cause highly nonlinear alterations in atomic or molecular struc­ ture and dynamics. The specific topics treated in this volume fall into two general cater­ gories, which are those for which strong field effects can be studied in detail in terrestrial laboratories: the dynamics of excited states in static or quasi-static electric and magnetic fields; and the interaction of atoms and molecules with intense laser radiation. In both areas there exist promising opportunities for research of a fundamental nature. An electric field of even a few volts per centimeter can be very strong on the atom­ ic scale, if it acts upon a weakly bound state. The study of Rydberg states with high reso­ lution laser spectroscop...

  2. Probing surface electric field noise with a single ion

    CERN Document Server

    Daniilidis, N; Bolloten, G; Ramm, M; Ransford, A; Ulin-Avila, E; Talukdar, I; Häffner, H

    2013-01-01

    We report room-temperature electric field noise measurements combined with in-situ surface characterization and cleaning of a microfabricated ion trap. We used a single-ion electric field noise sensor in combination with surface cleaning and analysis tools, to investigate the relationship between electric field noise from metal surfaces in vacuum and the composition of the surface. These experiments were performed in a novel setup that integrates ion trapping capabilities with surface analysis tools. We find that surface cleaning of an aluminum-copper surface significantly reduces the level of electric field noise, but the surface does not need to be atomically clean to show noise levels comparable to those of the best cryogenic traps. The post-cleaning noise levels are low enough to allow fault-tolerant trapped-ion quantum information processing on a microfabricated surface trap.

  3. Electron-atom scattering in a circularly polarized laser field

    CERN Document Server

    Cionga, Aurelia; Zloh, Gabriela; 10.1103/PhysRevA.61.063417

    2013-01-01

    We consider electron-atom scattering in a circularly polarized laser field at sufficiently high electron energies, permitting to describe the scattering process by the first order Born approximation. Assuming the radiation field has sufficiently moderate intensities, the laser-dressing of the hydrogen target atom in its ground state will be treated in second order perturbation theory. Within this approximation scheme, it is shown that the nonlinear differential cross sections of free-free transitions do neither depend on the {\\it dynamical phase} $\\phi$ of the radiative process nor on the {\\it helicity} of the circularly polarized laser light. Relations to the corresponding results for linear laser polarization are established.

  4. Ultrarelativistic quasiclassical wave functions in strong laser and atomic fields

    CERN Document Server

    Di Piazza, A

    2014-01-01

    The problem of an ultrarelativistic charge in the presence of an atomic and a plane-wave field is investigated in the quasiclassical regime by including exactly the effects of both background fields. Starting from the quasiclassical Green's function obtained in [Phys. Lett. B \\textbf{717}, 224 (2012)], the corresponding in- and out-wave functions are derived in the experimentally relevant case of the particle initially counterpropagating with respect to the plane wave. The knowledge of these electron wave functions opens the possibility of investigating a variety of problems in strong-field QED, where both the atomic field and the laser field are strong enough to be taken into account exactly from the beginning in the calculations.

  5. Atomic excitation and acceleration in strong laser fields

    Science.gov (United States)

    Zimmermann, H.; Eichmann, U.

    2016-10-01

    Atomic excitation in the tunneling regime of a strong-field laser-matter interaction has been recently observed. It is conveniently explained by the concept of frustrated tunneling ionization (FTI), which naturally evolves from the well-established tunneling picture followed by classical dynamics of the electron in the combined laser field and Coulomb field of the ionic core. Important predictions of the FTI model such as the n distribution of Rydberg states after strong-field excitation and the dependence on the laser polarization have been confirmed in experiments. The model also establishes a sound basis to understand strong-field acceleration of neutral atoms in strong laser fields. The experimental observation has become possible recently and initiated a variety of experiments such as atomic acceleration in an intense standing wave and the survival of Rydberg states in strong laser fields. Furthermore, the experimental investigations on strong-field dissociation of molecules, where neutral excited fragments after the Coulomb explosion of simple molecules have been observed, can be explained. In this review, we introduce the subject and give an overview over relevant experiments supplemented by new results.

  6. Classical-field model of the hydrogen atom

    Science.gov (United States)

    Rashkovskiy, Sergey A.

    2017-02-01

    It is shown that all of the basic properties of the hydrogen atom can be consistently described in terms of classical electrodynamics if instead of considering the electron to be a particle, we consider an electrically charged classical wave field—an "electron wave"—which is held by the electrostatic field of the proton. It is shown that quantum mechanics must be considered not as a theory of particles but as a classical field theory in the spirit of classical electrodynamics. In this case, we are not faced with difficulties in interpreting the results of the theory. In the framework of classical electrodynamics, all of the well-known regularities of the spontaneous emission of the hydrogen atom are obtained, which is usually derived in the framework of quantum electrodynamics. It is shown that there are no discrete states and discrete energy levels of the atom: the energy of the atom and its states change continuously. An explanation of the conventional corpuscular-statistical interpretation of atomic phenomena is given. It is shown that this explanation is only a misinterpretation of continuous deterministic processes. In the framework of classical electrodynamics, the nonlinear Schrödinger equation is obtained, which accounts for the inverse action of self-electromagnetic radiation of the electron wave and completely describes the spontaneous emissions of an atom.

  7. Correlation and contingency analysis of atom probe data: Diffusion-controlled dissolution of precipitates

    Energy Technology Data Exchange (ETDEWEB)

    Camus, E. (Hahn-Meitner-Institut Berlin GmbH (Germany)); Abromeit, C. (Hahn-Meitner-Institut Berlin GmbH (Germany))

    1994-05-01

    A statistical analysis of atom probe data is developed for evaluating the evolution of local composition fluctuations in concentrated alloys. The model allows the calculation of theoretical correlation and contingency coefficients for a presumed alloy microstructure taking into account the instrumental parameters, i.e. aperture size, block size and detector efficiency. A comparison of theoretical coefficients with those obtained from measured concentration profiles gives access to physically relevant parameters. The analysis is applied to the diffusion-controlled dissolution of spherical precipitates in the technical alloy Nimonic PE16 under ion irradiation. (orig.)

  8. Practical Issues for Atom Probe Tomography Analysis of III-Nitride Semiconductor Materials

    OpenAIRE

    2015-01-01

    This is the author accepted manuscript. The final version is available from Cambridge University Press via http://dx.doi.org/10.1017/S1431927615000422 Various practical issues affecting atom probe tomography (APT) analysis of III-nitride semiconductors have been studied as part of an investigation using a c-plane InAlN/GaN heterostructure. Specimen preparation was undertaken using a focused ion beam microscope with a mono-isotopic Ga source. This enabled the unambiguous observation of impl...

  9. Initial study on Z-phase strengthened 9-12% Cr steels by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Fang; Andren, Hans-Olof [Chalmers Univ. of Technology, Goeteborg (Sweden). Dept. of Applied Physics

    2010-07-01

    The microstructure of two different types of Z-phase strengthened experimental steels, CrNbN-based or CrTaN-based, was investigated. Both steels underwent aging at 650 C for relatively short period of time, 24 hours or 1005 hours. Atom probe tomography was used to study the chemical composition of the matrix and precipitates, and the size and number density of the small precipitates. Both steels contain Laves phase at prior austenite grain boundaries and martensitic lath boundaries. The CrTaN-based steel was found more promising due to its finer and more densely distributed precipitates after 1005 hour aging. (orig.)

  10. Influence of supersaturated carbon on the diffusion of Ni in ferrite determined by atom probe tomography

    KAUST Repository

    Kresse, T.

    2013-09-01

    In patented and cold-drawn pearlitic steel wires dissociation of cementite occurs during mechanical deformation. In this study the influence of the carbon decomposition on the diffusion of nickel in ferrite is investigated by means of atom probe tomography. In the temperature range 423-523 K we observed a much smaller activation energy of Ni diffusion than for self-diffusion in body-centered cubic iron, indicating an increased vacancy density owing to enhanced formation of vacancy-carbon complexes. © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  11. Probing spin-orbit-interaction-induced electron dynamics in the carbon atom by multiphoton ionization

    Science.gov (United States)

    Rey, H. F.; van der Hart, H. W.

    2014-09-01

    We use R-matrix theory with time dependence (RMT) to investigate multiphoton ionization of ground-state atomic carbon with initial orbital magnetic quantum number ML=0 and ML=1 at a laser wavelength of 390 nm and peak intensity of 1014W/cm2. Significant differences in ionization yield and ejected-electron momentum distribution are observed between the two values for ML. We use our theoretical results to model how the spin-orbit interaction affects electron emission along the laser polarization axis. Under the assumption that an initial C atom is prepared at zero time delay with ML=0, the dynamics with respect to time delay of an ionizing probe pulse modeled by using RMT theory is found to be in good agreement with available experimental data.

  12. Atom probe, AFM, and STM studies on vacuum-fired stainless steels

    Energy Technology Data Exchange (ETDEWEB)

    Stupnik, A. [ACC Austria GmbH, 8280 Fuerstenfeld (Austria); Frank, P. [Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz (Austria); Leisch, M., E-mail: m.leisch@tugraz.at [Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz (Austria)

    2009-04-15

    The surface morphology of grades 304L and 316LN stainless steels, after low-temperature bake-out process and vacuum annealing, has been studied by atomic force microscopy (AFM) and scanning tunnelling microscopy (STM). The local elemental composition on the surface before and after thermal treatment has been investigated by atom probe (AP) depth profiling measurements. After vacuum annealing, AFM and STM show significant changes in the surface structure and topology. Recrystallization and surface reconstruction is less pronounced on the 316LN stainless steel. AP depth profiling analyses result in noticeable nickel enrichment on the surface of grade 304L samples. Since hydrogen recombination is almost controlled by surface structure and composition, a strong influence on the outgassing behaviour by the particular surface microstructure can be deduced.

  13. Atom probe, AFM, and STM studies on vacuum-fired stainless steels.

    Science.gov (United States)

    Stupnik, A; Frank, P; Leisch, M

    2009-04-01

    The surface morphology of grades 304L and 316LN stainless steels, after low-temperature bake-out process and vacuum annealing, has been studied by atomic force microscopy (AFM) and scanning tunnelling microscopy (STM). The local elemental composition on the surface before and after thermal treatment has been investigated by atom probe (AP) depth profiling measurements. After vacuum annealing, AFM and STM show significant changes in the surface structure and topology. Recrystallization and surface reconstruction is less pronounced on the 316LN stainless steel. AP depth profiling analyses result in noticeable nickel enrichment on the surface of grade 304L samples. Since hydrogen recombination is almost controlled by surface structure and composition, a strong influence on the outgassing behaviour by the particular surface microstructure can be deduced.

  14. Extracting features buried within high density atom probe point cloud data through simplicial homology.

    Science.gov (United States)

    Srinivasan, Srikant; Kaluskar, Kaustubh; Broderick, Scott; Rajan, Krishna

    2015-12-01

    Feature extraction from Atom Probe Tomography (APT) data is usually performed by repeatedly delineating iso-concentration surfaces of a chemical component of the sample material at different values of concentration threshold, until the user visually determines a satisfactory result in line with prior knowledge. However, this approach allows for important features, buried within the sample, to be visually obscured by the high density and volume (~10(7) atoms) of APT data. This work provides a data driven methodology to objectively determine the appropriate concentration threshold for classifying different phases, such as precipitates, by mapping the topology of the APT data set using a concept from algebraic topology termed persistent simplicial homology. A case study of Sc precipitates in an Al-Mg-Sc alloy is presented demonstrating the power of this technique to capture features, such as precise demarcation of Sc clusters and Al segregation at the cluster boundaries, not easily available by routine visual adjustment.

  15. Phase dependent excitation of Rydberg atoms in non-zero average fields

    Science.gov (United States)

    Magnuson, Eric; Carrat, Vincent; Gallagher, Tom

    2016-05-01

    The final energy of an electron excited to a high lying Rydberg state in the presence of a microwave (MW) field shows a dependence on the phase of the field at which the excitation occurs. This phase dependence is comparable to that seen in strong field experiments using attosecond pulses to probe systems perturbed by intense infrared (IR) fields. In zero average field, final energies exhibit a phase dependence at twice the frequency of the MW field. We show a phase dependence at the same frequency as the MW field emerges in the presence of a non-zero average field, parallel to the MW polarization. To isolate phase dependence at the MW frequency, we amplitude modulate the IR excitation laser and phase lock this modulation to the MW field. Li atoms are excited to states near the ionization limit in the presence of a MW field, and bound Rydberg states (n>150) are detected. In an applied average field, we observe modulation of the Rydberg signal at the MW frequency. This modulation vanishes as the average field is zeroed, but persists even in fields large enough to ionize most of the population. We compare these results to symmetry arguments and a model of classical Rydberg orbits. An experiment to determine the absolute phase of the modulation relative the MW field is discussed. This work is supported by the US Department of Energy.

  16. A versatile variable field module for Asylum Cypher scanning probe system

    Science.gov (United States)

    Liu, Hongxue; Comes, Ryan; Lu, Jiwei; Wolf, Stuart; Hodgson, Jim; Rutgers, Maarten

    2013-03-01

    Atomic force microscopy (AFM) has become one of the most widely used techniques for measuring and manipulating various characteristics of materials at the nanoscale. However, there are very limited option for the characterization of field dependence properties. In this work, we demonstrate a versatile variable field module (VFM) with magnetic field up to 1800 Oe for the Asylum Research Cypher system. The magnetic field is changed by adjusting the distance between a rare earth magnet and the AFM probe. A built-in Hall sensor makes it possible to perform in-situ measurements of the field. Rotating the magnet makes it possible to do angular field dependent measurements. The capability of the VFM system is demonstrated by degaussing a floppy disk media with increasing magnetic field. The written bits are erased at about 800 Oe. Angular dependence measurements clearly show the evolution of magnetic domain structures. A completely reversible magnetic force microscopy (MFM) phase contrast is observed when the magnetic field is rotated by 180°. Further demonstration of successful magnetic switching of CoFe2O4 pillars in CoFe2O4-BiFeO3 nanocomposites will be presented and field dependent MFM and piezoresponse force microscopy (PFM) will be discussed. The work at University of Virginia was supported by DARPA under contract no. HR-0011-10-1-0072.

  17. Coaxial atomic force microscope probes for dielectrophoresis of DNA under different buffer conditions

    Science.gov (United States)

    Tao, Yinglei; Kumar Wickramasinghe, H.

    2017-02-01

    We demonstrate a coaxial AFM nanoprobe device for dielectrophoretic (DEP) trapping of DNA molecules in Tris-EDTA (TE) and phosphate-buffered saline (PBS) buffers. The DEP properties of 20 nm polystyrene beads were studied with coaxial probes in media with different conductivities. Due to the special geometry of our DEP probe device, sufficiently high electric fields were generated at the probe end to focus DNA molecules with positive DEP. DEP trapping for both polystyrene beads and DNA molecules was quantitatively analyzed over the frequency range from 100 kHz to 50 MHz and compared with the Clausius-Mossotti theory. Finally, we discussed the negative effect of medium salinity during DEP trapping.

  18. Electron Scattering by Ar Atoms in a Laser Field

    Institute of Scientific and Technical Information of China (English)

    ZHANG Sheng-Hai; QIAN Xing-Zhong; JIANG Yu-Hai; SUN Jin-Feng

    2000-01-01

    The differentialcross sections of electron-Ar atom scattering for free-free transition with one and two photons absorption in the presence of CO2 laser field is obtained by the second Born approximation, the direction of laser polarization being perpendicular to the change of electron momentum. Compared with the more recent available experimental data, the present results are very good.

  19. Atomic Beam Laser Spectrometer for In-field Isotopic Analysis

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Alonso [Los Alamos National Lab. (LANL), Los Alamos, NM (United States). Actinide Analytical Chemistry Group

    2016-06-22

    This is a powerpoint presentation for the DTRA quarterly program review that goes into detail about the atomic beam laser spectrometer for in-field isotopic analysis. The project goals are the following: analysis of post-detonation debris, determination of U and Pu isotopic composition, and fieldable prototype: < 2ft3, < 1000W.

  20. Sodium atom in strong magnetic fields: a pseudospectral approach

    Institute of Scientific and Technical Information of China (English)

    邹远川; 张战军; 乔豪学

    2003-01-01

    Energies and wavefunctions of low-lying states and Rydberg states for the sodium atom in uniform magnetic fields varying from 0 to 105T are calculated using a pseudospectral approach with a model potential in spherical coordinates.The energies are comparable with experimental results as well as those obtained by other calculations. The spectra of oscillator strength are worked out. The evolution of them with the magnetic field is shown.

  1. Dynamical localization: Hydrogen atoms in magnetic and microwave fields

    Energy Technology Data Exchange (ETDEWEB)

    Benvenuto, F.; Casati, G. [Dipartimento di Fisica dellUniversita, Via Castelnuovo 7, 22100 Como (Italy); Shepelyansky, D.L. [Laboratoire de Physique Quantique, UMR C5626 du CNRS, Universite Paul Sabatier, 31062, Toulouse (France)

    1997-03-01

    We show that dynamical localization for excited hydrogen atoms in magnetic and microwave fields takes place at quite low microwave frequency ({omega}n{sup 3}{lt}1). Estimates of the localization length are given for different parameter regimes, showing that the quantum delocalization border drops significantly as compared to the case of zero magnetic field. This opens up broad possibilities for laboratory investigations. {copyright} {ital 1997} {ital The American Physical Society}

  2. Quantitative analysis of carbon in cementite using pulsed laser atom probe

    Energy Technology Data Exchange (ETDEWEB)

    Kitaguchi, H.S., E-mail: hiroto.kitaguchi@twi.co.uk; Lozano-Perez, S.; Moody, M.P.

    2014-12-15

    Carbon quantification and the standardisation in a pure cementite were conducted using pulsed-laser atom probe tomography (APT). The results were analysed to investigate a dependence on three distinct experimental parameters; the laser pulse energy, the cryogenic specimen temperature and the laser pulse frequency. All the measurements returned an apparent carbon content of 25.0±1.0 at%. Carbon content measurements showed no clear dependence on the cryogenic temperature or the laser pulse frequency. However, the results did demonstrate a strong correlation with the laser pulse energy. For lower laser pulse energies, the analysis returned carbon contents higher than the stoichiometric ratio. It was suggested that this effect is due to pile up of {sup 56}Fe{sup ++} at the detector and as a consequence there is a systematic preferential loss of these ions throughout the course of the experiment. Conversely, in experiments utilising higher laser pulse energies, it was found that the carbon contents were smaller than the stoichiometric ratio. In these experiments an increasing fraction of the larger carbon molecular ions (e.g., C{sub 5} ions) were detected as part of a multiple detection events, which could affect the quantification measurements. - Highlights: • This paper describes carbon quantifications in cementite. • Laser pulsed atom probe tomography successfully quantified the carbon content. • A unique background subtraction method was applied. • Deviations from the stoichiometry were discussed.

  3. Atomic jet with ionization detection for laser spectroscopy of Rydberg atoms under collisions and fields

    Science.gov (United States)

    Philip, G.

    2008-03-01

    An efficient atomic jet setup offering many unprecedented advantages over a conventional heat pipe setup used in multi-photon spectroscopy, mainly of alkaline-earth metals, has been constructed by a scheme in which the sample material is encapsulated in a disposable cartridge oven located inside a thermally stabilised heat-pipe and is made to effuse in to a row of atomic beams merging to form a jet target. This novel scheme combines the advantages of both high density atomic beam with convenient geometry for orthogonal excitation and high sensitive ionisation detection capabilities of thermionic diodes, besides eliminating several problems inherent in the usual heat-pipe operation. Out of various designs, typical results are presented for a linear heat-pipe with vertical atomic jet used in two-photon spectroscopy of highly excited states of Sr I. Controlled excitations of both Rydberg and non-Rydberg states, which cannot otherwise be accessed from the ground state due to parity and spectroscopic selection rules, have been achieved by employing a weak electric field complimented by collisions. The atomic jet setup is also found very useful for the study of collisional broadening and shift of excited states and time evolution of Rydberg atoms.

  4. Quantum field entropy of the system with interaction between moving Bell-state atoms and coherent light field

    Institute of Scientific and Technical Information of China (English)

    ZHANG Cai-hua; Sachuerfu; Gerile

    2011-01-01

    The field entropy of the system with two moving atoms interacting with the coherent state is investigated by means of the full quantum theory.Under the different initial states with two atoms,the influences of the light field intensity and the atomic motion on the field entropy are discussed.The results indicate that the motion of the atoms leads to strict periodicity in the field entropy evolution.When the two atoms are in the Bell state initially,the system is in a completely disentangled state.For the atoms initially at other Bell states,the field periodically entangles with the atoms.

  5. Customized atomic force microscopy probe by focused-ion-beam-assisted tip transfer

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Andrew; Butte, Manish J., E-mail: manish.butte@stanford.edu [Department of Pediatrics, Division of Immunology, Allergy and Rheumatology, Stanford University, Stanford, California 94305 (United States)

    2014-08-04

    We present a technique for transferring separately fabricated tips onto tipless atomic force microscopy (AFM) cantilevers, performed using focused ion beam-assisted nanomanipulation. This method addresses the need in scanning probe microscopy for certain tip geometries that cannot be achieved by conventional lithography. For example, in probing complex layered materials or tall biological cells using AFM, a tall tip with a high-aspect-ratio is required to avoid artifacts caused by collisions of the tip's sides with the material being probed. We show experimentally that tall (18 μm) cantilever tips fabricated by this approach reduce squeeze-film damping, which fits predictions from hydrodynamic theory, and results in an increased quality factor (Q) of the fundamental flexural mode. We demonstrate that a customized tip's well-defined geometry, tall tip height, and aspect ratio enable improved measurement of elastic moduli by allowing access to low-laying portions of tall cells (T lymphocytes). This technique can be generally used to attach tips to any micromechanical device when conventional lithography of tips cannot be accomplished.

  6. Field ionization of free helium atoms: Correlation between the kinetic energy of ionized atoms and probability of their field ionization

    Energy Technology Data Exchange (ETDEWEB)

    Piskur, J.; Borg, L. [Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz (Austria); Stupnik, A.; Leisch, M. [Institute of Solid State Physics, Graz University of Technology, Petersgasse 16, 8010 Graz (Austria); Ernst, W.E. [Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz (Austria); Holst, B. [Institute of Experimental Physics, Graz University of Technology, Petersgasse 16, 8010 Graz (Austria)], E-mail: bodil@cantab.net

    2008-05-15

    In this paper the correlation between the kinetic energy of helium atoms and the probability of field ionization is investigated by exploiting the narrow velocity distribution of supersonic molecular beams. Field ionization measurements were carried out on supersonic helium beams at 298 K and 95 K corresponding to energies of about 65 meV and 20 meV, respectively, for the individual atoms. The field ionization was performed with a tungsten tip, radius of curvature 12 nm, kept at room temperature. The ionization probability was found to increase by about a factor 10 when the beam was cooled from 298 K to 95 K. The results presented in this paper are of importance for improving the understanding of field ionization and for the development of a new detector for helium and other molecular beams.

  7. Field ionization of free helium atoms: Correlation between the kinetic energy of ionized atoms and probability of their field ionization

    Science.gov (United States)

    Piskur, J.; Borg, L.; Stupnik, A.; Leisch, M.; Ernst, W. E.; Holst, B.

    2008-05-01

    In this paper the correlation between the kinetic energy of helium atoms and the probability of field ionization is investigated by exploiting the narrow velocity distribution of supersonic molecular beams. Field ionization measurements were carried out on supersonic helium beams at 298 K and 95 K corresponding to energies of about 65 meV and 20 meV, respectively, for the individual atoms. The field ionization was performed with a tungsten tip, radius of curvature 12 nm, kept at room temperature. The ionization probability was found to increase by about a factor 10 when the beam was cooled from 298 K to 95 K. The results presented in this paper are of importance for improving the understanding of field ionization and for the development of a new detector for helium and other molecular beams.

  8. Guiding Neutral Atoms with Two Current-Carrying Wires and a Vertical Bias Field on the Atom Chip

    Institute of Scientific and Technical Information of China (English)

    KE Min; YAN Bo; LI Xiao-Lin; WANG Yu-Zhu

    2008-01-01

    @@ We demonstrate the guiding of neutral atoms with two parallel microfabricated current-carrying wires on the atom chip and a verticai magnetic bias field.The atoms are guided along a magnetic field minimum parallel to the current-carrying wires and confined in the other two directions.We describe in detail how the precooled atoms are efficiently loaded into the two-wire guide.

  9. Recurrence spectra of He atoms in strong external fields

    Institute of Scientific and Technical Information of China (English)

    LIN Shenglu; LI Hongyun; WANG Dehua; ZHAO Wenli; GAO Feng

    2004-01-01

    By employing a model potential including the electron exchange energy, we extend the semiclassical closed orbit theory to study the multielectron atoms. Using special region-splitting consistent and iterative method, we figure out the closed orbits in the corresponding classical system and calculate the recurrence spectra of triplet helium atoms in parallel electric and magnetic fields at scaled energy ε = -0.03, n≈40, m = 0.The core-scattering effects have been taken into account, which lead to more peaks in the spectra. It has also been confirmed by means of the direct comparison between the spectral portrait in such a plot and those of hydrogen case. In order to compare the theoretic results with experiment, we investigate the closed orbits and recurrence spectra of helium atoms for the similar exchange potential but applied only by single electric field at scaled energy s= -2.7 case. The spectra are in good agreement with the experimental observation. We conclude that our model is correct and it is necessary to consider the exchange effect for determining the photoabsorption spectra of multielectron atoms in strong external fields.

  10. Adsorbate Electric Fields on a Cryogenic Atom Chip

    CERN Document Server

    Chan, K S; Hufnagel, C; Dumke, R

    2013-01-01

    We investigate the behaviour of electric fields originating from adsorbates deposited on a cryogenic atom chip as it is cooled from room temperature to cryogenic temperature. Using Rydberg electromagnetically induced transparency we measure the field strength versus distance from a 1 mm square of YBCO patterned onto a YSZ chip substrate. We find a localized and stable dipole field at room temperature and attribute it to a saturated layer of chemically adsorbed rubidium atoms on the YBCO. As the chip is cooled towards 83 K we observe a change in sign of the electric field as well as a transition from a localized to a delocalized dipole density. We relate these changes to the onset of physisorption on the chip surface when the van der Waals attraction overcomes the thermal desorption mechanisms. Our findings suggest that, through careful selection of substrate materials, it may be possible to reduce the electric fields caused by atomic adsorption on chips, opening up experiments to controlled Rydberg-surface co...

  11. Nonlocality and purity in atom-field coupling system

    Institute of Scientific and Technical Information of China (English)

    Cai Xin; Huang Guang-Ming; Li Gao-Xiang

    2005-01-01

    The effects of initial field state and thermal environment on quantum nonlocality and linear entropy in an atomfield coupling system are investigated. We found that if the cavity is lossless and the reservoir is in vacuum, the atom-field state can exhibit quantum nonlocality periodically and the linear entropies of the atom and the field also oscillate periodically with a period the same as that of quantum nonlocality. And if the cavity dissipation is very weak and the average photon number of the reservoir is very small, the quantum nonlocality will be lost and the linear entropies of the atom and the field oscillate with a decreasing amplitude. The rapidity of the loss of the quantum nonlocality depends on the amplitude of the initial squeezed coherent state, the cavity damping constant κ and the average photon number N of the thermal reservoir. The stronger the field and the larger the constant κ and the average photon number N could be, the more rapidly the nonlocality decreases.

  12. Magic frequencies in atom-light interaction for precision probing of the density matrix

    CERN Document Server

    Givon, Menachem; Waxman, Amir; David, Tal; Groswasser, David; Japha, Yonathan; Folman, Ron

    2013-01-01

    We analyze theoretically and experimentally the existence of a {\\it magic frequency} for which the absorption of a linearly polarized light beam by vapor alkali atoms is independent of the population distribution among the Zeeman sub-levels and the angle between the beam and a magnetic field. The phenomenon originates from a peculiar cancelation of the contributions of higher moments of the atomic density matrix, and is described using the Wigner-Eckart theorem and inherent properties of Clebsch-Gordan coefficients. One important application is the robust measurement of the hyperfine population.

  13. Influence of atomic motion on the population and dipole squeezing of a cascade three-level atom in cavity field

    Institute of Scientific and Technical Information of China (English)

    Zhu Ai-Dong; Zhang Shou

    2004-01-01

    The dynamical property of a cascade three-level atom is investigated in the condition of atomic motion. The influence of atomic motion on the population and dipole squeezing is discussed. The results show that atomic motion makes the amplitude of atomic population be steady and increasing the parameter ep which denotes the atomic motion and the structure of field mode can shorten the period of collapse-revivals. By choosing an appropriate paramenter ep, we can obtain a dipole squeezed atom of long standing.

  14. Real-Time Near-Field Terahertz Imaging with Atomic Optical Fluorescence

    CERN Document Server

    Wade, Christopher G; de Melo, Natalia R; Kondo, Jorge M; Adams, Charles S; Weatherill, Kevin J

    2016-01-01

    Terahertz (THz) near-field imaging is a flourishing discipline [1], with applications from fundamental studies of beam propagation [2,3] to the characterisation of metameterials [4,5] and waveguides [6,7]. Beating the diffraction limit typically involves rastering structures or detectors with length scale shorter than the radiation wavelength; in the THz domain this has been achieved using a number of techniques including scattering tips [8,9] and apertures [10]. Alternatively, mapping THz fields onto an optical wavelength and imaging the visible light removes the requirement for scanning a local probe, speeding up image collection times [11,12]. Here we report THz to optical conversion using a gas of highly excited `Rydberg' atoms. By collecting THz-induced optical fluorescence we demonstrate a real-time image of a THz standing wave and we use well-known atomic properties to calibrate the THz field strength. The mono-atomic gas does not distort the THz field and offers the potential to immerse structures wit...

  15. Characterization of grain boundaries in Cu(In,Ga)Se{sub 2} by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Schwarz, Torsten; Cojocaru-Miredin, Oana; Choi, Pyuck-Pa; Raabe, Dierk [Max-Planck Institute for Iron Research GmbH, Duesseldorf (Germany); Wuerz, Roland [Zentrum fuer Sonnenenergie- und Wasserstoff-Forschung Baden-Wuerttemberg (ZSW), Stuttgart (Germany)

    2012-07-01

    Solar cells based on the compound semiconductor Cu(In,Ga)Se{sub 2} (CIGS) as absorber material exhibit the highest efficiency among all thin-film solar cells. This is surprising high in view of the polycrystalline defect-rich structure of the CIGS absorber films. The high efficiency has been commonly ascribed to the diffusion of alkali metal atoms from the soda-lime glass substrate into the CIGS layer, which can render the grain boundaries (GB) electrically inactive. However, the exact mechanisms of how these impurities enhance the cell efficiency are yet to be clarified. As a step towards a better understanding of CIGS solar cells, we have analyzed the composition of solar-grade CIGS layers at the atomic-scale by using pulsed laser Atom Probe Tomography (APT). To perform APT analyses on selected GBs site-specific sample preparation was carried out using the Focused Ion Beam lift-out technique. In addition, Electron Back Scattered Diffraction was performed to characterize the structure and misorientation of selected GBs. Using APT, segregation of impurities at the GBs was directly observed. APT data of various types of GBs are presented and discussed with respect to the possible effects on the cell efficiency.

  16. Microwave field measurement via Rabi resonances in Cs atoms

    CERN Document Server

    Sun, Fuyu; Bai, Qingsong; Huang, Xianhe; Ma, Jie; Li, Xiaofeng

    2016-01-01

    We present a technique for measuring microwave (MW) field based on Rabi resonances induced by the interaction of atoms with a phase-modulated MW field. A theoretical model of field measurement is used to calculate Rabi frequency. Single-peak feature of the measurement model makes the technique a valuable tool for simple and fast field measurement. As an example, we use the technique to determine the MW field strength inside a Cs vapor cell in the X-band rectangular cavity for applied power in the range of -21 dBm to 20 dBm. The results show that this proposed technique is capable for detecting the field over a broad dynamical range.

  17. Atom probe study of Cu-poor to Cu-rich transition during Cu(In,Ga)Se2 growth

    Science.gov (United States)

    Couzinie-Devy, F.; Cadel, E.; Barreau, N.; Arzel, L.; Pareige, P.

    2011-12-01

    Atomic scale chemistry of polycrystalline Cu(In,Ga)Se2 (CIGSe) thin film has been characterized at key points of the 3-stage process using atom probe tomography. 3D atom distributions have been reconstructed when the layer is Cu-poor ([Cu]/([Ga] + [In]) 1), and at the end of the process. Particular attention has been devoted to grain boundary composition and Na atomic distribution within the CIGSe layer. Significant variation of composition is highlighted during the growing process, providing fundamental information helping the understanding of high efficiency CIGSe formation.

  18. THEORETICAL ANALYSIS AND EXPERIMENTAL STUDY OF CARBON NANOTUBE PROBE AND CONVENTIONAL ATOMIC FORCE MICROSCOPY PROBE ON SURFACE ROUGHNESS

    Institute of Scientific and Technical Information of China (English)

    WANG Jinghe; WANG Hongxiang; XU Zongwei; DONG Shen; WANG Shiqian; ZHANG Huali

    2008-01-01

    In this paper, three different tips are employed, i.e., the carbon nanotube tip, monocrystalline silicon tip and silicon nitride tip. Resorting to atomic force microscope (AFM), they are used for measuring the surface roughness of indium tin oxide (ITO) film and the immunoglobulin G (IgG) proteins within the scanning area of 10 μm×10 μm and 0.5 μm×0.5 μm, respectively. Subsequently, the scanned surface of the ITO film and IgG proteins are analyzed by using fractal dimension. The results show that the fractal dimension measured by carbon nanotube tip is biggest with the highest frequency components and the most microscopic information. Therefore, the carbon nanotube tip is the ideal measuring tool for measuring super-smooth surface, which will play a more and more important role in the high-resolution imaging field.

  19. Atomic parity violation in one single trapped and laser cooled radium ion: a probe of electroweak running

    Energy Technology Data Exchange (ETDEWEB)

    Giri, G.S.; Boell, O.; Jungmann, K.; Sahoo, B.K.; Timmermans, R.G.E.; Versolato, O.O.; Wansbeek, L.W.; Willmann, L. [KVI, University of Groningen (Netherlands)

    2009-07-01

    One single-trapped and laser cooled radium ion is an ideal candidate to investigate atomic parity non-conservation (APNC). APNC can serve as a low energy test of the Standard Model of particle physics. We aim for a precision measurement of the electroweak mixing angle, by probing the differential light shift of the 7S and 6D Zeeman sublevels. This shift is caused by the interaction of the ion with an off-resonant laser light field. With precision RF spectroscopy and subsequent electron shelving, the differential splitting can be determined to sub-Hertz accuracy. Recent calculations show that Ra{sup +} is a superior candidate for probing APNC. With an almost identical set-up and using the electron shelving technique, ultra-narrow transitions in this ion can be exploited for an all optical, high stability frequency standard clock. We have succeeded in the production and subsequent slowing down of radium isotopes around {sup 213}Ra. Further progress has been made in the development of ion traps and the necessary high precision optical laboratory. Laser spectroscopy of Ra{sup +} and the first ever trapping of this particle are being prepared.

  20. Hierarchical atom type definitions and extensible all-atom force fields.

    Science.gov (United States)

    Jin, Zhao; Yang, Chunwei; Cao, Fenglei; Li, Feng; Jing, Zhifeng; Chen, Long; Shen, Zhe; Xin, Liang; Tong, Sijia; Sun, Huai

    2016-03-15

    The extensibility of force field is a key to solve the missing parameter problem commonly found in force field applications. The extensibility of conventional force fields is traditionally managed in the parameterization procedure, which becomes impractical as the coverage of the force field increases above a threshold. A hierarchical atom-type definition (HAD) scheme is proposed to make extensible atom type definitions, which ensures that the force field developed based on the definitions are extensible. To demonstrate how HAD works and to prepare a foundation for future developments, two general force fields based on AMBER and DFF functional forms are parameterized for common organic molecules. The force field parameters are derived from the same set of quantum mechanical data and experimental liquid data using an automated parameterization tool, and validated by calculating molecular and liquid properties. The hydration free energies are calculated successfully by introducing a polarization scaling factor to the dispersion term between the solvent and solute molecules. © 2015 Wiley Periodicals, Inc.

  1. Probing strong-field general relativity near black holes

    CERN Document Server

    CERN. Geneva; Alvarez-Gaumé, Luís

    2005-01-01

    Nature has sprinkled black holes of various sizes throughout the universe, from stellar mass black holes in X-ray sources to supermassive black holes of billions of solar masses in quasars. Astronomers today are probing the spacetime near black holes using X-rays, and gravitational waves will open a different view in the near future. These tools give us an unprecedented opportunity to test ultra-strong-field general relativity, including the fundamental theorem of the uniqueness of the Kerr metric and Roger Penrose's cosmic censorship conjecture. Already, fascinating studies of spectral lines are showing the extreme gravitational lensing effects near black holes and allowing crude measurements of black hole spin. When the ESA-NASA gravitational wave detector LISA begins its observations in about 10 years, it will make measurements of dynamical spacetimes near black holes with an accuracy greater even than that which theoreticians can reach with their computations today. Most importantly, when gravitational wa...

  2. Probing N=2 superconformal field theories with localization

    CERN Document Server

    Fiol, Bartomeu; Torrents, Genis

    2015-01-01

    We use supersymmetric localization to study probes of four dimensional Lagrangian N=2 superconformal field theories. We first derive a unique equation for the eigenvalue density of these theories. We observe that these theories have a Wigner eigenvalue density precisely when they satisfy a necessary condition for having a holographic dual with a sensible higher-derivative expansion. We then compute in the saddle-point approximation the vacuum expectation value of 1/2-BPS circular Wilson loops, and the two-point functions of these Wilson loops with the Lagrangian density and with the stress-energy tensor. This last computation also provides the corresponding Bremsstrahlung functions and entanglement entropies. As expected, whenever a finite fraction of the matter is in the fundamental representation, the results are drastically different from those of N=4 supersymmetric Yang-Mills theory.

  3. Entanglement swapping between atom and cavity and generation of entangled state of cavity fields

    Institute of Scientific and Technical Information of China (English)

    Chen Ai-Xi; Deng Li

    2007-01-01

    This paper proposes a scheme where entanglement swapping between atom and cavity can be realized. A-type three-level atoms interacting resonantly with cavity field are considered. By detecting atom and cavity field, it realizes entanglement swapping between atom and cavity. It uses the technique of entanglement swapping to generate an entangled state of two cavity fields by measuring on atoms. It discusses the experimental feasibility of the proposed scheme and application of entangled state of cavity fields.

  4. Strong-Field Ionization of Laser Cooled Li Atoms

    Science.gov (United States)

    Sharma, Sachin; Romans, Kevin; Fischer, Daniel

    2016-05-01

    Recently, our understanding of few-body effects has been substantially boosted by the development of intense femto- and attosecond laser sources. Observing the momenta of the fragments of atoms and molecules ionized in these strong fields provided new and before inconceivable insights in molecular and electronic dynamics. Here, we report on a new experiment, where the target atoms (6 Li) are laser cooled and trapped using a magneto optical trap (MOT). Momentum vectors of the target fragments will be measured using a reaction microscope (ReMi). The exclusivity of this setup is a combination of MOT and ReMi, thus dubbed as MOTReMi. Here, the advantages over standard COLTRIMS systems are multifold: Firstly, an unprecedented recoil ion momentum resolution can be achieved, as the target can be prepared at significantly lower temperatures. Second, the atoms can be optically prepared in the ground or in polarized excited states. In a first experimental campaign, studies on single ionization of laser excited and polarized Lithium atoms will be performed with circularly polarized light. This experiment can provide insight into the helicity-dependence of the ionization dynamics as the differences among co- and counter rotating electron and laser field, if any, can be investigated.

  5. Detection of slow atoms confined in a Cesium vapor cell by spatially separated pump and probe laser beams

    CERN Document Server

    Todorov, Petko; Maurin, Isabelle; Saltiel, Solomon; Bloch, Daniel

    2013-01-01

    The velocity distribution of atoms in a thermal gas is usually described through a Maxwell-Boltzman distribution of energy, and assumes isotropy. As a consequence, the probability for an atom to leave the surface under an azimuth angle {\\theta} should evolve as cos {\\theta}, in spite of the fact that there is no microscopic basis to justify such a law. The contribution of atoms moving at a grazing incidence towards or from the surface, i.e. atoms with a small normal velocity, here called "slow" atoms, reveals essential in the development of spectroscopic methods probing a dilute atomic vapor in the vicinity of a surface, enabling a sub-Doppler resolution under a normal incidence irradiation. The probability for such "slow" atoms may be reduced by surface roughness and atom-surface interaction. Here, we describe a method to observe and to count these slow atoms relying on a mechanical discrimination, through spatially separated pump and probe beams. We also report on our experimental progresses toward such a g...

  6. The dynamic properties of the two-level entangled atom in an optical field

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The interaction of an optical field and one of the entangled atoms is analyzed in detail in this paper. Furthermore, the dynamic properties of the two-level entangled atom are manifested. The properties of the action are dependent on the initial state of the atom. After detecting the atom out of the field, we can obtain the state of the other atom moving in the field. It is shown that the state of the atom out of the field influences the dynamic properties of the atom in the field.

  7. Influence of the virtual photon field on the squeezing properties of an atom laser

    Institute of Scientific and Technical Information of China (English)

    Zhao Jian-Gang; Sun Chang-Yong; Wen Ling-Hua; Liang Bao-Long

    2009-01-01

    This paper investigates the squeezing properties of an atom laser without rotating-wave approximation in the system of a binomial states field interacting with a two-level atomic Bose-Einstein condensate. It discusses the influences of atomic eigenfrequency, the interaction intensity between the optical field and atoms, parameter of the binomial states field and virtual photon field on the squeezing properties. The results show that two quadrature components of an atom laser can be squeezed periodically. The duration and the degree of squeezing an atom laser have something to do with the atomic eigenfrequency and the parameter of the binomial states field, respectively. The collapse and revival frequency of atom laser fluctuation depends on the interaction intensity between the optical field and atoms. The effect of the virtual photon field deepens the depth of squeezing an atom laser.

  8. Extended virtual detector theory for strong-field atomic ionization.

    Science.gov (United States)

    Wang, Xu; Tian, Justin; Eberly, J H

    2013-06-14

    For time-dependent strong-field atomic ionization a new theoretical approach is described that combines the numerical time-dependent Schrödinger equation (TDSE) and the numerical time-dependent Newtonian equation (TDNE). This approach keeps both the accuracy of quantum calculations and the speed of classical calculations. It does not use approximate tunneling formulas. It is applied to a recent experimental result, and we show its successful comparison to extensive TDSE calculations made under exactly the same conditions.

  9. Field correlations and effective two level atom-cavity systems

    CERN Document Server

    Rebic, S; Tan, S M

    2004-01-01

    We analyse the properties of the second order correlation functions of the electromagnetic field in atom-cavity systems that approximate two-level systems. It is shown that a recently-developed polariton formalism can be used to account for all the properties of the correlations, if the analysis is extended to include two manifolds - corresponding to the ground state and the states excited by a single photon - rather than just two levels.

  10. Real time drift measurement for colloidal probe atomic force microscope: a visual sensing approach

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yuliang, E-mail: wangyuliang@buaa.edu.cn; Bi, Shusheng [Robotics Institute, School of Mechanical Engineering and Automation, Beihang University, Beijing 100191 (China); Wang, Huimin [Department of Materials Science and Engineering, The Ohio State University, 2041 College Rd., Columbus, OH 43210 (United States)

    2014-05-15

    Drift has long been an issue in atomic force microscope (AFM) systems and limits their ability to make long time period measurements. In this study, a new method is proposed to directly measure and compensate for the drift between AFM cantilevers and sample surfaces in AFM systems. This was achieved by simultaneously measuring z positions for beads at the end of an AFM colloidal probe and on sample surface through an off-focus image processing based visual sensing method. The working principle and system configuration are presented. Experiments were conducted to validate the real time drift measurement and compensation. The implication of the proposed method for regular AFM measurements is discussed. We believe that this technique provides a practical and efficient approach for AFM experiments requiring long time period measurement.

  11. Atomic scale properties of magnetic Mn-based alloys probed by emission Mössbauer spectroscopy

    CERN Multimedia

    Mn-based alloys are characterized by a wealth of properties, which are of interest both from fundamental physics point of view and particularly attractive for different applications in modern technology: from magnetic storage to sensing and spin-based electronics. The possibility to tune their magnetic properties through post-growth thermal processes and/or stoichiometry engineering is highly important in order to target different applications (i.e. Mn$_{x}$Ga) or to increase their Curie temperature above room temperature (i.e. off-stoichiometric MnSi). In this project, the Mössbauer effect will be applied at $^{57}$Fe sites following implantation of radioactive $^{57}$Mn, to probe the micro-structure and magnetism of Mn-based alloys on the atomic-scale. The proposed experimental plan is devoted to establish a direct correlation between the local structure and bulk magnetism (and other physical properties) of Mn-based alloys.

  12. Three-dimensional Chemical Imaging of Embedded Nanoparticles using Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Kuchibhatla, Satyanarayana V N T; Shutthanandan, V.; Prosa, Ty J.; Adusumilli, Praneet; Arey, Bruce W.; Buxbaum, Alex; Wang, Y. C.; Tessner, Ted; Ulfig, Robert M.; Wang, Chong M.; Thevuthasan, Suntharampillai

    2012-05-03

    Analysis of nanoparticles is often challenging especially when they are embedded in a matrix. Hence, we have used laser-assisted atom probe tomography (APT) to analyze the Au-nanoclusters synthesized in situ using ion beam implantation in single crystal MgO matrix. APT analysis along with scanning transmission electron microscopy and energy dispersive spectroscopy (STEM-EDS) indicated that the nanoparticles have an average size ~ 8 - 12 nm. While it is difficult to analyze the composition of individual nanoparticles using STEM, APT analysis can give three dimensional compositions of the same. It was shown that the maximum Au-concentration in the nanoparticles increases with increasing particle size, with a maximum Au-concentration of up to 50%.

  13. Analysis of deuterium in V-Fe5at.% film by atom probe tomography (APT)

    KAUST Repository

    Gemma, Ryota

    2011-09-01

    V-Fe5at.% 2 and 10-nm thick single layered films were prepared by ion beam sputtering on W substrate. They were loaded with D from gas phase at 0.2 Pa and at 1 Pa, respectively. Both lateral and depth D distribution of these films was investigated in detail by atom probe tomography. The results of analysis are in good agreement between the average deuterium concentration and the value, expected from electromotive force measurement on a similar flat film. An enrichment of deuterium at the V/W interface was observed for both films. The origin of this D-accumulation was discussed in respect to electron transfer, mechanical stress and misfit dislocations. © 2010 Elsevier B.V. All rights reserved.

  14. Effect of an external radiation field on the properties of the atoms and cavity field in the two-atom Tavis-Cummings model

    Institute of Scientific and Technical Information of China (English)

    王忠纯; 王琪; 张永生; 郭光灿

    2005-01-01

    We study the properties of atoms and cavity field in the two-atom Tavis-Cummings model where the two atoms interact with each other and are also driven by an external classical field. We consider the special case that the cavity is initially in a coherent state. The atomic inversion, the average photons number and the Mandel parameter in the driven Tavis-Cummings model are given and analysed numerically. We pay special attention to the dynamical behaviour of the atoms and the cavity field modified by the external field.

  15. Field Ionization detection of supersonic helium atom beams

    Science.gov (United States)

    Doak, R. B.

    2003-10-01

    Field ionization detectors (FID) may offer near-unity detection efficiency and nanoscale spatial resolution. To date, FID detection of molecular beams has been limited to effusive beams of broad Maxwellian velocity distributions. We report FID measurements on monoenergetic helium beams, including intensity measurements and time-of-flight measurements. The FID tips were carefully prepared and characterized in a field ionization microscope prior to use. With the supersonic helium beam we find a much smaller effective detection area ( 50 sq. nm) than was reported in the effusive helium beam experiments ( 200,000 sq. nm). This suggests that the FID ionization yield depends strongly on energy loss by the impinging atom during its initial collision with the FID surface: Our thermal energy, monoenergetic helium beam atoms likely lose little or no energy upon scattering from the clean tungsten FID surface, allowing the scattered atoms to escape the FID polarization field and therby reducing the ionization yield. To improve signal levels, inelastic scattering might be enhanced by use of lower beam velocities (present in the tails of a Maxwellian) or by adsorbing an overlayer on the FID tip (present at cryogenic tip temperatures). These factors likely explain the higher detection yields measured in the effusive beam experiments.

  16. Nanogeochronology of discordant zircon measured by atom probe microscopy of Pb-enriched dislocation loops.

    Science.gov (United States)

    Peterman, Emily M; Reddy, Steven M; Saxey, David W; Snoeyenbos, David R; Rickard, William D A; Fougerouse, Denis; Kylander-Clark, Andrew R C

    2016-09-01

    Isotopic discordance is a common feature in zircon that can lead to an erroneous age determination, and it is attributed to the mobilization and escape of radiogenic Pb during its post-crystallization geological evolution. The degree of isotopic discordance measured at analytical scales of ~10 μm often differs among adjacent analysis locations, indicating heterogeneous distributions of Pb at shorter length scales. We use atom probe microscopy to establish the nature of these sites and the mechanisms by which they form. We show that the nanoscale distribution of Pb in a ~2.1 billion year old discordant zircon that was metamorphosed c. 150 million years ago is defined by two distinct Pb reservoirs. Despite overall Pb loss during peak metamorphic conditions, the atom probe data indicate that a component of radiogenic Pb was trapped in 10-nm dislocation loops that formed during the annealing of radiation damage associated with the metamorphic event. A second Pb component, found outside the dislocation loops, represents homogeneous accumulation of radiogenic Pb in the zircon matrix after metamorphism. The (207)Pb/(206)Pb ratios measured from eight dislocation loops are equivalent within uncertainty and yield an age consistent with the original crystallization age of the zircon, as determined by laser ablation spot analysis. Our results provide a specific mechanism for the trapping and retention of radiogenic Pb during metamorphism and confirm that isotopic discordance in this zircon is characterized by discrete nanoscale reservoirs of Pb that record different isotopic compositions and yield age data consistent with distinct geological events. These data may provide a framework for interpreting discordance in zircon as the heterogeneous distribution of discrete radiogenic Pb populations, each yielding geologically meaningful ages.

  17. Determination of solute site occupancies within γ' precipitates in nickel-base superalloys via orientation-specific atom probe tomography.

    Science.gov (United States)

    Meher, S; Rojhirunsakool, T; Nandwana, P; Tiley, J; Banerjee, R

    2015-12-01

    The analytical limitations in atom probe tomography such as resolving a desired set of atomic planes, for solving complex materials science problems, have been overcome by employing a well-developed unique and reproducible crystallographic technique, involving synergetic coupling of orientation microscopy with atom probe tomography. The crystallographic information in atom probe reconstructions has been utilized to determine the solute site occupancies in Ni-Al-Cr based superalloys accurately. The structural information in atom probe reveals that both Al and Cr occupy the same sub-lattice within the L12-ordered γ' precipitates to form Ni3(Al,Cr) precipitates in a Ni-14Al-7Cr (at%) alloy. Interestingly, the addition of Co, which is a solid solution strengthener, to a Ni-14Al-7Cr alloy results in the partial reversal of Al site occupancy within γ' precipitates to form (Ni,Al)3(Al,Cr,Co) precipitates. This unique evidence of reversal of Al site occupancy, resulting from the introduction of other solutes within the ordered structures, gives insights into the relative energetics of different sub-lattice sites when occupied by different solutes.

  18. Entanglement of Three Atoms Induced by a Coherent Field

    Institute of Scientific and Technical Information of China (English)

    WANG Xiu-Wu; CAI Jin-Fang

    2006-01-01

    We calculate the concurrence and spin squeezing parameter of three atoms induced by a coherent field.It shows that when the mean numbers of photon of the field is very small, concurrence exhibits a certain kind of approximative periodic vibration. With the increase of the mean numbers of photon, its periodicity will be interrupted.As for the relationship between the concurrence and spin squeezing, numeric result shows that under Dick model, spin squeezing serves as a sufficient but not necessary condition for concurrence.

  19. Measuring the Earth's gravity field with cold atom interferometers

    CERN Document Server

    Carraz, Olivier; Massotti, Luca; Haagmans, Roger; Silvestrin, Pierluigi

    2015-01-01

    The scope of the paper is to propose different concepts for future space gravity missions using Cold Atom Interferometers (CAI) for measuring the diagonal elements of the gravity gradient tensor, the spacecraft angular velocity and the spacecraft acceleration. The aim is to achieve better performance than previous space gravity missions due to a very low white noise spectral behaviour of the CAI instrument and a very high common mode rejection, with the ultimate goals of determining the fine structures of the gravity field with higher accuracy than GOCE and detecting time-variable signals in the gravity field.

  20. Ordering and site occupancy of D03 ordered Fe3Al-5 at%Cr evaluated by means of atom probe tomography

    KAUST Repository

    Rademacher, Thomas W.

    2011-05-01

    Addition of ternary elements to the D03 ordered Fe3Al intermetallic phase is a general approach to optimise its mechanical properties. To understand the physical influences of such additions the determination of the probability of site occupancies of these additions on the lattice site and ordering parameters is of high interest. Some common experimental techniques such as X-ray diffraction or Atom Location by Channelling Enhanced Microanalysis (ALCHEMI) are usually applied to explore this interplay. Unfortunately, certain published results are partly inconsistent, imprecise or even contradictory. In this study, these aspects are evaluated systematically by atom probe tomography (APT) and a special data analysis method. Additionally, to account for possible field evaporation effects that can falsify the estimation of site occupancy and induce misinterpretations, APT evaporation sequences were also simulated. As a result, chromium occupies most frequently the next nearest neighbour sites of Al atoms and local ordering parameters could be achieved. © 2010 Elsevier B.V.

  1. Measurements of Electric Field Fluctuations Using a Capacitive Probe on the MST Reversed Field Pinch

    Science.gov (United States)

    Tan, Mingsheng; Almagri, A. F.; Sarff, J. S.; McCollam, K. J.; Triana, J. C.; Li, H.; Ding, W. X.; Liu, W.

    2015-11-01

    Experimental measurements and extended MHD computation reveal that both flow and current density fluctuations are important for the magnetic relaxation of RFP plasmas via tearing fluctuations. Motivated by these results, we have developed a multi-electrode capacitive probe for radial profile measurements of the electrostatic potential deep in the plasma. The capacitive probe measures the ac plasma potential via electrodes insulated from the plasma using an annular boron nitride dielectric (also the particle shield), provided the secondary emission is sufficiently large (Te>20 eV). The probe has ten sets of four capacitors with 1.5 cm radial separation. At each radius, four capacitors are arranged on a 1.3 cm square grid. This probe has been inserted up to 15 cm from the wall in 200 kA deuterium plasmas. The fluctuation amplitudes increase during the sawtooth crash and the power spectrum broadens (similar to the behavior of magnetic field fluctuations). The frequency bandwidth allows measurements of the radial coherence and phase of the fluctuations associated with rotating tearing modes up to the Alfvénic range. A next-step goal is measurement of the total dynamo emf, ~ /B0 , to complement ongoing measurements of the Hall dynamo emf, / ne , using a deep-insertion magnetic probe. M. Tan is supported by ITER-China Program. Work is supported by US DOE.

  2. Nanomechanical and topographical imaging of living cells by atomic force microscopy with colloidal probes

    Energy Technology Data Exchange (ETDEWEB)

    Puricelli, Luca; Galluzzi, Massimiliano; Schulte, Carsten; Podestà, Alessandro, E-mail: alessandro.podesta@mi.infn.it; Milani, Paolo [CIMaINa and Department of Physics, Università degli Studi di Milano, Via Celoria 16, 20133 Milano (Italy)

    2015-03-15

    Atomic Force Microscopy (AFM) has a great potential as a tool to characterize mechanical and morphological properties of living cells; these properties have been shown to correlate with cells’ fate and patho-physiological state in view of the development of novel early-diagnostic strategies. Although several reports have described experimental and technical approaches for the characterization of cellular elasticity by means of AFM, a robust and commonly accepted methodology is still lacking. Here, we show that micrometric spherical probes (also known as colloidal probes) are well suited for performing a combined topographic and mechanical analysis of living cells, with spatial resolution suitable for a complete and accurate mapping of cell morphological and elastic properties, and superior reliability and accuracy in the mechanical measurements with respect to conventional and widely used sharp AFM tips. We address a number of issues concerning the nanomechanical analysis, including the applicability of contact mechanical models and the impact of a constrained contact geometry on the measured Young’s modulus (the finite-thickness effect). We have tested our protocol by imaging living PC12 and MDA-MB-231 cells, in order to demonstrate the importance of the correction of the finite-thickness effect and the change in Young’s modulus induced by the action of a cytoskeleton-targeting drug.

  3. Mg dopant distribution in an AlGaN/GaN p-type superlattice assessed using atom probe tomography, TEM and SIMS

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, S E; Kappers, M J; Barnard, J S; Humphreys, C J; Oliver, R A [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke St., Cambridge, CB2 3QZ (United Kingdom); Clifton, P H; Ulfig, R M, E-mail: sb534@cam.ac.u [Imago Scientific Instruments Corporation, 5500 Nobel Drive, Madison, WI, 53711 (United States)

    2010-02-01

    P-type conducting layers are critical in GaN-based devices such as LEDs and laser diodes. Such layers are often produced by doping GaN with Mg, but the hole concentration can be enhanced using AlGaN/GaN p-type superlattices by exploiting the built-in polarisation fields. A Mg-doped AlGaN/GaN superlattice was studied using SIMS. Although the AlGaN and GaN were nominally doped to the same level, the SIMS data suggested a difference in doping density between the two materials. Atom probe tomography was then used to investigate the Mg distribution. The superlattice repeats were clearly visible, as expected and, in addition, significant Mg clustering was observed in both the GaN and AlGaN layers. There were many more Mg clusters in the AlGaN layers than the GaN layers, accounting for the difference in doping density suggested by SIMS. To evaluate the structural accuracy of the atom probe reconstruction, layer thicknesses from the atom probe were compared with STEM images. Finally, future work is proposed to investigate the Mg clusters in the TEM.

  4. Probing strong field ionization of solids with a Thomson parabola spectrometer

    Indian Academy of Sciences (India)

    Malay Dalui; T Madhu Trivikram; Ram Gopal; M Krishnamurthy

    2014-01-01

    Intense ultrashort laser pulses are known to generate high-density, high-temperature plasma from any substrate. Copious emission of hot electrons, from a solid substrate, results in strong electrostatic field that accelerates the ions with energies ranging from a few eV to MeV. Ion spectrometry from laser–plasma is convolved with multiple atomic systems, several charge states and a broad energy spread. Conventional mass spectrometric techniques have serious limitations to probe this ionization dynamics. We have developed an imaging ion spectrometer that measures charge/mass-resolved ion kinetic energies over the entire range. Microchannel plate (MCP) is used as the position-sensitive detector to perform online and single shot measurements. The wellresolved spectrum even for the low-energy ions, demonstrates that the spectral width is limited by the space-charge repulsion for the ions generated in the hot dense plasma.

  5. Nonlocal Response of Metallic Nanospheres Probed by Light, Electrons, and Atoms

    DEFF Research Database (Denmark)

    Christensen, Thomas; Yan, Wei; Raza, Søren

    2014-01-01

    Inspired by recent measurements on individual metallic nanospheres that cannot be explained with traditional classical electrodynamics, we theoretically investigate the effects of nonlocal response by metallic nanospheres in three distinct settings: atomic spontaneous emission, electron energy loss...... spectroscopy, and light scattering. These constitute two near-field and one far-field measurements, with zero-, one-, and two-dimensional excitation sources, respectively. We search for the clearest signatures of hydrodynamic pressure waves in nanospheres. We employ a linearized hydrodynamic model, and Mie......–Lorenz theory is applied for each case. Nonlocal response shows its mark in all three configurations, but for the two near-field measurements, we predict especially pronounced nonlocal effects that are not exhibited in far-field measurements. Associated with every multipole order is not only a single...

  6. Atoms in parallel fields: Analysis with diffractive periodic orbits

    Science.gov (United States)

    Owen, S. M.; Monteiro, T. S.; Dando, P. A.

    2000-11-01

    We show that fluctuations in the density of states of nonhydrogenic atoms in parallel fields are strongly influenced by diffractive periodic orbits. Unlike typical systems with a diffractive point scatterer, the atomic core of small atoms like lithium and helium is best understood as a combined geometric and diffractive scatterer. Each Gutzwiller (geometric) periodic orbit is paired with a diffractive orbit of the same action. We investigate, particularly, amplitudes for contributions from repetitions, and multiple scattering orbits. We find that periodic orbit repetitions are described by ``hybrid'' orbits, combining both diffractive and geometric core scatters, and that by including all possible permutations we can obtain excellent agreement between the semiclassical model and accurate fully quantal calculations. For high repetitions, we find even one-scatter diffractive contributions become of the same order as those of the geometric periodic orbit for repetition numbers n~ħ-1/2. Although the contribution of individual diffractive orbits is suppressed by O(ħ1/2) relative to the geometric periodic orbits, the proliferation of diffractive orbits with increasing period means that the diffractive effect for the atom can persist in the ħ-->0 limit.

  7. Suppression of reflections by directive probes in spherical near-field measurements

    DEFF Research Database (Denmark)

    Hansen, Per Christian; Larsen, Flemming H.

    1984-01-01

    The influence of probe correction in spherical near-field measurements on signals from outside the test volume is investigated theoretically and experimentally. It is found that the suppression of reflections obtained by a directive probe is not disturbed by the probe correction. A geometric rela...

  8. Very high-accuracy calibration of radiation pattern and gain of a near-field probe

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Nielsen, Jeppe Majlund; Breinbjerg, Olav

    2014-01-01

    In this paper, very high-accuracy calibration of the radiation pattern and gain of a near-field probe is described. An open-ended waveguide near-field probe has been used in a recent measurement of the C-band Synthetic Aperture Radar (SAR) Antenna Subsystem for the Sentinel 1 mission of the Europ......In this paper, very high-accuracy calibration of the radiation pattern and gain of a near-field probe is described. An open-ended waveguide near-field probe has been used in a recent measurement of the C-band Synthetic Aperture Radar (SAR) Antenna Subsystem for the Sentinel 1 mission...

  9. A new probe of magnetic fields in the pre-reionization epoch: II. Detectability

    CERN Document Server

    Gluscevic, Vera; Fang, Xiao; Hirata, Christopher; Oklopcic, Antonija; Mishra, Abhilash

    2016-01-01

    In the first paper of this series, we proposed a novel method to probe large-scale intergalactic magnetic fields during the cosmic Dark Ages, using 21-cm tomography. This method relies on the effect of spin alignment of hydrogen atoms in a cosmological setting, and on the effect of magnetic precession of the atoms on the statistics of the 21-cm brightness-temperature fluctuations. In this paper, we forecast the sensitivity of future tomographic surveys to detecting magnetic fields using this method. For this purpose, we develop a minimum-variance estimator formalism to capture the characteristic anisotropy signal using the two-point statistics of the brightness-temperature fluctuations. We find that, depending on the reionization history, and subject to the control of systematics from foreground subtraction, an array of dipole antennas in a compact-grid configuration with a collecting area slightly exceeding one square kilometer can achieve a $1\\sigma$ detection of $\\sim$$10^{-21}$ Gauss comoving (scaled to p...

  10. Rydberg atoms in low-frequency fields : fundamental aspects and applications

    NARCIS (Netherlands)

    Gürtler, Andreas Stefan

    2003-01-01

    In this thesis we investigate highly excited atoms, so-called Rydberg atoms, in oscillating fields with frequencies from the megahertz to the terahertz domain. The strong interaction of Rydberg atoms with external fields is used to establish a connection between the ionization of Rydberg atoms by ra

  11. Theoretical femtosecond physics atoms and molecules in strong laser fields

    CERN Document Server

    Grossmann, Frank

    2013-01-01

    Theoretical investigations of atoms and molecules interacting with pulsed or continuous wave lasers up to atomic field strengths on the order of 10^16 W/cm² are leading to an understanding of many challenging experimental discoveries. This book deals with the basics of femtosecond physics and goes up to the latest applications of new phenomena. The book presents an introduction to laser physics with mode-locking and pulsed laser operation. The solution of the time-dependent Schrödinger equation is discussed both analytically and numerically. The basis for the non-perturbative treatment of laser-matter interaction in the book is the numerical solution of the time-dependent Schrödinger equation. The light field is treated classically, and different possible gauges are discussed. Physical phenonema, ranging from Rabi-oscillations in two-level systems to the ionization of atoms, the generation of high harmonics, the ionization and dissociation of molecules as well as the control of chemical reactions are pre...

  12. Atoms and Ions Interacting with Particles and Fields: Final Report

    Energy Technology Data Exchange (ETDEWEB)

    Robicheaux, Francis [Auburn Univ., AL (United States)

    2014-09-18

    This grant supported research in basic atomic, molecular and optical physics related to the interactions of atoms with particles and fields. The duration of the grant was the 10 year period from 8/2003 to 8/2013. All of the support from the grant was used to pay salaries of the PI, postdocs, graduate students, and undergraduates and travel to conferences and meetings. The results were in the form of publications in peer reviewed journals. There were 65 peer reviewed publications over these 10 years with 8 of the publications in Physical Review Letters; all of the other articles were in respected peer reviewed journals (Physical Review A, New Journal of Physics, Journal of Physics B, ...). I will disuss the results for the periods of time relevant for each grant period.

  13. Solute atom migration in GH4169 superalloy under electrostatic fields

    Institute of Scientific and Technical Information of China (English)

    Yao Wang; Lei Wang; Yang Liu; Xiu Song; Bei-jiang Zhang; Jin-hui Du

    2013-01-01

    Electric field treatment (EFT) was applied on GH4169 alloy during aging at 500-800◦C to investigate the microstructure and property variation of the alloy under the action of EFT. The results demonstrate that the short-distance diff usion of Al, Ti, and Nb atoms can be accelerated by EFT, which results in the coarsening ofγ ? andγ ?? phases. Meanwhile, lattice distortion can be caused by the segregation of Fe and Cr atoms, owing to the vacancy flows migrating toward the charged surfaces of the alloy. Therefore, the alloy is hardened by the application of EFT, even if the strength of the alloy is partly reduced, which is caused by precipitation coarsening.

  14. On the truncation of the azimuthal mode spectrum of high-order probes in probe-corrected spherical near-field antenna measurements

    DEFF Research Database (Denmark)

    Pivnenko, Sergey; Laitinen, Tommi

    2011-01-01

    Azimuthal mode (m mode) truncation of a high-order probe pattern in probe-corrected spherical near-field antenna measurements is studied in this paper. The results of this paper provide rules for appropriate and sufficient m-mode truncation for non-ideal first-order probes and odd-order probes...

  15. Optical processes of photonic band gap structure with dressing field in atomic system

    Science.gov (United States)

    Zhang, Yun-Zhe; Liu, Zhe; Cai, Kang-Ning; Zhong, Hua; Zhang, Wei-Tao; Liu, Jun-Feng; Zhang, Yan-Peng

    2016-12-01

    We experimentally investigate probe transmission signals (PTS), the four-wave mixing photonic band gap signal (FWM BGS), and the fluorescence signal (FLS) in an inverted Y-type four level atomic system. For the first time, we compare the FLS of the two ground-state hyperfine levels of Rb 85. In particular, the second-order and the fourth-order fluorescence signals perform dramatic dressing discrepancies under the two hyperfine levels. Moreover, we find that the dressing field has some dressing effects on three such types of signals. Therefore, we demonstrate that the characteristics of PTS, FWM BGS, and FLS can be controlled by frequency detunings, the powers or phases of the dressing field. Such research could have potential applications in optical diodes, amplifiers, and quantum information processing.

  16. Probe measurements of the three-dimensional magnetic field structure in a rotating magnetic field sustained field-reversed configuration

    Science.gov (United States)

    Velas, K. M.; Milroy, R. D.

    2014-01-01

    A translatable three-axis probe was constructed and installed on the translation, confinement, and sustainment upgrade (TCSU) experiment. With ninety windings, the probe can simultaneously measure Br, Bθ, and Bz at 30 radial positions, and can be placed at any desired axial position within the field reversed configuration (FRC) confinement chamber. Positioning the probe at multiple axial positions and taking multiple repeatable shots allows for a full r-z map of the magnetic field. Measurements were made for odd-parity rotating magnetic field (RMF) antennas and even-parity RMF. The steady state data from applying a 10 kHz low pass filter used in conjunction with data at the RMF frequency yields a map of the full 3D rotating field structure. Comparisons will be made to the 3D magnetic structure predicted by NIMROD simulations, with parameters adjusted to match that of the TCSU experiments. The probe provides sufficient data to utilize a Maxwell stress tensor approach to directly measure the torque applied to the FRC's electrons, which combined with a resistive torque model, yields an estimate of the average FRC resistivity.

  17. Probe frequency- and field intensity-sensitive coherent control effects in an EIT-based periodic layered medium

    Institute of Scientific and Technical Information of China (English)

    Teh-Chau Liau; Jin-Jei Wu; Jianqi Shen; Tzong-Jer Yang

    2012-01-01

    A periodic layered medium,with unit cells consisting of a dielectric and an electromagnetically-induced transparency (EIT)-based atomic vapor,is designed for light propagation manipulation. Considering that a destructive quantum interference relevant to a two-photon resonance emerges in EIT-based atoms interacting with both control and probe fields,an EIT-based periodic layered medium exhibits a flexible frequency-sensitive optical response,where a very small variation in the probe frequency can lead to a drastic variation in reflectance and transmittance.The present EIT-based periodic layered structure can result in controllable optical processes that depend sensitively on the external control field.The tunable and sensitive optical response induced by the quantum interference of a multi-level atomic system can be applied in the fabrication of new photonic and quantum optical devices.This material will also open a good perspective for the application of such designs in several new fields,including photonic microcircuits or integrated optical circuits.

  18. Theoretical investigation of boundary contours of ground-state atoms in uniform electric fields

    Science.gov (United States)

    Shi, Hua; Zhao, Dong-Xia; Yang, Zhong-Zhi

    2015-12-01

    The boundary contours were investigated for first 54 ground-state atoms of the periodic table when they are in uniform electric fields of strengths 106, 107 and 108 V/m. The atomic characteristic boundary model in combination with an ab-initio method was employed. Some regularities of the deformation of atoms, ΔR, in above electric fields are revealed. Furthermore, atomic polarisabilities of the first 54 elements of the periodic table are shown to correlate strongly with the mean variation rate of atomic radial size divided by the strength of the electric field F, ?, which provides a predictive method of calculating atomic polarisabilities of 54 atoms.

  19. Field emission sensing for non-contact probe recording

    NARCIS (Netherlands)

    Febre, le Alexander Jonathan

    2008-01-01

    In probe recording an array of thousands of nanometer-sharp probes is used to write and read on a storage medium. By using micro-electromechanical system technology (MEMS) for fabrication, small form factor memories with high data density and low power consumption can be obtained. Such a system is e

  20. Nanometal Skin of Plasmonic Heterostructures for Highly Efficient Near-Field Scattering Probes

    Science.gov (United States)

    Zito, Gianluigi; Rusciano, Giulia; Vecchione, Antonio; Pesce, Giuseppe; di Girolamo, Rocco; Malafronte, Anna; Sasso, Antonio

    2016-08-01

    In this work, atomic force microscopy probes are functionalized by virtue of self-assembling monolayers of block copolymer (BCP) micelles loaded either with clusters of silver nanoparticles or bimetallic heterostructures consisting of mixed species of silver and gold nanoparticles. The resulting self-organized patterns allow coating the tips with a sort of nanometal skin made of geometrically confined nanoislands. This approach favors the reproducible engineering and tuning of the plasmonic properties of the resulting structured tip by varying the nanometal loading of the micelles. The newly conceived tips are applied for experiments of tip-enhanced Raman scattering (TERS) spectroscopy and scattering-type scanning near-field optical microscopy (s-SNOM). TERS and s-SNOM probe characterizations on several standard Raman analytes and patterned nanostructures demonstrate excellent enhancement factor with the possibility of fast scanning and spatial resolution nanoparticles at the tip apex, which may promote the tuning of the plasmonic properties, a large enhancement, and the possibility of adding new degrees of freedom for tip functionalization.

  1. Near-field Microwave Scanning Probe Imaging of Conductivity Inhomogeneities in CVD Graphene

    Energy Technology Data Exchange (ETDEWEB)

    Tselev, Alexander [ORNL; Lavrik, Nickolay V [ORNL; Vlassiouk, Ivan V [ORNL; Briggs, Dayrl P [ORNL; Rutgers, Maarten [Asylum Research, Santa Barbara, CA; Proksch, Roger [Asylum Research, Santa Barbara, CA; Kalinin, Sergei V [ORNL

    2012-01-01

    We have performed near-field scanning microwave microscopy (SMM) of graphene grown by chemical vapor deposition. Due to the use of probe-sample capacitive coupling and a relatively high ac frequency of a few GHz, this scanning probe method allows mapping of local conductivity without a dedicated counter electrode, with a spatial resolution of about 50 nm. Here, the coupling was enabled by atomic layer deposition of alumina on top of graphene, which in turn enabled imaging both large-area films, as well as micron-sized islands, with a dynamic range covering a low sheet resistance of a metal film and a high resistance of highly disordered graphene. The structures of graphene grown on Ni films and Cu foils are explored, and the effects of growth conditions are elucidated. We present a simple general scheme for interpretation of the contrast in the SMM images of our graphene samples and other two-dimensional conductors, which is supported by extensive numerical finite-element modeling. We further demonstrate that combination of the SMM and numerical modeling allows quantitative information about the sheet resistance of graphene to be obtained, paving the pathway for characterization of graphene conductivity with a sub-100 nm special resolution.

  2. Measurements of plasma density fluctuations and electric wave fields using spherical electrostatic probes

    Energy Technology Data Exchange (ETDEWEB)

    Eriksson, A.I.; Bostroem, R.

    1995-04-01

    Spherical electrostatic probes are in wide use for the measurements of electric fields and plasma density. This report concentrates on the measurements of fluctuations of these quantities rather than background values. Potential problems with the technique include the influence of density fluctuations on electric field measurements and vice versa, effects of varying satellite potential, and non-linear rectification in the probe and satellite sheaths. To study the actual importance of these and other possible effects, we simulate the response of the probe-satellite system to various wave phenomena in the plasma by applying approximate analytical as well as numerical methods. We use a set of non-linear probe equations, based on probe characteristics experimentally obtained in space, and therefore essentially independent of any specific probe theory. This approach is very useful since the probe theory for magnetized plasmas is incomplete. 47 refs.

  3. Atom probe tomography characterizations of high nickel, low copper surveillance RPV welds irradiated to high fluences

    Science.gov (United States)

    Miller, M. K.; Powers, K. A.; Nanstad, R. K.; Efsing, P.

    2013-06-01

    The Ringhals Units 3 and 4 reactors in Sweden are pressurized water reactors (PWRs) designed and supplied by Westinghouse Electric Company, with commercial operation in 1981 and 1983, respectively. The reactor pressure vessels (RPVs) for both reactors were fabricated with ring forgings of SA 508 class 2 steel. Surveillance blocks for both units were fabricated using the same weld wire heat, welding procedures, and base metals used for the RPVs. The primary interest in these weld metals is because they have very high nickel contents, with 1.58 and 1.66 wt.% for Unit 3 and Unit 4, respectively. The nickel content in Unit 4 is the highest reported nickel content for any Westinghouse PWR. Although both welds contain less than 0.10 wt.% copper, the weld metals have exhibited high irradiation-induced Charpy 41-J transition temperature shifts in surveillance testing. The Charpy impact 41-J shifts and corresponding fluences are 192 °C at 5.0 × 1023 n/m2 (>1 MeV) for Unit 3 and 162 °C at 6.0 × 1023 n/m2 (>1 MeV) for Unit 4. These relatively low-copper, high-nickel, radiation-sensitive welds relate to the issue of so-called late-blooming nickel-manganese-silicon phases. Atom probe tomography measurements have revealed ˜2 nm-diameter irradiation-induced precipitates containing manganese, nickel, and silicon, with phosphorus evident in some of the precipitates. However, only a relatively few number of copper atoms are contained within the precipitates. The larger increase in the transition temperature shift in the higher copper weld metal from the Ringhals R3 Unit is associated with copper-enriched regions within the manganese-nickel-silicon-enriched precipitates rather than changes in their size or number density.

  4. An atom probe perspective on phase separation and precipitation in duplex stainless steels

    Science.gov (United States)

    Guo, Wei; Garfinkel, David A.; Tucker, Julie D.; Haley, Daniel; Young, George A.; Poplawsky, Jonathan D.

    2016-06-01

    Three-dimensional chemical imaging of Fe-Cr alloys showing Fe-rich (α)/Cr-rich (α‧) phase separation is reported using atom probe tomography techniques. The extent of phase separation, i.e., amplitude and wavelength, has been quantitatively assessed using the Langer-Bar-on-Miller, proximity histogram, and autocorrelation function methods for two separate Fe-Cr alloys, designated 2101 and 2205. Although the 2101 alloy possesses a larger wavelength and amplitude after annealing at 427 °C for 100-10 000 h, it exhibits a lower hardness than the 2205 alloy. In addition to this phase separation, ultra-fine Ni-Mn-Si-Cu-rich G-phase precipitates form at the α/α‧ interfaces in both alloys. For the 2101 alloy, Cu clusters act to form a nucleus, around which a Ni-Mn-Si shell develops during the precipitation process. For the 2205 alloy, the Ni and Cu atoms enrich simultaneously and no core-shell chemical distribution was found. This segregation phenomenon may arise from the exact Ni/Cu ratio inside the ferrite. After annealing for 10 000 h, the number density of the G-phase within the 2205 alloy was found to be roughly one order of magnitude higher than in the 2101 alloy. The G-phase precipitates have an additional deleterious effect on the thermal embrittlement, as evaluated by the Ashby-Orowan equation, which explains the discrepancy between the hardness and the rate of phase separation with respect to annealing time (Gladman T 1999 Mater. Sci. Tech. Ser. 15 30-36). ).

  5. The atom in an intense optical field (2nd revised and enlarged edition)

    Science.gov (United States)

    Delone, N. B.; Krainov, V. P.

    The basic features characterizing multiphoton processes are examined, and descriptions are given of such phenomena as the multiphoton ionization of atoms, multiphoton resonance, and the perturbation of the bound-state spectrum in atoms in an optical field. The design of an experiment for measuring the interaction of laser radiation with atoms is proposed. Particular attention is given to nonlinear atomic susceptibilities, the effect of multifrequency laser radiation, and the behavior of highly excited atoms in an intense optical field.

  6. Atom in an intense optical field (2nd revised and enlarged edition)

    Energy Technology Data Exchange (ETDEWEB)

    Delone, N.B.; Krainov, V.P.

    1984-01-01

    The basic features characterizing multiphoton processes are examined, and descriptions are given of such phenomena as the multiphoton ionization of atoms, multiphoton resonance, and the perturbation of the bound-state spectrum in atoms in an optical field. The design of an experiment for measuring the interaction of laser radiation with atoms is proposed. Particular attention is given to nonlinear atomic susceptibilities, the effect of multifrequency laser radiation, and the behavior of highly excited atoms in an intense optical field.

  7. Quasistatic limit of the strong-field approximation describing atoms in intense laser fields: Circular polarization

    CERN Document Server

    Bauer, J H

    2010-01-01

    In the recent work of Vanne and Saenz [Phys. Rev. A 75, 063403 (2007)] the quasistatic limit of the velocity gauge strong-field approximation describing the ionization rate of atomic or molecular systems exposed to linearly polarized laser fields was derived. It was shown that in the low-frequency limit the ionization rate is proportional to the laser frequency (for a constant intensity of the laser field). In the present work I show that for circularly polarized laser fields the ionization rate is proportional to higher powers of the laser frequency for hydrogenic atoms. The new analytical expressions for asymptotic ionization rates (which become accurate in the quasistatic limit) contain no summations over multiphoton contributions. For very low laser frequencies (optical or infrared), these expressions usually remain with an order-of-magnitude agreement with the velocity gauge strong-field approximation.

  8. High-efficiency and high-resolution apertureless plasmonic near-field probe under internal illumination

    Science.gov (United States)

    Jiang, R. H.; Chou, H. C.; Chu, J. Y.; Chen, C.; Yen, T. J.

    2016-09-01

    Near-field scanning optical microscopy (NSOM) offers subwavelength optical resolution beyond the diffraction limit, enabling practical applications in optical imaging, sensing and nanolithography. However, due to the sub-100 nm size of apertures, conventional NSOM aperture probes suffer from the constrains of the strong attenuation of the throughput and limited the spatial resolution. To solve the problem, we designed a novel scheme for apertureless plasmonic probes with radial internal illumination. Employing non-periodic multi-rings geometry for plasmonic excitations, surface plasmons adiabatically nanofocuse energy at tip and the full width at half maximum of the optimal design is 18 nm. The proposed probe was optimized with 2D finite-difference time-domain (FDTD) analysis and realistic parabolic probe geometries. Comprehensive electromagnetic simulation shows that the optimal probe feature obeys Fabry-Pérot condition on the plasmonic metallic wall, giving rise to substantial field enhancement up to 6 orders of magnitude greater than conventional aperture probes without degrading its spatial resolution. We fabricated the proposed probe which possesses apex angle ( 22 degree) and tip radius ( 30 nm). Finally, the proposed near field plasmonic probe effectively combining the high resolution of apertureless probes with high throughput can enable the proposed plasmonic NSOM probe as a practical tool for applications in near field optical microscopy.

  9. Muonic atoms in super-intense laser fields

    Energy Technology Data Exchange (ETDEWEB)

    Shahbaz, Atif

    2009-01-28

    Nuclear effects in hydrogenlike muonic atoms exposed to intense high-frequency laser fields have been studied. Systems of low nuclear charge number are considered where a nonrelativistic description applies. By comparing the radiative response for different isotopes we demonstrate characteristic signatures of the finite nuclear mass, size and shape in the high-harmonic spectra. Cutoff energies in the MeV domain can be achieved, offering prospects for the generation of ultrashort coherent {gamma}-ray pulses. Also, the nucleus can be excited while the laser-driven muon moves periodically across it. The nuclear transition is caused by the time-dependent Coulomb field of the oscillating charge density of the bound muon. A closed-form analytical expression for electric multipole transitions is derived within a fully quantum mechanical approach and applied to various isotopes. The excitation probabilities are in general very small. We compare the process with other nuclear excitation mechanisms through coupling with atomic shells and discuss the prospects to observe it in experiment. (orig.)

  10. The Level-split of the Two-level Entangled Atom in an Optical Field

    Institute of Scientific and Technical Information of China (English)

    CAO Zhuoliang; HUANG Ting; GUO Guangcan; YI Youming

    2002-01-01

    The behavior of a two-level entangled atom in an optical field with circular polarization is studied in this paper. The interaction of an optical field and one of the entangled atoms is analyzed in detail. A general solution of the SchrAo¨Gdinger equation about the motion of the entangled atom is obtained. The properties of the action are dependent on the initial state of the atom. By detecting the entangled atom out of the field, we can obtain the state of the other atom moving in the field. It is shown that the state of the atom out of the field will influence the energies of the split-levels of the atom in the field.

  11. Nanoscale Stoichiometric Analysis of a High-Temperature Superconductor by Atom Probe Tomography.

    Science.gov (United States)

    Pedrazzini, Stella; London, Andrew J; Gault, Baptiste; Saxey, David; Speller, Susannah; Grovenor, Chris R M; Danaie, Mohsen; Moody, Michael P; Edmondson, Philip D; Bagot, Paul A J

    2017-01-31

    The functional properties of the high-temperature superconductor Y1Ba2Cu3O7-δ (Y-123) are closely correlated to the exact stoichiometry and oxygen content. Exceeding the critical value of 1 oxygen vacancy for every five unit cells (δ>0.2, which translates to a 1.5 at% deviation from the nominal oxygen stoichiometry of Y7.7Ba15.3Cu23O54-δ ) is sufficient to alter the superconducting properties. Stoichiometry at the nanometer scale, particularly of oxygen and other lighter elements, is extremely difficult to quantify in complex functional ceramics by most currently available analytical techniques. The present study is an analysis and optimization of the experimental conditions required to quantify the local nanoscale stoichiometry of single crystal yttrium barium copper oxide (YBCO) samples in three dimensions by atom probe tomography (APT). APT analysis required systematic exploration of a wide range of data acquisition and processing conditions to calibrate the measurements. Laser pulse energy, ion identification, and the choice of range widths were all found to influence composition measurements. The final composition obtained from melt-grown crystals with optimized superconducting properties was Y7.9Ba10.4Cu24.4O57.2.

  12. Atom probe tomography investigation of lath boundary segregation and precipitation in a maraging stainless steel.

    Science.gov (United States)

    Thuvander, Mattias; Andersson, Marcus; Stiller, Krystyna

    2013-09-01

    Lath boundaries in a maraging stainless steel of composition 13Cr-8Ni-2Mo-2Cu-1Ti-0.7Al-0.3Mn-0.2Si-0.03C (at%) have been investigated using atom probe tomography following aging at 475 °C for up to 100 h. Segregation of Mo, Si and P to the lath boundaries was observed already after 5 min of aging, and the amount of segregation increases with aging time. At lath boundaries also precipitation of η-Ni₃(Ti, Al) and Cu-rich 9R, in contact with each other, takes place. These co-precipitates grow with time and because of coarsening the area number density decreases. After 100 h of aging a ∼5 nm thick film-like precipitation of a Mo-rich phase was observed at the lath boundaries. From the composition of the film it is suggested that the phase in question is the quasicrystalline R' phase. The film is perforated with Cu-rich 9R and η-Ni₃(Ti, Al) co-precipitates. Not all precipitate types present in the matrix do precipitate at the lath boundaries; the Si-containing G phase and γ'-Ni₃(Ti, Al, Si) and the Cr-rich α' phase were not observed at the lath boundaries.

  13. Three-dimensional atom probe study of Fe-B-based nanocrystalline soft magnetic materials

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Y.M. [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan); Ohkubo, T. [Magnetic Materials Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)] [CREST, Japan Science and Technology Agency (Japan); Ohta, M.; Yoshizawa, Y. [Materials Development Laboratory, New Business Development Center, Hitachi Metals, Ltd., Kumagaya 360-0843 (Japan); Hono, K., E-mail: kazuhiro.hono@nims.go.jp [Magnetic Materials Center, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 (Japan)] [Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba 305-0047 (Japan)] [CREST, Japan Science and Technology Agency (Japan)

    2009-09-15

    Solute clustering and partitioning in new Fe-B-based soft magnetic materials with high saturation magnetic flux density (B{sub s}), (Fe{sub 0.85}B{sub 0.15}){sub 100-x}Cu{sub x} (x = 0.0, 1.0, and 1.5) and Fe{sub 82.65}Cu{sub 1.35}Si{sub y}B{sub 16-y} (y = 0.0, 2.0, and 5.0) melt-spun alloys, were investigated by three-dimensional atom probe and transmission electron microscopy. Although Cu clusters form after annealing in all the samples, it was found that only the clusters of 4-6 nm can serve as heterogeneous nucleation sites for {alpha}-Fe. While annealing the Si-free alloys at 410 deg. C led to the precipitation of Fe{sub 3}B, only {alpha}-Fe nanocrystals were observed in the Si-containing alloys. Lorenz TEM observation indicated the Fe{sub 3}B particles pin magnetic domain walls. The Fe{sub 82.65}Cu{sub 1.35}Si{sub y}B{sub 16-y} alloy with y = 2.0 crystallized by annealing at 400 deg. C exhibited optimal nanocrsytal/amorphous microstructure without the precipitation of Fe{sub 3}B, which led to the lowest coercivity while keeping a high B{sub s} {approx}1.85 T.

  14. Highly excited hydrogen in strong d. c. electric fields: atomic engineering

    Energy Technology Data Exchange (ETDEWEB)

    Nayfeh, M.H.

    1988-03-01

    We excite atomic hydrogen from the ground state via a three-photon process to high-lying excited states in the presence of strong d.c. electric fields. The external field is used to manipulate, control, and design specific atomic structures. We can construct nearly 'one-dimensional' atoms whose electronic distributions are highly extended along the field, and which may have enormous electric dipole moments ('giant-dipole atoms').

  15. Quantitative chemical-structure evaluation using atom probe tomography: Short-range order analysis of Fe–Al

    Energy Technology Data Exchange (ETDEWEB)

    Marceau, R.K.W., E-mail: r.marceau@deakin.edu.au [Institute for Frontier Materials, Deakin University, Geelong, VIC 3216 (Australia); Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf (Germany); Ceguerra, A.V.; Breen, A.J. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia); Raabe, D. [Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf (Germany); Ringer, S.P. [Australian Centre for Microscopy and Microanalysis, The University of Sydney, NSW 2006 (Australia); School of Aerospace, Mechanical and Mechatronic Engineering, The University of Sydney, NSW 2006 (Australia)

    2015-10-15

    Short-range-order (SRO) has been quantitatively evaluated in an Fe–18Al (at%) alloy using atom probe tomography (APT) data and by calculation of the generalised multicomponent short-range order (GM-SRO) parameters, which have been determined by shell-based analysis of the three-dimensional atomic positions. The accuracy of this method with respect to limited detector efficiency and spatial resolution is tested against simulated D0{sub 3} ordered data. Whilst there is minimal adverse effect from limited atom probe instrument detector efficiency, the combination of this with imperfect spatial resolution has the effect of making the data appear more randomised. The value of lattice rectification of the experimental APT data prior to GM-SRO analysis is demonstrated through improved information sensitivity. - Highlights: • Short-range-order (SRO) is quantitatively evaluated using atom probe tomography data. • Chemical species-specific SRO parameters have been calculated. • The accuracy of this method is tested against simulated D0{sub 3} ordered data. • Imperfect spatial resolution combined with finite detector efficiency causes a randomising effect. • Lattice rectification of the data prior to GM-SRO analysis is demonstrated to improve information sensitivity.

  16. Sharing my fifteen years experiences in the research field of Atomic Force Microscopy (AFM

    Directory of Open Access Journals (Sweden)

    Guha T

    2014-03-01

    Full Text Available Atomic Force Microscope (AFM was developed by Binnig and his coworkers in the year 1986. He was awarded Nobel Prize in physics for this work in 1986 in sharing with Rohrer and Ruska. Rationale to develop AFM: Scanning Tunneling Microscope (STM, the precursor to AFM is efficient in imaging electrically conducting specimen at atomic resolution. The impetus for development of AFM came to Binnig’s mind because of relatively poor efficiency of STM to image electrically non-conducting biological samples. He wondered why the surfaces be always imaged with a current but not with a force. He thought if small forces of interactions between a probe tip atoms and specimen surface atoms could be detected and amplified then imaging of biological specimen would be possible at a very high resolution. AFM working Principle: AFM is a Scanning Probe Microscopy (SPM by which imaging is realized by interaction of a probe with sample surface without any beam (light, electron and lens system. The probe is attached to a soft and sensitive cantilever and either specimen is scanned by probe or specimen scans itself under a stationary probe. Probe’s spring constant must be small and the deflection must be measurable along with high resonance frequency. The most commonly associated force with AFM is called Vander Waals force. Three modes of working are contact mode, non contact mode and tapping mode. In contact zone, the probe tip attached with cantilever is held less than a few A˚ from the sample surface and the inter-atomic force between the atoms of probe tip and sample surface is repulsive. In non-contact zone, the probe tip is held at a distance of 100s of A˚ from the sample surface and the inter-atomic force here is long range Vander Waals interaction and is attractive in nature. AFM is also called Scanning Force Microscope because the force of interaction between probe tip atoms and surface atoms is amplified to generate a signal voltage which modulates video

  17. Entanglement and coherence of a three-level atom in Λ configuration interacting with two fields

    Institute of Scientific and Technical Information of China (English)

    Zhang Jian-Song; Xu Jing-Bo

    2009-01-01

    We investigate the entanglement of a three-level atom in A configuration interacting with two quantized field modes by using logarithmic negativity. Then, we study the relationship of the atomic coherence and the entanglement between two fields which are initially prepared in vacuum or thermal states. We find that if the two fields are prepared in thermal states, the atomic coherence can induce the entanglement between two thermal fields. However, there is no coherence-induced entanglement between two vacuum fields.

  18. Electric field and temperature measurement using ultra wide bandwidth pigtailed electro-optic probes.

    Science.gov (United States)

    Bernier, Maxime; Gaborit, Gwenaël; Duvillaret, Lionel; Paupert, Alain; Lasserre, Jean-Louis

    2008-05-01

    We present pigtailed electro-optic probes that allow a simultaneous measurement of high frequency electric fields and temperature using a unique laser probe beam. This has been achieved by the development of a novel probe design associated with a fully automated servo-controlled optical bench, initially developed to stabilize the electric field sensor response. The developed electro-optic probes present a stable response in outdoors conditions over a time duration exceeding 1 h, a frequency bandwidth from kHz to tens of GHz with a sensitivity of 0.7 Vm(-1)Hz(-(1/2)), and a temperature accuracy of 40 mK.

  19. Creation and recovery of a W(111) single atom gas field ion source.

    Science.gov (United States)

    Pitters, Jason L; Urban, Radovan; Wolkow, Robert A

    2012-04-21

    Tungsten single atom tips have been prepared from a single crystal W(111) oriented wire using the chemical assisted field evaporation and etching method. Etching to a single atom tip occurs through a symmetric structure and leads to a predictable last atom unlike etching with polycrystalline tips. The single atom tip formation procedure is shown in an atom by atom removal process. Rebuilds of single atom tips occur on the same crystalline axis as the original tip such that ion emission emanates along a fixed direction for all tip rebuilds. This preparation method could be utilized and developed to prepare single atom tips for ion source development.

  20. Development of Two-Photon Pump Polarization Spectroscopy Probe Technique Tpp-Psp for Measurements of Atomic Hydrogen .

    Science.gov (United States)

    Satija, Aman; Lucht, Robert P.

    2015-06-01

    Atomic hydrogen (H) is a key radical in combustion and plasmas. Accurate knowledge of its concentration can be used to better understand transient phenomenon such as ignition and extinction in combustion environments. Laser induced polarization spectroscopy is a spatially resolved absorption technique which we have adapted for quantitative measurements of H atom. This adaptation is called two-photon pump, polarization spectroscopy probe technique (TPP-PSP) and it has been implemented using two different laser excitation schemes. The first scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-3P levels using a circularly polarized 656-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 656 nm. As a result, the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. The laser beams were created by optical parametric generation followed by multiple pulse dye amplification stages. This resulted in narrow linewidth beams which could be scanned in frequency domain and varied in energy. This allowed us to systematically investigate saturation and Stark effect in 2S-3P transitions with the goal of developing a quantitative H atom measurement technique. The second scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-4P transitions using a circularly polarized 486-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 486 nm. As a result the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. A dye laser was pumped by third harmonic of a Nd:YAG laser to create a laser beam

  1. Photoassociation of Atomic BEC within Mean-Field Approximation:Exact Solutions

    Institute of Scientific and Technical Information of China (English)

    CAI Wei; JING Hui; ZHAN Ming-Sheng; XU Jing-Jun

    2007-01-01

    We propose an exactly solvable method to study the coherent two-colour photoassociation of an atomic BoseEinstein condensate,by linearizing the bilinear atom-molecule coupling,which allows su to conveniently probe the quantum dynamics and statistics of the system.By preparing different initial states of the atomic condensate,we can observe very different quantum statistical properties of the system by exactly calculating the quadraturesqueezed and mode-correlated functions.

  2. Atomic structure and surface defects at mineral-water interfaces probed by in situ atomic force microscopy

    Science.gov (United States)

    Siretanu, Igor; van den Ende, Dirk; Mugele, Frieder

    2016-04-01

    Atomic scale details of surface structure play a crucial role for solid-liquid interfaces. While macroscopic characterization techniques provide averaged information about bulk and interfaces, high resolution real space imaging reveals unique insights into the role of defects that are believed to dominate many aspects of surface chemistry and physics. Here, we use high resolution dynamic Atomic Force Microscopy (AFM) to visualize and characterize in ambient water the morphology and atomic scale structure of a variety of nanoparticles of common clay minerals adsorbed to flat solid surfaces. Atomically resolved images of the (001) basal planes are obtained on all materials investigated, namely gibbsite, kaolinite, illite, and Na-montmorillonite of both natural and synthetic origin. Next to regions of perfect crystallinity, we routinely observe extended regions of various types of defects on the surfaces, including vacancies of one or few atoms, vacancy islands, atomic steps, apparently disordered regions, as well as strongly adsorbed seemingly organic and inorganic species. While their exact nature is frequently difficult to identify, our observations clearly highlight the ubiquity of such defects and their relevance for the overall physical and chemical properties of clay nanoparticle-water interfaces.Atomic scale details of surface structure play a crucial role for solid-liquid interfaces. While macroscopic characterization techniques provide averaged information about bulk and interfaces, high resolution real space imaging reveals unique insights into the role of defects that are believed to dominate many aspects of surface chemistry and physics. Here, we use high resolution dynamic Atomic Force Microscopy (AFM) to visualize and characterize in ambient water the morphology and atomic scale structure of a variety of nanoparticles of common clay minerals adsorbed to flat solid surfaces. Atomically resolved images of the (001) basal planes are obtained on all

  3. Atomic magnetometer

    Science.gov (United States)

    Schwindt, Peter [Albuquerque, NM; Johnson, Cort N [Albuquerque, NM

    2012-07-03

    An atomic magnetometer is disclosed which uses a pump light beam at a D1 or D2 transition of an alkali metal vapor to magnetically polarize the vapor in a heated cell, and a probe light beam at a different D2 or D1 transition to sense the magnetic field via a polarization rotation of the probe light beam. The pump and probe light beams are both directed along substantially the same optical path through an optical waveplate and through the heated cell to an optical filter which blocks the pump light beam while transmitting the probe light beam to one or more photodetectors which generate electrical signals to sense the magnetic field. The optical waveplate functions as a quarter waveplate to circularly polarize the pump light beam, and as a half waveplate to maintain the probe light beam linearly polarized.

  4. Probing Atomic Structure and Majorana Wavefunctions in Mono-Atomic Fe-chains on Superconducting Pb-Surface

    CERN Document Server

    Pawlak, Remy; Klinovaja, Jelena; Meier, Tobias; Kawai, Shigeki; Glatzel, Thilo; Loss, Daniel; Meyer, Ernst

    2015-01-01

    Motivated by the striking promise of quantum computation, Majorana bound states (MBSs) in solid-state systems have attracted wide attention in recent years. In particular, the wavefunction localization of MBSs is a key feature and crucial for their future implementation as qubits. Here, we investigate the spatial and electronic characteristics of topological superconducting chains of iron atoms on the surface of Pb(110) by combining scanning tunneling microscopy (STM) and atomic force microscopy (AFM). We demonstrate that the Fe chains are mono-atomic, structured in a linear fashion, and exhibit zero-bias conductance peaks at their ends which we interprete as signature for a Majorana bound state. Spatially resolved conductance maps of the atomic chains reveal that the MBSs are well localized at the chain ends (below 25 nm), with two localization lengths as predicted by theory. Our observation lends strong support to use MBSs in Fe chains as qubits for quantum computing devices.

  5. Placement of field probes for stabilization of breathing-induced B0-fluctuations in the brain

    DEFF Research Database (Denmark)

    Andersen, Mads; Madsen, Kristoffer H.; Hanson, Lars G.;

    ). It is a fundamental challenge, however, that the B0 measurements are spatially sparse (e.g. 16 probes), and performed outside the brain. Typically, the field is modelled by a linear combination of the spatial shim fields that the scanner can produce (such as spherical harmonics up to 3rd order), and the coefficients......Introduction: B0-fluctuations induced by breathing and body motion lead to artifacts for certain brain imaging sequences at ultra-high field (7T). A promising solution is to monitor the B0-fluctuations during the scan using external field probes, and update the shim currents in real-time (1...... for these spatial terms are determined by least square fitting to the field probe measurements. The probes must be placed carefully to ensure that the spherical harmonics can be distinguished using these few samples, and they must be placed close to the head so that the spatial field model is valid and to have good...

  6. Use of scanning near-field optical microscope with an aperture probe for detection of luminescent nanodiamonds

    Science.gov (United States)

    Shershulin, V. A.; Samoylenko, S. R.; Shenderova, O. A.; Konov, V. I.; Vlasov, I. I.

    2017-02-01

    The suitability of scanning near-field optical microscopy (SNOM) to image photoluminescent diamond nanoparticles with nanoscale resolution is demonstrated. Isolated diamond nanocrystals with an average size of 100 nm, containing negatively charged nitrogen-vacancy (NV-) centers, were chosen as tested material. The NV- luminescence was stimulated by continuous 532 nm laser light. Sizes of analyzed crystallites were monitored by an atomic force microscope. The lateral resolution of the order of 100 nm was reached in SNOM imaging of diamond nanoparticles using 150 nm square aperture of the probe.

  7. Effects of a uniform acceleration on atom-field interactions

    CERN Document Server

    Marino, Jamir; Passante, Roberto; Rizzuto, Lucia; Spagnolo, Salvatore

    2014-01-01

    We review some quantum electrodynamical effects related to the uniform acceleration of atoms in vacuum. After discussing the energy level shifts of a uniformly accelerated atom in vacuum, we investigate the atom-wall Casimir-Polder force for accelerated atoms, and the van der Waals/Casimir-Polder interaction between two accelerated atoms. The possibility of detecting the Unruh effect through these phenomena is also discussed in detail.

  8. Voltage-pulsed and laser-pulsed atom probe tomography of a multiphase high-strength low-carbon steel.

    Science.gov (United States)

    Mulholland, Michael D; Seidman, David N

    2011-12-01

    The differences in artifacts associated with voltage-pulsed and laser-pulsed (wavelength = 532 or 355 nm) atom-probe tomographic (APT) analyses of nanoscale precipitation in a high-strength low-carbon steel are assessed using a local-electrode atom-probe tomograph. It is found that the interfacial width of nanoscale Cu precipitates increases with increasing specimen apex temperatures induced by higher laser pulse energies (0.6-2 nJ pulse(-1) at a wavelength of 532 nm). This effect is probably due to surface diffusion of Cu atoms. Increasing the specimen apex temperature by using pulse energies up to 2 nJ pulse(-1) at a wavelength of 532 nm is also found to increase the severity of the local magnification effect for nanoscale M2C metal carbide precipitates, which is indicated by a decrease of the local atomic density inside the carbides from 68 ± 6 nm(-3) (voltage pulsing) to as small as 3.5 ± 0.8 nm(-3). Methods are proposed to solve these problems based on comparisons with the results obtained from voltage-pulsed APT experiments. Essentially, application of the Cu precipitate compositions and local atomic density of M2C metal carbide precipitates measured by voltage-pulsed APT to 532 or 355 nm wavelength laser-pulsed data permits correct quantification of precipitation.

  9. Atomic structure and surface defects at mineral-water interfaces probed by in situ atomic force microscopy.

    Science.gov (United States)

    Siretanu, Igor; van den Ende, Dirk; Mugele, Frieder

    2016-04-21

    Atomic scale details of surface structure play a crucial role for solid-liquid interfaces. While macroscopic characterization techniques provide averaged information about bulk and interfaces, high resolution real space imaging reveals unique insights into the role of defects that are believed to dominate many aspects of surface chemistry and physics. Here, we use high resolution dynamic Atomic Force Microscopy (AFM) to visualize and characterize in ambient water the morphology and atomic scale structure of a variety of nanoparticles of common clay minerals adsorbed to flat solid surfaces. Atomically resolved images of the (001) basal planes are obtained on all materials investigated, namely gibbsite, kaolinite, illite, and Na-montmorillonite of both natural and synthetic origin. Next to regions of perfect crystallinity, we routinely observe extended regions of various types of defects on the surfaces, including vacancies of one or few atoms, vacancy islands, atomic steps, apparently disordered regions, as well as strongly adsorbed seemingly organic and inorganic species. While their exact nature is frequently difficult to identify, our observations clearly highlight the ubiquity of such defects and their relevance for the overall physical and chemical properties of clay nanoparticle-water interfaces.

  10. Entanglement in Three-Atom Tavis-Cummings Model Induced by a Thermal Field

    Institute of Scientific and Technical Information of China (English)

    CAI Jin-Fang; LIU Hui-Ping

    2005-01-01

    The explicit form of the evolution operator for the three-atom Tavis-Cummings model is given. The atoms can be entangled through their interaction with a thermal field. The degree of entanglement depends on the mean photon number of the thermal field and the initial state of the atoms.

  11. Atom probe study of sodium distribution in polycrystalline Cu(In,Ga)Se{sub 2} thin film

    Energy Technology Data Exchange (ETDEWEB)

    Cadel, E. [Groupe de Physique des Materiaux (GPM), UMR 6634 CNRS, Avenue de l' Universite BP 12, 76801 Saint Etienne de Rouvray (France); Barreau, N., E-mail: nicolas.barreau@univ-nantes.fr [Institut des Materiaux Jean Rouxel (IMN), UMR 6502 CNRS, 2 rue de la Houssiniere BP 32229, 44322 Nantes cedex 3 (France); Kessler, J. [Institut des Materiaux Jean Rouxel (IMN), UMR 6502 CNRS, 2 rue de la Houssiniere BP 32229, 44322 Nantes cedex 3 (France); Pareige, P. [Groupe de Physique des Materiaux (GPM), UMR 6634 CNRS, Avenue de l' Universite BP 12, 76801 Saint Etienne de Rouvray (France)

    2010-04-15

    This article reports the first investigations of CuIn{sub 1-x}Ga{sub x}Se{sub 2} (CIGSe) polycrystalline thin films by means of atom probe tomography. Attention is focused on the distribution of Na atoms within the films. Both Na-containing and Na-free CIGSe thin films have been investigated. When Na is available during the CIGSe coevaporation, it is observed to be mainly segregated at the grain boundaries of the films; however, it is also detected within the grains of CIGSe at very low concentration.

  12. Near-field optical microscopy of localized excitations on rough surfaces: influence of a probe

    DEFF Research Database (Denmark)

    Bozhevolnyi, Sergey I.

    1999-01-01

    Starting from the general principles of near-field optical microscopy. I consider the influence of a probe when being used to image localized dipolar excitations and suggest a way of evaluating the perturbation thus introduced. Using the rigorous microscopic (electric) point-dipole description, I...... calculate the self consistent field intensity at the site of a probe dipole scanning over resonantly interacting object dipoles and show that the intensity distribution deviates from that existing in the absence of a probe. I demonstrate that this difference increases with an increase in the polarizability...... of the probe dipole, resulting eventually in a completely different intensity distribution, The calculations also show that the perturbation of the intensity distribution due to the presence of a probe decreases with an increase in the probe-sample distance. In order to evaluate the degree of perturbation, I...

  13. Preparation of Multicomponent Schr(o)dinger Cat States Through Resonant Atom-Field Interaction

    Institute of Scientific and Technical Information of China (English)

    ZHENG Shi-Biao

    2005-01-01

    A simple method is presented for generating multicomponent Schrodinger cat states through resonant atom-field interactions. In the scheme n two-level atoms, initially in ground states, are sent through a resonant cavity filled with a strong coherent field sequentially. Then state-selective measurements are performed on the atoms. The detections of the atoms in ground states collapse the cavity field onto a superposition of 2n coherent states. This is the first way for producing superpositions of many coherent states through resonant atom-field interaction.

  14. Inversion symmetry breaking of atomic bound states in strong and short laser fields

    CERN Document Server

    Stooß, Veit; Ott, Christian; Blättermann, Alexander; Ding, Thomas; Pfeifer, Thomas

    2015-01-01

    In any atomic species, the spherically symmetric potential originating from the charged nucleus results in fundamental symmetry properties governing the structure of atomic states and transition rules between them. If atoms are exposed to external electric fields, these properties are modified giving rise to energy shifts such as the AC Stark-effect in varying fields and, contrary to this in a constant (DC) electric field for high enough field strengths, the breaking of the atomic symmetry which causes fundamental changes in the atom's properties. This has already been observed for atomic Rydberg states with high principal quantum numbers. Here, we report on the observation of symmetry breaking effects in Helium atoms for states with principal quantum number n=2 utilizing strong visible laser fields. These findings were enabled by temporally resolving the dynamics better than the sub-optical cycle of the applied laser field, utilizing the method of attosecond transient absorption spectroscopy (ATAS). We ident...

  15. Field-emission spectroscopy of beryllium atoms adsorbed on tungsten

    Energy Technology Data Exchange (ETDEWEB)

    Czyzewski, J.J.; Grzesiak, W.; Krajniak, J. (Politechnika Wroclawska (Poland))

    1981-01-01

    Field emission energy distributions (FEED) have been measured for the beryllium-tungsten (023) adsorption system over the 78-450 K temperature range. A temperature dependence of the normalized half-width, ..delta../d, of FEED peaks changed significantly due to beryllium adsorption; and the curve, ..delta../d vs p, for the Be/W adsorption system was identical in character to the calculated curve based on the free electron model in contrast to the curve for the clean tungsten surface. In the last part of this paper Gadzuk's theory of the resonance-tunneling effect is applied to the beryllium atom on tungsten. Experimental and theoretical curves of the enhancement factor as a function of energy have been discussed.

  16. Modelling laser-atom interactions in the strong field regime

    CERN Document Server

    Galstyan, A; Mota-Furtado, F; O'Mahony, P F; Janssens, N; Jenkins, S D; Chuluunbaatar, O; Piraux, B

    2016-01-01

    We consider the ionisation of atomic hydrogen by a strong infrared field. We extend and study in more depth an existing semi-analytical model. Starting from the time-dependent Schroedinger equation in momentum space and in the velocity gauge we substitute the kernel of the non-local Coulomb potential by a sum of N separable potentials, each of them supporting one hydrogen bound state. This leads to a set of N coupled one-dimensional linear Volterra integral equations to solve. We analyze the gauge problem for the model, the different ways of generating the separable potentials and establish a clear link with the strong field approximation which turns out to be a limiting case of the present model. We calculate electron energy spectra as well as the time evolution of electron wave packets in momentum space. We compare and discuss the results obtained with the model and with the strong field approximation and examine in this context, the role of excited states.

  17. Investigation of material property influenced stoichiometric deviations as evidenced during UV laser-assisted atom probe tomography in fluorite oxides

    Energy Technology Data Exchange (ETDEWEB)

    Valderrama, Billy; Henderson, Hunter B. [Department of Materials Science and Engineering, University of Florida, 100 Rhines Hall, Gainesville, FL 32611 (United States); Yablinsky, Clarissa A. [Department of Nuclear Engineering, University of Wisconsin-Madison, 921 ERB, 1500 Engineering Drive, Madison, WI 53706 (United States); Gan, Jian [Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415 (United States); Allen, Todd R. [Department of Nuclear Engineering, University of Wisconsin-Madison, 921 ERB, 1500 Engineering Drive, Madison, WI 53706 (United States); Idaho National Laboratory, P.O. Box 1625, Idaho Falls, ID 83415 (United States); Manuel, Michele V., E-mail: mmanuel@mse.ufl.edu [Department of Materials Science and Engineering, University of Florida, 100 Rhines Hall, Gainesville, FL 32611 (United States)

    2015-09-15

    Oxide materials are used in numerous applications such as thermal barrier coatings, nuclear fuels, and electrical conductors and sensors, all applications where nanometer-scale stoichiometric changes can affect functional properties. Atom probe tomography can be used to characterize the precise chemical distribution of individual species and spatially quantify the oxygen to metal ratio at the nanometer scale. However, atom probe analysis of oxides can be accompanied by measurement artifacts caused by laser-material interactions. In this investigation, two technologically relevant oxide materials with the same crystal structure and an anion to cation ratio of 2.00, pure cerium oxide (CeO{sub 2}) and uranium oxide (UO{sub 2}) are studied. It was determined that electronic structure, optical properties, heat transfer properties, and oxide stability strongly affect their evaporation behavior, thus altering their measured stoichiometry, with thermal conductance and thermodynamic stability being strong factors.

  18. Using Atom-Probe Tomography to Understand Zn O ∶Al /SiO 2/Si Schottky Diodes

    Science.gov (United States)

    Jaramillo, R.; Youssef, Amanda; Akey, Austin; Schoofs, Frank; Ramanathan, Shriram; Buonassisi, Tonio

    2016-09-01

    We use electronic transport and atom-probe tomography to study Zn O ∶Al /SiO 2/Si Schottky diodes on lightly doped n - and p -type Si. We vary the carrier concentration in the ZnO ∶Al films by 2 orders of magnitude, but the Schottky barrier height remains nearly constant. Atom-probe tomography shows that Al segregates to the interface, so that the ZnO ∶Al at the junction is likely to be metallic even when the bulk of the ZnO ∶Al film is semiconducting. We hypothesize that the observed Fermi-level pinning is connected to the insulator-metal transition in doped ZnO. This implies that tuning the band alignment at oxide/Si interfaces may be achieved by controlling the transition between localized and extended states in the oxide, thereby changing the orbital hybridization across the interface.

  19. Analysis of Radiation Damage in Light Water Reactors: Comparison of Cluster Analysis Methods for the Analysis of Atom Probe Data.

    Science.gov (United States)

    Hyde, Jonathan M; DaCosta, Gérald; Hatzoglou, Constantinos; Weekes, Hannah; Radiguet, Bertrand; Styman, Paul D; Vurpillot, Francois; Pareige, Cristelle; Etienne, Auriane; Bonny, Giovanni; Castin, Nicolas; Malerba, Lorenzo; Pareige, Philippe

    2017-01-30

    Irradiation of reactor pressure vessel (RPV) steels causes the formation of nanoscale microstructural features (termed radiation damage), which affect the mechanical properties of the vessel. A key tool for characterizing these nanoscale features is atom probe tomography (APT), due to its high spatial resolution and the ability to identify different chemical species in three dimensions. Microstructural observations using APT can underpin development of a mechanistic understanding of defect formation. However, with atom probe analyses there are currently multiple methods for analyzing the data. This can result in inconsistencies between results obtained from different researchers and unnecessary scatter when combining data from multiple sources. This makes interpretation of results more complex and calibration of radiation damage models challenging. In this work simulations of a range of different microstructures are used to directly compare different cluster analysis algorithms and identify their strengths and weaknesses.

  20. Characterization of nano-sized precipitates in a Mn-based lean maraging steel by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Millan, J.; Ponge, D.; Raabe, D.; Choi, P.; Dmitrieva, O. [Max-Planck-Institut fuer Eisenforschung, Duesseldorf (Germany)

    2011-02-15

    We present atom probe tomography results of a precipitation-hardened Mn-based maraging steel (9 Mn, 1.9 Ni, 0.6 Mo, 1.1 Ti, 0.33 Al; in at.%). The alloy is characterized by the surprising effect that both, strength and total elongation increase upon aging. The material reveals a high ultimate tensile strength (UTS) up to 1 GPa and good ductility (total elongation (TE) of up to 15% in a tensile test) depending on aging conditions. We map the evolution of the precipitates after 450 C aging treatment using atom probe tomography in terms of chemical composition and size distribution. (Copyright copyright 2011 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  1. Probing the interactions between lignin and inorganic oxides using atomic force microscopy

    Science.gov (United States)

    Wang, Jingyu; Qian, Yong; Deng, Yonghong; Liu, Di; Li, Hao; Qiu, Xueqing

    2016-12-01

    Understanding the interactions between lignin and inorganic oxides has both fundamental and practical importance in industrial and energy fields. In this work, the specific interactions between alkali lignin (AL) and three inorganic oxide substrates in aqueous environment are quantitatively measured using atomic force microscopy (AFM). The results show that the average adhesion force between AL and metal oxide such as Al2O3 or MgO is nearly two times bigger than that between AL and nonmetal oxide such as SiO2 due to the electrostatic difference and cation-π interaction. When 83% hydroxyl groups of AL is blocked by acetylation, the adhesion forces between AL and Al2O3, MgO and SiO2 decrease 43, 35 and 75% respectively, which indicate hydrogen bonds play an important role between AL and inorganic oxides, especially in AL-silica system.

  2. Morphology and current-voltage characteristics of nanostructured pentacene thin films probed by atomic force microscopy.

    Science.gov (United States)

    Zorba, S; Le, Q T; Watkins, N J; Yan, L; Gao, Y

    2001-09-01

    Atomic force microscopy was used to study the growth modes (on SiO2, MoS2, and Au substrates) and the current-voltage (I-V) characteristics of organic semiconductor pentacene. Pentacene films grow on SiO2 substrate in a layer-by-layer manner with full coverage at an average thickness of 20 A and have the highest degree of molecular ordering with large dendritic grains among the pentacene films deposited on the three different substrates. Films grown on MoS2 substrate reveal two different growth modes, snowflake-like growth and granular growth, both of which seem to compete with each other. On the other hand, films deposited on Au substrate show granular structure for thinner coverages (no crystal structure) and dendritic growth for higher coverages (crystal structure). I-V measurements were performed with a platinum tip on a pentacene film deposited on a Au substrate. The I-V curves on pentacene film reveal symmetric tunneling type character. The field dependence of the current indicates that the main transport mechanism at high field intensities is hopping (Poole-Frenkel effect). From these measurements, we have estimated a field lowering coefficient of 9.77 x 10(-6) V-1/2 m1/2 and an ideality factor of 18 for pentacene.

  3. THE EXACT SOLUTION OF A TWO-LEVEL ATOM MOVING IN A QUANTIZED TRAVELLING LIGHT FIELD AND A GRAVITATIONAL FIELD

    Institute of Scientific and Technical Information of China (English)

    邹旭波; 许晶波; 高孝纯; 符建

    2001-01-01

    We adopt a dynamical algebraic approach to study the system of a two-level atom moving in a quantized travelling light field and a gravitational field with a multiphoton interaction. The exact solution of the system is obtained and used to discuss the influence of the gravitational field on the collapses and revivals of atomic population, sub-Poissonian statistics.

  4. Near-field fluorescence thermometry using highly efficient triple-tapered near-field optical fiber probe

    Science.gov (United States)

    Fujii, T.; Taguchi, Y.; Saiki, T.; Nagasaka, Y.

    2012-12-01

    A novel local temperature measurement method using fluorescence near-field optics thermal nanoscopy (Fluor-NOTN) has been developed. Fluor-NOTN enables nanoscale temperature measurement in situ by detecting the temperature-dependent fluorescence lifetime of CdSe quantum dots (QDs). In this paper, we report a novel triple-tapered near-field optical fiber probe that can increase the temperature measurement sensitivity of Fluor-NOTN. The performance of the proposed probe was numerically evaluated by the finite difference time domain method. Due to improvements in both the throughput and collection efficiency of near-field light, the sensitivity of the proposed probe was 1.9 times greater than that of typical double-tapered probe. The proposed shape of the triple-tapered core was successfully fabricated utilizing a geometrical model. The detected signal intensity of dried layers of QDs was greater by more than two orders than that of auto-fluorescence from the fiber core. In addition, the near-field fluorescence lifetime of the QDs and its temperature dependence were successfully measured by the fabricated triple-tapered near-field optical fiber probe. These measurement results verified the capability of the proposed triple-tapered near-field optical fiber probe to improve the collection efficiency of near-field fluorescence.

  5. Laser-assisted atom probe tomography of Ti/TiN films deposited on Si.

    Science.gov (United States)

    Sanford, N A; Blanchard, P T; White, R; Vissers, M R; Diercks, D R; Davydov, A V; Pappas, D P

    2017-03-01

    Laser-assisted atom probe tomography (L-APT) was used to examine superconducting TiN/Ti/TiN trilayer films with nominal respective thicknesses of 5/5/5 (nm). Such materials are of interest for applications that require large arrays of microwave kinetic inductance detectors. The trilayers were deposited on Si substrates by reactive sputtering. Electron energy loss microscopy performed in a scanning transmission electron microscope (STEM/EELS) was used to corroborate the L-APT results and establish the overall thicknesses of the trilayers. Three separate batches were studied where the first (bottom) TiN layer was deposited at 500°C (for all batches) and the subsequent TiN/Ti bilayer was deposited at ambient temperature, 250°C, and 500°C, respectively. L-APT rendered an approximately planar TiN/Si interface by making use of plausible mass-spectral assignments to N3(1+), SiN(1+), and SiO(1+). This was necessary since ambiguities associated with the likely simultaneous occurrence of Si(1+) and N2(1+) prevented their use in rendering the TiN/Si interface upon reconstruction. The non-superconducting Ti2N phase was also revealed by L-APT. Neither L-APT nor STEM/EELS rendered sharp Ti/TiN interfaces and the contrast between these layers diminished with increased film deposition temperature. L-APT also revealed that hydrogen was present in varying degrees in all samples including control samples that were composed of single layers of Ti or TiN.

  6. Atom probe tomography investigation of lath boundary segregation and precipitation in a maraging stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Thuvander, Mattias, E-mail: mattias.thuvander@chalmers.se [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden); Andersson, Marcus [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden); R and D Centre, Sandvik Materials Technology, SE-811 81 Sandviken (Sweden); Stiller, Krystyna [Department of Applied Physics, Chalmers University of Technology, SE-412 96 Göteborg (Sweden)

    2013-09-15

    Lath boundaries in a maraging stainless steel of composition 13Cr–8Ni–2Mo–2Cu–1Ti–0.7Al–0.3Mn–0.2Si–0.03C (at%) have been investigated using atom probe tomography following aging at 475 °C for up to 100 h. Segregation of Mo, Si and P to the lath boundaries was observed already after 5 min of aging, and the amount of segregation increases with aging time. At lath boundaries also precipitation of η-Ni{sub 3}(Ti, Al) and Cu-rich 9R, in contact with each other, takes place. These co-precipitates grow with time and because of coarsening the area number density decreases. After 100 h of aging a ∼5 nm thick film-like precipitation of a Mo-rich phase was observed at the lath boundaries. From the composition of the film it is suggested that the phase in question is the quasicrystalline R′ phase. The film is perforated with Cu-rich 9R and η-Ni{sub 3}(Ti, Al) co-precipitates. Not all precipitate types present in the matrix do precipitate at the lath boundaries; the Si-containing G phase and γ′-Ni{sub 3}(Ti, Al, Si) and the Cr-rich α′ phase were not observed at the lath boundaries. - Highlights: ► Lath boundaries in a maraging steel were analyzed by APT. ► Segregation of Mo, Si and P was measured. ► Precipitation of η-Ni{sub 3}(Ti, Al) and Cu-rich 9R was observed. ► After 100 h of aging a quasicrystalline Mo-rich film was observed.

  7. Tunnelling of Two-Level Atoms in Two-Photon Mazer:Atomic Coherence Effect and Statistics of Cavity Fields

    Institute of Scientific and Technical Information of China (English)

    何小灵; 杜四德; 周鲁卫; 汪启胜; 陈灏

    2004-01-01

    Tunnelling of a two-level atom is investigated in the two-photon mazer when the atom is initially prepared in a coherent superposition state and the cavity in various quantum states. For a strong coherent field, the tunnelling exhibits more regular oscillations but less remarkable switch effect than that in the one-photon mazer. It is discovered that in the presence of atomic coherence, the transmission probabilities in the ultracold regime are significantly different when the cavity field is initially in coherent, squeezed vacuum, even cat and odd cat states,respectively.

  8. Atom-field entanglement in two-atom Jaynes-Cummings model with intensity-dependent coupling

    OpenAIRE

    Bashkirov, E. K.

    2014-01-01

    An exact solution of the problem of two-atom one- and two-mode Jaynes-Cummings model with intensity-dependent coupling is presented. Asymptotic solutions for system state vectors are obtained in the approximation of large initial coherent fields. The atom-field entanglement is investigated on the basis of the reduced atomic entropy dynamics. The possibility of the system being initially in a pure disentangled state to revive into this state during the evolution process for both models is show...

  9. Atomic Spectrum in Ramsey Separated Oscillating Fields with Three Interaction Regions

    Institute of Scientific and Technical Information of China (English)

    CHEN Jingbiao; WANG Fengzhi; YANG Donghai; WANG YiQiu

    2001-01-01

    Comparing with the situation of Ramsey separated oscillating fields used in Cesium atomic beam frequency standard, the transition probability spectrum of two-level atoms in the Ramsey separated oscillating fields with three interaction regions has been derived under the condition of near resonance. The new characteristic of atomic spectrum with excessive microwave power was analyzed in detail. Meantime, the predicted new characteristic of atomic spectrum was confirmed by numerical method in this paper.

  10. A Feasibility Study of UV Laser Assisted 3D-Atom Probe Analysis of AlGaN/GaN HEMTs

    Science.gov (United States)

    2013-03-05

    Final Report for AOARD Grant-FA2386-11-1-4031 “A feasibility study of UV laser assisted 3D-atom probe analysis of AlGaN/ GaN HEMTs ” March 5...20-06-2011 to 19-06-2012 4. TITLE AND SUBTITLE A feasibility study of UV laser assisted 3D-atom probe analysis of AlGaN/ GaN HEMTs 5a. CONTRACT...gate region (gate metal, interfacial layer and defects, and AlGaN/ GaN epilayers) of an AFRL HEMT using laser assisted 3-D atom probe (3DAP

  11. Diamond-modified AFM probes: from diamond nanowires to atomic force microscopy-integrated boron-doped diamond electrodes.

    Science.gov (United States)

    Smirnov, Waldemar; Kriele, Armin; Hoffmann, René; Sillero, Eugenio; Hees, Jakob; Williams, Oliver A; Yang, Nianjun; Kranz, Christine; Nebel, Christoph E

    2011-06-15

    In atomic force microscopy (AFM), sharp and wear-resistant tips are a critical issue. Regarding scanning electrochemical microscopy (SECM), electrodes are required to be mechanically and chemically stable. Diamond is the perfect candidate for both AFM probes as well as for electrode materials if doped, due to diamond's unrivaled mechanical, chemical, and electrochemical properties. In this study, standard AFM tips were overgrown with typically 300 nm thick nanocrystalline diamond (NCD) layers and modified to obtain ultra sharp diamond nanowire-based AFM probes and probes that were used for combined AFM-SECM measurements based on integrated boron-doped conductive diamond electrodes. Analysis of the resonance properties of the diamond overgrown AFM cantilevers showed increasing resonance frequencies with increasing diamond coating thicknesses (i.e., from 160 to 260 kHz). The measured data were compared to performed simulations and show excellent correlation. A strong enhancement of the quality factor upon overgrowth was also observed (120 to 710). AFM tips with integrated diamond nanowires are shown to have apex radii as small as 5 nm and where fabricated by selectively etching diamond in a plasma etching process using self-organized metal nanomasks. These scanning tips showed superior imaging performance as compared to standard Si-tips or commercially available diamond-coated tips. The high imaging resolution and low tip wear are demonstrated using tapping and contact mode AFM measurements by imaging ultra hard substrates and DNA. Furthermore, AFM probes were coated with conductive boron-doped and insulating diamond layers to achieve bifunctional AFM-SECM probes. For this, focused ion beam (FIB) technology was used to expose the boron-doped diamond as a recessed electrode near the apex of the scanning tip. Such a modified probe was used to perform proof-of-concept AFM-SECM measurements. The results show that high-quality diamond probes can be fabricated, which are

  12. Magnetic-field-driven localization of light in a cold-atom gas

    CERN Document Server

    Skipetrov, S E

    2014-01-01

    We discover a transition from extended to localized quasi-modes for light in a gas of immobile two-level atoms in a magnetic field. The transition takes place either upon increasing the number density of atoms in a strong field or upon increasing the field at a high enough density. It has many characteristic features of a disorder-driven (Anderson) transition but is strongly influenced by near-field interactions between atoms and the anisotropy of the atomic medium induced by the magnetic field.

  13. Atom probe tomography and transmission electron microscopy of a Mg-doped AlGaN/GaN superlattice

    Energy Technology Data Exchange (ETDEWEB)

    Bennett, S.E., E-mail: sb534@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom); Ulfig, R.M.; Clifton, P.H. [Imago Scientific Instruments Corporation, 5500 Nobel Drive, Madison, WI 53711 (United States); Kappers, M.J.; Barnard, J.S.; Humphreys, C.J.; Oliver, R.A. [Department of Materials Science and Metallurgy, University of Cambridge, Pembroke Street, Cambridge CB2 3QZ (United Kingdom)

    2011-02-15

    The electronic characteristics of semiconductor-based devices are greatly affected by the local dopant atom distribution. In Mg-doped GaN, the clustering of dopants at structural defects has been widely reported, and can significantly affect p-type conductivity. We have studied a Mg-doped AlGaN/GaN superlattice using transmission electron microscopy (TEM) and atom probe tomography (APT). Pyramidal inversion domains were observed in the TEM and the compositional variations of the dopant atoms associated with those defects have been studied using APT. Rarely has APT been used to assess the compositional variations present due to structural defects in semiconductors. Here, TEM and APT are used in a complementary fashion, and the strengths and weaknesses of the two techniques are compared. -- Research Highlights: {yields} Mg-rich regions of approximately 5 nm in size were revealed in Mg-doped AlGaN/GaN superlattices using atom probe tomography (APT). {yields} Transmission electron microscopy (TEM) of the superlattice sample showed pyramidal inversion domains, concluded to be the same Mg-rich features observed by APT. {yields} The information gained from both the 3D APT study and the 2D TEM characterisation was then compared to determine the strengths and weaknesses of each technique in analysing nanoscale features in nitride materials.

  14. Probing the properties of quantum matter; an experimental study in three parts using ultracold atoms

    NARCIS (Netherlands)

    Bons, P.C.

    2015-01-01

    The three experiments described in this thesis investigate fundamental properties of ultracold atoms. Using laser cooling and evaporative cooling, a dilute gas of sodium atoms is cooled to ~100 nK. Under these circumstances a Bose-Einstein condensate (BEC) forms, where millions of atoms collapse int

  15. Coke Formation in a Zeolite Crystal During the Methanol-to-Hydrocarbons Reaction as Studied with Atom Probe Tomography.

    Science.gov (United States)

    Schmidt, Joel E; Poplawsky, Jonathan D; Mazumder, Baishakhi; Attila, Özgün; Fu, Donglong; de Winter, D A Matthijs; Meirer, Florian; Bare, Simon R; Weckhuysen, Bert M

    2016-09-01

    Understanding the formation of carbon deposits in zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, atom probe tomography (APT) has been used to spatially resolve the 3D compositional changes at the sub-nm length scale in a single zeolite ZSM-5 crystal, which has been partially deactivated by the methanol-to-hydrocarbons reaction using (13) C-labeled methanol. The results reveal the formation of coke in agglomerates that span length scales from tens of nanometers to atomic clusters with a median size of 30-60 (13) C atoms. These clusters correlate with local increases in Brønsted acid site density, demonstrating that the formation of the first deactivating coke precursor molecules occurs in nanoscopic regions enriched in aluminum. This nanoscale correlation underscores the importance of carefully engineering materials to suppress detrimental coke formation.

  16. The time resolved measurement of ultrashort terahertz-band electric fields without an ultrashort probe

    Energy Technology Data Exchange (ETDEWEB)

    Walsh, D. A., E-mail: david.walsh@stfc.ac.uk; Snedden, E. W. [Accelerator Science and Technology Centre, STFC Daresbury National Laboratory, Warrington WA4 4AD (United Kingdom); Jamison, S. P. [Accelerator Science and Technology Centre, STFC Daresbury National Laboratory, Warrington WA4 4AD (United Kingdom); Photon Science Institute, The University of Manchester, Manchester M13 9PL (United Kingdom)

    2015-05-04

    The time-resolved detection of ultrashort pulsed THz-band electric field temporal profiles without an ultrashort laser probe is demonstrated. A non-linear interaction between a narrow-bandwidth optical probe and the THz pulse transposes the THz spectral intensity and phase information to the optical region, thereby generating an optical pulse whose temporal electric field envelope replicates the temporal profile of the real THz electric field. This optical envelope is characterised via an autocorrelation based FROG (frequency resolved optical gating) measurement, hence revealing the THz temporal profile. The combination of a narrow-bandwidth, long duration, optical probe, and self-referenced FROG makes the technique inherently immune to timing jitter between the optical probe and THz pulse and may find particular application where the THz field is not initially generated via ultrashort laser methods, such as the measurement of longitudinal electron bunch profiles in particle accelerators.

  17. The time resolved measurement of ultrashort THz-band electric fields without an ultrashort probe

    CERN Document Server

    Walsh, David A; Jamison, Steven P

    2015-01-01

    The time-resolved detection of ultrashort pulsed THz-band electric field temporal profiles without an ultrashort laser probe is demonstrated. A non-linear interaction between a narrow-bandwidth optical probe and the THz pulse transposes the THz spectral intensity and phase information to the optical region, thereby generating an optical pulse whose temporal electric field envelope replicates the temporal profile of the real THz electric field. This optical envelope is characterised via an autocorrelation based FROG measurement, hence revealing the THz temporal profile. The combination of a narrow-bandwidth, long duration, optical probe and self-referenced FROG makes the technique inherently immune to timing jitter between the optical probe and THz pulse, and may find particular application where the THz field is not initially generated via ultrashort laser methods, such as the measurement of longitudinal electron bunch profiles in particle accelerators.

  18. APPROXIMATE MODEL OF INTENSE FIELD STABILIZATION FOR.HYDlROGEN ATOM

    Institute of Scientific and Technical Information of China (English)

    XIE BAI-SONG

    2000-01-01

    An approximate model is proposed to study the stabilization problem of hydrogen atoms under monochromatic intense laser field.The stabilization regime for system parameters such as laser field strength,laser field frequency and atomic magnetic quantum number are obtained by stability analysis of fixed points of the model.The results are consistent with those obtained by other methods.

  19. Measuring Motion-Induced B0-Fluctuations in the Brain Using Field Probes

    DEFF Research Database (Denmark)

    Andersen, Mads; Hanson, Lars G.; Madsen, Kristoffer Hougaard;

    2016-01-01

    Purpose: Fluctuations of the background magnetic field (B0) due to body and breathing motion can lead to significant artifacts in brain imaging at ultrahigh field. Corrections based on real-time sensing using external field probes show great potential. This study evaluates different aspects of fi...

  20. Analysis of Omni-directivity Error of Electromagnetic Field Probe using Isotropic Antenna

    Science.gov (United States)

    Hartansky, Rene

    2016-12-01

    This manuscript analyzes the omni-directivity error of an electromagnetic field (EM) probe and its dependence on frequency. The global directional characteristic of a whole EM probe consists of three independent directional characteristics of EM sensors - one for each coordinate. The shape of particular directional characteristics is frequency dependent and so is the shape of the whole EM probe's global directional characteristic. This results in systematic error induced in the measurement of EM fields. This manuscript also contains quantitative formulation of such errors caused by the shape change of directional characteristics for different types of sensors depending on frequency and their mutual arrangement.

  1. Fictitious magnetic field gradients in optical microtraps as an experimental tool for interrogating and manipulating cold atoms

    CERN Document Server

    Albrecht, Bernhard; Clausen, Christoph; Dareau, Alexandre; Schneeweiss, Philipp; Rauschenbeutel, Arno

    2016-01-01

    Optical microtraps provide a strong spatial confinement for laser-cooled atoms. They can, e.g., be realized with strongly focused trapping light beams or the optical near fields of nano-scale waveguides and photonic nanostructures. Atoms in such traps often experience strongly spatially varying AC Stark shifts which are proportional to the magnetic quantum number of the respective energy level. These inhomogeneous fictitious magnetic fields can cause a displacement of the trapping potential that depends on the Zeeman state. Hitherto, this effect was mainly perceived as detrimental. However, it also provides a means to probe and to manipulate the motional state of the atoms in the trap by driving transitions between Zeeman states. Furthermore, by applying additional real or fictitious magnetic fields, the state-dependence of the trapping potential can be controlled. Here, using laser-cooled atoms that are confined in a nanofiber-based optical dipole trap, we employ this control in order to tune the microwave c...

  2. Effects of a static electric field on two-color photoassociation of heteronuclear atom-pairs

    CERN Document Server

    Chakraborty, Debashree

    2013-01-01

    We study non-perturbative effects of a static electric field on two-color photoassociation of heteronuclear atom-pairs. A static electric field induces anisotropy in scattering between two heteronuclear atoms and hybridizes field-free rotational states of heteronuclear dimers or polar molecules. In a previous paper [D. Chakraborty $\\it {et.}$ $\\it {al.}$, J. Phys. B 44, 095201 (2011)], the effects of a static electric field on one-color photoassociation between heteronuclear 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 heteronuclear 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 scatt...

  3. Standard Practices for Usage of Inductive Magnetic Field Probes with Application to Electric Propulsion Testing

    Science.gov (United States)

    Polzin, Kurt A.; Hill, Carrie S.

    2013-01-01

    Inductive magnetic field probes (also known as B-dot probes and sometimes as B-probes or magnetic probes) are useful for performing measurements in electric space thrusters and various plasma accelerator applications where a time-varying magnetic field is present. Magnetic field probes have proven to be a mainstay in diagnosing plasma thrusters where changes occur rapidly with respect to time, providing the means to measure the magnetic fields produced by time-varying currents and even an indirect measure of the plasma current density through the application of Ampère's law. Examples of applications where this measurement technique has been employed include pulsed plasma thrusters and quasi-steady magnetoplasmadynamic thrusters. The Electric Propulsion Technical Committee (EPTC) of the American Institute of Aeronautics and Astronautics (AIAA) was asked to assemble a Committee on Standards (CoS) for Electric Propulsion Testing. The assembled CoS was tasked with developing Standards and Recommended Practices for various diagnostic techniques used in the evaluation of plasma thrusters. These include measurements that can yield either global information related to a thruster and its performance or detailed, local data related to the specific physical processes occurring in the plasma. This paper presents a summary of the standard, describing the preferred methods for fabrication, calibration, and usage of inductive magnetic field probes for use in diagnosing plasma thrusters. Inductive magnetic field probes (also called B-dot probes throughout this document) are commonly used in electric propulsion (EP) research and testing to measure unsteady magnetic fields produced by time-varying currents. The B-dot probe is relatively simple in construction, and requires minimal cost, making it a low-cost technique that is readily accessible to most researchers. While relatively simple, the design of a B-dot probe is not trivial and there are many opportunities for errors in

  4. Semiclassical calculation of ionisation rate for Rydberg helium atoms in an electric field

    Institute of Scientific and Technical Information of China (English)

    Wang De-Hua

    2011-01-01

    The ionisation of Rydberg helium atoms in an electric field above the classical ionisation threshold has been examined using the semiclassical method, with particular emphasis on discussing the influence of the core scattering on the escape dynamics of electrons. The results show that the Rydberg helium atoms ionise by emitting a train of electron pulses. Unlike the case of the ionisation of Rydberg hydrogen atom in parallel electric and magnetic fields,where the pulses of the electron are caused by the external magnetic field, the pulse trains for Rydberg helium atoms are created through core scattering. Each peak in the ionisation rate corresponds to the contribution of one core-scattered combination trajectory. This fact further illustrates that the ionic core scattering leads to the chaotic property of the Rydberg helium atom in external fields. Our studies provide a simple explanation for the escape dynamics in the ionisation of nonhydrogenic atoms in external fields.

  5. Composite particle and field theory in atomic quantum Hall effect

    Institute of Scientific and Technical Information of China (English)

    Zhao Bo; Chen Zeng-Bing

    2005-01-01

    In this paper, we explore the composite particle description of the atomic quantum Hall (QH) effect. We further give the Chern-Simon-Gross-Pitaevskii (CSGP) effective theory for the atomic Hall liquid, which is the counterpart of Chern-Simon theory in electron Hall effect. What we obtained is equivalent to the Laughlin wavefunction approach.Our results show that in terms of composite particles, the atomic Hall effect is really the same as the electronic QH effect. The CSGP effective theory would shed new light on the atomic QH effect.

  6. A Filtering Method to Reveal Crystalline Patterns from Atom Probe Microscopy Desorption Maps

    Science.gov (United States)

    2016-03-26

    between their evaporation and the evaporation of the previous atom . Since this time difference correlates with the location and the local structure of...APM is the only technique providing 3D atomic -scale composition information. However the amount of structural information can often be limited by...shape, the actual apex surface is not continuously smooth and presents some roughness due to the atomic nature of the surface structures . This results

  7. Measurement of the magnetic field profile in the atomic fountain clock FoCS-2 using Zeeman spectroscopy

    CERN Document Server

    Laurent, Devenoges; André, Stefanov; Antoine, Jallageas; Jacques, Morel; Thomas, Südmeyer; Pierre, Thomann

    2016-01-01

    We report the evaluation of the second order Zeeman shift in the continuous atomic fountain clock FoCS-2. Because of the continuous operation and its geometrical constraints, the methods used in pulsed fountain are not applicable. We use here time-resolved Zeeman spectroscopy to probe the magnetic field profile in the clock. The pulses of ac magnetic excitation allow us to measure the Zeeman frequency with spatial resolution and to evaluate the Zeeman shift with an uncertainty smaller than 10E-16 in relative units.

  8. Probe-based data storage

    CERN Document Server

    Koelmans, Wabe W; Abelmann, L

    2015-01-01

    Probe-based data storage attracted many researchers from academia and industry, resulting in unprecendeted high data-density demonstrations. This topical review gives a comprehensive overview of the main contributions that led to the major accomplishments in probe-based data storage. The most investigated technologies are reviewed: topographic, phase-change, magnetic, ferroelectric and atomic and molecular storage. Also, the positioning of probes and recording media, the cantilever arrays and parallel readout of the arrays of cantilevers are discussed. This overview serves two purposes. First, it provides an overview for new researchers entering the field of probe storage, as probe storage seems to be the only way to achieve data storage at atomic densities. Secondly, there is an enormous wealth of invaluable findings that can also be applied to many other fields of nanoscale research such as probe-based nanolithography, 3D nanopatterning, solid-state memory technologies and ultrafast probe microscopy.

  9. Advancement of Compositional and Microstructural Design of Intermetallic γ-TiAl Based Alloys Determined by Atom Probe Tomography

    Directory of Open Access Journals (Sweden)

    Thomas Klein

    2016-09-01

    Full Text Available Advanced intermetallic alloys based on the γ-TiAl phase have become widely regarded as most promising candidates to replace heavier Ni-base superalloys as materials for high-temperature structural components, due to their facilitating properties of high creep and oxidation resistance in combination with a low density. Particularly, recently developed alloying concepts based on a β-solidification pathway, such as the so-called TNM alloy, which are already incorporated in aircraft engines, have emerged offering the advantage of being processible using near-conventional methods and the option to attain balanced mechanical properties via subsequent heat-treatment. Development trends for the improvement of alloying concepts, especially dealing with issues regarding alloying element distribution, nano-scale phase characterization, phase stability, and phase formation mechanisms demand the utilization of high-resolution techniques, mainly due to the multi-phase nature of advanced TiAl alloys. Atom probe tomography (APT offers unique possibilities of characterizing chemical compositions with a high spatial resolution and has, therefore, been widely used in recent years with the aim of understanding the materials constitution and appearing basic phenomena on the atomic scale and applying these findings to alloy development. This review, thus, aims at summarizing scientific works regarding the application of atom probe tomography towards the understanding and further development of intermetallic TiAl alloys.

  10. Atoms

    Institute of Scientific and Technical Information of China (English)

    刘洪毓

    2007-01-01

    Atoms(原子)are all around us.They are something like the bricks (砖块)of which everything is made. The size of an atom is very,very small.In just one grain of salt are held millions of atoms. Atoms are very important.The way one object acts depends on what

  11. Effect of the tip state during qPlus noncontact atomic force microscopy of Si(100 at 5 K: Probing the probe

    Directory of Open Access Journals (Sweden)

    Adam Sweetman

    2012-01-01

    Full Text Available Background: Noncontact atomic force microscopy (NC-AFM now regularly produces atomic-resolution images on a wide range of surfaces, and has demonstrated the capability for atomic manipulation solely using chemical forces. Nonetheless, the role of the tip apex in both imaging and manipulation remains poorly understood and is an active area of research both experimentally and theoretically. Recent work employing specially functionalised tips has provided additional impetus to elucidating the role of the tip apex in the observed contrast.Results: We present an analysis of the influence of the tip apex during imaging of the Si(100 substrate in ultra-high vacuum (UHV at 5 K using a qPlus sensor for noncontact atomic force microscopy (NC-AFM. Data demonstrating stable imaging with a range of tip apexes, each with a characteristic imaging signature, have been acquired. By imaging at close to zero applied bias we eliminate the influence of tunnel current on the force between tip and surface, and also the tunnel-current-induced excitation of silicon dimers, which is a key issue in scanning probe studies of Si(100.Conclusion: A wide range of novel imaging mechanisms are demonstrated on the Si(100 surface, which can only be explained by variations in the precise structural configuration at the apex of the tip. Such images provide a valuable resource for theoreticians working on the development of realistic tip structures for NC-AFM simulations. Force spectroscopy measurements show that the tip termination critically affects both the short-range force and dissipated energy.

  12. Electro-optic probe measurements of electric fields in plasmas

    Science.gov (United States)

    Nishiura, M.; Yoshida, Z.; Mushiake, T.; Kawazura, Y.; Osawa, R.; Fujinami, K.; Yano, Y.; Saitoh, H.; Yamasaki, M.; Kashyap, A.; Takahashi, N.; Nakatsuka, M.; Fukuyama, A.

    2017-02-01

    The direct measurements of high-frequency electric fields in a plasma bring about significant advances in the physics and engineering of various waves. We have developed an electro-optic sensor system based on the Pockels effect. Since the signal is transmitted through an optical fiber, the system has high tolerance for electromagnetic noises. To demonstrate its applicability to plasma experiments, we report the first result of measurement of the ion-cyclotron wave excited in the RT-1 magnetosphere device. This study compares the results of experimental field measurements with simulation results of electric fields in plasmas.

  13. Near-field probing of photonic crystal directional couplers

    DEFF Research Database (Denmark)

    Volkov, V. S.; Bozhevolnyi, S. I.; Borel, Peter Ingo

    2006-01-01

    . By comparing the near-field optical images recorded in and after the directional coupler area, the features of light distribution are analyzed. Finally, the scanning near-field optical microscope observations are found to be in agreement with the transmission measurements conducted with the same sample.......We report the design, fabrication and characterization of a photonic crystal directional with a size of ~20 x 20 mm2 fabricated in silicon-on-insulator material. Using a scanning near-field optical microscope we demonstrate a high coupling efficiency for TM polarized light at telecom wavelengths...

  14. Nanopatterning on silicon surface using atomic force microscopy with diamond-like carbon (DLC-coated Si probe

    Directory of Open Access Journals (Sweden)

    Zhou Jingfang

    2011-01-01

    Full Text Available Abstract Atomic force microscope (AFM equipped with diamond-like carbon (DLC-coated Si probe has been used for scratch nanolithography on Si surfaces. The effect of scratch direction, applied tip force, scratch speed, and number of scratches on the size of the scratched geometry has been investigated. The size of the groove differs with scratch direction, which increases with the applied tip force and number of scratches but decreases slightly with scratch speed. Complex nanostructures of arrays of parallel lines and square arrays are further fabricated uniformly and precisely on Si substrates at relatively high scratch speed. DLC-coated Si probe has the potential to be an alternative in AFM-based scratch nanofabrication on hard surfaces.

  15. A New Method for Analyzing Near-Field Faraday Probe Data in Hall Thrusters

    Science.gov (United States)

    Huang, Wensheng; Shastry, Rohit; Herman, Daniel A.; Soulas, George C.; Kamhawi, Hani

    2013-01-01

    This paper presents a new method for analyzing near-field Faraday probe data obtained from Hall thrusters. Traditional methods spawned from far-field Faraday probe analysis rely on assumptions that are not applicable to near-field Faraday probe data. In particular, arbitrary choices for the point of origin and limits of integration have made interpretation of the results difficult. The new method, called iterative pathfinding, uses the evolution of the near-field plume with distance to provide feedback for determining the location of the point of origin. Although still susceptible to the choice of integration limits, this method presents a systematic approach to determining the origin point for calculating the divergence angle. The iterative pathfinding method is applied to near-field Faraday probe data taken in a previous study from the NASA-300M and NASA-457Mv2 Hall thrusters. Since these two thrusters use centrally mounted cathodes the current density associated with the cathode plume is removed before applying iterative pathfinding. A procedure is presented for removing the cathode plume. The results of the analysis are compared to far-field probe analysis results. This paper ends with checks on the validity of the new method and discussions on the implications of the results.

  16. Dynamic Polariton and Quantum State Swapping Between an Electromagnetic Field and Atomic Ensemble

    Institute of Scientific and Technical Information of China (English)

    汪凯戈; 杨国建

    2002-01-01

    We analyse a dynamical swapping of the quantum state in coupled harmonic oscillators. The result can be applied to the interaction of a single-mode field with atomic ensemble in the weak field case. Similar to the case of electromagnetic induced transparency (EIT), a dynamic polariton is formed. Therefore, the quantum state of the field can be completely mapped on to the atomic medium, and vice versa. Using this dynamical swapping and the adiabatic transfer in the EIT between the field and atomic ensemble, we propose a scheme in which both the quantum and the coherent information can be transferred from one field to another.

  17. Atom probe tomography study on Ge{sub 1−x−y}Sn{sub x}C{sub y} hetero-epitaxial film on Ge substrates

    Energy Technology Data Exchange (ETDEWEB)

    Kamiyama, Eiji, E-mail: ejkamiyama@aol.com [Technology, GlobalWafers Japan Corp. Ltd., 6-861-5 Higashiko, Seiro, Niigata 957-0197 (Japan); Department of Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja-shi, Okayama-ken 719-1197 (Japan); Sueoka, Koji [Department of Communication Engineering, Okayama Prefectural University, 111 Kuboki, Soja-shi, Okayama-ken 719-1197 (Japan); Terasawa, Kengo; Yamaha, Takashi; Nakatsuka, Osamu [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Zaima, Shigeaki [Department of Crystalline Materials Science, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8603 (Japan); Izunome, Koji; Kashima, Kazuhiko [Technology, GlobalWafers Japan Corp. Ltd., 6-861-5 Higashiko, Seiro, Niigata 957-0197 (Japan); Uchida, Hiroshi [Physical Analysis Technology Center, Toshiba Nanoanalysis Corporation, 8 Shinsugita-cho, Isogo-ku, Yokohama 235-8522 (Japan)

    2015-10-01

    We analyzed the incorporation of C atoms into a ternary alloy Ge{sub 1−x−y}Sn{sub x}C{sub y} epitaxial film on Ge substrates on a sub-nanometer scale by using atom probe tomography. Periodic atom distributions from individual (111) atomic planes were observed both in the Ge{sub 1−x−y}Sn{sub x}C{sub y} film and at the Ge substrates. Sn/C atoms had non-uniform distributions in the film. They also demonstrated a clear positive correlation in their distributions. Substitutional C atoms were only incorporated into the film when an Sn atom beam was applied onto the substrates under film growth conditions. - Highlights: • Incorporation of C atoms into epitaxial Ge{sub 1−x−y}Sn{sub x}C{sub y} film was studied. • Individual (111) atomic planes were observed by atom probe tomography. • Sn/C atoms had non-uniform distributions in the film. • Clear positive correlation in Sn/C atoms distributions was obtained.

  18. Interference of Atomic Bose-Einstein Condensate Interacting with Laser Field

    Institute of Scientific and Technical Information of China (English)

    YU Zhao-Xian; JIAO Zhi-Yong; SUN Jin-Zuo

    2004-01-01

    Interference of an atomic Bose-Einstein condensate interacting with a laser field in a double-well potential with dissipation is investigated. If properly selecting the laser field and the initial states of the atoms in the two wells,we find that the intensity exhibits revivals and collapses. The fidelity of interference is affected by the total number of atoms in the two wells and dissipation.

  19. Nonlinear Effects in Quantum Dynamics of Atom Laser: Mean-Field Approach

    Institute of Scientific and Technical Information of China (English)

    JING Hui

    2002-01-01

    Quantum dynamics and statistics of an atom laser with nonlinear binary interactions are investigated inthe framework of mean-field approximation. The linearized effective Hamiltonian of the system is accurately solvable.It is shown that, although the input radio frequency field is in an ordinary Glauber coherent state, the output matterwave will periodically exhibit quadrature squeezing effects purely originated from the nonlinear atom-atom collisions.

  20. Predoping effects of boron and phosphorous on arsenic diffusion along grain boundaries in polycrystalline silicon investigated by atom probe tomography

    Science.gov (United States)

    Takamizawa, Hisashi; Shimizu, Yasuo; Inoue, Koji; Nozawa, Yasuko; Toyama, Takeshi; Yano, Fumiko; Inoue, Masao; Nishida, Akio; Nagai, Yasuyoshi

    2016-10-01

    The effect of P or B predoping on As diffusion in polycrystalline Si was investigated by atom probe tomography. In all samples, a high concentration of As was found at grain boundaries, indicating that such boundaries are the main diffusion path. However, As grain-boundary diffusion was suppressed in the B-doped sample and enhanced in the P-doped sample. In a sample codoped with both P and B, As diffusion was somewhat enhanced, indicating competition between the effects of the two dopants. The results suggest that As grain-boundary diffusion can be controlled by varying the local concentration of P or B.

  1. The use of weak magnetic fields in collisions of polarized atoms

    NARCIS (Netherlands)

    Meijer, H.A.J.; Zeegers, Th.; Pelgrim, T.J.C.; Heideman, H.G.M.; Morgenstern, R.

    1989-01-01

    We have experimentally and theoretically investigated the behavior of excited Na atoms under the combined influence of resonant laser light and a weak magnetic field. The use of weak magnetic fields gives another possibility to vary the polarization of the atoms, additional to variation of the polar

  2. Fidelity of quantum state for interacting system of light field and atomic Bose-Einstein condensate

    Institute of Scientific and Technical Information of China (English)

    Chunjia Huang; Ming Zhou; Fanzhi Kong; Jiayuan Fang; Kewei Mo

    2005-01-01

    @@ The evolution characteristics of quantum state fidelity in an interacting system of single-mode light field and atomic Bose-Einstein condensate have been studied and the influence of the initial light field intensity and the interaction among atoms of Bose-Einstein condensate on the quantum state fidelity respectively have been discussed.

  3. Variation of local atomic structure due to devitrification of Ni-Zr alloy thin films probed by EXAFS measurements

    Science.gov (United States)

    Bhattacharya, Debarati; Tiwari, Nidhi; Bhattacharyya, Dibyendu; Jha, S. N.; Basu, S.

    2016-05-01

    Thin film metallic glasses (TFMGs) exhibit properties superior to their bulk counterparts allowing them to be potentially useful in many practical applications. Apart from their technological interest, when converted to crystallized state (devitrification) TFMGs can also act as precursors for partially crystallized or fully crystallized forms. Such devitrified forms are attractive due to their novel structural and magnetic properties. The amorphous-to-crystalline transformation of co-sputtered Ni-Zr alloy thin films through annealing was studied using EXAFS (Extended X-ray Absorption Fine Structure) measurements. Investigation through an atomic probe gives a better insight into the local environment of the atomic species, rendering a deeper understanding of thermal evolution of such materials.

  4. Probing the dynamic structure factor of a neutral Fermi superfluid along the BCS-BEC crossover using atomic impurity qubits

    Science.gov (United States)

    Mitchison, Mark T.; Johnson, Tomi H.; Jaksch, Dieter

    2016-12-01

    We study an impurity atom trapped by an anharmonic potential, immersed within a cold atomic Fermi gas with attractive interactions that realizes the crossover from a Bardeen-Cooper-Schrieffer superfluid to a Bose-Einstein condensate. Considering the qubit comprising the lowest two vibrational energy eigenstates of the impurity, we demonstrate that its dynamics probes the equilibrium density fluctuations encoded in the dynamic structure factor of the superfluid. Observing the impurity's evolution is thus shown to facilitate nondestructive measurements of the superfluid order parameter and the contact between collective and single-particle excitation spectra. Our setup constitutes a model of an open quantum system interacting with a thermal reservoir, the latter supporting both bosonic and fermionic excitations that are also coupled to each other.

  5. Photoelectron imaging, probe of the dynamics: from atoms... to clusters; Imagerie de photoelectrons, sonde de la dynamique: des atomes... aux agregats

    Energy Technology Data Exchange (ETDEWEB)

    Lepine, F

    2003-06-15

    This thesis concerns the study of the deexcitation of clusters and atoms by photoelectron imaging. The first part is dedicated to thermionic emission of a finite size system. A 3-dimensional imaging setup allows us to measure the time evolution of the kinetic energy spectrum of electrons emitted from different clusters (W{sub n}{sup -}, C{sub n}{sup -}, C{sub 60}). Then we have a direct access to the fundamental quantities which characterize this statistical emission: the temperature of the finite heat bath and the decay rate. The second part concerns the ionization of atomic Rydberg states placed in a static electric field. We performed the first experiment of photoionization microscopy which allows us to obtain a picture which is the macroscopic projection of the electronic wave function. Then we have access to the detail of the photoionization and particularly to the quantum properties of the electron usually confined at the atomic scale. (author)

  6. Mg I as a probe of the solar chromosphere - The atomic model

    Science.gov (United States)

    Mauas, Pablo J.; Avrett, Eugene H.; Loeser, Rudolf

    1988-01-01

    This paper presents a complete atomic model for Mg I line synthesis, where all the atomic parameters are based on recent experimental and theoretical data. It is shown how the computed profiles at 4571 A and 5173 A are influenced by the choice of these parameters and the number of levels included in the model atom. In addition, observed profiles of the 5173 A b2 line and theoretical profiles for comparison (based on a recent atmospheric model for the average quiet sun) are presented.

  7. Probing the magnetic fields in L1415 and L1389

    CERN Document Server

    Soam, A; G., Maheswar; Kim, Gwanjeong; S., Neha; Kim, Mi-Ryang

    2016-01-01

    We present the R-band polarimetric results towards two nebulae L1415 and L1389 containing low luminosity stars. Aim of this study is to understand the role played by magnetic fields in formation of low luminosity objects. Linear polarization arise due to dichroism of the background starlight projected on the cloud providing the plane-of-the sky magnetic field orientation. The offsets between mean magnetic field directions obtained towards L1415 and L1389 and the projected outflow axes are found to be 35$^{\\circ}$ and 12$^{\\circ}$, respectively. The offset between cloud minor axes and mean envelope magnetic field direction in L1415 and L1389 are 50$^{\\circ}$ and 87$^{\\circ}$, respectively. To estimate the magnetic field strength by using the updated Chandrasekhar-Fermi relation, we obtained the $^{12}$CO(J=1-0) line velocity dispersion value towards L1415 cloud using the TRAO single dish observations. The values of B$_{pos}$ in L1415 and L1389 are found to be 28$~\\mu$G and 149$~\\mu$G using CF technique and 23$...

  8. Probing Intergalactic Magnetic Fields with Simulations of Electromagnetic Cascades

    CERN Document Server

    Batista, Rafael Alves; Sigl, Guenter; Vachaspati, Tanmay

    2016-01-01

    We determine the effect of intergalactic magnetic fields on the distribution of high energy gamma rays by performing three-dimensional Monte Carlo simulations of the development of gamma-ray-induced electromagnetic cascades in the magnetized intergalactic medium. We employ the so-called 'Large Sphere Observer' method to efficiently simulate blazar gamma ray halos. We study magnetic fields with a Batchelor spectrum and with maximal left- and right-handed helicities. We also consider the case of sources whose jets are tilted with respect to the line of sight. We verify the formation of extended gamma ray halos around the source direction, and observe spiral-like patterns if the magnetic field is helical. We apply the $Q$-statistics to the simulated halos to extract their spiral nature and also propose an alternative method, the $S$-statistics. Both methods provide a quantative way to infer the helicity of the intervening magnetic fields from the morphology of individual blazar halos for magnetic field strengths...

  9. Probing correlations of early magnetic fields using μ-distortion

    Energy Technology Data Exchange (ETDEWEB)

    Ganc, Jonathan; Sloth, Martin S., E-mail: ganc@cp3.dias.sdu.dk, E-mail: sloth@cp3.dias.sdu.dk [CP" 3-Origins, Center for Cosmology and Particle Physics Phenomenology, University of Southern Denmark, Campusvej 55, 5230 Odense M (Denmark)

    2014-08-01

    The damping of a non-uniform magnetic field between the redshifts of about 10{sup 4} and 10{sup 6} injects energy into the photon-baryon plasma and causes the CMB to deviate from a perfect blackbody spectrum, producing a so-called μ-distortion. We can calculate the correlation (μ T) of this distortion with the temperature anisotropy T of the CMB to search for a correlation ( B{sup 2}ζ) between the magnetic field B and the curvature perturbation ζ; knowing the ( B{sup 2}ζ) correlation would help us distinguish between different models of magnetogenesis. Since the perturbations which produce the μ-distortion will be much smaller scale than the relevant density perturbations, the observation of this correlation is sensitive to the squeezed limit of ( B{sup 2}ζ), which is naturally parameterized by b{sub NL} (a parameter defined analogously to f{sub NL}). We find that a PIXIE-like CMB experiments has a signal to noise S/N≈ 1.0 × b{sub NL} ( B-tilde {sub μ}/10nG){sup 2}, where B-tilde {sub μ} is the magnetic field's strength on μ-distortion scales normalized to today's redshift; thus, a 10 nG field would be detectable with b{sub NL}=O(1). However, if the field is of inflationary origin, we generically expect it to be accompanied by a curvature bispectrum (ζ{sup 3}) induced by the magnetic field. For sufficiently small magnetic fields, the signal ( B{sup 2} ζ) will dominate, but for B-tilde {sub μ}∼> 1 nG, one would have to consider the specifics of the inflationary magnetogenesis model. We also discuss the potential post-magnetogenesis sources of a ( B{sup 2}ζ) correlation and explain why there will be no contribution from the evolution of the magnetic field in response to the curvature perturbation.

  10. Influence of the probe-sample interaction on scanning near-field optical microscopic images in the far field

    Institute of Scientific and Technical Information of China (English)

    Li Zhi; Zhang Jia-Sen; Yang Jing; Gong Qi-Huang

    2006-01-01

    We have studied the influence of probe-sample interaction in a scanning near-field optical microscopy (SNOM) in the far field by using samples with a step structure. For a sample with a step height of ~λ/4, the SNOM image contrast between the two sides of the step changes periodically at different scan heights. For a step height of ~λ/2, the image contrast remains approximately the same. The probe-sample interaction determines the SNOM image contrast here. The influence of different refractive indices of the sample has been also analysed by using a simple theoretical model.

  11. Modified pulsar current analysis: probing magnetic field evolution

    CERN Document Server

    Igoshev, A P

    2014-01-01

    We use a modified pulsar current analysis to study magnetic field decay in radio pulsars. In our approach we analyse the flow, not along the spin period axis as has been performed in previous studies, but study the flow along the direction of growing characteristic age, $\\tau=P/(2\\dot P)$. We perform extensive tests of the method and find that in most of the cases it is able to uncover non-negligible magnetic field decay (more than a few tens of per cent during the studied range of ages) in normal radio pulsars for realistic initial properties of neutron stars. However, precise determination of the magnetic field decay timescale is not possible at present. The estimated timescale may differ by a factor of few for different sets of initial distributions of neutron star parameters. In addition, some combinations of initial distributions and/or selection effects can also mimic enhanced field decay. We apply our method to the observed sample of radio pulsars at distances $<10$ kpc in the range of characteristi...

  12. Probing correlations of early magnetic fields using mu-distortion

    DEFF Research Database (Denmark)

    Ganc, Jonathan; Sloth, Martin Snoager

    2014-01-01

    The damping of a non-uniform magnetic field between the redshifts of about $10^4$ and $10^6$ injects energy into the photon-baryon plasma and causes the CMB to deviate from a perfect blackbody spectrum, producing a so-called $\\mu$-distortion. We can calculate the correlation $\\langle\\mu T......\\rangle$ of this distortion with the temperature anisotropy $T$ of the CMB to search for a correlation $\\langle B^2\\zeta\\rangle$ between the magnetic field $B$ and the curvature perturbation $\\zeta$; knowing the $\\langle B^2\\zeta\\rangle$ correlation would help us distinguish between different models of magnetogenesis. Since......_{\\text{NL}}$). We find that a PIXIE-like CMB experiments has a signal to noise $S/N\\approx 1.0 \\times b_{\\text{NL}} (\\tilde B_\\mu/10\\text{ nG})^2$, where $\\tilde B_\\mu$ is the magnetic field's strength on $\\mu$-distortion scales normalized to today's redshift; thus, a 10 nG field would be detectable with $b...

  13. Laser-induced reversion of $\\delta^{'}$ precipitates in an Al-Li alloy: Study on temperature rise in pulsed laser atom probe

    CERN Document Server

    Khushaim, Muna; Al-Kassab, Talaat

    2015-01-01

    The influence of tuning the laser energy during the analyses on the resulting microstructure in a specimen utilizing an ultra-fast laser assisted atom probe was demonstrated by a case study of a binary Al-Li alloy. The decomposition parameters, such as the size, number density, volume fraction and composition of $\\delta^{'}$ precipitates, were carefully monitored after each analysis. A simple model was employed to estimate the corresponding specimen temperature for each value of the laser energy. The results indicated that the corresponding temperatures for the laser energy in the range of 10 to 80 pJ are located inside the miscibility gap of the binary Al-Li phase diagram and fall into the metastable equilibrium field. In addition, the corresponding temperature for a laser energy of 100 pJ was in fairly good agreement with reported range of $\\delta^{'}$ solvus temperature, suggesting a result of reversion upon heating due to laser pulsing.

  14. Parameters affecting the adhesion strength between a living cell and a colloid probe when measured by the atomic force microscope.

    Science.gov (United States)

    McNamee, Cathy E; Pyo, Nayoung; Tanaka, Saaya; Vakarelski, Ivan U; Kanda, Yoichi; Higashitani, Ko

    2006-03-15

    In this study, we used the colloid probe atomic force microscopy (AFM) technique to investigate the adhesion force between a living cell and a silica colloid particle in a Leibovitz's L-15 medium (L-15). The L-15 liquid maintained the pharmaceutical conditions necessary to keep the cells alive in the outside environment during the AFM experiment. The force curves in such a system showed a steric repulsion in the compression force curve, due to the compression of the cells by the colloid probe, and an adhesion force in the decompression force curve, due to binding events between the cell and the probe. We also investigated for the first time how the position on the cell surface, the strength of the pushing force, and the residence time of the probe at the cell surface individually affected the adhesion force between a living cell and a 6.84 microm diameter silica colloid particle in L-15. The position of measuring the force on the cell surface was seen not to affect the value of the maximum adhesion force. The loading force was also seen not to notably affect the value of the maximum adhesion force, if it was small enough not to pierce and damage the cell. The residence time of the probe at the cell surface, however, clearly affected the adhesion force, where a longer residence time gave a larger maximum force. From these results, we could conclude that the AFM force measurements should be made using a loading force small enough not to damage the cell and a fixed residence time, when comparing results of different systems.

  15. Four-probe scanning tunnelling microscope with atomic resolution for electrical and electro-optical property measurements of nanosystems

    Institute of Scientific and Technical Information of China (English)

    Lin Xiao; He Xiao-Bo; Lu Jun-Ling; Gao Li; Huan Qing; Shi Dong-Xia; Gao Hong-Jun

    2005-01-01

    We demonstrate a special four-probe scanning tunnelling microscope (STM) system in ultrahigh vacuum (UHV),which can provide coarse positioning for every probe independently with the help of scanning electron microscope (SEM)and fine positioning down to nanometre using the STM technology. The system allows conductivity measurement by means of a four-point probe method, which can draw out more accurate electron transport characteristics in nanostructures, and provides easy manipulation of low dimension materials. All measurements can be performed in variable temperature (from 30K to 500K), magnetic field (from 0 to 0.1T), and different gas environments. Simultaneously, the cathodoluminescence (CL) spectrum can be achieved through an optical subsystem. Test measurements using some nanowire samples show that this system is a powerful tool in exploring electron transport characteristics and spectra in nanoscale physics.

  16. Probing correlations of early magnetic fields using $\\mu$-distortion

    CERN Document Server

    Ganc, Jonathan

    2014-01-01

    The damping of a non-uniform magnetic field between the redshifts of about $10^4$ and $10^6$ injects energy into the photon-baryon plasma and causes the CMB to deviate from a perfect blackbody spectrum, producing a so-called $\\mu$-distortion. We can calculate the correlation $\\langle\\mu T\\rangle$ of this distortion with the temperature anisotropy $T$ of the CMB to search for a correlation $\\langle B^2\\zeta\\rangle$ between the magnetic field $B$ and the curvature perturbation $\\zeta$. Since the perturbations which produce the $\\mu$-distortion will be much smaller scale than the relevant density perturbations, the observation of this correlation is sensitive to the squeezed limit of $\\langle B^2\\zeta\\rangle$, which is naturally parameterized by $b_{\\text{NL}}$ (a parameter defined analogously to $f_{\\text{NL}}$). We find that a PIXIE-like CMB experiments has a signal to noise $S/N\\approx 1.0 \\times b_{\\text{NL}} (\\tilde B_\\mu/10\\text{ nG})^2$, where $\\tilde B_\\mu$ is the magnetic field's strength on $\\mu$-disto...

  17. Electric field measurement of organic photovoltaic cell model using electrooptic probe

    Science.gov (United States)

    Saito, Ryo; Yabe, Yoko; Suzuki, Akito; Shinagawa, Mitsuru; Sugino, Hiroyuki; Katsuyama, Jun; Matsumoto, Yoshinori

    2016-09-01

    In this paper, we describe the use of a transverse electrooptic probe to measure the electric field of an organic photovoltaic (OPV) cell model. It is necessary to measure the voltage of each OPV cell in order to diagnose failure of the OPV. An electric field is generated by the OPV cell voltage, so measuring the electric field is effective for obtaining a failure diagnosis of the OPV. We use a transverse electrooptic probe as an instrumentation tool for measuring the electric field over the OPV. We confirmed the principle of superposition for the electric field strength from each OPV cell model. These results show that the calibration of each OPV cell voltage can be accomplished by measuring the electric field strength over the OPV cells.

  18. The Spin-Plane Double Probe Electric Field Instrument for MMS

    Science.gov (United States)

    Lindqvist, P.-A.; Olsson, G.; Torbert, R. B.; King, B.; Granoff, M.; Rau, D.; Needell, G.; Turco, S.; Dors, I.; Beckman, P.; Macri, J.; Frost, C.; Salwen, J.; Eriksson, A.; Åhlén, L.; Khotyaintsev, Y. V.; Porter, J.; Lappalainen, K.; Ergun, R. E.; Wermeer, W.; Tucker, S.

    2016-03-01

    The Spin-plane double probe instrument (SDP) is part of the FIELDS instrument suite of the Magnetospheric Multiscale mission (MMS). Together with the Axial double probe instrument (ADP) and the Electron Drift Instrument (EDI), SDP will measure the 3-D electric field with an accuracy of 0.5 mV/m over the frequency range from DC to 100 kHz. SDP consists of 4 biased spherical probes extended on 60 m long wire booms 90∘ apart in the spin plane, giving a 120 m baseline for each of the two spin-plane electric field components. The mechanical and electrical design of SDP is described, together with results from ground tests and calibration of the instrument.

  19. Coherent population oscillation produced by saturating probe and pump fields on the intercombination Line

    CERN Document Server

    Vafafard, A; Agarwal, G S

    2016-01-01

    We present a theoretical study of the experiments on coherent population oscillations and coher- ent population trapping on the intercombination line of 174Y b. The transition involves a change of the spin and thus can not be interpreted in terms of an effective Lambda system. The reported experiments are done in the regime where both pump and probe fields can saturate the transition. We demonstrate by both numerical and analytical calculations the appearance of the interference minimum as both pump and probe start saturating the transition. We present an analytical result for the threshold probe power when the interference minimum can appear. We also present de- tailed study of the appearance of the interference minimum when magnetic fields are applied. The magnetic fields not only create Zeeman splittings but in addition make the system open because of the couplings to other levels. We show the possibility of interference minimum at the position of subharmonic resonances.

  20. The Muonium Atom as a Probe of Physics beyond the Standard Model

    NARCIS (Netherlands)

    Willmann, L.; Jungmann, K.

    1998-01-01

    The observed interactions between particles are not fully explained in the successful theoretical description of the standard model to date. Due to the close confinement of the bound state muonium ($M = \\mu^+ e^-$) can be used as an ideal probe of quantum electrodynamics and weak interaction and als

  1. Probing Magnetism in 2D Molecular Networks after in Situ Metalation by Transition Metal Atoms.

    Science.gov (United States)

    Schouteden, K; Ivanova, Ts; Li, Z; Iancu, V; Janssens, E; Van Haesendonck, C

    2015-03-19

    Metalated molecules are the ideal building blocks for the bottom-up fabrication of, e.g., two-dimensional arrays of magnetic particles for spintronics applications. Compared to chemical synthesis, metalation after network formation by an atom beam can yield a higher degree of control and flexibility and allows for mixing of different types of magnetic atoms. We report on successful metalation of tetrapyridyl-porphyrins (TPyP) by Co and Cr atoms, as demonstrated by scanning tunneling microscopy experiments. For the metalation, large periodic networks formed by the TPyP molecules on a Ag(111) substrate are exposed in situ to an atom beam. Voltage-induced dehydrogenation experiments support the conclusion that the porphyrin macrocycle of the TPyP molecule incorporates one transition metal atom. The newly synthesized Co-TPyP and Cr-TPyP complexes exhibit striking differences in their electronic behavior, leading to a magnetic character for Cr-TPyP only as evidenced by Kondo resonance measurements.

  2. Probing the Quantum States of a Single Atom Transistor at Microwave Frequencies.

    Science.gov (United States)

    Tettamanzi, Giuseppe Carlo; Hile, Samuel James; House, Matthew Gregory; Fuechsle, Martin; Rogge, Sven; Simmons, Michelle Y

    2017-03-28

    The ability to apply gigahertz frequencies to control the quantum state of a single P atom is an essential requirement for the fast gate pulsing needed for qubit control in donor-based silicon quantum computation. Here, we demonstrate this with nanosecond accuracy in an all epitaxial single atom transistor by applying excitation signals at frequencies up to ≈13 GHz to heavily phosphorus-doped silicon leads. These measurements allow the differentiation between the excited states of the single atom and the density of states in the one-dimensional leads. Our pulse spectroscopy experiments confirm the presence of an excited state at an energy ≈9 meV, consistent with the first excited state of a single P donor in silicon. The relaxation rate of this first excited state to the ground state is estimated to be larger than 2.5 GHz, consistent with theoretical predictions. These results represent a systematic investigation of how an atomically precise single atom transistor device behaves under radio frequency excitations.

  3. Atomic-level imaging, processing and characterization of semiconductor surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kazmerski, L.L.

    1995-08-22

    A method for selecting and removing single specific atoms from a solid material surface uses photon biasing to break down bonds that hold the selected atom in the lattice and to reduce barrier effects that hold the atom from transferring to a probe. The photon bias is preferably light or other electromagnetic radiation with a wavelength and frequency that approximately matches the wave function of the target atom species to be removed to induce high energy, selective thermionic-like vibration. An electric field potential is then applied between the probe and the surface of the solid material to pull the atom out of the lattice and to transfer the atom to the probe. Different extrinsic atoms can be installed in the lattice sites that are vacated by the removed atoms by using a photon bias that resonates the extrinsic atom species, reversing polarity of the electric field, and blowing gas comprising the extrinsic atoms through a hollow catheter probe. 8 figs.

  4. Atomic-level imaging, processing and characterization of semiconductor surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Kazmerski, Lawrence L. (Lakewood, CO)

    1995-01-01

    A method for selecting and removing single specific atoms from a solid material surface uses photon biasing to break down bonds that hold the selected atom in the lattice and to reduce barrier effects that hold the atom from transferring to a probe. The photon bias is preferably light or other electromagnetic radiation with a wavelength and frequency that approximately matches the wave function of the target atom species to be removed to induce high energy, selective thermionic-like vibration. An electric field potential is then applied between the probe and the surface of the solid material to pull the atom out of the lattice and to transfer the atom to the probe. Different extrinsic atoms can be installed in the lattice sites that are vacated by the removed atoms by using a photon bias that resonates the extrinsic atom species, reversing polarity of the electric field, and blowing gas comprising the extrinsic atoms through a hollow catheter probe.

  5. Rotational symmetry breaking in the topological superconductor SrxBi2Se3 probed by upper-critical field experiments.

    Science.gov (United States)

    Pan, Y; Nikitin, A M; Araizi, G K; Huang, Y K; Matsushita, Y; Naka, T; de Visser, A

    2016-01-01

    Recently it was demonstrated that Sr intercalation provides a new route to induce superconductivity in the topological insulator Bi2Se3. Topological superconductors are predicted to be unconventional with an odd-parity pairing symmetry. An adequate probe to test for unconventional superconductivity is the upper critical field, Bc2. For a standard BCS layered superconductor Bc2 shows an anisotropy when the magnetic field is applied parallel and perpendicular to the layers, but is isotropic when the field is rotated in the plane of the layers. Here we report measurements of the upper critical field of superconducting SrxBi2Se3 crystals (Tc = 3.0 K). Surprisingly, field-angle dependent magnetotransport measurements reveal a large anisotropy of Bc2 when the magnet field is rotated in the basal plane. The large two-fold anisotropy, while six-fold is anticipated, cannot be explained with the Ginzburg-Landau anisotropic effective mass model or flux flow induced by the Lorentz force. The rotational symmetry breaking of Bc2 indicates unconventional superconductivity with odd-parity spin-triplet Cooper pairs (Δ4-pairing) recently proposed for rhombohedral topological superconductors, or might have a structural nature, such as self-organized stripe ordering of Sr atoms.

  6. Description of Atom-Field Interaction via Quantized Caldirola-Kanai Hamiltonian

    Science.gov (United States)

    Daneshmand, Roohollah; Tavassoly, Mohammad Kazem

    2017-01-01

    In this paper we outline an approach to the study of atom-field interacting systems, where the Hamiltonian of the field is simply inspired from the quantized Caldirola-Kanai Hamiltonian. As a simple physical realization of the model, the interaction between a two-level atom with such a single-mode field is studied. The explicit form of the atom-field entangled state associated with the considered system is analytically deduced and the dynamics of a few of its physical properties is numerically evaluated. To achieve the latter purposes, the temporal behavior of the degree of entanglement, atomic population inversion as well as sub-Poissonian statistics and quadrature squeezing of the field are evaluated. Moreover, the effects of the intensity of initial field and the damping parameter within the Caldirola-Kanai Hamiltonian on the above-mentioned criteria are investigated. As is shown, by adjusting the latter evolved parameters one can appropriately tune the discussed physical quantities.

  7. Classical trajectory perspective of atomic ionization in strong laser fields semiclassical modeling

    CERN Document Server

    Liu, Jie

    2014-01-01

    The ionization of atoms and molecules in strong laser fields is an active field in modern physics and has versatile applications in such as attosecond physics, X-ray generation, inertial confined fusion (ICF), medical science and so on. Classical Trajectory Perspective of Atomic Ionization in Strong Laser Fields covers the basic concepts in this field and discusses many interesting topics using the semiclassical model of classical trajectory ensemble simulation, which is one of the most successful ionization models and has the advantages of a clear picture, feasible computing and accounting for many exquisite experiments quantitatively. The book also presents many applications of the model in such topics as the single ionization, double ionization, neutral atom acceleration and other timely issues in strong field physics, and delivers useful messages to readers with presenting the classical trajectory perspective on the strong field atomic ionization. The book is intended for graduate students and researchers...

  8. Second harmonic generation at the probe tip for background-free near-field optical imaging.

    Science.gov (United States)

    Dong, Zhaogang; Soh, Yeng Chai

    2012-08-13

    Second harmonic generation (SHG) has been applied to reduce background signals in near-field optical imaging, but this technique is usually limited to samples with strong second-order nonlinear susceptibilities. To overcome this limitation, in this paper, we present a versatile background-free SHG configuration, where it utilizes the second-order nonlinear susceptibility of the probe which essentially functions as a near-field polarizer capable of filtering out the background signal component. In the theoretical analysis, we first model the probe-sample optical interactions at both the fundamental frequency and the second harmonic frequency by using the coupled dipole method. The theoretical model reveals that the proposed versatile background-free SHG configuration requires two conditions. The first condition is that the incident optical field must be s-polarized. The second condition is that the probe must be made of crystals from symmetry class 222, symmetry class 622, symmetry class 422, symmetry class 42m, symmetry class 43m or symmetry class 23. To demonstrate the effectiveness of the proposed versatile background-free SHG configuration, a probe made of deuterated potassium dideuterium phosphate (DKDP) crystal from symmetry class 42m is analyzed numerically. It is shown that when imaging samples with negligible second-order nonlinear susceptibilities, the proposed background-free SHG configuration improves the imaging contrast by more than one-order of magnitude as compared to all other imaging configurations. Moreover, we also investigate the dependence of its performance on other parameters, such as the probe-sample distance, the relative size between probe and sample, and the tilt angle of probe crystal. It is believed that the proposed configuration could be widely used to achieve high contrast near-field optical imaging.

  9. Characterization of local hydrophobicity on sapphire (0001) surfaces in aqueous environment by colloidal probe atomic force microscopy

    Science.gov (United States)

    Wada, Tomoya; Yamazaki, Kenji; Isono, Toshinari; Ogino, Toshio

    2017-02-01

    Sapphire (0001) surfaces exhibit a phase-separation into hydrophobic and hydrophilic domains upon high-temperature annealing, which were previously distinguished by the thickness of adsorbed water layers in air using atomic force microscopy (AFM). To characterize their local surface hydrophobicity in aqueous environment, we used AFM equipped with a colloidal probe and measured the local adhesive force between each sapphire domain and a hydrophilic SiO2 probe surface, or a hydrophobic polystyrene one. Two data acquisition modes for statistical analyses were used: one is force measurements at different positions of the surface and the other repeated measurement at a fixed position. We found that adhesive force measurements using the polystyrene probe allow us to distinctly separate the hydrophilic and hydrophobic domains. The dispersion in the force measurement data at different positions of the surface is larger than that in the repeated measurements at a fixed position. It indicates that the adhesive force measurement is repeatable although their data dispersion for the measurement positions is relatively large. From these results, we can conclude that the hydrophilic and hydrophobic domains on the sapphire (0001) surfaces are distinguished by a difference in their hydration degrees.

  10. Probing 2D Quantum Turbulence in Atomic Superfluid Gas using Bragg Scattering

    CERN Document Server

    Seo, Sang Won; Kim, Joon Hyun; Shin, Yong-il

    2016-01-01

    We demonstrate the use of spatially resolved Bragg spectroscopy for detection of the quantum vortex circulation signs in an atomic Bose-Einstein condensate (BEC). High-velocity atoms near the vortex cores are resonantly scattered from the BEC, and the vortex signs are determined from the scattered atom positions relative to the corresponding vortex cores. Using this method, we investigate decaying 2D quantum turbulence in a highly oblate BEC at temperatures of $\\sim 0.5 T_c$, where $T_c$ is the critical temperature of the trapped sample. Clustering of like-sign vortices is not observed; rather, the measured vortex configurations reveal weak pair correlations between the vortices and antivortices in the turbulent BEC. Our Bragg scattering method enables a direct experimental study of 2D quantum turbulence in BECs.

  11. Volatile organic compound ratios as probes of halogen atom chemistry in the Arctic

    Directory of Open Access Journals (Sweden)

    P. B. Shepson

    2008-03-01

    Full Text Available Volatile organic compound concentration ratios can be used as indicators of halogen chemistry that occurs during ozone depletion events in the Arctic during spring. Here we use a combination of modeling and measurements of [acetone]/[propanal] as an indicator of bromine chemistry, and [isobutane]/[n-butane] and [methyl ethyl ketone]/[n-butane] are used to study the extent of chlorine chemistry during four ozone depletion events during the Polar Sunrise Experiment of 1995. Using a 0-D photochemistry model in which the input of halogen atoms is controlled and varied, the approximate ratio of [Br]/[Cl] can be estimated for each ozone depletion event. It is concluded that there must be an additional source of propanal (likely from the snowpack to correctly simulate the VOC chemistry of the Arctic, and further evidence that the ratio of Br atoms to Cl atoms can vary greatly during ozone depletion events is presented.

  12. Volatile organic compound ratios as probes of halogen atom chemistry in the Arctic

    Directory of Open Access Journals (Sweden)

    A. E. Cavender

    2007-08-01

    Full Text Available Volatile organic compound concentration ratios can be used as indicators of halogen chemistry that occurs during ozone depletion events in the Arctic during spring. Here we use a combination of modeling and measurements of [acetone]/[propanal] as an indicator of bromine chemistry, and [isobutane]/[n-butane] and [methyl ethyl ketone]/[n-butane] are used to study the extent of chlorine chemistry during four ozone depletion events during the Polar Sunrise Experiment of 1995. Using a 0-D photochemistry model in which the input of halogen atoms is controlled and varied, the approximate ratio of [Br]/[Cl] can be estimated for each ozone depletion event. It is concluded that there must be an additional source of propanal (likely from the snowpack to correctly simulate the VOC chemistry of the Arctic, and that the ratio of Br atoms to Cl atoms can vary greatly during ozone depletion events.

  13. Spontaneous excitation of a circularly accelerated atom coupled with vacuum Dirac field fluctuations

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Jing [Institute of Physics and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Hu, Jiawei [Center for Nonlinear Science and Department of Physics, Ningbo University, Ningbo, Zhejiang 315211 (China); Yu, Hongwei, E-mail: hwyu@hunnu.edu.cn [Institute of Physics and Key Laboratory of Low Dimensional Quantum Structures and Quantum Control of Ministry of Education, Hunan Normal University, Changsha, Hunan 410081 (China); Center for Nonlinear Science and Department of Physics, Ningbo University, Ningbo, Zhejiang 315211 (China)

    2015-02-15

    We study the spontaneous excitation of a circularly accelerated atom coupled with vacuum Dirac field fluctuations by separately calculating the contribution to the excitation rate of vacuum fluctuations and a cross term which involves both vacuum fluctuations and radiation reaction, and demonstrate that although the spontaneous excitation for the atom in its ground state would occur in vacuum, such atoms in circular motion do not perceive a pure thermal radiation as their counterparts in linear acceleration do since the transition rates of the atom do not contain the Planckian factor characterizing a thermal bath. We also find that the contribution of the cross term that plays the same role as that of radiation reaction in the scalar and electromagnetic fields cases differs for atoms in circular motion from those in linear acceleration. This suggests that the conclusion drawn for atoms coupled with the scalar and electromagnetic fields that the contribution of radiation reaction to the mean rate of change of atomic energy does not vary as the trajectory of the atom changes from linear acceleration to circular motion is not a general trait that applies to the Dirac field where the role of radiation reaction is played by the cross term. - Highlights: • Spontaneous excitation of a circularly accelerated atom is studied. • The atom interacts with the Dirac field through nonlinear coupling. • A cross term involving vacuum fluctuations and radiation reaction contributes. • The atom in circular motion does not perceive pure thermal radiation. • The contribution of the cross term changes as the atomic trajectory varies.

  14. Quantum entanglement in the system of two two-level atoms interacting with a single-mode vacuum field

    Institute of Scientific and Technical Information of China (English)

    Zeng Ke; Fang Mao-Fa

    2005-01-01

    The entanglement properties of the system of two two-level atoms interacting with a single-mode vacuum field are explored. The quantum entanglement between two two-level atoms and a single-mode vacuum field is investigated by using the quantum reduced entropy; the quantum entanglement between two two-level atoms, and that between a single two-level atom and a single-mode vacuum field are studied in terms of the quantum relative entropy. The influences of the atomic dipole-dipole interaction on the quantum entanglement of the system are also discussed. Our results show that three entangled states of two atoms-field, atom-atom, and atom-field can be prepared via two two-level atoms interacting with a single-mode vacuum field.

  15. Classical-field description of the quantum effects in the light-atom interaction

    CERN Document Server

    Rashkovskiy, Sergey A

    2016-01-01

    In this paper I show that light-atom interaction can be described using purely classical field theory without any quantization. In particular, atom excitation by light that accounts for damping due to spontaneous emission is fully described in the framework of classical field theory. I show that three well-known laws of the photoelectric effect can also be derived and that all of its basic properties can be described within classical field theory.

  16. Negative refraction of ultra-cold atoms in optical lattices with nonuniform artificial gauge fields

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Ai-Xia, E-mail: zhangax@nwnu.edu.cn; Xue, Ju-Kui

    2016-07-01

    We theoretically study the reflection and refraction of ultra-cold atoms in optical lattices exposed to a nonuniform artificial magnetic field. The introduction of the nonuniform artificial magnetic field to the optical lattice for suitable designer magnetic potential barrier can lead to a series of intriguing reflection and refraction phenomena of atoms, including reflection, positive refraction, negative refraction and atomic matter wave splitting. Both the occurrence and the distribution of these reflection and refraction scenarios can be coherently controlled by the nonuniform artificial magnetic field. In particular, the regions close to the boundary of reflection demonstrate two more interesting propagation modes, i.e., a reflected branch of atoms comprising a positive or negative refracted branch of atoms with almost same atom population will be excited simultaneously at the magnetic potential barrier. The results can be a guide for the coherent control of the matter waves in optical lattices and the design of new atom optics devices. - Highlights: • Ultra-cold atoms in OL with nonuniform magnetic field are studied. • Matter wave reflection, refraction and splitting are coherently controlled. • Results provide a guide for the design of new atomic optics devices.

  17. Probing Magnetic Fields using the Giant Metrewave Radio Telescope

    CERN Document Server

    Farnes, J S; Kantharia, N G

    2013-01-01

    We present the first spectropolarimetric radio observations that apply Rotation Measure (RM) Synthesis to interferometric data from the Giant Metrewave Radio Telescope (GMRT) at 610 MHz. Spectropolarimetry requires measurement of a large number of instrumental systematics so that their effects can be calibrated - a technical problem that is currently being faced by the upcoming SKA pathfinders. Our fully-calibrated data allow for the peak Faraday depth and polarisation fraction to be measured for sub-mJy compact sources in the field of M51 at 610 MHz. The diffuse extended emission in the interacting galaxy pair is shown to be depolarised below the sensitivity limit. A survey of linear polarisation with the GMRT is now feasible and could be used to place constraints on the prevailing depolarisation mechanisms at low frequencies - improving polarised source count estimates and constraining the RM-grid observable with next generation facilities such as the SKA.

  18. Laser-Assisted Field Evaporation and Three-Dimensional Atom-by-Atom Mapping of Diamond Isotopic Homojunctions.

    Science.gov (United States)

    Mukherjee, Samik; Watanabe, Hideyuki; Isheim, Dieter; Seidman, David N; Moutanabbir, Oussama

    2016-02-10

    It addition to its high evaporation field, diamond is also known for its limited photoabsorption, strong covalent bonding, and wide bandgap. These characteristics have been thought for long to also complicate the field evaporation of diamond and make its control hardly achievable on the atomistic-level. Herein, we demonstrate that the unique behavior of nanoscale diamond and its interaction with pulsed laser lead to a controlled field evaporation thus enabling three-dimensional atom-by-atom mapping of diamond (12)C/(13)C homojunctions. We also show that one key element in this process is to operate the pulsed laser at high energy without letting the dc bias increase out of bounds for diamond nanotip to withstand. Herein, the role of the dc bias in evaporation of diamond is essentially to generate free charge carriers within the nanotip via impact ionization. The mobile free charges screen the internal electric field, eventually creating a hole rich surface where the pulsed laser is effectively absorbed leading to an increase in the nanotip surface temperature. The effect of this temperature on the uncertainty in the time-of-flight of an ion, the diffusion of atoms on the surface of the nanotip, is also discussed. In addition to paving the way toward a precise manipulation of isotopes in diamond-based nanoscale and quantum structures, this result also elucidates some of the basic properties of dielectric nanostructures under high electric field.

  19. Quantum Correlation of Two Entangled Atoms Interacting with the Binomial Optical Field

    Science.gov (United States)

    Liu, Tang-Kun; Tao, Yu; Shan, Chuan-Jia; Liu, Ji-bing

    2016-10-01

    Quantum correlations of two atoms in a system of two entangled atoms interacting with the binomial optical field are investigated. In eight different initial states of the two atoms, the influence of the strength of the dipole-dipole interaction, probabilities of a the Bernoulli trial and particle number of the binomial optical field on the temporal evolution of the geometrical quantum discord between two atoms are discussed. The result shows that two atoms always exist the correlation for different parameters. In addition, when and only when the two atoms are initially in the maximally entangled state, the temporal evolution of geometrical quantum discord is not affected by the parameters, and always keep in the degree of geometrical quantum discord that is a fixed value.

  20. Atomic and Electronic Structure of Quantum Dots Measured with Scanning Probe Techniques

    NARCIS (Netherlands)

    Sun, Z.

    2012-01-01

    This thesis deals with low temperature scanning tunneling microscopy/spectroscopy and atomic force microscopy (LT-STM/STS and AFM) studies on colloidal semiconductor and graphene quantum dots (g-QDs). These nanostructures are interesting because they show tunable electrical and optical properties du

  1. Quantitative analysis of hydrogen in SiO2/SiN/SiO2 stacks using atom probe tomography

    Directory of Open Access Journals (Sweden)

    Yorinobu Kunimune

    2016-04-01

    Full Text Available We have demonstrated that it is possible to reproducibly quantify hydrogen concentration in the SiN layer of a SiO2/SiN/SiO2 (ONO stack structure using ultraviolet laser-assisted atom probe tomography (APT. The concentration of hydrogen atoms detected using APT increased gradually during the analysis, which could be explained by the effect of hydrogen adsorption from residual gas in the vacuum chamber onto the specimen surface. The amount of adsorbed hydrogen in the SiN layer was estimated by analyzing another SiN layer with an extremely low hydrogen concentration (<0.2 at. %. Thus, by subtracting the concentration of adsorbed hydrogen, the actual hydrogen concentration in the SiN layer was quantified as approximately 1.0 at. %. This result was consistent with that obtained by elastic recoil detection analysis (ERDA, which confirmed the accuracy of the APT quantification. The present results indicate that APT enables the imaging of the three-dimensional distribution of hydrogen atoms in actual devices at a sub-nanometer scale.

  2. Reciprocity theory of apertureless scanning near-field optical microscopy with point-dipole probes.

    Science.gov (United States)

    Esslinger, Moritz; Vogelgesang, Ralf

    2012-09-25

    Near-field microscopy offers the opportunity to reveal optical contrast at deep subwavelength scales. In scanning near-field optical microscopy (SNOM), the diffraction limit is overcome by a nanoscopic probe in close proximity to the sample. The interaction of the probe with the sample fields necessarily perturbs the bare sample response, and a critical issue is the interpretation of recorded signals. For a few specific SNOM configurations, individual descriptions have been modeled, but a general and intuitive framework is still lacking. Here, we give an exact formulation of the measurable signals in SNOM which is easily applicable to experimental configurations. Our results are in close analogy with the description Tersoff and Hamann have derived for the tunneling currents in scanning tunneling microscopy. For point-like scattering probe tips, such as used in apertureless SNOM, the theory simplifies dramatically to a single scalar relation. We find that the measured signal is directly proportional to the field of the coupled tip-sample system at the position of the tip. For weakly interacting probes, the model thus verifies the empirical findings that the recorded signal is proportional to the unperturbed field of the bare sample. In the more general case, it provides guidance to an intuitive and faithful interpretation of recorded images, facilitating the characterization of tip-related distortions and the evaluation of novel SNOM configurations, both for aperture-based and apertureless SNOM.

  3. The dynamics of coupled atom and field assisted by continuous external pumping

    Energy Technology Data Exchange (ETDEWEB)

    Burlak, G.; Hernandez, J.A. [Centro de Investigacion en Ingenieria y Ciencias Aplicadas, Universidad Autonoma de Morelos, Cuernavaca, Morelos (Mexico); Starostenko, O. [Departamento de Fisica, Electronica, Sistemas y Mecatronica, Universidad de las Americas, 72820 Puebla (Mexico)

    2006-07-01

    The dynamics of a coupled system comprising a two-level atom and cavity field assisted by a continuous external classical field (driving Jaynes-Cummings model) is studied. When the initial field is prepared in a coherent state, the dynamics strongly depends on the algebraic sum of both fields. If this sum is zero (the compensative case) in the system, only the vacuum Rabi oscillations occur. The results with dissipation and external field detuning from the cavity field are also discussed. (Author)

  4. The Muonium Atom as a Probe of Physics beyond the Standard Model

    CERN Document Server

    Willmann, L

    1998-01-01

    The observed interactions between particles are not fully explained in the successful theoretical description of the standard model to date. Due to the close confinement of the bound state muonium ($M = \\mu^+ e^-$) can be used as an ideal probe of quantum electrodynamics and weak interaction and also for a search for additional interactions between leptons. Of special interest is the lepton number violating process of sponteanous conversion of muonium to antimuonium.

  5. [Connection of magnetic antisense probe with SK-Br-3 oncocyte mRNA nucleotide detected by high resolution atomic force microscope].

    Science.gov (United States)

    Tan, Shude; Ouyang, Yu; Li, Xinyou; Wen, Ming; Li, Shaolin

    2011-06-01

    The present paper is aimed to detect superparamagnetic iron oxide labeled c-erbB2 oncogene antisense oligonucleotide probe (magnetic antisense probe) connected with SK-Br-3 oncocyte mRNA nucleotide by high resolution atomic force microscope (AFM). We transfected SK-Br-3 oncocyte with magnetic antisense probe, then observed the cells by AFM with high resolution and detected protein expression and magnetic resonance imagine (MRI). The high resolution AFM clearly showed the connection of the oligonucleotide remote end of magnetic antisense probe with the mRNA nucleotide of oncocyte. The expression of e-erbB2 protein in SK-Br3 cells were highly inhibited by using magnetic antisense probe. We then obtained the lowest signal to noise ratio (SNR) of SK-Br-3 oncocyte transfected with magnetic antisense probe by MRI (PSK-Br-3 mRNA of tumor cell nuclear.

  6. Quantum-mechanical theory including angular momenta analysis of atom-atom collisions in a laser field

    Science.gov (United States)

    Devries, P. L.; George, T. F.

    1978-01-01

    The problem of two atoms colliding in the presence of an intense radiation field, such as that of a laser, is investigated. The radiation field, which couples states of different electronic symmetry, is described by the number state representation while the electronic degrees of freedom (plus spin-orbit interaction) are discussed in terms of a diabatic representation. The total angular momentum of the field-free system and the angular momentum transferred by absorption (or emission) of a photon are explicitly considered in the derivation of the coupled scattering equations. A model calculation is discussed for the Xe + F collision system.

  7. de Haas-van Alphen oscillations for neutral atoms in electric fields

    Science.gov (United States)

    Farias, B.; Furtado, C.

    2016-07-01

    The de Haas-van Alphen (dHvA) effect is well known as an oscillatory variation of the magnetization of conductors as a function of the inverse magnetic field and the frequency is proportional to the area of the Fermi surface. Here, we show that an analogous effect can occur for neutral atoms with a nonvanishing magnetic moment interacting with an electric field. Under an appropriate field-dipole configuration, the neutral atoms subject to a synthetic magnetic field arrange themselves in Landau levels. Using the Landau-Aharonov-Casher (LAC) theory, we obtain the energy eigenfunctions and eigenvalues as well as the degeneracy of the system. In a strong effective magnetic field regime we present the quantum oscillations in the energy and effective magnetization of a two-dimensional (2D) atomic gas. From the dHvA period we determine the area of the Fermi circle of the atomic cloud.

  8. Atom probe study of Cu-poor to Cu-rich transition during Cu(In,Ga)Se{sub 2} growth

    Energy Technology Data Exchange (ETDEWEB)

    Couzinie-Devy, F.; Cadel, E.; Pareige, P. [Groupe de Physique des Materiaux (GPM), UMR 6634 CNRS, Universite et INSA de Rouen, Avenue de l' Universite BP 12, 76801 Saint Etienne du Rouvray (France); Barreau, N.; Arzel, L. [Institut des Materiaux Jean Rouxel (IMN), UMR 6502 CNRS, 2 rue de la Houssiniere BP 32229, 44322 Nantes cedex 3 (France)

    2011-12-05

    Atomic scale chemistry of polycrystalline Cu(In,Ga)Se{sub 2} (CIGSe) thin film has been characterized at key points of the 3-stage process using atom probe tomography. 3D atom distributions have been reconstructed when the layer is Cu-poor ([Cu]/([Ga] + [In]) < 1), Cu-rich ([Cu]/([Ga] + [In]) > 1), and at the end of the process. Particular attention has been devoted to grain boundary composition and Na atomic distribution within the CIGSe layer. Significant variation of composition is highlighted during the growing process, providing fundamental information helping the understanding of high efficiency CIGSe formation.

  9. Interference Dynamics of Hydrogen Atoms in High-Frequency Dichromatic Laser Fields

    Science.gov (United States)

    Cheng, Tai-Wang; Li, Xiao-Feng; Fu, Pan-Ming; Chen, Shi-Gang

    2002-08-01

    We investigate the ionization and high-order harmonic generation of a hydrogen atom in high-frequency (several atomic units) super strong (up to several tens of atomic units) dichromatic laser fields. An effective iterative method in the framework of high-frequency Floquet theory is used in the calculations. We have considered two kinds of dichromatic laser field, i.e. 1ω-2ω and 1ω-3ω. We find that, in both the cases, the ionization and high-order harmonic generation show evident dependence on the relative phase and strength of the additional harmonic field. The dynamical origin of these interference effects is also discussed.

  10. Interference Dynamics of Hydrogen Atoms in High-Frequency Dichromatic Laser Fields

    Institute of Scientific and Technical Information of China (English)

    程太旺; 李晓峰; 傅盘铭; 陈式刚

    2002-01-01

    We investigate the ionization and high-order harmonic generation of a hydrogen atom in high-frequency (several atomic units) super strong (up to several tens of atomic units) dichromatic laser fields. An effective iterative method in the framework of high-frequency Floquet theory is used in the calculations. We have considered two kinds of dichromatic laser field, i.e. 1ω - 2ω and lω - 3ω. We find that, in both the cases, the ionization and high-order harmonic generation show evident dependence on the relative phase and strength of the additional harmonic field. The dynamical origin of these interference effects is also discussed.

  11. The effect of degenerate atomic levels on the field state dissipation in two-photon Jaynes-Cummings model

    Institute of Scientific and Technical Information of China (English)

    周玲; 宋鹤山; 李崇; 郭彦青

    2003-01-01

    The dissipation of the field in the two-photon Jaynes-Cummings model (JCM) with degenerate atomic levels was studied. The initial degenerate atomic state affects the field coherence loss. When the degenerate atom is initially in an equal probability superposition state, the field coherence loss is smallest. It is found that the degeneracy of the atomic level increases the period of entanglement between the atom and the field. When the degeneracy was considered, the coherence properties of the field could be affected by the reservoir qualitatively, if a nonlinear two-photon process is involved. This is different from the dissipation of one-photon JCM with degenerate atomic levels.

  12. Information Entropy Squeezing of a Two-Level Atom Interacting with Two-Mode Coherent Fields

    Institute of Scientific and Technical Information of China (English)

    LIU Xiao-Juan; FANG Mao-Fa

    2004-01-01

    From a quantum information point of view we investigate the entropy squeezing properties for a two-level atom interacting with the two-mode coherent fields via the two-photon transition. We discuss the influences of the initial state of the system on the atomic information entropy squeezing. Our results show that the squeezed component number,squeezed direction, and time of the information entropy squeezing can be controlled by choosing atomic distribution angle,the relative phase between the atom and the two-mode field, and the difference of the average photon number of the two field modes, respectively. Quantum information entropy is a remarkable precision measure for the atomic squeezing.

  13. Field-theory calculation of the electric dipole moment of the neutron and paramagnetic atoms

    Science.gov (United States)

    Griffith, Joel; Blundell, Steven; Sapirstein, Jonathan

    2013-04-01

    Electric dipole moments (edms) of bound states that arise from the constituents having edms are studied with field-theoretic techniques. The systems treated are the neutron and a set of paramagnetic atoms. In the latter case it is well known that the atomic edm differs greatly from the electron edm when the internal electric fields of the atom are taken into account. In the nonrelativistic limit these fields lead to a complete suppression, but for heavy atoms large enhancement factors are present. A general bound-state field theory approach applicable to both the neutron and paramagnetic atoms is set up. It is applied first to the neutron, treating the quarks as moving freely in a confining spherical well. It is shown that the effect of internal electric fields is small in this case. The atomic problem is then revisited using field-theory techniques in place of the usual Hamiltonian methods, and the atomic enhancement factor is shown to be consistent with previous calculations. Possible application of bound-state techniques to other sources of the neutron edm is discussed.

  14. Automation of the CHARMM General Force Field (CGenFF) I: bond perception and atom typing

    Science.gov (United States)

    Vanommeslaeghe, K.; MacKerell, A. D.

    2012-01-01

    Molecular mechanics force fields are widely used in computer-aided drug design for the study of drug-like molecules alone or interacting with biological systems. In simulations involving biological macromolecules, the biological part is typically represented by a specialized biomolecular force field, while the drug is represented by a matching general (organic) force field. In order to apply these general force fields to an arbitrary drug-like molecule, functionality for assignment of atom types, parameters and charges is required. In the present article, which is part I of a series of two, we present the algorithms for bond perception and atom typing for the CHARMM General Force Field (CGenFF). The CGenFF atom typer first associates attributes to the atoms and bonds in a molecule, such as valence, bond order, and ring membership among others. Of note are a number of features that are specifically required for CGenFF. This information is then used by the atom typing routine to assign CGenFF atom types based on a programmable decision tree. This allows for straightforward implementation of CGenFF’s complicated atom typing rules and for equally straightforward updating of the atom typing scheme as the force field grows. The presented atom typer was validated by assigning correct atom types on 477 model compounds including in the training set as well as 126 test-set molecules that were constructed to specifically verify its different components. The program may be utilized via an online implementation at https://www.paramchem.org/. PMID:23146088

  15. Automation of the CHARMM General Force Field (CGenFF) I: bond perception and atom typing.

    Science.gov (United States)

    Vanommeslaeghe, K; MacKerell, A D

    2012-12-21

    Molecular mechanics force fields are widely used in computer-aided drug design for the study of drug-like molecules alone or interacting with biological systems. In simulations involving biological macromolecules, the biological part is typically represented by a specialized biomolecular force field, while the drug is represented by a matching general (organic) force field. In order to apply these general force fields to an arbitrary drug-like molecule, functionality for assignment of atom types, parameters, and charges is required. In the present article, which is part I of a series of two, we present the algorithms for bond perception and atom typing for the CHARMM General Force Field (CGenFF). The CGenFF atom typer first associates attributes to the atoms and bonds in a molecule, such as valence, bond order, and ring membership among others. Of note are a number of features that are specifically required for CGenFF. This information is then used by the atom typing routine to assign CGenFF atom types based on a programmable decision tree. This allows for straightforward implementation of CGenFF's complicated atom typing rules and for equally straightforward updating of the atom typing scheme as the force field grows. The presented atom typer was validated by assigning correct atom types on 477 model compounds including in the training set as well as 126 test-set molecules that were constructed to specifically verify its different components. The program may be utilized via an online implementation at https://www.paramchem.org/ .

  16. Field-induced doping-mediated tunability in work function of Al-doped ZnO: Kelvin probe force microscopy and first-principle theory.

    Science.gov (United States)

    Kumar, Mohit; Mookerjee, Sumit; Som, Tapobrata

    2016-09-16

    We demonstrate that the work function of Al-doped ZnO (AZO) can be tuned externally by applying an electric field. Our experimental investigations using Kelvin probe force microscopy show that by applying a positive or negative tip bias, the work function of AZO film can be enhanced or reduced, which corroborates well with the observed charge transport using conductive atomic force microscopy. These findings are further confirmed by calculations based on first-principles theory. Tuning the work function of AZO by applying an external electric field is not only important to control the charge transport across it, but also to design an Ohmic contact for advanced functional devices.

  17. Field-induced doping-mediated tunability in work function of Al-doped ZnO: Kelvin probe force microscopy and first-principle theory

    Science.gov (United States)

    Kumar, Mohit; Mookerjee, Sumit; Som, Tapobrata

    2016-09-01

    We demonstrate that the work function of Al-doped ZnO (AZO) can be tuned externally by applying an electric field. Our experimental investigations using Kelvin probe force microscopy show that by applying a positive or negative tip bias, the work function of AZO film can be enhanced or reduced, which corroborates well with the observed charge transport using conductive atomic force microscopy. These findings are further confirmed by calculations based on first-principles theory. Tuning the work function of AZO by applying an external electric field is not only important to control the charge transport across it, but also to design an Ohmic contact for advanced functional devices.

  18. Squeezing effect of the cavity field in the two-atom Jay nes-Cummings model

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Authors investigate the model that two two-level atoms in terac t with a single-mode cavity. The formulation of the time evolution operator for the two-atom Jaynes-Cummings model is presented by the bare-states approach. Besides, squeezing effect of the cavity field is studied and some novel feature s are obtained.

  19. Photon statistical properties of the cavity field in the two-atom Jaynes-Cummings model

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The model that two two-level atoms interact with a singel-mode cavity is studied. The exact solution of the time evolution operator for the two-atom Jaynes-Cummings model is presented by the bare-states approach. Furthermore, we investigate the dynamical properties of the photon statistics of the cavity field, and obtain a number of novel features.

  20. Multiconfigurational self-consistent field calculations of nuclear shieldings using London atomic orbitals

    DEFF Research Database (Denmark)

    Ruud, Kenneth; Helgaker, Trygve; Kobayashi, Rika;

    1994-01-01

    Nuclear shielding calculations are presented for multiconfigurational self-consistent field wave functions using London atomic orbitals (gauge invariant atomic orbitals). Calculations of nuclear shieldings for eight molecules (H2O, H2S, CH4, N2, CO, HF, F2, and SO2) are presented and compared...

  1. Probing the short range spin dependent interactions by polarized {sup 3}He atom beams

    Energy Technology Data Exchange (ETDEWEB)

    Yan, H. [China Academy of Engineering Physics, Institute of Nuclear Physics and Chemistry, Mianyang, Sichuan (China); Indiana University, Center for Exploration of Energy and Matter, Bloomington, IN (United States); Sun, G.A.; Gong, J.; Pang, B.B.; Wang, Y.; Yang, Y.W.; Zhang, J.; Zhang, Y. [China Academy of Engineering Physics, Institute of Nuclear Physics and Chemistry, Mianyang, Sichuan (China)

    2014-10-15

    Experiments using polarized {sup 3}He atom beams to search for short range spin dependent forces are proposed. High intensity, high polarization, small beam size {sup 3}He atom beams have been successfully produced and used in surface science researches. By incorporating background reduction designs as combination shielding by μ-metal and superconductor and double beam paths, the precision of spin rotation angle per unit length could be improved by a factor of ∝ 10{sup 4}. By this precision, in combination with a high density and low magnetic susceptibility sample source mass, and reversing one beam path if necessary, sensitivities on three different types of spin dependent interactions could be improved by as much as ∝ 10{sup 2} to ∝ 10{sup 8} over the current experiments at the millimeter range. (orig.)

  2. Laser spectroscopic probing of coexisting superfluid and insulating states of an atomic Bose-Hubbard system

    Science.gov (United States)

    Kato, Shinya; Inaba, Kensuke; Sugawa, Seiji; Shibata, Kosuke; Yamamoto, Ryuta; Yamashita, Makoto; Takahashi, Yoshiro

    2016-04-01

    A system of ultracold atoms in an optical lattice has been regarded as an ideal quantum simulator for a Hubbard model with extremely high controllability of the system parameters. While making use of the controllability, a comprehensive measurement across the weakly to strongly interacting regimes in the Hubbard model to discuss the quantum many-body state is still limited. Here we observe a great change in the excitation energy spectra across the two regimes in an atomic Bose-Hubbard system by using a spectroscopic technique, which can resolve the site occupancy in the lattice. By quantitatively comparing the observed spectra and numerical simulations based on sum rule relations and a binary fluid treatment under a finite temperature Gutzwiller approximation, we show that the spectra reflect the coexistence of a delocalized superfluid state and a localized insulating state across the two regimes.

  3. Probing Electronic States of Magnetic Semiconductors Using Atomic Scale Microscopy & Spectroscopy

    Science.gov (United States)

    2013-12-01

    N000140710348 Final Report as of December 2013 Objective: This project was focused on the application of the scanning tunneling microscopy (STM...magnetic atoms on the surface of a superconductor can be used as a versatile platform for creating a topological superconductor . These initial...the application of the scanning tunneling microscopy (STM) to understand the electronic structure of magnetically doped semiconductors and to develop

  4. Probing the electric field in organic double layer-system by optical second harmonic generation

    Energy Technology Data Exchange (ETDEWEB)

    Lim, Eunju; Shibata, Yoshinori; Manaka, Takaaki [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552 (Japan); Iwamoto, Mitsumasa, E-mail: iwamoto@ome.pe.titech.ac.j [Department of Physical Electronics, Tokyo Institute of Technology, 2-12-1 O-okayama, Meguro-ku, Tokyo 152-8552 (Japan)

    2009-11-30

    Optical electric field induced second harmonic generation (EFISHG) measurements were employed to probe the electric field in the active layer of organic field effect transistors (OFETs) and organic light emitting diodes (OLEDs). The OFETs used were double-layered with an active layer of pentacene/poly (3-hexyl thiophene) P3HT on SiO{sub 2} gate insulator with Au source and drain electrodes. It was shown that SHG from the P3HT bottom layer could be selectively probed at a wavelength of 450 nm. Similarly, by using OLEDs comprised of a double layer of Tris(8-hydroxyquinolinato) aluminium (Alq{sub 3}) and N'-di(1-naphthyl)-N,N'-diphenylbenzidine ({alpha}-NPD) with a device structure of indium-zinc oxide (IZO)/{alpha}-NPD/Alq{sub 3}/Al, it was shown that EFISHG from the Alq{sub 3} layer could be selectively probed at a wavelength of 1000 nm by reflective laser beam irradiation from IZO-side. The results show that the spectroscopic nature of materials allows us to selectively probe the electric field distribution in each layer of multi-layer in organic devices.

  5. Graphene-like optical light field and its interaction with two-level atoms

    Science.gov (United States)

    Lembessis, V. E.; Courtial, Johannes; Radwell, N.; Selyem, A.; Franke-Arnold, S.; Aldossary, O. M.; Babiker, M.

    2015-12-01

    The theoretical basis leading to the creation of a light field with a hexagonal honeycomb structure resembling graphene is considered along with its experimental realization and its interaction with atoms. It is argued that associated with such a light field is an optical dipole potential which leads to the diffraction of the atoms, but the details depend on whether the transverse spread of the atomic wave packet is larger than the transverse dimensions of the optical lattice (resonant Kapitza-Dirac effect) or smaller (optical Stern-Gerlach effect). Another effect in this context involves the creation of gauge fields due to the Berry phase acquired by the atom moving in the light field. The experimental realization of the light field with a honeycomb hexagonal structure is described using holographic methods and we proceed to explore the atom diffraction in the Kapitza-Dirac regime as well as the optical Stern-Gerlach regime, leading to momentum distributions with characteristic but different hexagonal structures. The artificial gauge fields too are shown to have the same hexagonal spatial structure and their magnitude can be significantly large. The effects are discussed with reference to typical parameters for the atoms and the fields.

  6. Graphene Coatings: Probing the Limits of the One Atom Thick Protection Layer

    DEFF Research Database (Denmark)

    Nilsson, Louis; Andersen, Mie; Balog, Richard

    2012-01-01

    The limitations of graphene as an effective corrosion-inhibiting coating on metal surfaces, here exemplified by the hex-reconstructed Pt(100) surface, are probed by scanning tunneling microscopy measurements and density functional theory calculations. While exposure of small molecules directly onto...... the Pt(100) surface will lift the reconstruction, a single graphene layer is observed to act as an effective coating, protecting the reactive surface from O2 exposure and thus preserving the reconstruction underneath the graphene layer in O2 pressures as high as 104 mbar. A similar protective effect...

  7. A fast response miniature probe for wet steam flow field measurements

    Science.gov (United States)

    Bosdas, Ilias; Mansour, Michel; Kalfas, Anestis I.; Abhari, Reza S.

    2016-12-01

    Modern steam turbines require operational flexibility due to renewable energies’ increasing share of the electrical grid. Additionally, the continuous increase in energy demand necessitates efficient design of the steam turbines as well as power output augmentation. The long turbine rotor blades at the machines’ last stages are prone to mechanical vibrations and as a consequence time-resolved experimental data under wet steam conditions are essential for the development of large-scale low-pressure steam turbines. This paper presents a novel fast response miniature heated probe for unsteady wet steam flow field measurements. The probe has a tip diameter of 2.5 mm, and a miniature heater cartridge ensures uncontaminated pressure taps from condensed water. The probe is capable of providing the unsteady flow angles, total and static pressure as well as the flow Mach number. The operating principle and calibration procedure are described in the current work and a detailed uncertainty analysis demonstrates the capability of the new probe to perform accurate flow field measurements under wet steam conditions. In order to exclude any data possibly corrupted by droplets’ impact or evaporation from the heating process, a filtering algorithm was developed and implemented in the post-processing phase of the measured data. In the last part of this paper the probe is used in an experimental steam turbine test facility and measurements are conducted at the inlet and exit of the last stage with an average wetness mass fraction of 8.0%.

  8. Control of light trapping in a large atomic system by a static magnetic field

    CERN Document Server

    Skipetrov, S E; Havey, M D

    2016-01-01

    We propose to control light trapping in a large ensemble of cold atoms by an external, static magnetic field. For an appropriate choice of frequency and polarization of the exciting pulse, the field is expected to speed up the fluorescence of a dilute atomic system but can significantly slow it down in a dense ensemble. The slowing down of fluorescence is due to the excitation of spatially localized collective atomic states that appear only under a strong magnetic field and have exponentially long lifetimes. The control of fluorescence by the magnetic field may be of interest for use in future quantum-information processing devices. It also paves a way towards the experimental observation of the disorder-induced localization of light in cold atomic systems.

  9. Control of light trapping in a large atomic system by a static magnetic field

    Science.gov (United States)

    Skipetrov, S. E.; Sokolov, I. M.; Havey, M. D.

    2016-07-01

    We propose to control light trapping in a large ensemble of cold atoms by an external, static magnetic field. For an appropriate choice of frequency and polarization of the exciting pulse, the field is expected to speed up the fluorescence of a dilute atomic system. In a dense ensemble, the field does not affect the early-time superradiant signal but amplifies intensity oscillations at intermediate times and induces a very slow, nonexponential long-time decay. The slowing down of fluorescence is due to the excitation of spatially localized collective atomic states that appear only under a strong magnetic field and have exponentially long lifetimes. Our results therefore pave a way towards experimental observation of the disorder-induced localization of light in cold atomic systems.

  10. A new united atom force field for adsorption of alkenes in zeolites

    NARCIS (Netherlands)

    Liu, B.; Smit, B.; Rey, F.; Valencia, S.; Calero, S.

    2008-01-01

    A new united atom force field was developed that accurately describes the adsorption properties of linear alkenes in zeolites. The force field was specifically designed for use in the inhomogeneous system and therefore a truncated and shifted potential was used. With the determined force field, we p

  11. The Multiphoton Interaction of Lambda Model Atom and Two-Mode Fields

    Science.gov (United States)

    Liu, Tang-Kun

    1996-01-01

    The system of two-mode fields interacting with atom by means of multiphotons is addressed, and the non-classical statistic quality of two-mode fields with interaction is discussed. Through mathematical calculation, some new rules of non-classical effects of two-mode fields which evolue with time, are established.

  12. Faithfully probabilistic teleportation of an unknown atomic state and cavity field state with a single measurement

    Institute of Scientific and Technical Information of China (English)

    Yang Zhen-Biao; Wu Huai-Zhi; Su Wan-Jun; Zhong Zhi-Rong; Zheng Shi-Biao

    2007-01-01

    This paper shows that, based on the single-photon JC model depicting the resonant interaction of a two-level atom with a single cavity mode, an unknown atomic state and cavity photon superposition state can be faithfully teleported with only a single measurement. The scheme is probabilistic, its success lies on the event that the sender atom (or the medi-atom, for teleportation of cavity field state) is detected in the higher state. The scheme is in contrast to the previous ones of using a maximally two-particle entangled state as quantum channel.

  13. Data analysis and other considerations concerning the study of precipitation in Al–Mg–Si alloys by Atom Probe Tomography

    Directory of Open Access Journals (Sweden)

    M.W. Zandbergen

    2015-12-01

    Full Text Available Atom Probe Tomography (APT analysis and hardness measurements were used to characterize the early stages of precipitation in an Al–0.51 at%Mg–0.94 at%Si alloy as reported in the accompanying Acta Materialia paper [1]. The changes in microstructure were investigated after single-stage or multi-stage heat treatments including natural ageing at 298 K (NA, pre-ageing at 353 K (PA, and automotive paint-bake ageing conditions at 453 K (PB. This article provides Supporting information and a detailed report on the experimental conditions and the data analysis methods used for this investigation. Careful design of experimental conditions and analysis methods was carried out to obtain consistent and reliable results. Detailed data on clustering for prolonged NA and PA treatments have been reported.

  14. Chemical gradients across phase boundaries between martensite and austenite in steel studied by atom probe tomography and simulation

    Energy Technology Data Exchange (ETDEWEB)

    Dmitrieva, O.; Ponge, D.; Inden, G.; Millan, J.; Choi, P. [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 40237 Duesseldorf (Germany); Sietsma, J. [Delft University of Technology, Faculty 3mE, Dept. MSE, 2628 CD Delft (Netherlands); Raabe, D., E-mail: d.raabe@mpie.de [Max-Planck-Institut fuer Eisenforschung, Max-Planck-Str. 1, 40237 Duesseldorf (Germany)

    2011-01-15

    Partitioning at phase boundaries of complex steels is important for their properties. We present atom probe tomography results across martensite/austenite interfaces in a precipitation-hardened maraging-TRIP steel (12.2 Mn, 1.9 Ni, 0.6 Mo, 1.2 Ti, 0.3 Al; at.%). The system reveals compositional changes at the phase boundaries: Mn and Ni are enriched while Ti, Al, Mo and Fe are depleted. More specific, we observe up to 27 at.% Mn in a 20 nm layer at the phase boundary. This is explained by the large difference in diffusivity between martensite and austenite. The high diffusivity in martensite leads to a Mn flux towards the retained austenite. The low diffusivity in the austenite does not allow accommodation of this flux. Consequently, the austenite grows with a Mn composition given by local equilibrium. The interpretation is based on DICTRA and mixed-mode diffusion calculations (using a finite interface mobility).

  15. Design and implementation of precise position controller of active probe of atomic force microscopy for nanomanipulation

    Institute of Scientific and Technical Information of China (English)

    HAO LiNa; ZHANG JiangBo; XI Ning

    2008-01-01

    Efficiency and accuracy of AFM-based nanomanipulation are still major problems to be solved,due to the nonlinearities and uncertainties,such as drift,creep,hysteresis,etc.The deformation of cantilevers caused by manipulation force is also one of the most major factors of nonlinearities and uncertainties.It causes difficulties in precise control of the tip position and causes the tip to miss the position of the object.In order to solve this problem,the traditional approach is to use a rigid cantilever.However,this will significantly reduce the sensitivity of force sensing during manipulation,which is essential for achieving an efficient and reliable nanomanipulation.In this paper,a kind of active AFM probe has been used to solve this problem by directly controlling the cantilever's flexibility or rigidity during manipu- lation.Based on Euller-Bernoulli Model,a kind of controller of the active probe employing Peri- odic-Output-Feedback (POF) law is implemented.The results of simulation and experiments have demonstrated that this theoretical model and POF controller are suitable for precise position control of nanomanipulation.

  16. Radio-Frequency Field-Induced Quantum Interference Effects in Cold Atoms

    Institute of Scientific and Technical Information of China (English)

    龙全; 周蜀渝; 周善钰; 王育竹

    2001-01-01

    We propose constructing a quantum interference configuration for cold atoms in a magneto-optical trap by applying a radio frequency field, which coherently couples adjacent Zeeman sublevels, in combination with a repumping laser field. One effect of this interference is that a dip exists in the absorption of the repumping light when the radio frequency is scanned. Our prediction has been indirectly detected through the fluorescence of cold atoms in a preliminary experiment.

  17. Atomic and field dynamics in the time-dependent Jaynes-Cummings model with arbitrary detuning

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    We propose a general numerical method for solving the time -dependent Jaynes-Cummings model with arbitrary detuning by integrating relate d groups of coupled equations using Runge-Kutta numerical technique. The atomic and field dynamics such as evolution of atomic population inversion and second -order correlation function of photons are studied in case of different detunin g. The results show that the field tends to exhibit bunching effect due to the I ncreasing of detuning.

  18. Knee structure in double ionization of noble atoms in circularly polarized laser fields

    Science.gov (United States)

    Chen, Xiang; Wu, Yan; Zhang, Jingtao

    2017-01-01

    Nonsequential double ionization is characterized by a knee structure in the plot of double-ionization probability versus laser intensity. In circularly polarized (CP) laser fields, this structure has only been observed for Mg atoms. By choosing laser fields according to a scaling law, we exhibit the knee structure in CP laser fields for Ar and He atoms. The collision of the ionized electron with the core enhances the ionization of the second electron and forms the knee structure. The electron recollision is universal in CP laser fields, but the ionization probability in the knee region decreases as the wavelength of the driven field increases. For experimental observations, it is beneficial to use target atoms with small ionization potentials and laser fields with short wavelengths.

  19. Investigation of the self tempering effect of martensite by means of atom probe tomography; Untersuchung des Selbstanlasseffektes von Martensit mit Hilfe von Atomsondentomographie

    Energy Technology Data Exchange (ETDEWEB)

    Sackl, Stephanie [Montanuniv. Leoben (Austria). Christian Doppler Labor ' ' Early Stages of Precipitation' ' ; Clemens, Helmut; Primig, Sophie [Montanuniv. Leoben (Austria). Dept. of Physical Metallurgy and Materials Testing

    2015-10-01

    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.

  20. Probing characteristics of collagen molecules on various surfaces via atomic force microscopy

    Science.gov (United States)

    Su, Hao-Wei; Ho, Mon-Shu; Cheng, Chao-Min

    2012-06-01

    We examine, herein, specific dynamic responses of collagen molecules (i.e., observations of self-assembly and nanometric adhesion force measurements of type-I collagen molecules) as they interact with either a hydrophobic or a hydrophilic surface at two distinct temperatures, using a liquid-type atomic force microscope. We conclude that, regardless of surface hydrophobicity/hydrophilicity, assembled microfibrils eventually distribute homogeneously in accordance with changes in surface-related mechanical properties of collagen molecules at different self-assembly stages.

  1. Probing molecular interaction between transferrin and anti-transferrin by atomic force microscope

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The interaction between transferrin (Tf) and its antibody was investigated by atomic force microscope. Tf-antibody was immobilized on the Au-coated glass slide, and the specific combination between antibody and antigen was also characterized by AFM. The results showed that holo-transferrin was jogged with anti-transferrin, and binded anti-tran- sferrin more tightly than apo-transferrin. The force- distance curves revealed that the affinity of anti-trans- ferrin and holo-transferrin was much stronger than that of apo-transferrin.

  2. DNA flexibility on short length scales probed by atomic force microscopy.

    Science.gov (United States)

    Mazur, Alexey K; Maaloum, Mounir

    2014-02-14

    Unusually high bending flexibility has been recently reported for DNA on short length scales. We use atomic force microscopy (AFM) in solution to obtain a direct estimate of DNA bending statistics for scales down to one helical turn. It appears that DNA behaves as a Gaussian chain and is well described by the wormlike chain model at length scales beyond 3 helical turns (10.5 nm). Below this threshold, the AFM data exhibit growing noise because of experimental limitations. This noise may hide small deviations from the Gaussian behavior, but they can hardly be significant.

  3. Atom probe analysis on interaction between Cr and N in bake-hardening steels with anti-aging properties at RT

    Energy Technology Data Exchange (ETDEWEB)

    Takahashi, Jun, E-mail: takahashi.3ct.jun@jp.nssmc.com [Advanced Technology Research Laboratories, Nippon Steel and Sumitomo Metal Corporation, 20-1, Shintomi, Futtsu-city, Chiba 293-8511 (Japan); Maruyama, Naoki; Kawakami, Kazuto; Yoshinaga, Naoki; Sugiyama, Masaaki [Advanced Technology Research Laboratories, Nippon Steel and Sumitomo Metal Corporation, 20-1, Shintomi, Futtsu-city, Chiba 293-8511 (Japan); Ohkubo, Tadakatsu; Ping, De-hai; Hono, Kazuhiro [National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, Ibaraki 305-0047 (Japan)

    2013-11-15

    One-dimensional atom probe (1DAP) analysis was performed on chromium and nitrogen added bake hardening steel sheets that have both high bake-hardenability and anti-aging properties at room temperature (RT). The atomic data of more than 2 million atoms were collected for sample steels with and without low-temperature aging after recrystallization annealing and quenching. The correlation in atomic position between chromium and nitrogen atoms in a solid solution was investigated by a statistical analysis using the binomial distribution function. In the samples with low-temperature aging, the probability that a chromium atom was observed near a nitrogen atom was significantly higher than that estimated from the null hypothesis that there was no attractive atomic interaction. This suggests that there is an attractive interaction between a nitrogen atom and a chromium atom in bcc iron, which led to the anti-aging properties at RT. In contrast, such correlation was not observed definitely in the samples without low-temperature aging, which implied that the atomic pair formation is a thermal activation process.

  4. Fine structure in a strong magnetic field: Paschen-Back effect reconsidered in Rydberg atoms

    Science.gov (United States)

    Liu, Wenyu; Gu, Sihong; Li, Baiwen

    1996-05-01

    Using a kind of potential model wave function for alkali metal atoms, we nonperturbatively study the effect of fine structure on the Rydberg spectra of Cs atom in a strong magnetic field. Our numerical results reveal spectral structure dramatically different from the well-established Paschen-Back effect, and we argue that the fine structure of the Rydberg Cs atom cannot be neglected even in a magnetic field as strong as several teslas. We also give an error estimate of our results and a word on possible experimental verification.

  5. Bifurcations in the hydrogen atom in the presence of a circularly polarized microwave field and a static magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Lanchares, V. [Departamento de Matematicas y Computacion, Universidad de La Rioja, 26004 Logrono (Spain); Inarrea, M.; Salas, J.P. [Area de Fisica Aplicada, Universidad de La Rioja, 26004 Logrono (Spain)

    1997-09-01

    In a classical model, the dynamics of the hydrogen atom subjected to a circularly polarized microwave field and a magnetic field is shown to belong to the family of so-called biparametric quadratic Hamiltonians. The energy-level structure is studied in terms of the parametric bifurcations. {copyright} {ital 1997} {ital The American Physical Society}

  6. Analysis of Near-Field Diffraction Pattern of a Metallic Probe Tip with the Boundary Diffraction Wave Method

    Institute of Scientific and Technical Information of China (English)

    TANG Lin; GU Chun; CHEN Bo; WANG Pei; MING Hai; XIE Jian-Ping

    2005-01-01

    @@ The boundary diffraction wave theory is introduced to analyse a near-field diffraction (NFD) pattern of a metallic probe tip of apertureless scanning near-field microscopy. This method is simple and can give a clear physical picture. The polarization effect of the incident light and the different shapes of the metallic probe tip are simulated. The results show that the NFD pattern of the metallic probe tip is directly related to those factors.

  7. Probing deviations from traditional colloid filtration theory by atomic forces microscopy.

    Energy Technology Data Exchange (ETDEWEB)

    Reno, Marissa Devan

    2005-12-01

    Colloid transport through saturated media is an integral component of predicting the fate and transport of groundwater contaminants. Developing sound predictive capabilities and establishing effective methodologies for remediation relies heavily on our ability to understand the pertinent physical and chemical mechanisms. Traditionally, colloid transport through saturated media has been described by classical colloid filtration theory (CFT), which predicts an exponential decrease in colloid concentration with travel distance. Furthermore, colloid stability as determined by Derjaguin-Landau-Veney-Overbeek (DLVO) theory predicts permanent attachment of unstable particles in a primary energy minimum. However, recent studies show significant deviations from these traditional theories. Deposition in the secondary energy minimum has been suggested as a mechanism by which observed deviations can occur. This work investigates the existence of the secondary energy minimum as predicted by DLVO theory using direct force measurements obtained by Atomic Forces Microscopy. Interaction energy as a function of separation distance between a colloid and a quartz surface in electrolyte solutions of varying ionic strength are obtained. Preliminary force measurements show promise and necessary modifications to the current experimental methodology have been identified. Stringent surface cleaning procedures and the use of high-purity water for all injectant solutions is necessary for the most accurate and precise measurements. Comparisons between direct physical measurements by Atomic Forces Microscopy with theoretical calculations and existing experimental findings will allow the evaluation of the existence or absence of a secondary energy minimum.

  8. Atomic Interference Method for Direct Measurement of the Wigner Function of aCavity Field

    Institute of Scientific and Technical Information of China (English)

    ZHENG Shi-Biao

    2001-01-01

    We propose a scheme for the reconstruction of a cavity field state. In the scheme the cavity field is first displaced by a microwave source, and then is placed in front of one slit of the two-slit apparatus. Ground state atoms pass through the apparatus, hitting upon the screen far away from the two-slit apparatus. The atom-field interaction is dispersive. The contrast of interference fringes is directly related to the Wigner function for the field state. The scheme can be easily generalized to measure the Wigner function of an entangled state of two spatially separated single-mode cavities.

  9. Indium clustering in a-plane InGaN quantum wells as evidenced by atom probe tomography

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Fengzai; Zhu, Tongtong; Oehler, Fabrice; Fu, Wai Yuen; Griffiths, James T.; Massabuau, Fabien C.-P.; Kappers, Menno J.; Oliver, Rachel A., E-mail: rao28@cam.ac.uk [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom); Martin, Tomas L.; Bagot, Paul A. J.; Moody, Michael P., E-mail: michael.moody@materials.ox.ac.uk [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom)

    2015-02-16

    Atom probe tomography (APT) has been used to characterize the distribution of In atoms within non-polar a-plane InGaN quantum wells (QWs) grown on a GaN pseudo-substrate produced using epitaxial lateral overgrowth. Application of the focused ion beam microscope enabled APT needles to be prepared from the low defect density regions of the grown sample. A complementary analysis was also undertaken on QWs having comparable In contents grown on polar c-plane sample pseudo-substrates. Both frequency distribution and modified nearest neighbor analyses indicate a statistically non-randomized In distribution in the a-plane QWs, but a random distribution in the c-plane QWs. This work not only provides insights into the structure of non-polar a-plane QWs but also shows that APT is capable of detecting as-grown nanoscale clustering in InGaN and thus validates the reliability of earlier APT analyses of the In distribution in c-plane InGaN QWs which show no such clustering.

  10. Resolving phase information of the optical local density of state with scattering near-field probes

    Science.gov (United States)

    Prasad, R.; Vincent, R.

    2016-10-01

    We theoretically discuss the link between the phase measured using a scattering optical scanning near-field microscopy (s-SNOM) and the local density of optical states (LDOS). A remarkable result is that the LDOS information is directly included in the phase of the probe. Therefore by monitoring the spatial variation of the trans-scattering phase, we locally measure the phase modulation associated with the probe and the optical paths. We demonstrate numerically that a technique involving two-phase imaging of a sample with two different sized tips should allow to obtain the image the pLDOS. For this imaging method, numerical comparison with extinction probe measurement shows crucial qualitative and quantitative improvement.

  11. Field testing of a probe to measure fouling in an industrial flue gas stream

    Energy Technology Data Exchange (ETDEWEB)

    Sohal, M.S.

    1990-11-01

    The US Department of Energy, Office of Industrial Technology sponsors work in the area of measuring and mitigating fouling in heat exchangers. This report describes the design and fabrication of a gas-side fouling measuring device, and its testing in an industrial environment. The report gives details of the probe fabrication, material used, controllers, other instrumentation required for various measurements, and computer system needed for recording the data. The calibration constants for measuring the heat flux with the heat fluxmeter were determined. The report also describes the field test location, the tests performed, the data collected, and the data analysis. The conclusions of the tests performed were summarized. Although fouling deposits on the probe were minimal, the tests proved that the probe is capable of measuring the fouling in a harsh industrial environment. 17 refs., 19 figs., 5 tabs.

  12. Measurements Using a Scanning Near-Field Coaxial Probe Microwave Microscope

    Science.gov (United States)

    Steinhauer, David E.; Vlahacos, C. P.; Dutta, Sudeep; Wellstood, F. C.; Anlage, Steven M.

    1997-03-01

    We have developed a scanning near-field microwave microscope using an open-ended coaxial probe.(C. P. Vlahacos, et al.) Appl. Phys. Lett. 69, 3272 (1996)^,(S. M. Anlage, et al.) IEEE Trans. Appl. Supercond. (1997) The probe is connected to a coaxial transmission line, which acts as a resonant microwave circuit. The probe is scanned over a sample while microwave energy is fed into the other end of the coaxial line. The quantities that can be measured simultaneously during a scan are shifts in the resonant frequencies, amplitude of the resonant peaks, quality factor of the circuit, and changes in phase relative to the microwave source. We will show images and discuss the theory of how the data are related to properties of the sample.

  13. Atomic force microscopy and spectroscopy to probe single membrane proteins in lipid bilayers.

    Science.gov (United States)

    Sapra, K Tanuj

    2013-01-01

    The atomic force microscope (AFM) has opened vast avenues hitherto inaccessible to the biological scientist. The high temporal (millisecond) and spatial (nanometer) resolutions of the AFM are suited for studying many biological processes in their native conditions. The AFM cantilever stylus is aptly termed as a "lab on a tip" owing to its versatility as an imaging tool as well as a handle to manipulate single bonds and proteins. Recent examples assert that the AFM can be used to study the mechanical properties and monitor processes of single proteins and single cells, thus affording insight into important mechanistic details. This chapter specifically focuses on practical and analytical protocols of single-molecule AFM methodologies related to high-resolution imaging and single-molecule force spectroscopy of membrane proteins. Both these techniques are operator oriented, and require specialized working knowledge of the instrument, theoretical, and practical skills.

  14. Direct probe of anisotropy in atom-molecule collisions via quantum scattering resonances

    CERN Document Server

    Klein, Ayelet; Skomorowski, Wojciech; Żuchowski, Piotr S; Pawlak, Mariusz; Janssen, Liesbeth M C; Moiseyev, Nimrod; van de Meerakker, Sebastiaan Y T; van der Avoird, Ad; Koch, Christiane P; Narevicius, Edvardas

    2016-01-01

    Anisotropy is a fundamental property of particle interactions. It occupies a central role in cold and ultra-cold molecular processes, where long range forces have been found to significantly depend on orientation in ultra-cold polar molecule collisions. Recent experiments have demonstrated the emergence of quantum phenomena such as scattering resonances in the cold collisions regime due to quantization of the intermolecular degrees of freedom. Although these states have been shown to be sensitive to interaction details, the effect of anisotropy on quantum resonances has eluded experimental observation so far. Here, we directly measure the anisotropy in atom-molecule interactions via quantum resonances by changing the quantum state of the internal molecular rotor. We observe that a quantum scattering resonance at a collision energy of $k_B$ x 270 mK appears in the Penning ionization of molecular hydrogen with metastable helium only if the molecule is rotationally excited. We use state of the art ab initio and ...

  15. The magneto-optical effect of cold atoms in an integrating sphere for atomic clock and optical magnetometer

    CERN Document Server

    Wan, Jinyin; Meng, Yanling; Xiao, Ling; Liu, Peng; Wang, Xiumei; Wang, Yaning; Liu, Liang

    2014-01-01

    We investigate the magneto-optical effect of cold atoms in an integrating sphere both experimentally and theoretically. The dependence of magneto-optical rotation angle on the biased magnetic field, the probe light intensity, and the probe light detuning are investigated. The probe light background is blocked and the shot noise is strongly suppressed. This detection scheme may provide a new approach for high contrast cold atom clock and cold atom optical magnetometer.

  16. Stray magnetic field compensation with a scalar atomic magnetometer

    Science.gov (United States)

    Belfi, J.; Bevilacqua, G.; Biancalana, V.; Cecchi, R.; Dancheva, Y.; Moi, L.

    2010-06-01

    We describe a system for the compensation of time-dependent stray magnetic fields using a dual channel scalar magnetometer based on nonlinear Faraday rotation in synchronously optically pumped Cs vapor. We detail the active control strategy, with an emphasis on the electronic circuitry, based on a simple phase-locked-loop integrated circuit. The performance and limits of the system developed are tested and discussed. The system was applied to significantly improve the detection of free induction decay signals from protons of remotely magnetized water precessing in an ultralow magnetic field.

  17. Stray Magnetic Field Compensation with a Scalar Atomic Magnetometer

    CERN Document Server

    Belfi, Jacopo; Biancalana, Valerio; Cecchi, Roberto; Dancheva, Yordanka; Moi, Luigi

    2010-01-01

    We describe a system for the compensation of time-dependent stray magnetic fields using a dual channel scalar magnetometer based on non-linear Faraday rotation in synchronously optically pumped Cs vapour. We detail the active control strategy, with an emphasis on the electronic circuitry, based on a simple phase-locked-loop integrated circuit. The performance and limits of the system developed are tested and discussed. The system was applied to significantly improve the detection of free induction decay signals from protons of remotely magnetized water precessing in an ultra-low magnetic field.

  18. Effects of Laser Energy and Wavelength on the Analysis of LiFePO4 Using Laser Assisted Atom Probe Tomography

    Energy Technology Data Exchange (ETDEWEB)

    Santhanagopalan, Dhamodaran; Schreiber, Daniel K.; Perea, Daniel E.; Martens, Rich; Janssen, Yuri; Kalifah, Peter; Meng, Ying S.

    2015-01-21

    The effects of laser wavelength (355 nm and 532 nm) and laser pulse energy on the quantitative accuracy of atom probe tomography (APT) examinations of LiFePO4 (LFP) are considered. A systematic investigation of ultraviolet (UV, 355 nm) and green (532 nm) laser assisted APT of LFP has revealed distinctly different behaviors. With the use of UV laser the major issue was identified as the preferential loss of oxygen (up to 10 at. %) while other elements (Li, Fe and P) were observed to be close to nominal ratios. Lowering the laser energy per pulse to 1 pJ increased the observed oxygen concentration to near its correct stoichiometry and was well correlated with systematically higher concentrations of 16O2+ ions. This observation supports the premise that lower laser energies lead to a higher probability of oxygen molecule ionization. Conversely, at higher laser energies the resultant lower effective electric field reduces the probability of oxygen molecule ionization. Green laser assisted field evaporation led to the selective loss of Li (~50% deficiency) and correct ratios of the remaining elements, including the oxygen concentration. The loss of Li is explained by selective dc evaporation of lithium between laser pulses and relatively negligible oxygen loss as neutrals during green-laser pulsing. Lastly, plotting of multihit events on a Saxey plot for the straight-flight path data (green laser only) revealed a surprising dynamic recombination process for some molecular ions mid-flight.

  19. Model-independent measurement of the charge density distribution along an Fe atom probe needle using off-axis electron holography without mean inner potential effects

    Energy Technology Data Exchange (ETDEWEB)

    Migunov, V., E-mail: v.migunov@fz-juelich.de; Dunin-Borkowski, R. E. [Ernst Ruska-Centre for Microscopy and Spectroscopy with Electrons (ER-C) and Peter Grünberg Institute (PGI), Forschungszentrum Jülich, D-52425 Jülich (Germany); London, A. [Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH (United Kingdom); Farle, M. [Fakultät für Physik and Center of Nanointegration (CeNIDE), Universität Duisburg-Essen, D-47048 Duisburg (Germany)

    2015-04-07

    The one-dimensional charge density distribution along an electrically biased Fe atom probe needle is measured using a model-independent approach based on off-axis electron holography in the transmission electron microscope. Both the mean inner potential and the magnetic contribution to the phase shift are subtracted by taking differences between electron-optical phase images recorded with different voltages applied to the needle. The measured one-dimensional charge density distribution along the needle is compared with a similar result obtained using model-based fitting of the phase shift surrounding the needle. On the assumption of cylindrical symmetry, it is then used to infer the three-dimensional electric field and electrostatic potential around the needle with ∼10 nm spatial resolution, without needing to consider either the influence of the perturbed reference wave or the extension of the projected potential outside the field of view of the electron hologram. The present study illustrates how a model-independent approach can be used to measure local variations in charge density in a material using electron holography in the presence of additional contributions to the phase, such as those arising from changes in mean inner potential and specimen thickness.

  20. Nanostructural evolution of Cr-rich precipitates in a Cu-Cr-Zr alloy during heat treatment studied by 3 dimensional atom probe

    DEFF Research Database (Denmark)

    Hatakeyama, Masahiko; Toyama, Takeshi; Nagai, Yasuyoshi;

    2008-01-01

    Nanostructural evolution of Cr (Cr-rich) precipitates in a Cu-0.78%Cr-0.13%Zr alloy has been studied after aging and overaging (reaging) by laser assisted local electrode 3 dimensional atom probe (Laser-LEAP). This material is a candidate for the first wall and divertor components of future fusion...

  1. Topographic and electronic contrast of the graphene moir´e on Ir(111) probed by scanning tunneling microscopy and noncontact atomic force microscopy

    NARCIS (Netherlands)

    Sun, Z.; Hämäläinen, K.; Sainio, K.; Lahtinen, J.; Vanmaekelbergh, D.A.M.; Liljeroth, P.

    2011-01-01

    Epitaxial graphene grown on transition-metal surfaces typically exhibits a moir´e pattern due to the lattice mismatch between graphene and the underlying metal surface. We use both scanning tunneling microscopy (STM) and atomic force microscopy (AFM) to probe the electronic and topographic contrast

  2. In situ triaxial magnetic field compensation for the spin-exchange-relaxation-free atomic magnetometer.

    Science.gov (United States)

    Fang, Jiancheng; Qin, Jie

    2012-10-01

    The spin-exchange-relaxation-free (SERF) atomic magnetometer is an ultra-high sensitivity magnetometer, but it must be operated in a magnetic field with strength less than about 10 nT. Magnetic field compensation is an effective way to shield the magnetic field, and this paper demonstrates an in situ triaxial magnetic field compensation system for operating the SERF atomic magnetometer. The proposed hardware is based on optical pumping, which uses some part of the SERF atomic magnetometer itself, and the compensation method is implemented by analyzing the dynamics of the atomic spin. The experimental setup for this compensation system is described, and with this configuration, a residual magnetic field of strength less than 2 nT (±0.38 nT in the x axis, ±0.43 nT in the y axis, and ±1.62 nT in the z axis) has been achieved after compensation. The SERF atomic magnetometer was then used to verify that the residual triaxial magnetic fields were coincident with what were achieved by the compensation system.

  3. Scattering matrix theory for Cs Rydberg atoms in magnetic field

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Based on the closed orbit theory framework together with the quantum defect the-ory and time-independent scattering matrices theory,we calculate the recurrence spectra of diamagnetic Cs atoms at several different scaled energies near the second ionization threshold.It is revealed that the new extra peaks in spectra are attributed to the combination recurrences of semiclassical closed orbits arising from core-scattered events.This method considers the dynamic states of the Rydberg electron in the core region and long-range region and can be analytically resumed to include all orders of core-scattering automatically.With this approach a convergent recurrence spectrum can be reasonably achieved.It is found that the spectral complexity depends highly sensitively on the scaled energy.With the in-crease of the scaled energy,the spectral structure changes from simple to com-plicate and the dynamic feature from regular to chaotic.The comparison of the re-currence spectra with Dando’s result under the same conditions demonstrates that there exist some similarities and differences between them,and furthermore,the feasibility of the scattering matrix method is explained.

  4. 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.

  5. Schottky nanocontact of one-dimensional semiconductor nanostructures probed by using conductive atomic force microscopy

    Science.gov (United States)

    Lee, Jung Ah; Rok Lim, Young; Jung, Chan Su; Choi, Jun Hee; Im, Hyung Soon; Park, Kidong; Park, Jeunghee; Kim, Gyu Tae

    2016-10-01

    To develop the advanced electronic devices, the surface/interface of each component must be carefully considered. Here, we investigate the electrical properties of metal-semiconductor nanoscale junction using conductive atomic force microscopy (C-AFM). Single-crystalline CdS, CdSe, and ZnO one-dimensional nanostructures are synthesized via chemical vapor transport, and individual nanobelts (or nanowires) are used to fabricate nanojunction electrodes. The current-voltage (I -V) curves are obtained by placing a C-AFM metal (PtIr) tip as a movable contact on the nanobelt (or nanowire), and often exhibit a resistive switching behavior that is rationalized by the Schottky (high resistance state) and ohmic (low resistance state) contacts between the metal and semiconductor. We obtain the Schottky barrier height and the ideality factor through fitting analysis of the I-V curves. The present nanojunction devices exhibit a lower Schottky barrier height and a higher ideality factor than those of the bulk materials, which is consistent with the findings of previous works on nanostructures. It is shown that C-AFM is a powerful tool for characterization of the Schottky contact of conducting channels between semiconductor nanostructures and metal electrodes.

  6. Perfect/complete scattering experiments probing quantum mechanics on atomic and molecular collisions and coincidences

    CERN Document Server

    Kleinpoppen, Hans; Grum-Grzhimailo, Alexei N

    2013-01-01

    The main goal of this book is to elucidate what kind of experiment must be performed in order to determine the full set of independent parameters which can be extracted and calculated from theory, where electrons, photons, atoms, ions, molecules, or molecular ions may serve as the interacting constituents of matter.  The feasibility of such perfect' and-or `complete' experiments, providing the complete quantum mechanical knowledge of the process, is associated with the enormous potential of modern research techniques, both, in experiment and theory.  It is even difficult to overestimate the role of theory in setting of the complete experiment, starting with the fact that an experiment can be complete only within a certain theoretical framework, and ending with the direct prescription of what, and in what conditions should be measured to make the experiment `complete'.  The language of the related theory is the language of quantum mechanical amplitudes and their relative phases.  This book captures the spi...

  7. Sensitivity of self-powered detector probes to electron and gamma-ray fields

    Science.gov (United States)

    Lone, M. A.; Wong, P. Y.; Ajmani, K.

    1994-10-01

    A self-powered detector (SPD) is a simple, passive device that consists of a coaxial probe with a metallic outer sleeve, a mineral oxide insulating layer, and a metallic inner core. SPDs are used in nuclear reactors to monitor neutron and gamma fields. Responses of SPDs to electrons and γ-rays of various energies were investigated with Monte Carlo simulations. Transmission filters were studied for the design of threshold SPD probes used for on-line monitoring of the energy spectrum of high-power industrial electron accelerator beams. Filters were also investigated for the enhancement of γ-ray sensitivity of an SPD placed in a mixed electron and γ-ray field.

  8. Experimental demonstration of a fifth force due to chameleon field via cold atoms

    OpenAIRE

    Zhang, Hai-Chao

    2017-01-01

    We tested a fifth force using cold atom experiments. The accelerated expansion of the universe implies the possibility of the presence of a scalar field throughout the universe driving the acceleration. This field would result in a detectable force between normal-matter objects. Theory of the chameleon field states that the force should be strong in a thin shell near the surface of a source object but greatly suppressed inside and outside of the source object. We used two atom clouds: one as ...

  9. Magnetometer suitable for Earth field measurement based on transient atomic response

    CERN Document Server

    Lenci, L; Valente, P; Failache, H; Lezama, A

    2015-01-01

    We describe the development of a simple atomic magnetometer using $^{87}$Rb vapor suitable for Earth magnetic field monitoring. The magnetometer is based on time-domain determination of the transient precession frequency of the atomic alignment around the measured field. A sensitivity of 1.5 nT/$\\sqrt{Hz}$ is demonstrated on the measurement of the Earth magnetic field in the laboratory. We discuss the different parameters determining the magnetometer precision and accuracy and predict a sensitivity of 30 pT/$\\sqrt{Hz}$

  10. Probing the resonance potential in the F atom reaction with hydrogen deuteride with spectroscopic accuracy

    Science.gov (United States)

    Ren, Zefeng; Che, Li; Qiu, Minghui; Wang, Xingan; Dong, Wenrui; Dai, Dongxu; Wang, Xiuyan; Yang, Xueming; Sun, Zhigang; Fu, Bina; Lee, Soo-Y.; Xu, Xin; Zhang, Dong H.

    2008-01-01

    Reaction resonances are transiently trapped quantum states along the reaction coordinate in the transition state region of a chemical reaction that could have profound effects on the dynamics of the reaction. Obtaining an accurate reaction potential that holds these reaction resonance states and eventually modeling quantitatively the reaction resonance dynamics is still a great challenge. Up to now, the only viable way to obtain a resonance potential is through high-level ab initio calculations. Through highly accurate crossed-beam reactive scattering studies on isotope-substituted reactions, the accuracy of the resonance potential could be rigorously tested. Here we report a combined experimental and theoretical study on the resonance-mediated F + HD → HF + D reaction at the full quantum state resolved level, to probe the resonance potential in this benchmark system. The experimental result shows that isotope substitution has a dramatic effect on the resonance picture of this important system. Theoretical analyses suggest that the full-dimensional FH2 ground potential surface, which was believed to be accurate in describing the resonance picture of the F + H2 reaction, is found to be insufficiently accurate in predicting quantitatively the resonance picture for the F + HD → HF + D reaction. We constructed a global potential energy surface by using the CCSD(T) method that could predict the correct resonance peak positions as well as the dynamics for both F + H2 → HF + H and F + HD → HF + D, providing an accurate resonance potential for this benchmark system with spectroscopic accuracy. PMID:18687888

  11. Evaluation of electric field intensity on atom diffusion of Cu/Ta/Si stacks during annealing

    Energy Technology Data Exchange (ETDEWEB)

    Wang, L. [Jiangsu University of Science and Technology, Key Laboratory of Advanced Welding Technology of Jiangsu Province, Zhenjiang (China); Nanjing University, Stomatology Department, Nanjing General Hospital of Nanjing Command, Medical School, Nanjing (China); Jin, L. [Nanjing University, Stomatology Department, Nanjing General Hospital of Nanjing Command, Medical School, Nanjing (China); Yu, L.H.; Dong, S.T.; Chen, J.; Xu, J.H. [Jiangsu University of Science and Technology, Key Laboratory of Advanced Welding Technology of Jiangsu Province, Zhenjiang (China)

    2016-01-15

    Cu/Ta/Si stacks were prepared and, subsequently, annealed at 650 C with different electric field intensity (0-4.0 kV/cm). The effect of electric field intensity on atomic diffusion was determined from cross-sectional TEM micrographs of Cu/Ta/Si stacks. The atomic diffusion as well as the growth of amorphous layer at Ta/Si interface tended to enhance with the increased electric field intensity at 650 C. The growth of amorphous layer obeyed a logarithmic law. The reduction in diffusion activation energy Q by increased electric field intensity will accelerate the atom diffusion, leading to significant barrier failure of Cu/Ta/Si stacks. (orig.)

  12. Effect of Phase Shifted Frequency Modulation on Two Level Atom-Field Interaction

    Institute of Scientific and Technical Information of China (English)

    K.V. Priyesh; Ramesh Babu Thayyullathil

    2012-01-01

    We have studied the effect of phase shifted frequency modulation on two level atom with field interaction using Jaynes-Cummings model. Here the frequency of the interacting field is sinusoidally varying with time with a constant phase. Due to the presence of phase in the frequency modulation, the variation of population inversion with time is different from the standard case. There are no exact collapses and revivals in the variation of population inversion but it oscillates sinusoidally with time. In coherent field atom interaction the population inversion behaves as in the case of Fock state atom interaction, when frequency modulation with a non zero phase is applied. The study done with squeezed field has shown the same behavior of the population inversion.

  13. Dispersion of rotation of polarization plane and circular dichroism for alkaline atoms in intense radiation fields

    Science.gov (United States)

    Karagodova, Tamara Y.; Kuptsova, Anna V.

    1998-10-01

    The method of computer simulations on nonlinear resonant magneto-optical effects developed for real multi-level atoms in the two laser fields of arbitrary intensity and external magnetic field is applied for the polarization effects of different types calculations and investigations of the dependence of the characteristics of these effects on magnetic field strength, intensities, polarizations and detunings of laser fields for alkaline atoms. The essence of the method consists in simulations and analysis of the plots of dependence of quasienergies on parameters (detunings and intensities of radiation fields, magnetic field strength), which are obtained with the help of sorting subprogram, and selection of suitable algorithms for calculations of characteristics of nonlinear resonant magneto-optical effects. One-photon and two photon resonant effects are investigated for wide range of magnetic field strength from Zeeman to Paschen Back effects. Some new features in the spectra of rotation of plane of polarization and circular dicohroizm of different types are predicted. The results show the agreement with known experiments. Such calculations of nonlinear resonant magneto-optical effects in the intense laser fields resonant to adjacent transitions and magnetic field show the opportunity of investigation the modifications of electronic structure due to intense radiation fields and strong external magnetic field in atomic gases and also may be used for the treatment of new methods of phase-polarization selection of modes of tunable lasers.

  14. Probing the z > 6 universe with the first Hubble Frontier Fields cluster A2744.

    OpenAIRE

    Atek, Hakim,; Richard, Johan; Kneib, Jean-Paul; Clement, Benjamin; Egami, Eiichi; Ebeling, Harald; Jauzac, Mathilde; Jullo, Eric; Laporte, Nicolas; Limousin, Marceau; Natarajan, Priyamvada

    2014-01-01

    The Hubble Frontier Fields program combines the capabilities of the Hubble Space Telescope (HST) with the gravitational lensing of massive galaxy clusters to probe the distant universe to an unprecedented depth. Here, we present the results of the first combined HST and Spitzer observations of the cluster A-2744. We combine the full near-infrared data with ancillary optical images to search for gravitationally lensed high-redshift (z gsim 6) galaxies. We report the detection of 15 I 814 dropo...

  15. Ultrathin MXene-Micropattern-Based Field-Effect Transistor for Probing Neural Activity.

    Science.gov (United States)

    Xu, Bingzhe; Zhu, Minshen; Zhang, Wencong; Zhen, Xu; Pei, Zengxia; Xue, Qi; Zhi, Chunyi; Shi, Peng

    2016-05-01

    A field-effect transistor (FET) based on ultrathin Ti3 C2 -MXene micropatterns is developed and utilized as a highly sensitive biosensor. The device is produced with the microcontact printing technique, making use of its unique advantages for easy fabrication. Using the MXene-FET device, label-free probing of small molecules in typical biological environments and fast detection of action potentials in primary neurons is demonstrated.

  16. Magnetoencephalography with a two-color pump-probe, fiber-coupled atomic magnetometer

    Science.gov (United States)

    Johnson, Cort; Schwindt, Peter D. D.; Weisend, Michael

    2010-12-01

    The authors have detected magnetic fields from the human brain with a compact, fiber-coupled rubidium spin-exchange-relaxation-free magnetometer. Optical pumping is performed on the D1 transition and Faraday rotation is measured on the D2 transition. The beams share an optical axis, with dichroic optics preparing beam polarizations appropriately. A sensitivity of magnetoencephalography system. The design is amenable to arraying sensors around the head, providing a framework for noncryogenic, whole-head magnetoencephalography.

  17. Probing the interaction of individual amino acids with inorganic surfaces using atomic force spectroscopy.

    Science.gov (United States)

    Razvag, Yair; Gutkin, Vitaly; Reches, Meital

    2013-08-13

    This article describes single-molecule force spectroscopy measurements of the interaction between individual amino acid residues and inorganic surfaces in an aqueous solution. In each measurement, there is an amino acid residue, lysine, glutamate, phenylalanine, leucine, or glutamine, and each represents a class of amino acids (positively or negatively charged, aromatic, nonpolar, and polar). Force-distance curves measured the interaction of the individual amino acid bound to a silicon atomic force microscope (AFM) tip with a silcon substrate, cut from a single-crystal wafer, or mica. Using this method, we were able to measure low adhesion forces (below 300 pN) and could clearly determine the strength of interactions between the individual amino acid residues and the inorganic substrate. In addition, we observed how changes in the pH and ionic strength of the solution affected the adsorption of the residues to the substrates. Our results pinpoint the important role of hydrophobic interactions among the amino acids and the substrate, where hydrophobic phenylalanine exhibited the strongest adhesion to a silicon substrate. Additionally, electrostatic interactions also contributed to the adsorption of amino acid residues to inorganic substrates. A change in the pH or ionic strength values of the buffer altered the strength of interactions among the amino acids and the substrate. We concluded that the interplay between the hydrophobic forces and electrostatic interactions will determine the strength of adsorption among the amino acids and the surface. Overall, these results contribute to our understanding of the interaction at the organic-inorganic interface. These results may have implications for our perception of the specificity of peptide binding to inorganic surfaces. Consequently, it would possibly lead to a better design of composite materials and devices.

  18. Probing anisotropic surface properties and interaction forces of chrysotile rods by atomic force microscopy and rheology.

    Science.gov (United States)

    Yang, Dingzheng; Xie, Lei; Bobicki, Erin; Xu, Zhenghe; Liu, Qingxia; Zeng, Hongbo

    2014-09-16

    Understanding the surface properties and interactions of nonspherical particles is of both fundamental and practical importance in the rheology of complex fluids in various engineering applications. In this work, natural chrysotile, a phyllosilicate composed of 1:1 stacked silica and brucite layers which coil into cylindrical structure, was chosen as a model rod-shaped particle. The interactions of chrysotile brucite-like basal or bilayered edge planes and a silicon nitride tip were measured using an atomic force microscope (AFM). The force-distance profiles were fitted using the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, which demonstrates anisotropic and pH-dependent surface charge properties of brucite-like basal plane and bilayered edge surface. The points of zero charge (PZC) of the basal and edge planes were estimated to be around pH 10-11 and 6-7, respectively. Rheology measurements of 7 vol % chrysotile (with an aspect ratio of 14.5) in 10 mM NaCl solution showed pH-dependent yield stress with a local maximum around pH 7-9, which falls between the two PZC values of the edge and basal planes of the rod particles. On the basis of the surface potentials of the edge and basal planes obtained from AFM measurements, theoretical analysis of the surface interactions of edge-edge, basal-edge, and basal-basal planes of the chrysotile rods suggests the yield stress maximum observed could be mainly attributed to the basal-edge attractions. Our results indicate that the anisotropic surface properties (e.g., charges) of chrysotile rods play an important role in the particle-particle interaction and rheological behavior, which also provides insight into the basic understanding of the colloidal interactions and rheology of nonspherical particles.

  19. Evaluation of carbon nanotube probes in critical dimension atomic force microscopes.

    Science.gov (United States)

    Choi, Jinho; Park, Byong Chon; Ahn, Sang Jung; Kim, Dal-Hyun; Lyou, Joon; Dixson, Ronald G; Orji, Ndubuisi G; Fu, Joseph; Vorburger, Theodore V

    2016-07-01

    The decreasing size of semiconductor features and the increasing structural complexity of advanced devices have placed continuously greater demands on manufacturing metrology, arising both from the measurement challenges of smaller feature sizes and the growing requirement to characterize structures in more than just a single critical dimension. For scanning electron microscopy, this has resulted in increasing sophistication of imaging models. For critical dimension atomic force microscopes (CD-AFMs), this has resulted in the need for smaller and more complex tips. Carbon nanotube (CNT) tips have thus been the focus of much interest and effort by a number of researchers. However, there have been significant issues surrounding both the manufacture and use of CNT tips. Specifically, the growth or attachment of CNTs to AFM cantilevers has been a challenge to the fabrication of CNT tips, and the flexibility and resultant bending artifacts have presented challenges to using CNT tips. The Korea Research Institute for Standards and Science (KRISS) has invested considerable effort in the controlled fabrication of CNT tips and is collaborating with the National Institute of Standards and Technology on the application of CNT tips for CD-AFM. Progress by KRISS on the precise control of CNT orientation, length, and end modification, using manipulation and focused ion beam processes, has allowed us to implement ball-capped CNT tips and bent CNT tips for CD-AFM. Using two different generations of CD-AFM instruments, we have evaluated these tip types by imaging a line/space grating and a programmed line edge roughness specimen. We concluded that these CNTs are capable of scanning the profiles of these structures, including re-entrant sidewalls, but there remain important challenges to address. These challenges include tighter control of tip geometry and careful optimization of scan parameters and algorithms for using CNT tips.

  20. A genome probe survey of the microbial community in oil fields

    Energy Technology Data Exchange (ETDEWEB)

    Voordouw, G.; Telang, A. [Calgary Univ., AB (Canada). Dept. of Biology

    2000-07-01

    Reverse sample genome probing (RSGP) was conducted in water injected oil fields in Western Canada in order to analyze the microbial community in the fields to identify different bacteria responsible for microbially influenced corrosion (MIC) or souring. Oil fields of moderate temperature and salinity have an anaerobic microbial community consisting of sulfate-reducing bacteria (SRB), sulfide-oxidizing bacteria (SOB) and heterotrophic bacteria. The RSGP revealed that selected SRB are enhanced at metal surfaces and can therefore contribute to corrosion. Some of the SRB were found to be insensitive to biocides that are used in the field. RSGP also showed that injection of nitrate, instead of sulfate, leads to a marked increase of Campylobacter sp., which gets its energy from the oxidation of sulfide by nitrate. It was concluded that RSGP is a useful tool to monitor the effects of chemical stresses on the oil field microbial community. 13 refs., 2 figs.