Low-reflection beam refractions by ultrathin Huygens metasurface

International Nuclear Information System (INIS)

Jia, Sheng Li; Wan, Xiang; Fu, Xiao Jian; Zhao, Yong Jiu; Cui, Tie Jun

2015-01-01

We propose a Huygens source unit cell to develop an ultrathin low-reflection metasurface, which could provide extreme controls of phases of the transmitted waves. Both electric and magnetic currents are supported by the proposed unit cell, thus leading to highly efficient and full controls of phases. The coupling between electric and magnetic responses is negligible, which will significantly reduce the difficulty of design. Since the unit cell of metasurface is printed on two bonded boards, the fabrication process is simplified and the thickness of metasurface is reduced. Based on the proposed unit cell, a beam-refracting metasurface with low-reflection is designed and manufactured. Both near-field and far-field characteristics of the beam-refracting metasurface are investigated by simulations and measurements, which indicate that the proposed Huygens metasurface performs well in controlling electromagnetic waves

The effect of aberrated recording beams on reflecting Bragg gratings

Science.gov (United States)

SeGall, Marc; Ott, Daniel; Divliansky, Ivan; Glebov, Leonid B.

2013-03-01

The effect of aberrations present in the recording beams of a holographic setup is discussed regarding the period and spectral response of a reflecting volume Bragg grating. Imperfect recording beams result in spatially varying resonant wavelengths and the side lobes of the spectrum are washed out. Asymmetrical spectra, spectral broadening, and a reduction in peak diffraction efficiency may also be present, though these effects are less significant for gratings with wider spectral widths. Reflecting Bragg gratings (RBGs) are used as elements in a variety of applications including spectral beam combining1,2, mode locking3,4, longitudinal and transverse mode selection in lasers5,6, and sensing7,8. For applications requiring narrow spectral selectivity9, or large apertures10, these gratings must have a uniform period throughout the length of the recording medium, which may be on the order of millimeters. However, when using typical recording techniques such as two-beam interference for large aperture gratings and phase-mask recording of fiber gratings, aberrations from the optical elements in the system result in an imperfect grating structure11-13. In this paper we consider the effects of aberrations on large aperture gratings recorded in thick media using the two-beam interference technique. Previous works in analyzing the effects of aberrations have considered the effects of aberrations in a single recording plane where the beams perfectly overlap. Such an approach is valid for thin media (on the order of tens of microns), but for thick recording media (on the order of several millimeters) there will be a significant shift in the positions of the beams relative to each other as they traverse the recording medium. Therefore, the fringe pattern produced will not be constant throughout the grating if one or both beams have a non-uniform wavefront. Such non-uniform gratings may have a wider spectral width, a shifted resonant wavelength, or other problems. It is

Ion Dynamics at Shocks: Ion Reflection and Beam Formation at Quasi-perpendicular Shocks

International Nuclear Information System (INIS)

Kucharek, Harald; Moebius, Eberhard

2005-01-01

The physics of collisionless shocks is controlled by the ion dynamics. The generation of gyrating ions by reflection as well as the formation of field-aligned ion beams are essential parts of this dynamic. On the one hand reflection is most likely the first interaction of ions with the shock before they undergo the downstream thermalization process. On the other hand field-aligned ion beams, predominately found at the quasi-perpendicular bow shock, propagate into the distant foreshock region and may create wave activity. We revisit ion reflection, the source and basic production mechanism of field-aligned ion beams, by using multi-spacecraft measurements and contrast these observations with existing theories. Finally, we propose an alternative production mechanism

Beam line optics technologies series (7). Orthopedic treatment of sharp of light (reflecting mirror)

International Nuclear Information System (INIS)

Uruga, Tomoya; Nomura, Masaharu

2006-01-01

A reflecting mirror (mirror) is the most popular light device for orthopedic treatment of the shape of light. The paper explains the kinds of mirror for hard X-ray field and its applications in order to think the objects of mirror and how to adjust it when user experiment on the beam-line. The basic knowledge of reflection of X-ray, a use of mirror, the kinds of condenser mirror, the influence factors on the condenser size, arrangement of mirror in the hard X-ray beam-line, what kinds of mirror are necessary, evaluation of performance of mirror and adjustment, and troubles and measures are described. Layout in optics hutch at BL01B1 at SPring-8, refraction and total reflection of X-rays at surface, reflectivity of Rh and Pt with ideal surface as a function of photon energy, effects of surface roughness on reflectivity of Rh, calculated beam sizes for typical SPring-8 mirror as a function of magnification, schematic drawing of mirror, standard mirror system for vertical deflection in bending magnet beam-line, and observed and calculated reflectivity of Rh double mirror at BL01B1 at SPring-8 are illustrated. (S.Y)

Beams of fast neutral atoms and molecules in low-pressure gas-discharge plasma

Energy Technology Data Exchange (ETDEWEB)

Metel, A. S., E-mail: ametel@stankin.ru [Moscow State University of Technology ' Stankin,' (Russian Federation)

2012-03-15

Fast neutral atom and molecule beams have been studied, the beams being produced in a vacuum chamber at nitrogen, argon, or helium pressure of 0.1-10 Pa due to charge-exchange collisions of ions accelerated in the sheath between the glow discharge plasma and a negative grid immersed therein. From a flat grid, two broad beams of molecules with continuous distribution of their energy from zero up to e(U + U{sub c}) (where U is voltage between the grid and the vacuum chamber and U{sub c} is cathode fall of the discharge) are propagating in opposite directions. The beam propagating from the concave surface of a 0.2-m-diameter grid is focused within a 10-mm-diameter spot on the target surface. When a 0.2-m-diameter 0.2-m-high cylindrical grid covered by end disks and composed of parallel 1.5-mm-diameter knitting needles spaced by 4.5 mm is immersed in the plasma, the accelerated ions pass through the gaps between the needles, turn inside the grid into fast atoms or molecules, and escape from the grid through the gaps on its opposite side. The Doppler shift of spectral lines allows for measuring the fast atom energy, which corresponds to the potential difference between the plasma inside the chamber and the plasma produced as a result of charge-exchange collisions inside the cylindrical grid.

Matrix isolation sublimation: An apparatus for producing cryogenic beams of atoms and molecules

Energy Technology Data Exchange (ETDEWEB)

Sacramento, R. L.; Alves, B. X.; Silva, B. A.; Wolff, W.; Cesar, C. L. [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ (Brazil); Oliveira, A. N. [Instituto de Física, Universidade Federal do Rio de Janeiro, Caixa Postal 68528, 21941-972 Rio de Janeiro, RJ (Brazil); INMETRO, Av. Nossa Senhora das Graças, 50 25250-020 Duque de Caxias, RJ (Brazil); Li, M. S. [Instituto de Física de São Carlos, Universidade de São Paulo, Ave. Trabalhador São Carlense, 400, 13565-590 São Carlos, SP (Brazil)

2015-07-15

We describe the apparatus to generate cryogenic beams of atoms and molecules based on matrix isolation sublimation. Isolation matrices of Ne and H{sub 2} are hosts for atomic and molecular species which are sublimated into vacuum at cryogenic temperatures. The resulting cryogenic beams are used for high-resolution laser spectroscopy. The technique also aims at loading atomic and molecular traps.

Experimental Investigation of Propagation and Reflection Phenomena in Finite Amplitude Sound Beams.

Science.gov (United States)

Averkiou, Michalakis Andrea

Measurements of finite amplitude sound beams are compared with theoretical predictions based on the KZK equation. Attention is devoted to harmonic generation and shock formation related to a variety of propagation and reflection phenomena. Both focused and unfocused piston sources were used in the experiments. The nominal source parameters are piston radii of 6-25 mm, frequencies of 1-5 MHz, and focal lengths of 10-20 cm. The research may be divided into two parts: propagation and reflection of continuous-wave focused sound beams, and propagation of pulsed sound beams. In the first part, measurements of propagation curves and beam patterns of focused pistons in water, both in the free field and following reflection from curved targets, are presented. The measurements are compared with predictions from a computer model that solves the KZK equation in the frequency domain. A novel method for using focused beams to measure target curvature is developed. In the second part, measurements of pulsed sound beams from plane pistons in both water and glycerin are presented. Very short pulses (less than 2 cycles), tone bursts (5-30 cycles), and frequency modulated (FM) pulses (10-30 cycles) were measured. Acoustic saturation of pulse propagation in water is investigated. Self-demodulation of tone bursts and FM pulses was measured in glycerin, both in the near and far fields, on and off axis. All pulse measurements are compared with numerical results from a computer code that solves the KZK equation in the time domain. A quasilinear analytical solution for the entire axial field of a self-demodulating pulse is derived in the limit of strong absorption. Taken as a whole, the measurements provide a broad data base for sound beams of finite amplitude. Overall, outstanding agreement is obtained between theory and experiment.

High-efficiency dual-modes vortex beam generator with polarization-dependent transmission and reflection properties.

Science.gov (United States)

Tang, Shiwei; Cai, Tong; Wang, Guang-Ming; Liang, Jian-Gang; Li, Xike; Yu, Jiancheng

2018-04-23

Vortex beam is believed to be an effective way to extend communication capacity, but available efforts suffer from the issues of complex configurations, fixed operation mode as well as low efficiency. Here, we propose a general strategy to design dual-modes vortex beam generator by using metasurfaces with polarization-dependent transmission and reflection properties. Combining the focusing and vortex functionalities, we design/fabricate a type of compact dual-modes vortex beam generator operating at both reflection/transmission sides of the system. Experimental results demonstrate that the designed metadevice can switch freely and independently between the reflective vortex with topological charge m 1  = 2 and transmissive vortex with m 2  = 1. Moreover, the metadevice exhibits very high efficiencies of 91% and 85% for the reflective and transmissive case respectively. Our findings open a door for multifunctional metadevices with high performances, which indicate wide applications in modern integration-optics and wireless communication systems.

Channeling and Volume Reflection Based Crystal Collimation of Tevatron Circulating Beam Halo

CERN Document Server

Shiltsev, V.; Drozhdin, A.; Johnson, T.; Legan, A.; Mokhov, N.; Reilly, R.; Still, D.; Tesarek, R.; Zagel, J.; Peggs, S.; Assmann, R.; Previtali, V.; Scandale, W.; Chesnokov, Y.; Yazynin, I.; Guidi, V.; Ivanov, Y.

2010-01-01

The T980 crystal collimation experiment is underway at the Tevatron to determine if this technique could increase 980 GeV beam-halo collimation efficiency at high-energy hadron colliders such as the Tevatron and the LHC. T980 also studies various crystal types and parameters. The setup has been substantially enhanced during the Summer 2009 shutdown by installing a new O-shaped crystal in the horizontal goniometer, as well as adding a vertical goniometer with two alternating crystals (O-shaped and multi-strip) and additional beam diagnostics. First measurements with the new system are quite encouraging, with channeled and volume-reflected beams observed on the secondary collimators as predicted. Investigation of crystal collimation efficiencies with crystals in volume reflection and channeling modes are described in comparison with an amorphous primary collimator. Results on the system performance are presented for the end-of-store studies and for entire collider stores. The first investigation of colliding be...

A study of small molecule ingress into planar and cylindrical materials using ion beam analysis

International Nuclear Information System (INIS)

Smith, R.W.

2001-12-01

Ion beam analysis techniques have been developed to allow profiling of small molecules diffused into materials at depths ranging from 10 -7 to 10 -1 m. A model DPS/PS/DPS triple-layer film and D( 3 He,p) 4 He nuclear reaction analysis was used to test the applicability of a novel data processing program - the IBA DataFurnace - to nuclear reaction data. The same reaction and program were used to depth profile the diffusion of heavy water into cellophane. A scanning 3 He micro-beam technique was developed to profile the diffusion of small molecules into both planar and cylindrical materials. The materials were exposed to liquids containing deuterium labelled molecules. A cross-section was exposed by cutting the material perpendicular to the surface and this was bombarded by a scanning 3 He micro-beam. Nuclear reaction analysis was used to profile the diffusing molecules, particle induced X-ray emission (in most cases) to locate the matrix and Rutherford backscattering for normalisation. Two-dimensional maps showing the molecular distribution over the cross-section were obtained. From these one-dimensional concentration profiles were produced. Water diffusion was studied into a planar and a cylindrical polymer, three different planar fibre optic grade glasses and both a fibre optic pressure sensor and communication fibre. The diffusion of dye into hair was also investigated. These studies have provided information about the diffusion mechanisms that take place, and where relevant diffusion coefficients have been obtained using either a semi-infinite medium Fickian planar diffusion model or a cylindrical Fickian diffusion model. (author)

Dynamics and adsorption of gas molecules using proton beams

International Nuclear Information System (INIS)

Kim, J. Y.; Kim, E. K.; Lee, J. K.

2008-04-01

We irradiated nano sized MgO powders and carbon nanotubes by proton beams with energy of 35 MeV for different dosing time and the difference before and after the irradiation was investigated by using NO and Ar gas adsorptions studies. Particular interest was given to the irradiation of proton beams on quasicrystals made with Ti-Zr-Ni to remove the oxygen layer on the surface of the sample. Quasicrystals are known to exhibit a 5-fold rotational symmetry which is theoretically forbidden in a concept of solid state physics, and have a potential applications on large amount of hydrogen loading due to their structural complexity and chemical affinity with hydrogen. The results are summarized as four major accomplishments. 1) Proton irradiated MgO powders demonstrated the increased number of NO atomic layers in a layer-by-layer fashion suggesting that the surface of the sample became homogeneous compare to the pure samples. 2) the synchrotron based X-ray diffraction data suggests that NO molecules form an 1x1 commensurate structure on MgO (100) surface evidenced by the NO peak location at the Q values of 2.12 A -1 . 3) Proton irradiated SWCNTs exhibit the uniform Ar atomic layer formation suggesting that the surface of the CNTs can be homonized by the proton beam irradiation, and 4) 20 MeV of proton beam can effectively remove the oxygen layer on metal oxides so that Ti-Zr-Ni quasicrystals can load a large amount of hydrogen (exceeding to the density of liquid hydrogen) at room temperature.

Single-Molecule Fluorescence Studies of Membrane Transporters Using Total Internal Reflection Microscopy.

Science.gov (United States)

Goudsmits, Joris M H; van Oijen, Antoine M; Slotboom, Dirk J

2017-01-01

Cells are delineated by a lipid bilayer that physically separates the inside from the outer environment. Most polar, charged, or large molecules require proteins to reduce the energetic barrier for passage across the membrane and to achieve transport rates that are relevant for life. Here, we describe techniques to visualize the functioning of membrane transport proteins with fluorescent probes at the single-molecule level. First, we explain how to produce membrane-reconstituted transporters with fluorescent labels. Next, we detail the construction of a microfluidic flow cell to image immobilized proteoliposomes on a total internal reflection fluorescence microscope. We conclude by describing the methods that are needed to analyze fluorescence movies and obtain useful single-molecule data. © 2017 Elsevier Inc. All rights reserved.

Reflection coefficients of permeant molecules in human red cell suspensions.

Science.gov (United States)

Owen, J D; Eyring, E M

1975-08-01

The Staverman reflection coefficient, sigma for several permeant molecules was determined in human red cell suspensions with a Durrum stopped-flow spectrophotometer. This procedure was first used with dog, cat, and beef red cells and with human red cells. The stopped-flow technique used was similar to the rapid-flow method used by those who originally reported sigma measurements in human red cells for molecules which rapidly penetrate the red cell membrane. The sigma values we obtained agreed with those previously reported for most of the slow penetrants, except malonamide, but disagreed with all the sigma values previously reported for the rapid penetrants. We were unable to calculate an "equivalent pore radius" with our sigma data. The advantages of our equipment and our experimental procedure are discussed. Our sigma data suggest that sigma is indirectly proportional to the log of the nonelectrolyte permeability coefficient, omega. Since a similar trend has been previously shown for log omega and molar volume of the permeant molecules, a correlatioo was shown between sigma and molar volume suggesting the membrane acts as a sieve.

A positronium beam and positronium reflection from LiF(100)

International Nuclear Information System (INIS)

Weber, M.; Tang, S.; Berko, S.; Brown, B.L.; Canter, K.F.; Lynn, K.G.; Mills, A.P. Jr.; Roellig, L.O.; Viescas, A.J.

1988-01-01

We report results obtained from a variable energy monoenergetic beam of positronium (Ps). Ps was formed by a charge transfer reaction of positrons colliding with Ar gas atoms in a ''gas cell'' with an efficiency of about 3 /times/ 10/sup /minus/4/. The beam was used to measure the fraction, R, of specularly reflected ortho-Ps from LiF(100). We found R to peak at about 30% for 7 eV Ps at a specular scattering angle of 50/degree/ to 60/degree/. At higher energies R drops sharply to values around 0.5% near 60 eV Ps

Ghost reflections of Gaussian beams in anamorphic optical systems with an application to Michelson interferometer.

Science.gov (United States)

Abd El-Maksoud, Rania H

2016-02-20

In this paper, a methodology is developed to model and analyze the effect of undesired (ghost) reflections of Gaussian beams that are produced by anamorphic optical systems. The superposition of these beams with the nominal beam modulates the nominal power distribution at the recording plane. This modulation may cause contrast reduction, veiling parts of the nominal image, and/or the formation of spurious interference fringes. The developed methodology is based on synthesizing the beam optical paths into nominal and ghost optical beam paths. Similar to the nominal beam, we present the concept that each ghost beam is characterized by a beam size, wavefront radius of curvature, and Gouy phase in the paraxial regime. The nominal and ghost beams are sequentially traced through the system and formulas for estimating the electric field magnitude and phase of each ghost beam at the recording plane are presented. The effective electric field is the addition of the individual nominal and ghost electric fields. Formulas for estimating Gouy phase, the shape of the interference fringes, and the central interference order are introduced. As an application, the theory of the formation of the interference fringes by Michelson interferometer is presented. This theory takes into consideration the ghost reflections that are formed by the beam splitter. To illustrate the theory and to show its wide applicability, simulation examples that include a Mangin mirror, a Michelson interferometer, and a black box optical system are provided.

Laser mass spectrometry with circularly polarized light: circular dichroism of cold molecules in a supersonic gas beam.

Science.gov (United States)

Titze, Katharina; Zollitsch, Tilo; Heiz, Ulrich; Boesl, Ulrich

2014-09-15

An experiment on chiral molecules that combines circular dichroism (CD) spectroscopy, mass-selective detection by laser mass spectrometry (MS), and cooling of molecules by using a supersonic beam is presented. The combination of the former two techniques (CD-laser-MS) is a new method to investigate chiral molecules and is now used by several research groups. Cooling in a supersonic beam supplies a substantial increase in spectroscopic resolution, a feature that has not yet been used in CD spectroscopy. In the experiments reported herein, a large variation in the electronic CD of carbonyl 3-methylcyclopentanone was observed depending on the excited vibrational modes in the n → π* transition. This finding should be of interest for the detection of chiral molecules and for the theoretical understanding of the CD of vibronic bands. It is expected that this effect will show up in other chiral carbonyls because the n → π* transition is typical for the carbonyl group. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Specific Features of Destabilization of the Wave Profile During Reflection of an Intense Acoustic Beam from a Soft Boundary

Science.gov (United States)

Deryabin, M. S.; Kasyanov, D. A.; Kurin, V. V.; Garasyov, M. A.

2016-05-01

We show that a significant energy redistribution occurs in the spectrum of reflected nonlinear waves, when an intense acoustic beam is reflected from an acoustically soft boundary, which manifests itself at short wave distances from a reflecting boundary. This effect leads to the appearance of extrema in the distributions of the amplitude and intensity of the field of the reflected acoustic beam near the reflecting boundary. The results of physical experiments are confirmed by numerical modeling of the process of transformation of nonlinear waves reflected from an acoustically soft boundary. Numerical modeling was performed by means of the Khokhlov—Zabolotskaya—Kuznetsov (KZK) equation.

Versatile piezoelectric pulsed molecular beam source for gaseous compounds and organic molecules with femtomole accuracy for UHV and surface science applications

International Nuclear Information System (INIS)

Schiesser, Alexander; Schaefer, Rolf

2009-01-01

This note describes the construction of a piezoelectric pulsed molecular beam source based upon a design presented in an earlier work [D. Proch and T. Trickl, Rev. Sci. Instrum. 60, 713 (1988)]. The design features significant modifications that permit the determination of the number of molecules in a beam pulse with an accuracy of 1x10 11 molecules per pulse. The 21 cm long plunger-nozzle setup allows the molecules to be brought to any point of the UHV chamber with very high intensity. Furthermore, besides typical gaseous compounds, also smaller organic molecules with a vapor pressure higher than 0.1 mbar at room temperature may serve as feed material. This makes the new design suitable for various applications in chemical and surface science studies.

Site-specific fragmentation of polystyrene molecule using size-selected Ar gas cluster ion beam

International Nuclear Information System (INIS)

Moritani, Kousuke; Mukai, Gen; Hashinokuchi, Michihiro; Mochiji, Kozo

2009-01-01

The secondary ion mass spectrum (SIMS) of a polystyrene thin film was investigated using a size-selected Ar gas cluster ion beam (GCIB). The fragmentation in the SIM spectrum varied by kinetic energy per atom (E atom ); the E atom dependence of the secondary ion intensity of the fragment species of polystyrene can be essentially classified into three types based on the relationship between E atom and the dissociation energy of a specific bonding site in the molecule. These results indicate that adjusting E atom of size-selected GCIB may realize site-specific bond breaking within a molecule. (author)

High-Efficiency Volume Reflection of an Ultrarelativistic Proton Beam with a Bent Silicon Crystal

CERN Document Server

Scandale, Walter; Carnera, Alberto; Della Mea, Gianantonio; De Salvador, Davide; Milan, Riccardo; Vomiero, Alberto; Baricordi, Stefano; Dalpiaz, Pietro; Fiorini, Massimiliano; Guidi, Vincenzo; Martinelli,Giuliano; Mazzolari, Andrea; Milan, Emiliano; Ambrosi, Giovanni; Azzarello, Philipp; Battiston, Roberto; Bertucci, Bruna; Burger, William J; Ionica, Maria; Zuccon, Paolo; Cavoto, Gianluca; Santacesaria, Roberta; Valente, Paolo; Vallazza, Erik; Afonin, Alexander G; Baranov, Vladimir T; Chesnokov, Yury A; Kotov, Vladilen I; Maisheev, Vladimir A; Yaznin, Igor A; Afansiev, Sergey V; Kovalenko, Alexander D; Taratin, Alexander M; Denisov, Alexander S; Gavrikov, Yury A; Ivanov, Yuri M; Ivochkin, Vladimir G; Kosyanenko, Sergey V; Petrunin, Anatoli A; Skorobogatov, Vyacheslav V; Suvorov, Vsevolod M; Bolognini, Davide; Foggetta,Luca; Hasan, Said; Prest, Michela

2007-01-01

The volume reflection phenomenon was detected while investigating 400 GeV proton interactions with bent silicon crystals in the external beam H8 of the CERN Super Proton Synchrotron. Such a process was observed for a wide interval of crystal orientations relative to the beam axis, and its efficiency exceeds 95%, thereby surpassing any previously observed value. These observations suggest new perspectives for the manipulation of high-energy beams, e.g., for collimation and extraction in new-generation hadron colliders, such as the CERN Large Hadron Collider.

Generating millimeter-wave Bessel beam with orbital angular momentum using reflective-type metasurface inherently integrated with source

Science.gov (United States)

Shen, Yizhu; Yang, Jiawei; Meng, Hongfu; Dou, Wenbin; Hu, Sanming

2018-04-01

Metasurfaces, orbital angular momenta (OAM), and non-diffractive Bessel beams have been attracting worldwide research. Combining the benefits of these three promising techniques, this paper proposes a metasurface-based reflective-type approach to generate a first-order Bessel beam carrying OAM. To validate this approach, a millimeter-wave metasurface is analyzed, designed, fabricated, and measured. Experimental results agree well with simulation. Moreover, this reflective-type metasurface, generating a Bessel beam with OAM, is inherently integrated with a planar feeding source in the same single-layer printed circuit board. Therefore, the proposed design features low profile, low cost, easy integration with front-end active circuits, and no alignment error between the feeding source and the metasurface.

Transient field behavior in an electromagnetic pulse from neutral-beam reflection

International Nuclear Information System (INIS)

Strobel, G.L.

1990-01-01

A neutral beam of electrons and positrons catches up to an electromagnetic pulse moving in a medium with refractive index n. The neutral beam is reflected and deposits some of its energy in a current region in the tail of the pulse. The location, size, and shape of the transient-induced electric fields in the current region are modeled using current densities from uniform averaged fields. The electric field in the current region is predicted to rise linearly with time, with a doubling time determined by the beam parameters and the initial local electromagnetic field. A coordinate frame comoving with the pulse is used to determine the extent of and conditions within the current region. In this comoving frame the Lorentz-transformed electric field is zero, but there is an enhanced Lorentz-transformed magnetic field. The extent of the current region is found from the radius of the semicircular charged-particle orbits in the comoving frame

Dielectric multilayer beam splitter with differential phase shift on transmission and reflection for division-of-amplitude photopolarimeter.

Science.gov (United States)

Yuan, Wenjia; Shen, Weidong; Zhang, Yueguang; Liu, Xu

2014-05-05

Dielectric multilayer beam splitter with differential phase shift on transmission and reflection for division-of-amplitude photopolarimeter (DOAP) was presented for the first time to our knowledge. The optimal parameters for the beam splitter are Tp = 78.9%, Ts = 21.1% and Δr - Δt = π/2 at 532nm at an angle of incidence of 45°. Multilayer anti-reflection coating with low phase shift was applied to reduce the backside reflection. Different design strategies that can achieve all optimal targets at the wavelength were tested. Two design methods were presented to optimize the differential phase shift. The samples were prepared by ion beam sputtering (IBS). The experimental results show good agreement with those of the design. The ellipsometric parameters of samples were measured in reflection (ψr, Δr) = (26.5°, 135.1°) and (28.2°, 133.5°), as well as in transmission (ψt, Δt) = (62.5°, 46.1°) and (63.5°, 46°) at 532.6nm. The normalized determinant of instrument matrix to evaluate the performance of samples is respectively 0.998 and 0.991 at 532.6nm.

Measuring contact angle and meniscus shape with a reflected laser beam.

Science.gov (United States)

Eibach, T F; Fell, D; Nguyen, H; Butt, H J; Auernhammer, G K

2014-01-01

Side-view imaging of the contact angle between an extended planar solid surface and a liquid is problematic. Even when aligning the view perfectly parallel to the contact line, focusing one point of the contact line is not possible. We describe a new measurement technique for determining contact angles with the reflection of a widened laser sheet on a moving contact line. We verified this new technique measuring the contact angle on a cylinder, rotating partially immersed in a liquid. A laser sheet is inclined under an angle φ to the unperturbed liquid surface and is reflected off the meniscus. Collected on a screen, the reflection image contains information to determine the contact angle. When dividing the laser sheet into an array of laser rays by placing a mesh into the beam path, the shape of the meniscus can be reconstructed from the reflection image. We verified the method by measuring the receding contact angle versus speed for aqueous cetyltrimethyl ammonium bromide solutions on a smooth hydrophobized as well as on a rough polystyrene surface.

Nonpolarizing beam splitter designed by frustrated total internal reflection inside a glass cube.

Science.gov (United States)

Xu, Xueke; Shao, Jianda; Fan, Zhengxiu

2006-06-20

A method for the design of an all-dielectric nonpolarizing prism beam splitter utilizing the principle of frustrated total internal reflection is reported. The nonpolarizing condition for a prism beam splitter is discussed, and some single layer design examples are elaborated. The concept can be applied to a wide range of wavelengths and arbitrary transmittance values, and with the help of a computer design program examples of 400-700 nm, T(p)=T(s)=0.5+/-0.01, with incident angles of 45 degrees and 62 degrees are given. In addition, the sensitivity and application of the design are also discussed.

Spectral multitude and spectral dynamics reflect changing conjugation length in single molecules of oligophenylenevinylenes

KAUST Repository

Kobayashi, Hiroyuki; Tsuchiya, Kousuke; Ogino, Kenji; Vacha, Martin

2012-01-01

Single-molecule study of phenylenevinylene oligomers revealed distinct spectral forms due to different conjugation lengths which are determined by torsional defects. Large spectral jumps between different spectral forms were ascribed to torsional flips of a single phenylene ring. These spectral changes reflect the dynamic nature of electron delocalization in oligophenylenevinylenes and enable estimation of the phenylene torsional barriers. © 2012 The Owner Societies.

Interaction of a finite-length ion beam with a background plasma: Reflected ions at the quasi-parallel bow shock

International Nuclear Information System (INIS)

Onsager, T.G.; Winske, D.; Thomsen, M.F.

1991-01-01

The coupling of a finite-length, field-aligned, ion beam with a uniform background plasma is investigated using one-dimensional hybrid computer simulations. The finite-length beam is used to study the interaction between the incident solar wind and ions reflected from the Earth's quasi-parallel bow shock, where the reflection process may vary with time. The coupling between the reflected ions and the solar wind is relevant to ion heating at the bow shock and possibly to the formation of hot, flow anomalies and re-formation of the shock itself. The authors find that although there are many similarities between the instabilities driven by the finite-length beam and those predicted by linear theory for an infinite, homogeneous beam, there are also some important differences. Consistent with linear theory, the waves which dominate the interaction are the electromagnetic right-hand polarized resonant and nonresonant modes. However, in addition to the instability growth rates, the length of time that the waves are in contact with the beam is also an important factor in determining which wave mode will dominate the interaction. Whereas linear theory predicts the nonresonant mode to have the larger growth rate for the parameters they investigate, with finite-length beam they find that both the nonresonant and resonant modes contribute to the interaction. They find that the interaction will result in strong coupling, where a significant fraction of the available free energy is converted into thermal energy in a short time, provided the beam is sufficiently dense or sufficiently long

Ion-Molecule Reaction Dynamics.

Science.gov (United States)

Meyer, Jennifer; Wester, Roland

2017-05-05

We review the recent advances in the investigation of the dynamics of ion-molecule reactions. During the past decade, the combination of single-collision experiments in crossed ion and neutral beams with the velocity map ion imaging detection technique has enabled a wealth of studies on ion-molecule reactions. These methods, in combination with chemical dynamics simulations, have uncovered new and unexpected reaction mechanisms, such as the roundabout mechanism and the subtle influence of the leaving group in anion-molecule nucleophilic substitution reactions. For this important class of reactions, as well as for many fundamental cation-molecule reactions, the information obtained with crossed-beam imaging is discussed. The first steps toward understanding micro-solvation of ion-molecule reaction dynamics are presented. We conclude with the presentation of several interesting directions for future research.

Collision dynamics of methyl radicals and highly vibrationally excited molecules using crossed molecular beams

International Nuclear Information System (INIS)

Chu, P.M.Y.

1991-10-01

The vibrational to translational (V→T) energy transfer in collisions between large highly vibrationally excited polyatomics and rare gases was investigated by time-of-flight techniques. Two different methods, UV excitation followed by intemal conversion and infrared multiphoton excitation (IRMPE), were used to form vibrationally excited molecular beams of hexafluorobenzene and sulfur hexafluoride, respectively. The product translational energy was found to be independent of the vibrational excitation. These results indicate that the probability distribution function for V→T energy transfer is peaked at zero. The collisional relaxation of large polyatomic molecules with rare gases most likely occurs through a rotationally mediated process. Photodissociation of nitrobenzene in a molecular beam was studied at 266 nm. Two primary dissociation channels were identified including simple bond rupture to produce nitrogen dioxide and phenyl radical and isomerization to form nitric oxide and phenoxy radical. The time-of-flight spectra indicate that simple bond rupture and isomerization occurs via two different mechanisms. Secondary dissociation of the phenoxy radicals to carbon monoxide and cyclopentadienyl radicals was observed as well as secondary photodissociation of phenyl radical to give H atom and benzyne. A supersonic methyl radical beam source is developed. The beam source configuration and conditions were optimized for CH 3 production from the thermal decomposition of azomethane. Elastic scattering of methyl radical and neon was used to differentiate between the methyl radicals and the residual azomethane in the molecular beam

Total internal reflection sum-frequency generation spectroscopy and dense gold nanoparticles monolayer: a route for probing adsorbed molecules

International Nuclear Information System (INIS)

Tourillon, Gerard; Dreesen, Laurent; Volcke, Cedric; Sartenaer, Yannick; Thiry, Paul A; Peremans, Andre

2007-01-01

We show that sum-frequency generation spectroscopy performed in the total internal reflection configuration (TIR-SFG) combined with a dense gold nanoparticles monolayer allows us to study, with an excellent signal to noise ratio and high signal to background ratio, the conformation of adsorbed molecules. Dodecanethiol (DDT) was used as probe molecules in order to assess the potentialities of the approach. An enhancement of more than one order of magnitude of the SFG signals arising from the adsorbed species is observed with the TIR geometry compared to the external reflection one while the SFG non-resonant contribution remains the same for both configurations. Although further work is required to fully understand the origin of the SFG process on nanoparticles, our work opens new possibilities for studying nanostructures

BEAM TRANSPORT AND STORAGE WITH COLD NEUTRAL ATOMS AND MOLECULES

Energy Technology Data Exchange (ETDEWEB)

Walstrom, Peter L. [Los Alamos National Laboratory

2012-05-15

A large class of cold neutral atoms and molecules is subject to magnetic field-gradient forces. In the presence of a field, hyperfine atomic states are split into several Zeeman levels. The slopes of these curves vs. field are the effective magnetic moments. By means of optical pumping in a field, Zeeman states of neutral lithium atoms and CaH molecules with effective magnetic moments of nearly {+-} one Bohr magneton can be selected. Particles in Zeeman states for which the energy increases with field are repelled by increasing fields; particles in states for which the energy decreases with field are attracted to increasing fields. For stable magnetic confinement, field-repelled states are required. Neutral-particle velocities in the present study are on the order of tens to hundreds of m/s and the magnetic fields needed for transport and injection are on the order of in the range of 0.01-1T. Many of the general concepts of charged-particle beam transport carry over into neutral particle spin-force optics, but with important differences. In general, the role of bending dipoles in charged particle optics is played by quadrupoles in neutral particle optics; the role of quadrupoles is played by sextupoles. The neutralparticle analog of charge-exchange injection into storage rings is the use of lasers to flip the state of particles from field-seeking to field-repelled. Preliminary tracking results for two neutral atom/molecule storage ring configurations are presented. It was found that orbit instabilities limit the confinment time in a racetrack-shaped ring with discrete magnetic elements with drift spaces between them; stable behavior was observed in a toroidal ring with a continuous sextupole field. An alternative concept using a linear sextupole or octupole channel with solenoids on the ends is presently being considered.

Quantifying the Assembly of Multicomponent Molecular Machines by Single-Molecule Total Internal Reflection Fluorescence Microscopy.

Science.gov (United States)

Boehm, E M; Subramanyam, S; Ghoneim, M; Washington, M Todd; Spies, M

2016-01-01

Large, dynamic macromolecular complexes play essential roles in many cellular processes. Knowing how the components of these complexes associate with one another and undergo structural rearrangements is critical to understanding how they function. Single-molecule total internal reflection fluorescence (TIRF) microscopy is a powerful approach for addressing these fundamental issues. In this article, we first discuss single-molecule TIRF microscopes and strategies to immobilize and fluorescently label macromolecules. We then review the use of single-molecule TIRF microscopy to study the formation of binary macromolecular complexes using one-color imaging and inhibitors. We conclude with a discussion of the use of TIRF microscopy to examine the formation of higher-order (i.e., ternary) complexes using multicolor setups. The focus throughout this article is on experimental design, controls, data acquisition, and data analysis. We hope that single-molecule TIRF microscopy, which has largely been the province of specialists, will soon become as common in the tool box of biophysicists and biochemists as structural approaches have become today. © 2016 Elsevier Inc. All rights reserved.

Fiber-based modulated optical reflectance configuration allowing for offset pump and probe beams

Science.gov (United States)

Fleming, A.; Folsom, C.; Jensen, C.; Ban, H.

2016-12-01

A new fiber-based modulated optical reflectance configuration is developed in this work. The technique maintains the fiber-based heating laser (pump) and detection laser (probe) in close proximity at a fixed separation distance in a ceramic ferrule. The pump beam periodically heats the sample inducing thermal waves into the sample. The probe beam measures the temperature response at a known distance from the pump beam over a range of heating modulation frequencies. The thermal diffusivity of the sample may be calculated from the phase response between the input heat flux and the temperature response of a sample having a reflective surface. The unique measurement configuration is ideal for in situ measurements and has many advantages for laboratory-based systems. The design and development of the system are reported along with theoretical justification for the experimental design. The thermal diffusivities of Ge and SiC are measured and found to be within 10% of reported literature values. The diffusivity for SiO2 is measured with a relative difference of approximately 100% from the literature value when the ferrule is in contact with the sample. An additional measurement was made on the SiO2 sample with the ferrule not in contact resulting in a difference of less than 2% from the literature value. The difference in the SiO2 measurement when the ferrule is in contact with the sample is likely due to a parallel heat transfer path through the dual-fiber ferrule assembly.

Stimulated Brillouin scattering reflectivity in the case of a spatially smoothed laser beam interacting with an inhomogeneous plasma

International Nuclear Information System (INIS)

Tikhonchuk, V.T.; Mounaix, P.; Pesme, D.

1997-01-01

The stimulated Brillouin scattering (SBS) instability is investigated theoretically in the case of a spatially smoothed laser beam interacting with an inhomogeneous plasma in the regime of strong ion acoustic damping. The domain of parameters being considered corresponds to most of the present day experiments carried out with nanosecond laser pulses interacting with preformed plasmas: the characteristic length for convective amplification is assumed to be much shorter than the longitudinal correlation length of the laser field. The SBS reflectivity of one individual hot spot is analytically computed taking into account thermal noise emission and pump depletion within the hot spot. The SBS reflectivity of the whole beam is then obtained by summing up the individual hot spot reflectivities in accordance with their statistical distribution. copyright 1997 American Institute of Physics

Development of a Pump-Probe System using a Non-Coated ZnSe Beam Splitter Cube for an MIR-FEL

CERN Document Server

Heya, Manabu; Horiike, Hiroshi; Ishii, Katsonuri; Suzuki, Sachiko

2004-01-01

A pump-probe technique is essential for a proper understanding of laser interaction with tissue and material. Our pump-probe system divides the incident mid-infrared Free Electron Laser (MIR-FEL) into two beams with equal intensity, and crosses simultaneously the two incoming beams at the same position. One is for a pump beam, another is for a probe beam. Time-resolved absorption spectroscopy involving this technique gives us information on the vibrational dynamics of molecules. We have developed this system for an MIR-FEL using a non-coating ZnSe beam splitter cube. The beam splitter cube is composed of two ZnSe prisms in the shape like a trapezoid. The two pulses with equal intensity are generated due to Fresnel reflection and transmission at the boundary between two prisms, then are reflected due to total reflection at other side boundaries between each prism and air, and illuminate simultaneously the same spot. We have conducted a proof-of-concept of experiment of this system using an MIR-FEL. We showed t...

Angularly symmetric splitting of a light beam upon reflection and refraction at an air-dielectric plane boundary.

Science.gov (United States)

Azzam, R M A

2015-12-01

Conditions for achieving equal and opposite angular deflections of a light beam by reflection and refraction at an air-dielectric boundary are determined. Such angularly symmetric beam splitting (ASBS) is possible only if the angle of incidence is >60° by exactly one third of the angle of refraction. This simple law, plus Snell's law, leads to several analytical results that clarify all aspects of this phenomenon. In particular, it is shown that the intensities of the two symmetrically deflected beams can be equalized by proper choice of the prism refractive index and the azimuth of incident linearly polarized light. ASBS enables a geometrically attractive layout of optical systems that employ multiple prism beam splitters.

Mechanical beam isolator

International Nuclear Information System (INIS)

Post, R.F.; Vann, C.S.

1996-10-01

Back-reflections from a target, lenses, etc. can gain energy passing backwards through a laser just like the main beam gains energy passing forwards. Unless something blocks these back-reflections early in their path, they can seriously damage the laser. A Mechanical Beam Isolator is a device that blocks back-reflections early, relatively inexpensively, and without introducing aberrations to the laser beam

Quantification of protein based on single-molecule counting by total internal reflection fluorescence microscopy with adsorption equilibrium

International Nuclear Information System (INIS)

Wang Lei; Xu Guang; Shi Zhikun; Jiang Wei; Jin Wenrui

2007-01-01

We developed a sensitive single-molecule imaging method for quantification of protein by total internal reflection fluorescence microscopy with adsorption equilibrium. In this method, the adsorption equilibrium of protein was achieved between solution and glass substrate. Then, fluorescence images of protein molecules in a evanescent wave field were taken by a highly sensitive electron multiplying charge coupled device. Finally, the number of fluorescent spots corresponding to the protein molecules in the images was counted. Alexa Fluor 488-labeled goat anti-rat IgG(H + L) was chosen as the model protein. The spot number showed an excellent linear relationship with protein concentration. The concentration linear range was 5.4 x 10 -11 to 8.1 x 10 -10 mol L -1

Improved alternating gradient transport and focusing of neutral molecules

International Nuclear Information System (INIS)

Kalnins, Juris; Lambertson, Glen; Gould, Harvey

2001-01-01

Polar molecules, in strong-field seeking states, can be transported and focused by an alternating sequence of electric field gradients that focus in one transverse direction while defocusing in the other. We show by calculation and numerical simulation, how one may greatly improve the alternating gradient transport and focusing of molecules. We use a new optimized multipole lens design, a FODO lattice beam transport line, and lenses to match the beam transport line to the beam source and the final focus. We derive analytic expressions for the potentials, fields, and gradients that may be used to design these lenses. We describe a simple lens optimization procedure and derive the equations of motion for tracking molecules through a beam transport line. As an example, we model a straight beamline that transports a 560 m/s jet-source beam of methyl fluoride molecules 15 m from its source and focuses it to 2 mm diameter. We calculate the beam transport line acceptance and transmission, for a beam with velocity spread, and estimate the transmitted intensity for specified source conditions. Possible applications are discussed

Coherent Bichromatic Force Deflection of Molecules

Science.gov (United States)

Kozyryev, Ivan; Baum, Louis; Aldridge, Leland; Yu, Phelan; Eyler, Edward E.; Doyle, John M.

2018-02-01

We demonstrate the effect of the coherent optical bichromatic force on a molecule, the polar free radical strontium monohydroxide (SrOH). A dual-frequency retroreflected laser beam addressing the X˜2Σ+↔A˜2Π1 /2 electronic transition coherently imparts momentum onto a cryogenic beam of SrOH. This directional photon exchange creates a bichromatic force that transversely deflects the molecules. By adjusting the relative phase between the forward and counterpropagating laser beams we reverse the direction of the applied force. A momentum transfer of 70 ℏk is achieved with minimal loss of molecules to dark states. Modeling of the bichromatic force is performed via direct numerical solution of the time-dependent density matrix and is compared with experimental observations. Our results open the door to further coherent manipulation of molecular motion, including the efficient optical deceleration of diatomic and polyatomic molecules with complex level structures.

Ion-molecule interactions in crossed-beams

International Nuclear Information System (INIS)

Hansen, S.G.

1980-09-01

Interactions of the ions N + , F + , and CO 2 + with H 2 and/or its isotopes were examined using the crossed-beam technique in the low ( + ( 3 P) + H 2 → NH + + H, complex formation dominates up to 1.9 eV and a substantial interaction occurs between all collision partners up to 3.6 eV. The distribution of N + scattered nonreactively from H 2 also showed a long-lived complex channel below 1.9 eV. The reaction F + ( 3 P) + H 2 →FH + + H proceeded by a direct reaction mechanism at 0.20 to 1.07 eV. The reaction CO 2 + + D 2 → DCO 2 + + D gives asymmetric product distributions at 0.27 eV and above, indicating a direct reaction mechanism. Results indicated that there are probably barriers in the exit channels for DCO 2 + , DCO + , and D 2 O + products. The electronic state distributions of the N + , F + , and CO 2 + beams was investigated using beam attenuation and total luminescence techniques

Low pressure tritiation of molecules

International Nuclear Information System (INIS)

Moran, T.F.; Powers, J.C.; Lively, M.O.

1980-01-01

A method is described of tritiating sensitive biological molecules by depositing molecules of the substance to be tritiated on a supporting substrate in an evacuated vacuum chamber near, but not in the path of, an electron beam which traverses the chamber, admitting tritium gas into the chamber, and subjecting the tritium to the electron beam. Vibrationally excited tritium gas species are generated which collide and react with the substance thus incorporating tritium atoms into the substance. (U.K.)

Molecules in the cold environment of a supersonic free-jet beam: from spectroscopy of neutral-neutral interactions to a test of Bell's inequality

International Nuclear Information System (INIS)

Koperski, J; Fry, E S

2006-01-01

The supersonic free-jet expansion technique has been used in different fields of research in physics, physical chemistry and chemistry to study vibrational and rotational molecular structures in ground and excited electronic energy states as well as in cold chemistry to study chemical reactions in a unique environment. The supersonic beam technique, as a widely used method in laser spectroscopy of molecules, exploits a source of monokinetic, rotationally and vibrationally cold molecules, that are very weakly bound in their ground electronic states (van der Waals molecules). In experiments at Jagiellonian University the supersonic free-jet beam serves as a source of ground-state van der Waals objects in studies of neutral-neutral interactions between group 12 metal (M = Zn, Cd, Hg) and noble gas (NG) atoms. Recently, the method has been applied as a source of entangled 199 Hg atom pairs in order to test Bell's inequality in an experiment at Texas A and M University

Focused Beam Reflectance Measurement (FBRM) a promising tool for wet-end optimisation and web break prediction

NARCIS (Netherlands)

Lumpe, C.; Joore, L.; Homburg, K.; Verstraeten, E.

2001-01-01

The trends to increased speed and higher qualities have increased the need for wet-end control - especially for systems with on-line measuring devices and feed forward control. One possibility is the use of Focused Beam Reflectance Measurement (FBRM) to measure on-line particle counts and their

Direct observation of the Andreev reflection of a quasiparticle beam by quantum turbulence in superfluid 3He-B

International Nuclear Information System (INIS)

Bradley, D.I.; Fisher, S.N.; Guenault, A.M.; Lowe, M.R.; Pickett, G.R.; Rahm, A.

2003-01-01

A beam of quasiparticles from a black-body radiator is directed at a localized region of quantum turbulence generated by a vibrating wire resonator driven at super-critical velocity. We are able to measure directly the fraction of the incident quasiparticle beam which is retro-reflected from the turbulence by Andreev processes. Combining these measurements with previous measurements on the spatial extent of the turbulence may allow us to infer the vortex line density

An electrostatic elliptical mirror for neutral polar molecules.

Science.gov (United States)

González Flórez, A Isabel; Meek, Samuel A; Haak, Henrik; Conrad, Horst; Santambrogio, Gabriele; Meijer, Gerard

2011-11-14

Focusing optics for neutral molecules finds application in shaping and steering molecular beams. Here we present an electrostatic elliptical mirror for polar molecules consisting of an array of microstructured gold electrodes deposited on a glass substrate. Alternating positive and negative voltages applied to the electrodes create a repulsive potential for molecules in low-field-seeking states. The equipotential lines are parallel to the substrate surface, which is bent in an elliptical shape. The mirror is characterized by focusing a beam of metastable CO molecules and the results are compared to the outcome of trajectory simulations.

Molecular-beam electric-resonance studies of linear triatomic molecules

International Nuclear Information System (INIS)

Reinartz, J.M.L.J.

1976-01-01

In the present work, the MBER technique has been employed to investigate the spectra of the high temperature species KCN and CsOH and at low temperatures the spectra of five different isotopic species of OCS in natural mixture and the most abundant isotopic species of N 2 O and ClCN. For the low temperature species, spectra in the ground state and in the first excited state of the bending mode have been obtained. Bending vibrational effects on hyperfine constants and on electric and magnetic constants have been deduced from these spectra. The introduction of nozzle beam sources has been a factor of great importance for this study. For the ground states, high resolution spectra have been obtained both in external electric and in combined parallel electric and magnetic fields. These spectra could well be explained by the known theories for molecules in a 1 Σ state to within an experimental accuracy of about 50-150 Hz. Extension of the theory needed for the interpretation of the spectra for excited bending states is given. Hyperfine properties and electric and magnetic constants have been obtained with very high accuracy from the analysis of the frequencies of the observed transitions within one rotational state (ΔJ = 0 transitions)

A non-reflecting boundary for use in a finite element beam model of a railway track

Science.gov (United States)

Yang, Jiannan; Thompson, David J.

2015-02-01

Some beam-like structures such as a railway track are effectively infinite in nature. Analytical solutions exist for simple structures but numerical methods like the finite element (FE) method are often employed to study more complicated problems. However, when the FE method is used for structures of infinite extent it is essential to introduce artificial boundaries to limit the area of computation. Here, a non-reflecting boundary is developed using a damped tapered tip for application in a finite element model representing an infinite supported beam. The FE model of the tapered tip is validated against an analytical model based on Bessel functions. The reflection characteristics of the FE tapered tip are quantified using a wave/FE superposition method. It is shown that the damped tapered tip is much more effective than its constant counterpart and achieves reduction of the model size. The damped tapered tip is applied to a simple FE railway track model and good agreement is found when its point mobility is compared with an analytical infinite track model.

Continuous all-optical deceleration of molecular beams

Science.gov (United States)

Jayich, Andrew; Chen, Gary; Long, Xueping; Wang, Anna; Campbell, Wesley

2014-05-01

A significant impediment to generating ultracold molecules is slowing a molecular beam to velocities where the molecules can be cooled and trapped. We report on progress toward addressing this issue with a general optical deceleration technique for molecular and atomic beams. We propose addressing the molecular beam with a pump and dump pulse sequence from a mode-locked laser. The pump pulse counter-propagates with respect to the beam and drives the molecules to the excited state. The dump pulse co-propagates and stimulates emission, driving the molecules back to the ground state. This cycle transfers 2 ℏk of momentum and can generate very large optical forces, not limited by the spontaneous emission lifetime of the molecule or atom. Importantly, avoiding spontaneous emission limits the branching to dark states. This technique can later be augmented with cooling and trapping. We are working towards demonstrating this optical force by accelerating a cold atomic sample.

An Improved Measurement Method for the Strength of Radiation of Reflective Beam in an Industrial Optical Sensor Based on Laser Displacement Meter.

Science.gov (United States)

Bae, Youngchul

2016-05-23

An optical sensor such as a laser range finder (LRF) or laser displacement meter (LDM) uses reflected and returned laser beam from a target. The optical sensor has been mainly used to measure the distance between a launch position and the target. However, optical sensor based LRF and LDM have numerous and various errors such as statistical errors, drift errors, cyclic errors, alignment errors and slope errors. Among these errors, an alignment error that contains measurement error for the strength of radiation of returned laser beam from the target is the most serious error in industrial optical sensors. It is caused by the dependence of the measurement offset upon the strength of radiation of returned beam incident upon the focusing lens from the target. In this paper, in order to solve these problems, we propose a novel method for the measurement of the output of direct current (DC) voltage that is proportional to the strength of radiation of returned laser beam in the received avalanche photo diode (APD) circuit. We implemented a measuring circuit that is able to provide an exact measurement of reflected laser beam. By using the proposed method, we can measure the intensity or strength of radiation of laser beam in real time and with a high degree of precision.

Nanostructure sensor of presence and concentration of a target molecule

Science.gov (United States)

Schipper, John F. (Inventor)

2009-01-01

Method and system (i) to determine when a selected target molecule is present or absent in a fluid, (2) to estimate concentration of the target molecule in the fluid and (3) estimate possible presence of a second (different) target molecule in the fluid, by analyzing differences in resonant frequencies of vibration of a thin beam suspended in the fluid, after the fluid has moved across the beam.

High-order dynamic modeling and parameter identification of structural discontinuities in Timoshenko beams by using reflection coefficients

Science.gov (United States)

Fan, Qiang; Huang, Zhenyu; Zhang, Bing; Chen, Dayue

2013-02-01

Properties of discontinuities, such as bolt joints and cracks in the waveguide structures, are difficult to evaluate by either analytical or numerical methods due to the complexity and uncertainty of the discontinuities. In this paper, the discontinuity in a Timoshenko beam is modeled with high-order parameters and then these parameters are identified by using reflection coefficients at the discontinuity. The high-order model is composed of several one-order sub-models in series and each sub-model consists of inertia, stiffness and damping components in parallel. The order of the discontinuity model is determined based on the characteristics of the reflection coefficient curve and the accuracy requirement of the dynamic modeling. The model parameters are identified through the least-square fitting iteration method, of which the undetermined model parameters are updated in iteration to fit the dynamic reflection coefficient curve with the wave-based one. By using the spectral super-element method (SSEM), simulation cases, including one-order discontinuities on infinite- and finite-beams and a two-order discontinuity on an infinite beam, were employed to evaluate both the accuracy of the discontinuity model and the effectiveness of the identification method. For practical considerations, effects of measurement noise on the discontinuity parameter identification are investigated by adding different levels of noise to the simulated data. The simulation results were then validated by the corresponding experiments. Both the simulation and experimental results show that (1) the one-order discontinuities can be identified accurately with the maximum errors of 6.8% and 8.7%, respectively; (2) and the high-order discontinuities can be identified with the maximum errors of 15.8% and 16.2%, respectively; and (3) the high-order model can predict the complex discontinuity much more accurately than the one-order discontinuity model.

An Improved Measurement Method for the Strength of Radiation of Reflective Beam in an Industrial Optical Sensor Based on Laser Displacement Meter

Directory of Open Access Journals (Sweden)

Youngchul Bae

2016-05-01

Full Text Available An optical sensor such as a laser range finder (LRF or laser displacement meter (LDM uses reflected and returned laser beam from a target. The optical sensor has been mainly used to measure the distance between a launch position and the target. However, optical sensor based LRF and LDM have numerous and various errors such as statistical errors, drift errors, cyclic errors, alignment errors and slope errors. Among these errors, an alignment error that contains measurement error for the strength of radiation of returned laser beam from the target is the most serious error in industrial optical sensors. It is caused by the dependence of the measurement offset upon the strength of radiation of returned beam incident upon the focusing lens from the target. In this paper, in order to solve these problems, we propose a novel method for the measurement of the output of direct current (DC voltage that is proportional to the strength of radiation of returned laser beam in the received avalanche photo diode (APD circuit. We implemented a measuring circuit that is able to provide an exact measurement of reflected laser beam. By using the proposed method, we can measure the intensity or strength of radiation of laser beam in real time and with a high degree of precision.

Polarized infrared reflectance studies for wurtzite InN epilayers on Si(111) grown by molecular beam expitaxy

International Nuclear Information System (INIS)

Ooi, P.K.; Lee, S.C.; Ng, S.S.; Hassan, Z.; Abu Hassan, H.; Chen, W.L.

2011-01-01

Room temperature polarized infrared reflectance technique is employed to study the optical properties of wurtzite InN epilayers on Si(111) grown by molecular beam expitaxy. The reflection spectra are compared to the calculated spectra generated based on the anisotropic dielectric function model. Good agreement between the measured and calculated spectra is obtained. From the fit of the experimental curve, the reststrahlen parameters at the center of Brillouin zone, the carrier concentration and mobility as well as the epilayers thicknesses are determined. The values of the carrier concentration and mobility are in good agreement with the results obtained from the Hall effects measurements.

Crossed beam experiments

International Nuclear Information System (INIS)

Dolder, K.T.

1976-01-01

Many natural phenomena can only be properly understood if one has a detailed knowledge of interactions involving atoms, molecules, ions, electrons or photons. In the laboratory these processes are often studied by preparing beams of two types of particle and observing the reactions which occur when the beams intersect. Some of the more interesting of these crossed beam experiments and their results are discussed. Proposals to extend colliding beam techniques to high energy particle physics are also outlined. (author)

Beam broadening of polar molecules and clusters in deflection experiments.

Science.gov (United States)

Bulthuis, J; Kresin, V V

2012-01-07

A beam of rotating dipolar particles (molecules or clusters) will broaden when passed through an electric or magnetic field gradient region. This broadening, which is a common experimental observable, can be expressed in terms of the variance of the distribution of the resulting polarization orientation (the direction cosine). Here, the broadening for symmetric-top and linear rotors is discussed. These two types of rotors have qualitatively different low-field orientation distribution functions, but behave similarly in a strong field. While analytical expressions for the polarization variance can be derived from first-order perturbation theory, for experimental guidance it is important to identify the applicability and limitations of these expressions, and the general dependence of the broadening on the experimental parameters. For this purpose, the analytical results are compared with the full diagonalization of the rotational Stark-effect matrices. Conveniently for experimental estimations, it is found that for symmetric tops, the dependence of the broadening parameter on the rotational constant, the axial ratio, and the field strength remains similar to the analytical expression even outside of the perturbative regime. Also, it is observed that the shape envelope, the centroid, and the width of the orientation distribution function for a symmetric top are quite insensitive to the value of its rotational constant (except at low rotational temperatures).

A recycling molecular beam reactor

International Nuclear Information System (INIS)

Prada-Silva, G.; Haller, G.L.; Fenn, J.B.

1974-01-01

In a Recycling Molecular Beam Reactor, RMBR, a beam of reactant gas molecules is formed from a supersonic free jet. After collision with a target the molecules pass through the vacuum pumps and are returned to the nozzle source. Continuous recycling permits the integration of very small reaction probabilities into measurable conversions which can be analyzed by gas chromatography. Some preliminary experiments have been carried out on the isomerization of cyclopropane

Electric dipole moments of nanosolvated acid molecules in water clusters.

Science.gov (United States)

Guggemos, Nicholas; Slavíček, Petr; Kresin, Vitaly V

2015-01-30

The electric dipole moments of (H2O)nDCl (n=3-9) clusters have been measured by the beam-deflection method. Reflecting the (dynamical) charge distribution within the system, the dipole moment contributes information about the microscopic structure of nanoscale solvation. The addition of a DCl molecule to a water cluster results in a strongly enhanced susceptibility. There is evidence for a noticeable rise in the dipole moment occurring at n≈5-6. This size is consistent with predictions for the onset of ionic dissociation. Additionally, a molecular-dynamics model suggests that even with a nominally bound impurity an enhanced dipole moment can arise due to the thermal and zero-point motion of the proton and the water molecules. The experimental measurements and the calculations draw attention to the importance of fluctuations in defining the polarity of water-based nanoclusters and generally to the essential role played by motional effects in determining the response of fluxional nanoscale systems under realistic conditions.

Real-time reflectance-difference spectroscopy of GaAs molecular beam epitaxy homoepitaxial growth

Energy Technology Data Exchange (ETDEWEB)

Lastras-Martínez, A., E-mail: alm@cactus.iico.uaslp.mx, E-mail: alastras@gmail.com; Ortega-Gallegos, J.; Guevara-Macías, L. E.; Nuñez-Olvera, O.; Balderas-Navarro, R. E.; Lastras-Martínez, L. F. [Instituto de Investigación en Comunicación Optica, Universidad Autónoma de San Luis Potosí, Alvaro Obregón 64, San Luis Potosí, SLP 78000 (Mexico); Lastras-Montaño, L. A. [IBM T. J. Watson Research Center, Yorktown Heights, New York 10598 (United States); Lastras-Montaño, M. A. [Department of Electrical and Computer Engineering, University of California, Santa Barbara, Santa Barbara, California 93106 (United States)

2014-03-01

We report on real time-resolved Reflectance-difference (RD) spectroscopy of GaAs(001) grown by molecular beam epitaxy, with a time-resolution of 500 ms per spectrum within the 2.3–4.0 eV photon energy range. Through the analysis of transient RD spectra we demonstrated that RD line shapes are comprised of two components with different physical origins and determined their evolution during growth. Such components were ascribed to the subsurface strain induced by surface reconstruction and to surface stoichiometry. Results reported in this paper render RD spectroscopy as a powerful tool for the study of fundamental processes during the epitaxial growth of zincblende semiconductors.

Polarized infrared reflectance study of free standing cubic GaN grown by molecular beam epitaxy

International Nuclear Information System (INIS)

Lee, S.C.; Ng, S.S.; Hassan, H. Abu; Hassan, Z.; Zainal, N.; Novikov, S.V.; Foxon, C.T.; Kent, A.J.

2014-01-01

Optical properties of free standing cubic gallium nitride grown by molecular beam epitaxy system are investigated by a polarized infrared (IR) reflectance technique. A strong reststrahlen band, which reveals the bulk-like optical phonon frequencies, is observed. Meanwhile, continuous oscillation fringes, which indicate the sample consists of two homogeneous layers with different dielectric constants, are observed in the non-reststrahlen region. By obtaining the first derivative of polarized IR reflectance spectra measured at higher angles of incidence, extra phonon resonances are identified at the edges of the reststrahlen band. The observations are verified with the theoretical results simulated based on a multi-oscillator model. - Highlights: • First time experimental studies of IR optical phonons in bulk like, cubic GaN layer. • Detection of extra phonon modes of cubic GaN by polarized IR reflectance technique. • Revelation of IR multiphonon modes of cubic GaN by first derivative numerical method. • Observation of multiphonon modes requires very high angle of incidence. • Resonance splitting effect induced by third phonon mode is a qualitative indicator

Angularly symmetric splitting of a light beam upon reflection and refraction at an air-dielectric plane boundary: comment.

Science.gov (United States)

Andersen, Torben B

2016-05-01

In a recent paper, conditions for achieving equal and opposite angular deflections of a light beam by reflection and refraction at an interface between air and a dielectric were determined [J. Opt. Soc. Am. A32, 2436 (2015)JOAOD60740-323210.1364/JOSAA.32.002436]. The paper gives plots of angles of incidence and refraction as a function of the prism refractive index as well as plots of reflectances and incident linear-polarization azimuth angles as functions of the refractive index. We show here that it is possible to express these quantities as simple algebraic functions of the refractive index.

New structural studies of liquid crystal by reflectivity and resonant X-ray diffraction

International Nuclear Information System (INIS)

Fernandes, P.

2007-04-01

This memory presents three structural studies of smectic Liquid Crystals by reflectivity and resonant diffraction of X-rays. It is divided in five chapters. In the first a short introduction to Liquid Crystals is given. In particular, the smectic phases that are the object of this study are presented. The second chapter is consecrated to the X-ray experimental techniques that were used in this work. The three last chapters present the works on which this thesis can be divided. Chapter three demonstrates on free-standing films of MHPOBC (historic liquid crystal that possesses the antiferroelectric sub-phases) the possibility to extend the technique of resonant X-ray diffraction to liquid crystals without resonant element. In the fourth chapter the structure of the B 2 liquid crystal phase of bent-core molecules (or banana molecules) is elucidated by using resonant X-ray diffraction combined with polarization analysis of the diffracted beam. A model of the polarization of the resonant beam diffracted by four different structures proposed for the B 2 phase is developed in this chapter. In the fifth chapter a smectic binary mixture presenting a very original critical point of phase separation is studied by X-ray reflectivity and optical microscopy. A concentration gradient in the direction perpendicular to the plane of the film seems to be induced by the free-standing film geometry. The results of a simplified model of the system are compatible with this interpretation

Trapping molecules in two and three dimensions

International Nuclear Information System (INIS)

Pinkse, PW.H.; Junglen, T.; Rieger, T.; Rangwala, S.A.; Windpassinger, P.; Rempe, G.

2005-01-01

Full text: Cold molecules offer a new testing ground for quantum-physical effects in nature. For example, producing slow beams of large molecules could push experiments studying the boundary between quantum interference and classical particles up towards ever heavier particles. Moreover, cold molecules, in particular YbF, seem an attractive way to narrow down the constraints on the value of the electron dipole moment and finally, quantum information processing using chains of cold polar molecules or vibrational states in molecules have been proposed. All these proposals rely on advanced production and trapping techniques, most of which are still under development. Therefore, novel production and trapping techniques for cold molecules could offer new possibilities not found in previous methods. Electric traps hold promise for deep trap potentials for neutral molecules. Recently we have demonstrated two-dimensional trapping of polar molecules in a four-wire guide using electrostatic and electrodynamic trapping techniques. Filled from a thermal effusive source, such a guide will deliver a beam of slow molecules, which is an ideal source for interferometry experiments with large molecules, for instance. Here we report about the extension of this work to three-dimensional trapping. Polar molecules with a positive Stark shift can be trapped in the minimum of an electrostatic field. We have successfully tested a large volume electrostatic trap for ND3 molecules. A special feature of this trap is that it can be loaded continuously from an electrostatic guide, at a temperature of a few hundred mK. (author)

A Zeeman slower for diatomic molecules

Science.gov (United States)

Petzold, M.; Kaebert, P.; Gersema, P.; Siercke, M.; Ospelkaus, S.

2018-04-01

We present a novel slowing scheme for beams of laser-coolable diatomic molecules reminiscent of Zeeman slowing of atomic beams. The scheme results in efficient compression of the one-dimensional velocity distribution to velocities trappable by magnetic or magneto-optical traps. We experimentally demonstrate our method in an atomic testbed and show an enhancement of flux below v = 35 m s‑1 by a factor of ≈20 compared to white light slowing. 3D Monte Carlo simulations performed to model the experiment show excellent agreement. We apply the same simulations to the prototype molecule 88Sr19F and expect 15% of the initial flux to be continuously compressed in a narrow velocity window at around 10 m s‑1. This is the first experimentally shown continuous and dissipative slowing technique in molecule-like level structures, promising to provide the missing link for the preparation of large ultracold molecular ensembles.

Real-time reflectance-difference spectroscopy of GaAs molecular beam epitaxy homoepitaxial growth

Directory of Open Access Journals (Sweden)

A. Lastras-Martínez

2014-03-01

Full Text Available We report on real time-resolved Reflectance-difference (RD spectroscopy of GaAs(001 grown by molecular beam epitaxy, with a time-resolution of 500 ms per spectrum within the 2.3–4.0 eV photon energy range. Through the analysis of transient RD spectra we demonstrated that RD line shapes are comprised of two components with different physical origins and determined their evolution during growth. Such components were ascribed to the subsurface strain induced by surface reconstruction and to surface stoichiometry. Results reported in this paper render RD spectroscopy as a powerful tool for the study of fundamental processes during the epitaxial growth of zincblende semiconductors.

New results in the relation between intensity distribution of reflected molecular beams and spatial distribution of elementary crystal cells in solids

International Nuclear Information System (INIS)

Nikuradse, A.; Weidner, J.

1974-01-01

Analytic expressions for the intensity distribution of a molecular beam reflected by a solid surface which consists of face centered cubic elementary cells have been studied. One has also tried to study the influence of the spatial distribution of the elementary crystal cells on the intensity of reflection. Some curves which had been evaluated and designed by a computer are now published. The Kratzer potential of interaction has alway been supposed [fr

Energy storage and redistribution in molecules

International Nuclear Information System (INIS)

Hinze, J.

1983-01-01

This book presents information on the following topics: chemistry and spectroscopy of molecules at high levels of excitation; energy and phase randomization in large molecules as probed by laser spectroscopy; intramolecular processes in isolated polyatomic molecules; pulse-probe measurements in low-temperature, low-pressure SF 6 ; the photodissociation dynamics of H 2 S and CF 3 NO; photofragment spectroscopy of the NO 2 dissociation; preparation, laser spectroscopy and predissociation of alkali dimers in supersonic nozzle beams; excited states of small molecules - collisional quenching and photodissociation; quantum-state-resolved scattering of lithium hydride; and molecular negative ions

Radius of curvature measurement of spherical smooth surfaces by multiple-beam interferometry in reflection

Science.gov (United States)

Abdelsalam, D. G.; Shaalan, M. S.; Eloker, M. M.; Kim, Daesuk

2010-06-01

In this paper a method is presented to accurately measure the radius of curvature of different types of curved surfaces of different radii of curvatures of 38 000,18 000 and 8000 mm using multiple-beam interference fringes in reflection. The images captured by the digital detector were corrected by flat fielding method. The corrected images were analyzed and the form of the surfaces was obtained. A 3D profile for the three types of surfaces was obtained using Zernike polynomial fitting. Some sources of uncertainty in measurement were calculated by means of ray tracing simulations and the uncertainty budget was estimated within λ/40.

Isotope separation by photodissociation of Van der Wall's molecules

International Nuclear Information System (INIS)

Lee, Y.T.

1977-01-01

A method of separating isotopes based on the dissociation of a Van der Waal's complex is described. A beam of molecules of a Van der Waal's complex containing, as one partner of the complex, a molecular species in which an element is present in a plurality of isotopes is subjected to radiation from a source tuned to a frequency which will selectively excite vibrational motion by a vibrational transition or through electronic transition of those complexed molecules of the molecular species which contain a desired isotope. Since the Van der Waal's binding energy is much smaller than the excitational energy of vibrational motion, the thus excited Van der Waal's complex dissociate into molecular components enriched in the desired isotope. The recoil velocity associated with vibrational to translational and rotational relaxation will send the separated molecules away from the beam whereupon the product enriched in the desired isotope can be separated from the constituents of the beam

Alternating gradient focusing and deceleration of polar molecules

NARCIS (Netherlands)

Bethlem, H.L.; Tarbutt, M.R.; Kupper, J.; Carty, D.; Wohlfart, K.; Hinds, E.A.; Meijer, G.

2006-01-01

Beams of polar molecules can be focused using an array of electrostatic lenses in alternating gradient (AG) configuration. They can also be accelerated or decelerated by applying an appropriate high-voltage switching sequence to the lenses. AG focusing is applicable to molecules in both low-field-

Continuous centrifuge decelerator for polar molecules.

Science.gov (United States)

Chervenkov, S; Wu, X; Bayerl, J; Rohlfes, A; Gantner, T; Zeppenfeld, M; Rempe, G

2014-01-10

Producing large samples of slow molecules from thermal-velocity ensembles is a formidable challenge. Here we employ a centrifugal force to produce a continuous molecular beam with a high flux at near-zero velocities. We demonstrate deceleration of three electrically guided molecular species, CH3F, CF3H, and CF3CCH, with input velocities of up to 200  m s(-1) to obtain beams with velocities below 15  m s(-1) and intensities of several 10(9)  mm(-2) s(-1). The centrifuge decelerator is easy to operate and can, in principle, slow down any guidable particle. It has the potential to become a standard technique for continuous deceleration of molecules.

Molecular-beam studies of primary photochemical processes

Energy Technology Data Exchange (ETDEWEB)

Lee, Y.T.

1982-12-01

Application of the method of molecular-beam photofragmentation translational spectroscopy to the investigation of primary photochemical processes of polyatomic molecules is described. Examples will be given to illustrate how information concerning the energetics, dynamics, and mechanism of dissociation processes can be obtained from the precise measurements of angular and velocity distributions of products in an experiment in which a well-defined beam of molecules is crossed with a laser.

Molecular-beam studies of primary photochemical processes

International Nuclear Information System (INIS)

Lee, Y.T.

1982-12-01

Application of the method of molecular-beam photofragmentation translational spectroscopy to the investigation of primary photochemical processes of polyatomic molecules is described. Examples will be given to illustrate how information concerning the energetics, dynamics, and mechanism of dissociation processes can be obtained from the precise measurements of angular and velocity distributions of products in an experiment in which a well-defined beam of molecules is crossed with a laser

A theoretical and experimental investigation of the interaction between gas molecules and cryogenic surfaces

International Nuclear Information System (INIS)

Varlam, M.; Steflea, D.; Chiriloaie, N.

1992-01-01

The cryo-pumping performance of a cryo-surface subjected to the impingement of low-pressure, thermal-velocity air flow is experimentally and theoretically investigated. Our purpose is to determine the angular dependence of capture coefficients for gas molecules incident on a cryogenic surface under conditions closely approximating those prevailing in cryo-pumped high vacuum chambers. The classical model for the interaction of gas atoms and the solid surface - the 'soft-tube' model - is developed and the basic assumption are examined. Starting from this theory we have calculated the capture coefficient of the Ag - N system and these values are discussed in terms of principal parameters considered. Despite the many simplifying assumptions, this model has the important attribute that it yields closed-form expressions for the capture coefficient of gas molecules. The molecular beam technique offers a direct experimental method for determining the capture coefficient for molecules with given angles of incidence by measuring the incident and reflected molecular fluxes. An experimental setup is also designed and the method for determining these coefficients is proposed. (Author)

Optimal beam sources for Stark decelerators in collision experiments: a tutorial review

International Nuclear Information System (INIS)

Vogels, Sjoerd N.; Gao, Zhi; Meerakker, Sebastiaan Y.T. van de

2015-01-01

With the Stark deceleration technique, packets of molecules with a tunable velocity, a narrow velocity spread, and a high state purity can be produced. These tamed molecular beams find applications in high resolution spectroscopy, cold molecule trapping, and controlled scattering experiments. The quality and purity of the packets of molecules emerging from the decelerator critically depend on the specifications of the decelerator, but also on the characteristics of the molecular beam pulse with which the decelerator is loaded. We consider three frequently used molecular beam sources, and discuss their suitability for molecular beam deceleration experiments, in particular with the application in crossed beam scattering in mind. The performance of two valves in particular, the Nijmegen Pulsed Valve and the Jordan Valve, is illustrated by decelerating ND 3 molecules in a 2.6 meter-long Stark decelerator. We describe a protocol to characterize the valve, and to optimally load the pulse of molecules into the decelerator. We characterize the valves regarding opening time duration, optimal valve-to-skimmer distance, mean velocity, velocity spread, state purity, and relative intensity. (orig.)

Interferometric optical fiber microcantilever beam biosensor

Science.gov (United States)

Wavering, Thomas A.; Meller, Scott A.; Evans, Mishell K.; Pennington, Charles; Jones, Mark E.; VanTassell, Roger; Murphy, Kent A.; Velander, William H.; Valdes, E.

2000-12-01

With the proliferation of biological weapons, the outbreak of food poisoning occurrences, and the spread of antibiotic resistant strains of pathogenic bacteria, the demand has arisen for portable systems capable of rapid, specific, and quantitative target detection. The ability to detect minute quantities of targets will provide the means to quickly assess a health hazardous situation so that the appropriate response can be orchestrated. Conventional test results generally require hours or even several days to be reported, and there is no change for real-time feedback. An interferometric optical fiber microcantilever beam biosensor has successfully demonstrated real time detection of target molecules. The microcantilever biosensor effectively combines advanced technology from silicon micromachining, optical fiber sensor, and biochemistry to create a novel detection device. This approach utilizes affinity coatings on micromachiend cantilever beams to attract target molecules. The presence of the target molecule causes bending in the cantilever beam, which is monitored using an optical displacement system. Dose-response trials have shown measured responses at nanogram/ml concentrations of target molecules. Sensitivity is expected to extend from the nanogram to the picogram range of total captured mass as the microcantilever sensors are optimized.

Bragg reflection transmission filters for variable resolution monochromators

International Nuclear Information System (INIS)

Chapman, D.

1989-01-01

There are various methods for improving the angular and spectral resolution of monochromator and analyzer systems. The novel system described here, though limited to higher x-ray energies (>20keV), is based on a dynamical effect occurring on the transmitted beam with a thin perfect crystal plate set in the Bragg reflection case. In the case of Bragg reflection from a perfect crystal, the incident beam is rapidly attenuated as it penetrates the crystal in the range of reflection. This extinction length is of the order of microns. The attenuation length, which determines the amount of normal transmission through the plate is generally much longer. Thus, in the range of the Bragg reflection the attenuation of the transmitted beam can change by several orders of magnitude with a small change in energy or angle. This thin crystal plate cuts a notch in the transmitted beam with a width equal to its Darwin width, thus acting as a transmission filter. When used in a non-dispersive mode with other monochromator crystals, the filter when set at the Bragg angle will reflect the entire Darwin width of the incident beam and transmit the wings of the incident beam distribution. When the element is offset in angle by some fraction of the Darwin width, the filter becomes useful in adjusting the angular width of the transmitted beam and removing a wing. Used in pairs with a symmetric offset, the filters can be used to continuously adjust the intrinsic angular divergence of the beam with good wing reduction. Instances where such filters may be useful are in improving the angular resolution of a small angle scattering camera. These filters may be added to a Bonse-Hart camera with one pair on the incident beam to reduce the intrinsic beam divergence and a second pair on the analyzer arm to improve the analyzer resolution. 2 refs., 3 Figs

Synchrotron-based multiple-beam FTIR chemical imaging of a multi-layered polymer in transmission and reflection: towards cultural heritage applications

Science.gov (United States)

Unger, Miriam; Mattson, Eric; Schmidt Patterson, Catherine; Alavi, Zahrasadet; Carson, David; Hirschmugl, Carol J.

2013-04-01

IRENI (infrared environmental imaging) is a recently commissioned Fourier transform infrared (FTIR) chemical imaging beamline at the Synchrotron Radiation Center in Madison, WI, USA. This novel beamline extracts 320 mrad of radiation, horizontally, from one bending magnet. The optical transport separates and recombines the beam into 12 parallel collimated beams to illuminate a commercial FTIR microspectrometer (Bruker Hyperion 3000) equipped with a focal plane array detector where single pixels in the detector image a projected sample area of either 0.54×0.54 μm2 or 2×2 μm2, depending in the measurement geometry. The 12 beams are partially overlapped and defocused, similar to wide-field microscopy, homogeneously illuminating a relatively large sample area compared to single-beam arrangements. Both transmission and reflection geometries are used to examine a model cross section from a layered polymer material. The compromises for sample preparation and measurement strategies are discussed, and the chemical composition and spatial definition of the layers are distinguished in chemical images generated from data sets. Deconvolution methods that may allow more detailed data analysis are also discussed.

Supersonic molecular beam experiments on surface chemical reactions.

Science.gov (United States)

Okada, Michio

2014-10-01

The interaction of a molecule and a surface is important in various fields, and in particular in complex systems like biomaterials and their related chemistry. However, the detailed understanding of the elementary steps in the surface chemistry, for example, stereodynamics, is still insufficient even for simple model systems. In this Personal Account, I review our recent studies of chemical reactions on single-crystalline Cu and Si surfaces induced by hyperthermal oxygen molecular beams and by oriented molecular beams, respectively. Studies of oxide formation on Cu induced by hyperthermal molecular beams demonstrate a significant role of the translational energy of the incident molecules. The use of hyperthermal molecular beams enables us to open up new chemical reaction paths specific for the hyperthermal energy region, and to develop new methods for the fabrication of thin films. On the other hand, oriented molecular beams also demonstrate the possibility of understanding surface chemical reactions in detail by varying the orientation of the incident molecules. The steric effects found on Si surfaces hint at new ways of material fabrication on Si surfaces. Controlling the initial conditions of incoming molecules is a powerful tool for finely monitoring the elementary step of the surface chemical reactions and creating new materials on surfaces. Copyright © 2014 The Chemical Society of Japan and Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Angularly symmetric splitting of a light beam upon reflection and refraction at an air-dielectric plane boundary: reply.

Science.gov (United States)

Azzam, R M A

2016-05-01

The simplified explicit expressions derived by Andersen [J. Opt. Soc. Am. A33, 984 (2016)JOAOD60740-323210.1364/JOSAA.32.000984], that relate to angularly symmetric beam splitting by reflection and refraction at an air-dielectric interface recently described by Azzam [J. Opt. Soc. Am. A32, 2436 (2015)JOAOD60740-323210.1364/JOSAA.32.002436], are welcome. A few additional remarks are also included in my reply to Andersen's comment.

Laser control of atomic beam motion and applications

International Nuclear Information System (INIS)

Balykin, V.I.; Letokhov, V.S.

1987-01-01

The authors present the results of an experimental investigation of the control of atomic beam motion by the light pressure of laser radiation. Collimation, focusing and reflection of the atomic beam are considered. Collimation of the atomic beam is achieved by the interaction of laser radiation with atoms, when the light pressure force depends only on the atom's velocity. A similar regime of atomic beam interaction with radiation was performed with transversal irradiation of a beam by the axis-symmetrical field. The axis-symmetrical field was formed by laser radiation reflected from the conical mirror surface of a reflecting axicon. The axis of the atomic beam coincided with that of the axicon. The collimation regime was reached under negative detuning of the laser radiation frequency from the atomic transition frequency by a value equal to several homogeneous widths. With positive detuning by the same value the regime of beam decollimation was observed. The density of atoms on the beam axis was changed by 10 3 times, when the collimation regime was replaced by that of decollimation. Focusing of the atomic beam was achieved by light pressure dependent on the atomic coordinate. Focusing was performed within the field configuration formed by divergent laser Gaussian beams propagating in the direction +- X, +- Y of a Cartesian coordinate system. Waists of the laser beams were an equal distance from the atomic beam axis. With an atomic beam propagating along the z axis, expressions for local distance and a formula for the laser lens were obtained. Focusing of the atomic beam was experimentally accomplished, and the image of the atomic beam was received. In this work they also investigated reflection of the atomic beam by laser radiation. The possibility of creating the optics of a neutral atomic beam is shown

High resolution laser spectroscopy as a diagnostic tool in beams

International Nuclear Information System (INIS)

Bergmann, K.; Hefter, U.; Hering, P.

1977-01-01

The combination of high resolution laser spectroscopy with the technique of molecular beams allows a very detailed beam research since molecules or atoms in specific quantum states can be sampled yielding previously unavailable sources of data. In these experiments a Na/Na 2 beam emerges from a 0.2 mm nozzle and is collimated by a 2 mm wide slit 50 cm downstream. To probe the molecules a single mode Ar + -laser was used which can be tuned within the gain profile of the laser line (8 GHz) to several transitions between specific levels in the ground state and second electronically excited state of the Na 2 molecule. (Auth.)

Versatile microfluidic total internal reflection (TIR)-based devices: application to microbeads velocity measurement and single molecule detection with upright and inverted microscope.

Science.gov (United States)

Le, Nam Cao Hoai; Yokokawa, Ryuji; Dao, Dzung Viet; Nguyen, Thien Duy; Wells, John C; Sugiyama, Susumu

2009-01-21

A poly(dimethylsiloxane) (PDMS) chip for Total Internal Reflection (TIR)-based imaging and detection has been developed using Si bulk micromachining and PDMS casting. In this paper, we report the applications of the chip on both inverted and upright fluorescent microscopes and confirm that two types of sample delivery platforms, PDMS microchannel and glass microchannel, can be easily integrated depending on the magnification of an objective lens needed to visualize a sample. Although any device configuration can be achievable, here we performed two experiments to demonstrate the versatility of the microfluidic TIR-based devices. The first experiment was velocity measurement of Nile red microbeads with nominal diameter of 500 nm in a pressure-driven flow. The time-sequenced fluorescent images of microbeads, illuminated by an evanescent field, were cross-correlated by a Particle Image Velocimetry (PIV) program to obtain near-wall velocity field of the microbeads at various flow rates from 500 nl/min to 3000 nl/min. We then evaluated the capabilities of the device for Single Molecule Detection (SMD) of fluorescently labeled DNA molecules from 30 bp to 48.5 kbp and confirm that DNA molecules as short as 1105 bp were detectable. Our versatile, integrated device could provide low-cost and fast accessibility to Total Internal Reflection Fluorescent Microscopy (TIRFM) on both conventional upright and inverted microscopes. It could also be a useful component in a Micro-Total Analysis System (micro-TAS) to analyze nanoparticles or biomolecules near-wall transport or motion.

Implementation of real-time multiple reflection and Fresnel absorption of laser beam in keyhole

International Nuclear Information System (INIS)

Cho, Jung-Ho; Na, Suck-Joo

2006-01-01

A computational analysis of laser keyhole welding is achieved. The main driving force to make the molten pool as a narrow and deep keyhole is the recoil pressure induced by evaporation of the material. Also, the multiple reflection effect on the keyhole wall plays an important role in making the keyhole deeper and raising its total energy absorption rate. Multiple reflection and Fresnel absorption are implemented simultaneously with the proposed ray tracing technique in a discrete grid cell system during the simulation for every single time step. In particular, the Fresnel absorption model is chosen as an energy transfer mechanism from laser beam to workpiece. With all the governing equations including continuity, momentum and energy equation, the VOF method is adopted to trace the free surface of the molten pool. Simulation results are compared with the experimental ones to verify its validity. A pulsed Nd : YAG laser was used for keyhole welding experiments on mild steel plates of 7 mm thickness. It was observed that the generated keyhole maintains its solidified shape without any closing phenomenon both in the experiments and in the simulations

Implementation of real-time multiple reflection and Fresnel absorption of laser beam in keyhole

Energy Technology Data Exchange (ETDEWEB)

Cho, Jung-Ho; Na, Suck-Joo [Department of Mechanical Engineering, KAIST, 373-1 Guseong-dong, Yuseong-gu, Daejeon 305-701 (Korea, Republic of)

2006-12-21

A computational analysis of laser keyhole welding is achieved. The main driving force to make the molten pool as a narrow and deep keyhole is the recoil pressure induced by evaporation of the material. Also, the multiple reflection effect on the keyhole wall plays an important role in making the keyhole deeper and raising its total energy absorption rate. Multiple reflection and Fresnel absorption are implemented simultaneously with the proposed ray tracing technique in a discrete grid cell system during the simulation for every single time step. In particular, the Fresnel absorption model is chosen as an energy transfer mechanism from laser beam to workpiece. With all the governing equations including continuity, momentum and energy equation, the VOF method is adopted to trace the free surface of the molten pool. Simulation results are compared with the experimental ones to verify its validity. A pulsed Nd : YAG laser was used for keyhole welding experiments on mild steel plates of 7 mm thickness. It was observed that the generated keyhole maintains its solidified shape without any closing phenomenon both in the experiments and in the simulations.

Survey of coherent ion reflection at the quasi-parallel bow shock

International Nuclear Information System (INIS)

Onsager, T.G.; Thomsen, M.F.; Gosling, J.T.; Bame, S.J.; Russell, C.T.

1990-01-01

Ions coherently reflected off the Earth's bow shock have previously been observed both when the upstream geometry is quasi-perpendicular and when it is quasi-parallel. In the case of quasiperpendicular geometry, the ions are reflected in a nearly specular manner and are quickly carried back into the shock by the convecting magnetic field. In the quasi-parallel geometry, however, near-specularly reflected ions' guiding center velocities would on the average be directed away from the shock, allowing the ions to escape into the upstream region. The conditions under which coherent reflection occurs and the subsequent coupling of the reflected ions to the incoming solar wind plasma are important factors when assessing the contribution of the reflected ions to the downstream temperature increase and the shock structure. The survey presented in this paper, along with previously reported observations, suggests that near-specularly reflected ions are indeed an important aspect of energy dissipation at the Earth's quasi-parallel bow shock. The authors find that (1) cool, coherent, near-specularly reflected ion beams are detected over nearly the full range of upstream plasma paraameters commonly found at the Earth's bow shock; (2) the beams are typically observed only near the shock ramp or some shock-like feature; and (3) the observed beam velocities are almost always consistent with what one would expect for near-specularly reflected ions after only a small fraction of a gyroperiod following reflection. The second and third points indicate that the beams spread very quickly in velocity space. This spread in velocities could be due either to interactions between the beam and incoming solar wind ions or to some initially small velocity spread in the beam

Suppression of beam-excited electron waves by an externally applied RF signal

International Nuclear Information System (INIS)

Fukumasa, Osamu; Itatani, Ryohei

1980-11-01

Suppression of the beam-excited electron wave in a bounded system is investigated in connection with the beam distribution function. Wave suppression has two different processes depending on whether injected beams are reflected at the other end or not. In the absence of reflected beam electrons, deformation of the beam distribution function is observed in relation to the suppression of the electron wave. However, when beam electrons are reflected, the external wave suppresses the electron wave but distribution function shows no appreciable change. These experimental results show that nonlinear behaviors of beam electrons, namely behaviors of reflected beams, are quite important for wave suppression. By using the method of partial simulation, interaction between two waves in the bounded system including nonlinear motions of beam electrons is studied numerically. Qualitative agreement between experimental and numerical results is obtained. (author)

Aligning molecules with intense nonresonant laser fields

DEFF Research Database (Denmark)

Larsen, J.J.; Safvan, C.P.; Sakai, H.

1999-01-01

Molecules in a seeded supersonic beam are aligned by the interaction between an intense nonresonant linearly polarized laser field and the molecular polarizability. We demonstrate the general applicability of the scheme by aligning I2, ICl, CS2, CH3I, and C6H5I molecules. The alignment is probed...... by mass selective two dimensional imaging of the photofragment ions produced by femtosecond laser pulses. Calculations on the degree of alignment of I2 are in good agreement with the experiments. We discuss some future applications of laser aligned molecules....

Neutral beam program

International Nuclear Information System (INIS)

Anon.

1979-01-01

The structure of the beam injection program for the Doublet-3 device is discussed. The design considerations for the beam line and design parameters for the Doublet-3 ion souce are given. Major components of the neutral beam injector system are discussed in detail. These include the neutralizer, magnetic shielding, reflecting magnets, vacuum system, calorimeter and beam dumps, and drift duct. The planned location of the two-injector system for Doublet-3 is illustrated and site preparation is considered. The status of beamline units 1 and 2 and the future program schedule are discussed

Beam front accelerators

International Nuclear Information System (INIS)

Reiser, M.

1982-01-01

An intense relativistic electron beam cannot propagate in a metal drift tube when the current exceeds the space charge limit. Very high charge density and electric field gradients (10 2 to 10 3 MV/m) develop at the beam front and the electrons are reflected. When a neutral gas or a plasma is present, collective acceleration of positive ions occur, and the resulting charge neutralization enables the beam to propagate. Experimental results, theoretical understanding, and schemes to achieve high ion energies by external control of the beam front velocity will be reviewed

In Situ Focused Beam Reflectance Measurement (FBRM, Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR and Raman Characterization of the Polymorphic Transformation of Carbamazepine

Directory of Open Access Journals (Sweden)

Sohrab Rohani

2012-02-01

Full Text Available The objective of this work was to study the polymorphic transformation of carbamazepine from Form II to Form III in 1-propanol during seeded isothermal batch crystallization. First, the pure Form II and Form III were obtained and characterized. Then their solubilities and metastable zone limits were measured by in-situ attenuated total reflectance Fourier transform infrared (ATR-FTIR spectroscopy and focused beam reflectance measurement (FBRM. A transition temperature at about 34.2 °C was deduced suggesting the enantiotropic nature of this compound over the studied temperature range. To quantify the polymorph ratio during the transformation process, a new in-situ quantitative method was developed to measure the fraction of Form II by Raman spectroscopy. Successful tracking of the nucleation of the stable form and the transformation from Form II to Form III during isothermal crystallization was achieved by Raman spectroscopy and FBRM. The results from these three in-situ techniques, FBRM, FTIR and Raman were consistent with each other. The results showed a strong dependency on the amount of seeds added during isothermal crystallization.

Many-beam electron extinction distances in zirconium

International Nuclear Information System (INIS)

Cann, C.D.

1977-05-01

Many-beam extinction distances have been calculated for twenty-two of the lowest order reflections in zirconium. Ten beams comprising the directly transmitted and the nine lowest order systematic reflections were included in each calculation. Extinction distances for each reflection were determined for electron accelerating voltages of 100 and 200 kV, both at the exact Bragg condition and at deviations up to two Bragg angles from this condition. (author)

Quantum interference experiments with complex organic molecules

International Nuclear Information System (INIS)

Eibenberger, S. I.

2015-01-01

Matter-wave interference with complex particles is a thriving field in experimental quantum physics. The quest for testing the quantum superposition principle with highly complex molecules has motivated the development of the Kapitza-Dirac-Talbot-Lau interferometer (KDTLI). This interferometer has enabled quantum interference with large organic molecules in an unprecedented mass regime. In this doctoral thesis I describe quantum superposition experiments which we were able to successfully realize with molecules of masses beyond 10 000 amu and consisting of more than 800 atoms. The typical de Broglie wavelengths of all particles in this thesis are in the order of 0.3-5 pm. This is significantly smaller than any molecular extension (nanometers) or the delocalization length in our interferometer (hundreds of nanometers). Many vibrational and rotational states are populated since the molecules are thermally highly excited (300-1000 K). And yet, high-contrast quantum interference patterns could be observed. The visibility and position of these matter-wave interference patterns is highly sensitive to external perturbations. This sensitivity has opened the path to extensive studies of the influence of internal molecular properties on the coherence of their associated matter waves. In addition, it enables a new approach to quantum-assisted metrology. Quantum interference imprints a high-contrast nano-structured density pattern onto the molecular beam which allows us to resolve tiny shifts and dephasing of the molecular beam. I describe how KDTL interferometry can be used to investigate a number of different molecular properties. We have studied vibrationally-induced conformational changes of floppy molecules and permanent electric dipole moments using matter-wave deflectometry in an external electric field. We have developed a new method for optical absorption spectroscopy which uses the recoil of the molecules upon absorption of individual photons. This allows us to

Industrial applications or electron beams

International Nuclear Information System (INIS)

Martin, J. I.

2001-01-01

Industrial use of electron beams began in the 1950's with the crosslinking of polyethylene film and wire insulation. Today the number of electron beam Processing Systems installed for industrial applications throughout the world has grown to more than six hundred stations in over 35 countries. Total installed power is now approaching 40 megawatts (over 8 million tons of products per year). Electron beam is now utilized by many major industries including plastics, automotive, rubber goods, wire and cable, electrical insulation, semiconductor, medical, packaging, or pollution control. The principal effect of high-energy electrons is to produce ions in the materials treated, resulting in the liberation of orbital electrons. As a result, the original molecule is modified and the ree radicals combine to form new molecules with new chemical reactions or dis organisation od the DNA chains of living organisms (insects, fungus, microorganisms, etc.). (Author) 8 refs

A source of translationally cold molecular beams

Science.gov (United States)

Sarkozy, Laszlo C.

Currently the fields studying or using molecules with low kinetic energies are experiencing an unprecedented growth. Astronomers and chemists are interested in chemical reactions taking place at temperatures below or around 20 K, spectroscopists could make very precise measurements on slow molecules and molecular physicists could chart the potential energy surfaces more accurately. And the list continues. All of these experiments need slow molecules, with kinetic energies from around 10 cm-1 down to 0. Several designs of cold sources have already been made. The most interesting ones are presented. This work describes the design and the testing of a cold source based on the collisional cooling technique: the molecules of interest are cooled well below their freezing point by a precooled buffer gas. This way condensation is avoided. The source is a copper cell cooled to 4.2 K by an external liquid helium bath. The cell is filled with cold buffer gas (helium). The molecules of choice (ammonia) are injected through a narrow tube in the middle of the cell. The cold molecules leave the cell through a 1 millimeter hole. Two versions of pulsing techniques have been employed: a shutter blade which covers the source hole and opens it only for short moments, and a chopper that modulates the beam further downstream. Both produced pulse lengths around 1 millisecond. The source is tested in an experiment in which the emerging molecules are focused and detected. Time of flight technique is used to measure the kinetic energies. Two detectors have been employed: a microwave cavity to analyze the state of the molecules in the beam, and a mass spectrometer to measure the number density of the particles. The molecules coming out of the source hole are formed into a beam by an electrostatic quadrupole state selector. The quantum mechanical aspects and the elements of electrodynamics involved in the focusing are described. A computer simulation program is presented, which helped

Behavior of obliquely incident vector Bessel beams at planar interfaces

KAUST Repository

Salem, Mohamed; Bagci, Hakan

2013-01-01

We investigate the behavior of full-vector electromagnetic Bessel beams obliquely incident at an interface between two electrically different media. We employ a Fourier transform domain representation of Bessel beams to determine their behavior upon reflection and transmission. This transform, which is geometric in nature, consists of elliptical support curves with complex weighting associated with them. The behavior of the scattered field at an interface is highly complex, owing to its full-vector nature; nevertheless, this behavior has a straightforward representation in the transform domain geometry. The analysis shows that the reflected field forms a different vector Bessel beam, but in general, the transmitted field cannot be represented as a Bessel beam. Nevertheless, using this approach, we demonstrate a method to propagate a Bessel beam in the refractive medium by launching a non- Bessel beam at the interface. Several interesting phenomena related to the behavior of Bessel beams are illustrated, such as polarized reflection at Brewster's angle incidence, and the Goos-Hänchen and Imbert-Federov shifts in the case of total reflection. © 2013 Optical Society of America.

Behavior of obliquely incident vector Bessel beams at planar interfaces

KAUST Repository

Salem, Mohamed

2013-01-01

We investigate the behavior of full-vector electromagnetic Bessel beams obliquely incident at an interface between two electrically different media. We employ a Fourier transform domain representation of Bessel beams to determine their behavior upon reflection and transmission. This transform, which is geometric in nature, consists of elliptical support curves with complex weighting associated with them. The behavior of the scattered field at an interface is highly complex, owing to its full-vector nature; nevertheless, this behavior has a straightforward representation in the transform domain geometry. The analysis shows that the reflected field forms a different vector Bessel beam, but in general, the transmitted field cannot be represented as a Bessel beam. Nevertheless, using this approach, we demonstrate a method to propagate a Bessel beam in the refractive medium by launching a non- Bessel beam at the interface. Several interesting phenomena related to the behavior of Bessel beams are illustrated, such as polarized reflection at Brewster\\'s angle incidence, and the Goos-Hänchen and Imbert-Federov shifts in the case of total reflection. © 2013 Optical Society of America.

Wave-optical evaluation of interference fringes and wavefront phase in a hard-x-ray beam totally reflected by mirror optics.

Science.gov (United States)

Yamauchi, Kazuto; Yamamura, Kazuya; Mimura, Hidekazu; Sano, Yasuhisa; Saito, Akira; Endo, Katsuyoshi; Souvorov, Alexei; Yabashi, Makina; Tamasaku, Kenji; Ishikawa, Tetsuya; Mori, Yuzo

2005-11-10

The intensity flatness and wavefront shape in a coherent hard-x-ray beam totally reflected by flat mirrors that have surface bumps modeled by Gaussian functions were investigated by use of a wave-optical simulation code. Simulated results revealed the necessity for peak-to-valley height accuracy of better than 1 nm at a lateral resolution near 0.1 mm to remove high-contrast interference fringes and appreciable wavefront phase errors. Three mirrors that had different surface qualities were tested at the 1 km-long beam line at the SPring-8/Japan Synchrotron Radiation Research Institute. Interference fringes faded when the surface figure was corrected below the subnanometer level to a spatial resolution close to 0.1 mm, as indicated by the simulated results.

Engineering and control of cold molecules. Making manipulating and exploiting ultra-cold polar molecules

International Nuclear Information System (INIS)

Bigelow, N.P.; Haimberger, C.; Kleinert, J.; Tscherneck, M.; Holmes, M.E.

2005-01-01

In the last 12 months several groups have demonstrated the use of photo association to create cold heteronuclear (polar) molecules. We report on the formation of translationally cold NaCs molecules starting from a laser-cooled atomic vapor of Na and Cs atoms. Colliding atoms are transferred into bound molecular states in a two-step photoactivated process. We find a translational temperature of T ≅ 260 mK. To increase the density and number of trapped atoms, dark-spot techniques are used on the MOT and a Zeeman slowed sodium beam is used to load the sodium atoms into the trap. Spectroscopy of these molecules is underway using time-of-flight ion detection and trap-loss. Initial REMPI measurements indicate that both singlet and triplet states are being populated by the spontaneous-decay driven process. We measure a rate constant for molecule formation of K NaCs = 7.43 · 10 15 cm 3 s -1 . (author)

Soluble intercellular adhesion molecule-1 and interleukin-6 levels reflect endothelial dysfunction in patients with primary hypercholesterolaemia treated with atorvastatin.

Science.gov (United States)

Nawawi, H; Osman, N S; Annuar, R; Khalid, B A K; Yusoff, K

2003-08-01

Adhesion molecules and cytokines are involved in the pathogenesis of intimal injury in atherosclerosis but their relationship with endothelial function remains unclear. The objectives of this study were to examine the effects of atorvastatin on soluble adhesion molecules, interleukin-6 (IL-6) and brachial artery endothelial-dependent flow mediated dilatation (FMD) in patients with familial (FH) and non-familial hypercholesterolaemia (NFH). A total of 74 patients (27 FH and 47 NFH) were recruited. Fasting lipid profiles, soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular-cellular adhesion molecule-1 (sVCAM-1), E-selectin, IL-6 and FMD were measured at baseline, 2 weeks, 3 and 9 months post-atorvastatin treatment (FH--80 mg/day, NFH--10 mg/day). In both groups, compared to baseline, sICAM-1 levels were significantly reduced at 2 weeks, further reduced at 3 months and maintained at 9 months (P<0.0001). The IL-6 levels were significantly reduced at 3 months and 9 months compared to baseline for FH (P<0.005) and NFH (P<0.0001). In both groups, the FMD at 2 weeks was higher than baseline (P<0.005), with progressive improvement up to 9 months. FMD was negatively correlated with sICAM-1 and IL-6. In conclusion, both low and high doses of atorvastatin lead to early progressive improvement in endothelial function in patients with primary hypercholesterolaemia. sICAM-1 and IL-6 levels reflect endothelial dysfunction in these patients.

Molecular-beam studies

International Nuclear Information System (INIS)

Wexler, S.; Parks, E.K.; Young, C.E.; Dehmer, P.M.; Kuhry, J.G.; Cohen, R.B.; Pobo, L.G.

1975-01-01

Highlights of experimental results obtained with chemical accelerators are described under the following headings: development of an aerodynamic source of fast I atoms and I 2 molecules; chemi-ionization processes in collisions of uranium atoms with oxygen molecules; chemi-ionization reactions in other metal--O 2 collisions (La, Ce, Th); kinetic surface ionization; and single-crystal beam source. Relative cross sections for formation of various collision products are shown, as a function of energy in the eV range. (12 figures) (U.S.)

Functional Reflective Polarizer for Augmented Reality and Color Vision Deficiency

Science.gov (United States)

2016-03-03

augment reality system is relatively high as compared to a polarizing beam splitter or a conventional reflective polarizer. Such a functional reflective...brightness of the display [7]. A key component for polarization management is polarizing beam splitter (PBS). Even though the PBS has exceptional...polarizer that can be incorporated into a compact augmented reality system. The design principle of the functional reflective polarizer is explained and

EDITORIAL: Focus on Cold and Ultracold Molecules FOCUS ON COLD AND ULTRACOLD MOLECULES

Science.gov (United States)

Carr, Lincoln D.; Ye, Jun

2009-05-01

Cold and ultracold molecules are the next wave of ultracold physics, giving rise to an exciting array of scientific opportunities, including many body physics for novel quantum phase transitions, new states of matter, and quantum information processing. Precision tests of fundamental physical laws benefit from the existence of molecular internal structure with exquisite control. The study of novel collision and reaction dynamics will open a new chapter of quantum chemistry. Cold molecules bring together researchers from a variety of fields, including atomic, molecular, and optical physics, chemistry and chemical physics, quantum information science and quantum simulations, condensed matter physics, nuclear physics, and astrophysics, a truly remarkable synergy of scientific explorations. For the past decade there have been steady advances in direct cooling techniques, from buffer-gas cooling to cold molecular beams to electro- and magneto-molecular decelerators. These techniques have allowed a large variety of molecules to be cooled for pioneering studies. Recent amazing advances in experimental techniques combining the ultracold and the ultraprecise have furthermore brought molecules to the point of quantum degeneracy. These latter indirect cooling techniques magnetically associate atoms from a Bose-Einstein condensate and/or a quantum degenerate Fermi gas, transferring at 90% efficiency highly excited Fano-Feshbach molecules, which are on the order of 10 000 Bohr radii in size, to absolute ground state molecules just a few Bohr across. It was this latter advance, together with significant breakthroughs in internal state manipulations, which inspired us to coordinate this focus issue now, and is the reason why we say the next wave of ultracold physics has now arrived. Whether directly or indirectly cooled, heteronuclear polar molecules offer distinct new features in comparison to cold atoms, while sharing all of their advantages (purity, high coherence

Theory of reflection reflection and transmission of electromagnetic, particle and acoustic waves

CERN Document Server

Lekner, John

2016-01-01

This book deals with the reflection of electromagnetic and particle waves by interfaces. The interfaces can be sharp or diffuse. The topics of the book contain absorption, inverse problems, anisotropy, pulses and finite beams, rough surfaces, matrix methods, numerical methods,  reflection of particle waves and neutron reflection. Exact general results are presented, followed by long wave reflection, variational theory, reflection amplitude equations of the Riccati type, and reflection of short waves. The Second Edition of the Theory of Reflection is an updated and much enlarged revision of the 1987 monograph. There are new chapters on periodically stratified media, ellipsometry, chiral media, neutron reflection and reflection of acoustic waves. The chapter on anisotropy is much extended, with a complete treatment of the reflection and transmission properties of arbitrarily oriented uniaxial crystals. The book gives a systematic and unified treatment reflection and transmission of electromagnetic and particle...

Excimer lasers utilizing XeF and XeCl molecules

Energy Technology Data Exchange (ETDEWEB)

Bychkov, Yu I; Konovalov, I N; Losev, V F; Mesyats, G A; Ryzhov, V V; Tarasenko, V F; Fedorov, A I; Shemyakina, S B; Yastremskii, A G

1978-12-01

The results are given of an experimental and theoretical study of XeF (wavelength approx. 350 nm) and XeCl (wavelength approx. 308 nm) lasers excited by an electron beam, a discharge stabilized by an electron beam, and a rapid discharge. These lasers are representative of ones employing halides of noble gases, which are the most powerful sources of stimulated emission in the uv region. The XeCl laser is shown to have good emission characteristics with various methods of excitation. An analysis of the kinetics of processes in the plasma of lasers utilizing halides of noble gases showed that the main channel for the transfer of the beam's energy to the formation of excimer molecules is the ionic channel. An efficiency of about 2.6 percent and a specific radiant energy of 10 J.l/sup -1/ showed that XeCl* is one of the most effective excimer molecules.

Atom capture and loss in ion molecule collisions

International Nuclear Information System (INIS)

Breinig, M.; Lasley, S.E.; Gaither, C.C. III.

1985-01-01

Progress is reported in measuring the energy and angular distribution of protons emerging with velocity close to the beam velocity from the target region when Ar + beams collide with a CH 4 target and ArH + beams collide with a He target at asymptotically high speeds. The protons result from the transfer of a target constituent to the projectile (atom capture) or from the dissociation of the projectile molecule in the collision (atom loss). For atom capture processes the Thomas peak is clearly observed. 10 refs., 3 figs

Study of phosphoric acid crystallization using a focused beam reflectance measurement method

Energy Technology Data Exchange (ETDEWEB)

Ma, Yong [School of Chemistry and Resource Environment, Linyi Normal University, Linyi Shandong 276005 (China); Chen, Kui; Wu, Yanyang; Zhu, Jiawen [Chemical Engineering Research Center, East China University of Science and Technology, Shanghai 200237 (China); Sheng, Yong [SINOCHEN Fuling Chemical Industrial Co., Ltd, Chongqing 226005 (China)

2010-10-15

A way for restoring the crystal size distributions (CSD) from measured chord length distributions (CLD) was reported in this paper. The kinetics of phosphoric acid crystallization process was investigated in cooling mode using focused beam reflectance measurement (FBRM) and digital photo technique. In order to restore the CSD from measured CLD and verify the reliability of FBRM data, digital photo technique in real time and optical microscope were applied in large crystal size and small range, respectively. Results indicated a converting constant A existed between CLD and CSD when crystal growth follows size-independent growth (Mcabe's {delta}L law) law. It was verified by Malvern particles size analysis method. The converting constant A varied with crystal morphology. The crystal growth order increased with the stirring increasing speed during phosphoric acid crystallization process. The trend was especially notable at higher speed situations. It can illustrate that the state of phosphoric acid hemihydrate crystal growth was controlled by both diffusion and surface-integration with the increasing stirring speed. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

A modified gradient approach for the growth of low-density InAs quantum dot molecules by molecular beam epitaxy

Science.gov (United States)

Sharma, Nandlal; Reuter, Dirk

2017-11-01

Two vertically stacked quantum dots that are electronically coupled, so called quantum dot molecules, are of great interest for the realization of solid state building blocks for quantum communication networks. We present a modified gradient approach to realize InAs quantum dot molecules with a low areal density so that single quantum dot molecules can be optically addressed. The individual quantum dot layers were prepared by solid source molecular beam epitaxy depositing InAs on GaAs(100). The bottom quantum dot layer has been grown without substrate rotation resulting in an In-gradient across the surface, which translated into a density gradient with low quantum dot density in a certain region of the wafer. For the top quantum dot layer, separated from the bottom quantum dot layer by a 6 nm thick GaAs barrier, various InAs amounts were deposited without an In-gradient. In spite of the absence of an In-gradient, a pronounced density gradient is observed for the top quantum dots. Even for an In-amount slightly below the critical thickness for a single dot layer, a density gradient in the top quantum dot layer, which seems to reproduce the density gradient in the bottom layer, is observed. For more or less In, respectively, deviations from this behavior occur. We suggest that the obvious influence of the bottom quantum dot layer on the growth of the top quantum dots is due to the strain field induced by the buried dots.

Optics with an Atom Laser Beam

International Nuclear Information System (INIS)

Bloch, Immanuel; Koehl, Michael; Greiner, Markus; Haensch, Theodor W.; Esslinger, Tilman

2001-01-01

We report on the atom optical manipulation of an atom laser beam. Reflection, focusing, and its storage in a resonator are demonstrated. Precise and versatile mechanical control over an atom laser beam propagating in an inhomogeneous magnetic field is achieved by optically inducing spin flips between atomic ground states with different magnetic moment. The magnetic force acting on the atoms can thereby be effectively switched on and off. The surface of the atom optical element is determined by the resonance condition for the spin flip in the inhomogeneous magnetic field. More than 98% of the incident atom laser beam is reflected specularly

Electro-induced reactions of biologically important molecules

International Nuclear Information System (INIS)

Kocisek, J.

2010-01-01

The thesis presents the results of research activities in the field of electron interactions with biologically relevant molecules which was carried out during my PhD studies at the Department of Experimental Physics, Comenius University in Bratislava. Electron induced interactions with biologically relevant molecules were experimentally studied using crossed electron-molecule beams experiment. The obtained results, were presented in four publications in international scientific journals. First study of deals with electron impact ionisation of furanose alcohols [see 1. in list of author publications on page 22]. It has been motivated by most important works in the field of electron induced damages of DNA bases [4]. Studied 3-hydroxytetrahydrofuran and tetrahydrofurfuryl alcohol, are important model molecules for more complex biological systems (e.g. deoxyribose).The influence of hydroxyl group on stabilisation of the positive ions of the molecules, together with the stability of furan ring in ionized form are main themes of the study. The studies of small amides and aminoacids are connected to scientific studies in the field of formation of the aminoacids and other biologically relevant molecules in space and works trying to explain electron induced processes in more complex molecules[12, 13, 24]. The most important results were obtained for aminoacid Serine [see 2. in list of author publications on page 22]. We have showed that additional OH group of Serine considerably lower the reaction enthalpy limit of reactions resulting to formation of neutral water molecules, in comparison to other amino acids. Also the study of (M-H)- reaction channel using the electron beam with FWHM under 100 meV is of high importance in the field. The last part of the thesis is focused on the electron interactions with organosilane compounds. Materials prepared from organosilane molecules in plasmas have wide range of applications in both biology and medicine. We have studied electron

Energy redistribution in diatomic molecules on surfaces

International Nuclear Information System (INIS)

Asscher, M.; Somorjai, G.A.

1984-04-01

Translational and internal degrees of freedom of a scattered beam of NO molecules from a Pt(111) single crystal surface were measured as a function of scattering angle and crystal temperature in the range 450 to 1250K. None of the three degrees of freedom were found to fully accommodate to the crystal temperature, the translational degree being the most accommodated and the rotational degree of freedom the least. A precursor state model is suggested to account for the incomplete accommodation of translational and vibrational degrees of freedom as a function of crystal temperature and incident beam energy. The vibrational accommodation is further discussed in terms of a competition between desorption and vibrational excitation processes, thus providing valuable information on the interaction between vibrationally excited molecules and surfaces. Energy transfer into rotational degrees of freedom is qualitatively discussed

A Physical Description of the Response of Coupled Beams

DEFF Research Database (Denmark)

Hugin, Claus Thomas

1997-01-01

An analytical method is presented for computing the vibrational response and the net transmitted power of bending wave fields in system consisting of coupled finite beams. The method is based on a wave approach that utilises the reflection and transmission coefficients of the different beam joint...... are valid for frequencies above which the influence of the reflected near fields for each of the beam elements is negligible. The method is demonstrated on different configurations of beams coupled in extension of each other....

Metasurface for multi-channel terahertz beam splitters and polarization rotators

Science.gov (United States)

Zang, XiaoFei; Gong, HanHong; Li, Zhen; Xie, JingYa; Cheng, QingQing; Chen, Lin; Shkurinov, Alexander P.; Zhu, YiMing; Zhuang, SongLin

2018-04-01

Terahertz beam splitters and polarization rotators are two typical devices with wide applications ranging from terahertz communication to system integration. However, they are faced with severe challenges in manipulating THz waves in multiple channels, which is desirable for system integration and device miniaturization. Here, we propose a method to design ultra-thin multi-channel THz beam splitters and polarization rotators simultaneously. The reflected beams are divided into four beams with nearly the same density under illumination of linear-polarized THz waves, while the polarization of reflected beams in each channel is modulated with a rotation angle or invariable with respect to the incident THz waves, leading to the multi-channel polarization rotator (multiple polarization rotation in the reflective channels) and beam splitter, respectively. Reflective metasurfaces, created by patterning metal-rods with different orientations on a polyimide film, were fabricated and measured to demonstrate these characteristics. The proposed approach provides an efficient way of controlling polarization of THz waves in various channels, which significantly simplifies THz functional devices and the experimental system.

Simulation of reflectivity spectrum for non-absorbing multilayer ...

Indian Academy of Sciences (India)

Reflectivity simulation is an essential tool for the design and optimization of optical thin ... with the experimental results of the multilayer optical thin films grown by electron-beam evaporation ... beam splitters [4] and various optical filters. ... thickness (QWOT) layer AR coating and multilayer HR coating using electron- beam ...

A comparative study of the enhancement of molecular emission in a spatially confined plume through optical emission spectroscopy and probe beam deflection measurements

Energy Technology Data Exchange (ETDEWEB)

Ding, Dayu; Liang, Peipei; Wu, Jiada; Xu, Ning; Ying, Zhifeng; Sun, Jian, E-mail: jsun@fudan.edu.cn

2013-01-01

The spatial confinement effects of shock wave on the expansion of a carbon plume induced by pulsed laser ablation of graphite in air and the enhancement of the plume emission were studied by optical emission spectroscopy and probe beam deflection measurements. A metal disk was set in the way of the ablation-generated shock wave to block and reflect the supersonically propagating shock wave. The reflected shock wave propagated backwards and confined the expanding plume. The optical emission of CN molecules was enhanced in contrast to the case without the block disk and the emission enhancement was dependent on the position of the disk. Based on the results of time-integrated and -resolved optical emission spectroscopy, and the time- and space-resolved probe beam deflection measurements, the processes occurring in the plume were discussed and the mechanisms responsible for the enhancement of molecular emission in the spatially confined plume were investigated. - Highlights: ► Spatial confinement and optical emission enhancement of carbon plume were studied. ► Ablation-generated shockwave propagating in air was reflected by a block disk. ► The effects of reflected shockwave on the emission enhancement were confirmed. ► The reflect shockwave confined the carbon plume and enhanced the plume emission.

A comparative study of the enhancement of molecular emission in a spatially confined plume through optical emission spectroscopy and probe beam deflection measurements

International Nuclear Information System (INIS)

Ding, Dayu; Liang, Peipei; Wu, Jiada; Xu, Ning; Ying, Zhifeng; Sun, Jian

2013-01-01

The spatial confinement effects of shock wave on the expansion of a carbon plume induced by pulsed laser ablation of graphite in air and the enhancement of the plume emission were studied by optical emission spectroscopy and probe beam deflection measurements. A metal disk was set in the way of the ablation-generated shock wave to block and reflect the supersonically propagating shock wave. The reflected shock wave propagated backwards and confined the expanding plume. The optical emission of CN molecules was enhanced in contrast to the case without the block disk and the emission enhancement was dependent on the position of the disk. Based on the results of time-integrated and -resolved optical emission spectroscopy, and the time- and space-resolved probe beam deflection measurements, the processes occurring in the plume were discussed and the mechanisms responsible for the enhancement of molecular emission in the spatially confined plume were investigated. - Highlights: ► Spatial confinement and optical emission enhancement of carbon plume were studied. ► Ablation-generated shockwave propagating in air was reflected by a block disk. ► The effects of reflected shockwave on the emission enhancement were confirmed. ► The reflect shockwave confined the carbon plume and enhanced the plume emission

Merged neutral beams

Energy Technology Data Exchange (ETDEWEB)

Osterwalder, Andreas [Ecole Polytechnique Federale de Lausanne (EPFL), Institute for Chemical Sciences and Engineering, Lausanne (Switzerland)

2015-12-15

A detailed description of a merged beam apparatus for the study of low energy molecular scattering is given. This review is intended to guide any scientist who plans to construct a similar experiment, and to provide some inspiration in describing the approach we chose to our goal. In our experiment a supersonic expansion of paramagnetic particles is merged with one of polar molecules. A magnetic and an electric multipole guide are used to bend the two beams onto the same axis. We here describe in detail how the apparatus is designed, characterised, and operated. (orig.)

Neutron transmission and reflection at a copper single crystal

Energy Technology Data Exchange (ETDEWEB)

Adib, M.; Maayouf, R.M.A.; Abdel-Kawy, A.; Fayek, M.; Habib, N. (Atomic Energy Establishment, Cairo (Egypt). Reactor and Neutron Physics Dept.); Wahba, M. (Ain Shams Univ., Cairo (Egypt). Dept. of Engineering Physics and Mathematics)

1991-06-01

Neutron transmission and reflection at a copper single crystal cut along the (111) plane were studied with the fixed-scattering-angle spectrometer installed at the ET-RR-1 reactor. The transmission was measured for neutron wavelengths between 0.15 and 0.46 nm and various orientations of the (111) plane with respect to the incident beam. When used as a neutron band pass filter, the crystal is optimally oriented when the neutron beam is incident parallel to the (111) direction. The reflectivity was measured for the (111) plane at 45deg with respect to the incident beam. The results were found to be in reasonable agreement with a value predicted for the reflected intensity at an imperfect crystal with finite absorption. (orig.).

Neutron transmission and reflection at a copper single crystal

International Nuclear Information System (INIS)

Adib, M.; Maayouf, R.M.A.; Abdel-Kawy, A.; Fayek, M.; Habib, N.; Wahba, M.

1991-01-01

Neutron transmission and reflection at a copper single crystal cut along the (111) plane were studied with the fixed-scattering-angle spectrometer installed at the ET-RR-1 reactor. The transmission was measured for neutron wavelengths between 0.15 and 0.46 nm and various orientations of the (111) plane with respect to the incident beam. When used as a neutron band pass filter, the crystal is optimally oriented when the neutron beam is incident parallel to the [111] direction. The reflectivity was measured for the (111) plane at 45deg with respect to the incident beam. The results were found to be in reasonable agreement with a value predicted for the reflected intensity at an imperfect crystal with finite absorption. (orig.) [de

Polarizer reflectivity variations

International Nuclear Information System (INIS)

Ozarski, R.G.; Prior, J.

1980-01-01

On Shiva the beam energy along the chain is monitored using available reflections and/or transmission through beam steering, splitting, and polarizing optics without the intrusion of any additional glass for diagnostics. On the preamp table the diagnostic signal is obtained from the signal transmitted through turning mirrors. At the input of each chain the signal is obtained from the transmission through one of the mirrors used for the chain input alignment sensor (CHIP). At the chain output the transmission through the final turning mirror is used. These diagnostics have proved stable and reliable. However, one of the prime diagnostic locations is at the output of the beta rod. The energy at this location is measured by collecting small reflections from the last polarizer surface of the beta Pockels cell polarizer package. Unfortunately, calibration of this diagnostic has varied randomly, seldom remaining stable for a week or more. The cause of this fluctuation has been investigated for the past year and'it has been discovered that polarizer reflectivity varies with humidity. This report will deal with the possible causes that were investigated, the evidence that humidity is causing the variation, and the associated mechanism

Reflection-type hologram for atoms

International Nuclear Information System (INIS)

Shimizu, Fujio; Fujita, Jun-ichi

2002-01-01

A cold metastable neon atomic beam was manipulated with a reflective amplitude hologram that was encoded on a silicon surface. A black-and-white pattern of atoms was reconstructed on a microchannel plate detector. The hologram used the enhanced quantum reflection developed by authors and was made of a two-dimensional array of rectangular low and high reflective cells. The surface of the high reflective cell was composed of regularly spaced roof-shaped ridges, while the low reflective cell was simply a flat surface. The hologram was the first demonstration of reflective atom-optical elements that used universal interaction between a neutral atom and solid surface

Nanosecond and femtosecond mass spectroscopic analysis of a molecular beam produced by the spray-jet technique

International Nuclear Information System (INIS)

Yamada, Toshiki; Shinohara, Hidenori; Kamikado, Toshiya; Okuno, Yoshishige; Suzuki, Hitoshi; Mashiko, Shinro; Yokoyama, Shiyoshi

2008-01-01

The spray-jet molecular beam apparatus enabled us to produce a molecular beam of non-volatile molecules under high vacuum from a sprayed mist of sample solutions. The apparatus has been used in spectroscopic studies and as a means of molecular beam deposition. We analyzed the molecular beam, consisting of non-volatile, solvent, and carrier-gas molecules, by using femtosecond- and nanosecond- laser mass spectroscopy. The information thus obtained provided insight into the molecular beam produced by the spray-jet technique

Properties of backward electromagnetic waves and negative reflection in ferrite films

International Nuclear Information System (INIS)

Vashkovsky, Anatolii V; Lock, Edwin H

2006-01-01

For a backward electromagnetic wave (magnetostatic wave) in a ferrite film, reflection from a perfect mirror formed by the straight edge of the film is investigated experimentally and theoretically. It is found that when the incident wave is collinear (the group velocity vector and the wave vector have opposite directions), negative reflection occurs at any angle of incidence, i.e., the incident and reflected beams are on the same side of the normal to the boundary. It is discovered that a noncollinear backward wave is nonreciprocal in the sense that its energy can be localized both near the surface and in the middle of the film. This property, previously observed only for surface magnetostatic waves, provides both the efficiency of generating and receiving the wave and the possibility of observing the reflected beam. A situation is realized where wave reflection results in two reflected beams. The properties of backward electromagnetic waves propagating in ferrite films are briefly analyzed. (methodological notes)

Surface flatness measurement of quasi-parallel plates employing three-beam interference with strong reference beam

Science.gov (United States)

Sunderland, Zofia; Patorski, Krzysztof

2016-12-01

A big challenge for standard interferogram analysis methods such as Temporal Phase Shifting or Fourier Transform is a parasitic set of fringes which might occur in the analyzed fringe pattern intensity distribution. It is encountered, for example, when transparent glass plates with quasi-parallel surfaces are tested in Fizeau or Twyman-Green interferometers. Besides the beams reflected from the plate front surface and the interferometer reference the beam reflected from the plate rear surface also plays important role; its amplitude is comparable with the amplitude of other beams. In result we face three families of fringes of high contrast which cannot be easily separated. Earlier we proposed a competitive solution for flatness measurements which relies on eliminating one of those fringe sets from the three-beam interferogram and separating two remaining ones with the use of 2D Continuous Wavelet Transform. In this work we cover the case when the intensity of the reference beam is significantly higher than the intensities of two object beams. The main advantage of differentiating beam intensities is the change in contrast of individual fringe families. Processing of such three-beam interferograms is modified but also takes advantage of 2D CWT. We show how to implement this method in Twyman-Green and Fizeau setups and compare this processing path and measurement procedures with previously proposed solutions.

Interactions of electrons with biologically important molecules

International Nuclear Information System (INIS)

Pisklova, K.; Papp, P.; Stano, M.

2012-01-01

For the study of interactions of low-energy electrons with the molecules in the gas phase, the authors used electron-molecule cross-beam apparatus. The experiment is carried out in high vacuum, where molecules of the tested compound are inducted through a capillary. For purposes of this experiment the sample was electrically heated to 180 Deg C., giving a bundle of GlyGly molecules into the gas phase. The resulting signals can be evaluated in two different modes: mass spectrum - at continuous electron energy (e.g. 100 eV) they obtained the signal of intensity of the ions according to their mass to charge ratio; ionization and resonance spectra - for selected ion mass when the authors received the signal of intensity of the ions, depending on the energy of interacting electron.

Quantitative resonant soft x-ray reflectivity of ultrathin anisotropic organic layers: Simulation and experiment of PTCDA on Au

International Nuclear Information System (INIS)

Capelli, R.; Koshmak, K.; Giglia, A.; Mukherjee, S.; Nannarone, S.; Mahne, N.; Doyle, B. P.; Pasquali, L.

2016-01-01

Resonant soft X-ray reflectivity at the carbon K edge, with linearly polarized light, was used to derive quantitative information of film morphology, molecular arrangement, and electronic orbital anisotropies of an ultrathin 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) film on Au(111). The experimental spectra were simulated by computing the propagation of the electromagnetic field in a trilayer system (vacuum/PTCDA/Au), where the organic film was treated as an anisotropic medium. Optical constants were derived from the calculated (through density functional theory) absorption cross sections of the single molecule along the three principal molecular axes. These were used to construct the dielectric tensor of the film, assuming the molecules to be lying flat with respect to the substrate and with a herringbone arrangement parallel to the substrate plane. Resonant soft X-ray reflectivity proved to be extremely sensitive to film thickness, down to the single molecular layer. The best agreement between simulation and experiment was found for a film of 1.6 nm, with flat laying configuration of the molecules. The high sensitivity to experimental geometries in terms of beam incidence and light polarization was also clarified through simulations. The optical anisotropies of the organic film were experimentally determined and through the comparison with calculations, it was possible to relate them to the orbital symmetry of the empty electronic states.

Quantitative resonant soft x-ray reflectivity of ultrathin anisotropic organic layers: Simulation and experiment of PTCDA on Au

Energy Technology Data Exchange (ETDEWEB)

Capelli, R.; Koshmak, K.; Giglia, A.; Mukherjee, S.; Nannarone, S. [IOM-CNR, s.s. 14, Km. 163.5 in AREA Science Park, Basovizza, 34149 Trieste (Italy); Mahne, N. [Elettra, s.s. 14, km 163.5 in AREA Science Park, Basovizza, 34149 Trieste (Italy); Doyle, B. P. [Department of Physics, University of Johannesburg, P.O. Box 524, Auckland Park 2006 (South Africa); Pasquali, L., E-mail: luca.pasquali@unimore.it [IOM-CNR, s.s. 14, Km. 163.5 in AREA Science Park, Basovizza, 34149 Trieste (Italy); Department of Physics, University of Johannesburg, P.O. Box 524, Auckland Park 2006 (South Africa); Dipartimento di Ingegneria “Enzo Ferrari,” Università di Modena e Reggio Emilia, Via Vignolese 905, 41125 Modena (Italy)

2016-07-14

Resonant soft X-ray reflectivity at the carbon K edge, with linearly polarized light, was used to derive quantitative information of film morphology, molecular arrangement, and electronic orbital anisotropies of an ultrathin 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) film on Au(111). The experimental spectra were simulated by computing the propagation of the electromagnetic field in a trilayer system (vacuum/PTCDA/Au), where the organic film was treated as an anisotropic medium. Optical constants were derived from the calculated (through density functional theory) absorption cross sections of the single molecule along the three principal molecular axes. These were used to construct the dielectric tensor of the film, assuming the molecules to be lying flat with respect to the substrate and with a herringbone arrangement parallel to the substrate plane. Resonant soft X-ray reflectivity proved to be extremely sensitive to film thickness, down to the single molecular layer. The best agreement between simulation and experiment was found for a film of 1.6 nm, with flat laying configuration of the molecules. The high sensitivity to experimental geometries in terms of beam incidence and light polarization was also clarified through simulations. The optical anisotropies of the organic film were experimentally determined and through the comparison with calculations, it was possible to relate them to the orbital symmetry of the empty electronic states.

Beam splitter phase shifts: Wave optics approach

Science.gov (United States)

Agnesi, Antonio; Degiorgio, Vittorio

2017-10-01

We investigate the phase relationships between transmitted and reflected waves in a lossless beam splitter having a multilayer structure, using the matrix approach as outlined in classical optics books. Contrarily to the case of the quantum optics formalism generally employed to describe beam splitters, these matrices are not unitary. In this note we point out the existence of general relations among the elements of the transfer matrix that describes the multilayer beam splitter. Such relations, which are independent of the detailed structure of the beam splitter, fix the phase shifts between reflected and transmitted waves. It is instructive to see how the results obtained by Zeilinger by using spinor algebra and Pauli matrices can be easily derived from our general relations.

Inactivation of Bacillus atrophaeus and of Aspergillus niger using beams of argon ions, of oxygen molecules and of oxygen atoms

Energy Technology Data Exchange (ETDEWEB)

Raballand, V; Benedikt, J; Keudell, A von [Research Group Reactive Plasmas, Ruhr-Universitaet Bochum, 44780 Bochum (Germany); Wunderlich, J [Fraunhofer Institut for Process Engineering and Packaging, Giggenhauser Strasse 35, 85354 Freising (Germany)], E-mail: Achim.vonKeudell@rub.de

2008-06-07

The inactivation of spores of Bacillus atrophaeus and of Aspergillus niger using beams of argon ions, of oxygen molecules and of oxygen atoms is studied. Thereby, the conditions occurring in oxygen containing low pressure plasmas are mimicked and fundamental inactivation mechanisms can be revealed. It is shown that the impact of O atoms has no effect on the viability of the spores and that no etching of the spore coat occurs up to an O atom fluence of 3.5 x 10{sup 19} cm{sup -2}. The impact of argon ions with an energy of 200 eV does not cause significant erosion for fluences up to 1.15 x 10{sup 18} cm{sup -2}. However, the combined impact of argon ions and oxygen molecules or atoms causes significant etching of the spores and significant inactivation. This is explained by the process of chemical sputtering, where an ion-induced defect at the surface of the spore reacts with either the incident bi-radical O{sub 2} or with an incident O atom. This leads to the formation of CO, CO{sub 2} and H{sub 2}O and thus to erosion.

A Resistive Wideband Space Beam Splitter

OpenAIRE

Mahesh, Nivedita; Subrahmanyan, Ravi; Shankar, N. Udaya; Raghunathan, Agaram

2014-01-01

We present the design, construction and measurements of the electromagnetic performance of a wideband space beam splitter. The beam splitter is designed to power divide the incident radiation into reflected and transmitted components for interferometer measurement of spectral features in the mean cosmic radio background. Analysis of a 2-element interferometer configuration with a vertical beam splitter between a pair of antennas leads to the requirement that the beam splitter be a resistive s...

Gradient metasurface for four-direction anomalous reflection in terahertz

Science.gov (United States)

Wang, Jiao; Jiang, Yannan

2018-06-01

In this paper, a four-direction anomalous reflection metasurface is proposed. The basic cells comprise of squares and circles, which are designed at various sizes and arranged in a super cell at regular spacing. Then, properly combining super cells molds a square phase gradient metasurface (PGM). It is mounted on an optical thickness gold mirror, which inhibits all light transmission. Markedly different from previously reported metasurfaces, the square PGM is characterized by four-direction reflection beams. It takes into consideration the normal incidence and the oblique incidence. For the normal incidence, that the degrees of the four reflection angles are identical is due to the x, - x, y and - y directional discontinuous phase gradients, and lies on the symmetric structure in the xoy plane, which is then revealed by the surface current distribution. Incident angles varying from -20° to 20°, the reflection angles are demonstrated in the oblique incidence. Moreover, the PGM is polarization-independent. The performance is attributed to the symmetry of structure, which is verified by Radar cross section. Simulated results prove that our method offers a simple and effective strategy for metasurface design in terahertz. The proposed PGM can aid in focused beams, steering beams, and shaped beams.

Real-time particle size analysis using focused beam reflectance measurement as a process analytical technology tool for a continuous granulation-drying-milling process.

Science.gov (United States)

Kumar, Vijay; Taylor, Michael K; Mehrotra, Amit; Stagner, William C

2013-06-01

Focused beam reflectance measurement (FBRM) was used as a process analytical technology tool to perform inline real-time particle size analysis of a proprietary granulation manufactured using a continuous twin-screw granulation-drying-milling process. A significant relationship between D20, D50, and D80 length-weighted chord length and sieve particle size was observed with a p value of 0.05).

Personal extrapolation of CDF test beam use to the SSC

International Nuclear Information System (INIS)

Nodulman, L.

1986-01-01

The author's personal experience in test beam usage at CDF is used to predict SSC needs at the point of turn-on. It is concluded that the test beam demand will reflect the scale of effort involved in SSC detectors rather than the total number of them. Provision for later expansion is recommended. It is also recommended that the test beam facilities, as well as detector electronics, should reflect the available dynamic range; particularly, a single high energy beam derived from the SSC could be shared by several groups

Personal extrapolation of CDF test beam use to the SSC

Energy Technology Data Exchange (ETDEWEB)

Nodulman, L.

1986-06-23

The author's personal experience in test beam usage at CDF is used to predict SSC needs at the point of turn-on. It is concluded that the test beam demand will reflect the scale of effort involved in SSC detectors rather than the total number of them. Provision for later expansion is recommended. It is also recommended that the test beam facilities, as well as detector electronics, should reflect the available dynamic range; particularly, a single high energy beam derived from the SSC could be shared by several groups. (LEW)

SISGR: Room Temperature Single-Molecule Detection and Imaging by Stimulated Emission Microscopy

Energy Technology Data Exchange (ETDEWEB)

Xie, Xiaoliang Sunney [Harvard Univ., Cambridge, MA (United States). Dept. of Chemistry and Chemical Biology

2017-03-13

Single-molecule spectroscopy has made considerable impact on many disciplines including chemistry, physics, and biology. To date, most single-molecule spectroscopy work is accomplished by detecting fluorescence. On the other hand, many naturally occurring chromophores, such as retinal, hemoglobin and cytochromes, do not have detectable fluorescence. There is an emerging need for single-molecule spectroscopy techniques that do not require fluorescence. In the last proposal period, we have successfully demonstrated stimulated emission microscopy, single molecule absorption, and stimulated Raman microscopy based on a high-frequency modulation transfer technique. These first-of-a- kind new spectroscopy/microscopy methods tremendously improved our ability to observe molecules that fluorescence weakly, even to the limit of single molecule detection for absorption measurement. All of these methods employ two laser beams: one (pump beam) excites a single molecule to a real or virtual excited state, and the other (probe beam) monitors the absorption/emission property of the single. We extract the intensity change of the probe beam with high sensitivity by implementing a high-frequency phase-sensitive detection scheme, which offers orders of magnitude improvement in detection sensitivity over direct absorption/emission measurement. However, single molecule detection based on fluorescence or absorption is fundamentally limited due to their broad spectral response. It is important to explore other avenues in single molecule detection and imaging which provides higher molecular specificity for studying a wide variety of heterogeneous chemical and biological systems. This proposal aimed to achieve single-molecule detection sensitivity with near resonance stimulated Raman scattering (SRS) microscopy. SRS microscopy was developed in our lab as a powerful technique for imaging heterogeneous samples based on their intrinsic vibrational contrasts, which provides much higher molecular

Nonlinear wave beams in a piezo semiconducting layer

International Nuclear Information System (INIS)

Bagdoev, A.G.; Shekoyan, A.V.; Danoyan, Z.N.

1997-01-01

The propagation of quasi-monochromatic nonlinear wave in a piezo semiconducting layer taking into account electron-concentration nonlinearity is considered. For such medium the evolution equations for incoming and reflected waves are derived. Nonlinear Schroedinger equations and solutions for narrow beams are obtained. It is shown that symmetry of incoming and reflected waves does not take place. The focusing of beams is investigated.18 refs

Long range heliostat target using array of normal incidence pyranometers to evaluate a beam of solar radiation

Science.gov (United States)

Ghanbari, Cheryl M; Ho, Clifford K; Kolb, Gregory J

2014-03-04

Various technologies described herein pertain to evaluating a beam reflected by a heliostat. A portable target that has an array of sensors mounted thereupon is configured to capture the beam reflected by the heliostat. The sensors in the array output measured values indicative of a characteristic of the beam reflected by the heliostat. Moreover, a computing device can generate and output data corresponding to the beam reflected by the heliostat based on the measured values indicative of the characteristic of the beam received from the sensors in the array.

Kinetics of physical adsorption of ethane on Ir(110)-(1×2): Molecular beam reflectivity measurements and Monte Carlo simulations

OpenAIRE

Kang, H. C.; Mullins, C. B.; Weinberg, W. H.

1990-01-01

Experimental results, obtained using a reflectivity method, for the probability of physical adsorption of ethane on the Ir(110)-(1×2) surface are presented. We analyze these results using Monte Carlo simulations and show that physical adsorption can occur either directly or through a precursor state in which an ethane molecule is trapped in a second layer above a first layer of physically adsorbed ethane. From the Monte Carlo simulations, we are able to establish that the energy barrier for d...

BEAM web server: a tool for structural RNA motif discovery.

Science.gov (United States)

Pietrosanto, Marco; Adinolfi, Marta; Casula, Riccardo; Ausiello, Gabriele; Ferrè, Fabrizio; Helmer-Citterich, Manuela

2018-03-15

RNA structural motif finding is a relevant problem that becomes computationally hard when working on high-throughput data (e.g. eCLIP, PAR-CLIP), often represented by thousands of RNA molecules. Currently, the BEAM server is the only web tool capable to handle tens of thousands of RNA in input with a motif discovery procedure that is only limited by the current secondary structure prediction accuracies. The recently developed method BEAM (BEAr Motifs finder) can analyze tens of thousands of RNA molecules and identify RNA secondary structure motifs associated to a measure of their statistical significance. BEAM is extremely fast thanks to the BEAR encoding that transforms each RNA secondary structure in a string of characters. BEAM also exploits the evolutionary knowledge contained in a substitution matrix of secondary structure elements, extracted from the RFAM database of families of homologous RNAs. The BEAM web server has been designed to streamline data pre-processing by automatically handling folding and encoding of RNA sequences, giving users a choice for the preferred folding program. The server provides an intuitive and informative results page with the list of secondary structure motifs identified, the logo of each motif, its significance, graphic representation and information about its position in the RNA molecules sharing it. The web server is freely available at http://beam.uniroma2.it/ and it is implemented in NodeJS and Python with all major browsers supported. marco.pietrosanto@uniroma2.it. Supplementary data are available at Bioinformatics online.

Simulations of longitudinal beam dynamics of space-charge dominated beams for heavy ion fusion

International Nuclear Information System (INIS)

Miller, D.A.C.

1994-12-01

The longitudinal instability has potentially disastrous effects on the ion beams used for heavy ion driven inertial confinement fusion. This instability is a open-quotes resistive wallclose quotes instability with the impedance coining from the induction modules in the accelerator used as a driver. This instability can greatly amplify perturbations launched from the beam head and can prevent focusing of the beam onto the small spot necessary for fusion. This instability has been studied using the WARPrz particle-in-cell code. WARPrz is a 2 1/2 dimensional electrostatic axisymmetric code. This code includes a model for the impedance of the induction modules. Simulations with resistances similar to that expected in a driver show moderate amounts of growth from the instability as a perturbation travels from beam head to tail as predicted by cold beam fluid theory. The perturbation reflects off the beam tail and decays as it travels toward the beam head. Nonlinear effects cause the perturbation to steepen during reflection. Including the capacitive component of the, module impedance. has a partially stabilizing effect on the longitudinal instability. This reduction in the growth rate is seen in both cold beam fluid theory and in simulations with WARPrz. Instability growth rates for warm beams measured from WARPrz are lower than cold beam fluid theory predicts. Longitudinal thermal spread cannot account for this decrease in the growth rate. A mechanism for coupling the transverse thermal spread to decay of the longitudinal waves is presented. The longitudinal instability is no longer a threat to the heavy ion fusion program. The simulations in this thesis have shown that the growth rate for this instability will not be as large as earlier calculations predicted

Reactions of modulated molecular beams with pyrolytic graphite IV. Water vapor

International Nuclear Information System (INIS)

Olander, D.R.; Acharya, T.R.; Ullman, A.Z.

1977-01-01

The reaction of water vapor with the prism plane face of anneal pyrolytic graphite was investigated by modulated molecular beam--mass spectrometry methods. The equivalent water vapor pressure of the beam was approx.2 x 10 -5 Torr and the graphite temperature was varied from 300 to 2500 0 K. The mechanism was deduced from three types of experiments: isotope exchange utilizing modulated H 2 O and steady D 2 O beams; measurements of the phase difference between H 2 O and neon reflected from the surface from a mixed primary beam of these species; and reaction of a modulated H 2 O beam to produce CO and H 2 . Based upon the isotope exchange experiments chemisorption of water on graphite was found to be dissociative and reversible. Incident water molecules chemisorbed with a sticking probability of 0.15 +- 0.02 to form the complexes C--OH and C--H. Recombination of the surface complexes reverses the adsorption step and is responsible for the isotope exchange properties of the graphite surface. This process is unactivated. Reaction to produce CO and H 2 also results from collisions of the primary surface complexes, but this step has an activation energy of 170 kJ/mole. This reaction yields bound complexes tentatively identified as C--O and H--C--H, which then decompose to produce the stable reaction products. All of the above steps exhibit characteristic times on the order of milliseconds, and are therefore detectable by the modulated beam method. All surface intermediates are strongly affected by solution and diffusion in the bulk of the solid

Change in spatial coherence of light on refraction and on reflection.

Science.gov (United States)

Lahiri, Mayukh; Wolf, Emil

2013-06-01

A theory of refraction and reflection of partially coherent electromagnetic beams has been recently developed. In this paper, we apply it to study the change in spatial coherence caused by refraction and by reflection more fully. By considering a Gaussian Schell-model beam, we show that the change is, in general, dependent on the angle of incidence.

Laser-Bioplasma Interaction: The Blood Type Transmutation Induced by Multiple Ultrashort Wavelength Laser Beams

Science.gov (United States)

Stefan, V. Alexander

2015-11-01

The interaction of ultrashort wavelength multi laser beams with the flowing blood thin films leads to the transmutation of the blood types A, B, and AB into O type. This is a novel mechanism of importance for the transfusion medicine. Laser radiation is in resonance with the eigen-frequency modes of the antigen proteins and forces the proteins to parametrically oscillate until they get kicked out from the surface. The stripping away of antigens is done by the scanning-multiple-lasers of a high repetition rate in the blue-purple frequency domain. The guiding-lasers are in the red-green frequency domain. The laser force, (parametric interaction with the antigen eigen-oscillation), upon the antigen protein molecule must exceed its weight. The scanning laser beam is partially reflected as long as the antigen(s) is not eliminated. The process of the protein detachment can last a few minutes. Supported by Nikola Tesla Labs., Stefan University.

Laser Beam Focus Analyser

DEFF Research Database (Denmark)

Nielsen, Peter Carøe; Hansen, Hans Nørgaard; Olsen, Flemming Ove

2007-01-01

the obtainable features in direct laser machining as well as heat affected zones in welding processes. This paper describes the development of a measuring unit capable of analysing beam shape and diameter of lasers to be used in manufacturing processes. The analyser is based on the principle of a rotating......The quantitative and qualitative description of laser beam characteristics is important for process implementation and optimisation. In particular, a need for quantitative characterisation of beam diameter was identified when using fibre lasers for micro manufacturing. Here the beam diameter limits...... mechanical wire being swept through the laser beam at varying Z-heights. The reflected signal is analysed and the resulting beam profile determined. The development comprised the design of a flexible fixture capable of providing both rotation and Z-axis movement, control software including data capture...

Diagnostic studies of ion beam formation in inductively coupled plasma

Energy Technology Data Exchange (ETDEWEB)

Jacobs, Jenee L. [Iowa State Univ., Ames, IA (United States)

2015-01-01

This dissertation describes a variety of studies focused on the plasma and the ion beam in inductively coupled plasma mass spectrometry (ICP-MS). The ability to use ICP-MS for measurements of trace elements in samples requires the analytes to be efficiently ionized. Updated ionization efficiency tables are discussed for ionization temperatures of 6500 K and 7000 K with an electron density of 1 x 10¹⁵ cm^-3. These values are reflective of the current operating parameters of ICP-MS instruments. Calculations are also discussed for doubly charged (M²⁺) ion formation, neutral metal oxide (MO) ionization, and metal oxide (MO⁺) ion dissociation for similar plasma temperature values. Ionization efficiency results for neutral MO molecules in the ICP have not been reported previously.

Reflection of a polarized light cone

Science.gov (United States)

Brody, Jed; Weiss, Daniel; Berland, Keith

2013-01-01

We introduce a visually appealing experimental demonstration of Fresnel reflection. In this simple optical experiment, a polarized light beam travels through a high numerical-aperture microscope objective, reflects off a glass slide, and travels back through the same objective lens. The return beam is sampled with a polarizing beam splitter and produces a surprising geometric pattern on an observation screen. Understanding the origin of this pattern requires careful attention to geometry and an understanding of the Fresnel coefficients for S and P polarized light. We demonstrate that in addition to a relatively simple experimental implementation, the shape of the observed pattern can be computed both analytically and by using optical modeling software. The experience of working through complex mathematical computations and demonstrating their agreement with a surprising experimental observation makes this a highly educational experiment for undergraduate optics or advanced-lab courses. It also provides a straightforward yet non-trivial system for teaching students how to use optical modeling software.

Slowing techniques for loading a magneto-optical trap of CaF molecules

Science.gov (United States)

Truppe, Stefan; Fitch, Noah; Williams, Hannah; Hambach, Moritz; Sauer, Ben; Hinds, Ed; Tarbutt, Mike

2016-05-01

Ultracold molecules in a magneto-optical trap (MOT) are useful for testing fundamental physics and studying strongly-interacting quantum systems. With experiments starting with a relatively fast (50-200 m/s) buffer-gas beam, a primary concern is decelerating molecules to below the MOT capture velocity, typically 10 m/s. Direct laser cooling, where the molecules are slowed via momentum transfer from a chirped counter-propagating narrowband laser, is a natural choice. However, chirping the cooling and repump lasers requires precise control of multiple laser frequencies simultaneously. Another approach, called ``white-light slowing'' uses a broadband laser such that all fast molecules in the beam are decelerated. By addressing numerous velocities no chirping is needed. Unfortunately, both techniques have significant losses as molecules are transversely heated during the optical cycling. Ideally, the slowing method would provide simultaneous deceleration and transverse guiding. A newly developed technique, called Zeeman-Sisyphus deceleration, is potentially capable of both. Using permanent magnets and optical pumping, the number of scattered photons is reduced, lessening transverse heating and relaxing the repump requirements. Here we compare all three options for CaF.

Biomaterial imaging with MeV-energy heavy ion beams

Energy Technology Data Exchange (ETDEWEB)

Seki, Toshio, E-mail: seki@sakura.nucleng.kyoto-u.ac.jp [Department of Nuclear Engineering, Kyoto Univ., Uji, Kyoto 611-0011 (Japan); CREST, Japan Science and Technology Agency (JST), Chiyoda, Tokyo 102-0075 (Japan); Wakamatsu, Yoshinobu; Nakagawa, Shunichiro [Department of Nuclear Engineering, Kyoto Univ., Uji, Kyoto 611-0011 (Japan); Aoki, Takaaki [Department of Electronic Science and Engineering, Kyoto Univ., Nishikyo, Kyoto 615-8510 (Japan); CREST, Japan Science and Technology Agency (JST), Chiyoda, Tokyo 102-0075 (Japan); Ishihara, Akihiko [Laboratory of Cell Biology and Life Science, Graduate School of Human and Environmental Studies, Kyoto Univ., Sakyo, Kyoto 606-8501 (Japan); Matsuo, Jiro [Quantum Science and Engineering Center, Kyoto Univ., Uji, Kyoto 611-0011 (Japan); CREST, Japan Science and Technology Agency (JST), Chiyoda, Tokyo 102-0075 (Japan)

2014-08-01

The spatial distribution of several chemical compounds in biological tissues and cells can be obtained with mass spectrometry imaging (MSI). In conventional secondary ion mass spectrometry (SIMS) with keV-energy ion beams, elastic collisions occur between projectiles and atoms of constituent molecules. The collisions produce fragments, making the acquisition of molecular information difficult. In contrast, ion beams with MeV-energy excite near-surface electrons and enhance the ionization of high-mass molecules; hence, SIMS spectra of fragment-suppressed ionized molecules can be obtained with MeV-SIMS. To compare between MeV and conventional SIMS, we used the two methods based on MeV and Bi{sub 3}-keV ions, respectively, to obtain molecular images of rat cerebellum. Conventional SIMS images of m/z 184 were clearly observed, but with the Bi{sub 3} ion, the distribution of the molecule with m/z 772.5 could be observed with much difficulty. This effect was attributed to the low secondary ion yields and we could not get many signal counts with keV-energy beam. On the other hand, intact molecular ion distributions of lipids were clearly observed with MeV-SIMS, although the mass of all lipid molecules was higher than 500 Da. The peaks of intact molecular ions in MeV-SIMS spectra allowed us to assign the mass. The high secondary ion sensitivity with MeV-energy heavy ions is very useful in biomaterial analysis.

Biomaterial imaging with MeV-energy heavy ion beams

International Nuclear Information System (INIS)

Seki, Toshio; Wakamatsu, Yoshinobu; Nakagawa, Shunichiro; Aoki, Takaaki; Ishihara, Akihiko; Matsuo, Jiro

2014-01-01

The spatial distribution of several chemical compounds in biological tissues and cells can be obtained with mass spectrometry imaging (MSI). In conventional secondary ion mass spectrometry (SIMS) with keV-energy ion beams, elastic collisions occur between projectiles and atoms of constituent molecules. The collisions produce fragments, making the acquisition of molecular information difficult. In contrast, ion beams with MeV-energy excite near-surface electrons and enhance the ionization of high-mass molecules; hence, SIMS spectra of fragment-suppressed ionized molecules can be obtained with MeV-SIMS. To compare between MeV and conventional SIMS, we used the two methods based on MeV and Bi 3 -keV ions, respectively, to obtain molecular images of rat cerebellum. Conventional SIMS images of m/z 184 were clearly observed, but with the Bi 3 ion, the distribution of the molecule with m/z 772.5 could be observed with much difficulty. This effect was attributed to the low secondary ion yields and we could not get many signal counts with keV-energy beam. On the other hand, intact molecular ion distributions of lipids were clearly observed with MeV-SIMS, although the mass of all lipid molecules was higher than 500 Da. The peaks of intact molecular ions in MeV-SIMS spectra allowed us to assign the mass. The high secondary ion sensitivity with MeV-energy heavy ions is very useful in biomaterial analysis

Strong-field ionization of linear molecules by a bicircular laser field: Symmetry considerations

Science.gov (United States)

Gazibegović-Busuladžić, A.; Busuladžić, M.; Hasović, E.; Becker, W.; Milošević, D. B.

2018-04-01

Using the improved molecular strong-field approximation, we investigate (high-order) above-threshold ionization [(H)ATI] of various linear polyatomic molecules by a two-color laser field of frequencies r ω and s ω (with integer numbers r and s ) having coplanar counter-rotating circularly polarized components (a so-called bicircular field). Reflection and rotational symmetries for molecules aligned in the laser-field polarization plane, analyzed for diatomic homonuclear molecules in Phys. Rev. A 95, 033411 (2017), 10.1103/PhysRevA.95.033411, are now considered for diatomic heteronuclear molecules and symmetric and asymmetric linear triatomic molecules. There are additional rotational symmetries for (H)ATI spectra of symmetric linear molecules compared to (H)ATI spectra of the asymmetric ones. It is shown that these symmetries manifest themselves differently for r +s odd and r +s even. For example, HATI spectra for symmetric molecules with r +s even obey inversion symmetry. For ATI spectra of linear molecules, reflection symmetry appears only for certain molecular orientation angles ±90∘-j r 180∘/(r +s ) (j integer). For symmetric linear molecules, reflection symmetry appears also for the angles -j r 180∘/(r +s ) . For perpendicular orientation of molecules with respect to the laser-field polarization plane, the HATI spectra are very similar to those of the atomic targets, i.e., both spectra are characterized by the same type of the (r +s )-fold symmetry.

Electron-beam curing of epoxy resins: effect of alcohols on cationic ...

Indian Academy of Sciences (India)

Unknown

Electron-beam (e-beam) induced polymerization of epoxy resins proceeds via cationic mechanism in presence of suitable ... generate ionic species, free radicals, and/or molecules in .... bisphenol A) and the effect of presence of different OH.

Low energy cross section data for ion-molecule reactions in hydrogen systems and for charge transfer of multiply charged ions with atoms and molecules

International Nuclear Information System (INIS)

Okuno, Kazuhiko

2007-04-01

Systematic cross section measurements for ion-molecule reactions in hydrogen systems and for charge transfer of multiply charged ions in low energy collisions with atoms and molecules have been performed continuously by the identical apparatus installed with an octo-pole ion beam guide (OPIG) since 1980 till 2004. Recently, all of accumulated cross section data for a hundred collision systems has been entered into CMOL and CHART of the NIFS atomic and molecular numerical database together with some related cross section data. In this present paper, complicated ion-molecule reactions in hydrogen systems are revealed and the brief outlines of specific properties in low energy charge transfer collisions of multiply charged ions with atoms and molecules are introduced. (author)

Neutral-particle-beam production and injection

International Nuclear Information System (INIS)

Post, D.; Pyle, R.

1982-07-01

This paper is divided into two sections: the first is a discussion of the interactions of neutral beams with confined plasmas, the second is concerned with the production and diagnosis of the neutral beams. In general we are dealing with atoms, molecules, and ions of the isotopes of hydrogen, but some heavier elements (for example, oxygen) will be mentioned. The emphasis will be on single-particle collisions; selected atomic processes on surfaces will be included

First spatial separation of a heavy ion isomeric beam with a multiple-reflection time-of-flight mass spectrometer

Science.gov (United States)

Dickel, T.; Plaß, W. R.; Ayet San Andres, S.; Ebert, J.; Geissel, H.; Haettner, E.; Hornung, C.; Miskun, I.; Pietri, S.; Purushothaman, S.; Reiter, M. P.; Rink, A.-K.; Scheidenberger, C.; Weick, H.; Dendooven, P.; Diwisch, M.; Greiner, F.; Heiße, F.; Knöbel, R.; Lippert, W.; Moore, I. D.; Pohjalainen, I.; Prochazka, A.; Ranjan, M.; Takechi, M.; Winfield, J. S.; Xu, X.

2015-05-01

211Po ions in the ground and isomeric states were produced via 238U projectile fragmentation at 1000 MeV/u. The 211Po ions were spatially separated in flight from the primary beam and other reaction products by the fragment separator FRS. The ions were energy-bunched, slowed-down and thermalized in a gas-filled cryogenic stopping cell (CSC). They were then extracted from the CSC and injected into a high-resolution multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS). The excitation energy of the isomer and, for the first time, the isomeric-to-ground state ratio were determined from the measured mass spectrum. In the subsequent experimental step, the isomers were spatially separated from the ions in the ground state by an ion deflector and finally collected with a silicon detector for decay spectroscopy. This pioneering experimental result opens up unique perspectives for isomer-resolved studies. With this versatile experimental method new isomers with half-lives longer than a few milliseconds can be discovered and their decay properties can be measured with highest sensitivity and selectivity. These experiments can be extended to studies with isomeric beams in nuclear reactions.

STICKING OF MOLECULES ON NONPOROUS AMORPHOUS WATER ICE

Energy Technology Data Exchange (ETDEWEB)

He, Jiao; Vidali, Gianfranco [Physics Department, Syracuse University, Syracuse, NY 13244 (United States); Acharyya, Kinsuk, E-mail: gvidali@syr.edu [Department of Chemistry, University of Virginia, Charlottesville, VA 22904 (United States)

2016-05-20

Accurate modeling of physical and chemical processes in the interstellar medium (ISM) requires detailed knowledge of how atoms and molecules adsorb on dust grains. However, the sticking coefficient, a number between 0 and 1 that measures the first step in the interaction of a particle with a surface, is usually assumed in simulations of ISM environments to be either 0.5 or 1. Here we report on the determination of the sticking coefficient of H{sub 2}, D{sub 2}, N{sub 2}, O{sub 2}, CO, CH{sub 4}, and CO{sub 2} on nonporous amorphous solid water. The sticking coefficient was measured over a wide range of surface temperatures using a highly collimated molecular beam. We showed that the standard way of measuring the sticking coefficient—the King–Wells method—leads to the underestimation of trapping events in which there is incomplete energy accommodation of the molecule on the surface. Surface scattering experiments with the use of a pulsed molecular beam are used instead to measure the sticking coefficient. Based on the values of the measured sticking coefficient, we suggest a useful general formula of the sticking coefficient as a function of grain temperature and molecule-surface binding energy. We use this formula in a simulation of ISM gas–grain chemistry to find the effect of sticking on the abundance of key molecules both on grains and in the gas phase.

Convergent beam thickness determination of thin foil zirconium specimens

International Nuclear Information System (INIS)

Cann, C.D.

1978-07-01

The use of convergent beam patterns to determine the thickness of zirconium foils observed in the electron microscope has been investigated both theoretically and experimentally. On the basis of many-beam dynamical theory calculations, the [1012], [1013], and [1120] reflections at an accelerating voltage of 100 kV and the [1013], [1120], and [1122] reflections at 200 kV were found most suitable for convergent beam thickness determinations. Experimental convergent beam patterns were obtained in the JEOL-200B electron microscope under two different sets of conditions based on the size of the pattern desired. Computer assisted analysis of the patterns obtained gave foil thicknesses in good agreement with those determined from thickness extinction contours. (author)

Second-order temporal interference of two independent light beams at an asymmetrical beam splitter

International Nuclear Information System (INIS)

Liu Jianbin; Wang Jingjing; Xu Zhuo

2017-01-01

The second-order temporal interference of classical and nonclassical light at an asymmetrical beam splitter is discussed based on two-photon interference in Feynman’s path integral theory. The visibility of the second-order interference pattern is determined by the properties of the superposed light beams, the ratio between the intensities of these two light beams, and the reflectivity of the asymmetrical beam splitter. Some requirements about the asymmetrical beam splitter have to be satisfied in order to ensure that the visibility of the second-order interference pattern of nonclassical light beams exceeds the classical limit. The visibility of the second-order interference pattern of photons emitted by two independent single-photon sources is independent of the ratio between the intensities. These conclusions are important for the researches and applications in quantum optics and quantum information when an asymmetrical beam splitter is employed. (paper)

A new crossed molecular beam apparatus using time-sliced ion velocity imaging technique

International Nuclear Information System (INIS)

Wu Guorong; Zhang Weiqing; Pan Huilin; Shuai Quan; Jiang Bo; Dai Dongxu; Yang Xueming

2008-01-01

A new crossed molecular beam apparatus has been constructed for investigating polyatomic chemical reactions using the time-sliced ion velocity map imaging technique. A unique design is adopted for one of the two beam sources and allows us to set up the molecular beam source either horizontally or vertically. This can be conveniently used to produce versatile atomic or radical beams from photodissociation and as well as electric discharge. Intensive H-atom beam source with high speed ratio was produced by photodissociation of the HI molecule and was reacted with the CD 4 molecule. Vibrational-state resolved HD product distribution was measured by detecting the CD 3 product. Preliminary results were also reported on the F+SiH 4 reaction using the discharged F atom beam. These results demonstrate that this new instrument is a powerful tool for investigating chemical dynamics of polyatomic reactions.

STATUS REPORT ON DEVELOPMENT OF A HIGH-SPEED HIGH-INTENSITY MOLECULAR BEAM

Energy Technology Data Exchange (ETDEWEB)

Knuth, Eldon L.

1963-07-15

Status of a high-speed high-intensity molecular beam under development is described. Bases for designs of the several components are presented. Using an arc-heated source and a hypersonic jet, molecular energies exceeding 1 ev and beam intensities of the order of 10/sup 16/ molecules/ cm/sup 2/ sec are anticipated. A two-disk beam chopper and speed selector provides a means for analyzing the speed distribution in the generated beam, for chopping the beam into bursts of nearly monoenergetic molecules suitable for scattering studies using the time-of-flight technique, and for modulating the beam in order to facilitate detection. A through-flow ionization detector possesses the versatility required for scattering studies using the time-of-flight technique. A sorption pump and a turbo pump serve as central components of alternative pumping systems for the collimating chamber. Using the arc-heated source, the converging nozzle, the conduction-radiation-cooled skimmer, the turbo pump (turning at 3400 rpm), the chopperselector (acting only as a chopper), and the detector, an arc-heated beam is generated and detected. (auth)

Beam-induced pressure variations in a TFTR neutral-beam injector

International Nuclear Information System (INIS)

Willis, J.E.; Berkner, K.H.

1981-10-01

In neutral-beam injection systems either all or part of the gas flow into the neutralizer comes from the plasma source. When the beam is switched on, ions from the plasma source, which used to contribute to the gas flow, are converted to an energetic beam and are pumped away: hence reducing the gas input to the neutralizer. The large volume of the neutralizer and its high conductance damp out rapid changes; for example, when the gas to the source is first turned on, there is a 230 msec exponential rise time associated with pressure in the neutralizer. The neutralizer in turn acts as a source of gas to the first chamber and the first chamber to the second and so on. Beam dumps become additional sources of gas in the second chamber and target tank as gas molecules are collisionally desorbed from the surface of the dump. A simple analytical model (the equivalent of an electrical RC circuit) of the volumes and conductances of the system has been used to describe the pressure variations. The use of time dependent sources terms in the model gives an estimate of the desorption rate from the dumps and its time variation during a beam pulse

Development of a radioactive ion beam test stand at LBNL

International Nuclear Information System (INIS)

Burke, J.; Freedman, S.J.; Fujikawa, B.; Gough, R.A.; Lyneis, C.M.; Vetter, P.; Wutte, D.; Xie, Z.Q.

1998-01-01

For the on-line production of a 14 O + ion beam, an integrated target--transfer line ion source system is now under development at LBNL. 14 O is produced in the form of CO in a high temperature carbon target using a 20 MeV 3 He beam from the LBNL 88'' Cyclotron via the reaction 12 C( 3 He,n) 14 O. The neutral radioactive CO molecules diffuse through an 8 m room temperature stainless steel line from the target chamber into a cusp ion source. The molecules are dissociated, ionized and extracted at energies of 20 to 30 keV and mass separated with a double focusing bending magnet. The different components of the setup are described. The release and transport efficiency for the CO molecules from the target through the transfer line was measured for various target temperatures. The ion beam transport efficiencies and the off-line ion source efficiencies for Ar, O 2 and CO are presented. Ionization efficiencies of 28% for Ar + , 1% for CO, 0.7% for O + , 0.33 for C + have been measured

Effect of end reflections on conversion efficiency of coaxial relativistic backward wave oscillator

Energy Technology Data Exchange (ETDEWEB)

Teng, Yan; Chen, Changhua; Sun, Jun; Shi, Yanchao; Ye, Hu; Wu, Ping; Li, Shuang; Xiong, Xiaolong [Science and Technology on High Power Microwave Laboratory, Northwest Institute of Nuclear Technology, Xi' an 710024 (China)

2015-11-07

This paper theoretically investigates the effect of end reflections on the operation of the coaxial relativistic backward wave oscillator (CRBWO). It is found that the considerable enhancement of the end reflection at one end increases the conversion efficiency, but excessively large end reflections at both ends weaken the asynchronous wave-beam interaction and thus reduce the conversion efficiency. Perfect reflection at the post end significantly improves the interaction between the electron beam and the asynchronous harmonic so that the conversion efficiency is notably increased. Based on the theoretical research, the diffraction-CRBWO with the generated microwave diffracted and output through the front end of the coaxial slow wave structure cavity is proposed. The post end is conductively closed to provide the perfect reflection. This promotes the amplitude and uniformity of the longitudinal electric field on the beam transmission line and improves the asynchronous wave-beam interaction. In numerical simulations under the diode voltage and current of 450 kV and 5.84 kA, microwave generation with the power of 1.45 GW and the conversion efficiency of 55% are obtained at the frequency of 7.45 GHz.

Developments in non-destructive beam diagnostics

International Nuclear Information System (INIS)

Fraser, J.S.

1981-01-01

With the large average beam currents being achieved in accelerators and storage rings, there is an increasing need for non-destructive beam diagnostic devices. For continuous beams, position monitors of the capacitive pick-up type are replaced by resonant devices that respond to the transverse displacement of the beam centroid. Bunch length monitors of the SLAC type using resonant cavities operating in the TM 010 mode can be used for continuous beams. The more detailed information derivable from beam profile scanners requires development of improved non-destructive devices. Profile monitors which scan the visible light produced by high current beams may be more reliable than ones using the residual ionization if the light intensity from gas molecules following nonionizing collisions with beam particles gives a measure of the beam current density independent of the local electron density. The intense Balmer series lines from neutral hydrogen beams have been used successfully to measure beam profiles. At CRNL and at LASL, beam light profile monitors are being developed for high average current accelerators. Three or more projections will be recorded to allow tomographic reconstruction of the two-dimensional beam current density. Light detection is either by intensified Reticons or ISIT vidicons. The use of three or more beam light monitors on a beam transport line will also permit estimates of the transverse emittance to be made through the reconstruction technique

Electro-optic polymeric reflection modulator based on plasmonic metamaterial

Science.gov (United States)

Abbas, A.; Swillam, M.

2018-02-01

A novel low power design for polymeric Electro-Optic reflection modulator is proposed based on the Extraordinary Reflection of light from multilayer structure consisting of a plasmonic metasurface with a periodic structure of sub wavelength circular apertures in a gold film above a thin layer of EO polymer and above another thin gold layer. The interference of the different reflected beams from different layer construct the modulated beam, The applied input driving voltage change the polymer refractive index which in turn determine whether the interference is constructive or destructive, so both phase and intensity modulation could be achieved. The resonant wavelength is tuned to the standard telecommunication wavelength 1.55μm, at this wavelength the reflection is minimum, while the absorption is maximum due to plasmonic resonance (PR) and the coupling between the incident light and the plasmonic metasurface.

Laser diagnostics for picosecond e-beams

International Nuclear Information System (INIS)

Pogorelsky, I.; Ben-Zvi, I.

1992-01-01

We propose a novel approach to picosecond e-bunch/laser pulse synchronization and spatial alignment based upon refraction and reflection of a laser beam on a plasma column created by relativistic electrons traveling through a gas or solid optical material. The technique may be used in laser accelerators and for general subpicosecond e-beam diagnostics

Laser Cooled YbF Molecules for Measuring the Electron's Electric Dipole Moment

Science.gov (United States)

Lim, J.; Almond, J. R.; Trigatzis, M. A.; Devlin, J. A.; Fitch, N. J.; Sauer, B. E.; Tarbutt, M. R.; Hinds, E. A.

2018-03-01

We demonstrate one-dimensional sub-Doppler laser cooling of a beam of YbF molecules to 100 μ K . This is a key step towards a measurement of the electron's electric dipole moment using ultracold molecules. We compare the effectiveness of magnetically assisted and polarization-gradient sub-Doppler cooling mechanisms. We model the experiment and find good agreement with our data.

An Improved Measurement Method for the Strength of Radiation of Reflective Beam in an Industrial Optical Sensor Based on Laser Displacement Meter

OpenAIRE

Youngchul Bae

2016-01-01

An optical sensor such as a laser range finder (LRF) or laser displacement meter (LDM) uses reflected and returned laser beam from a target. The optical sensor has been mainly used to measure the distance between a launch position and the target. However, optical sensor based LRF and LDM have numerous and various errors such as statistical errors, drift errors, cyclic errors, alignment errors and slope errors. Among these errors, an alignment error that contains measurement error for the stre...

Ionization and ions pair formation in He(n1P) thermal collisions in the Rydberg + molecules low states

International Nuclear Information System (INIS)

Pesnelle, A.; Ronge, C.; Perdrix, M.; Watel, G.

1988-06-01

The application limits of the free electron model are tested. Experiments on polar molecules and on molecules of high electronical affinity are effectuated. The experiments are carried out in a three crossed beam geometry: a He(2 1S , 2 3S ) metastable atom beam, a continuous and monomode laser UV beam (316 nm), and a gas target beam. The main results are: high cross sections are observed on NH3, SO2 and C3H6O; the σ''exp'' behavior, as a function of v r , is v r -2 ; a monotone σ''exp'' (v r ) behavior is observed for SF6 and NO2. The experimental data can not be justified by means of the free electron model [fr

Photoionization studies with molecular beams

International Nuclear Information System (INIS)

Ng, C.Y.

1976-09-01

A molecular beam photoionization apparatus which combines the advantages of both the molecular beam method with photoionization mass spectrometry has been designed and constructed for carrying out some unique photoionization experiments. Rotational cooling during the supersonic expansion has resulted in high resolution photoionization efficiency curves for NO, ICl, C 2 H 2 and CH 3 I. The analysis of these spectra has yielded ionization potentials for these molecules to an accuracy of +- 3 MeV. Detailed autoionization structures were also resolved. This allows the investigation of the selection rules for autoionization, and the identification of the Rydberg series which converge to the excited states of the molecular ions. The degree of relaxation for thermally populated excited states has been examined using NO and ICl as examples. As a result of adiabatic cooling, a small percentage of dimers is also formed during the expansion. The photoionization efficiency curves for (NO) 2 , ArICl, Ar 2 , Kr 2 and Xe 2 have been obtained near the thresholds. Using the known dissociation energies of the (NO) 2 , Ar 2 , Kr 2 and Xe 2 van der Waals molecules, the corresponding dissociation energies for NO-NO + , Ar 2 + , Kr 2 + , and Xe 2 + have been determined. The ionization mechanisms for this class of molecules are examined and discussed

Optically stimulated slowing of polar heavy-atom molecules with a constant beat phase

Science.gov (United States)

Yin, Yanning; Xu, Supeng; Xia, Meng; Xia, Yong; Yin, Jianping

2018-04-01

Polar heavy-atom molecules have been well recognized as promising candidates for precision measurements and tests of fundamental physics. A much slower molecular beam to increase the interaction time should lead to a more sensitive measurement. Here we theoretically demonstrate the possibility of the stimulated longitudinal slowing of heavy-atom molecules by the coherent optical bichromatic force with a constant beat phase. Taking the YbF meolecule as an example, we show that a rapid and short-distance deceleration of heavy molecules by a phase-compensation method is feasible with moderate conditions. A molecular beam of YbF with a forward velocity of 120 m/s can be decelerated below 10 m/s within a distance of 3.5 cm and with a laser irradiance for each traveling wave of 107.2 W/cm 2 . Our proposed slowing method could be a promising approach to break through the space constraint or the limited capture efficiency of molecules loadable into a magneto-optical trap in traditional deceleration schemes, opening the possibility for a significant improvement of the precision measurement sensitivity.

High-resolution, high-throughput, positive-tone patterning of poly(ethylene glycol by helium beam exposure through stencil masks.

Directory of Open Access Journals (Sweden)

Eliedonna E Cacao

Full Text Available In this work, a collimated helium beam was used to activate a thiol-poly(ethylene glycol (SH-PEG monolayer on gold to selectively capture proteins in the exposed regions. Protein patterns were formed at high throughput by exposing a stencil mask placed in proximity to the PEG-coated surface to a broad beam of helium particles, followed by incubation in a protein solution. Attenuated Total Reflectance-Fourier Transform Infrared Spectroscopy (ATR-FTIR spectra showed that SH-PEG molecules remain attached to gold after exposure to beam doses of 1.5-60 µC/cm(2 and incubation in PBS buffer for one hour, as evidenced by the presence of characteristic ether and methoxy peaks at 1120 cm(-1 and 2870 cm(-1, respectively. X-ray Photoelectron Spectroscopy (XPS spectra showed that increasing beam doses destroy ether (C-O bonds in PEG molecules as evidenced by the decrease in carbon C1s peak at 286.6 eV and increased alkyl (C-C signal at 284.6 eV. XPS spectra also demonstrated protein capture on beam-exposed PEG regions through the appearance of a nitrogen N1s peak at 400 eV and carbon C1s peak at 288 eV binding energies, while the unexposed PEG areas remained protein-free. The characteristic activities of avidin and horseradish peroxidase were preserved after attachment on beam-exposed regions. Protein patterns created using a 35 µm mesh mask were visualized by localized formation of insoluble diformazan precipitates by alkaline phosphatase conversion of its substrate bromochloroindoyl phosphate-nitroblue tetrazolium (BCIP-NBT and by avidin binding of biotinylated antibodies conjugated on 100 nm gold nanoparticles (AuNP. Patterns created using a mask with smaller 300 nm openings were detected by specific binding of 40 nm AuNP probes and by localized HRP-mediated deposition of silver nanoparticles. Corresponding BSA-passivated negative controls showed very few bound AuNP probes and little to no enzymatic formation of diformazan precipitates or silver

Molecule scattering from insulator and metal surfaces

International Nuclear Information System (INIS)

Moroz, Iryna; Ambaye, Hailemariam; Manson, J R

2004-01-01

Calculations are carried out and compared with data for the scattering of CH 4 molecules from a LiF(001) surface and for O 2 scattering from Al(111). The theory is a mixed classical-quantum formalism that includes energy and momentum transfers between the surface and projectile for translational and rotational motions as well as internal mode excitation of the projectile molecule. The translational and rotational degrees of freedom couple most strongly to multiphonon excitations of the surface and are treated with classical dynamics. Internal vibrational excitations of the molecules are treated with a semiclassical formalism with extension to arbitrary numbers of modes and arbitrary quantum numbers. Calculations show good agreement for the dependence on incident translational energy, incident beam angle and surface temperature when compared with data for energy-resolved intensity spectra and angular distributions

Neutron beams. Tracks analysis, imaging and medicine

International Nuclear Information System (INIS)

Pepy, G.

2006-01-01

Thermal neutron beams can supply informations about the arrangement of atoms and molecules and about their movement inside the matter. This article treats of the preparation of thermal neutron beams and of the applications that use their penetration and matter activation properties: 1 - thermal neutrons production; 2 - basic properties of thermal neutrons: neutrons scattering, absorbing materials, activating materials, transparent materials, preparation of a neutron beam; 3 - tracks measurement by activation: activation method, measurement of marine pollution by heavy elements, historical evolution of glass composition; 4 - neutron radiography: neutronography, neutronoscopy: viscosity measurement; 5 - cancer treatment. (J.S.)

Note: A well-confined pulsed low-energy ion beam: Test experiments of Ar+

Science.gov (United States)

Hu, Jie; Wu, Chun-Xiao; Tian, Shan Xi

2018-06-01

Here we report a pulsed low-energy ion beam source for ion-molecule reaction study, in which the ions produced by the pulsed electron impact are confined well in the spatial size of each bunch. In contrast to the ion focusing method to reduce the transverse section of the beam, the longitudinal section in the translational direction is compressed by introducing a second pulse in the ion time-of-flight system. The test experiments for the low-energy argon ions are performed. The present beam source is ready for applications in the ion-molecule reaction dynamics experiments, in particular, in combination with the ion velocity map imaging technique.

Isotope separation apparatus and method

International Nuclear Information System (INIS)

Feldman, B. J.

1985-01-01

The invention relates to an improved method and apparatus for laser isotope separation by photodeflection. A molecular beam comprising at least two isotopes to be separated intersects, preferably substantially perpendicular to one broad side of the molecular beam, with a laser beam traveling in a first direction. The laser beam is reflected back through the molecular beam, preferably in a second direction essentially opposite to the first direction. Because the molecules in the beam occupy various degenerate energy levels, if the laser beam comprises chirped pulses comprising selected wavelengths, the laser beam will very efficiently excite substantially all unexcited molecules and will cause stimulated emission of substantially all excited molecules of a selected one of the isotopes in the beam which such pulses encounter. Excitation caused by first direction chirped pulses moves molecules of the isotope excited thereby in the first direction. Stimulated emission of excited molecules of the isotope is brought about by returning chirped pulses traveling in the second direction. Stimulated emission moves emitting molecules in a direction opposite to the photon emitted. Because emitted photons travel in the second direction, emitting molecules move in the first direction. Substantial molecular movement of essentially all the molecules containing the one isotope is accomplished by a large number of chirped pulse-molecule interactions. A beam corer collects the molecules in the resulting enriched divergent portions of the beam

New structural studies of liquid crystal by reflectivity and resonant X-ray diffraction; Nouvelles etudes structurales de cristaux liquides par reflectivite et diffraction resonante des rayons X

Energy Technology Data Exchange (ETDEWEB)

Fernandes, P

2007-04-15

This memory presents three structural studies of smectic Liquid Crystals by reflectivity and resonant diffraction of X-rays. It is divided in five chapters. In the first a short introduction to Liquid Crystals is given. In particular, the smectic phases that are the object of this study are presented. The second chapter is consecrated to the X-ray experimental techniques that were used in this work. The three last chapters present the works on which this thesis can be divided. Chapter three demonstrates on free-standing films of MHPOBC (historic liquid crystal that possesses the antiferroelectric sub-phases) the possibility to extend the technique of resonant X-ray diffraction to liquid crystals without resonant element. In the fourth chapter the structure of the B{sub 2} liquid crystal phase of bent-core molecules (or banana molecules) is elucidated by using resonant X-ray diffraction combined with polarization analysis of the diffracted beam. A model of the polarization of the resonant beam diffracted by four different structures proposed for the B{sub 2} phase is developed in this chapter. In the fifth chapter a smectic binary mixture presenting a very original critical point of phase separation is studied by X-ray reflectivity and optical microscopy. A concentration gradient in the direction perpendicular to the plane of the film seems to be induced by the free-standing film geometry. The results of a simplified model of the system are compatible with this interpretation.

An atomic coilgun: using pulsed magnetic fields to slow a supersonic beam

International Nuclear Information System (INIS)

Narevicius, E; Parthey, C G; Libson, A; Narevicius, J; Chavez, I; Even, U; Raizen, M G

2007-01-01

We report the experimental demonstration of a novel method to slow atoms and molecules with permanent magnetic moments using pulsed magnetic fields. In our experiments, we observe the slowing of a supersonic beam of metastable neon from 461.0 ± 7.7 to 403 ± 16 m s -1 in 18 stages, where the slowed peak is clearly separated from the initial distribution. This method has broad applications as it may easily be generalized, using seeding and entrainment into supersonic beams, to all paramagnetic atoms and molecules

Isotope separation apparatus and method

International Nuclear Information System (INIS)

Cotter, T.P.

1982-01-01

The invention relates to a method and apparatus for laser isotope separation by photodeflection. A molecular beam comprising at least two isotopes to be separated intersects, preferable substantially perpendicular to one broad side of the molecular beam, with a laser beam traveling in a first direction. The laser beam is reflected back through the molecular beam, preferably in a second direction essentially opposite to the first direction. The laser beam comprises pi-pulses of a selected wavelength which excite unexcited molecules, or cause stimulated emission of excited molecules of one of the isotopes. Excitation caused by first direction pi-pulses moves molecules of the isotope excited thereby in the first direction. Stimulated emission of excited molecules of the isotope is brought about by returning pi-pulses traveling in the second direction. Stimulated emission moves emitting molecules in a direction opposite to the photon emitted. Because emitted photons travel in the second direction, emitting molecules move in the first direction. Substantial molecular movement is accomplished by a large number of pi-pulse-molecule interactions. A beam corer collects the molecules in the resulting enriched divergent portions of the beam

Generation and propagation characteristics of a localized hollow beam

Science.gov (United States)

Xia, Meng; Wang, Zhizhang; Yin, Yaling; Zhou, Qi; Xia, Yong; Yin, Jianping

2018-05-01

A succinct experimental scheme is demonstrated to generate a localized hollow beam by using a π-phase binary bitmap and a convergent thin lens. The experimental results show that the aspect ratio of the dark-spot size of the hollow beam can be effectively controlled by the focal length of the lens. The measured beam profiles in free space also agree with the theoretical modeling. The studies hold great promise that such a hollow beam can be used to cool trapped atoms (or molecules) by Sisyphus cooling and to achieve an optically-trapped Bose–Einstein condensate by optical-potential evaporative cooling.

Focused ion beam-fabricated Au micro/nanostructures used as a surface enhanced Raman scattering-active substrate for trace detection of molecules and influenza virus

Energy Technology Data Exchange (ETDEWEB)

Lin, Ying-Yi; Liao, Jiunn-Der; Ju, Yu-Hung; Chang, Chia-Wei [Department of Materials Science and Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Shiau, Ai-Li, E-mail: jdliao@mail.ncku.edu.tw [Department of Microbiology and Immunology, National Cheng Kung University, No 1, University Road, Tainan 70101, Taiwan (China)

2011-05-06

The focused ion beam (FIB) technique was used to precisely fabricate patterned Au micro/nanostructures (fibAu). The effects of surface enhanced Raman scattering (SERS) on the fibAu samples were investigated by adjusting the geometrical, dimensional, and spacing factors. The SERS mechanism was evaluated using low-concentration rhodamine 6G (R6G) molecules, physically adsorbed or suspended on/within the micro/nanostructures. The results indicated that for detecting R6G molecules, hexagon-like micro/nanostructures induced a higher electromagnetic mechanism (EM) due to the availability of multiple edges and small curvature. By decreasing the dimensions from 300 to 150 nm, the laser-focused area contained an increasing number of micro/nanostructures and therefore intensified the excitation of SERS signals. Moreover, with an optimized geometry and dimensions of the micro/nanostructures, the relative intensity/surface area value reached a maximum as the spacing was 22 nm. An exponential decrease was found as the spacing was increased, which most probably resulted from the loss of EM. The spacing between the micro/nanostructures upon the fibAu was consequently regarded as the dominant factor for the detection of R6G molecules. By taking an optimized fibAu to detect low-concentration influenza virus, the amino acids from the outermost surface of the virus can be well distinguished through the SERS mechanism.

Structured surface reflector design for oblique incidence beam splitter at 610 GHz.

Science.gov (United States)

Defrance, F; Casaletti, M; Sarrazin, J; Wiedner, M C; Gibson, H; Gay, G; Lefèvre, R; Delorme, Y

2016-09-05

An iterative alternate projection-based algorithm is developed to design structured surface reflectors to operate as beam splitters at GHz and THz frequencies. To validate the method, a surface profile is determined to achieve a reflector at 610 GHz that generates four equal-intensity beams towards desired directions of ±12.6° with respect to the specular reflection axis. A prototype is fabricated and the beam splitter behavior is experimentally demonstrated. Measurements confirm a good agreement (within 1%) with computer simulations using Feko, validating the method. The beam splitter at 610 GHz has a measured efficiency of 78% under oblique incidence illumination that ensures a similar intensity between the four reflected beams (variation of about 1%).

Investigation of industrial-scale carbon dioxide reduction using pulsed electron beams

Energy Technology Data Exchange (ETDEWEB)

Petrov, G. M.; Apruzese, J. P.; Petrova, Tz. B.; Wolford, M. F. [Plasma Physics Division, Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC 20375-5346 (United States)

2016-03-14

Carbon dioxide is the most important greenhouse gas contributing to global warming. To help mitigate increasing CO{sub 2} concentrations, we investigate a method of carbon dioxide reduction using high-power electron beams, which can be used on an industrial scale. A series of experiments are conducted in which the reduction of CO{sub 2} is measured for different gas compositions and power deposition rates. An electron beam deposition model is applied to compute reduction rates of CO{sub 2} and energy cost for breaking a CO{sub 2} molecule in flue gas and pure carbon dioxide at atmospheric pressure. For flue gas consisting of 82% N{sub 2}, 6% O{sub 2}, and 12% CO{sub 2}, the calculated energy cost is 85 eV per molecule. In order to dissociate 50% of the CO{sub 2} molecules, beam energy density deposition on the order of 20 J/cm{sup 3} is required. Electron beam irradiation of 12.6 liter gas volume containing 90% CO{sub 2} and 10% CH{sub 4} at beam energy density deposition of 4.2 J/cm{sup 3}, accumulated over 43 shots in a 20 min interval, reduced the CO{sub 2} concentration to 78%. Analogous experiments with a gas mixture containing 11.5% CO{sub 2}, 11.5% CH{sub 4}, and balance of Ar, reduced the CO{sub 2} concentration to below 11% with energy deposition 0.71 J/cm{sup 3}, accumulated over 10 shots in a 5 min interval. The experimental data and the theoretical predictions of CO{sub 2} reduction using pulsed electron beams are in agreement within the experimental error. Other techniques to enhance the removal of CO{sub 2} with pulsed electron beams are also explored, yielding new possible avenues of research.

Metallic plates lens focalizing a high power microwave beam

International Nuclear Information System (INIS)

Rebuffi, L.

1987-08-01

A metallic grating composed of thin parallel plates opportunely spaced, permits to correct the phase of an incident high power microwave beam. In this work we show how it is possible to obtain a beam focalisation (lens), a beam deflection (prisma), or a variation in the polarization (polarizer) using parallel metallic plates. The main design parameters are here presented, in order to obtain the wanted phase modification keeping low the diffraction, the reflected power, the ohmic losses and avoiding breakdowns. Following the given criteria, a metallic plate lens has been realized to focalize the 200 KW, 100 msec 60 GHz beam used in the ECRH experiment on the TFR tokamak. The experimental beam concentration followed satisfactory the design requirements. In fact, the maximum intensity increased about twice the value without lens. In correspondence of this distance a reduction of the beam size of about 50% have been measured for the -3 dB radius. The lens supported high power tests without breakdowns or increase of the reflected power

Chemical reaction dynamics of Rydberg atoms with neutral molecules: A comparison of molecular-beam and classical trajectory results for the H(n)+D2→HD+D(n') reaction

International Nuclear Information System (INIS)

Song Hui; Dai Dongxu; Wu Guorong; Wang, C.-C.; Harich, Steven A.; Hayes, Michael Y.; Wang Xiuyan; Gerlich, Dieter; Yang Xueming; Skodje, Rex T.

2005-01-01

Recent molecular-beam experiments have probed the dynamics of the Rydberg-atom reaction, H(n)+D 2 →HD+D(n) at low collision energies. It was discovered that the rotationally resolved product distribution was remarkably similar to a much more limited data set obtained at a single scattering angle for the ion-molecule reaction H + +D 2 →D + +HD. The equivalence of these two problems would be consistent with the Fermi-independent-collider model (electron acting as a spectator) and would provide an important new avenue for the study of ion-molecule reactions. In this work, we employ a classical trajectory calculation on the ion-molecule reaction to facilitate a more extensive comparison between the two systems. The trajectory simulations tend to confirm the equivalence of the ion+molecule dynamics to that for the Rydberg-atom+molecule system. The theory reproduces the close relationship of the two experimental observations made previously. However, some differences between the Rydberg-atom experiments and the trajectory simulations are seen when comparisons are made to a broader data set. In particular, the angular distribution of the differential cross section exhibits more asymmetry in the experiment than in the theory. The potential breakdown of the classical model is discussed. The role of the 'spectator' Rydberg electron is addressed and several crucial issues for future theoretical work are brought out

Irradiation of wastewater with electron beam is a key to sustainable smart/green cities: a review

Science.gov (United States)

Hossain, Kaizar; Maruthi, Y. Avasn; Das, N. Lakshmana; Rawat, K. P.; Sarma, K. S. S.

2018-03-01

Remediation of wastewater, sludge and removal of objectionable substances from our environment using radiation technology is neglected. Hardly, a couple of decades ago, application of electron beam (EB) technology has gained attention for waste management. When wastewater is irradiated with electron beam, the beam can alter the physico-chemical properties of irradiated aqueous material and also transform wastewater chemicals due to the excitation or ionization of chemical molecules. Thus, chemical reactions may be capable of producing new compounds. The beam of electrons initiates primary reactions to induce the excitation or ionization of molecules at varied rates. This review paper will help to a budding researcher how to optimize the irradiation process to achieve high efficiency with low electron beam energy which is economically viable/feasible. Application of E-beam radiation for wastewater treatment may ensure future smart cities with sustainable water resources management.

Intense low energy positron beams

International Nuclear Information System (INIS)

Lynn, K.G.; Jacobsen, F.M.

1993-01-01

Intense positron beams are under development or being considered at several laboratories. Already today a few accelerator based high intensity, low brightness e + beams exist producing of the order of 10 8 - 10 9 e + /sec. Several laboratories are aiming at high intensity, high brightness e + beams with intensities greater than 10 9 e + /sec and current densities of the order of 10 13 - 10 14 e + sec - 1 cm -2 . Intense e + beams can be realized in two ways (or in a combination thereof) either through a development of more efficient B + moderators or by increasing the available activity of B + particles. In this review we shall mainly concentrate on the latter approach. In atomic physics the main trust for these developments is to be able to measure differential and high energy cross-sections in e + collisions with atoms and molecules. Within solid state physics high intensity, high brightness e + beams are in demand in areas such as the re-emission e + microscope, two dimensional angular correlation of annihilation radiation, low energy e + diffraction and other fields. Intense e + beams are also important for the development of positronium beams, as well as exotic experiments such as Bose condensation and Ps liquid studies

High resolution low dose transmission electron microscopy real-time imaging and manipulation of nano-scale objects in the electron beam

Science.gov (United States)

Brown, Jr., R. Malcolm; Barnes, Zack [Austin, TX; Sawatari, Chie [Shizuoka, JP; Kondo, Tetsuo [Kukuoka, JP

2008-02-26

The present invention includes a method, apparatus and system for nanofabrication in which one or more target molecules are identified for manipulation with an electron beam and the one or more target molecules are manipulated with the electron beam to produce new useful materials.

Calculation of beam neutralization in the IPNS-Upgrade RCS

International Nuclear Information System (INIS)

Chae, Yong-Chul.

1995-01-01

The author calculated the neutralization of circulating beam in this report. In the calculation it is assumed that all electrons liberated from the background molecules due to the collisional processes are trapped in the potential well of the proton beam. Including the dependence of ionization cross sections on the kinetic energy of the incident particle, the author derived the empirical formula for beam neutralization as a function of time and baseline vacuum pressure, which is applicable to the one acceleration cycle of the IPNS-Upgrade RCS

Imaging of Volume Phase Gratings in a Photosensitive Polymer, Recorded in Transmission and Reflection Geometry

Directory of Open Access Journals (Sweden)

Tina Sabel

2014-02-01

Full Text Available Volume phase gratings, recorded in a photosensitive polymer by two-beam interference exposure, are studied by means of optical microscopy. Transmission gratings and reflection gratings, with periods in the order of 10 μm down to 130 nm, were investigated. Mapping of holograms by means of imaging in sectional view is introduced to study reflection-type gratings, evading the resolution limit of classical optical microscopy. In addition, this technique is applied to examine so-called parasitic gratings, arising from interference from the incident reference beam and the reflected signal beam. The appearance and possible avoidance of such unintentionally recorded secondary structures is discussed.

Correction for reflected sky radiance in low-altitude coastal hyperspectral images.

Science.gov (United States)

Kim, Minsu; Park, Joong Yong; Kopilevich, Yuri; Tuell, Grady; Philpot, William

2013-11-10

Low-altitude coastal hyperspectral imagery is sensitive to reflections of sky radiance at the water surface. Even in the absence of sun glint, and for a calm water surface, the wide range of viewing angles may result in pronounced, low-frequency variations of the reflected sky radiance across the scan line depending on the solar position. The variation in reflected sky radiance can be obscured by strong high-spatial-frequency sun glint and at high altitude by path radiance. However, at low altitudes, the low-spatial-frequency sky radiance effect is frequently significant and is not removed effectively by the typical corrections for sun glint. The reflected sky radiance from the water surface observed by a low-altitude sensor can be modeled in the first approximation as the sum of multiple-scattered Rayleigh path radiance and the single-scattered direct-solar-beam radiance by the aerosol in the lower atmosphere. The path radiance from zenith to the half field of view (FOV) of a typical airborne spectroradiometer has relatively minimal variation and its reflected radiance to detector array results in a flat base. Therefore the along-track variation is mostly contributed by the forward single-scattered solar-beam radiance. The scattered solar-beam radiances arrive at the water surface with different incident angles. Thus the reflected radiance received at the detector array corresponds to a certain scattering angle, and its variation is most effectively parameterized using the downward scattering angle (DSA) of the solar beam. Computation of the DSA must account for the roll, pitch, and heading of the platform and the viewing geometry of the sensor along with the solar ephemeris. Once the DSA image is calculated, the near-infrared (NIR) radiance from selected water scan lines are compared, and a relationship between DSA and NIR radiance is derived. We then apply the relationship to the entire DSA image to create an NIR reference image. Using the NIR reference image

Polarization properties of linearly polarized parabolic scaling Bessel beams

Energy Technology Data Exchange (ETDEWEB)

Guo, Mengwen; Zhao, Daomu, E-mail: zhaodaomu@yahoo.com

2016-10-07

The intensity profiles for the dominant polarization, cross polarization, and longitudinal components of modified parabolic scaling Bessel beams with linear polarization are investigated theoretically. The transverse intensity distributions of the three electric components are intimately connected to the topological charge. In particular, the intensity patterns of the cross polarization and longitudinal components near the apodization plane reflect the sign of the topological charge. - Highlights: • We investigated the polarization properties of modified parabolic scaling Bessel beams with linear polarization. • We studied the evolution of transverse intensity profiles for the three components of these beams. • The intensity patterns of the cross polarization and longitudinal components can reflect the sign of the topological charge.

Transition paths in single-molecule force spectroscopy.

Science.gov (United States)

Cossio, Pilar; Hummer, Gerhard; Szabo, Attila

2018-03-28

In a typical single-molecule force spectroscopy experiment, the ends of the molecule of interest are connected by long polymer linkers to a pair of mesoscopic beads trapped in the focus of two laser beams. At constant force load, the total extension, i.e., the end-to-end distance of the molecule plus linkers, is measured as a function of time. In the simplest systems, the measured extension fluctuates about two values characteristic of folded and unfolded states, with occasional transitions between them. We have recently shown that molecular (un)folding rates can be recovered from such trajectories, with a small linker correction, as long as the characteristic time of the bead fluctuations is shorter than the residence time in the unfolded (folded) state. Here, we show that accurate measurements of the molecular transition path times require an even faster apparatus response. Transition paths, the trajectory segments in which the molecule (un)folds, are properly resolved only if the beads fluctuate more rapidly than the end-to-end distance of the molecule. Therefore, over a wide regime, the measured rates may be meaningful but not the transition path times. Analytic expressions for the measured mean transition path times are obtained for systems diffusing anisotropically on a two-dimensional free energy surface. The transition path times depend on the properties both of the molecule and of the pulling device.

Three-beam double stimulated Raman scatterings: Cascading configuration

Science.gov (United States)

Rao, B. Jayachander; Cho, Minhaeng

2018-03-01

Two-beam stimulated Raman scattering (SRS) has been used in diverse label-free spectroscopy and imaging applications of live cells, biological tissues, and functional materials. Recently, we developed a theoretical framework for the three-beam double SRS processes that involve pump, Stokes, and depletion beams, where the pump-Stokes and pump-depletion SRS processes compete with each other. It was shown that the net Stokes gain signal can be suppressed by increasing the depletion beam intensity. The theoretical prediction has been experimentally confirmed recently. In the previous scheme for a selective suppression of one SRS by making it compete with another SRS, the two SRS processes occur in a parallel manner. However, there is another possibility of three-beam double SRS scheme that can be of use to suppress either Raman gain of the Stokes beam or Raman loss of the pump beam by depleting the Stokes photons with yet another SRS process induced by the pair of Stokes and another (second) Stokes beam. This three-beam double SRS process resembles a cascading energy transfer process from the pump beam to the first Stokes beam (SRS-1) and subsequently from the first Stokes beam to the second Stokes beam (SRS-2). Here, the two stimulated Raman gain-loss processes are associated with two different Raman-active vibrational modes of solute molecule. In the present theory, both the radiation and the molecules are treated quantum mechanically. We then show that the cascading-type three-beam double SRS can be described by coupled differential equations for the photon numbers of the pump and Stokes beams. From the approximate solutions as well as exact numerical calculation results for the coupled differential equations, a possibility of efficiently suppressing the stimulated Raman loss of the pump beam by increasing the second Stokes beam intensity is shown and discussed. To further prove a potential use of this scheme for developing a super-resolution SRS microscopy, we

Development of Beam Utilization Technologies and Support for Users

International Nuclear Information System (INIS)

Kim, Kyeryung; Jung, Myunghwan; Noh, Yongoh; Lee, Sooyeon; Kim, Hyukwook; Kil, Jaekeun; Lee, Nayoung; Ra, Sekin; Lee, Miejeen; Kim, Sora

2013-02-01

The Final goals are to achieve the 2nd goals of the Proton Engineering Frontier Project, development of proton beam utilization technologies, to incubate the potential users, and to develop fundamental technologies. Based on these achievements, we are going to enhance the accelerator utilization and maximize contribution to the local society after accelerator construction completion. For the these goals, we were operating user program reflecting the results of 3rd step planning. We support 38 small projects during 2 years. As results of activation of beam utilization, we acquired 768 users at the end of 2012. We survey proton beam technology proposals, individuals and institutions participation letter of intent through the research of 'Planning of a support program for both basic research by using accelerator and manpower cultivation'. And inaugurated KOPUA (Korea Proton Accelerator User Association) on March 28, 2012 with 152 members. We secured experimental conditions at TR23 and TR103 and reflected in the target room design and operation scenarios via investigate the requirements. Through these requirements, we make a remote sample transfer system, beam regulating system, hot cell and sample transport container. Moreover, we develop proton beam technologies such as in-vivo proton beam irradiation system, comparison of the biological effects for pulse beam and continuous beam, basic experiments for the metal nanopaticle synthesis, research for radioactivatied samples and devices, conceptual design and calculation for neutron source target and calculation of the isotope production yield. Proton accelerator can be utilized in a variety of field, including NT, BT, IT, ST, ET, Nuclear, medical, and some of the user facilities required were constructed through this project, Experience for the construction and operation of these facilities can be reflected to the construction of the rest 8 target room of proton accelerator center

Multiphoton processes in isolated atoms and molecules

International Nuclear Information System (INIS)

Sudbo, A.S.

1979-11-01

The theory of coherent excitation of a multilevel quantum mechanical system is developed. Damping of the system is taken into account by the use of a density matrix formalism. General properties of the wave function and/or the density matrix are discussed. The physical implications for the behavior of the system are described, together with possible applications of the formalism, including the infrared multiphoton excitation of molecules, and optical pumping in alkali atoms. Experimental results are presented on the infrared multiphoton dissociation of molecules, followed by a discussion of the general features of this process. The experimental results were obtained using a crossed laser and molecular beam method, and the emphasis is on determining the properties of the dissociating molecule and the dissociation products. The dissociation process is shown to be described very well by the standard statistical theory (RRKM theory) of unimolecular reactions, a brief presentation of which is also included

Fast metastable hydrogen atoms from H2 molecules: twin atoms

Directory of Open Access Journals (Sweden)

Trimèche A.

2015-01-01

Full Text Available It is a difficult task to obtain “twin atoms”, i.e. pairs of massive particles such that one can perform experiments in the same fashion that is routinely done with “twin photons”. One possible route to obtain such pairs is by dissociating homonuclear diatomic molecules. We address this possibility by investigating the production of metastable H(2s atoms coming from the dissociation of cold H2 molecules produced in a Campargue nozzle beam crossing an electron beam from a high intensity pulsed electron gun. Dissociation by electron impact was chosen to avoid limitations of target molecular excited states due to selection rules. Detectors placed several centimeters away from the collision center, and aligned with respect to possible common molecular dissociation channel, analyze the neutral fragments as a function of their time-of-flight (TOF through Lyman-α detection. Evidence for the first time observed coincidence of pairs of H(2s atoms obtained this way is presented.

Low-energy positron interactions with atoms and molecules

International Nuclear Information System (INIS)

Surko, C M; Gribakin, G F; Buckman, S J

2005-01-01

This paper is a review of low-energy positron interactions with atoms and molecules. Processes of interest include elastic scattering, electronic and vibrational excitation, ionization, positronium formation and annihilation. An overview is presented of the currently available theoretical and experimental techniques to study these phenomena, including the use of trap-based positron beam sources to study collision processes with improved energy resolution. State-resolved measurements of electronic and vibrational excitation cross sections and measurement of annihilation rates in atoms and molecules as a function of incident positron energy are discussed. Where data are available, comparisons are made with analogous electron scattering cross sections. Resonance phenomena, common in electron scattering, appear to be less common in positron scattering. Possible exceptions include the sharp onsets of positron-impact electronic and vibrational excitation of selected molecules. Recent energy-resolved studies of positron annihilation in hydrocarbons containing more than a few carbon atoms provide direct evidence that vibrational Feshbach resonances underpin the anomalously large annihilation rates observed for many polyatomic species. We discuss open questions regarding this process in larger molecules, as well as positron annihilation in smaller molecules where the theoretical picture is less clear. (topical review)

Investigation of photobleaching and saturation of single molecules by fluorophore recrossing events

Energy Technology Data Exchange (ETDEWEB)

Burrows, Sean M.; Reif, Randall D. [Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061 (United States); Pappas, Dimitri [Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, TX 79409-1061 (United States)], E-mail: d.pappas@ttu.edu

2007-08-15

A method for investigation of photobleaching and saturation of single molecules by fluorophore recrossing events in a laser beam is described. The diffraction-limited probe volumes encountered in single-molecule detection (SMD) produce high excitation irradiance, which can decrease available signal. The single molecules of several dyes were detected and the data was used to extract interpeak times above a defined threshold value. The interpeak times revealed the number of fluorophore recrossing events. The number of molecules detected that were within 2 ms of each other represented a molecular recrossing for this work. Calcein, fluorescein and R-phycoerythrin were analyzed and the saturation irradiance and photobleaching effects were determined as a function of irradiance. This approach is simple and it serves as a method of optimizing experimental conditions for single-molecule detection.

Electron-impact ionization of SiCl{sub 3} using an improved crossed fast-neutral-beam - electron-beam apparatus

Energy Technology Data Exchange (ETDEWEB)

Mahoney, J M; Gutkin, M V; Tarnovsky, V; Becker, K [Department of Physics and Engineering Physics, Stevens Institute of Technology, Hoboken, NJ 07030 (United States)], E-mail: kbecker@poly.edu

2008-05-15

The fast-neutral-beam technique is a versatile approach to the determination of absolute cross sections for electron-impact ionization of atoms, stable molecules as well as free radicals and metastable species. A fast neutral beam of the species under study is prepared by charge-transfer neutralization of a mass-selected ion beam and the species are subsequently ionized by an electron beam. Mass- and energy-dispersive selection separates singly from multiply charged ions and parent from fragment ions and allows the determination of partial ionization cross sections. Here we describe some major improvements that were made recently to the fast-beam apparatus that has been used extensively for ionization cross section measurements for the past 15 years in our group. Experiments using well-established ionization cross sections in conjunction with extensive ion trajectory simulations were carried out to test the satisfactory performance of the modified fast-neutral-beam apparatus. We also report absolute partial cross sections for the formation of various singly charged positive ions produced by electron impact on SiCl{sub 3} for impact energies from threshold to 200 eV in the modified fast-beam apparatus.

Reflection of the solar wind ions at the earth's bow shock: energization

International Nuclear Information System (INIS)

Bonifazi, C.; Moreno, G.; Russell, C.T.

1983-01-01

The energies of the field-aligned proton beams observed upstream of the earth's bow shock are tested, on a statistical basis, against a simple reflection model. The comparison is carried out using both plasma and magnetic field data collected by the ISEE 2 spacecraft. The observations refer to the period from November 5 to December 20, 1977. According to this model, some of the solar wind protons incident upon the earth's shock front when reflected upstream gain energy by displacement parallel to the interplanetary electric field. The energy gained in the reflection can be described as a function of the angles between the interplanetary magnetic field, the solar wind bulk velocity, and the local shock normal. The task of finding these angles, i.e., the expected source point of the reflected ions at the earth's shock front, has been resolved using both the measured magnetic field direction and actual beam trajectory. The latter method, which takes into account the ion drift velocity, leads to a better agreement between theory and observations when far from the shock. In particular, it allows us to check the energies of the field-aligned beams even when they are observed far from the earth's bow shock (at distances up to 10-15 R/sub E/). We confirm, on a statistical basis, the test of the model recently carried out using the Los Alamos National Laboratory/Max-Planck-extraterrestrische observations on ISEE 1 and 2. We infer that reflected beams can sometimes propagate far upstream of the earth's bow shock without changing their energy properties

Cryogenic Beam Screens for High-Energy Particle Accelerators

CERN Document Server

Baglin, V; Tavian, L; van Weelderen, R

2013-01-01

Applied superconductivity has become a key enabling technology for high-energy particle accelerators, thus making them large helium cryogenic systems operating at very low temperature. The circulation of high-intensity particle beams in these machines generates energy deposition in the first wall through different processes. For thermodynamic efficiency, it is advisable to intercept these beam-induced heat loads, which may be large in comparison with cryostat heat in-leaks, at higher temperature than that of the superconducting magnets of the accelerator, by means of beam screens located in the magnet apertures. Beam screens may also be used as part of the ultra-high vacuum system of the accelerator, by sheltering the gas molecules cryopumped on the beam pipe from impinging radiation and thus avoiding pressure runaway. Space being extremely tight in the magnet apertures, cooling of the long, slender beam screens also raises substantial problems in cryogenic heat transfer and fluid flow. We present sizing rule...

Microwave generation and frequency conversion using intense relativistic electron beams

International Nuclear Information System (INIS)

Buzzi, J.M.; Doucet, H.J.; Etlicher, B.

1977-01-01

Some aspects of the microwave generation and frequency conversion by relativistic electron beams are studied. Using an electron synchrotron maser, the excitation of microwaves by an annular relativistic electron beam propagating through a circular wave guide immersed in a longitudinal magnetic field is analyzed. This theoretical model is somewhat more realistic than the previous one because the guiding centers are not on the wave guide axis. Microwave reflection is observed on a R.E.B. front propagating into a gas filled waveguide. The frequency conversion from the incident X-band e.m. waves and the reflected Ka band observed signal is consistent with the Doppler model for β = 0.7. This value agrees with the average beam front velocity as measured from time-of-flight using two B/sub theta/ probes. The reflection is found to occur during the current rise time. With a low impedance device (2 Ω, 400 keV) a GW X-band emission has been observed using thin anodes and a gas filled waveguide. This emission is probably due to the self-fields of the beam and could be used as a diagnostic

Photoionization studies with molecular beams

Energy Technology Data Exchange (ETDEWEB)

Ng, C.Y.

1976-09-01

A molecular beam photoionization apparatus which combines the advantages of both the molecular beam method with photoionization mass spectrometry has been designed and constructed for carrying out some unique photoionization experiments. Rotational cooling during the supersonic expansion has resulted in high resolution photoionization efficiency curves for NO, ICl, C/sub 2/H/sub 2/ and CH/sub 3/I. The analysis of these spectra has yielded ionization potentials for these molecules to an accuracy of +- 3 MeV. Detailed autoionization structures were also resolved. This allows the investigation of the selection rules for autoionization, and the identification of the Rydberg series which converge to the excited states of the molecular ions. The degree of relaxation for thermally populated excited states has been examined using NO and ICl as examples. As a result of adiabatic cooling, a small percentage of dimers is also formed during the expansion. The photoionization efficiency curves for (NO)/sub 2/, ArICl, Ar/sub 2/, Kr/sub 2/ and Xe/sub 2/ have been obtained near the thresholds. Using the known dissociation energies of the (NO)/sub 2/, Ar/sub 2/, Kr/sub 2/ and Xe/sub 2/ van der Waals molecules, the corresponding dissociation energies for NO-NO/sup +/, Ar/sub 2//sup +/, Kr/sub 2//sup +/, and Xe/sub 2//sup +/ have been determined. The ionization mechanisms for this class of molecules are examined and discussed.

Possible heterogeneity of centres of binding 1,8-ANS in molecules of oxygenated hemoglobin

International Nuclear Information System (INIS)

Parul', D.A.; Bokut', S.B.; Milyutin, A.A.; Petrov, E.P.; Nemkovich, N.A.; Sobchuk, A.N.; Dzhagarov, B.M.

1999-01-01

Forming of oxygenated hemoglobin is one of effects of ionizing radiation action on organism. It was revealed heterogeneity of centers of binding of 1,8-ANS in intact molecule of oxygenated hemoglobin. Two types of binding centers possible reflect the existence of two regions in protein molecule with different accessibility to molecules of water

Power-recycled michelson interferometer with a 50/50 grating beam splitter

International Nuclear Information System (INIS)

Friedrich, D; Burmeister, O; Britzger, M; Bunkowski, A; Danzmann, K; Schnabel, R; Clausnitzer, T; Fahr, S; Kley, E-B; Tuennermann, A

2008-01-01

We designed and fabricated an all-reflective 50/50 beam splitter based on a dielectric grating. This beam splitter was used to set up a power-recycled Michelson interferometer with a finesse of about F PR ∼ 880. Aspects of the diffractive beam splitter as well as of the interferometer design are discussed

Power-recycled michelson interferometer with a 50/50 grating beam splitter

OpenAIRE

Friedrich, Daniel; Burmeister, O.; Britzger, M.; Bunkowski, A.; Clausnitzer, T.; Fahr, S.; Kley, E.B.; Tünnermann, A.; Danzmann, Karsten; Schnabel, Roman

2008-01-01

We designed and fabricated an all-reflective 50/50 beam splitter based on a dielectric grating. This beam splitter was used to set up a power-recycled Michelson interferometer with a finesse of about FPR ≈ 880. Aspects of the diffractive beam splitter as well as of the interferometer design are discussed.

Analysis of contaminants on electronic components by reflectance FTIR spectroscopy

International Nuclear Information System (INIS)

Griffith, G.W.

1982-09-01

The analysis of electronic component contaminants by infrared spectroscopy is often a difficult process. Most of the contaminants are very small, which necessitates the use of microsampling techniques. Beam condensers will provide the required sensitivity but most require that the sample be removed from the substrate before analysis. Since it can be difficult and time consuming, it is usually an undesirable approach. Micro ATR work can also be exasperating, due to the difficulty of positioning the sample at the correct place under the ATR plate in order to record a spectrum. This paper describes a modified reflection beam condensor which has been adapted to a Nicolet 7199 FTIR. The sample beam is directed onto the sample surface and reflected from the substrate back to the detector. A micropositioning XYZ stage and a close-focusing telescope are used to position the contaminant directly under the infrared beam. It is possible to analyze contaminants on 1 mm wide leads surrounded by an epoxy matrix using this device. Typical spectra of contaminants found on small circuit boards are included

Spin analysis and new effects in reflectivity measurements

International Nuclear Information System (INIS)

Fermon, C.

1996-01-01

We present two new effects in polarized neutron reflectivity. We show that we have a non symmetric spin-flip signal in reflectivity measurements on magnetic films when the external field is not negligible. This phenomenon is due to different Larmor precessions for the two spin states and has to be taken into account in some experiments. The second effect is still not understood but we present results indicating that the specular reflection on a non magnetic surface can induce a neutron beam depolarization or rotation. (authors)

Molecular Beam Chemistry: Reactions of Oxygen Atoms with Halogen Molecules.

Science.gov (United States)

1982-10-15

nonlinear one has s = 3, r = 1, and n = 3/2. In the "loose" complex the bending modes go over to free rotation of the product diatomit molecule; thus s...contains no adjustable parameters. All observable properties *l of the reaction may be predicted including product velocity and angular dis- tributions...example, P. R. Bevington, Data Reduction and Error Analysis for the Physical Sciences (McGraw-Hill Book Co., New York, 1969). 65. Equation (3) is strictly

Rovibrational optical pumping of a molecular beam

Science.gov (United States)

Cournol, A.; Pillet, P.; Lignier, H.; Comparat, D.

2018-03-01

The preparation of molecules in well-defined internal states is essential for various studies in fundamental physics and physical chemistry. It is thus of particular interest to find methods that increase the brightness of molecular beams. Here, we report on rotational and vibrational pumpings of a supersonic beam of barium monofluoride molecules. With respect to previous works, the time scale of optical vibrational pumping has been greatly reduced by enhancing the spectral power density in the vicinity of the appropriate molecular transitions. We demonstrate a complete transfer of the rovibrational populations lying in v″=1 -3 into the vibrational ground-state v″=0 . Rotational pumping, which requires efficient vibrational pumping, has been also demonstrated. According to a Maxwell-Boltzmann description, the rotational temperature of our sample has been reduced by a factor of ˜8 . In this fashion, the population of the lowest rotational levels increased by more than one order of magnitude.

Carbon Electrode-Molecule Junctions: A Reliable Platform for Molecular Electronics.

Science.gov (United States)

Jia, Chuancheng; Ma, Bangjun; Xin, Na; Guo, Xuefeng

2015-09-15

The development of reliable approaches to integrate individual or a small collection of molecules into electrical nanocircuits, often termed "molecular electronics", is currently a research focus because it can not only overcome the increasing difficulties and fundamental limitations of miniaturization of current silicon-based electronic devices, but can also enable us to probe and understand the intrinsic properties of materials at the atomic- and/or molecular-length scale. This development might also lead to direct observation of novel effects and fundamental discovery of physical phenomena that are not accessible by traditional materials or approaches. Therefore, researchers from a variety of backgrounds have been devoting great effort to this objective, which has started to move beyond simple descriptions of charge transport and branch out in different directions, reflecting the interdisciplinarity. This Account exemplifies our ongoing interest and great effort in developing efficient lithographic methodologies capable of creating molecular electronic devices through the combination of top-down micro/nanofabrication with bottom-up molecular assembly. These devices use nanogapped carbon nanomaterials (such as single-walled carbon nanotubes (SWCNTs) and graphene), with a particular focus on graphene, as point contacts formed by electron beam lithography and precise oxygen plasma etching. Through robust amide linkages, functional molecular bridges terminated with diamine moieties are covalently wired into the carboxylic acid-functionalized nanogaps to form stable carbon electrode-molecule junctions with desired functionalities. At the macroscopic level, to improve the contact interface between electrodes and organic semiconductors and lower Schottky barriers, we used SWCNTs and graphene as efficient electrodes to explore the intrinsic properties of organic thin films, and then build functional high-performance organic nanotransistors with ultrahigh responsivities

Beam tube vacuum in future superconducting proton colliders

International Nuclear Information System (INIS)

Turner, W.

1994-10-01

The beam tube vacuum requirements in future superconducting proton colliders that have been proposed or discussed in the literature -- SSC, LHC, and ELN -- are reviewed. The main beam tube vacuum problem encountered in these machines is how to deal with the magnitude of gas desorption and power deposition by synchrotron radiation while satisfying resistivity, impedance, and space constraints in the cryogenic environment of superconducting magnets. A beam tube vacuum model is developed that treats photodesorption of tightly bound H, C, and 0, photodesorption of physisorbed molecules, and the isotherm vapor pressure of H 2 . Experimental data on cold tube photodesorption experiments are reviewed and applied to model calculations of beam tube vacuum performance for simple cold beam tube and liner configurations. Particular emphasis is placed on the modeling and interpretation of beam tube photodesorpiion experiments at electron synchrotron light sources. The paper also includes discussion of the constraints imposed by beam image current heating, the growth rate of the resistive wall instability, and single-bunch instability impedance limits

Real-time single-molecule imaging of quantum interference.

Science.gov (United States)

Juffmann, Thomas; Milic, Adriana; Müllneritsch, Michael; Asenbaum, Peter; Tsukernik, Alexander; Tüxen, Jens; Mayor, Marcel; Cheshnovsky, Ori; Arndt, Markus

2012-03-25

The observation of interference patterns in double-slit experiments with massive particles is generally regarded as the ultimate demonstration of the quantum nature of these objects. Such matter-wave interference has been observed for electrons, neutrons, atoms and molecules and, in contrast to classical physics, quantum interference can be observed when single particles arrive at the detector one by one. The build-up of such patterns in experiments with electrons has been described as the "most beautiful experiment in physics". Here, we show how a combination of nanofabrication and nano-imaging allows us to record the full two-dimensional build-up of quantum interference patterns in real time for phthalocyanine molecules and for derivatives of phthalocyanine molecules, which have masses of 514 AMU and 1,298 AMU respectively. A laser-controlled micro-evaporation source was used to produce a beam of molecules with the required intensity and coherence, and the gratings were machined in 10-nm-thick silicon nitride membranes to reduce the effect of van der Waals forces. Wide-field fluorescence microscopy detected the position of each molecule with an accuracy of 10 nm and revealed the build-up of a deterministic ensemble interference pattern from single molecules that arrived stochastically at the detector. In addition to providing this particularly clear demonstration of wave-particle duality, our approach could also be used to study larger molecules and explore the boundary between quantum and classical physics.

EUV beam splitter for use in the wavelength region around 6 nm

International Nuclear Information System (INIS)

Takenaka, Hisataka; Ichimaru, Satoshi; Gullikson, E.M.

2005-01-01

Extreme ultraviolet (EUV) beam splitters for use at a wavelength of around 6 nm were fabricated. The designs were optimized for Cr/C multilayers and incident angles of 45 deg. and 80 deg. . Measurements revealed the reflectivity of a Cr/C beam splitter to be 3.3% and the transmittance to be 5.6% at a wavelength of 6.36 nm and an incident angle of 45 deg. . The reflectivity of a Cr/C beam splitter was 5.8% and the transmittance was 6.6% at a wavelength of 6.15 nm and an incident angle of 80 deg.

Single beam pass migmacell method and apparatus

International Nuclear Information System (INIS)

Maglich, B.C.; Nering, J.E.; Mazarakis, M.G.; Miller, R.A.

1976-01-01

The invention provides improvements in migmacell apparatus and method by dispensing with the need for metastable confinement of injected molecular ions for multiple precession periods. Injected molecular ions undergo a 'single pass' through the reaction volume. By preconditioning the injected beam such that it contains a population distribution of molecules in higher vibrational states than in the case of a normal distribution, injected molecules in the single pass exper-ience collisionless dissociation in the migmacell under magnetic influence, i.e., so-called Lorentz dissociation. Dissociationions then form atomic migma

Laser systems configured to output a spectrally-consolidated laser beam and related methods

Science.gov (United States)

Koplow, Jeffrey P [San Ramon, CA

2012-01-10

A laser apparatus includes a plurality of pumps each of which is configured to emit a corresponding pump laser beam having a unique peak wavelength. The laser apparatus includes a spectral beam combiner configured to combine the corresponding pump laser beams into a substantially spatially-coherent pump laser beam having a pump spectrum that includes the unique peak wavelengths, and first and second selectively reflective elements spaced from each other to define a lasing cavity including a lasing medium therein. The lasing medium generates a plurality of gain spectra responsive to absorbing the pump laser beam. Each gain spectrum corresponds to a respective one of the unique peak wavelengths of the substantially spatially-coherent pump laser beam and partially overlaps with all other ones of the gain spectra. The reflective elements are configured to promote emission of a laser beam from the lasing medium with a peak wavelength common to each gain spectrum.

Atomic battery with beam switching

International Nuclear Information System (INIS)

Edling, E.A.; McKenna, R.P.; Peterick, E.Th. Jr.; Trexler, F.D.

1984-01-01

An electric power generating apparatus that is powered primarily by the emission of electrically charged particles from radio-active materials enclosed in an evacuated vessel of glass or the like. An arrangement of reflecting electrodes causes a beam of particles to switch back and forth at a high frequency between two collecting electrodes that are connected to a resonating tuned primary circuit consisting of an inductor with resonating capacitor. The reflecting electrodes are energized in the proper phase relationship to the collecting electrodes to insure sustained oscillation by means of a secondary winding coupled inductively to the primary winding and connected to the reflecting electrodes. Power may be drawn from the circuit at a stepped down voltage from a power take-off winding that is coupled to the primary winding. The disclosure also describes a collecting electrode arrangement consisting of multiple spatially separated electrodes which together serve to capture a maximum of the available particle energy. A self-starting arrangement for start of oscillations is described. A specially adapted version of the invention utilizes two complementary beams of oppositely charged particles which are switched alternatingly between the collecting electrodes

MOLECULAR BEAM STUDIES OF IR LASER INDUCED MULTIPHOTON DISSOCIATION AND VIBRATIONAL PREDISSOCIATION

Energy Technology Data Exchange (ETDEWEB)

Lee, Yuan T.; Shen, Y. Ron

1980-06-01

The advancement of crossed molecular beam methods, modern spectroscopy and laser technology allows us to observe chemical reactions on atomic and molecular levels in great detail. After a brief history of crossed molecular beams studies, the author describes and discusses the universal molecular beam apparatus and gives examples of crossed molecular beam studies. The crossed beam technique is compared to other techniques used to provide microscopic information on reaction dynamics. Application of crossed laser and molecular beam studies to the problem of IR multiphoton dissociation of polyatomic molecules is discussed. Study of vibrational predissociation of hydrogen-bonded and van der Waals molecular clusters are discussed. Future cases that the author considers worth pursuing that could benefit from the collisionless environment of molecular beams are enumerated.

Multiple Reflections and Fresnel Absorption of Gaussian Laser Beam in an Actual 3D Keyhole during Deep-Penetration Laser Welding

Directory of Open Access Journals (Sweden)

Xiangzhong Jin

2012-01-01

Full Text Available In deep penetration laser welding, a keyhole is formed in the material. Based on an experimentally obtained bending keyhole from low- and medium-speed laser penetration welding of glass, the keyhole profiles in both the symmetric plane are determined by polynomial fitting. Then, a 3D bending keyhole is reconstructed under the assumption of circular cross-section of the keyhole at each keyhole depth. In this paper, the behavior of focused Gaussian laser beam in the keyhole is analyzed by tracing a ray of light using Gaussian optics theory, the Fresnel absorption and multiple reflections in the keyhole are systematically studied, and the laser intensities absorbed on the keyhole walls are calculated. Finally, the formation mechanism of the keyhole is deduced.

[In situ diffuse reflectance FTIR spectroscopy study of CO adsorption on Ni2P/mesoporous molecule sieve catalysts].

Science.gov (United States)

Liu, Qian-qian; Ji, Sheng-fu; Wu, Ping-yi; Hu, Lin-hua; Huang, Xiao-fan; Zhu, Ji-qin; Li, Cheng-yue

2009-05-01

Abstract The supported nickel phosphate precursors were prepared by incipient wetness impregnation using nickel nitrate as nickel source, diammonium hydrogen phosphate as phosphorus source, and MCM-41, MCM-48, SBA-15 and SBA-16 as supports, respectively. Then, the supported Ni2 P catalysts were prepared by temperature-programmed reduction in flowing Hz from their nickel phosphate precursors. The in situ diffuse reflectance FTIR spectroscopy (DRIFTS) analysis with the probe molecule CO was carried out to characterize the surface properties. The results indicated that there were significant differences in the spectral features of the samples. The upsilon(CO) absorbances observed for adsorbed CO on mesoporous molecule sieve was attributed to weak physical adsorption. There are four different kinds of upsilon(CO) absorbances observed for adsorbed CO on Ni2 P/MCM-41 catalyst with the following assignments: (1) the formation of Ni(CO)4 at 2055 cm(-1). (2) CO terminally bonded to cus Ni(delta+) (0

Spectroscopic determination of species and divergence of hydrogen beams in the W7AS neutral beam injectors

International Nuclear Information System (INIS)

Ott, W.; Penningsfeld, F.P.

1993-01-01

Light-collecting systems are installed at the neutralizers of the W7AS neutral beam lines. They receive light emitted at an angle of 120 to the beam axes. Hydrogen beams are analyzed at around the wavelength of H α (6562.8 A), helium beams at around 5875.6 A. The hydrogen spectra show the well-known shifted and unshifted lines emitted by the different beam species and the background gas. The line widths are mainly determined by the beam focussing, the beamlet divergence and the apparatus profile. Knowing the focussing properties of the ion source and the instrument function of the spectrometer, one can determine the beamlet divergence. The spectrum is approximated by a series of Gaussians using least-squares fitting methods and evaluated with respect to beam species and divergence. Evaluation of the spectra proved difficult because they show a structured background, which is observed in the whole range of the Doppler shift. It is shown with helium beams that the background is caused by wall reflection of light emitted by the beam in the whole angular range between 0 and 180 . The knowledge of the background structure gained with He beams allows interpretation of the more complicated hydrogen spectra. (orig.)

Efficient anomalous reflection through near-field interactions in metasurfaces

Science.gov (United States)

Chalabi, H.; Ra'di, Y.; Sounas, D. L.; Alù, A.

2017-08-01

Gradient metasurfaces have been extensively used in the past few years for advanced wave manipulation over a thin surface. These metasurfaces have been mostly designed based on the generalized laws of reflection and refraction. However, it was recently revealed that metasurfaces based on this approach tend to suffer from inefficiencies and complex design requirements. We have recently proposed a different approach to the problem of efficient beam steering using a surface, based on bianisotropic particles in a periodic array. Here, we show highly efficient reflective metasurfaces formed by pairs of isotropic dielectric rods, which can offer asymmetrical scattering of normally incident beams with unitary efficiency. Our theory shows that moderately broadband anomalous reflection can be achieved with suitably designed periodic arrays of isotropic nanoparticles. We also demonstrate practical designs using TiO2 cylindrical nanorods to deflect normally incident light toward a desired direction. The proposed structures may pave the way to a broader range of light management opportunities, with applications in energy harvesting, signaling, and communications.

Anomalous electron heating and energy balance in an ion beam generated plasma

Energy Technology Data Exchange (ETDEWEB)

Guethlein, G.

1987-04-01

The plasma described in this report is generated by a 15 to 34 kV ion beam, consisting primarily of protons, passing through an H/sub 2/ gas cell neutralizer. Plasma ions (or ion-electron pairs) are produced by electron capture from (or ionization of) gas molecules by beam ions and atoms. An explanation is provided for the observed anomalous behavior of the electron temperature (T/sub e/): a step-lite, nearly two-fold jump in T/sub e/ as the beam current approaches that which minimizes beam angular divergence; insensitivity of T/sub e/ to gas pressure; and the linear relation of T/sub e/ to beam energy.

New Perspectives on the Search for a Parity Violation Effect in Chiral Molecules

Science.gov (United States)

Auguste, F.; Tokunaga, S. K.; Shelkovnikov, A.; Daussy, C.; Amy-Klein, A.; Chardonnet, C.; Darquie, B.

2013-06-01

Parity violation (PV) effects have so far never been observed in chiral molecules. Originating from the weak interaction, PV should lead to frequency differences in the rovibrational spectra of the two enantiomers of a chiral molecule. However the smallness of the effect represents a very difficult experimental challenge. We propose to compare the rovibrational spectra (around 10 μm) of two enantiomers, recorded using the ultra-high resolution spectroscopy technique of Doppler-free two-photon Ramsey interferometry in a supersonic molecular beam. With an alternate beam of left- and right-handed molecules and thanks to our expertise in the control of the absolute frequency of the probe CO_2 lasers, we should reach a fractional sensitivity better around 10^{-15} (a few tens of millihertz), on the frequency difference between enantiomers. We will review our latest results on the high-resolution spectroscopy, either in cell or in a supersonic beam, of methyltrioxorhenium. B. Darquié, C. Stoeffler, A. Shelkovnikov, C. Daussy, A. Amy-Klein, C. Chardonnet, S. Zrig, L. Guy, J. Crassous, P. Soulard, P. Asselin, T. R. Huet, P. Schwerdtfeger, R. Bast and T. Saue, Chirality 22, 870 (2010). C. Stoeffler, B. Darquié, A. Shelkovnikov, C. Daussy, A. Amy-Klein, C. Chardonnet, L. Guy, J. Crassous, T. R. Huet, P. Soulard and P. Asselin, Phys. Chem. Chem. Phys. 13, 854 (2011). N. Saleh, S. Zrig, L. Guy, R. Bast, T. Saue, B. Darquié and J. Crassous, submitted to Phys. Chem. Chem. Phys. (2013).

Designs of infrared nonpolarizing beam splitters with a Ag layer in a glass cube.

Science.gov (United States)

Shi, Jin Hui; Wang, Zheng Ping

2008-05-10

A novel design of a nonpolarizing beam splitter with a Ag layer in a cube was proposed and optimized, based on the needle optimization. The digital simulations of the reflectance and reflection-induced retardance were presented. The simulation results showed that both the amplitude and the phase characteristics of the nonpolarizing beam splitter could realize the design targets. The difference between the simulated and the target reflectance of 50% is less than 0.4% and the simulated and the reflection-induced retardance is less than 0.62 degrees in the 1260 -1360 nm range for both p and s components.

Beam scrubbing of beam pipes during the first commissioning of SuperKEKB

Science.gov (United States)

Suetsugu, Y.; Shibata, K.; Ishibashi, T.; Kanazawa, K.; Shirai, M.; Terui, S.; Hisamatsu, H.

2018-02-01

The first (Phase-1) commissioning of SuperKEKB-an electron-positron collider with asymmetric energies located at KEK, in Tsukuba, Japan-started in February 2016, after more than five years of upgrading work on KEKB, and successfully ended in June of the same year. This paper describes one major task of Phase-1 commissioning: beam scrubbing the surface of the beam pipes, to prepare them for a sufficiently long beam lifetime and low background noise in the next commissioning, when a new particle detector will be installed. The pressure rises per unit beam current (dP/dI [Pa A-1]) were continuously monitored, and the coefficient of photon-stimulated desorption (PSD), η [molecules photon-1], was evaluated in the arc sections. The value of η decreased steadily with the beam dose, as expected. For arc sections in the positron ring, where most of the beam pipes were newly fabricated, the decrease in η against the photon dose (D) was similar to that previously reported; that is: η ∝ D-0.5 ∼ 0.8. At high storage beam currents, the evolution of η was affected by gas desorption resulting from the multipacting of electrons-that is, the electron cloud effect (ECE), which is a phenomenon particular to high-intensity positron rings. For the arc sections in the electron ring, η also decreased smoothly with the photon dose D, approximately as ∝ D-0.8. Given that most of these beam pipes were reused from KEKB, the value of η was much lower than that of the positron ring, and also lower than that of the electron ring of KEKB from the early stages of D. This implies that the surface of the reused beam pipes remembered the conditions in the KEKB, which is a known memory effect. The results obtained for η are compared with those obtained in various other accelerators.

Industrial applications or electron beams; Aplicaciones industriales de la irradiacion como servicio

Energy Technology Data Exchange (ETDEWEB)

Martin, J. I.

2001-07-01

Industrial use of electron beams began in the 1950's with the crosslinking of polyethylene film and wire insulation. Today the number of electron beam Processing Systems installed for industrial applications throughout the world has grown to more than six hundred stations in over 35 countries. Total installed power is now approaching 40 megawatts (over 8 million tons of products per year). Electron beam is now utilized by many major industries including plastics, automotive, rubber goods, wire and cable, electrical insulation, semiconductor, medical, packaging, or pollution control. The principal effect of high-energy electrons is to produce ions in the materials treated, resulting in the liberation of orbital electrons. As a result, the original molecule is modified and the ree radicals combine to form new molecules with new chemical reactions or dis organisation od the DNA chains of living organisms (insects, fungus, microorganisms, etc.). (Author) 8 refs.

Single-Molecule Light-Sheet Imaging of Suspended T Cells.

Science.gov (United States)

Ponjavic, Aleks; McColl, James; Carr, Alexander R; Santos, Ana Mafalda; Kulenkampff, Klara; Lippert, Anna; Davis, Simon J; Klenerman, David; Lee, Steven F

2018-05-08

Adaptive immune responses are initiated by triggering of the T cell receptor. Single-molecule imaging based on total internal reflection fluorescence microscopy at coverslip/basal cell interfaces is commonly used to study this process. These experiments have suggested, unexpectedly, that the diffusional behavior and organization of signaling proteins and receptors may be constrained before activation. However, it is unclear to what extent the molecular behavior and cell state is affected by the imaging conditions, i.e., by the presence of a supporting surface. In this study, we implemented single-molecule light-sheet microscopy, which enables single receptors to be directly visualized at any plane in a cell to study protein dynamics and organization in live, resting T cells. The light sheet enabled the acquisition of high-quality single-molecule fluorescence images that were comparable to those of total internal reflection fluorescence microscopy. By comparing the apical and basal surfaces of surface-contacting T cells using single-molecule light-sheet microscopy, we found that most coated-glass surfaces and supported lipid bilayers profoundly affected the diffusion of membrane proteins (T cell receptor and CD45) and that all the surfaces induced calcium influx to various degrees. Our results suggest that, when studying resting T cells, surfaces are best avoided, which we achieve here by suspending cells in agarose. Copyright © 2018. Published by Elsevier Inc.

On the origin of field-aligned beams at the quasi-perpendicular bow shock: multi-spacecraft observations by Cluster

Directory of Open Access Journals (Sweden)

H. Kucharek

2004-07-01

Full Text Available Two distinct populations of reflected and accelerated ions are known to originate from quasi-perpendicular shocks, gyrating ions and reflected ion beams. Recent observations under such bow shock conditions with Cluster have shown strong evidence that both particle distributions appear to emerge from the same reflection process. In this paper the basic production mechanism of field-aligned beams has been investigated by using CLUSTER multi-spacecraft measurements. We have analyzed several quasi-perpendicular shocks with the Cluster Ion Spectrometry experiment (CIS and followed the spatial and temporal evolution of the reflected and transmitted ion populations across the shock. These observations show that the field-aligned beams most likely result from effective scattering in pitch angle during reflection in the shock ramp. Investigating a low Mach number shock, leakage of a fraction of the thermalized ion distribution in the downstream region does not appear to be the source as the volume in phase space occupied by beam ions is empty downstream of the shock ramp.

Continuous all-optical deceleration of molecular beams and demonstration with Rb atoms

Science.gov (United States)

Long, Xueping; Jayich, Andrew; Campbell, Wesley

2017-04-01

Ultracold samples of molecules are desirable for a variety of applications, such as many-body physics, precision measurement and quantum information science. However, the pursuit of ultracold molecules has achieved limited success: spontaneous emission into many different dark states makes it hard to optically decelerate molecules to trappable speed. We propose to address this problem with a general optical deceleration technique that exploits a pump-dump pulse pair from a mode-locked laser. A molecular beam is first excited by a counter-propagating ``pump'' pulse. The molecular beam is then driven back to the initial ground state by a co-propagating ``dump'' pulse via stimulated emission. The delay between the pump and dump pulse is set to be shorter than the excited state lifetimes in order to limit decays to dark states. We report progress benchmarking this stimulated force by accelerating a cold sample of neutral Rb atoms.

Performance polymeric concrete with synthetic fiber reinforcement against reflective cracking in rigid pavement overlay

International Nuclear Information System (INIS)

Khan, N.U.; Khan, B.

2012-01-01

Cement concrete pavements are used for heavy traffic loads throughout the world owing to its better and economical performance. Placing of a concrete overlay on the existing pavement is the most prevalent rehabilitating method for such pavements, however, the problem associated with the newly placed overlay is the occurrence of reflective cracking. This paper presents an assessment of the performance of polymeric concrete with synthetic fiber reinforcement against reflective cracking in an overlay system. The performance of polymeric concrete with synthetic fibers as an overlay material is measured in terms of the load-deflection, strain-deflection and load-strain behavior of beams of the polymeric concrete. For this purpose, five types of beams having different number of fiber wires and position are tested for flexure strength. Deflection/strains for each increment of load are recorded. In addition, cubes of plain concrete and of concrete with synthetic fiber needles were tested after 7 and 28 days for compressive strengths. Finite element models in ANSYS software for the beams have also been developed. Beams with greater number of longitudinal fiber wires displayed relatively better performance against deflection whilst beams with synthetic fiber needles showed better performance against strains. Thus, polymeric concrete overlay with fiber reinforcement will serve relatively better against occurrence of reflective cracking. (author)

Spectral simulations of polar diatomic molecules immersed in He clusters: application to the ICl (X) molecule

International Nuclear Information System (INIS)

Villarreal, P; Lara-Castells, M P de; Prosmiti, R; Delgado-Barrio, G; Lopez-Duran, D; Gianturco, F A; Jellinek, J

2007-01-01

A recently developed quantum-chemistry-like methodology to study molecules solvated in atomic clusters is applied to the ICl (iodine chloride) polar diatomic molecule immersed in clusters of He atoms. The atoms of the solvent clusters are treated as the 'electrons' and the solvated molecule as a structured 'nucleus' of the combined solvent-solute system. The helium-helium and helium-dopant interactions are represented by parametrized two-body and ab initio three-body potentials, respectively. The ground-state wavefunctions are used to compute the infrared (IR) spectra of the solvated molecule. In agreement with the experimental observations, the computed spectra exhibit considerable differences depending on whether the solvent cluster is comprised of bosonic ( 4 He) or fermionic ( 3 He) atoms. The source of these differences is attributed to the different spin-statistics of the solvent clusters. The bosonic versus fermionic nature of the solvent is reflected in the IR absorption selection rules. Only P and R branches with single state transitions appear in the spectrum when the molecule is solvated in a bosonic cluster. On the other hand, when the solvent represents a fermionic environment, quasi-degenerate multiplets of spin states contribute to each branch and, in addition, the Q-branch becomes also allowed. Combined, these two factors explain the more congested nature of the spectrum in the fermionic case

Quantum state specific reactant preparation in a molecular beam by rapid adiabatic passage

Science.gov (United States)

Chadwick, Helen; Hundt, P. Morten; van Reijzen, Maarten E.; Yoder, Bruce L.; Beck, Rainer D.

2014-01-01

Highly efficient preparation of molecules in a specific rovibrationally excited state for gas/surface reactivity measurements is achieved in a molecular beam using tunable infrared (IR) radiation from a single mode continuous wave optical parametric oscillator (cw-OPO). We demonstrate that with appropriate focusing of the IR radiation, molecules in the molecular beam crossing the fixed frequency IR field experience a Doppler tuning that can be adjusted to achieve complete population inversion of a two-level system by rapid adiabatic passage (RAP). A room temperature pyroelectric detector is used to monitor the excited fraction in the molecular beam and the population inversion is detected and quantified using IR bleaching by a second IR-OPO. The second OPO is also used for complete population transfer to an overtone or combination vibration via double resonance excitation using two spatially separated RAP processes.

Buildup of electrons with hot electron beam injection into a homogeneous magnetic field

International Nuclear Information System (INIS)

Bashko, V.A.; Krivoruchko, A.M.; Tarasov, I.K.

1989-01-01

The injection of the monoenergetic beam of electrons into the vacuum drift channel under the conditions when the beam current exceeds a certain threshold value involves a virtual cathode creation. The process of virtual cathode creation leads to an exchange of one-fluid movement of beam particles to three-fluid one corresponding to incident, reflected and passed through anticathode beam particles. For the monoenergetic beam case when the velocity spread Δv dr (v dr is the beam drift velocity), the beam instability was predicted in theory and was observed in experiment. Meanwhile, the injection in the drift space of the 'hot' beam having finite spread in velocities may be accompanied not only by the reflection of particles if their velocity v 1/2 (where φ is the electrostatic potential dip value, e and m are the electron charge and mass, respectively), but also the mutual Coulomb scattering of incident and reflected electrons. The scattering process leads in its turn to appearance of viscosity forces and to trapping of a part of beam electrons into the effective potential well formed by electrostatic potential dip and the viscous force potential. The interaction of travelling and trapped particles may occur even at the stage preceding the virtual electrode formation and it may influence the process of its appearance and also the current flow through the drift space. In this report there are described the experimental results on accumulation of electrons when electron beam propagates in vacuum and has a large spread in particle velocities Δv dr in the homogeneous longitudinal magnetic field when ω pe He where ω pe is the electron Langmuir frequency of beam electrons, ω He is the electron cyclotron frequency. (author) 6 refs., 2 figs

Reflection and transmission of full-vector X-waves normally incident on dielectric half spaces

KAUST Repository

Salem, Mohamed

2011-08-01

The reflection and transmission of full-vector X-Waves incident normally on a planar interface between two lossless dielectric half-spaces are investigated. Full-vector X-Waves are obtained by superimposing transverse electric and magnetic polarization components, which are derived from the scalar X-Wave solution. The analysis of transmission and reflection is carried out via a straightforward but yet effective method: First, the X-Wave is decomposed into vector Bessel beams via the Bessel-Fourier transform. Then, the reflection and transmission coefficients of the beams are obtained in the spectral domain. Finally, the transmitted and reflected X-Waves are obtained via the inverse Bessel-Fourier transform carried out on the X-wave spectrum weighted with the corresponding coefficient. © 2011 IEEE.

Proposed frustrated-total-reflection acoustic sensing method

International Nuclear Information System (INIS)

Hull, J.R.

1981-01-01

Modulation of electromagnetic energy transmission through a frustrated-total-reflection device by pressure-induced changes in the index of refraction is proposed for use as an acoustic detector. Maximum sensitivity occurs for angles of incidence near the critical angle. The minimum detectable pressure in air is limited by Brownian noise. Acoustic propagation losses and diffraction of the optical beam by the acoustic signal limit the minimum acoustic wavelength to lengths of the order of the spatial extent of the optical beam. The response time of the method is fast enough to follow individual acoustic waves

Molecular beam kinetics

International Nuclear Information System (INIS)

Behrens, R. Jr.

1975-11-01

The design of a crossed molecular beam ''supermachine'' for neutral--neutral collisions is discussed. The universal electron bombardment ionizer, mass filter, and ion detection system of the detector, the supersonic nozzle sources, the differential pumping arrangement for the sources and detector, the time-of-flight detection of scattered products, and the overall configuration of the apparatus are described. The elastic scattering of two systems, CH 4 + Ar and NH 3 + Ar, has been measured using the supermachine with two supersonic nozzle sources. The rainbow structure and the interference oscillations are seen in each system. The best fit to the data was found using a Morse--Spline--Van der Waals (MSV) potential. The three potential parameters epsilon, r/sub m/, and β were found to be 2.20(+-0.04) x 10 -14 ergs, 3.82(+-0.04)A, and 7.05 +- 0.20 for CH 4 + Ar, and 2.21(+-0.04) x 10 -14 ergs 3.93 (+-0.05)A, and 8.45 +- 0.30 for NH 3 + Ar. A new phenomenon in crossed molecular beams of condensation of a molecule on a cluster to form a complex was observed. A bromine molecule condensed on clusters of chlorine (Cl 2 )/sub chi/ and ammonia (NH 3 )/sub chi/. The value of chi for measurements in these experiments ranges from 7 to 40 for chlorine clusters and from 10 to 70 ammonia clusters

Many-beam effects in electron microscope images of lattice defects

International Nuclear Information System (INIS)

Izui, Kazuhiko; Nishida, Takahiko; Furuno, Shigemi; Otsu, Hitoshi

1974-01-01

Multi-beam effects in electron microscopic images were investigated. A computation program was developed on the basis of a matrix theory of the multi-beam effects. The matrix theory for a perfect crystal and an imperfect crystal is described, and expression for absorption coefficient is presented. The amplitude of electron wave penetrating through lattice defects is expressed by using scattering matrices which correspond to crystal slices. Calculation of extinction distance was performed, and compared with experimental results. In case of systematic reflection, the difference between two beams and from four to eight beams approximation was small, while a large effect was seen in case of accidental reflection. The intensity profile of bend contour was calculated for silicon and copper-aluminum alloy. Distance between submaxima becomes short with increase of thickness. The change in stacking fault fringes with diffraction condition was investigated. Samples were copper-aluminum alloy. Systematic behavior of the fringes was obtained, and the calculated results reproduced experimental ones. (Kato, T.)

Multiphoton dissociation of polyatomic molecules

International Nuclear Information System (INIS)

Schulz, P.A.

1979-10-01

The dynamics of infrared multiphoton excitation and dissociation of SF 6 was investigated under collision free conditions by a crossed laser-molecular beam method. In order to understand the excitation mechanism and to elucidate the requirements of laser intensity and energy fluence, a series of experiments were carried out to measure the dissociation yield dependences on energy fluence, vibrational temperature of SF 6 , the pulse duration of the CO 2 laser and the frequency in both one and two laser experiments. Translational energy distributions of the SF 5 dissociation product measured by time of flight and angular distributions and the dissociation lifetime of excited SF 6 as inferred from the observation of secondary dissociation of SF 5 into SF 4 and F during the laser pulse suggest that the dynamics of dissociation of excited molecules is dominated by complete energy randomization and rapid intramolecular energy transfer on a nanosecond timescale, and can be adequately described by RRKM theory. An improved phenomenological model including the initial intensity dependent excitation, a rate equation describing the absorption and stimulated emission of single photons, and the unimolecular dissociation of excited molecules is constructed based on available experimental results. The model shows that the energy fluence of the laser determines the excitation of molecules in the quasi-continuum and the excess energy with which molecules dissociate after the laser pulse. The role played by the laser intensity in multiphoton dissociation is more significant than just that of overcoming the intensity dependent absorption in the lowest levels. 63 references

Antarctic Surface Reflectivity Measurements from the ANITA-3 and HiCal-1 Experiments

Science.gov (United States)

Gorham, P. W.; Allison, P.; Banerjee, O.; Beatty, J. J.; Belov, K.; Besson, D. Z.; Binns, W. R.; Bugaev, V.; Cao, P.; Chen, C.; Chen, P.; Clem, J. M.; Connolly, A.; Dailey, B.; Dasgupta, P.; Deaconu, C.; Cremonesi, L.; Dowkontt, P. F.; Fox, B. D.; Gordon, J.; Hill, B.; Hupe, R.; Israel, M. H.; Jain, P.; Kowalski, J.; Lam, J.; Learned, J. G.; Liewer, K. M.; Liu, T. C.; Matsuno, S.; Miki, C.; Mottram, M.; Mulrey, K.; Nam, J.; Nichol, R. J.; Novikov, A.; Oberla, E.; Prohira, S.; Rauch, B. F.; Romero-Wolf, A.; Rotter, B.; Ratzlaff, K.; Russell, J.; Saltzberg, D.; Seckel, D.; Schoorlemmer, H.; Stafford, S.; Stockham, J.; Stockham, M.; Strutt, B.; Tatem, K.; Varner, G. S.; Vieregg, A. G.; Wissel, S. A.; Wu, F.; Young, R.

The primary science goal of the NASA-sponsored ANITA project is measurement of ultra-high energy neutrinos and cosmic rays, observed via radio-frequency signals resulting from a neutrino or cosmic ray interaction with terrestrial matter (e.g. atmospheric or ice molecules). Accurate inference of the energies of these cosmic rays requires understanding the transmission/reflection of radio wave signals across the ice-air boundary. Satellite-based measurements of Antarctic surface reflectivity, using a co-located transmitter and receiver, have been performed more-or-less continuously for the last few decades. Our comparison of four different reflectivity surveys, at frequencies ranging from 2 to 45GHz and at near-normal incidence, yield generally consistent maps of high versus low reflectivity, as a function of location, across Antarctica. Using the Sun as an RF source, and the ANITA-3 balloon borne radio-frequency antenna array as the RF receiver, we have also measured the surface reflectivity over the interval 200-1000MHz, at elevation angles of 12-30∘. Consistent with our previous measurement using ANITA-2, we find good agreement, within systematic errors (dominated by antenna beam width uncertainties) and across Antarctica, with the expected reflectivity as prescribed by the Fresnel equations. To probe low incidence angles, inaccessible to the Antarctic Solar technique and not probed by previous satellite surveys, a novel experimental approach (“HiCal-1”) was devised. Unlike previous measurements, HiCal-ANITA constitute a bi-static transmitter-receiver pair separated by hundreds of kilometers. Data taken with HiCal, between 200 and 600MHz shows a significant departure from the Fresnel equations, constant with frequency over that band, with the deficit increasing with obliquity of incidence, which we attribute to the combined effects of possible surface roughness, surface grain effects, radar clutter and/or shadowing of the reflection zone due to Earth

Ultrafast dynamics of electronically excited molecules and clusters

International Nuclear Information System (INIS)

Lietard, Aude

2014-01-01

This PhD thesis investigated the ultrafast dynamics of photo-chromic molecules and argon clusters in the gas phase at the femtosecond timescale. Pump-probe experiments are performed in a set-up which associates a versatile pulsed molecular beam coupled to a photoelectron/photoion velocity map imager (VMI) and a time-of-flight mass spectrometer (TOF-MS). Theses pump-probe experiments provides the temporal evolution of the electronic distribution for each system of interest. Besides, a modelization has been performed in order to characterize the density and the velocity distribution in the pulsed beam. Regarding the photo-chromic di-thienyl-ethene molecules, parallel electronic relaxation pathways were observed. This contrasts with the observation of sequential relaxation processes in most molecules studied so far. In the present case, the initial wave packet splits in two parts. One part is driven to the ground state at the femtosecond time scale through a conical intersection, and the second part remains for ps in the excited state and experiences oscillations in a suspended well. This study has shed light into the intrinsic dynamics of the molecules under study and a general relaxation mechanism has been proposed, which applies to the whole family of di-thienyl-ethene molecules whatever the state of matter (gas phase or solution) in which they have been investigated. Concerning argon clusters excited at about 14 eV, two behaviors of different time scale have been observed at different time scales. The first one occurs in the first picoseconds of the dynamics. It corresponds to the electronic relaxation of an excitonic state at a rate of 1 eV.ps -1 . The second phenomenon corresponds to the localization of the exciton on the excimer Ar 2 *. This phenomenon is observed 4-5 ps after the excitation. In this study, we also observed the ejection of excited argon atoms, addressing the lifetime of the delocalized excitonic state. This work provide additional informations

Atmospheric processes on ice nanoparticles in molecular beams

Directory of Open Access Journals (Sweden)

Michal eFárník

2014-02-01

Full Text Available This review summarizes some recent experiments with ice nanoparticles (large water clusters in molecular beams and outlines their atmospheric relevance: (1 Investigation of mixed water–nitric acid particles by means of the electron ionization and sodium doping combined with photoionization revealed the prominent role of HNO3 molecule as the condensation nuclei. (2 The uptake of atmospheric molecules by water ice nanoparticles has been studied, and the pickup cross sections for some molecules exceed significantly the geometrical sizes of the ice nanoparticles. (3 Photodissociation of hydrogen halides on water ice particles has been shown to proceed via excitation of acidically dissociated ion pair and subsequent biradical generation and H3O dissociation. The photodissociation of CF2Cl2 molecule in clusters is also mentioned. Possible atmospheric consequences of all these results are briefly discussed.

Proximity effect and Andreev reflection in single-C{sub 60} junctions

Energy Technology Data Exchange (ETDEWEB)

Brand, Jonathan; Neel, Nicolas; Kroeger, Joerg [Institut fuer Physik, Technische Universitaet Ilmenau, D-98693 Ilmenau (Germany)

2016-07-01

Single C{sub 60} molecules deposited on an ultrathin oxide film on Nb(110) were investigated using a low-temperature scanning tunnelling microscope. Spectroscopy of the differential conductance (dI/dV) in the tunnelling range indicates proximity-induced superconductivity in junctions comprising the oxide layer as well as single C{sub 60} molecules. Andreev reflection is enhanced upon controlled fabrication of tip-surface contacts. With decreasing electrode separation the Bardeen-Cooper-Schrieffer energy gap gradually evolves into a zero-bias peak in dI/dV spectra reflecting the spectroscopic signature of Andreev reflection. The current-voltage characteristics of the tunnelling and contact junctions are well described by the Blonder-Tinkham-Klapwijk theory. Our spectroscopic data evidence the influence of the electrodes' atomic-scale structure on electron transport across normal metal-superconductor interfaces.

Velocity distribution and dimer formation in a Na/Na2 beam

International Nuclear Information System (INIS)

Bergmann, K.; Hefter, U.; Hering, P.

1977-01-01

Using the TOF via optical pumping method and the Doppler-shifted laser induced emission described previously, the authors have measured the parallel and perpendicular velocity distribution respectively for Na atoms and Na 2 molecules in a variety of individual quantum states. In addition they monitored the flux of molecules in specific states while changing the stagnation pressure. In all cases a significant dependence on the internal energy of the molecules was found. The goal of these experiments is to improve understanding of the beam dynamics and the dimer formation process. (Auth.)

Generation of nanospikes via laser ablation of metals in liquid environment and their activity in surface-enhanced Raman scattering of organic molecules

Energy Technology Data Exchange (ETDEWEB)

Truong, S. Lau; Levi, G.; Bozon-Verduraz, F. [ITODYS, UMR-CNRS 7086, Universite Paris 7-Denis Diderot, 2, place Jussieu, 75251 Paris cedex 05 (France); Petrovskaya, A.V.; Simakin, A.V. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov street, 119991 Moscow (Russian Federation); Shafeev, G.A. [Wave Research Center of A.M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov street, 119991 Moscow (Russian Federation)], E-mail: shafeev@kapella.gpi.ru

2007-12-15

The formation of dense arrays of nanospikes occurs under laser ablation of bulk targets (Ag, Au, Ta, Ti) immersed in liquids such as water or ethanol. The average height of spikes is 50 nm and their density on the target amounts to 10{sup 10} cm{sup -2}. The effect is observed with sufficiently short laser pulses. In particular, either a 350 ps or a 90 ps Nd:YAG lasers are used in their fundamental harmonics. The nanospikes are characterized by UV-Visible reflection spectrometry and atomic force microscopy. The oscillations of electrons within nanospikes result in a permanent coloration of the surface and a modification of the optical reflection spectra of the metal. Scanning the laser beam along the metal surface allows its nanostructuring over extended areas ({approx}1 cm{sup 2}). The nanostructured Ag surface shows enhanced Raman scattering of acridine molecules at a concentration of 10{sup -5} M/l, whereas the initial Ag targets do not show any signal within the accuracy of measurements.

An Innovative Beam Halo Monitor system for the CMS experiment at the LHC: Design, Commissioning and First Beam Results

CERN Document Server

AUTHOR|(INSPIRE)INSPIRE-00344917; Dabrowski, Anne

The Compact Muon Solenoid (CMS) is a multi-purpose experiment situated at the Large Hadron Collider (LHC). The CMS has the mandate of searching new physics and making precise measurements of the already known mechanisms by using data produced by collisions of high-energy particles. To ensure high quality physics data taking, it is important to monitor and ensure the quality of the colliding particle beams. This thesis presents the research and design, the integration and the first commissioning results of a novel Beam Halo Monitor (BHM) that was designed and built for the CMS experiment. The BHM provides an online, bunch-by-bunch measurement of background particles created by interactions of the proton beam with residual gas molecules in the vacuum chamber or with collimator material upstream of the CMS, separately for each beam. The system consists of two arrays of twenty direction-sensitive detectors that are distributed azimuthally around the outer forward shielding of the CMS experiment. Each detector is ...

Design of collimating and rearrangement systems of laser diode array beam

Science.gov (United States)

Gao, Runmei; Fang, Tao; Fu, Rulian; Yao, Jianquan

2015-10-01

To improve the laser diode output beam quality, micro-cylindrical lens and the step-type lens combination are designed. The former is used to collimate beam in fast-axis direction, while the latter plays a role in the slow-axis of splitting and the rearrangement. The micro-column semi-elliptical lens is made with the drops of spherical zoom lensin electric field and with the help of the material properties of light-cured production, which can reduce the reflection of the front surface and total reflection loss of the after. The divergence angle in the fast axis is compressed to roughly the same as that in the slow-axis direction; Stepped lens splits compressed long strip beam in the slow axis, with parallelogram style of level equidistant and rearrange in the fast axis direction. The spot in the slow axis gets smaller and the spot becomes larger in the fast axis. At last divergence angle and the beam spot achieve balanced in the fast axis and slow axis, optical parameters BPP integrates approximate the same, and beam quality can be improved.

Design and analysis of metal-dielectric nonpolarizing beam splitters in a glass cube.

Science.gov (United States)

Shi, Jin Hui; Guan, Chun Ying; Wang, Zheng Ping

2009-06-20

A novel design of a 25-layer metal-dielectric nonpolarizing beam splitter in a cube is proposed by use of the optimization method and is theoretically investigated. The simulations of the reflectance and differential phases induced by reflection and transmission are presented. The simulation results reveal that both the amplitude and the phase characteristics of the nonpolarizing beam splitter could realize the design targets, the differences between the simulated and the target reflectance of 50% are less than 2%, and the differential phases are less than 3 degrees in the range of 530 nm-570 nm for both p and s components.

Generation and transportation of low-energy, high-current electron beams

International Nuclear Information System (INIS)

Ozur, G.E.; Proskurovskij, D.I.; Nazarov, D.S.

1996-01-01

Experimental data on the production of low-energy, high-current electron beams in a plasma-filled diode are presented. The highest beam energy density achieved is about 40 J/cm 2 , which makes it possible to treat materials in the mode of intense evaporation of the surface layer. It was shown that the use of a hollow cathode improves the beam homogeneity. The feasibility was demonstrated of the production of low-energy high-current electron beams in a gun with plasma anode based on the use of a reflective discharge. (author). 6 figs., 6 refs

Natural extracellular nanovesicles and photodynamic molecules: is there a future for drug delivery?

Science.gov (United States)

Kusuzaki, Katsuyuki; Matsubara, Takao; Murata, Hiroaki; Logozzi, Mariantonia; Iessi, Elisabetta; Di Raimo, Rossella; Carta, Fabrizio; Supuran, Claudiu T; Fais, Stefano

2017-12-01

Photodynamic molecules represent an alternative approach for cancer therapy for their property (i) to be photo-reactive; (ii) to be not-toxic for target cells in absence of light; (iii) to accumulate specifically into tumour tissues; (iv) to be activable by a light beam only at the tumour site and (v) to exert cytotoxic activity against tumour cells. However, to date their clinical use is limited by the side effects elicited by systemic administration. Extracellular vesicles are endogenous nanosized-carriers that have been recently introduced as a natural delivery system for therapeutic molecules. We have recently shown the ability of human exosomes to deliver photodynamic molecules. Therefore, this review focussed on extracellular vesicles as a novel strategy for the delivery of photodynamic molecules at cancer sites. This completely new approach may enhance the delivery and decrease the toxicity of photodynamic molecules, therefore, represent the future for photodynamic therapy for cancer treatment.

Reflected and diffuse ions backstreaming from the earth's bow shock 2. Origin

International Nuclear Information System (INIS)

Bonifazi, C.; Moreno, G.

1981-01-01

The morphology of the foreshock region and the origin of the 'reflected' and 'diffuse' ion populations are investigated for the first time through an extended statistical analysis. Data are supplied by the solar wind experiment on the satellite ISEE 2 in the period November 5 to December 20, 1977. It is confirmed, on a statistical basis, that quasi-perpendicular shock structures generate beams of reflected ions which propagate along the interplanetary magnetic field lines against the incoming solar wind. Diffuse ions are at least in part originated by the disruption of the reflected beams due to some plasma instability, having a growth time of the order of a few tens of seconds. A preliminary energy balance appears to be consistent with the proposed picture of the phenomena occurring in the foreshock region

Investigation on Single-Molecule Junctions Based on Current–Voltage Characteristics

Directory of Open Access Journals (Sweden)

Yuji Isshiki

2018-02-01

Full Text Available The relationship between the current through an electronic device and the voltage across its terminals is a current–voltage characteristic (I–V that determine basic device performance. Currently, I–V measurement on a single-molecule scale can be performed using break junction technique, where a single molecule junction can be prepared by trapping a single molecule into a nanogap between metal electrodes. The single-molecule I–Vs provide not only the device performance, but also reflect information on energy dispersion of the electronic state and the electron-molecular vibration coupling in the junction. This mini review focuses on recent representative studies on I–Vs of the single molecule junctions that cover investigation on the single-molecule diode property, the molecular vibration, and the electronic structure as a form of transmission probability, and electronic density of states, including the spin state of the single-molecule junctions. In addition, thermoelectronic measurements based on I–Vs and identification of the charged carriers (i.e., electrons or holes are presented. The analysis in the single-molecule I–Vs provides fundamental and essential information for a better understanding of the single-molecule science, and puts the single molecule junction to more practical use in molecular devices.

The Crossed-Beam Scattering Method in Studies of Ion-Molecule Reaction Dynamics

Czech Academy of Sciences Publication Activity Database

Herman, Zdeněk

2001-01-01

Roč. 212, - (2001), s. 413-443 ISSN 1387-3806 R&D Projects: GA ČR GA203/00/0632 Institutional research plan: CEZ:AV0Z4040901 Keywords : ion-molecule reaction dynamics * ion scattering * experimental methods Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.176, year: 2001

Electron beam induced fluorescence measurements of the degree of hydrogen dissociation in hydrogen plasmas

NARCIS (Netherlands)

Smit, C.; Brussaard, G.J.H.; de Beer, E.C.M.; Schram, D.C.; Sanden, van de M.C.M.

2004-01-01

The degree of dissociation of hydrogen in a hydrogen plasma has been measured using electron beam induced fluorescence. A 20 kV, 1 mA electron beam excites both the ground state H atom and H2 molecule into atomic hydrogen in an excited state. From the resulting fluorescence the degree of

Timoshenko beam element with anisotropic cross-sectional properties

DEFF Research Database (Denmark)

Stäblein, Alexander; Hansen, Morten Hartvig

2016-01-01

Beam models are used for the aeroelastic time and frequency domain analysis of wind turbines due to their computational efficiency. Many current aeroelastic tools for the analysis of wind turbines rely on Timoshenko beam elements with classical crosssectional properties (EA, EI, etc.). Those cross......-sectional properties do not reflect the various couplings arising from the anisotropic behaviour of the blade material. A twonoded, three-dimensional Timoshenko beam element was therefore extended to allow for anisotropic cross-sectional properties. For an uncoupled beam, the resulting shape functions are identical...... to the original formulation. The new element was implemented into a co-rotational formulation and validated against natural frequencies and several static load cases of previous works....

Experimentation with low-energy positron beams

International Nuclear Information System (INIS)

Mills, A.P. Jr.

1983-01-01

The capability of studying the interactions of positrons with surfaces has recently been exploited by using ultra-high-vacuum techniques. The result has been a new understanding of how positrons interact with surfaces and because of this we are now able to make much stronger fluxes of slow positrons. The higher beam strengths in turn are opening up new possibilities for experimentation on surfaces and solids and for studying the atomic physics of positronium and positron-molecule scattering at low energies. The lectures are intended to review some of the history of this subject and to outline the present state of our knowledge of experimentation with low-energy positron beams. (orig./TW)

Investigation of omnidirectional reflection band in ZnTe/ZnSe distributed Bragg reflector

Energy Technology Data Exchange (ETDEWEB)

Huang, Ying-Shin [Department of Electrical Engineering, National Taiwan Ocean University, Keelung 20224, Taiwan (China); Hu, Sheng-Yao [Department of Digital Technology Design, Tungfang Design University, Kaohsiung 82941, Taiwan (China); Lee, Yueh-Chien, E-mail: jacklee@mail.tnu.edu.tw [Department of Electronic Engineering, Tungnan University, New Taipei City 22202, Taiwan (China); Chang, Chung-Cheng; Tiong, Kwong-Kau [Department of Electrical Engineering, National Taiwan Ocean University, Keelung 20224, Taiwan (China); Shen, Ji-Lin [Department of Physics, Chung Yuan Christian University, Chung-Li 32023, Taiwan (China); Chou, Wu-Ching [Department of Electrophysics, National Chiao Tung University, Hsinchu 30010, Taiwan (China)

2015-11-15

We report the characteristics of reflectance spectra of the 15- and 20-period ZnTe/ZnSe distributed Bragg reflector grown on GaAs (001) substrates by molecular beam epitaxy. The reflectance spectra measured at various incident angles and polarizations were investigated by the theoretical curves simulated using transfer matrix method. The wavelength variation of the refractive indices described by Sellmeier equation and random thickness model were also considered for the interpretation of the experimentally observed curves. An omnidirectional reflection range defined from the edge of incident-angle-dependent reflection band with TE and TM polarizations is about 15 nm, and is consistent with the observed experimental curves. The results showed that the selected ZnTe and ZnSe materials are suitable for constructing multilayer structures having omnidirectional reflection band. - Highlights: • ZnTe/ZnSe distributed Bragg reflector grown by molecular beam epitaxy. • The reflectance spectra are measured at various incidence angles and polarizations. • The theoretical curves are considered by Sellmeier and random thickness models. • An observed omnidirectional reflection range in ZnTe/ZnSe DBR is about 15 nm.

Structural biology facilities at Brookhaven National Laboratory`s high flux beam reactor

Energy Technology Data Exchange (ETDEWEB)

Korszun, Z.R.; Saxena, A.M.; Schneider, D.K. [Brookhaven National Laboratory, Upton, NY (United States)

1994-12-31

The techniques for determining the structure of biological molecules and larger biological assemblies depend on the extent of order in the particular system. At the High Flux Beam Reactor at the Brookhaven National Laboratory, the Biology Department operates three beam lines dedicated to biological structure studies. These beam lines span the resolution range from approximately 700{Angstrom} to approximately 1.5{Angstrom} and are designed to perform structural studies on a wide range of biological systems. Beam line H3A is dedicated to single crystal diffraction studies of macromolecules, while beam line H3B is designed to study diffraction from partially ordered systems such as biological membranes. Beam line H9B is located on the cold source and is designed for small angle scattering experiments on oligomeric biological systems.

Thin transparent film characterization by photothermal reflectance (abstract)

Science.gov (United States)

Li Voti, R.; Wright, O. B.; Matsuda, O.; Larciprete, M. C.; Sibilia, C.; Bertolotti, M.

2003-01-01

Photothermal reflectance methods have been intensively applied to the nondestructive testing of opaque thin films [D. P. Almond and P. M. Patel, Photothermal Science and Techniques (Chapman and Hall, London, 1996); C. Bento and D. P. Almond, Meas. Sci. Technol. 6, 1022 (1995); J. Opsal, A. Rosencwaig, and D. Willenborg, Appl. Opt. 22, 3169 (1983)]. The basic principle is based on thermal wave interferometry: the opaque specimen is illuminated by a laser beam, periodically chopped at the frequency f, so as to generate a plane thermal wave in the surface region. This wave propagates in the film, approaches the rear interface (film-bulk), is partially reflected back, reaches the front surface, is again partially reflected back and so on, giving rise to thermal wave interference. A consequence of this interference is that the surface temperature may be enhanced (constructive interference) or reduced (destructive interference) by simply scanning the frequency f (that is, the thermal diffusion length μ=√D/πf ), so as to observe damped oscillations as a function of f; in practice only the first oscillation may be clearly resolved and used to measure either the film thickness d or the film thermal diffusivity D, and this situation occurs when μ≈d. In general, photothermal reflectance does not measure directly the surface temperature variation, but rather a directly related signal determined by the thermo-optic coefficients and the sample geometry; for detection it is common to monitor the optical reflectivity variation of a probe beam normally incident on the sample. If the thin film is partially transparent to the probe, the theory becomes more difficult [O. Matsuda and O. B. Wright, J. Opt. Soc. Am. B (in press)] and one should consider the probe beam multiple reflections in the thin film. The probe modulation is optically inhomogeneous due to the temperature-induced changes in refractive index. Although in the past the complexity of the analysis has impeded

Parasitic helminths: a pharmacopeia of anti-inflammatory molecules.

Science.gov (United States)

Johnston, M J G; MacDonald, J A; McKay, D M

2009-02-01

Infection with parasitic helminths takes a heavy toll on the health and well-being of humans and their domestic livestock, concomitantly resulting in major economic losses. Analyses have consistently revealed bioactive molecules in extracts of helminths or in their excretory/secretory products that modulate the immune response of the host. It is our view that parasitic helminths are an untapped source of immunomodulatory substances that, in pure form, could become new drugs (or models for drug design) to treat disease. Here, we illustrate the range of immunomodulatory molecules in selected parasitic trematodes, cestodes and nematodes, their impact on the immune cells in the host and how the host may recognize these molecules. There are many examples of the partial characterization of helminth-derived immunomodulatory molecules, but these have not yet translated into new drugs, reflecting the difficulty of isolating and fully characterizing proteins, glycoproteins and lipid-based molecules from small amounts of parasite material. However, this should not deter the investigator, since analytical techniques are now being used to accrue considerable structural information on parasite-derived molecules, even when only minute quantities of tissue are available. With the introduction of methodologies to purify and structurally-characterize molecules from small amounts of tissue and the application of high throughput immunological assays, one would predict that an assessment of parasitic helminths will yield a variety of novel drug candidates in the coming years.

Electron beam fluorescence spectrometry of internal state populations in nozzle beams of nitrogen and nitrogen/rare gas mixtures

International Nuclear Information System (INIS)

Faubel, M.; Weiner, E.R.

1981-01-01

Rotational level populations of N 2 were measured downstream from the skimmer in beams of pure N 2 and in mixtures of N 2 with He, Ne, and Ar expanded from room temperature nozzles. The range of p 0 D was from 5 to 50 Torr cm. The formation of dimers and higher condensates of beam species was monitored during the runs. The effect of condensation energy release on rotational populations and parallel temperatures was readily observed. Two different methods for evaluating the rotational population distributions were compared. One method is based on a dipole-excitation model and the other on an excitation matrix obtained empirically. Neither method proved clearly superior. Both methods indicated nonequilibrium rotational populations for all of our room temperature nozzle expansion conditions. Much of the nonequilibrium character appears to be due to the behavior of the K = 2 and K = 4 levels, which may be accounted for in terms of the rotational energy level spacing. In particular, the overpopulation of the K = 4 level is explained by a near-resonant transfer of rotational energy between molecules in the K = 6 and K = 0 states, to give two molecules in the K = 4 state. Rotational and vibrational temperatures were determined for pure N 2 beams from nozzles heated up to 1700 0 K. The heated nozzle experiments indicated a 40% increase in the rotational collision number between 300 and 1700 0 K

Controlling translational motion of neutral molecules in inhomogeneous electric fields

International Nuclear Information System (INIS)

Yamakita, Yoshihiro

2006-01-01

Hydrogen molecules are excited to Rydberg states with n=16, 17 in the presence of inhomogeneous field of an electric dipole by a vacuum ultraviolet-ultraviolet double resonance scheme. The large dipole moment produced in Stark eigenstates leads to strong forces on the molecules in the inhomogeneous electric field. Deflection and deceleration are demonstrated for a pulsed supersonic beam containing the H 2 molecules in the n=16, 17, N + =2, M J =0 Rydberg states. The Rydberg states are found to survive for over 100 μs after the dipole field is switched off. The Rydberg states have a special stability with respect to decay by predissociation. Complete deceleration to the zero mean velocity is numerically demonstrated for H 2 molecules in the higher linear low-field-seeking n=16, M J =0 Rydberg states by using a symplectic integrator of the fourth order. The calculations show that the initial velocity of 900 ms -1 with translational temperature 1 K is decelerated to 0 ms -1 with 13 mK. (author)

Single-Molecule Analysis for RISC Assembly and Target Cleavage.

Science.gov (United States)

Sasaki, Hiroshi M; Tadakuma, Hisashi; Tomari, Yukihide

2018-01-01

RNA-induced silencing complex (RISC) is a small RNA-protein complex that mediates silencing of complementary target RNAs. Biochemistry has been successfully used to characterize the molecular mechanism of RISC assembly and function for nearly two decades. However, further dissection of intermediate states during the reactions has been warranted to fill in the gaps in our understanding of RNA silencing mechanisms. Single-molecule analysis with total internal reflection fluorescence (TIRF) microscopy is a powerful imaging-based approach to interrogate complex formation and dynamics at the individual molecule level with high sensitivity. Combining this technique with our recently established in vitro reconstitution system of fly Ago2-RISC, we have developed a single-molecule observation system for RISC assembly. In this chapter, we summarize the detailed protocol for single-molecule analysis of chaperone-assisted assembly of fly Ago2-RISC as well as its target cleavage reaction.

Intense positron beam and its application to surface science

International Nuclear Information System (INIS)

Ito, Y.; Hirose, M.; Kanazawa, I.; Sueoka, O.; Takamura, S.; Okada, S.

1992-01-01

Intense pulsed slow positron beam has been produced using the 100 MeV electron LINAC of JAERI · Tokai. In order to use the beam for surface studies such as positron diffraction and positron microscopy, it was transferred from the solenoid magnetic field to field free region and then was brightness-enhanced. The beam size was reduced from 10 mmφ (in the magnetic field) to 0.5 mmφ after two stages of re-moderation. Using the intense brightness-enhanced positron beam we have observed for the first time RHEPD (Reflection High-Energy Positron Diffraction) patterns. A design of re-emission positron microscopy is also described. (author)

Closely spaced mirror pair for reshaping and homogenizing pump beams in laser amplifiers

International Nuclear Information System (INIS)

Bass, I.L.

1992-12-01

Channeling a laser beam by multiple reflections between two closely-spaced, parallel or nearly parallel mirrors, serves to reshape and homogenize the beam at the output gap between the mirrors. Application of this device to improve the spatial overlap of a copper laser pump beam with the signal beam in a dye laser amplifier is described. This technique has been applied to the AVLIS program at the Lawrence Livermore National Laboratory

Grazing incidence beam expander

Energy Technology Data Exchange (ETDEWEB)

Akkapeddi, P.R.; Glenn, P.; Fuschetto, A.; Appert, Q.; Viswanathan, V.K.

1985-01-01

A Grazing Incidence Beam Expander (GIBE) telescope is being designed and fabricated to be used as an equivalent end mirror in a long laser resonator cavity. The design requirements for this GIBE flow down from a generic Free Electron Laser (FEL) resonator. The nature of the FEL gain volume (a thin, pencil-like, on-axis region) dictates that the output beam be very small. Such a thin beam with the high power levels characteristic of FELs would have to travel perhaps hundreds of meters or more before expanding enough to allow reflection from cooled mirrors. A GIBE, on the other hand, would allow placing these optics closer to the gain region and thus reduces the cavity lengths substantially. Results are presented relating to optical and mechanical design, alignment sensitivity analysis, radius of curvature analysis, laser cavity stability analysis of a linear stable concentric laser cavity with a GIBE. Fabrication details of the GIBE are also given.

OCCURRENCE OF ACCELERATING FIELD, FORMATION AND DYNAMICS OF RELATIVISTIC ELECTRON BEAM NEAR JUPITER

Directory of Open Access Journals (Sweden)

V. I. Maslov

2018-06-01

Full Text Available The possible dynamics of the electron beam, formed in the vicinity of Io, the natural satellite of Jupiter, and injected toward Jupiter, has been investigated analytically. When a beam penetrates the Jupiter plasma to a certain depth, the beam-plasma instability can be developed. In this case, the distribution function of electrons is expanded additionally by excited oscillations. These electrons, when their energy is of order of a required certain value, cause UV polar light. For closing of a current, the formation of a double electric layer is necessary. The necessary parameters and conditions for the formation of a double layer with a large jump of an electric potential at a certain height have been formulated, its properties, stability, behavior over time and beam reflection in its field for closing of a current have been described. Reflection of the beam can lead to its vortex dynamics.

Charged particle beams for radiobiology at RARAF

International Nuclear Information System (INIS)

Colvett, R.D.; Rohrig, N.; Marino, S.A.

1977-01-01

(1) The extent to which the internal structure of a molecule might affect the separation of its constituent atoms after the molecule dissociates was investigated. Scattered intensity vs. lateral distance is shown (at 46 cm) for beams of 1.25-MeV monatomic deuterons, 2.5-MeV diatomic deuterons, and 3.75-MeV triatomic deuterons. It was found that the three species of ions have essentially indistinguishable scattering parameters; i.e., molecular effects are negligible. (2) Representative LET spectra are shown for deuterons of 2.2, 1.9, and 1.7 MeV and 3 He of 6.2 MeV. 3 figures

X-ray-ultraviolet beam splitters for the Michelson interferometer

International Nuclear Information System (INIS)

Delmotte, Franck; Ravet, Marie-Francoise; Bridou, Francoise; Varniere, Francoise; Zeitoun, Philippe; Hubert, Sebastien; Vanbostal, Laurent; Soullie, Gerard

2002-01-01

With the aim of realizing a Michelson interferometer working at 13.9 nm, we have developed a symmetrical beam splitter with multilayers deposited on the front and back sides of a silicon nitride membrane. On the basis of the experimental optical properties of the membrane, simulations have been performed to define the multilayer structure that provides the highest reflectivity-transmission product. Optimized Mo-Si multilayers have been successfully deposited on both sides of the membrane by use of the ion-beam sputtering technique, with a thickness-period reproducibility of 0.1 nm. Measurements by means of synchrotron radiation at 13.9 nm and at an angle of 45 deg. provide a reflectivity of 14.2% and a transmission of 15.2% for a 60% s-polarized light, close to the simulated values. Such a beam splitter has been used for x-ray laser Michelson interferometry at 13.9 nm. The first interferogram is discussed

X-ray-ultraviolet beam splitters for the Michelson interferometer.

Science.gov (United States)

Delmotte, Franck; Ravet, Marie-Françoise; Bridou, Françoise; Varnière, Françoise; Zeitoun, Philippe; Hubert, Sébastien; Vanbostal, Laurent; Soullie, Gérard

2002-10-01

With the aim of realizing a Michelson interferometer working at 13.9 nm, we have developed a symmetrical beam splitter with multilayers deposited on the front and back sides of a silicon nitride membrane. On the basis of the experimental optical properties of the membrane, simulations have been performed to define the multilayer structure that provides the highest reflectivity-transmission product. Optimized Mo-Si multilayers have been successfully deposited on both sides of t he membrane by use of the ion-beam sputtering technique, with a thickness-period reproducibility of 0.1 nm. Measurements by means of synchrotron radiation at 13.9 nm and at an angle of 45 degrees provide a reflectivity of 14.2% and a transmission of 15.2% for a 60% s-polarized light, close to the simulated values. Such a beam splitter has been used for x-ray laser Michelson interferometry at 13.9 nm. The first interferogram is discussed.

Dynamics of harmonic generation in atoms and molecules

International Nuclear Information System (INIS)

Boutu, W.

2007-09-01

Harmonics are generated when an ultra-short laser impulse with an energy of 10 14 W/cm 2 is focused on a gas jet. A radiation in the UV X range is then emitted in the direction of the incident laser beam. This radiation has a periodical spectral structure composed of odd harmonics of the fundamental frequency. The first part of this work is dedicated to the optimization of the harmonic radiation. We have studied an alternative and cheaper solution to the flexible mirror, we have used a set of concentric phase plates in order to control the spatial phase of the beam and create an enlarged square profile near the focusing spot. We show how different parameters like phase shift or luminous-flux density or jet position have an impact on the harmonic signal. This second part of this work deals with the generation of high order harmonics in N 2 and CO 2 molecules. The experimental setting is based on the RABITT method (reconstruction of the atto-second burst by interference of 2-photon transitions). We have observed the presence of a spectral minimum linked to a phenomena of quantum interferences between the molecule and the electron wave packet. Moreover, a shift in the spectral phase appears at the place of the interference. (A.C.)

Non-mechanical optical path switching and its application to dual beam spectroscopy including gas filter correlation radiometry

Science.gov (United States)

Sachse, Glen W. (Inventor); Wang, Liang-Guo (Inventor)

1992-01-01

A non-mechanical optical switch is developed for alternately switching a monochromatic or quasi-monochromatic light beam along two optical paths. A polarizer polarizes light into a single, e.g., vertical component which is then rapidly modulated into vertical and horizontal components by a polarization modulator. A polarization beam splitter then reflects one of these components along one path and transmits the other along the second path. In the specific application of gas filter correlation radiometry, one path is directed through a vacuum cell and one path is directed through a gas correlation cell containing a desired gas. Reflecting mirrors cause these two paths to intersect at a second polarization beam splitter which reflects one component and transmits the other to recombine them into a polarization modulated beam which can be detected by an appropriate single sensor.

Radiation produced by electrons incident on molecules

International Nuclear Information System (INIS)

Moehlman, G.R.

1977-01-01

The work described in this thesis deals with light intensity measurements of emission spectra (1850-9000 A) produced by a continuous or pulsed beam of monoenergetic electrons (0 - 2000 eV) incident on a variety of molecular gases like H 2 , D 2 , H 2 O, HCl, NH 3 and several hydrocarbons. The emission spectra are dominated by fluorescence from excited fragments produced via dissociative excitation, besides fluorescence from excited parent molecules themselves. The experimental results thus obtained are expressed in terms of emission cross sections and lifetimes

Numerical Simulations for the Beam-Induced Electron Cloud in the LHC Beam Screen

CERN Document Server

Brüning, Oliver Sim

1998-01-01

The following work summarises simulation results obtained at CERN for the beam-induced electron cloud and looks at possible cures for the heat load in the LHC beam screen. The synchrotron radiation in the LHC creates a continuous flow of photoelectrons. These electrons are accelerated by the electric field of the bunch and hit the vacuum chamber on the opposite side of the beam pipe where they crea te secondary electrons which are again accelerated by the next bunch. For a large secondary emission yield the above mechanism leads to an exponential growth of the electron cloud which is limited by space charge forces. The simulations use a two-dimensional mesh for the space charge calculations and include the effect of image charges on the vacuum chamber wall. Depending on the quantum yield for the production of photoelectrons, the secondary emission yield and the reflectivity, the heat load can vary from 0.1 W/m to more than 15 W/m.

Generation and transportation of low-energy, high-current electron beams

Energy Technology Data Exchange (ETDEWEB)

Ozur, G E; Proskurovskij, D I; Nazarov, D S [Russian Academy of Sciences, Tomsk (Russian Federation). Institute of High Current Electronics

1997-12-31

Experimental data on the production of low-energy, high-current electron beams in a plasma-filled diode are presented. The highest beam energy density achieved is about 40 J/cm{sup 2}, which makes it possible to treat materials in the mode of intense evaporation of the surface layer. It was shown that the use of a hollow cathode improves the beam homogeneity. The feasibility was demonstrated of the production of low-energy high-current electron beams in a gun with plasma anode based on the use of a reflective discharge. (author). 6 figs., 6 refs.

A fiber-coupled displacement measuring interferometer for determination of the posture of a reflective surface

International Nuclear Information System (INIS)

Mao, Shuai; Hu, Peng-Cheng; Ding, Xue-Mei; Tan, Jiu-Bin

2016-01-01

A fiber-coupled displacement measuring interferometer capable of determining of the posture of a reflective surface of a measuring mirror is proposed. The newly constructed instrument combines fiber-coupled displacement and angular measurement technologies. The proposed interferometer has advantages of both the fiber-coupled and the spatially beam-separated interferometer. A portable dual-position sensitive detector (PSD)-based unit within this proposed interferometer measures the parallelism of the two source beams to guide the fiber-coupling adjustment. The portable dual PSD-based unit measures not only the pitch and yaw of the retro-reflector but also measures the posture of the reflective surface. The experimental results of displacement calibration show that the deviations between the proposed interferometer and a reference one, Agilent 5530, at two different common beam directions are both less than ±35 nm, thus verifying the effectiveness of the beam parallelism measurement. The experimental results of angular calibration show that deviations of pitch and yaw with the auto-collimator (as a reference) are less than ±2 arc sec, thus proving the proposed interferometer’s effectiveness for determination of the posture of a reflective surface.

Application of Zeeman spatial beam-splitting in polarized neutron reflectometry

OpenAIRE

Kozhevnikov, S. V.; Ignatovich, V. K.; Radu, F.

2017-01-01

Neutron Zeeman spatial beam-splitting is considered at reflection from magnetically noncollinear films. Two applications of Zeeman beam-splitting phenomenon in polarized neutron reflectometry are discussed. One is the construction of polarizing devices with high polarizing efficiency. Another one is the investigations of magnetically noncollinear films with low spin-flip probability. Experimental results are presented for illustration.

Morphological change of self-organized protrusions of fluoropolymer surface by ion beam irradiation

International Nuclear Information System (INIS)

Kitamura, Akane; Kobayashi, Tomohiro; Satoh, Takahiro; Koka, Masashi; Kamiya, Tomihiro; Suzuki, Akihiro; Terai, Takayuki

2013-01-01

Polytetrafluoroethylene (PTFE) and fluorinated ethylene propylene (FEP) are typical fluoropolymers displaying several desirable technological properties such as electrical insulation and high chemical resistance. When their surfaces are irradiated with ion beams, dense micro-protrusions formed after the emergence and spread of micropores across the entire irradiated area, allowing culture cells to spread on the top of the protrusions. In this study, we investigate the morphological changes introduced in the fluoropolymer surfaces by ion beams as the energy of the beams is increased. When an FEP sample was irradiated with a nitrogen ion beam with an energy of less than 350 keV at 1.0 μA/cm 2 , protrusions were formed with a density between 2 × 10 7 /cm 2 and 2 × 10 8 /cm 2 . However, at energies higher than 350 keV, the protrusions became sparse, and the density dropped to 5 × 10 2 /cm 2 . Protrusions appeared sporadically during irradiation at high energies, and the top of the protrusions appeared as spots inside the sample, which were difficult to etch and became elongated as the erosion of the surface progressed. Erosion was caused by sputtering of FEP molecules and evaporation at notably elevated temperatures on the surface. Analysis based on attenuated total reflectance/Fourier transform infrared spectroscopy showed the presence of C=C bonds as well as –COOH, –C=O, and –OH bonds on all irradiated samples. Their concentration on the surface densely covered with micro-protrusions was higher than that on the surface with sparse protrusions after irradiation at energies exceeding 350 keV. Thus, we determined a suitable range for the ion energy for creating FEP surfaces densely covered with protrusions

Transient beam loading in electron-positron storage rings

International Nuclear Information System (INIS)

Wilson, P.B.

1978-01-01

In this note the fundamental of transient beam loading in electron-positron storage rings will be reviewed. The notation, and some of the material, has been introduced previously. The present note is, however, more tutorial in nature, and in addition the analysis is extended to include the transient behaviour of the cavity fields and reflected power between bunch passages. Since we are not bound here by the rigid space limitations of a paper for publication, an attempt is made to give a reasonably coherent and complete discussion of transient beam loading that can hopefully be followed even by the uninitiated. The discussion begins with a consideration of the beam-cavity interaction in the ''single-pass'' limit. In this limit it is assumed that the fields induced in the cavity by the passage of a bunch have decayed essentially to zero by the time the next bunch has arrived. The problem of the maximum energy that can be extracted from a cavity by a bunch is given particular attention, since this subject seems to be the source of some confusion. The analysis is then extended to the ''multiple-pass'' case, where the beam-induced fields do not decay to zero between bunches, and to a detailed consideration of the transient variation of cavity fields and reflected power. The note concludes with a brief discussion of the effect of transient beam loading on quantum lifetime

Polarization-Independent Electrically Tunable Holographic Polymer Dispersed Liquid Crystals Grating Doped with Chiral Molecules

Directory of Open Access Journals (Sweden)

Hui LI

2017-08-01

Full Text Available This study proposes a holographic grating made of polymer dispersed liquid crystal (PDLC, with a small amount of chiral molecules doped into PDLC material. The major advantage of this grating is that it is independent of light polarization. This characteristic was verified by applying the interference beam intensity of a He-Cd laser at 150 mW/cm2, with an incidence angle between the two interference beams of 24°, for an irradiation curing duration of 120 s. The observed periodic structure of the grating is consistent with the theoretical value. As chiral molecules are doped, nematic-LC experiences a phase-change in the grating. However, the electro-optical features are only slightly affected. This proposed grating has greatly potential in 3D imaging because of its polarization-independent feature.DOI: http://dx.doi.org/10.5755/j01.ms.23.2.16312

Molecular beam studies of reaction dynamics

International Nuclear Information System (INIS)

Lee, Yuan T.

1991-03-01

The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation

Molecular beam studies of reaction dynamics

Energy Technology Data Exchange (ETDEWEB)

Lee, Y.T. [Lawrence Berkeley Laboratory, CA (United States)

1993-12-01

The major thrust of this research project is to elucidate detailed dynamics of simple elementary reactions that are theoretically important and to unravel the mechanism of complex chemical reactions or photochemical processes that play important roles in many macroscopic processes. Molecular beams of reactants are used to study individual reactive encounters between molecules or to monitor photodissociation events in a collision-free environment. Most of the information is derived from measurement of the product fragment energy, angular, and state distributions. Recent activities are centered on the mechanisms of elementary chemical reactions involving oxygen atoms with unsaturated hydrocarbons, the dynamics of endothermic substitution reactions, the dependence of the chemical reactivity of electronically excited atoms on the alignment of excited orbitals, the primary photochemical processes of polyatomic molecules, intramolecular energy transfer of chemically activated and locally excited molecules, the energetics of free radicals that are important to combustion processes, the infrared-absorption spectra of carbonium ions and hydrated hydronium ions, and bond-selective photodissociation through electric excitation.

X-ray pencil beam facility for optics characterization

Science.gov (United States)

Krumrey, Michael; Cibik, Levent; Müller, Peter; Bavdaz, Marcos; Wille, Eric; Ackermann, Marcelo; Collon, Maximilien J.

2010-07-01

The Physikalisch-Technische Bundesanstalt (PTB) has used synchrotron radiation for the characterization of optics and detectors for astrophysical X-ray telescopes for more than 20 years. At a dedicated beamline at BESSY II, a monochromatic pencil beam is used by ESA and cosine Research since the end of 2005 for the characterization of novel silicon pore optics, currently under development for the International X-ray Observatory (IXO). At this beamline, a photon energy of 2.8 keV is selected by a Si channel-cut monochromator. Two apertures at distances of 12.2 m and 30.5 m from the dipole source form a pencil beam with a typical diameter of 100 μm and a divergence below 1". The optics to be investigated is placed in a vacuum chamber on a hexapod, the angular positioning is controlled by means of autocollimators to below 1". The reflected beam is registered at 5 m distance from the optics with a CCD-based camera system. This contribution presents design and performance of the upgrade of this beamline to cope with the updated design for IXO. The distance between optics and detector can now be 20 m. For double reflection from an X-ray Optical Unit (XOU) and incidence angles up to 1.4°, this corresponds to a vertical translation of the camera by 2 m. To achieve high reflectance at this angle even with uncoated silicon, a lower photon energy of 1 keV is available from a pair of W/B4C multilayers. For coated optics, a high energy option can provide a pencil beam of 7.6 keV radiation.

Simulation of the development and interaction of instabilities in a relativistic electron beam under variation of the beam wall thickness

Energy Technology Data Exchange (ETDEWEB)

Badarin, A. A.; Kurkin, S. A. [Saratov State University (Russian Federation); Koronovskii, A. A. [Yuri Gagarin State Technical University (Russian Federation); Rak, A. O. [Belorussian State University of Informatics and Radioelectronics (Belarus); Hramov, A. E., E-mail: hramovae@gmail.com [Saratov State University (Russian Federation)

2017-03-15

The development and interaction of Bursian and diocotron instabilities in an annular relativistic electron beam propagating in a cylindrical drift chamber are investigated analytically and numerically as functions of the beam wall thickness and the magnitude of the external uniform magnetic field. It is found that the interaction of instabilities results in the formation of a virtual cathode with a complicated rotating helical structure and several reflection regions (electron bunches) in the azimuthal direction. It is shown that the number of electron bunches in the azimuthal direction increases with decreasing beam wall thickness and depends in a complicated manner on the magnitude of the external magnetic field.

Beam-Beam Effects

International Nuclear Information System (INIS)

Herr, W; Pieloni, T

2014-01-01

One of the most severe limitations in high-intensity particle colliders is the beam-beam interaction, i.e. the perturbation of the beams as they cross the opposing beams. This introduction to beam-beam effects concentrates on a description of the phenomena that are present in modern colliding beam facilities

Temperature-dependent ion beam mixing

International Nuclear Information System (INIS)

Rehn, L.E.; Alexander, D.E.

1993-08-01

Recent work on enhanced interdiffusion rates during ion-beam mixing at elevated temperatures is reviewed. As discussed previously, expected increase in ion-beam mixing rates due to 'radiation-enhanced diffusion' (RED), i.e. the free migration of isolated vacancy and interstitial defects, is well documented in single-crystal specimens in the range of 0.4 to 0.6 of absolute melting temperature. In contrast, the increase often observed at somewhat lower temperatures during ion-beam mixing of polycrystalline specimens is not well understood. However, sufficient evidence is available to show that this increase reflects intracascade enhancement of a thermally-activated process that also occurs without irradiation. Recent evidence is presented which suggests that this process is Diffusion-induced Grain-Boundary Migration (DIGM). An important complementary conclusion is that because ion-beam mixing in single-crystal specimens exhibits no significant temperature dependence below that of RED, models that invoke only irradiation-specific phenomena, e.g., cascade-overlap, thermal-spikes, or liquid-diffusion, and hence which predict no difference in mixing behavior between single- or poly-crystalline specimens, cannot account for the existing results

Controllable reflection of X-rays on crystals of saccharose

CERN Document Server

Navasardyan, M A; Hayrapetyan, K T; Gabrielyan, R T

2003-01-01

Multiple (ten times and more) increase in intensities of separate reflections and of lauegram reflections from organic single crystals of saccharose (C sub 1 2H sub 2 2O sub 1 1) was observed under influence of certain temperature gradient. On the base of the present experiment and the data of our previous woks we show that the controllable reflection process has a common nature and the intensity of the diffracted beam under external influences does not depend on the total number of electrons per unit volume of the unit cell of the single crystal.

Low energy ion-molecule reactions

Energy Technology Data Exchange (ETDEWEB)

Farrar, J.M. [Univ. of Rochester, NY (United States)

1993-12-01

This project is concerned with elucidating the dynamics of elementary ion-molecule reactions at collision energies near and below 1 eV. From measurements of the angular and energy distributions of the reaction products, one can infer intimathe details about the nature of collisions leading to chemical reaction, the geometries and lifetimes of intermediate complexes that govern the reaction dynamics, and the collision energy dependence of these dynamical features. The author employs crossed-beam low energy mass spectrometry technology developed over the last several years, with the focus of current research on proton transfer and hydrogen atom transfer reactions of te O{sup {minus}} ion with species such as HF, H{sub 2}O, and NH{sub 3}.

Growth of a delta-doped silicon layer by molecular beam epitaxy on a charge-coupled device for reflection-limited ultraviolet quantum efficiency

Science.gov (United States)

Hoenk, Michael E.; Grunthaner, Paula J.; Grunthaner, Frank J.; Terhune, R. W.; Fattahi, Masoud; Tseng, Hsin-Fu

1992-01-01

Low-temperature silicon molecular beam epitaxy is used to grow a delta-doped silicon layer on a fully processed charge-coupled device (CCD). The measured quantum efficiency of the delta-doped backside-thinned CCD is in agreement with the reflection limit for light incident on the back surface in the spectral range of 260-600 nm. The 2.5 nm silicon layer, grown at 450 C, contained a boron delta-layer with surface density of about 2 x 10 exp 14/sq cm. Passivation of the surface was done by steam oxidation of a nominally undoped 1.5 nm Si cap layer. The UV quantum efficiency was found to be uniform and stable with respect to thermal cycling and illumination conditions.

Matter reflects Antimatter

CERN Document Server

Bianconi, A.; Cristiano, A.; Leali, M.; Lodi Rizzini, E.; Venturelli, L.; Zurlo, N.

2008-01-01

It is common belief that the interaction between antimatter and ordinary solid matter is dominated by annihilation. However, non-destructive processes may play a relevant role too. One century ago E. Rutherford wrote about the "diffuse reflection" of alpha and beta particles by thin layers of different metals: "The observations ... of Geiger and Marsden on the scattering of alpha rays indicate that some of the alpha particles must suffer a deflexion of more than a right angle at a single encounter.... It will be shown that the main deductions from the theory are independent of whether the central charge is supposed to be positive or negative". Although the theory of electromagnetic scattering is in first approximation independent of the relative sign of the colliding particles, in the case where projectile antiprotons are shot against a wall of solid matter the Rutherford diffuse reflection mechanism competes with the annihilation process. So it is not obvious at all that a relevant part of an antiproton beam...

Calculation of Reflectance and Transmittance of Coating With Optically Rough Surfaces

International Nuclear Information System (INIS)

El-Depsy, A.; Shawky, A.M.

2011-01-01

For ideal surfaces, components of the reflected beam are related to the components of the incident beam by Fresnel reflection equation. The surfaces encountered in engineering applications deviate from ideal as a result of roughness, oxidization and contamination; hence the Radiative properties of these real surfaces differ greatly from those predicted by electromagnetic theory. In regard to problems of radiative heat transfer; the roughness of surfaces may be divided into two categories: (1) small surface irregularities such that the incident radiation cannot undergo more than a single reflection, (2) deep cavities in which the incident radiation undergoes multi-reflection. The normally incident radiation from rough surface having small irregularities is reflected partly specularly and partly diffusely [1]. Kubelka-Munk theory (K-M) [2] describes optical characteristics (e.g. reflectance, transmittance and absorbance) by a variety of light scattering media including paints, textiles and papers, and It is widely used in various industrial applications. Moder developments in radiative transfer theory (RTT) enable the derivation of (K-M) parameters from first principles [3]. Kubelka and Munk proposed a theory based on a model of two light fluxes travelling in the forward and backward directions. Subsequently a number of authors refined the theory and compared it with experimental data [4]. Several authors attempted to relate the Kubelka- Munk coefficients to the transport coefficients [5,6

Measurement of the attosecond emission from aligned molecules

International Nuclear Information System (INIS)

Boutu, W.; Merdji, H.; Fitour, R.; Monchicourt, P.; Breger, P.; Carre, B.; Salieres, P.

2006-01-01

Complete test of publication follows. Recently, a number of papers have demonstrated the interest of high-order harmonic generation (HHG) from molecules aligned with respect to the laser polarization. Itatani et al. (Nature 432, 867 (2004)) have shown that a precise characterization of the harmonic emission allows performing a tomographic reconstruction of the molecular orbitals that radiate. Kanai et al. (Nature 435, 470 (2005)) have evidenced quantum interferences in the recombination process of HHG that are directly related to the molecular structure. In all of these papers, only the HHG intensity was measured. The relative harmonic phase, though more difficult to measure, contains important information on the interference process, and is needed for an ab initio tomographic reconstruction. Finally, while the attosecond emission from atoms has been thoroughly studied, in particular by our group (Mairesse et al., Science (302, 1540 (2003)), it has not been investigated in molecules. In a first experiment (Wabnitz et al., EPJD (2006)), we measured the amplitude and relative phase of harmonics radiated by un-aligned nitrogen molecules. Small but reproducible deviations from the phase of harmonics generated in argon (same ionization potential as nitrogen) were measured for low orders. In a recent experiment, we have measured, up to high order, the harmonic amplitude and relative phase for aligned molecules (N 2 and CO 2 ). In order to align the molecules, we used the so-called nonadiabatic technique: a rotational wavepacket is created by a strong enough and short aligning pulse, so that a field-free alignment is obtained at the revival (a few ps after the aligning pulse). The measurement of phase locking between neighboring harmonics was performed through the photoionization of a target gas by the harmonic beam in presence of a sufficiently intense 'dressing' laser beam (RABITT technique). The harmonic phase measured when the CO 2 molecules are aligned parallel to

Use of molecular ion beams from a tandem accelerator

International Nuclear Information System (INIS)

Faibis, A.; Goldring, G.; Hass, M.; Kaim, R.; Plesser, I.; Vager, Z.

1981-01-01

A large variety of positive molecular ion beams can be produced by gaseous charge exchange in the terminal of a tandem accelerator. After acceleration the molecules are usually dissociated by passage through a thin foil. Measurements of the break-up products provide a way to study both the structure of incident ions and the effects of electronic potentials on the internuclear interaction inside the foil. Beam intensities of a few picoamperes are quite adequate for these measurements, and the relatively high energy obtained by use of a tandem accelerator has the advantage of minimizing multiple scattering effects in the foil. The main difficulty in using the molecular beams lies in the large magnetic rigidity of singly-charged heavy molecular ions

Fabrication of the multilayer beam splitters with large area for soft X-ray laser interferometer

International Nuclear Information System (INIS)

Wang Zhanshan; Zhang Zhong; Wang Fengli; Wu Wenjuan; Wang Hongchang; Qin Shuji; Chen Lingyan

2004-01-01

The soft X-ray laser Mach-Zehnder interferometer is an important tool to measure the electron densities of a laser-produced plasma near the critical surface. The design of a multilayer beam splitter at 13.9 nm for soft X-ray laser Mach-Zehnder interferometer is completed based on the standard of maximizing product of reflectivity and transmission of the beam splitter. The beam splitters which is Mo/Si multilayers on 10 mm x 10 mm area Si 3 N 4 membrane are fabricated using the magnetron sputtering. The figure error of the beam splitter has reached the deep nanometer magnitude by using optical profiler and the product of reflectivity and transmission measured by synchrotron radiation is up to to 4%. (authors)

Fabrication of Low Noise Borosilicate Glass Nanopores for Single Molecule Sensing.

Directory of Open Access Journals (Sweden)

Jayesh A Bafna

Full Text Available We show low-cost fabrication and characterization of borosilicate glass nanopores for single molecule sensing. Nanopores with diameters of ~100 nm were fabricated in borosilicate glass capillaries using laser assisted glass puller. We further achieve controlled reduction and nanometer-size control in pore diameter by sculpting them under constant electron beam exposure. We successfully fabricate pore diameters down to 6 nm. We next show electrical characterization and low-noise behavior of these borosilicate nanopores and compare their taper geometries. We show, for the first time, a comprehensive characterization of glass nanopore conductance across six-orders of magnitude (1M-1μM of salt conditions, highlighting the role of buffer conditions. Finally, we demonstrate single molecule sensing capabilities of these devices with real-time translocation experiments of individual λ-DNA molecules. We observe distinct current blockage signatures of linear as well as folded DNA molecules as they undergo voltage-driven translocation through the glass nanopores. We find increased signal to noise for single molecule detection for higher trans-nanopore driving voltages. We propose these nanopores will expand the realm of applications for nanopore platform.

Serial single molecule electron diffraction imaging: diffraction background of superfluid helium droplets

Science.gov (United States)

Zhang, Jie; He, Yunteng; Lei, Lei; Alghamdi, Maha; Oswalt, Andrew; Kong, Wei

2017-08-01

In an effort to solve the crystallization problem in crystallography, we have been engaged in developing a method termed "serial single molecule electron diffraction imaging" (SS-EDI). The unique features of SS-EDI are superfluid helium droplet cooling and field-induced orientation: together the two features constitute a molecular goniometer. Unfortunately, the helium atoms surrounding the sample molecule also contribute to a diffraction background. In this report, we analyze the properties of a superfluid helium droplet beam and its doping statistics, and demonstrate the feasibility of overcoming the background issue by using the velocity slip phenomenon of a pulsed droplet beam. Electron diffraction profiles and pair correlation functions of ferrocene-monomer-doped droplets and iodine-nanocluster-doped droplets are presented. The timing of the pulsed electron gun and the effective doping efficiency under different dopant pressures can both be controlled for size selection. This work clears any doubt of the effectiveness of superfluid helium droplets in SS-EDI, thereby advancing the effort in demonstrating the "proof-of-concept" one step further.

Generation of Ag nanospikes via laser ablation in liquid environment and their activity in SERS of organic molecules

Energy Technology Data Exchange (ETDEWEB)

Lau Truong, S.; Levi, G.; Bozon-Verduraz, F. [Universite Paris 7-Denis Diderot, ITODYS, UMR-CNRS 7086, Paris Cedex 05 (France); Petrovskaya, A.V.; Simakin, A.V.; Shafeev, G.A. [Russian Academy of Sciences, Wave Research Center of A.M. Prokhorov General Physics Institute, Moscow (Russian Federation)

2007-11-15

The formation of dense arrays of nanospikes occurs under laser ablation of bulk silver immersed in liquids such as water or ethanol. The average height of spikes is 50 nm and their density on the target amounts to 10{sup 10} cm{sup -2}. This effect is observed with sufficiently short laser pulses. In particular, either a 350 ps or a 90 ps Nd:YAG lasers are used operating in their fundamental harmonics. These nanospikes are characterized by UV-visible reflection spectrometry and atomic force microscopy. The oscillations of electrons within Ag nanospikes results in a permanent coloration of the surface and a modification of the optical reflection spectra of the metal. Nanospikes show a peak of plasmon resonance around 380 nm, which shifts to the visible range upon oxidation in air. The initial spectrum may be restored by reduction of the oxidized Ag surface through processing in an ammonia aqueous solution. Scanning the laser beam along the metal surface allows its nanostructuring over extended areas ({proportional_to}1 cm{sup 2}). The nanostructured Ag surface shows enhanced Raman scattering of acridine molecules at a concentration of 10{sup -5} M/l, whereas initial Ag target do not show any signal within the accuracy of measurements. (orig.)

Expanded beam deflection method for simultaneous measurement of displacement and vibrations of multiple microcantilevers

International Nuclear Information System (INIS)

Nieradka, K.; MaloziePc, G.; Kopiec, D.; Gotszalk, T.; Grabiec, P.; Janus, P.; Sierakowski, A.

2011-01-01

Here we present an extension of optical beam deflection (OBD) method for measuring displacement and vibrations of an array of microcantilevers. Instead of focusing on the cantilever, the optical beam is either focused above or below the cantilever array, or focused only in the axis parallel to the cantilevers length, allowing a wide optical line to span multiple cantilevers in the array. Each cantilever reflects a part of the incident beam, which is then directed onto a photodiode array detector in a manner allowing distinguishing between individual beams. Each part of reflected beam behaves like a single beam of roughly the same divergence angle in the bending sensing axis as the incident beam. Since sensitivity of the OBD method depends on the divergence angle of deflected beam, high sensitivity is preserved in proposed expanded beam deflection (EBD) method. At the detector, each spot's position is measured at the same time, without time multiplexing of light sources. This provides real simultaneous readout of entire array, unavailable in most of competitive methods, and thus increases time resolution of the measurement. Expanded beam can also span another line of cantilevers allowing monitoring of specially designed two-dimensional arrays. In this paper, we present first results of application of EBD method to cantilever sensors. We show how thermal noise resolution can be easily achieved and combined with thermal noise based resonance frequency measurement.

Importance of beam-beam tune spread to collective beam-beam instability in hadron colliders

International Nuclear Information System (INIS)

Jin Lihui; Shi Jicong

2004-01-01

In hadron colliders, electron-beam compensation of beam-beam tune spread has been explored for a reduction of beam-beam effects. In this paper, effects of the tune-spread compensation on beam-beam instabilities were studied with a self-consistent beam-beam simulation in model lattices of Tevatron and Large Hodron Collider. It was found that the reduction of the tune spread with the electron-beam compensation could induce a coherent beam-beam instability. The merit of the compensation with different degrees of tune-spread reduction was evaluated based on beam-size growth. When two beams have a same betatron tune, the compensation could do more harm than good to the beams when only beam-beam effects are considered. If a tune split between two beams is large enough, the compensation with a small reduction of the tune spread could benefit beams as Landau damping suppresses the coherent beam-beam instability. The result indicates that nonlinear (nonintegrable) beam-beam effects could dominate beam dynamics and a reduction of beam-beam tune spread by introducing additional beam-beam interactions and reducing Landau damping may not improve the stability of beams

Polymeric membrane studied using slow positron beam

International Nuclear Information System (INIS)

Hung, W.-S.; Lo, C.-H.; Cheng, M.-L.; Chen Hongmin; Liu Guang; Chakka, Lakshmi; Nanda, D.; Tung, K.-L.; Huang, S.-H.; Lee, Kueir-Rarn; Lai, J.-Y.; Sun Yiming; Yu Changcheng; Zhang Renwu; Jean, Y.C.

2008-01-01

A radioisotope slow positron beam has been built at the Chung Yuan Christian University in Taiwan for the research and development in membrane science and technology. Doppler broadening energy spectra and positron annihilation lifetime have been measured as a function of positron energy up to 30 keV in a polyamide membrane prepared by the interfacial polymerization between triethylenetetraamine (TETA) and trimesoyl chloride (TMC) on modified porous polyacrylonitrile (PAN) asymmetric membrane. The multilayer structures and free-volume depth profile for this asymmetric membrane system are obtained. Positron annihilation spectroscopy coupled with a slow beam could provide new information about size selectivity of transporting molecules and guidance for molecular designs in polymeric membranes

Injection of an electron beam into a plasma and spacecraft charging

International Nuclear Information System (INIS)

Okuda, H.; Kan, J.R.

1987-01-01

Injection of a nonrelativistic electron beam into a fully ionized plasma from a spacecraft including the effect of charging has been studied using a one-dimensional particle simulation model. It is found that the spacecraft charging remains negligible and the beam can propagate into a plasma, if the beam density is much smaller than the ambient density. When the injection current is increased by increasing the beam density, significant spacecraft charging takes place and the reflection of beam electrons back to the spacecraft reduces the beam current significantly. On the other hand, if the injection current is increased by increasing the beam energy, spacecraft charging remains negligible and a beam current much larger than the thermal return current can be injected. It is shown that the electric field caused by the beam--plasma instability accelerates the ambient electrons toward the spacecraft thereby enhancing the return current

Low-temperature relative reflectivity measurements of reflective and scintillating foils used in rare event searches

Science.gov (United States)

Langenkämper, A.; Ulrich, A.; Defay, X.; Feilitzsch, F. v.; Lanfranchi, J.-C.; Mondragón, E.; Münster, A.; Oppenheimer, C.; Potzel, W.; Roth, S.; Schönert, S.; Steiger, H.; Trinh Thi, H. H.; Wawoczny, S.; Willers, M.; Zöller, A.

2018-03-01

In this work we investigate the reflectivity of highly reflective multilayer polymer foils used in the CRESST experiment. The CRESST experiment searches directly for dark matter via operating scintillating CaWO4 crystals as targets for elastic dark matter-nucleon scattering. In order to suppress background events, the experiment employs the so-called phonon-light technique which is based on the simultaneous measurement of the heat signal in the main CaWO4 target crystal and of the emitted scintillation light with a separate cryogenic light detector. Both detectors are surrounded by a highly reflective and scintillating multilayer polymer foil to increase the light collection efficiency and to veto surface backgrounds. While this study is motivated by the CRESST experiment, the results are also relevant for other rare event searches using scintillating cryogenic bolometers in the field of the search of dark matter and neutrinoless double beta decay (0 νββ). In this work a dedicated experiment has been set up to determine the relative reflectivity at 300 K and 20 K of three multilayer foils ("VM2000", "VM2002", "Vikuiti") produced by the company 3M. The intensity of a light beam reflected off the foil is measured with a CCD camera. The ratio of the intensities at 300 K and 20 K corresponds to the relative reflectivity change. The measurements performed in this work show no variation of the reflectivity with temperature at a level of ∼1%.

Experimental study on electrostatic guiding of supersonic D2O molecular beam with two charged wires

International Nuclear Information System (INIS)

Yin Yaling; Xia Yong; Chen Haibo; Yin Jianping

2007-01-01

We demonstrate the guiding of a supersonic heavy-water (D 2 O) molecular beam using a hollow electrostatic field generated by the combination of two parallel charged-wires and two grounded metal-plates, and report some new and preliminary experimental results. In the experiment, we detect the guiding signals by using the method of time-of-flight mass spectrum and study the dependence of the relative transmission of the beam guide on the guiding voltage. Our study shows that the relative transmission of the beam guide is increased linearly with increasing guiding voltage V guid , and the number of the guided D 2 O molecules is at least increased by 89.4% when the guiding voltage is +20.0 kV. Finally, some potential applications of our guiding scheme in the molecule optics are briefly discussed. (authors)

Injection and propagation of a nonrelativistic electron beam and spacecraft charging

International Nuclear Information System (INIS)

Okuda, H.; Berchem, J.

1987-05-01

Two-dimensional numerical simulations have been carried out in order to study the injection and propagation of a nonrelativistic electron beam from a spacecraft into a fully ionized plasma in a magnetic field. Contrary to the earlier results in one-dimension, a high density electron beam whose density is comparable to the ambient density can propagate into a plasma. A strong radial electric field resulting from the net charges in the beam causes the beam electrons to spread radially reducing the beam density. When the injection current exceeds the return current, significant charging of the spacecraft is observed along with the reflection of the injected electrons back to the spacecraft. Recent data on the electron beam injection from the Spacelab 1 (SEPAC) are discussed

Electron Beam Mediated Simple Synthetic Route to Preparing Layered Zinc Hydroxide

International Nuclear Information System (INIS)

Bae, Hyo Sun; Jung, Hyun

2012-01-01

We have developed a novel and eco-friendly synthetic route for the preparation of a two-dimensional layered zinc hydroxide with intercalated nitrate anions. The layered zinc hydroxide nitrate, called 'zinc basic salt', was, in general, successfully synthesized, using an electron beam irradiation technique. The 2-propanol solutions containing hydrated zinc nitrate were directly irradiated with an electron-beam at room temperature, under atmospheric conditions, without stabilizers or base molecules. Under electron beam irradiation, the reactive OH· radicals were generated by radiolysis of water molecules in precursor metal salts. After further radiolytic processes, the hydroxyl anions might be formed by the reaction of solvated electrons and the OH· radical. Finally, the Zn 5 (OH) 8 (NO 3 ) 2 ·2H 2 O was precipitated by the reaction of zinc cation and hydroxyl anions. Structure and morphology of obtained compounds were characterized by powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and high resolution transmission electron microscopy (HR-TEM). The chemical components of the products were determined by Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (EA). The thermal behavior of products was studied by thermogravimetric (TG) and differential thermal analysis (DTA)

Laser beam shaping design based on micromirror array

Science.gov (United States)

Fang, Han; Su, Bida; Liu, Jiaguo; Fan, Xiaoli; Jing, Wang

2017-10-01

In the practical application of the laser, it is necessary to use the laser beam shaping technology to shape the output beam of laser device to the uniform light intensity distribution. The shaping divergent optical system of compound eye integrator way is composed of beam expanding mirror group and lens array. Its working principle is to expand the output laser to a certain size of caliber, and then divide the beam with lens array into multiple sub beam, where the lens unit of lens array can control the divergence angle of sub beam through the design of focal length, with mutual superposition of the sub beam in far field, to make up for the nonuniformity of beam, so that the radiant exitance on the radiated surface may become uniform. In this paper, we use a reflective microlens array to realize the laser beam shaping. By through of the practical optical path model established, the ray tracing is carried out and the simulation results for single-mode Gaussian beam with noise circumstance is provided. The analysis results show that the laser beam shaping under different inputs can be effectively realized by use of microlens array. All the energy is within the signal window, with a high energy efficiency of more than 90%; The measured surface has a better uniformity, and the uniformity is better than 99.5% at 150m.

The measurement of neutral beam thermal profiles on 'V'-shaped calorimeters

International Nuclear Information System (INIS)

Kamperschroer, J.H.; Lagin, L.J.; Silber, K.

1995-01-01

It is customary in high power neutral beam systems to use a V-shaped calorimeter to stop and measure the beam. With proper instrumentation, it is possible to determine both the neutral beam power and divergence. By utilizing a near-grazing angle of incidence, the area over which the beam is in contact with the surface is increased, thereby decreasing the power density over the case of normal incidence. Thermocouples on the back of the calorimeter, in conjunction with real time fitting algorithms, are used to deduce the divergence from the thermal profile. This measurement implicitly assumes that the measured profile corresponds to that of the incident beam. It is shown that such is not the case. Energetic particle reflection at near-grazing angle causes the thermal profile on the calorimeter to be more peaked than the incident distribution. The implications of this on the non-linear multiple regression technique of determining the divergence are discussed. With the aid of a reflection model, developed and applied to the beam from a typical TFTR ion source, it is shown that a peaked power density can be modelled. Neural networks are being studied as a means of supplanting the older regression technique of measuring divergence. Y-direction divergences have been successfully derived using a one-dimensional neural network

A high-efficiency positive (negative) surface ionization source for radioactive ion beam (abstract)a

International Nuclear Information System (INIS)

Alton, G.D.; Mills, G.D.

1996-01-01

A versatile, new concept, spherical-geometry, positive (negative) surface-ionization source has been designed and fabricated which will have the capability of generating both positive- and negative-ion beams without mechanical changes to the source. The source utilizes a highly permeable, high-work-function Ir ionizer (φ≡5.29 eV) for ionizing highly electropositive atoms/molecules; while for negative-surface ionization, the work function is lowered to φ≡1.43 eV by continually feeding cesium vapor through the ionizer matrix. The use of this technique for negative ion beam generation has the potential of overcoming the chronic poisoning effects experienced with LaB 6 while enhancing considerably the efficiency for negative surface ionization of atoms and molecules with intermediate electron affinities. The flexibility of operation in either mode makes it especially attractive for radioactive ion beam applications and, therefore, the source will be used as a complementary replacement for the high-temperature electron impact ionization sources presently in use at the Holifield radioactive beam facility. The design features and operational principles of the source will be described in this report. copyright 1996 American Institute of Physics

Study on the excited diatomic molecules of rare gas

International Nuclear Information System (INIS)

Kasama, Kunihiko; Arai, Shigeyoshi

1981-01-01

The study on the excited diatomic molecules of rare gas is presented. The absorption spectra, the mechanism of formation and attenuation and the reactions with other molecules are described. The excitation of rare gas was made by using a pulsed electron beam generator. The absorption of excited diatomic molecules was measured as the functions of time. Two absorption peaks were observed. The electron states of rare gases were estimated. The observed and calculated transition values were given for each peak. The absorption spectra of Ne change with time. The spectra of Ar do not change with time. Four and eleven absorption maxima were seen in the spectra of Kr and Xe, respectively. In the case of Ar, the thermal equilibrium existed. The constants of the production and attenuation rates were obtained as the functions of Ar gas pressure. In the case of Ne, there wad definitely the time dependence of absorption spectra. The attenuation constant was obtained for each transition between various vibration levels. It is necessary to consider the relaxation from high vibrational levels. The energy transfer between vibrational levels hardly occurred in Ne because the intervals are large. When there are other molecules, the attnuation was accelerated. (Kato, T.)

On the radiation accompanying volume reflection

International Nuclear Information System (INIS)

Bandiera, L.; Bagli, E.; Berra, A.; Bolognini, D.; Dalpiaz, P.; Della Mea, G.; De Salvador, D.; Guidi, V.; Hasan, S.; Lietti, D.; Mazzolari, A.

2013-01-01

The electromagnetic radiation emitted by 120 GeV/c volume-reflected electrons in a bent silicon crystal has been investigated at CERN SPS-H4 beamline. The trajectories of electrons crossing a silicon strip-like crystal have been reconstructed through a telescope system based on high precision micro-strip detectors. The experimental setup was also equipped with a spectrometer and an electromagnetic calorimeter to measure the energy loss of the particles under volume reflection condition. Such a system enabled to record the full photon spectrum up to the nominal energy of the beam. Experimental results were compared to recently developed theoretical approaches based on the quasi-classical operators method of Baier and Katkov

Low energy electron attachment to the uracil molecule

International Nuclear Information System (INIS)

Hanel, G.; Gstir, B.; Denifl, S.; Scheier, P.; Maerk, T.D.; Farizon, B.; Farizon, M.

2002-01-01

Using a recently constructed high resolution crossed beam apparatus involving a hemispherical electron monochromator, electron attachment to the uracil molecule C 4 H 4 N 2 O 2 was studied. The electron energy range investigated was in the region between 0 and 12 eV. What will happen when slow electrons are colliding with the cellular RNA compound uracil was the objective of this investigation. The following anion fragments were detected: (C 4 H 3 N 2 O 2 ) - , OCN - , (H 2 C 3 NO) - , CN - , O - . The most important result was that within the detection efficiency any traces of the parent anion were observed. The most intense fragment anion appeared on a mass to charge ratio 111 amu., it corresponds to a uracil molecule missing one hydrogen. Another observation was whereas the parent minus H anion is observed at zero electron energy, all other fragments appear in other range. (nevyjel)

Structured surface reflector design for oblique incidence beam splitter at 610 GHz

OpenAIRE

Defrance , Fabien; Casaletti , Massimiliano; Sarrazin , Julien; Wiedner , Martina; Gibson , Hugh; Gay , Gregory; Lefevre , Roland; Delorme , Yan

2016-01-01

International audience; An iterative alternate projection-based algorithm is developed to design structured surface reflectors to operate as beam splitters at GHz and THz frequencies. To validate the method, a surface profile is determined to achieve a reflector at 610 GHz that generates four equal-intensity beams towards desired directions of ±12.6° with respect to the specular reflection axis. A prototype is fabricated and the beam splitter behavior is experimentally demonstrated. Measureme...

Combined reflection and transmission microscope for telemedicine applications in field settings.

Science.gov (United States)

Biener, Gabriel; Greenbaum, Alon; Isikman, Serhan O; Lee, Kelvin; Tseng, Derek; Ozcan, Aydogan

2011-08-21

We demonstrate a field-portable upright and inverted microscope that can image specimens in both reflection and transmission modes. This compact and cost-effective dual-mode microscope weighs only ∼135 grams (image of the specimen onto an opto-electronic sensor-array that is positioned above the beam-splitter cube. In addition to this, the illumination beam is also partially transmitted through the same specimen, which then casts lensfree in-line holograms of the same objects onto a second opto-electronic sensor-array that is positioned underneath the beam-splitter cube. By rapid digital reconstruction of the acquired lensfree holograms, transmission images (both phase and amplitude) of the same specimen are also created. We tested the performance of this field-portable microscope by imaging various micro-particles, blood smears as well as a histopathology slide corresponding to skin tissue. Being compact, light-weight and cost-effective, this combined reflection and transmission microscope might especially be useful for telemedicine applications in resource limited settings. This journal is © The Royal Society of Chemistry 2011

Towards high purity nanostructures from electron beam induced deposition of platinum

NARCIS (Netherlands)

Botman, A.P.J.M.

2009-01-01

Electron beam induced deposition (EBID) is a novel nanofabrication technique allowing the rapid prototyping of three-dimensional nanodevices and the metallic wiring of nanostructures, and is a promising technique for many applications in nanoresearch. EBID is a process wherein a precursor molecule

Dynamics of infrared multiphonon dissociation of SF6 by molecular beam method

International Nuclear Information System (INIS)

Grant, E.R.; Coggiola, M.J.; Lee, Y.T.; Schulz, P.A.; Shen, Y.R.

1977-01-01

A crossed molecular beam apparatus has been adapted to study the dynamics of excitation and dissociation of polyatomic molecules in intense IR laser fields. Initial experiments have involved the study of the dissociation of SF 6 by CO 2 laser radiation at 10.6 μm. A molecular beam of SF 6 was formed by supersonic expansion using three stages of differential pumping. A grating tuned pulsed CO 2 TEA laser was used as the excitation source. The laser beam was focused by a 25 cm focal length ZnSe lens, and crossed the molecular beam near its focal point. The fragments produced by multiphonon dissociation of SF 6 within the small interaction region were detected as a function of recoil angle and velocity. (Auth.)

Influence of the linear magneto-electric effect on the lateral shift of light reflected from a magneto-electric film

International Nuclear Information System (INIS)

Dadoenkova, Yu S; Petrov, R V; Bichurin, M I; Bentivegna, F F L; Dadoenkova, N N; Lyubchanskii, I L

2016-01-01

We present a theoretical investigation of the lateral shift of an infrared light beam reflected from a magnetic film deposited on a non-magnetic dielectric substrate, taking into account the linear magneto-electric interaction in the magnetic film. We use the stationary phase method to evaluate the lateral shift. It is shown that the magneto-electric coupling leads to a six-fold enhancement of the lateral shift amplitude of a p-(s-) polarized incident beam reflected into a s-(p-) polarized beam. A reversal of the magnetization in the film leads to a nonreciprocal sign change of the lateral shift. (paper)

Trajectory method in the theory of Laue diffraction of X rays in crystals: II. Effect of total reflection at bending deformation

International Nuclear Information System (INIS)

Kohn, V. G.

2008-01-01

The effect of total reflection (switching) of a spherical X-ray wave in the case of Laue diffraction in a crystal with bending deformation is analyzed by the trajectory method. Qualitative analytical description and computation of the spatial structure of the reflected beam for large and small distances between the spherical-wave source and the crystal are performed. The mechanism of much more efficient reflection of an X-ray beam by a deformed crystal in comparison with a perfect crystal is clearly demonstrated. It is also shown that the trajectory method is very convenient for description of the total reflection phenomenon.

Trajectory method in the theory of Laue diffraction of X rays in crystals: II. Effect of total reflection at bending deformation

International Nuclear Information System (INIS)

Kohn, V. G.

2008-01-01

The effect of total reflection (switching) of a spherical X-ray wave in the case of Laue diffraction in a crystal with bending deformation is analyzed by the trajectory method. Qualitative analytical description and computation of the spatial structure of the reflected beam for large and small distances between the spherical-wave source and the crystal are performed. The mechanism of much more efficient reflection of an X-ray beam by a deformed crystal in comparison with a perfect crystal is clearly demonstrated. It is also shown that the trajectory method is very convenient for description of the total reflection phenomenon

Molecule Matters van der Waals Molecules

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 14; Issue 12. Molecule Matters van der Waals Molecules - Noble Gas Clusters are London Molecules! E Arunan. Feature Article Volume 14 Issue 12 December 2009 pp 1210-1222 ...

Electron stereodynamics in coulomb explosion of molecules by slow highly charged ions

International Nuclear Information System (INIS)

Ichimura, Atsushi; Ohyama-Yamaguchi, Tomoko

2008-01-01

The three-center Coulombic over-the-barrier model is developed for Coulomb explosion of a homonuclear diatomic molecule in collisions with a slow (∼10 eV/amu) highly charged ion. A conventional two-step picture of multiple electron transfer followed by Coulomb explosion is far from appropriate because the molecule sets out to dissociate before the incident ion approaches the closest distance. We treat the formation of a quasi-molecule and its decay into the three moving atomic ions. Charge-asymmetric population between fragment ions observed in a triple-coincidence measurement is suggested to reflect the bond elongation during a collision. Collisions of Kr 8+ + N 2 are analyzed. (author)

Goos–Hänchen and Imbert–Fedorov beam shifts: an overview

International Nuclear Information System (INIS)

Bliokh, K Y; Aiello, A

2013-01-01

We consider reflection and transmission of polarized paraxial light beams at a plane dielectric interface. The field transformations taking into account a finite beam width are described based on the plane-wave representation and geometric rotations. Using geometrical-optics coordinate frames accompanying the beams, we construct an effective Jones matrix characterizing spatial-dispersion properties of the interface. This results in a unified self-consistent description of the Goos–Hänchen and Imbert–Fedorov shifts (the latter being also known as the spin Hall effect of light). Our description reveals the intimate relation of the transverse Imbert–Fedorov shift to the geometric phases between constituent waves in the beam spectrum and to the angular momentum conservation for the whole beam. Both spatial and angular shifts are considered as well as their analogues for higher-order vortex beams carrying intrinsic orbital angular momentum. We also give a brief overview of various extensions and generalizations of the basic beam-shift phenomena and related effects. (review article)

Numerical study on the interaction between a modulated electron beam and a plasma

International Nuclear Information System (INIS)

Fukumasa, Osamu; Itatani, Ryohei.

1981-09-01

Interaction of a modulated electron beam with a plasma is calculated for unbounded and bounded electron beam-plasma systems, using the method of partial simulation. In the case of the unbounded system, deformation of the beam distribution function is occurred in relation to suppression of one wave by the other wave. While, in the case of the bounded system, occurrence of deformation depends on whether feedback effects of reflected beams are present or not. The findings are qualitatively in agreement with our experimental results [19]. (author)

Beam profile measurements on the advanced test accelerator using optical techniques

International Nuclear Information System (INIS)

Chong, Y.P.; Kalibjian, R.; Cornish, J.P.; Kallman, J.S.; Donnelly, D.

1986-01-01

Beam current density profiles of ATA have been measured both spatially and temporally using a number of diagnostics. An extremely important technique involves measuring optical emissions from either a target foil inserted into the beam path or gas atoms and molecules excited by beam electrons. This paper describes the detection of the optical emission. A 2-D gated television camera with a single or dual micro-channel-plate (MCP) detector for high gain provides excellent spatial and temporal resolution. Measurements are routinely made with resolutions of 1 mm and 5 ns respectively. The optical line of sight allows splitting part of the signal to a streak camera or photometer for even higher time resolution

Reflection and transmission of normally incident full-vector X waves on planar interfaces

KAUST Repository

Salem, Mohamed

2011-12-23

The reflection and transmission of full-vector X waves normally incident on planar half-spaces and slabs are studied. For this purpose, X waves are expanded in terms of weighted vector Bessel beams; this new decomposition and reconstruction method offers a more lucid and intuitive interpretation of the physical phenomena observed upon the reflection or transmission of X waves when compared to the conventional plane-wave decomposition technique. Using the Bessel beam expansion approach, we have characterized changes in the field shape and the intensity distribution of the transmitted and reflected full-vector X waves. We have also identified a novel longitudinal shift, which is observed when a full-vector X wave is transmitted through a dielectric slab under frustrated total reflection condition. The results of our studies presented here are valuable in understanding the behavior of full-vector X waves when they are utilized in practical applications in electromagnetics, optics, and photonics, such as trap and tweezer setups, optical lithography, and immaterial probing. © 2011 Optical Society of America.

Trapping and interactions of an ultracold gas of Cs2 molecules

International Nuclear Information System (INIS)

Mark, M.; Kraemer, T.; Herbig, J.; Waldburger, P.; Naegerl, H.C.; Chin, C.; Grimm, R.

2005-01-01

Full text: We investigate dynamics and interactions of Cs 2 dimers in a CO2-laser dipole trap. Starting with a Bose-Einstein condensate (BEC) of 2.2 x 10 5 Cs atoms, we create ultracold molecules in a single, weakly bound quantum state by sweeping the magnetic field across a narrow Feshbach resonance. When the molecules are created in free space, the conversion efficiency exceeds 30 %, yielding up to 50000 molecules. In our trapping experiments, about 6000 ultracold Cs 2 dimers are prepared in the optical trap at a temperature of 200 nK. We transfer the trapped molecules from the initial molecular state to other molecular states by following avoided crossings. We find two magnetically tunable resonances in collisions between the molecules for one of the molecular states. We interpret these Feshbach-liKEX resonances as being induced by Cs 4 bound states near the molecular scattering continuum. Further, we have discovered a new molecular state with very large orbital angular momentum of l = 8. This state is very weakly coupled to one of the initial molecular states. We use the associated avoided crossing as a molecular beam splitter to realize a molecular Ramsey-type interferometer. Refs. 2 (author)

Single DNA molecules as probes for interrogating silica surfaces after various chemical treatments

International Nuclear Information System (INIS)

Liu Xia; Wu Zhan; Nie Huagui; Liu Ziling; He Yan; Yeung, E.S.

2007-01-01

We examined the adsorption of single YOYO-1-labeled λ-DNA molecules at glass surfaces after treatment with various chemical cleaning methods by using total internal reflection fluorescence microscopy (TIRFM). The characteristics of these surfaces were further assessed using contact angle (CA) measurements and atomic force microscopy (AFM). By recording the real-time dynamic motion of DNA molecules at the liquid/solid interface, subtle differences in adsorption affinities were revealed. The results indicate that the driving force for adsorption of DNA molecules on glass surfaces is mainly hydrophobic interaction. We also found that surface topography plays a role in the adsorption dynamics

Coherent beam-beam effects

International Nuclear Information System (INIS)

Chao, A.W.

1992-01-01

There are two physical pictures that describe the beam-beam interaction in a storage ring collider: The weak-strong and the strong-strong pictures. Both pictures play a role in determining the beam-beam behavior. This review addresses only the strong-strong picture. The corresponding beam dynamical effects are referred to as the coherent beam-beam effects. Some basic knowledge of the weak-strong picture is assumed. To be specific, two beams of opposite charges are considered. (orig.)

High Throughput, Label-free Screening Small Molecule Compound Libraries for Protein-Ligands using Combination of Small Molecule Microarrays and a Special Ellipsometry-based Optical Scanner.

Science.gov (United States)

Landry, James P; Fei, Yiyan; Zhu, X D

2011-12-01

Small-molecule compounds remain the major source of therapeutic and preventative drugs. Developing new drugs against a protein target often requires screening large collections of compounds with diverse structures for ligands or ligand fragments that exhibit sufficiently affinity and desirable inhibition effect on the target before further optimization and development. Since the number of small molecule compounds is large, high-throughput screening (HTS) methods are needed. Small-molecule microarrays (SMM) on a solid support in combination with a suitable binding assay form a viable HTS platform. We demonstrate that by combining an oblique-incidence reflectivity difference optical scanner with SMM we can screen 10,000 small-molecule compounds on a single glass slide for protein ligands without fluorescence labeling. Furthermore using such a label-free assay platform we can simultaneously acquire binding curves of a solution-phase protein to over 10,000 immobilized compounds, thus enabling full characterization of protein-ligand interactions over a wide range of affinity constants.

Ionization of nitrogen cluster beam

International Nuclear Information System (INIS)

Yano, Katsuki; Be, S.H.; Enjoji, Hiroshi; Okamoto, Kosuke

1975-01-01

A nitrogen cluster beam (neutral particle intensity of 28.6 mAsub(eq)) is ionized by electron collisions in a Bayard-Alpert gauge type ionizer. The extraction efficiency of about 65% is obtained at an electron current of 10 mA with an energy of 50 eV. The mean cluster size produced at a pressure of 663 Torr and temperature of 77.3 K is 2x10 5 molecules per cluster. By the Coulomb repulsion force, multiply ionized cluster ions are broken up into smaller fragments and the cluster ion size reduces to one-fourth at an electron current of 15 mA. Mean neutral cluster sizes depend strongly on the initial degree of saturation PHI 0 and are 2x10 5 , 7x10 4 and 3x10 4 molecules per cluster at PHI 0 's of 0.87, 0.66 and 0.39, respectively. (auth.)

Free molecule flow analysis of the interaction of skimming hardware components and background gas with free jets

International Nuclear Information System (INIS)

Raghuraman, P.; Bossel, U.

1974-01-01

Under conditions typical for the extraction of nozzle beams from free jets the rarefied flow pattern in the expansion chamber containing skimming hardware components and background gas is studied using a free molecule solution to the Boltzmann equation

Surface Resistance Measurements of LHC Dipole Beam Screen Samples

CERN Document Server

Caspers, Friedhelm; Ruggiero, F; Tan, J; Tsutsui, H

2000-01-01

An estimate of the resistive losses in the LHC dipole beam screen is given from cold surface resistance measurements using the shielded pair technique. Several beam screen samples have been evaluated, with different copper coating methods, including a sample with ribbed surface envisaged to reduce electron cloud losses thanks to its low reflectivity. Experimental data, derived by a proper analysis of the measured Q-factors and including error estimates are compared with theoretical predictions of the anomalous skin effect.

Fluorescent Biosensors Based on Single-Molecule Counting.

Science.gov (United States)

Ma, Fei; Li, Ying; Tang, Bo; Zhang, Chun-Yang

2016-09-20

fluorescence signals by specific in vitro/in vivo fluorescent labeling, and consequently, the fluorescent molecules indicate the presence of target molecules. The resultant fluorescence signals may be simply counted by either microfluidic device-integrated confocal microscopy or total internal reflection fluorescence-based single-molecule imaging. We have developed a series of single-molecule counting-based biosensors which can be classified as separation-free and separation-assisted assays. As a proof-of-concept, we demonstrate the applications of single-molecule counting-based biosensors for sensitive detection of various target biomolecules such as DNAs, miRNAs, proteins, enzymes, and intact cells, which may function as the disease-related biomarkers. Moreover, we give a summary of future directions to expand the usability of single-molecule counting-based biosensors including (1) the development of more user-friendly and automated instruments, (2) the discovery of new fluorescent labels and labeling strategies, and (3) the introduction of new concepts for the design of novel biosensors. Due to their high sensitivity, good selectivity, rapidity, and simplicity, we believe that the single-molecule counting-based fluorescent biosensors will indubitably find wide applications in biological research, clinical diagnostics, and drug discovery.

Electron collision cross sections and electron swarm parameters for gas molecules

International Nuclear Information System (INIS)

Hayashi, Makoto

1986-01-01

Elastic and inelastic electron collision cross sections for molecules which interest in radiation research have been determined from available electron beam and electron swarm data by utilizing the Boltzmann equation and Monte Carlo simulation method. Electron drift velocity data which interest in radiation Pysics have been discussed and some calculated results of electron drift velocity data for CF 4 and CF 4 -inert gases mixtures will be presented. (author)

An approach towards solving refraction problems in EM1002 multi-beam echo-sounder system

Digital Repository Service at National Institute of Oceanography (India)

Fernandes, W.A.

Multi-beam echo-sounding is the technique in which multiple beams of acoustic in nature are sent down to seabed and upon reflection, they are received back and processed to give depths values. The report is focused to give a brief idea about EM1002...

Radiolysis study of actinide complexing agent by irradiation with helium ion beam

International Nuclear Information System (INIS)

Sugo, Yumi; Taguchi, Mitsumasa; Sasaki, Yuji; Hirota, Koichi; Kimura, Takaumi

2009-01-01

α-Radiolysis of N,N,N',N'-tetraoctyldiglycolamide (TODGA) in n-dodecane was investigated by the irradiation with helium ion beam provided by a tandem accelerator. The radiation chemical yield for the degradation of TODGA by helium ion beam irradiation was less than that by γ-rays irradiation. It is considered that the radical cations of n-dodecane, which contribute to the charge transfer reaction with the TODGA molecules, decrease by recombination in track by high LET radiations such as α-particles.

Anisotropic etching of polycrystalline silicon with a hot Cl2 molecular beam

International Nuclear Information System (INIS)

Suzuki, K.; Hiraoka, S.; Nishimatsu, S.

1988-01-01

A hot Cl 2 molecular (Cl/sup */ 2 ) beam was successfully applied to achieve highly anisotropic, highly selective, and almost damage-free etching of polycrystalline Si. The anisotropy, the ratio of etch rates in vertical and horizontal directions, was larger than 25. The selectivity, the ratio of polycrystalline Si and SiO 2 etch rates, was larger than 1000. The Cl/sup */ 2 beam was produced by free jet expansion of a Cl 2 gas heated in a graphite furnace. The furnace temperature was 830 0 C. The substrate temperature was 180 0 C. The average total energy (0.38 eV) of a Cl/sup */ 2 molecule impinging on a substrate surface is much lower than the critical energy (approximately 10 eV) to displace the atoms of the etched material and to cause surface damage. This is the essential reason why this highly selective and almost damage-free etching has been achieved. The highly anisotropic etching mechanism is explained by a model taking into account the directional incidence of Cl/sup */ 2 molecules to the surface, and the deactivation process of the Cl/sup */ 2 molecules on a cold surface

Molecule Matters van der Waals Molecules

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 15; Issue 7. Molecule Matters van der Waals Molecules - Rg•••HF Complexes are Debye Molecules! E Arunan. Feature Article Volume 15 Issue 7 July 2010 pp 667-674. Fulltext. Click here to view fulltext PDF. Permanent link:

Considerations involved in the design of negative-ion-based neutral beam systems

International Nuclear Information System (INIS)

Cooper, W.S.

1983-11-01

We consider the requirements and constraints for negative-ion-based neutral beam injection systems, and show how these are reflected in design considerations. We will attempt to develop a set of guidelines for users and developers to use to see how well (in a qualitative sense, at least) a particular neutral beam system fits a particular proposed need

High efficiency and high-energy intra-cavity beam shaping laser

International Nuclear Information System (INIS)

Yang, Hailong; Meng, Junqing; Chen, Weibiao

2015-01-01

We present a technology of intra-cavity laser beam shaping with theory and experiment to obtain a flat-top-like beam with high-pulse energy. A radial birefringent element (RBE) was used in a crossed Porro prism polarization output coupling resonator to modulate the phase delay radially. The reflectively of a polarizer used as an output mirror was variable radially. A flat-top-like beam with 72.5 mJ, 11 ns at 20 Hz was achieved by a side-pumped Nd:YAG zigzag slab laser, and the optical-to-optical conversion efficiency was 17.3%. (paper)

High efficiency and high-energy intra-cavity beam shaping laser

Science.gov (United States)

Yang, Hailong; Meng, Junqing; Chen, Weibiao

2015-09-01

We present a technology of intra-cavity laser beam shaping with theory and experiment to obtain a flat-top-like beam with high-pulse energy. A radial birefringent element (RBE) was used in a crossed Porro prism polarization output coupling resonator to modulate the phase delay radially. The reflectively of a polarizer used as an output mirror was variable radially. A flat-top-like beam with 72.5 mJ, 11 ns at 20 Hz was achieved by a side-pumped Nd:YAG zigzag slab laser, and the optical-to-optical conversion efficiency was 17.3%.

Radiation pressure calibration and test mass reflectivities for LISA Pathfinder

International Nuclear Information System (INIS)

Korsakova, Natalia; Kaune, Brigitte

2017-01-01

This paper describes a series of experiments which were carried out during the main operations of LISA Pathfinder. These experiments were performed by modulating the power of the measurement and reference beams. In one series of experiments the beams were sequentially switched on and off. In the other series of experiments the powers of the beams were modulated within 0.1% and 1% of the constant power. These experiments use recordings of the total power measured on the photodiodes to infer the properties of the Optical Metrology System (OMS), such as reflectivities of the test masses and change of the photodiode efficiencies with time. In the first case the powers are back propagated from the different photodiodes to the same place on the optical bench to express the unknown quantities in the measurement with the complimentary photodiode measurements. They are combined in the way that the only unknown left is the test mass reflectivities. The second experiment compared two estimates of the force applied to the test masses due to the radiation pressure that appears because of the beam modulations. One estimate of the force is inferred from the measurements of the powers on the photodiodes and propagation of this measurement to the test masses. The other estimation of the force is done by calculating it from the change in the main scientific output of the instrument – differential displacement of the two test masses. (paper)

Radiation pressure calibration and test mass reflectivities for LISA Pathfinder

Science.gov (United States)

Korsakova, Natalia; Kaune, Brigitte; LPF Collaboration

2017-05-01

This paper describes a series of experiments which were carried out during the main operations of LISA Pathfinder. These experiments were performed by modulating the power of the measurement and reference beams. In one series of experiments the beams were sequentially switched on and off. In the other series of experiments the powers of the beams were modulated within 0.1% and 1% of the constant power. These experiments use recordings of the total power measured on the photodiodes to infer the properties of the Optical Metrology System (OMS), such as reflectivities of the test masses and change of the photodiode efficiencies with time. In the first case the powers are back propagated from the different photodiodes to the same place on the optical bench to express the unknown quantities in the measurement with the complimentary photodiode measurements. They are combined in the way that the only unknown left is the test mass reflectivities. The second experiment compared two estimates of the force applied to the test masses due to the radiation pressure that appears because of the beam modulations. One estimate of the force is inferred from the measurements of the powers on the photodiodes and propagation of this measurement to the test masses. The other estimation of the force is done by calculating it from the change in the main scientific output of the instrument - differential displacement of the two test masses.

A sextupole-magnet as variable velocity selector for paramagnetic atomic beams in the thermal range

International Nuclear Information System (INIS)

Spindler, G.; Ebinghaus, H.; Steffens, E.

1974-01-01

The possibility of employing a sextupole-magnet as a velocity selector on account of its velocity dependent focusing properties for paramagnetic atomic beams is investigated. In comparison with a traditional velocity selector with rotating disks, a sextupole-magnet as velocity selector has the advantage of additional focusing and polarizing the atomic beam. Moreover it suppresses polymer molecules without an effective magnetic momentum of the electronic shell

Experimental studies of laser-generated translationally hot atoms and molecules

International Nuclear Information System (INIS)

Cousins, L.M.

1989-01-01

An important determinant of the outcome of a chemical interaction is the relative translational energy of the partners. This thesis focuses on the generation of translationally energetic atoms and molecules and the role of translational energy in chemical interactions. One set of studies examines the competitive pathways of reactions and energy transfer in hyperthermal collisions of fast H or D atoms with HF. The vibrational excitation of HF or DF is measured using a time- and wavelength-resolved infrared emission technique. The results suggest that different collision geometries can lead to markedly different mechanisms for vibrational excitation. Another set of experiments is performed with a goal to generate a repetitively pulsed source of molecules or atoms with translational energies in the 0.1-10 eV range. A pulsed UV laser is used to excite a molecular film, vaporizing a number of molecules near the surface of the film. The composition and velocity of these molecules are measured by their time-of-flight to a quadrupole mass spectrometer. Kinetic energies in the range of 0.1-10 eV are observed; the energies are continuously variable and the molecules can be repetitively and reproducibly generated. To establish the dynamics of the vaporization, the internal distributions of fast 0.1-0.7 eV NO molecules are measured using a laser multiphoton detection technique. These studies indicate that the translationally hot molecules are ejected rotationally cold, i.e. typically with only 3% of the energy in rotational excitation. The large disequilibrium between translation and rotation suggests that the vaporization occurs by a transient, nonequilibrium heating mechanism coupled with an adiabatic expansion. The result is additionally promising in light of the desire to produce fast beams of molecules with characterizable and narrow internal energy distributions

Observation of surface discharge on polymer films irradiated by electron beam

International Nuclear Information System (INIS)

Komatsubara, Minoru; Ishii, Masaru; Tsumura, Eiji.

1992-01-01

The surface discharge on dielectric surfaces of a spacecraft caused by spacecraft charging is simulated by using a high vacuum chamber equipped with an electron beam gun. Fluoroethylene-propylene (FEP) and polyethleneterephthalate (PET) films frequently employed as thermal control materials are irradiated by an electron beam until surface discharges occur, then the spectrum and waveform of emitted light of discharge, together with the current waveform of the discharge and the mass spectrum of the gas in the vacuum chamber are measured. In the range of 300 through 700 nm of the wavelength, light emission from CN radicals, C 2 radicals, CH radicals and hydrogen atoms are detected. From this result, it is suggested that water molecules in the residual gas and molecules in the structure of the specimen contribute the light emission. The spectroscopic observation of the light emission suggests that the discharge energy is concentrated on PET more than that on FEP. (author)

Interactions of molecules with surfaces. Progress report, 1 February 1985-31 January 1986

International Nuclear Information System (INIS)

Greene, E.F.

1986-01-01

The angular distributions of beams of Ne and Ar atoms scattered nearly elastically from LiF (100) at 294 K show structure that is obscured by inelastic scattering when the whole range of velocities leaving the crystal is recorded. Increased fluxes of neutral species in beams from an effusive source of alkali halide vapor observed when a beam of electrons is coaxial with the neutral beam are shown to be well accounted for by a model involving electron stimulated desorption of alkali atoms. A simple model is proposed for the compensation observed for changes of the preexponential factor and activation energy in rate coefficients for the desorption of molecules from surfaces undergoing surface phase transitions. The isomerization of perfluoroDewarbenzene to perfluorobenzene can be produced in yields of 10% after single energetic collisions with a surface of polytetrafluoroethylene. The yield of ions produced when a beam of Na atoms strikes a Si(111) surface is increased over the equilibrium value observed for thermal beams by a factor of 10 or more when the kinetic energy of the incoming atoms is increased to 14 eV. The yield is sensitive to the dynamics of electron exchange between the surface and the ion. 12 refs., 1 fig

XUV laser-produced plasma sheet beam and microwave agile mirror

International Nuclear Information System (INIS)

Shen, W.; Scharer, J.E.; Porter, B.; Lam, N.T.

1994-01-01

An excimer-laser (λ = 193 nm) produced plasma in an organic gas (TMAE) has been generated and studied. These studies have determined the ion-electron recombination coefficient and the photon absorption cross-section, of the neutral gas. The dependences of wave transmission, reflection and absorption on plasma density are obtained. A new optical system with an array of cylindrical XUV coated lenses has been implemented to form a plasma sheet to study its usage as agile mirror microwave reflector. The lens system expands the incident laser beam in X direction and compresses it in Y direction to form a sheet beam. The expanded beam then passes through a vacuum chamber filled with TMAE at 50--500 nTorr to produce the plasma sheet. Space-time measurements of the plasma density and temperature as measured by a Langmuir probe are presented. XUV optical measurements of the laser beam as measured by a photodiode are presented. Initial experiments have generated a plasma sheet of 5--10 mm x 11 cm with peak plasma density of 5 x 10 13 cm -3 . A microwave source will be utilized to study the agile mirror character of the plasma sheet. Modeling of the microwave reflection from the plasma profile will also be discussed

Surface chemical reactions induced by molecules electronically-excited in the gas

DEFF Research Database (Denmark)

Petrunin, Victor V.

2011-01-01

and alignment are taking place, guiding all the molecules towards the intersections with the ground state PES, where transitions to the ground state PES will occur with minimum energy dissipation. The accumulated kinetic energy may be used to overcome the chemical reaction barrier. While recombination chemical...... be readily produced. Products of chemical adsorption and/or chemical reactions induced within adsorbates are aggregated on the surface and observed by light scattering. We will demonstrate how pressure and spectral dependencies of the chemical outcomes, polarization of the light and interference of two laser...... beams inducing the reaction can be used to distinguish the new process we try to investigate from chemical reactions induced by photoexcitation within adsorbed molecules and/or gas phase photolysis....

Reflection properties of hydrogen ions at helium irradiated tungsten surfaces

International Nuclear Information System (INIS)

Doi, K; Tawada, Y; Kato, S; Sasao, M; Kenmotsu, T; Wada, M; Lee, H T; Ueda, Y; Tanaka, N; Kisaki, M; Nishiura, M; Matsumoto, Y; Yamaoka, H

2016-01-01

Nanostructured W surfaces prepared by He bombardment exhibit characteristic angular distributions of hydrogen ion reflection upon injection of 1 keV H + beam. A magnetic momentum analyzer that can move in the vacuum chamber has measured the angular dependence of the intensity and the energy of reflected ions. Broader angular distributions were observed for He-irradiated tungsten samples compared with that of the intrinsic polycrystalline W. Both intensity and energy of reflected ions decreased in the following order: the polycrystalline W, the He-bubble containing W, and the fuzz W. Classical trajectory Monte Carlo simulations based on Atomic Collision in Amorphous Target code suggests that lower atom density near the surface can make the reflection coefficients lower due to increasing number of collisions. (paper)

Effect of the selective adsorption on the reactive scattering process of molecular beams from stepped surfaces

International Nuclear Information System (INIS)

Garcia, N.

1977-01-01

An indicative proposal which may explain the diffusion of incident atomic beams scattered by a crystal surface is made in terms of the selective adsorption mechanism. In this sense, the stepped metallic surfaces present characteristics which enhance the displacements and the lifetimes of the beams on the surface. This may be important for increasing the exchange reactive scattering of molecules from crystal surfaces

[Aerodynamic focusing of particles and heavy molecules

International Nuclear Information System (INIS)

de la Mora, J.F.

1990-01-01

By accelerating a gas containing suspended particles or large molecules through a converging nozzle, the suspended species may be focused and therefore used to write fine lines on a surface. Our objective was to study the limits on how narrow this focal region could be as a function of particle size. We find that, for monodisperse particles with masses m p some 3.6 x 10 5 times larger than the molecular mass m of the carrier gas (diameters above some 100 angstrom), there is no fundamental obstacle to directly write submicron features. However, this conclusion has been verified experimentally only with particles larger than 0.1 μm. Experimental, theoretical and numerical studies on the defocusing role of Brownian motion for very small particles or heavy molecules have shown that high resolution (purely aerodynamic) focusing is impossible with volatile molecules whose masses are typically smaller than 1000 Dalton. For these, the minimal focal diameter after optimization appears to be 5√(m/m p ) times the nozzle diameter d n . But combinations of focused lasers and aerodynamic focusing appear as promising for direct writing with molecular precursors. Theoretical and numerical schemes capable of predicting the evolution of the focusing beam, including Brownian motion effects, have been developed, although further numerical work would be desirable. 11 refs

Ion beam analysis

International Nuclear Information System (INIS)

Bethge, K.

1995-01-01

Full text: Ion beam analysis is an accelerator application area for the study of materials and the structure of matter; electrostatic accelerators of the Van de Graaff or Dynamitron type are often used for energies up to a few MeV. Two types of machines are available - the single-ended accelerator type with higher beam currents and greater flexibility of beam management, or the tandem accelerator, limited to atomic species with negative ions. The accelerators are not generally installed at specialist accelerator laboratories and have to be easy to maintain and simple to operate. The most common technique for industrial research is Rutherford Back Scattering Spectrometry (RBS). Helium ions are the preferred projectiles, since at elevated energies (above 3 MeV) nuclear resonance scattering can be used to detect photons associated with target molecules containing elements such as carbon, nitrogen or oxygen. Due to the large amount of available data on nuclear reactions in this energy range, activation analysis (detecting trace elements by irradiating the sample) can be performed with charged particles from accelerators over a wider range of atoms than with the conventional use of neutrons, which is more suited to light elements. Resonance reactions have been used to detect trace metals such as aluminium, titanium and vanadium. Hydrogen atoms are vital to the material performance of several classes of materials, such as semiconductors, insulators and ceramics. Prudent selection of the projectile ion aids the analysis of hydrogen composition; the technique is then a simple measurement of the emitted gamma radiation. Solar cell material and glass can be analysed in this way. On a world-wide basis, numerous laboratories perform ion beam analysis for research purposes; considerable work is carried out in cooperation between scientific laboratories and industry, but only a few laboratories provide a completely commercial service

Nanopore formation on Au coated pyramid under electron beam irradiations (plasmonic nanopore on pyramid

Directory of Open Access Journals (Sweden)

Seong Soo Choi

2016-03-01

Full Text Available There have been tremendous interests about the single molecule analysis using a sold-state nanopore. The solid-state nanopore can be fabricated either by drilling technique, or diffusion technique by using electron beam irradiations. The solid-state SiN nanopore device with electrical detection technique recently fabricated, however, the solid-state Au nanopore with optical detection technique can be better utilized as the next generation single molecule sensor. In this report, the nanometer size openings with its size less than 10 nm on the diffused membrane on the 200 nm Au pyramid were fabricated by using field emission scanning electron microscopy (FESEM electron beam irradiations, transmission electron microscopy (TEM, etc. After the sample was being kept under a room environment for several months, several Au (111 clusters with ~6 nm diameter formed via Ostwald ripening are observed using a high resolution TEM imaging. The nanopore with Au nanoclusters on the diffused membrane can be utilized as an optical nanopore device. Keywords: Electron beam irradiation, Surface diffusion, Carbon contamination, Au cluster, Ostwald ripening

Beer-Lambert-Law Parametric Model of Reflectance Spectra for Dyed Fabrics

Science.gov (United States)

2016-06-06

reflections from layered systems (i.e., scattering matrix formulations) [12,13,14], the Kubelka-Munk theory of diffuse reflectance (and formulations...mode. The Lambda 1050 incorporated a double beam, 150 mm integrating sphere housing a photomultiplier tube (PMT) detector for the UV-Vis (175 – 860 nm...of the combined system of dye and fabric. This relation follows from the Beer-Lambert law and formalism of the scattering- matrix [20]. In particular

Development of a total reflection X-ray fluorescence spectrometer for ...

Indian Academy of Sciences (India)

Unknown

design and use of a peltier cooled solid state detector for energy dispersive detection. Alignment and ... X-ray beam at a glancing angle less than the critical angle at which total ... materials is < 1 so that external total reflection takes place at an ...

Simultaneous delivery of electron beam therapy and ultrasound hyperthermia using scanning reflectors: a feasibility study

International Nuclear Information System (INIS)

Moros, Eduardo G.; Straube, William L.; Klein, Eric E.; Yousaf, Muhammed; Myerson, Robert J.

1995-01-01

Purpose: The feasibility of simultaneously delivering external electron beam radiation and superficial hyperthermia using a scanning ultrasound reflector-array system (SURAS) was experimentally investigated and demonstrated. Methods and Materials: A new system uses a scanning reflector to distribute the acoustic energy from a planar ultrasound array over the surface of the target volume. External photon/electron beams can be concurrently delivered with hyperthermia by irradiating through the scanning reflectors. That is, this system enables the acoustic waves and the radiation beams to enter the target volume from the same direction. Reflectors were constructed of air-equivalent materials for maximum acoustic reflection and minimum radiation attenuation. Acoustically, the air reflectors were compared to brass reflectors (assumed ideal) for reflectivity and specular quality using several single transducers ranging in frequency from 0.68 to 4.8 MHz. The relative reflectivity was determined from acoustic power measurements using a force-balance technique. The specular quality was assessed by comparing the acoustic pressure fields reflected by air reflectors with those reflected by brass reflectors. Also, acoustic pressure fields generated by a SURAS prototype for two different arrays (2.24 and 4.5 MHz) were measured to investigate field distribution variations as a function of the distance separating the array and the scanning reflector. All pressure fields were measured with a hydrophone in a degassed water tank. Finally, to determine the effect of the air reflectors on electron dose distributions, these were measured using film in a water-equivalent solid phantom after passage of a 20 MeV electron beam through the SURAS. These measurements were performed with the reflector scanning continuously across the electron beam and at rest within the electron beam. Results: The measurements performed using single ultrasound transducers showed that the air reflectors had

Thermoacoustic focusing lens by symmetric Airy beams with phase manipulations

Science.gov (United States)

Liu, Chen; Xia, Jian-Ping; Sun, Hong-Xiang; Yuan, Shou-Qi

2017-12-01

We report the realization of broadband acoustic focusing lenses based on two symmetric thermoacoustic phased arrays of Airy beams, in which the units of thermoacoustic phase control are designed by employing air with different temperatures surrounded by rigid insulated boundaries and thermal insulation films. The phase delays of the transmitted and reflected units could cover a whole 2π interval, which arises from the change of the sound velocity of air induced by the variation of the temperature. Based on the units of phase control, we design the transmitted and reflected acoustic focusing lenses with two symmetric Airy beams, and verify the high self-healing focusing characteristic and the feasibility of the thermal insulation films. Besides, the influences of the bending angle of the Airy beam on the focusing performance are discussed in detail. The proposed acoustic lens has advantages of broad bandwidth (about 4.8 kHz), high focusing performance, self-healing feature, and simple structure, which enable it to provide more schemes for acoustic focusing. It has excellent potential applications in acoustic devices.

Image-rotating cavity designs for improved beam quality in nanosecond optical parametric oscillators

International Nuclear Information System (INIS)

Smith, Arlee V.; Bowers, Mark S.

2001-01-01

We show by computer simulation that high beam quality can be achieved in high-energy, nanosecond optical parametric oscillators by use of image-rotating resonators. Lateral walk-off between the signal and the idler beams in a nonlinear crystal creates correlations across the beams in the walk off direction, or equivalently, creates a restricted acceptance angle. These correlations can improve the beam quality in the walk-off plane. We show that image rotation or reflection can be used to improve beam quality in both planes. The lateral walk-off can be due to birefringent walk-off in type II mixing or to noncollinear mixing in type I or type II mixing

INFLUENCE OF LASER BEAM PROFILE ON LIGHT SCATTERING BY HUMAN SKIN DURING PHOTOMETRY BY ELLIPSOIDAL REFLECTORS

Directory of Open Access Journals (Sweden)

M. A. Bezuglyi

2018-01-01

Full Text Available The correct accounting of laser emitter parameters for improvement of diagnostic authenticity of methods of optical biomedical diagnostic is important problem for applied biophotonic tasks. The purpose of the current research is estimation of influence of energy distribution profile in transversal section of laser beam on light scattering by human skin layers at photometry by ellipsoidal reflectors.Biomedical photometer with ellipsoidal reflectors for investigation of biological tissue specimens in transmitted and reflected light uses laser probing radiation with infinitely thin, Gauss-type and uniform cross-section profile. Distribution of beams with denoted profiles, which consist of 20 million photons with wavelength 632.8 nm, was modeled by using of Monte-Carlo simulation in human skin layers (corneous layer, epidermis, derma and adipose tissue of various anatomic thickness and with ellipsoidal reflectors with focal parameter equal to 16.875 mm and eccentricity of 0.66.The modeling results represent that illuminance distribution in zones of photometric imaging is significantly influenced by the laser beam cross-section profile for various thickness of corneous layer and epidermis in transmitted and reflected light, and also derma in reflected light. Illuminance distribution for adipose tissue in reflected and transmitted light, and also derma in transmitted light, practically do not depend of laser beam profile for anatomic thicknesses, which are appropriate for human skin on various sections of body.There are represented results of modified Monte-Carlo simulation method for biomedical photometer with ellipsoidal reflectors during biometry of human skin layers. For highly scattered corneous layer and epidermis the illumination of middle and external rings of photometric images changes depending from the laser beam profile for more than 50 % in transmitted and 30 % in reflected light. For weakly scattering skin layers (derma and adipose layer

Quantitative assessment of the ion-beam irradiation induced direct damage of nucleic acid bases through FTIR spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Huang, Qing, E-mail: huangq@ipp.ac.cn [Key Laboratory of Ion Beam Bio-engineering, Institute of Technical Biology and Agriculture Engineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences (China); University of Science and Technology of China, Hefei 230029, Anhui (China); Su, Xi; Yao, Guohua; Lu, Yilin; Ke, Zhigang; Liu, Jinghua; Wu, Yuejin; Yu, Zengliang [Key Laboratory of Ion Beam Bio-engineering, Institute of Technical Biology and Agriculture Engineering, Hefei Institutes of Physical Science, Chinese Academy of Sciences (China)

2014-07-01

Energetic particles exist ubiquitously in nature, and when they hit DNA molecules in organisms, they may induce critical biological effects such as mutation. It is however still a challenge to measure directly and quantitatively the damage imposed by the energetic ions on target DNA molecules. In this work we attempted to employ Fourier transformation infrared (FTIR) spectroscopy to assess the ion-induced direct damage of four nucleic acid bases, namely, thymine (T), cytosine (C), guanine (G), and adenine (A), which are the building blocks of DNA molecules. The samples were prepared as thin films, irradiated by argon ion-beams at raised ion fluences, and in the meantime measured by FTIR spectroscopy for the damage in a quasi-in-situ manner. It was found that the low-energy ion-beam induced radiosensitivity of the four bases shows the sequence G > T > C > A, wherein the possible mechanism was also discussed.

How to measure load-dependent kinetics of individual motor molecules without a force clamp

DEFF Research Database (Denmark)

Sung, J.; Mortensen, Kim; Spudich, J.A.

2017-01-01

Single-molecule force spectroscopy techniques, including optical trapping, magnetic trapping, and atomic force microscopy, have provided unprecedented opportunities to understand biological processes at the smallest biological length scales. For example, they have been used to elucidate the molec......Single-molecule force spectroscopy techniques, including optical trapping, magnetic trapping, and atomic force microscopy, have provided unprecedented opportunities to understand biological processes at the smallest biological length scales. For example, they have been used to elucidate...... functions at the single molecule level, such as conformational changes and force-generation of individual motor proteins or force-dependent kinetics in molecular interactions. Here, we describe a new method, “Harmonic Force Spectroscopy (HFS).” With a conventional dual-beam optical trap and a simple...... concepts, experimental setup, step-by-step experimental protocol, theory, data analysis, and results....

Observing the motion of electrons in atoms and molecules

International Nuclear Information System (INIS)

McCarthy, I.E.; Weigold, E.

1981-07-01

The dynamic electronic structure of atoms and molecules can be directly observed by means of the (e,2e) reaction, which measures the distribution of energies and momenta of two electrons in coincidence after a knockout reaction initiated by an electron beam of known momentum incident on a molecular gas target. The molecular state for each event is identified by the electron separation energy. The recoil momentum for each event is known from the difference of measured initial and final momenta. It has been verified that values of this momentum are equal under suitable conditions to the momentum of the electron in the target immediately before knockout. Thus the spherically-averaged electron momentum distribution for each molecular orbital is measured. This is directly related to molecular orbitals calculated by the methods of quantum chemistry. Properties of different types of molecules obtained by this method are discussed

Beam, vacuum and walls, a 3-body interaction

International Nuclear Information System (INIS)

Arianer, J.

2002-11-01

The interactions between beams of accelerated particles, residual gas and walls involve complex physical processes. In most cases these interactions affect the quality of the vacuum and the value of the pressure. This course reviews all these interactions in a pedagogical and practical way that may be useful for any user of devices involving beams of particles. This document is made up of 6 chapters: 1) basic notions (Maxwell-Boltzmann distribution, kinematics of charged particles, collisions, excitation and ionization), 2) properties of beams (emittance, local effects, and synchrotron radiation), 3) interactions between residual gas and particle beams (Bremsstrahlung radiation, energy loss due to ionization, charge shift of ion beams, photo-absorption and photo-ionization, and slowing-down in a plasma), 4) surface properties (crystal structure, and interaction between surface and the residual gas), 5) interaction between the beam and walls (reflection and diffraction of electrons, secondary emission of electrons, desorption induced by electron and ion impacts, photon production, ion-wall interaction, sputtering, ion penetration, surface ionization and thermal-ionization), and 6) radiation-wall interaction (diffusion, damping, photo-electric effect, desorption induced by photons, pair production and laser-surface interaction). (A.C.)

Anomalous foreshock field-aligned beams observed by Cluster

Directory of Open Access Journals (Sweden)

K. Meziane

2011-10-01

Full Text Available We report occasional observations of two simultaneously distinct ion foreshock components recorded by the Cluster spacecraft upstream of the Earth's bow shock. In most occurrences, the lower-energy population originates as a field-aligned beam (FAB associated with quasi-perpendicular regions, which loses energy as the IMF rotates into oblique geometries. A second beam, with energies in excess of ~10 keV, appears sometimes in association with the onset of ultra-low frequency (ULF waves, and sometimes ahead of the appearance of the latter. Measurements from the mass spectrometer indicate that both beams consist of protons. While the lower-speed beam is well-accounted for by a known reflection mechanism, the non-radial IMF orientations as well as other arguments seem to rule out magnetosheath or magnetospheric sources for the higher energy component. The wave characteristics are typical of the oblique foreshock and we have found that they are in cyclotron-resonance with the low speed beam (FAB. These observations constitute a theoretical challenge since conventional mechanisms described in the literature cannot account for the production of beams at two different energies.

Electron-beam generated porous dextran gels: experimental and quantum chemical studies.

Science.gov (United States)

Naumov, Sergej; Knolle, Wolfgang; Becher, Jana; Schnabelrauch, Matthias; Reichelt, Senta

2014-06-01

The aim of this work was to investigate the reaction mechanism of electron-beam generated macroporous dextran cryogels by quantum chemical calculation and electron paramagnetic resonance measurements. Electron-beam radiation was used to initiate the cross-linking reaction of methacrylated dextran in semifrozen aqueous solutions. The pore morphology of the resulting cryogels was visualized by scanning electron microscopy. Quantum chemical calculations and electron paramagnetic resonance studies provided information on the most probable reaction pathway and the chain growth radicals. The most probable reaction pathway was a ring opening reaction and the addition of a C-atom to the double-bond of the methacrylated dextran molecule. First detailed quantum chemical calculation on the reaction mechanism of electron-beam initiated cross-linking reaction of methacrylated dextran are presented.

Evaluation of the NEG Coating Saturation Level after 3 Years of LHC Beam Operation

CERN Document Server

Bregliozzi, G; Jimenez, J M; Lanza, G; Porcelli, T

2013-01-01

The room temperature vacuum system of the Large Hadron Collider (LHC) at CERN has been designed to ensure vacuum stability and beam lifetime of 100 h with nominal current of 0.56 A per beam at 7 TeV of energy. The requirements for the interaction regions are moreover driven to minimize the background noise of the experiments, to keep the equivalent hydrogen gas density below 1013 molecules of H2 per m3. \

Latest polarization and beam characterization results of the Orsay polarized electron source

International Nuclear Information System (INIS)

Arianer, J.; Cohen, S.; Essabaa, S.; Frascaria, R.; Zerhouni, O.

1995-01-01

The Orsay polarized electron source based on the chemi-ionization of aligned He(2 3 S 1 ) atoms and CO 2 molecules is briefly described. The latest results concerning electron polarization and beam emittance are presented. The present development status is also discussed. (K.A.)

Transverse Laser Beam Shaping in High Brightness Electron Gun at ATF

CERN Document Server

Roychowdhury, S

2005-01-01

The brightness of electron beams from a photo injector is influenced by the transverse and longitudinal distribution of the laser beam illuminating the cathode. Previous studies at Brookhaven Accelerator Test Facility have shown that formation of an ideal e-beam with lowest transverse emittance requires uniform circular distribution of the emitted electrons. The use of the uniformly distributed power of the laser beam may not lead to that of the emitted electrons because of the non-uniform quantum efficiency. A proper shaping of the laser beam can compensate for this non-uniformity. In this paper we describe the use of digital light processing (DLP) technique based on digital mirror device (DMD) for spatial modulation of the laser beam, for measurements of the quantum efficiency map, and for creating the desirable e-beam density profiles. A DMD is aμelectronic mechanical system (MEMS) comprising of millions of highly reflectiveμmirrors controlled by underlying electronics. We present exper...

Simple methods of aligning four-circle diffractometers with crystal reflections

Energy Technology Data Exchange (ETDEWEB)

Mitsui, Y [Tokyo Univ. (Japan). Faculty of Pharmaceutical Sciences

1979-08-01

Simple methods of aligning four-circle diffractometers with crystal reflections are devised. They provide the methods to check (1) perpendicularity of chi plane to the incident beam, (2) zero point of 2theta and linearity of focus-chi center-receiving aperture and (3) zero point of chi.

A Starting Point for Fluorescence-Based Single-Molecule Measurements in Biomolecular Research

Directory of Open Access Journals (Sweden)

Alexander Gust

2014-09-01

Full Text Available Single-molecule fluorescence techniques are ideally suited to provide information about the structure-function-dynamics relationship of a biomolecule as static and dynamic heterogeneity can be easily detected. However, what type of single-molecule fluorescence technique is suited for which kind of biological question and what are the obstacles on the way to a successful single-molecule microscopy experiment? In this review, we provide practical insights into fluorescence-based single-molecule experiments aiming for scientists who wish to take their experiments to the single-molecule level. We especially focus on fluorescence resonance energy transfer (FRET experiments as these are a widely employed tool for the investigation of biomolecular mechanisms. We will guide the reader through the most critical steps that determine the success and quality of diffusion-based confocal and immobilization-based total internal reflection fluorescence microscopy. We discuss the specific chemical and photophysical requirements that make fluorescent dyes suitable for single-molecule fluorescence experiments. Most importantly, we review recently emerged photoprotection systems as well as passivation and immobilization strategies that enable the observation of fluorescently labeled molecules under biocompatible conditions. Moreover, we discuss how the optical single-molecule toolkit has been extended in recent years to capture the physiological complexity of a cell making it even more relevant for biological research.

Measurement and Analysis of Rotational Energy of Nitrogen Molecular Beam by REMPI

International Nuclear Information System (INIS)

Mori, H.; Yamaguchi, H.; Kataoka, K.; Sugiyama, N.; Ide, K.; Niimi, T.

2008-01-01

Molecular beams are powerful tools for diagnoses of solid surfaces and gas-surface interaction tests. Unfortunately, there are very few reports about experimental analysis of internal energy distribution (e.g. rotational energy) of molecular beams of diatomic or polyatomic molecules, because measurement of internal energy distribution is very difficult. Spectroscopic measurement techniques based on resonantly enhanced multiphoton ionization (REMPI) is very powerful for measurement in highly rarefied gas flows. In this study, the REMPI method is applied to measurement of rotational energy distribution of nitrogen molecular beams. The REMPI spectrum of the molecular beam indicates the rotational temperature higher than the translational temperature of 7.2 K estimated by assuming isentropic flows. The O and P branches of the REMPI spectrum correspond to the rotational temperature of 30 K, but the S branch of the spectrum deviates from that at 30 K. It seems to be because the non-equilibrium rotational energy distribution of the molecular beam deviates from the Boltzmann distribution.

Quadra-quantum Dots and Related Patterns of Quantum Dot Molecules:

Directory of Open Access Journals (Sweden)

Somsak Panyakeow

2010-10-01

Full Text Available Abstract Laterally close-packed quantum dots (QDs called quantum dot molecules (QDMs are grown by modified molecular beam epitaxy (MBE. Quantum dots could be aligned and cross hatched. Quantum rings (QRs created from quantum dot transformation during thin or partial capping are used as templates for the formations of bi-quantum dot molecules (Bi-QDMs and quantum dot rings (QDRs. Preferable quantum dot nanostructure for quantum computation based on quantum dot cellular automata (QCA is laterally close-packed quantum dot molecules having four quantum dots at the corners of square configuration. These four quantum dot sets are called quadra-quantum dots (QQDs. Aligned quadra-quantum dots with two electron confinements work like a wire for digital information transmission by Coulomb repulsion force, which is fast and consumes little power. Combination of quadra-quantum dots in line and their cross-over works as logic gates and memory bits. Molecular Beam Epitaxial growth technique called ‘‘Droplet Epitaxy” has been developed for several quantum nanostructures such as quantum rings and quantum dot rings. Quantum rings are prepared by using 20 ML In-Ga (15:85 droplets deposited on a GaAs substrate at 390°C with a droplet growth rate of 1ML/s. Arsenic flux (7–8×10-6Torr is then exposed for InGaAs crystallization at 200°C for 5 min. During droplet epitaxy at a high droplet thickness and high temperature, out-diffusion from the centre of droplets occurs under anisotropic strain. This leads to quantum ring structures having non-uniform ring stripes and deep square-shaped nanoholes. Using these peculiar quantum rings as templates, four quantum dots situated at the corners of a square shape are regrown. Two of these four quantum dots are aligned either or , which are preferable crystallographic directions of quantum dot alignment in general.

Ag-ZnO nanostructure for ANTA explosive molecule detection

Energy Technology Data Exchange (ETDEWEB)

Shaik, Ummar Pasha [Advanced Center of Research in High Energy Materials, University of Hyderabad, Hyderabad 500046 (India); Sangani, L. D. Varma [Centre for Advanced Studies in Electronics Science and Technology, School of Physics, University of Hyderabad (India); Gaur, Anshu [Department of Industrial Engineering, University of Trento, Via Sommarive9, Trento (Italy); Mohiddon, Md. Ahamad, E-mail: ahamed.vza@gmail.com [National Institute of Technology Andhra Pradesh, Tadepalliguem 534101, AP, India Phone : (+) 91-40-23134382, FAX: (+) 91-40-23010227 (India); Krishna, M. Ghanashyam [Advanced Center of Research in High Energy Materials, University of Hyderabad, Hyderabad 500046 (India); Centre for Advanced Studies in Electronics Science and Technology, School of Physics, University of Hyderabad (India); National Institute of Technology Andhra Pradesh, Tadepalliguem 534101, AP, India Phone : (+) 91-40-23134382, FAX: (+) 91-40-23010227 (India)

2016-05-23

Ag/ZnO nanostructure for surface enhanced Raman scattering application in the detection of ANTA explosive molecule is demonstrated. A highly rough ZnO microstructure was achieved by rapid thermal annealing of metallic Zn film. Different thickness Ag nanostructures are decorated over these ZnO microstructures by ion beam sputtering technique. Surface enhanced Raman spectroscopic studies carried out over Ag/ZnO substrates have shown three orders higher enhancement compared to bare Ag nanostructure deposited on the same substrate. The reasons behind such huge enhancement are discussed based on the morphology of the sample.

Liquid Atomization Induced by Pulse Laser Reflection underneath Liquid Surface

Science.gov (United States)

Utsunomiya, Yuji; Kajiwara, Takashi; Nishiyama, Takashi; Nagayama, Kunihito; Kubota, Shiro; Nakahara, Motonao

2009-05-01

We observed a novel effect of pulse laser reflection at the interface between transparent materials with different refractive indices. The electric field intensity doubles when a laser beam is completely reflected from a material with a higher refractive index to a material with a lower index. This effect appreciably reduces pulse laser ablation threshold of transparent materials. We performed experiments to observe the entire ablation process for laser incidence on the water-air interface using pulse laser shadowgraphy with high-resolution film; the minimum laser fluence for laser ablation at the water-air interface was approximately 12-16 J/cm2. We confirmed that this laser ablation occurs only when the laser beam is incident on the water-air interface from water. Many slender liquid ligaments extend like a milk crown and seem to be atomized at the tip. Their detailed structures can be resolved only by pulse laser photography using high-resolution film.

The role of Triton surfactant in anisotropic etching of {1 1 0} reflective planes on (1 0 0) silicon

Science.gov (United States)

Resnik, Drago; Vrtacnik, Danilo; Aljancic, Uros; Mozek, Matej; Amon, Slavko

2005-06-01

Etching characteristics and properties of {1 1 0} silicon crystal planes used as 45° optical mirrors for deflecting optical beams from/to optical fibers were investigated. Fiber aligning grooves and passive mirror-like planes were realized by wet micromachining of (1 0 0) silicon in KOH IPA and TMAH IPA systems. Implementation of Triton-x-100 surfactant as an additive to 25% TMAH in anisotropic etching of {1 1 0} silicon passive mirror planes is reported and discussed. It was found that Triton-x-100 contents in the range of 10 200 ppm to the 25% TMAH water etchant significantly increase the anisotropy mostly by decreasing the {1 1 0} etch rate and retaining the {1 0 0} etch rate. It is also shown that {1 1 0} surface roughness is substantially improved compared to two other etching systems. Furthermore, efficient convex corner underetching reduction is demonstrated. The results of optical characterization of passive mirrors with 632 nm incident light show reduced scattering of reflected optical beam due to improved microroughness for mirrors made by TMAH Triton. For the reflection of the optical beam with 1.33 µm and 1.54 µm wavelengths, sputtered layer of gold is used as reflective coating on silicon mirrors thus increasing the reflected optical beam intensity by an additional 8%.

The inelastic scattering of 2Pi [case (b)] molecules and an understanding of the differing Λ doublet propensities for molecules of π vs π3 orbital occupancy

International Nuclear Information System (INIS)

Dagdigian, P.J.; Alexander, M.H.; Liu, K.; Department of Chemistry, University of Maryland, College Park, Maryland 20742; Gas Phase Chemical Dynamics Group, Chemistry Division, Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439)

1989-01-01

The quantum formalism for the scattering of a diatomic molecule in a 2 Pi electronic state which is well described by Hund's case (b) limit is investigated here. For a particular JF/sub i/ yields J'F'/sub 1/ transition, quantum interference effects will lead to preferential population of one of the final state Λ doublet levels. The nonstatistical population of final state Λ doublet levels arises from an interference between terms in the expansion of the two electrostatic potential energy surfaces, of A' and A'' reflection symmetry, which describe the interaction between a molecule in a Pi electronic state and a closed-shell partner. The particular Λ doublet level preferred is opposite for molecules of π 1 vs π 3 electron occupancy. The physical origin of this reversal in the Λ doublet propensity is a direct reflection of the fact that for the former the A' potential surface is more repulsive since the sole π electron lies in the triatomic plane in this case, whereas for molecules of π 3 electron occupancy the A' surface is less repulsive than the A'' surface since for the A' surface only one of the three π electrons lies in the triatomic plane. The magnitude of these Λ doublet propensities is illustrated by calculated cross sections for the CH(X 2 Pi)--He system using the ab initio potential energy surfaces calculated by the Argonne theoretical group, and these cross sections are compared to those of the crossed molecular study of Liu and Macdonald [J. Chem. Phys. 61, xxxx (1989)]. A similar analysis is carried out for collisions of a molecule of π 3 electron occupancy and is illustrated by inelastic collisions of OH(X 2 Pi)

Impurity transport during neutral beam injection in the ISX-B tokamak

International Nuclear Information System (INIS)

Isler, R.C.; Crume, E.C.; Arnurius, D.E.; Murray, L.E.

1980-10-01

In ohmically heated ISX-B discharges, both the intrinsic iron impurity ions and small amounts of argon introduced as a test gas accumulate at the center of the plasma. But during certain beam-heated discharges, it appears that this accumulation does not take place. These results may reflect the conclusion of Stacey and Sigmar that momentum transferred from the beams to the plasma can inhibit inward impurity transport

Spatial dose and microdose distribution in tissues. Ionization, nuclear reactions, multiple scattering simulation of beam transport

International Nuclear Information System (INIS)

Jacquot, C.

1976-01-01

Computer simulation and nuclear emulsion and gelatin techniques enabled to give the total elastic and inelastic cross sections and to forecast the spatial microdose distributions in cells, nuclei and molecules. For this purpose, the transport of a beam into tissues having a given composition is calculated, the nuclear reactions are generated and the energy depositions in standard planes perpendicular to the beam are recorded

Design technique for all-dielectric non-polarizing beam splitter plate

Science.gov (United States)

Rizea, A.

2012-03-01

There are many situations when, for the proper working, an opto-electronic device requiring optical components does not change the polarization state of light after a reflection, splitting or filtering. In this paper, a design for a non-polarizing beam splitter plate is proposed. Based on certain optical properties of homogeneous dielectric materials we will establish a reliable thin film package formula, excellent for the start of optimization to obtain a 20-nm bandwidth non-polarizing beam splitter.

Electromagnetic ion beam instability upstream of the earth's bow shock

International Nuclear Information System (INIS)

Gary, S.P.; Gosling, J.T.; Forslund, D.W.

1981-01-01

The linear theory of the electromagnetic ion beam instability for arbitrary angles of propagation has been studied. The parameters considered in the theory are typical of the solar wind upstream of the earth's bow shock when a 'reflected' proton beam is present. Maximum growth occurs for propagation parallel to the ambient field B, but this instability also displays significant growth at wave-vectors oblique to B, Oblique, unstable modes seem to be the likely source of the compressive magnetic fluctuations recently observed in conjunction with 'diffuse' ion population. An energetic ion beam does not directly give rise to linear growth of either ion acoustic or whistler mode instabilities

Magnetic field modification of ultracold molecule-molecule collisions

International Nuclear Information System (INIS)

Tscherbul, T V; Suleimanov, Yu V; Aquilanti, V; Krems, R V

2009-01-01

We present an accurate quantum mechanical study of molecule-molecule collisions in the presence of a magnetic field. The work focuses on the analysis of elastic scattering and spin relaxation in collisions of O 2 ( 3 Σ g - ) molecules at cold (∼0.1 K) and ultracold (∼10 -6 K) temperatures. Our calculations show that magnetic spin relaxation in molecule-molecule collisions is extremely efficient except at magnetic fields below 1 mT. The rate constant for spin relaxation at T=0.1 K and a magnetic field of 0.1 T is found to be as large as 6.1x10 -11 cm -3 s -1 . The magnetic field dependence of elastic and inelastic scattering cross sections at ultracold temperatures is dominated by a manifold of Feshbach resonances with the density of ∼100 resonances per Tesla for collisions of molecules in the absolute ground state. This suggests that the scattering length of ultracold molecules in the absolute ground state can be effectively tuned in a very wide range of magnetic fields. Our calculations demonstrate that the number and properties of the magnetic Feshbach resonances are dramatically different for molecules in the absolute ground and excited spin states. The density of Feshbach resonances for molecule-molecule scattering in the low-field-seeking Zeeman state is reduced by a factor of 10.

A large angle cold neutron bender using sequential garland reflections for pulsed neutron source

Energy Technology Data Exchange (ETDEWEB)

Ebisawa, T.; Tasaki, S. [Kyoto Univ., Kumatori, Osaka (Japan). Research Reactor Inst; Soyama, K.; Suzuki, J. [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment

2001-03-01

We discuss a basic structure and performance of a new cold neutron bender using sequential garland reflections, in order to bend a neutron beam with large divergence by large angle. Using this bender for a pulsed neutron source we could not only avoid the frame overlap for cold neutrons but also install a plural spectrometers at a cold guide and obtain polarized neutron beams if necessary. (author)

A large angle cold neutron bender using sequential garland reflections for pulsed neutron source

International Nuclear Information System (INIS)

Ebisawa, T.; Tasaki, S.; Soyama, K.; Suzuki, J.

2001-01-01

We discuss a basic structure and performance of a new cold neutron bender using sequential garland reflections, in order to bend a neutron beam with large divergence by large angle. Using this bender for a pulsed neutron source we could not only avoid the frame overlap for cold neutrons but also install a plural spectrometers at a cold guide and obtain polarized neutron beams if necessary. (author)

Device for guiding a subthermal neutron beam and focussing device made of micro-neutron guides

International Nuclear Information System (INIS)

Marx, D.

1977-01-01

The invention concerns a device for guiding, in particular for diverting, a subthermal neutron beam with curved boundary surfaces at least in one level, whose sides towards the neutron beam are covered with at least one coating which reflects the subthermal neutrons completely. (orig./RW) [de

Studies of interstellar vibrationally-excited molecules

International Nuclear Information System (INIS)

Ziurys, L.M.; Snell, R.L.; Erickson, N.R.

1986-01-01

Several molecules thus far have been detected in the ISM in vibrationally-excited states, including H 2 , SiO, HC 3 N, and CH 3 CN. In order for vibrational-excitation to occur, these species must be present in unusually hot and dense gas and/or where strong infrared radiation is present. In order to do a more thorough investigation of vibrational excitation in the interstellar medium (ISM), studies were done of several mm-wave transitions originating in excited vibrational modes of HCN, an abundant interstellar molecule. Vibrationally-excited HCN was recently detected toward Orion-KL and IRC+10216, using a 12 meter antenna. The J=3-2 rotational transitions were detected in the molecule's lowest vibrational state, the bending mode, which is split into two separate levels, due to l-type doubling. This bending mode lies 1025K above ground state, with an Einstein A coefficient of 3.6/s. The J=3-2 line mode of HCN, which lies 2050K above ground state, was also observed toward IRC+10216, and subsequently in Orion-KL. Further measurements of vibrationally-excited HCN were done using a 14 meter telescope, which include the observations of the (0,1,0) and (0,2,0) modes towards Orion-KL, via their J=3-2 transitions at 265-267 GHz. The spectrum of the J=3-2 line in Orion taken with the 14 meter telescope, is shown, along with a map, which indicates that emission from vibrationally-excited HCN arises from a region probably smaller than the 14 meter telescope's 20 arcsec beam

Ultrasonic flaw detection in a monorail box beam

Science.gov (United States)

Zheng, Peng; Greve, David W.; Oppenheim, Irving J.

2009-03-01

A steel box beam in a monorail application is constructed with an epoxy grout wearing surface, precluding visual inspection of its top flange. This paper describes a sequence of experimental research tasks to develop an ultrasonic system to detect flaws (such as fatigue cracks) in that flange, and the results of a field test to demonstrate system performance. The problem is constrained by the fact that the flange is exposed only along its longitudinal edges, and by the fact that permanent installation of transducers at close spacing was deemed to be impractical. The system chosen for development, after experimental comparison of alternate technologies, features angle-beam ultrasonic transducers with fluid coupling to the flange edge; the emitting transducers create transverse waves that travel diagonally across the width of the flange, where an array of receiving transducers detect flaw reflections and flaw shadows. The system rolls along the box beam, surveying (screening) the top flange for the presence of flaws. In a first research task, conducted on a full-size beam specimen, we compared waves generated from different transducer locations, either the flange edge or the web face, and at different frequency ranges. At relatively low frequencies, such as 100 kHz, we observed Lamb wave modes, and at higher frequency, in the MHz range, we observed nearlylongitudinal waves with trailing pulses. In all cases we observed little attenuation by the wearing surface and little influence of reflection at the web-flange joints. At the conclusion of this task we made the design decision to use edgemounted transducers at relatively high frequency, with correspondingly short wavelength, for best scattering from flaws. In a second research task we conducted experiments at 55% scale on a steel plate, with machined flaws of different size, and detected flaws of target size for the intended application. We then compared the performance of bonded transducers, fluid

Shack-Hartmann reflective micro profilometer

Science.gov (United States)

Gong, Hai; Soloviev, Oleg; Verhaegen, Michel; Vdovin, Gleb

2018-01-01

We present a quantitative phase imaging microscope based on a Shack-Hartmann sensor, that directly reconstructs the optical path difference (OPD) in reflective mode. Comparing with the holographic or interferometric methods, the SH technique needs no reference beam in the setup, which simplifies the system. With a preregistered reference, the OPD image can be reconstructed from a single shot. Also, the method has a rather relaxed requirement on the illumination coherence, thus a cheap light source such as a LED is feasible in the setup. In our previous research, we have successfully verified that a conventional transmissive microscope can be transformed into an optical path difference microscope by using a Shack-Hartmann wavefront sensor under incoherent illumination. The key condition is that the numerical aperture of illumination should be smaller than the numerical aperture of imaging lens. This approach is also applicable to characterization of reflective and slightly scattering surfaces.

Effect of ion compensation of the beam space charge on gyrotron operation

Energy Technology Data Exchange (ETDEWEB)

Fokin, A. P.; Glyavin, M. Yu. [Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod 603950 (Russian Federation); Nusinovich, G. S. [Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, Maryland 20742-3511 (United States)

2015-04-15

In gyrotrons, the coherent radiation of electromagnetic waves takes place when the cyclotron resonance condition between the wave frequency and the electron cyclotron frequency or its harmonic holds. The voltage depression caused by the beam space charge field changes the relativistic cyclotron frequency and, hence, can play an important role in the beam-wave interaction process. In long pulse and continuous-wave regimes, the beam space charge field can be partially compensated by the ions, which appear due to the beam impact ionization of neutral molecules of residual gases in the interaction space. In the present paper, the role of this ion compensation of the beam space charge on the interaction efficiency is analyzed. We also analyze the effect of the electron velocity spread on the limiting currents and discuss some effects restricting the ion-to-beam electron density ratio in the saturation stage. It is shown that the effect of the ion compensation on the voltage depression caused by the beam space charge field can cause significant changes in the efficiency of gyrotron operation and, in some cases, even result in the break of oscillations.

Core excitation and de-excitation spectroscopies of free atoms and molecules

International Nuclear Information System (INIS)

Ueda, Kiyoshi

2006-01-01

This article provides a review of the current status of core excitation and de-excitation spectroscopy studies of free atoms molecules using a high-resolution soft X-ray monochromator and a high-resolution electron energy analyzer, installed in the soft X-ray photochemistry beam line at SPring-8. Experimental results are discussed for 1s excitation of Ne, O 1s excitation of CO and H 2 O, and F 1s excitation of CF 4 . (author)

Applications of capillary optics for focused ion beams

International Nuclear Information System (INIS)

Umezawa, Kenji

2014-01-01

This article introduces applications of focused ion beams (∼1 μm) with glass capillaries systems. A first report on the interaction between ion beams and glass capillaries was published in 1996. The guiding capabilities of glass capillaries were discovered due to ion reflection from inner wall of glass surfaces. Meanwhile, the similar optics have been already realized in focusing X-rays using glass capillaries. The basic technology of X-rays optics using glass capillaries had been developed in the 1980's and 1900's. Also, low energy atom scattering spectroscopy for insulator material analysis will be mentioned. (author)

Focused beam reflectance method as an innovative (PAT) tool to monitor in-line granulation process in fluidized bed.

Science.gov (United States)

Alshihabi, Firas; Vandamme, Thierry; Betz, Gabriele

2013-02-01

Fluidized bed granulation is a commonly used unit operation in the pharmaceutical industry. But still to obtain and control the desired granule size is challenging due to many process variables affecting the final product. Focused beam reflectance measurement (FBRM, Mettler-Toledo, Switzerland) is an increasingly popular particle growth analysis technique. FBRM tool was installed in two different locations inside a fluidized bed granulator (GPCG2, Glatt, Binzen) in order to monitor the granulation growth kinetics. An experimental design was created to study the effect of process variables using FBRM probe and comparing the results with the one's measured by sieve analysis. The probe location is of major importance to get smooth and robust curves. The excess feeding of binder solution might lead to agglomeration and thus to process collapse, however this phenomenon was clearly detected with FBRM method. On the other hand, the process variables at certain levels might affect the FBRM efficiency by blocking the probe window with sticky particles. A good correlation was obtained (R(2) = 0.95) between FBRM and sieve analysis mean particle size. The proposed in-line monitoring tool enables the operator to select appropriate process parameters and control the wet granulation process more efficiently.

Laboratory studies of ion-molecule reactions and interstellar chemistry

International Nuclear Information System (INIS)

Koyano, Inosuke

1989-01-01

Several types of laboratory studies have been performed on ion-molecule reactions relevant to the formation of the interstellar molecules. Special emphasis is placed on the formation, structure, and reactivity of the C 3 H 3 + ions, which are believed to play a key role in interstellar chemistry. When these ions are produced by the reaction of C 3 H 4+ with C 3 H 4 in a beam-gas arrangement, their times-of-flight (TOF) show abnormally broad distributions regardless of the sources of the reactant C 3 H 4 + ion (photoionization of allene, propyne, the cyclopropene) and the nature of the neutral reactant, while all other product ions from the same reaction show sharp TOF distributions. On the other hand, all C 3 H 3 + ions produced by unimolecular decomposition of energetic C 3 H 4 + ions show sharp TOF distribution. The peculiarity of the C 3 H 3 + ions manifested in these and other experiments is discussed in conjunction with interstellar chemistry

Scanning ion micro-beam techniques for measuring diffusion in heterogeneous materials

International Nuclear Information System (INIS)

Jenneson, P.M.; Clough, A.S.

1998-01-01

A raster scanning MeV micro-beam of 1 H + or 3 He + ions was used to study the diffusion of small molecules in heterogeneous materials. The location of elemental contaminants (heavier than Lithium) in polymer insulated cables was studied with 1 H micro-Particle Induced X-ray Emission (μPIXE). Concentration profiles of a deuterated molecule in a hair fibre were determined with 3 He micro-Nuclear Reaction Analysis (μNRA). Chlorine and heavy water (D 2 0) diffusion into cement pastes were profiled using a combination of 3 He μPIXE and μNRA. (authors)

Detecting high-density ultracold molecules using atom–molecule collision

International Nuclear Information System (INIS)

Chen, Jun-Ren; Kao, Cheng-Yang; Chen, Hung-Bin; Liu, Yi-Wei

2013-01-01

Utilizing single-photon photoassociation, we have achieved ultracold rubidium molecules with a high number density that provides a new efficient approach toward molecular quantum degeneracy. A new detection mechanism for ultracold molecules utilizing inelastic atom–molecule collision is demonstrated. The resonant coupling effect on the formation of the X 1 Σ + g ground state 85 Rb 2 allows for a sufficient number of more deeply bound ultracold molecules, which induced an additional trap loss and heating of the co-existing atoms owing to the inelastic atom–molecule collision. Therefore, after the photoassociation process, the ultracold molecules can be investigated using the absorption image of the ultracold rubidium atoms mixed with the molecules in a crossed optical dipole trap. The existence of the ultracold molecules was then verified, and the amount of accumulated molecules was measured. This method detects the final produced ultracold molecules, and hence is distinct from the conventional trap loss experiment, which is used to study the association resonance. It is composed of measurements of the time evolution of an atomic cloud and a decay model, by which the number density of the ultracold 85 Rb 2 molecules in the optical trap was estimated to be >5.2 × 10 11 cm −3 . (paper)

Circulating vascular cell adhesion molecule-1 in pre-eclampsia, gestational hypertension, and normal pregnancy: evidence of selective dysregulation of vascular cell adhesion molecule-1 homeostasis in pre-eclampsia.

Science.gov (United States)

Higgins, J R; Papayianni, A; Brady, H R; Darling, M R; Walshe, J J

1998-08-01

Our purpose was to investigate circulating levels of vascular cell adhesion molecule-1 in the peripheral and uteroplacental circulations during normotensive and hypertensive pregnancies. This prospective observational study involved 2 patient groups. Group 1 consisted of 22 women with pre-eclampsia and 30 normotensive women followed up longitudinally through pregnancy and post partum. There were an additional 13 women with established gestational hypertension. Group 2 consisted of 20 women with established pre-eclampsia and 19 normotensive control subjects undergoing cesarean delivery. Plasma levels of vascular cell adhesion molecule-1 were measured in blood drawn from the antecubital vein (group 1) and from both the antecubital and uterine veins (group 2). Data were analyzed by analysis of variance. In group 1 vascular cell adhesion molecule-1 levels did not change significantly throughout normal pregnancy and post partum. Women with established pre-eclampsia had increased vascular cell adhesion molecule-1 levels compared with the normotensive pregnancy group (P = .01). Vascular cell adhesion molecule-1 levels were not elevated in women with established gestational hypertension. In group 2 significantly higher levels of vascular cell adhesion molecule-1 were detected in the uteroplacental (P post partum, is not a feature of nonproteinuric gestational hypertension, and is not observed with other major leukocyte adhesion molecules. Induction of vascular cell adhesion molecule-1 expression in pre-eclampsia may contribute to leukocyte-mediated tissue injury in this condition or may reflect perturbation of other, previously unrecognized, functions of this molecule in pregnancy.

The spontaneous synchronized dance of pairs of water molecules

Energy Technology Data Exchange (ETDEWEB)

Roncaratti, Luiz F. [Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia (Italy); Instituto de Física, Universidade de Brasília, 70910-900 Brasília (Brazil); Cappelletti, David, E-mail: david.cappelletti@unipg.it; Pirani, Fernando [Dipartimento di Chimica, Biologia e Biotecnologie, Università degli Studi di Perugia, 06123 Perugia (Italy)

2014-03-28

Molecular beam scattering experiments have been performed to study the effect of long-range anisotropic forces on the collision dynamics of two small polar molecules. The main focus of this paper is on water, but also ammonia and hydrogen sulphide molecules have been investigated, and some results will be anticipated. The intermolecular distances mainly probed are of the order of 1 nm and therefore much larger than the molecular dimensions. In particular, we have found that the natural electric field gradient, generated by different spatial orientations of the permanent electric dipoles, is able to promote the transformation of free rotations into coupled pendular states, letting the molecular partners involved in the collision complex swinging to and fro around the field direction. This long-ranged concerted motion manifested itself as large increases of the magnitude of the total integral cross section. The experimental findings and the theoretical treatment developed to shed light on the details of the process suggest that the transformation from free rotations to pendular states depends on the rotational level of both molecules, on the impact parameter, on the relative collision velocity, on the dipole moment product and occurs in the time scale of picoseconds. The consequences of this intriguing phenomenon may be important for the interpretation and, in perspective, for the control of elementary chemical and biological processes, given by polar molecules, ions, and free radicals, occurring in several environments under various conditions.

The spontaneous synchronized dance of pairs of water molecules

International Nuclear Information System (INIS)

Roncaratti, Luiz F.; Cappelletti, David; Pirani, Fernando

2014-01-01

Molecular beam scattering experiments have been performed to study the effect of long-range anisotropic forces on the collision dynamics of two small polar molecules. The main focus of this paper is on water, but also ammonia and hydrogen sulphide molecules have been investigated, and some results will be anticipated. The intermolecular distances mainly probed are of the order of 1 nm and therefore much larger than the molecular dimensions. In particular, we have found that the natural electric field gradient, generated by different spatial orientations of the permanent electric dipoles, is able to promote the transformation of free rotations into coupled pendular states, letting the molecular partners involved in the collision complex swinging to and fro around the field direction. This long-ranged concerted motion manifested itself as large increases of the magnitude of the total integral cross section. The experimental findings and the theoretical treatment developed to shed light on the details of the process suggest that the transformation from free rotations to pendular states depends on the rotational level of both molecules, on the impact parameter, on the relative collision velocity, on the dipole moment product and occurs in the time scale of picoseconds. The consequences of this intriguing phenomenon may be important for the interpretation and, in perspective, for the control of elementary chemical and biological processes, given by polar molecules, ions, and free radicals, occurring in several environments under various conditions

Some simple ideas on x-ray reflection and grazing-incidence diffraction from thin surfactant films

DEFF Research Database (Denmark)

Kjær, K.

1994-01-01

For Langmuir films of long linear amphiphilic molecules at the air-water interface, grazing-incidence diffraction data resolved in terms of both the horizontal and vertical components of the scattering angle can be evaluated to a fair level of detail by means of a slide rule. Specular reflection ...... data require more sophisticated means although some rules of thumb can be formulated.......For Langmuir films of long linear amphiphilic molecules at the air-water interface, grazing-incidence diffraction data resolved in terms of both the horizontal and vertical components of the scattering angle can be evaluated to a fair level of detail by means of a slide rule. Specular reflection...

Controlling X-ray beam trajectory with a flexible hollow glass fibre

Energy Technology Data Exchange (ETDEWEB)

Tanaka, Yoshihito, E-mail: yotanaka@riken.jp [RIKEN, 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan); Kwansei Gakuin University, Gakuen, Sanda, Hyogo 669-1337 (Japan); Nakatani, Takashi; Onitsuka, Rena [Kwansei Gakuin University, Gakuen, Sanda, Hyogo 669-1337 (Japan); Sawada, Kei [RIKEN, 1-1-1 Kouto, Sayo-cho, Hyogo 679-5148 (Japan); Takahashi, Isao [Kwansei Gakuin University, Gakuen, Sanda, Hyogo 669-1337 (Japan)

2014-01-01

X-ray beam trajectory control has been performed by using a 1.5 m-long flexible hollow glass fibre. A two-dimensional scan of a synchrotron radiation beam was demonstrated for X-ray absorption mapping. A metre-length flexible hollow glass fibre with 20 µm-bore and 1.5 mm-cladding diameters for transporting a synchrotron X-ray beam and controlling the trajectory has been examined. The large cladding diameter maintains a moderate curvature to satisfy the shallow glancing angle of total reflection. The observed transmission efficiency was more than 20% at 12.4 keV. As a demonstration, a wide-area scan of a synchrotron radiation beam was performed to identify the elements for a fixed metal film through its absorption spectra.

Reflectivity and filtering characteristics of pyrolytic graphite

International Nuclear Information System (INIS)

Adib, M.; Abdel-Kawy, A.; Ashry, A.; Abbas, Y.; Wahba, W.

1988-01-01

The neutron transmission measurements through oriented pyrolytic graphite (P.G. crystal) were carried out in the wavelength band from 0.15 nm to 6.5 nm at different orientations of the (002) plane of the crystal w.r.t. the neutron beam direction. It was found that the P.G. crystal may be tuned for optimum scattering of second-order neutrons in the wavelength ranging between 0.112 nm and 0.425 nm, by adjusting the filter in an appropriate orientation. The reflectivity of (002), (004) and (006) planes of P.G. were measured and the following results are obtained: the reflectivity of (002) plane was found to be 99% by (transmission method). The ratio of the integrated intensity of the reflected neutrons from (004) and (006) is 3.14+-0.25 and is found to be in agreement with the calculated ratio. The measurements were performed using the fixed scattering angle spectrometer installed in front of the ET-RR-1 reactor horizontal channel

Molecular beam photoionization and gas-surface scattering

International Nuclear Information System (INIS)

Ceyer, S.T.

1979-09-01

The energetics of the ethylene ion-molecule reactions was investigated in more detail than previously possible in two body collision experiments by photoionization of the neutral van der Waals ethylene dimer. The stability of the (C 2 H 4 ) + C 2 H 4 ion-molecule collision complex has been determined to be 18.2 +- 0.5 kcal. The highest potential barriers along the reaction coordinate for decomposition of this collision complex into C 4 H 7 + + H and C 3 H 5 + + CH 3 have been determined to be 0 +- 1.5 and 8.7 +- 1.5 kcal. In a similar manner, the energetics of the solvated ethylene dimer ion was investigated by the photoionization of the ethylene trimer. The absolute proton affinity of NH 3 (203.6 +- 1.3 kcal/mole) and the proton solvation energies by more than one NH 3 have been determined by molecular beam photoionization. In addition, the NH 3 + -NH 3 interaction energy (0.79 +- 0.05 eV) was measured by photoionization of the neutral van der Waals dimer. These experiments have shown that photoionization of van der Waals clusters is a very powerful method of determining the energetics of gas phase proton solvation. The scattering of helium atomic beams from a high Miller index platinum surface that exhibits ordered, periodic steps on the atomic scale to probe the effect of atomic steps on the scattering distribution is explored. Rainbow scattering is observed when the step edges are perpendicular to the incident helium atoms. The design, construction and operation of a beam-surface scattering apparatus are described. The first data obtained in this apparatus are presented and the interesting dynamical aspects of the oxidation of D, D 2 and CO are discussed. 75 references

Ion-electron recombination in merged-beams experiments

International Nuclear Information System (INIS)

Schmidt, H.T.

1994-01-01

In the present thesis, studies of recombination processes applying the technique of merged beams of fast ions and electrons are described. The main advantage of this technique is that the low relative velocity of ions and electrons necessary for these investigations can be achieved, at the same time as the velocity of the ions relative to the molecules of the residual gas is high. The high ion velocity leads to a very low reaction cross section for the leading contribution to the background signal, the capture of electrons in collisions with residual gas molecules. The experimental technique is described, emphasizing the electron beam velocity distribution and its relation to the energy resolution of the experiments. The presentation of the process of electron cooling is aimed at introducing this process as a tool for merged-beams experiments in storage rings rather than investigating the process itself. The non-resonant process of radiative recombination for non-fully stripped ions, showing evidence of incomplete screening is presented. Experimental investigation of dielectronic recombination is presented. Results of measurements of this process for He-like ions form the Aarhus single-pass experiment and the Heidelberg storage ring experiment are compared. Recombination is reduced from being the aim of the investigation to being a tool for high-precision measurements of the lifetimes of the 1s2s 3 S metastable states of HE-like ions of boron, carbon, and nitrogen, performed at the Heidelberg storage ring. The experiment is concerned with the process of dissociative recombination of molecular hydrogen ions. The discussion of this experiment emphasizes the distribution of population on the different vibrational levels of the ions in the initial state. In particular, a laser photo-dissociation technique was introduced to reduce the number of initial levels in the experiment. (EG) 24 refs

Monte Carlo program for the cold neutron beam guide

International Nuclear Information System (INIS)

Yoshiki, H.

1985-02-01

A Monte Carlo program for the transport of cold neutrons through beam guides has been developed assuming that the neutrons follow the specular reflections. Cold neutron beam guides are normally used to transport cold neutrons (4 ∼ 10 Angstrom) to experimental equipments such as small angle scattering apparatus, TOF measuring devices, polarized neutron spectrometers, and ultra cold neutron generators, etc. The beam guide is about tens of meters in length and is composed from a meter long guide elements made up from four pieces of Ni coated rectangular optical glass. This report describes mathematics and algorithm employed in the Monte Carlo program together with the display of the results. The source program and input data listings are also attached. (Aoki, K.)

BEAM-ish: A Graphical User Interface for the Physical Characterization of Macromolecular Crystals

Science.gov (United States)

Lovelace, Jeff; Snell, Edward H.; Pokross, Matthew; Arvai, Andrew S.; Nielsen, Chris; Nguyen, Xuong; Bellamy, Henry D; Borgstahl, Gloria E. O.; Rose, M. Franklin (Technical Monitor)

2000-01-01

Crystal mosaicity is determined from the measurement of the reflection angular width and can be used as an indicator of crystal perfection. A new method has been developed that combines the use of unfocused synchrotron radiation, super-fine phi slicing and a CCD area detector to simultaneously measure the mosaicity of hundreds of reflections . The X-ray beam characteristics and Lorentz correction are deconvoluted from the resulting reflection widths to calculate the true crystal mosaicity.

Out-of-plane reflection and refraction of light by anisotropic optical antenna metasurfaces with phase discontinuities.

Science.gov (United States)

Aieta, Francesco; Genevet, Patrice; Yu, Nanfang; Kats, Mikhail A; Gaburro, Zeno; Capasso, Federico

2012-03-14

Experiments on ultrathin anisotropic arrays of subwavelength optical antennas display out-of-plane refraction. A powerful three-dimensional (3D) extension of the recently demonstrated generalized laws of refraction and reflection shows that the interface imparts a tangential wavevector to the incident light leading to anomalous beams, which in general are noncoplanar with the incident beam. The refracted beam direction can be controlled by varying the angle between the plane of incidence and the antenna array. © 2012 American Chemical Society

particle simulation for electrostatic oscillation of virtual cathode in relativistic electron beams

International Nuclear Information System (INIS)

Chen Deming; Wang Min

1990-01-01

The virtual cathode oscillation in relativistic electron beams is studied by a 1-D electrostatic particle simulation code with finite-size-particle model. When injection current is less than the space charge limiting current, electron beam propagates stably and transsmits completely. When injection current exceeds the space charge limit, its propagation is unstable, a part of electrons reflect and the other electrons transsmit. The position and potential of the virtual cathode caused by space charge effects oscillate periodically. When the beam current increases, the virtual cathode position closer to the injection plane and its oscillating region gets narrower, the virtual cathode potential decreases and its amplitude increases, the oscillation frequency increases above the beam plasma frequency

Preparation of highly oriented poly-diacetylene LB-films with ion beam irradiation

International Nuclear Information System (INIS)

Hosoi, F.; Aoki, Y.; Hagiwara, M.; Omichi, H.

1992-01-01

Langmuir-Blodgett (LB) films such as 10,12-heptacosa-diynoic acid, 10,12-pentacosa-diynoic acid, 10,12-tricosa-diynoic acid were irradiated with ion beam, electron beam and UV-light, and the effect of irradiation on morphology of the polymerized film was studied. A sharp and intense X-ray diffraction pattern with higher order peaks which was not observed in the original films was obtained by Fe + beam irradiation. The interlayer spacing of diacetylene molecules calculated from the X-ray diffraction experiment was much longer than that theoretically anticipated. Similar results were observed when LB-films were treated with Ar + beam of 1keV for a short time although there was little observation of polymerization. In contrast, the diffraction pattern of the films polymerized with UV-light was broad and weak, and higher order peaks disappeared with the increase in irradiation dose. (author)

Monolithic millimeter-wave diode array beam controllers: Theory and experiment

Science.gov (United States)

Sjogren, L. B.; Liu, H.-X. L.; Wang, F.; Liu, T.; Wu, W.; Qin, X.-H.; Chung, E.; Domier, C. W.; Luhmann, N. C., Jr.; Maserjian, J.

1992-01-01

In the current work, multi-function beam control arrays have been fabricated and have successfully demonstrated amplitude control of transmitted beams in the W and D bands (75-170 GHz). While these arrays are designed to provide beam control under DC bias operation, new designs for high-speed electronic and optical control are under development. These arrays will fill a need for high-speed watt-level beam switches in pulsed reflectometer systems under development for magnetic fusion plasma diagnostics. A second experimental accomplishment of the current work is the demonstration in the 100-170 GHz (D band) frequency range of a new technique for the measurement of the transmission phase as well as amplitude. Transmission data can serve as a means to extract ('de-embed') the grid parameters; phase information provides more complete data to assist in this process. Additional functions of the array beam controller yet to be tested include electronically controlled steering and focusing of a reflected beam. These have application in the areas of millimeter-wave electronic scanning radar and reflectometry, respectively.

High-power direct diode laser output by spectral beam combining

Science.gov (United States)

Tan, Hao; Meng, Huicheng; Ruan, Xu; Du, Weichuan; Wang, Zhao

2018-03-01

We demonstrate a spectral beam combining scheme based on multiple mini-bar stacks, which have more diode laser combining elements, to increase the combined diode laser power and realize equal beam quality in both the fast and slow axes. A spectral beam combining diode laser output of 1130 W is achieved with an operating current of 75 A. When a 9.6 X de-magnifying telescope is introduced between the output mirror and the diffraction grating, to restrain cross-talk among diode laser emitters, a 710 W spectral beam combining diode laser output is achieved at the operating current of 70 A, and the beam quality on the fast and slow axes of the combined beam is about 7.5 mm mrad and 7.3 mm mrad respectively. The power reduction is caused by the existence of a couple resonator between the rear facet of the diode laser and the fast axis collimation lens, and it should be eliminated by using diode laser chips with higher front facet transmission efficiency and a fast axis collimation lens with lower residual reflectivity.

Full-angle Negative Reflection with An Ultrathin Acoustic Gradient Metasurface: Floquet-Bloch Modes Perspective and Experimental Verification

KAUST Repository

Liu, Bingyi

2017-07-01

Metasurface with gradient phase response offers new alternative for steering the propagation of waves. Conventional Snell\\'s law has been revised by taking the contribution of local phase gradient into account. However, the requirement of momentum matching along the metasurface sets its nontrivial beam manipulation functionality within a limited-angle incidence. In this work, we theoretically and experimentally demonstrate that the acoustic gradient metasurface supports the negative reflection for full-angle incidence. The mode expansion theory is developed to help understand how the gradient metasurface tailors the incident beams, and the full-angle negative reflection occurs when the first negative order Floquet-Bloch mode dominates. The coiling-up space structures are utilized to build desired acoustic gradient metasurface and the full-angle negative reflections have been perfectly verified by experimental measurements. Our work offers the Floquet-Bloch modes perspective for qualitatively understanding the reflection behaviors of the acoustic gradient metasurface and enables a new degree of the acoustic wave manipulating.

Highly anisotropic metasurface: a polarized beam splitter and hologram

Science.gov (United States)

Zheng, Jun; Ye, Zhi-Cheng; Sun, Nan-Ling; Zhang, Rui; Sheng, Zheng-Ming; Shieh, Han-Ping D.; Zhang, Jie

2014-01-01

Two-dimensional metasurface structures have recently been proposed to reduce the challenges of fabrication of traditional plasmonic metamaterials. However, complex designs and sophisticated fabrication procedures are still required. Here, we present a unique one-dimensional (1-D) metasurface based on bilayered metallic nanowire gratings, which behaves as an ideal polarized beam splitter, producing strong negative reflection for transverse-magnetic (TM) light and efficient reflection for transverse-electric (TE) light. The large anisotropy resulting from this TE-metal-like/TM-dielectric-like feature can be explained by the dispersion curve based on the Bloch theory of periodic metal-insulator-metal waveguides. The results indicate that this photon manipulation mechanism is fundamentally different from those previously proposed for 2-D or 3-D metastructures. Based on this new material platform, a novel form of metasurface holography is proposed and demonstrated, in which an image can only be reconstructed by using a TM light beam. By reducing the metamaterial structures to 1-D, our metasurface beam splitter exhibits the qualities of cost-efficient fabrication, robust performance, and high tunability, in addition to its applicability over a wide range of working wavelengths and incident angles. This development paves a foundation for metasurface structure designs towards practical metamaterial applications. PMID:25262791

Goos-Hänchen effect and bending of spin wave beams in thin magnetic films

International Nuclear Information System (INIS)

Gruszecki, P.; Krawczyk, M.; Romero-Vivas, J.; Dadoenkova, Yu. S.; Dadoenkova, N. N.; Lyubchanskii, I. L.

2014-01-01

For magnon spintronic applications, the detailed knowledge of spin wave (SW) beam dispersion, transmission (reflection) of SWs passing through (reflected from) interfaces, or borders or the scattering of SWs by inhomogeneities is crucial. These wave properties are decisive factors on the usefulness of a particular device. Here, we demonstrate, using micromagnetic simulations supported by an analytical model, that the Goos-Hänchen (GH) shift exists for SW reflecting from thin film edge and that with the effect becomes observable. We show that this effect will exist for a broad range of frequencies in the dipole-exchange range, with the magnetization degree of pinning at the film edge as the crucial parameter, whatever its nature. Moreover, we have also found that the GH effect can be accompanied or even dominating by a bending of the SW beam due to the inhomogeneity of the internal magnetic field. This inhomogeneity, created by demagnetizing field taking place at the film edge, causes gradual change of SWs refractive index. The refraction of the SW beams by the non-uniformity of the magnetic field enables the exploration of graded index magnonics and metamaterial properties for the transmission and processing of information at nanoscale

Goos-Hänchen effect and bending of spin wave beams in thin magnetic films

Energy Technology Data Exchange (ETDEWEB)

Gruszecki, P., E-mail: pawel.gruszecki@amu.edu.pl; Krawczyk, M., E-mail: krawczyk@amu.edu.pl [Faculty of Physics, Adam Mickiewicz University in Poznań, Umultowska 85, Poznań 61-614 (Poland); Romero-Vivas, J. [Department of Electronic and Computer Engineering, University of Limerick, Limerick (Ireland); Dadoenkova, Yu. S.; Dadoenkova, N. N. [Donetsk Physical and Technical Institute of the National Academy of Sciences of Ukraine, 83114 Donetsk (Ukraine); Ulyanovsk State University, 42 Leo Tolstoy str., 432000 Ulyanovsk (Russian Federation); Lyubchanskii, I. L. [Donetsk Physical and Technical Institute of the National Academy of Sciences of Ukraine, 83114 Donetsk (Ukraine)

2014-12-15

For magnon spintronic applications, the detailed knowledge of spin wave (SW) beam dispersion, transmission (reflection) of SWs passing through (reflected from) interfaces, or borders or the scattering of SWs by inhomogeneities is crucial. These wave properties are decisive factors on the usefulness of a particular device. Here, we demonstrate, using micromagnetic simulations supported by an analytical model, that the Goos-Hänchen (GH) shift exists for SW reflecting from thin film edge and that with the effect becomes observable. We show that this effect will exist for a broad range of frequencies in the dipole-exchange range, with the magnetization degree of pinning at the film edge as the crucial parameter, whatever its nature. Moreover, we have also found that the GH effect can be accompanied or even dominating by a bending of the SW beam due to the inhomogeneity of the internal magnetic field. This inhomogeneity, created by demagnetizing field taking place at the film edge, causes gradual change of SWs refractive index. The refraction of the SW beams by the non-uniformity of the magnetic field enables the exploration of graded index magnonics and metamaterial properties for the transmission and processing of information at nanoscale.

Cylinder and metal grating polarization beam splitter

Science.gov (United States)

Yang, Junbo; Xu, Suzhi

2017-08-01

We propose a novel and compact metal grating polarization beam splitter (PBS) based on its different reflected and transmitted orders. The metal grating exhibits a broadband high reflectivity and polarization dependence. The rigorous coupled wave analysis is used to calculate the reflectivity and the transmitting spectra and optimize the structure parameters to realize the broadband PBS. The finite-element method is used to calculate the field distribution. The characteristics of the broadband high reflectivity, transmitting and the polarization dependence are investigated including wavelength, period, refractive index and the radius of circle grating. When grating period d = 400 nm, incident wavelength λ = 441 nm, incident angle θ = 60° and radius of circle d/5, then the zeroth reflection order R0 = 0.35 and the transmission zeroth order T0 = 0.08 for TE polarization, however, T0 = 0.34 and R0 = 0.01 for TM mode. The simple fabrication method involves only single etch step and good compatibility with complementary metal oxide semiconductor technology. PBS designed here is particularly suited for optical communication and optical information processing.

Design of automatic tracking system for electron beam welding

International Nuclear Information System (INIS)

He Chengdan; Chinese Academy of Space Technology, Lanzhou; Li Heqi; Li Chunxu; Ying Lei; Luo Yan

2004-01-01

The design and experimental process of an automatic tracking system applied to local vacuum electron beam welding are dealt with in this paper. When the annular parts of an exactitude apparatus were welded, the centre of rotation of the electron gun and the centre of the annular weld are usually not superposed because of the machining error, workpiece's setting error and so on. In this teaching process, a little bundle of electron beam is used to scan the weld groove, the amount of the secondary electrons reflected from the workpiece is different when the electron beam scans the both sides and the centre of the weld groove. The difference can indicate the position of the weld and then a computer will record the deviation between the electron beam spot and the centre of the weld groove. The computer will analyze the data and put the data into the storage software. During the welding process, the computer will modify the position of the electron gun based on the deviation to make the electron beam spot centered on the annular weld groove. (authors)

Current Status of the Beam Position Monitoring System at TLS

Science.gov (United States)

Kuo, C. H.; Hu, K. H.; Chen, Jenny; Lee, Demi; Wang, C. J.; Hsu, S. Y.; Hsu, K. T.

2006-11-01

The beam position monitoring system is an important part of a synchrotron light source that supports its routine operation and studies of beam physics. The Taiwan light source is equipped with 59 BPMs. Highly precise closed orbits are measured by multiplexing BPMs. Data are acquired using multi-channel 16-bit ADC modules. Orbit data are sampled every millisecond. Fast orbit data are shared in a reflective memory network to support fast orbit feedback. Averaged data were updated to control database at a rate of 10 Hz. A few new generation digital BPMs were tested to evaluate their performance and functionality. This report summarizes the system structure, the software environment and the preliminary beam test of the BPM system.

A technique for simultaneous detection of individual vortex states of Laguerre-Gaussian beams transmitted through an aqueous suspension of microparticles

Science.gov (United States)

Khonina, S. N.; Karpeev, S. V.; Paranin, V. D.

2018-06-01

A technique for simultaneous detection of individual vortex states of the beams propagating in a randomly inhomogeneous medium is proposed. The developed optical system relies on the correlation method that is invariant to the beam wandering. The intensity distribution formed at the optical system output does not require digital processing. The proposed technique based on a multi-order phase diffractive optical element (DOE) is studied numerically and experimentally. The developed detection technique is used for the analysis of Laguerre-Gaussian vortex beams propagating under conditions of intense absorption, reflection, and scattering in transparent and opaque microparticles in aqueous suspensions. The performed experimental studies confirm the relevance of the vortex phase dependence of a laser beam under conditions of significant absorption, reflection, and scattering of the light.

Analytical and numerical studies of positive ion beam expansion for surface treatment applications

Science.gov (United States)

Lounes-Mahloul, Soumya; Bendib, Abderrezeg; Oudini, Noureddine

2018-01-01

The aim of this work is to study the expansion in vacuum, of a positive ion beam with the use of one dimensional (1D) analytic model and a two dimensional Particle-In-Cell (2D-PIC) simulation. The ion beam is extracted and accelerated from preformed plasma by an extraction system composed of two polarized parallel perforated grids. The results obtained with both approaches reveal the presence of a potential barrier downstream the extraction system which tends to reflect the ion flux. The dependence of the critical distance for which all extracted ions are reflected, is investigated as a function of the extracted ion beam current density. In particular, it is shown that the 1D model recovers the well-known Child-Langmuir law and that the 2D simulation presents a significant discrepancy with respect to the 1D prediction. Indeed, for a given value of current density, the transverse effects lead to a greater critical distance.

Ion-source dependence of the distributions of internuclear separations in 2-MeV HeH+ beams

International Nuclear Information System (INIS)

Kanter, E.P.; Gemmell, D.S.; Plesser, I.; Vager, Z.

1981-01-01

Experiments involving the use of MeV molecular-ion beams have yielded new information on atomic collisions in solids. A central part of the analyses of such experiments is a knowledge of the distribution of internuclear separations contained in the incident beam. In an attempt to determine how these distributions depend on ion-source gas conditions, we have studied foil-induced dissociations of H 2+ , H 3+ , HeH + , and OH 2+ ions. Although changes of ion-source gas compositions and pressure were found to have no measurable influence on the vibrational state populations of the beams reaching our target, for HeH + we found that beams produced in our rf source were vibrationally hotter than beams produced in a duoplasmatron. This was also seen in studies of neutral fragments and transmitted molecules

Reflectance-anisotropy study of the dynamics of molecular beam epitaxy growth of GaAs and InGaAs on GaAs(001)

Energy Technology Data Exchange (ETDEWEB)

Ortega-Gallegos, J.; Lastras-Martinez, A.; Lastras-Martinez, L.F. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi. Alvaro Obregon 64, San Luis Potosi (Mexico); Balderas-Navarro, R.E. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi. Alvaro Obregon 64, San Luis Potosi (Mexico); Facultad de Ciencias, Universidad Autonoma de San Luis Potosi. Alvaro Obregon 64, San Luis Potosi (Mexico)

2008-07-01

Reflectance-Anisotropy (RA) observations during the Molecular Beam Epitaxy (MBE) growth of zincblende semiconductors films were carried out using the E{sub 1} optical transition as a probe. We follow the kinetics of the deposition of GaAs and In{sub 0.3}Ga{sub 0.7}As on GaAs(001) at growth rates of 0.2 and 0.25 ML/s, respectively. During growth we used a constant As{sub 4} or As{sub 2} flux pressure of 5 x 10{sup -6} Torr. Clear RA-oscillations were observed during growth with a period that nearly coincides with the growth period for a Ga-As bilayer. RHEED was used as an auxiliary technique in order to obtain a correlation between RHEED and RA oscillations. On the basis of our results, we argue that RAS oscillations are mainly associated to periodic changes in surface atomic structure. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Reflectance-anisotropy study of the dynamics of molecular beam epitaxy growth of GaAs and InGaAs on GaAs(001)

International Nuclear Information System (INIS)

Ortega-Gallegos, J.; Lastras-Martinez, A.; Lastras-Martinez, L.F.; Balderas-Navarro, R.E.

2008-01-01

Reflectance-Anisotropy (RA) observations during the Molecular Beam Epitaxy (MBE) growth of zincblende semiconductors films were carried out using the E 1 optical transition as a probe. We follow the kinetics of the deposition of GaAs and In 0.3 Ga 0.7 As on GaAs(001) at growth rates of 0.2 and 0.25 ML/s, respectively. During growth we used a constant As 4 or As 2 flux pressure of 5 x 10 -6 Torr. Clear RA-oscillations were observed during growth with a period that nearly coincides with the growth period for a Ga-As bilayer. RHEED was used as an auxiliary technique in order to obtain a correlation between RHEED and RA oscillations. On the basis of our results, we argue that RAS oscillations are mainly associated to periodic changes in surface atomic structure. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

A fixed angle double mirror filter for preparing a pink undulator beam at the Advanced Photon Source

International Nuclear Information System (INIS)

Dufresne, E.; Sanchez, T.; Nurushev, T.; Clarke, R.; Dierker, S.B.

2000-01-01

Recent advances in X-ray Photon Correlation Spectroscopy (XPCS) use the full bandwidth of an undulator harmonic in order to maximize the coherent flux for small angle X-ray scattering experiments. X-ray mirrors and filters are typically used to select a given harmonic of the spectrum. At the University of Michigan/Howard University/Lucent Technologies, Bell Labs, Collaborative Access Team (MHATT-CAT) undulator beamline of the Advanced Photon Source, we have designed a fixed-angle Double Mirror Filter which will provide a 'pink beam' (i.e., 2-3% bandwidth) for XPCS experiments. This device uses two small mirrors which vertically reflect a 0.1 mmx0.1 mm white beam in a symmetric geometry. The doubly reflected beam propagates parallel to the incident white beam, but is offset vertically by 35 mm. Using the standard offset of the APS allows one to stop the white beam with a standard APS beam stop. In this report, we will describe our design considerations for this instrument. We also report the results of preliminary tests of the performance. The mirrors preserve the transverse coherence of the source, and filter the undulator spectrum as expected

Reaction dynamics of electronically excited alkali atoms with simpler molecules

International Nuclear Information System (INIS)

Weiss, P.S.; Mestdagh, J.M.; Schmidt, H.; Vernon, M.F.; Covinsky, M.H.; Balko, B.A.; Lee, Y.T.

1985-05-01

The reactions of electronically excited sodium atoms with simple molecules have been studied in crossed molecular beams experiments. Electronically excited Na(3 2 P/sub 3/2/, 4 2 D/sub 5/2/, and 5 2 S/sub 1/2/) were produced by optical pumping using single frequency dye lasers. The effects of the symmetry, and the orientation and alignment of the excited orbital on the chemical reactivity, and detailed information on the reaction dynamics were derived from measurements of the product angular and velocity distributions. 12 refs., 9 figs

Emerging science and technology of antimatter plasmas and trap-based beams

International Nuclear Information System (INIS)