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1

Cooperative mechanism for anchoring highly polar molecules at an ionic surface  

NASA Astrophysics Data System (ADS)

Structure formation of the highly polar molecule cytosine on the (111) cleavage plane of calcium fluoride is investigated in ultrahigh vacuum using noncontact atomic force microscopy at room temperature. Molecules form well-defined trimer structures, covering the surface as homogeneously distributed stable structures. Density-functional theory calculations yield a diffusion barrier of about 0.5 eV for individual molecules suggesting that they are mobile at room temperature. Furthermore, it is predicted that the molecules can form trimers in a configuration allowing all molecules to attain their optimum adsorption position on the substrate. As the trimer geometry facilitates hydrogen bonding between the molecules within the trimer, we conclude that the stabilization of individual diffusing molecules into stable trimers is due to a cooperative mechanism involving polar interactions between molecules and substrate as well as hydrogen bonding between molecules.

Schütte, J.; Bechstein, R.; Rohlfing, M.; Reichling, M.; Kühnle, A.

2009-11-01

2

High-order elliptically polarized harmonic generation in extended molecules with ultrashort intense bichromatic circularly polarized laser pulses  

SciTech Connect

Numerical solutions of the time-dependent Schroedinger equation (TDSE) for a two-dimensional H{sub 2}{sup +} molecule excited by a bichromatic ultrashort intense circularly polarized laser pulse with frequencies {omega}{sub 0} and 2{omega}{sub 0} and relative carrier envelope phase {phi} are used to explore the generation of high-order elliptically polarized harmonics as a function of internuclear distance R. Optimal values of {phi} and R for efficient and maximum molecular high-order harmonic generation (MHOHG) are determined from a classical model of collision with neighboring ions and confirmed from the TDSE nonperturbative simulations. Maximum elliptically polarized harmonic energies of I{sub p}+13.5U{sub p} are found, where I{sub p} is the ionization potential and U{sub p}=I{sub 0}/4m{sub e{omega}0}{sup 2} is the ponderomotive energy at intensity I{sub 0} and frequency {omega}{sub 0}. The polarization properties of MHOHG, phase difference {delta}, ellipticity {epsilon}, and orientation angle {phi} are presented as well. The high efficiency of the proposed MHOHG scheme should be useful for production of elliptically polarized attosecond extreme ultraviolet pulses.

Yuan, Kai-Jun; Bandrauk, Andre D. [Laboratoire de Chimie Theorique, Faculte des Sciences, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada)

2010-06-15

3

Nonadiabatic molecular high-order harmonic generation from polar molecules: Spectral redshift  

SciTech Connect

Molecular high-order harmonic generation (MHOHG) from the polar diatomic molecule HeH{sup 2+} in short intense laser fields is studied numerically. Due to the nonadiabatic response of the molecular dipole to the rapid change of laser intensity, a spectral redshift is predicted in high-intensity and ultrashort laser pulses, contrary to the blueshift observed in the harmonics generated from atoms in long laser pulses. The MHOHG temporal structures are investigated by a wavelet time-frequency analysis, which shows that the enhanced excitation of localized long lifetime excited states shifts the harmonic generation spectrum in the falling part of short laser pulses, due to the presence of a permanent dipole moment, and thus is unique to polar molecules.

Bian Xuebin; Bandrauk, Andre D. [Departement de Chimie, Universite de Sherbrooke, Sherbrooke, Quebec, J1K 2R1 (Canada)

2011-04-15

4

Qubit-induced high-order nonlinear interaction of the polar molecules in a stripline cavity  

SciTech Connect

By the exchange of virtual microwave photon induced by a stripline cavity, we present a collective spin-qubit model for the indirect interaction between a superconducting charge-phase qubit and an ensemble of the polar molecules. More importantly, the high-order nonlinear interaction among the polar molecules is generated successfully by using the SU(2) commutation relations of the qubit. Numerical simulation shows that this high-order nonlinear interaction can lead to a strong macroscopic quantum coherent effect, even if the parameters including the molecular number are small. For a large molecular number, the Kerr nonlinear interaction is also obtained. Moreover, it is found that this Kerr nonlinear parameter depends linearly on the molecular number, and as a result, has a giant value, which is 2 to 3 orders of magnitude larger than that in the other proposal schemes of the solid-state systems. Our results present a way to investigate the quantum nonlinear dynamics of the polar molecules.

Chen Gang [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Shanxi University, Taiyuan 030006 (China); Department of Physics, Shaoxing University, Shaoxing 312000 (China); Zhang Hao; Yang Yonggang; Xiao Liantuan; Jia Suotang [State Key Laboratory of Quantum Optics and Quantum Optics Devices, Shanxi University, Taiyuan 030006 (China); Wang Rui [Department of Physics, Zhejiang Ocean University, ZhouShan 316000 (China)

2010-07-15

5

Charge transfer processes in collisions of slow highly charged ions with polar molecules CO and C3H8  

Microsoft Academic Search

Charge transfer processes resulting from low energy collisions of polar molecules CO and C3H8 with highly charged Be2+ and B2+ ions have been investigated experimentally and theoretically. The potential for the one-electron exchange interaction between a polar molecule and highly charged atomic ion were obtained in closed analytical form in the framework of a semiclassical approach. Obtained results were used

M. V. Khoma; Makoto Imai; O. M. Karbovanets; Y. Kikuchi; M. Saito; Y. Haruyama; M. I. Karbovanets; I. Yu Kretinin; A. Itoh; R. J. Buenker

2009-01-01

6

High proton polarization at high temperature with single crystals of aromatic molecules  

NASA Astrophysics Data System (ADS)

Protons in single crystals of naphthalene doped with pentacene and p-terphenyl doped with pentacene have been polarized up to 32% and 18%, respectively. Such polarization has been achieved at liquid nitrogen temperature in a magnetic field of 3kG by means of microwave-induced optical nuclear polarization. We also measured the polarization by the neutron transmission method. The relaxation time at 77K in 7G was found to be about 3h and the enhancement of the obtained polarization compared with thermal polarization reached 8×104. This method is applicable to neutron experiments.

Iinuma, M.; Takahashi, Y.; Shaké, I.; Oda, M.; Masaike, A.; Yabuzaki, T.; Shimizu, H. M.

2004-08-01

7

High proton polarization at high temperature with single crystals of aromatic molecules  

Microsoft Academic Search

Protons in single crystals of naphthalene doped with pentacene and p-terphenyl doped with pentacene have been polarized up to 32% and 18%, respectively. Such polarization has been achieved at liquid nitrogen temperature in a magnetic field of 3kG by means of microwave-induced optical nuclear polarization. We also measured the polarization by the neutron transmission method. The relaxation time at 77K

M. Iinuma; Y. Takahashi; I. Shaké; M. Oda; A. Masaike; T. Yabuzaki; H. M Shimizu

2004-01-01

8

Charge transfer processes in collisions of slow highly charged ions with polar molecules CO and C3H8  

NASA Astrophysics Data System (ADS)

Charge transfer processes resulting from low energy collisions of polar molecules CO and C3H8 with highly charged Be2+ and B2+ ions have been investigated experimentally and theoretically. The potential for the one-electron exchange interaction between a polar molecule and highly charged atomic ion were obtained in closed analytical form in the framework of a semiclassical approach. Obtained results were used for close-coupling calculations of total cross sections for single electron transfer in the studied reactions.

Khoma, M. V.; Imai, Makoto; Karbovanets, O. M.; Kikuchi, Y.; Saito, M.; Haruyama, Y.; Karbovanets, M. I.; Kretinin, I. Yu; Itoh, A.; Buenker, R. J.

2009-04-01

9

Dipole-bound anions of highly polar molecules: ethylene carbonate and vinylene carbonate.  

PubMed

Results of experimental and theoretical studies of dipole-bound negative ions of the highly polar molecules ethylene carbonate (EC, C3H4O3, mu=5.35 D) and vinylene carbonate (VC, C3H2O3, mu=4.55 D) are presented. These negative ions are prepared in Rydberg electron transfer (RET) reactions in which rubidium (Rb) atoms, excited to ns or nd Rydberg states, collide with EC or VC molecules to produce EC- or VC- ions. In both cases ions are produced only when the Rb atoms are excited to states described by a relatively narrow range of effective principal quantum numbers, n*; the greatest yields of EC- and VC- are obtained for n*(max)=9.0+/-0.5 and 11.6+/-0.5, respectively. Charge transfer from low-lying Rydberg states of Rb is characteristic of a large excess electron binding energy (Eb) of the neutral parent; employing the previously derived empirical relationship Eb=23/n*(max)(2.8) eV, the electron binding energies are estimated to be 49+/-8 meV for EC and 24+/-3 meV for VC. Electron photodetachment studies of EC- show that the excess electron is bound by 49+/-5 meV, in excellent agreement with the RET results, lending credibility to the empirical relationship between Eb and n*(max). Vertical electron affinities for EC and VC are computed employing aug-cc-pVDZ atom-centered basis sets supplemented with a (5s5p) set of diffuse Gaussian primitives to support the dipole-bound electron; at the CCSD(T) level of theory the computed electron affinities are 40.9 and 20.1 meV for EC and VC, respectively. PMID:15267903

Hammer, Nathan I; Hinde, Robert J; Compton, Robert N; Diri, Kadir; Jordan, Kenneth D; Radisic, Dunja; Stokes, Sarah T; Bowen, Kit H

2004-01-01

10

The Electrical Polarity of Molecules  

Microsoft Academic Search

ON attempting to correlate the electrical double-refraction (Kerr effect) of gases and vapours which has been measured by Leiser, Hansen and Szivessy, with the optical anisotropy of the molecules determined from observations on light-scattering, it is found that electrically polar molecules generally exhibit a Kerr effect which is very large in relation to their optical anisotropy. This indicates that the

C. V. Raman; K. S. Krishnan

1926-01-01

11

Probing the origin of elliptical high-order harmonic generation from aligned molecules in linearly polarized laser fields  

SciTech Connect

A recent experiment [Phys. Rev. Lett. 102, 073902 (2009)] has demonstrated that elliptically polarized high-order harmonic generation can be produced from linearly polarized driving fields for aligned molecular systems. In order to reveal the underlying physical mechanisms of elliptical harmonics, we present fully ab initio and high-precision calculations and analyses of the amplitude, phase, and polarization state of the harmonic radiation from molecular hydrogen ions with arbitrary orientation. We find that high ellipticity arises from molecular orbital symmetry and two-center interference effects. Our ab initio exploration and findings lead to a general rule that the ellipticity becomes high for molecular orbitals represented by a symmetric combination of atomic orbitals, whereas it becomes low for molecular orbitals represented by an antisymmetric combination. This finding also applies to the general case of aligned linear molecules.

Son, Sang-Kil [Department of Chemistry, University of Kansas, Lawrence, Kansas 66045 (United States); Telnov, Dmitry A. [Department of Physics, St. Petersburg State University, St. Petersburg 198504 (Russian Federation); Chu, Shih-I. [Department of Chemistry, University of Kansas, Lawrence, Kansas 66045 (United States); Center for Quantum Science and Engineering, Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China)

2010-10-15

12

Quantum interference and multielectron effects in high-harmonic spectra of polar molecules  

NASA Astrophysics Data System (ADS)

We experimentally and theoretically analyze the manifestations of quantum interference and multiple ionization channels (multiple orbitals) in high-harmonic spectra of aligned N2O molecules. Increasing the probe wavelength from 1.17 to 1.46 ?m, we demonstrate the gradual disappearance of multielectron effects and quantitatively explain the observation through calculations. We thus identify a minimum in the high-harmonic spectrum of N2O caused only by its structure. By comparing its position with that measured in the isoelectronic CO2 molecule for similar axis distributions, we find a difference of 10 eV, confirmed by ab initio quantum scattering calculations. Quantum interference in photorecombination is thus shown to be sensitive to subtle differences in the valence orbital structure of molecules with nearly identical lengths. This property may find applications in time-resolved studies.

Rupenyan, A.; Kraus, P. M.; Schneider, J.; Wörner, H. J.

2013-03-01

13

Electron interactions with polar molecules  

SciTech Connect

A description is given of a number of the features of discrete and continuous spectra of electrons interacting with polar molecules. Attention is focused on the extent to which theoretical predictions concerning cross sections, resonances, and bound states are strongly influenced by the various approximations that are so ubiquitous in the treatment of such problems. Similarly, threshold scattering and photodetachment processes are examined for the case of weakly bound dipole states whose higher members overlap the continuum.

Garrett, W.R.

1981-01-01

14

Nuclear polarization of H2 molecules formed from polarized atoms  

Microsoft Academic Search

A planned experiment to measure the nuclear polarization of H2 molecules formed by recombination of polarized H atoms is described. Polarization will be measured with a longitudinally polarized 200 MeV proton beam and a longitudinally polarized storage cell gas target at the IUCF cooler ring. .

T. Wise; J. T. Balewski; W. W. Daehnick; J. Doskow; D. Friesel; W. Haeberli; H. Kolster; B. Lorentz; H. O. Meyer; P. V. Pancella; R. E. Pollock; B. V. Przewoski; P. A. Quin; F. Rathmann; T. Rinckel; Swapan K. Saha; B. Schwartz; A. Wellinghausen

2000-01-01

15

Collisional ionization of high-Rydberg lithium atoms in thermal-energy encounters with rapidly rotating polar molecules  

SciTech Connect

Ionization cross sections for high-Ryberg lithium atoms in collisions with the polar molecules NH/sub 3/, H/sub 2/O, and H/sub 2/S have been determined by analysis of time-of-flight distributions for a thermal beam of lithium atoms excited by pulsed electron impact. States with principal quantum numbers n in the range 20< or approx. =n< or approx. =75 are excited, with a peak in the distribution at napprox. =35. The cross sections are of order 10/sup -12/ cm/sup 2/ for all three molecules. Theoretical calculations are also described, based on the first Born approximation, in which the outermost Rydberg electron is assumed to be essentially free. This theory, as well as the calculation of Matsuzawa, slightly underestimates the experimental results.

Shepard, C.L.; Kocher, C.A.

1983-06-01

16

Nuclear Polarization of Hydrogen Molecules from Recombination of Polarized Atoms  

NASA Astrophysics Data System (ADS)

The nuclear polarization of H2 molecules formed by recombination of polarized H atoms on a Cu surface was measured as a function of external magnetic field and of temperature of the surface. The proton polarization of the molecules was determined by scattering of a longitudinally polarized 203-MeV proton beam in the Indiana University Cyclotron Facility storage ring. The nuclear polarization of the molecules, relative to the polarization of the atoms before recombination, increased from near zero in a weak magnetic field to 0.42+/-0.02 in a 0.66 T field. A simple model of the relaxation accounts quantitatively for the observations.

Wise, T.; Haeberli, W.; Lorentz, B.; Quin, P. A.; Rathmann, F.; Schwartz, B.; Walker, T. G.; Wellinghausen, A.; Balewski, J. T.; Doskow, J.; Meyer, H. O.; Pollock, R. E.; Przewoski, B. V.; Rinckel, T.; Saha, Swapan K.; Pancella, P. V.

2001-07-01

17

ATOMIC AND MOLECULAR PHYSICS: High order correlation-polarization potential for vibrational excitation scattering of diatomic molecules by low-energy electrons  

NASA Astrophysics Data System (ADS)

This paper introduces a correlation-polarization potential with high order terms for vibrational excitation in electron-molecule scattering. The new polarization potential generalizes the two-term approximation so that it can better reflect the dependence of correlation and polarization effects on the position coordinate of the scattering electron. It applies the new potential on the vibrational excitation scattering from N2 in an energy range which includes the 2?g shape resonance. The good agreement of theoretical resonant peaks with experiments shows that polarization potentials with high order terms are important and should be included in vibrational excitation scattering.

Feng, Hao; Sun, Wei-Guo; Zeng, Yang-Yang

2009-11-01

18

Microstructured Switchable Mirror for Polar Molecules  

NASA Astrophysics Data System (ADS)

By miniaturizing electrode geometries high electric fields can be produced using modest voltages. A planar array of 20 ?m wide gold electrodes, spaced 20 ?m apart, is made on a sapphire substrate. A voltage difference of up to 350V is applied to adjacent electrodes, generating an electric field that decreases exponentially with distance from the substrate. This microstructured array can be used as a mirror for polar molecules and can be rapidly switched on and off. This is demonstrated by retro­reflecting a beam of state-selected ammonia molecules with a forward velocity of about 30 m/s.

Schulz, Stephan A.; Bethlem, Hendrick L.; van Veldhoven, Jacqueline; Küpper, Jochen; Conrad, Horst; Meijer, Gerard

2004-07-01

19

Microstructured switchable mirror for polar molecules.  

PubMed

By miniaturizing electrode geometries high electric fields can be produced using modest voltages. A planar array of 20 microm wide gold electrodes, spaced 20 microm apart, is made on a sapphire substrate. A voltage difference of up to 350 V is applied to adjacent electrodes, generating an electric field that decreases exponentially with distance from the substrate. This microstructured array can be used as a mirror for polar molecules and can be rapidly switched on and off. This is demonstrated by retro-reflecting a beam of state-selected ammonia molecules with a forward velocity of about 30 m/s. PMID:15323886

Schulz, Stephan A; Bethlem, Hendrick L; van Veldhoven, Jacqueline; Küpper, Jochen; Conrad, Horst; Meijer, Gerard

2004-07-09

20

The Stark effect in Rydberg states of a highly polar diatomic molecule: CaF.  

PubMed

The Stark effect in molecular Rydberg states is qualitatively different from the Stark effect in atomic Rydberg states because of the anisotropy of the ion core and the existence of rotational and vibrational degrees of freedom. These uniquely molecular features cause the electric-field-induced decoupling of the Rydberg electron from the body frame to proceed in several stages in a molecule. Because the transition dipole moment among the same-n* Rydberg states is much larger than the permanent dipole moment of the ion core, the decoupling of the Rydberg electron from the ion core proceeds gradually. In the first stage, analyzed in detail in this paper, l and N are mixed by the external electric field, while N+ is conserved. In the further stages, as the external electric field increases, N+, n*, and v+ are expected to undergo mixing. We have characterized these stages in n*=13, v+=1 states of CaF. The large permanent dipole moment of CaF+ makes CaF qualitatively different from the other molecules in which the Stark effect in Rydberg states has been described (H2, Na2, Li2, NO, and H3) and makes it an ideal testbed for documenting the competition between the external and CaF+ dipole electric fields. We use the weak-field Stark effect to gain access to the lowest-N rotational levels of f, g, and h states and to assign their actual or nominal N+ quantum number. Lowest-N rotational levels provide information needed to disentangle the short-range and long-range interactions between the Rydberg electron and the ion core. We diagonalize an effective Hamiltonian matrix to determine the l-characters of the 3 < or = l < or = 5 core-nonpenetrating 2Sigma+ states and to characterize their mixing with the core-penetrating states. We conclude that the mixing of the l=4, N-N+=-4(g(-4)) state with lower-l 2Sigma+ states is stronger than documented in our previous multichannel quantum defect theory and long-range fits to zero-field spectra. PMID:19691382

Petrovi?, Vladimir S; Kay, Jeffrey J; Coy, Stephen L; Field, Robert W

2009-08-14

21

Trapping polar molecules in an ac trap  

SciTech Connect

Polar molecules in high-field seeking states cannot be trapped in static traps as Maxwell's equations do not allow a maximum of the electric field in free space. It is possible to generate an electric field that has a saddle point by superposing an inhomogeneous electric field to an homogeneous electric field. In such a field, molecules are focused along one direction, while being defocused along the other. By reversing the direction of the inhomogeneous electric field the focusing and defocusing directions are reversed. When the fields are being switched back and forth at the appropriate rate, this leads to a net focusing force in all directions. We describe possible electrode geometries for creating the desired fields and discuss their merits. Trapping of {sup 15}ND{sub 3} ammonia molecules in a cylindrically symmetric ac trap is demonstrated. We present measurements of the spatial distribution of the trapped cloud as a function of the settings of the trap and compare these to both a simple model assuming a linear force and to full three-dimensional simulations of the experiment. With the optimal settings, molecules within a phase-space volume of 270 mm{sup 3} (m/s){sup 3} remain trapped. This corresponds to a trap depth of about 5 mK and a trap volume of about 20 mm{sup 3}.

Bethlem, Hendrick L. [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); Laser Centre Vrije Universiteit, De Boelelaan 1081, NL-1081HV Amsterdam (Netherlands); Veldhoven, Jacqueline van [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); FOM-Institute for Plasmaphysics Rijnhuizen, P.O. Box 1207, NL-3430 BE Nieuwegein (Netherlands); Schnell, Melanie; Meijer, Gerard [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany)

2006-12-15

22

Optical production of ultracold polar molecules  

NASA Astrophysics Data System (ADS)

We present recent work resulting in the production of ultracold, polar RbCs molecules in their absolute vibronic ground state. The production process consists of several steps: photoassociation of laser-cooled atoms; radiative stabilization of the resulting molecules; identification of the resulting population distribution; and laser-stimulated stale transfer lo the vibrational ground state. We discuss the properties of the resulting sample of of X1?+(? = 0) molecules, with a view to the future directions of these experiments.

Demille, D.; Sage, J. M.; Sainis, S.; Bergeman, T.

2006-11-01

23

Fluorescence Polarization Assays in Small Molecule Screening  

PubMed Central

Importance of the field Fluorescence polarization (FP) is a homogeneous method that allows rapid and quantitative analysis of diverse molecular interactions and enzyme activities. This technique has been widely utilized in clinical and biomedical settings, including the diagnosis of certain diseases and monitoring therapeutic drug levels in body fluids. Recent developments in the field has been symbolized by the facile adoption of FP in high-throughput screening (HTS) and small molecule drug discovery of an increasing range of target classes. Areas covered in this review The article provides a brief overview on the theoretical foundation of FP, followed by updates on recent advancements in its application for various drug target classes, including G-protein coupled receptors (GPCRs), enzymes and protein-protein interactions (PPIs). The strengths and weaknesses of this method, practical considerations in assay design, novel applications, and future directions are also discussed. What the reader will gain The reader will be informed of the most recent advancements and future directions of FP application to small molecule screening. Take home message In addition to its continued utilization in high-throughput screening, FP has expanded into new disease and target areas and has been marked by increased use of labeled small molecule ligands for receptor binding studies.

Lea, Wendy A.; Simeonov, Anton

2011-01-01

24

Production and applications of ultracold polar molecules  

NASA Astrophysics Data System (ADS)

Ultracold polar molecules are of interest because of their strong, long-range, anisotropic dipole-dipole interactions, as well as their large intrinsic polarizability. Sources of such molecules have potential applications in fields as diverse as chemical physics, many-body physics and tests of fundamental symmetries. As an example, I will discuss our proposal to use ultracold polar molecules as the basis for a large-scale quantum computer [1]. Motivated by these applications, we have produced ultracold, polar RbCs molecules, in various vibrationally excited levels, via photoassociation of a laser-cooled mixture of Rb and Cs atoms. Using model potential curves which reproduce observed spectroscopic data, we infer the possibility to produce large numbers of ultracold polar molecules in their stable rovibrational ground state. We will also report on our recent efforts to verify the predictions of our model by directly measuring the number of molecules produced in particular states. [1] D. DeMille, Phys. Rev. Lett. 88, 067901 (2002).

Demille, David

2004-03-01

25

Strong-field approximation for ionization of a diatomic molecule by a strong laser field. III. High-order above-threshold ionization by an elliptically polarized field  

SciTech Connect

We investigate high-order above-threshold ionization (HATI) of diatomic molecules having different symmetries by an elliptically polarized laser field using the modified molecular strong-field approximation. The yields of high-energy electrons contributing to the plateau region of the photoelectron spectra strongly depend on the employed ellipticity. This is more pronounced if the major axis of the polarization ellipse is parallel or perpendicular to the molecular axis and at the end of the high-energy plateau. For the O{sub 2} molecule (characterized by {pi}{sub g} symmetry) the maximum yield is observed for some value of the ellipticity {epsilon} different from zero. On the other hand, in the same circumstances, the N{sub 2} molecule ({sigma}{sub g}) behaves as an atom, i.e., the yield is maximum for {epsilon}=0. These characteristics of the photoelectron spectra remain valid in a wide region of the molecular orientations and laser peak intensities. The symmetry properties of the molecular HATI spectra are considered in detail: by changing the molecular orientation one or other type of the symmetry emerges or disappears. Presenting differential ionization spectra in the ionized electron energy-emission angle plane we have observed similar interference effects as in the HATI spectra governed by a linearly polarized field.

Busuladzic, M. [Medical Faculty, University of Sarajevo, Cekalusa 90, 71000 Sarajevo (Bosnia and Herzegowina); Gazibegovic-Busuladzic, A. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegowina); Milosevic, D. B. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegowina); Max-Born-Institut, Max-Born-Strasse 2a, 12489 Berlin (Germany)

2009-07-15

26

Magnetic Trapping of Polar Molecules with Buffer-gas Cooling  

NASA Astrophysics Data System (ADS)

Molecules possess a number of features that could greatly expand the possibilities for study of new interactions, collective quantum effects, collisional processes, fundamental tests and chemical processes. This is due to 1) the strong interactions between the dipole moments of polar molecules, 2) the rotational and vibrational internal structure of all molecules, and 3) the easily orientable internal electric field of many polar molecules. The promise of cold and ultracold dipolar molecules will only be realized when samples can be prepared with at least approximately the same ease in which we now prepare atomic samples. Several approaches towards trapping of polar molecules, the key first step toward studying ultracold polar molecules at high density, have already succeeded: direct cooling of molecules via a buffer gas, mechanical slowing of a pulsed molecular beam with electric fields and photoassociation of alkali atoms. Over the past 5 years we have developed the technique of buffer-gas cooling and loading of molecules into magnetic traps, starting with the first trapping of a molecule, CaH, in 1998. Buffer-gas cooling relies solely on elastic collisions (thermalization) of the species-to-be-trapped with a cryogenically cooled helium gas and so is independent of any particular energy level pattern. Using buffer-gas loading, paramagnetic atoms (Cr, Eu, Mo) and molecules (CaH) have been trapped and several other species have been cooled (Na, Ti, Y, Zr, Sc, PbO, and NH) and their collisional properties studied. The process is found to be highly efficient; the number of trapped species limited only by the production method. The general method and recent results will be discussed including the cooling of molecules directly from a molecular beam and the creation of cold molecular beams.

Doyle, John

2004-03-01

27

Superconducting microwave cavity towards controlling the motion of polar molecules  

NASA Astrophysics Data System (ADS)

We propose the use of superconducting microwave cavities for the focusing and deceleration of cold polar molecular beams. A superconducting cavity with a high quality factor produces a large ac Stark shift in polar molecules, which allow us to efficiently control molecular motion. Our discussion is based on the experimental characterization of a prototype cavity: a lead-tin-coated cylindrical copper cavity, which has a quality factor of 106 and tolerates several watts of input power. Such a microwave device provides a powerful way to control molecules not only in low-field-seeking states, but also in high-field-seeking states such as the ground rotational state.

Enomoto, Katsunari; Djuricanin, Pavle; Gerhardt, Ilja; Nourbakhsh, Omid; Moriwaki, Yoshiki; Hardy, Walter; Momose, Takamasa

2012-10-01

28

Tunable Holstein model with cold polar molecules  

SciTech Connect

We show that an ensemble of polar molecules trapped in an optical lattice can be considered as a controllable open quantum system. The coupling between collective rotational excitations and the motion of the molecules in the lattice potential can be controlled by varying the strength and orientation of an external dc electric field as well as the intensity of the trapping laser. The system can be described by a generalized Holstein Hamiltonian with tunable parameters and can be used as a quantum simulator of excitation energy transfer and polaron phenomena. We show that the character of excitation energy transfer can be modified by tuning experimental parameters.

Herrera, Felipe; Krems, Roman V. [Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada)

2011-11-15

29

Lithium as a refrigerant for polar molecules  

NASA Astrophysics Data System (ADS)

Gases of ultracold polar molecules offer exciting new possibilities in many areas, including precision measurements [1], simulations of many-body quantum systems [2], and quantum information processing [3]. We aim to cool polar molecules by sympathetic cooling with ultracold atoms inside a suitable trap [4]. This poster presents our work on the production and transportation of a dense ultracold cloud of lithium for use as a refrigerant in sympathetic cooling. Up to 10^10 lithium atoms are loaded from a Zeeman slower into a magneto-optical trap. Using a moving magnetic trap the atoms are transported to a separate chamber where they will later be co-trapped with molecules. We present the design of our setup and our recent results on transport. We also explore the possibility of electrically polarizing the lithium so that dipole-dipole interactions become important in the gas.[4pt] [1] J. J. Hudson, D. M. Kara, I. J. Smallman, B. E. Sauer, M. R. Tarbutt and E. A. Hinds, Nature 473, 493 (2011).[0pt] [2] A. Micheli, G. K. Brennen, and P. Zoller, Nature Physics 2, 341 (2006).[0pt] [3] D. DeMille, Phys. Rev. Lett. 88, 067901 (2002).[0pt] [4] S. K. Tokunaga, W. Skomorowski, P. S. .Zuchowski, R. Moszynski, J. M. Hutson, E. A. Hinds and M. R. Tarbutt, Eur. Phys. J. D 65, 141 (2011).

Kaushik, A.; Tokunaga, S. K.; Hendricks, R. J.; Hinds, E. A.; Tarbutt, M. R.

2013-03-01

30

Dynamics of reactive ultracold alkali polar molecules  

NASA Astrophysics Data System (ADS)

Recently, ultracold polar molecules of KRb have been created. These molecules are chemically reactive and their lifetime in a trap is limited [1]. However, their lifetime increases when they are loaded into a 1D optical lattice in the presence of an electric field [2]. These results naturally raise the question of manipulating ultracold collisions of other species of alkali dimer molecules, with an eye toward both novel stereochemistry, as well as suppressing unwanted reactions, to enable condensed matter applications. In this talk, we report on a comparative study between the bi-alkali polar molecules of LiNa, LiK, LiRb, LiCs which have been predicted to be reactive [3]. We compute the isotropic C6 coefficients of these systems and we predict the elastic and reactive rate coefficients when an electric field is applied in a 1D optical lattice. We will discuss the efficacy of evaporative cooling for each species.[4pt] [1] Ni et al., Science 322, 231 (2008); Ospelkaus et al., Science 327, 853 (2010); Ni et al., Nature 464, 1324 (2010). [2] Qu'em'ener et al., Phys. Rev. A 81, 060701(R) (2010) ; Qu'em'ener et al., Phys. Rev. A 83, 012705 (2011); de Miranda et al., arXiv:1010.3731, to appear in Nature Physics. [3] Zuchowski et al., Phys. Rev. A 81, 060703(R) (2010).

Quéméner, Goulven; Bohn, John; Petrov, Alexander; Kotochigova, Svetlana

2011-06-01

31

Dynamics of thermal Casimir-Polder forces on polar molecules  

SciTech Connect

We study the influence of thermal Casimir-Polder forces on the near-surface trapping of cold polar molecules, with emphasis on LiH and YbF near a Au surface at room temperature. We show that even for a molecule initially prepared in its electronic and rovibrational ground state, the Casimir-Polder force oscillates with the molecule-wall separation. The nonresonant force and the evanescent part of the resonant force almost exactly cancel at high temperature which results in a saturation of the (attractive) force in this limit. This implies that the Casimir-Polder force on a fully thermalized molecule can differ dramatically from that obtained using a naive perturbative expansion of the Lifshitz formula based on the molecular ground-state polarizability. A dynamical calculation reveals how the spatial oscillations die out on a typical time scale of several seconds as thermalization of the molecule with its environment sets in.

Ellingsen, Simen Aadnoey; Buhmann, Stefan Yoshi; Scheel, Stefan [Department of Energy and Process Engineering, Norwegian University of Science and Technology, N-7491 Trondheim (Norway); Quantum Optics and Laser Science, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom)

2009-05-15

32

Vibrational relaxation rates of a polar molecule in polar liquids  

Microsoft Academic Search

Both the vibrational energy relaxation and pure dephasing of a polar solute in polar liquids are theoretically studied and particularly the role of the long-range Coulomb interaction between the solute and the polarization modes of the polar liquid is focused on in this paper. If the linear coupling potential between the vibrational displacement and the solvent polarization mode is taken

Minhaeng Cho

1996-01-01

33

Universal rates for reactive ultracold polar molecules in reduced dimensions.  

PubMed

Analytic expressions describe universal elastic and reactive rates of quasi-two-dimensional and quasi-one-dimensional collisions of highly reactive ultracold molecules interacting by a van der Waals potential. Exact and approximate calculations for the example species KRb show that stability and evaporative cooling can be realized for spin-polarized fermions at moderate dipole and trapping strength, whereas bosons or unlike fermions require significantly higher dipole or trapping strengths. PMID:20868041

Micheli, Andrea; Idziaszek, Zbigniew; Pupillo, Guido; Baranov, Mikhail A; Zoller, Peter; Julienne, Paul S

2010-08-13

34

Interlayer Superfluidity in Bilayer Systems of Fermionic Polar Molecules  

SciTech Connect

We consider fermionic polar molecules in a bilayer geometry where they are oriented perpendicularly to the layers, which permits both low inelastic losses and superfluid pairing. The dipole-dipole interaction between molecules of different layers leads to the emergence of interlayer superfluids. The superfluid regimes range from BCS-like fermionic superfluidity with a high T{sub c} to Bose-Einstein (quasi-)condensation of interlayer dimers, thus exhibiting a peculiar BCS-Bose-Einstein condensation crossover. We show that one can cover the entire crossover regime under current experimental conditions.

Pikovski, A.; Santos, L. [Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, 30169, Hannover (Germany); Klawunn, M. [Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, 30169, Hannover (Germany); INO-CNR BEC Center and Dipartimento di Fisica, Universita di Trento, 38123 Povo (Italy); Shlyapnikov, G. V. [Laboratoire de Physique Theorique et Modeles Statistique, Universite Paris Sud, CNRS, 91405 Orsay (France); Van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65/67, 1018 XE Amsterdam (Netherlands)

2010-11-19

35

Transport of polar molecules by an alternating-gradient guide  

SciTech Connect

An alternating-gradient electric guide provides a way to transport a wide variety of polar molecules, including those in high-field-seeking states. We investigate the motion of polar molecules in such a guide by measuring the transmission of CaF molecules in their high-field-seeking ground state, with the guide operating at a variety of switching frequencies and voltages. We model the guide using analytical and numerical techniques and compare the predictions of these models to the experimental results and to one another. The analytical results are approximate but provide simple and useful estimates for the maximum phase-space acceptance of the guide and for the switching frequency required. The numerical methods provide more accurate results over the full range of switching frequencies. Our investigation shows that, even when the fields are static, some high-field-seeking molecules are able to pass through the guide on metastable trajectories. We show that the maximum possible transmission requires accurate alignment within the guide and between the guide and detector.

Wall, T. E.; Armitage, S.; Hudson, J. J.; Sauer, B. E.; Dyne, J. M.; Hinds, E. A.; Tarbutt, M. R. [Centre for Cold Matter, Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2AZ (United Kingdom)

2009-10-15

36

Nonlocal state swapping of polar molecules in bilayers  

SciTech Connect

The observation of significant dipolar effects in gases of ultracold polar molecules typically demands a strong external electric field to polarize the molecules. We show that, even in the absence of a significant polarization, dipolar effects may play a crucial role in the physics of polar molecules in bilayers, provided that the molecules in each layer are initially prepared in a different rotational state. Then, interlayer dipolar interactions result in a nonlocal swap of the rotational state between molecules in different layers, even for weak applied electric fields. The interlayer scattering due to the dipole-dipole interaction leads to a nontrivial dependence of the swapping rate on density, temperature, interlayer spacing, and population imbalance. For reactive molecules such as KRb, chemical recombination immediately follows a nonlocal swap and dominates the losses even for temperatures well above quantum degeneracy, and hence could be observed under current experimental conditions.

Pikovski, A.; Santos, L. [Institut fuer Theoretische Physik, Leibniz Universitaet Hannover, Appelstrasse 2, D-30169 Hannover (Germany); Klawunn, M.; Recati, A. [Istituto Nazionale di Ottica del Consiglio Nazionale delle Ricerche (INO-CNR) BEC Center and Dipartimento di Fisica, Universita di Trento, I-38123 Povo (Italy)

2011-12-15

37

Scattering of Low-Energy Electrons from Polar Molecules.  

National Technical Information Service (NTIS)

Differential and total cross sections are predicted for low-energy collisions of electrons with polar molecules. The potential is due to a point dipole fixed to the molecule at its center of mass, the molecule is treated as a rigid rotator, and the first ...

O. H. Crawford

1967-01-01

38

Molecular polarizability in quantum defect theory: polar molecules  

SciTech Connect

The reduced-added Green's function technique in the quantum defect theory combines the advantages of analytical and ab initio methods in calculating frequency-dependent (dynamic) polarizabilities of atoms and molecules, providing an exact account for the high-excited and continuum electronic states. In the present paper this technique is modified to take into account the long-range dipole potential of a polar molecule core. The method developed is applied to calculation of the dynamic polarizability tensors of alkali-metal hydrides LiH and NaH as well as to some fluorides (CaF and BF) in the frequency range up to the first resonances. The results are in good agreement with ab initio calculations available for some frequencies.

Akindinova, E. V.; Chernov, V. E.; Kretinin, I. Yu.; Zon, B. A. [Voronezh State University, Voronezh RU-394693 (Russian Federation)

2010-04-15

39

Bound states and universality in layers of cold polar molecules  

Microsoft Academic Search

The recent experimental realization of cold polar molecules in the rotational and vibrational ground state opens the door to the study of a wealth of phenomena involving long-range interactions. By applying an optical lattice to a gas of cold polar molecules one can create a layered system of planar traps. Due to the long-range dipole-dipole interaction one expects a rich

J. R. Armstrong; N. T. Zinner; D. V. Fedorov; A. S. Jensen

2010-01-01

40

Spontaneous interlayer superfluidity in bilayer systems of cold polar molecules  

SciTech Connect

Recent experimental progress in producing ultracold polar molecules with a net electric dipole moment opens up possibilities for realizing quantum phases governed by the long-range and anisotropic dipole-dipole interactions. In this work we predict the existence of experimentally observable broken-symmetry states with spontaneous interlayer coherence in cold polar molecule bilayers. These exotic states, which are manifestations of collective bilayer quantum entanglement, appear due to strong repulsive interlayer interactions and exhibit properties of superfluids, ferromagnets, and excitonic condensates.

Lutchyn, Roman M.; Das Sarma, S. [Joint Quantum Institute, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States); Rossi, Enrico [Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)

2010-12-15

41

Prospects for making polar molecules with microwave fields.  

PubMed

We propose a mechanism to produce ultracold polar molecules with microwave fields. It converts trapped ultracold atoms into vibrationally excited molecules by a single microwave transition and entirely depends on the existence of a permanent dipole moment in the molecules. As opposed to production of molecules by photoassociation or magnetic-field Feshbach resonances, our method does not rely on properties of excited states or existence of Feshbach resonances. We determine conditions for optimal creation of polar molecules in vibrationally excited states of the ground-state potential by changing frequency and intensity of the microwave field. We also explore the possibility to produce vibrationally cold molecules by combining the microwave field with an optical Raman transition or by applying a microwave field to Feshbach molecules. The production mechanism is illustrated for KRb and RbCs. PMID:17930893

Kotochigova, Svetlana

2007-08-17

42

Polar confinement modulates solvation behavior of methane molecules  

NASA Astrophysics Data System (ADS)

Polar confinement induces an amorphous solidlike state of water characterized by an orientational correlation time longer than hundreds of picoseconds and significant structural disorder. Solvation behavior of methane molecules is dramatically modulated under polar confinement. Moreover our simulations indicate that the charges equivalent to those borne by atoms of amino acids could generate an electric field which is strong enough to stimulate the phase transition of water. In our results, polar confinement is found to be more capable of aggregating hydrophobic molecules. This study raises an interesting mechanism by which the cagelike structure of the Escherichia coli chaperonin GroEL and the cochaperonin GroES complex helps protein folding.

Xu, Weixin; Mu, Yuguang

2008-06-01

43

Designs of biased Stark guides for polar molecules  

NASA Astrophysics Data System (ADS)

Here we consider three possible biased electrostatic guides of polar molecules. The design of these guides is motivated by their possible uses in a precision measurement of the electron's electric dipole moment. These guides may also have applications in the alignment-preserving transportation of ultracold molecules.

Yang, Tao; Coker, James; Furneaux, J. E.; Shafer-Ray, N. E.

2012-06-01

44

Quantum phase gate and controlled entanglement with polar molecules  

SciTech Connect

We propose an alternative scenario for the generation of entanglement between rotational quantum states of two polar molecules. This entanglement arises from dipole-dipole interaction, and is controlled by a sequence of laser pulses simultaneously exciting both molecules. We study the efficiency of the process, and discuss possible experimental implementations with cold molecules trapped in optical lattices or in solid matrices. Finally, various entanglement detection procedures are presented, and their suitability for these two physical situations is analyzed.

Charron, Eric; Keller, Arne; Atabek, Osman [Laboratoire de Photophysique Moleculaire du CNRS, Universite Paris-Sud, Batiment 210, 91405 Orsay Cedex (France); Milman, Perola [Laboratoire de Photophysique Moleculaire du CNRS, Universite Paris-Sud, Batiment 210, 91405 Orsay Cedex (France); CERMICS, Ecole Nationale des Ponts et Chaussees, 6 et 8 av. Blaise Pascal, Cite Descartes, Champs-sur-Marne, 77455 Marne-la-Vallee (France)

2007-03-15

45

Polar steric interactions for V-shaped molecules.  

PubMed

We consider the effect of shape polarity in the excluded-volume interaction between V -shaped polar particles in orientationally ordered phases. We show that the polar component of the steric interaction between these polar particles, large enough in two space dimensions, can also become important in three space dimensions. Unexpectedly, polar steric interactions, up to now neglected, favor an "antiparallel" pair binding, which may be the building block of orientationally ordered phases for polar particles. An antiferromorphic smectic ordering, which is also antiferroelectric, could further be attained at high enough density by the same mechanism. PMID:18763971

Bisi, Fulvio; Rosso, Riccardo; Virga, Epifanio G; Durand, Georges E

2008-07-17

46

Synchrotron Storage Ring for Neutral Polar Molecules  

NASA Astrophysics Data System (ADS)

We have modeled the performance of a molecular synchrotron storage ring. Using 90 m/s deuterated ammonia (ND_3) as an example [1], we specify the shape, size, field, and placement of all of the electrostatic bending, focusing [2], bunching, and injection elements needed for a desk-top sized ring. With a newly developed code, we designed a race track lattice and tracked molecules for 400 turns to determine the dynamic aperture and momentum acceptance of the synchrotron storage ring. Results will be presented. [1] F. Crompvoets et al, Nature 411, 174 (2001) [2] J. Kalnins et. al., http://arXiv.org/abs/physics/0112073

Gould, Harvey

2002-05-01

47

A Comparison of Pair Potential for Some Polar and Non-Polar Mesogenic Molecules  

Microsoft Academic Search

Asymmetry of pair potential plays a crucial role in the formation of mesophases in molecular systems. Variation of such asymmetry is closely related to the constituents of the molecules as well as their positions. To investigate the asymmetry as well as its effect on molecular behavior, a few polar biphenyl and non-polar 2,5 disubstituted pyridine derivatives have been chosen. The

Shailendar Kumar Thakur; Mihir Roychoudhury

2012-01-01

48

Entanglement of polar symmetric top molecules as candidate qubits.  

PubMed

Proposals for quantum computing using rotational states of polar molecules as qubits have previously considered only diatomic molecules. For these the Stark effect is second-order, so a sizable external electric field is required to produce the requisite dipole moments in the laboratory frame. Here we consider use of polar symmetric top molecules. These offer advantages resulting from a first-order Stark effect, which renders the effective dipole moments nearly independent of the field strength. That permits use of much lower external field strengths for addressing sites. Moreover, for a particular choice of qubits, the electric dipole interactions become isomorphous with NMR systems for which many techniques enhancing logic gate operations have been developed. Also inviting is the wider chemical scope, since many symmetric top organic molecules provide options for auxiliary storage qubits in spin and hyperfine structure or in internal rotation states. PMID:22029292

Wei, Qi; Kais, Sabre; Friedrich, Bretislav; Herschbach, Dudley

2011-10-21

49

Single molecule polarization spectroscopy: pentacene in p-terphenyl  

Microsoft Academic Search

Polarized light spectroscopy has been performed on single pentacene molecules in p-terphenyl single crystals. Thin crystal flakes of p-terphenyl doped with a very low concentration of pentacene have been grown by sublimation. The orientation of the transition dipole moment of the pentacene molecules in the a?b?-plane of the crystal was determined by taking the birefringence of the crystalline matrix into

Frank Güttler; Mauro Croci; Alois Renn; Urs P. Wild

1996-01-01

50

Generation of W state and NOON state of distant polar molecules ensembles via a triple hybrid device  

NASA Astrophysics Data System (ADS)

A scheme is proposed to generate the W state and NOON state for the collective molecular modes of distant polar molecules ensembles via a triple hybrid device. Through the virtual excitation of the microwave photons of the transmission-line resonators, the interaction between the superconducting charge qubit and the polar molecules induces the entanglement for the collective modes of the polar molecules. The enhanced effective coupling strength between the superconducting charge qubit and the polar molecules enables to generate the W state and NOON state with high fidelity.

Chen, Mei-Feng; Zhang, Chun-Ling; Ma, Song-She

2013-10-01

51

Model Independence in Two Dimensions and Polarized Cold Dipolar Molecules  

SciTech Connect

We calculate the energy and wave functions of two particles confined to two spatial dimensions interacting via arbitrary anisotropic potentials with negative or zero net volume. The general rigorous analytic expressions are given in the weak coupling limit where universality or model independence are approached. The monopole part of anisotropic potentials is crucial in the universal limit. We illustrate the universality with a system of two arbitrarily polarized cold dipolar molecules in a bilayer. We discuss the transition to universality as a function of polarization and binding energy and compare analytic and numerical results obtained by the stochastic variational method. The universal limit is essentially reached for experimentally accessible strengths.

Volosniev, A. G.; Fedorov, D. V.; Jensen, A. S.; Zinner, N. T. [Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

2011-06-24

52

On the theory of the dielectric constant of dilute solutions of polar molecules in non-polar solvents  

Microsoft Academic Search

The dielectric constant of even a very dilute solution of polar molecules in non-polar solvents depends upon the geometry of how the non-polar molecules are arranged and how the polar molecules are placed relative to them. These are topological effects which the usual semi-macroscopic theories employing continuum approximations are inherently incapable of revealing. Their existence is demonstrated by making a

J. H. Van Vleck

1972-01-01

53

Single molecule polarization spectroscopy: pentacene in p-terphenyl  

NASA Astrophysics Data System (ADS)

Polarized light spectroscopy has been performed on single pentacene molecules in p-terphenyl single crystals. Thin crystal flakes of p-terphenyl doped with a very low concentration of pentacene have been grown by sublimation. The orientation of the transition dipole moment of the pentacene molecules in the a'/b'- plane of the crystal was determined by taking the birefringence of the crystalline matrix into account. An assignment of the pentacene sites O 1, O 2, O 3 and O 4 to the crystallographic position M 1, M 2, M 3 and M 4 of the p-terphenyl triclinic unit cell is proposed.

Güttler, Frank; Croci, Mauro; Renn, Alois; Wild, Urs P.

1996-11-01

54

Collective states in clusters of polar-polarizable molecules  

Microsoft Academic Search

Electrostatic interactions among polar-polarizable molecules in molecular materials, including crystals, aggregates, LB-films.., have important and non-trivial effects on the observed properties. We present a model that, based on a two-state description of each molecular site, encompasses the mean-field and excitonic models and leads to an internally consistent description of ground and optical properties of the material. Collective effects show up

Anna Painelli; Francesca Terenziani

2003-01-01

55

High intensity polarized electron sources  

SciTech Connect

The status of the polarized electron source development program at SLAC will be reviewed. Emission currents of 60 A, corresponding to a space charge limited current density of 180 A/cm/sup 2/, have been obtained from GaAs photocathodes. Electron beam polarization 20% greater than that obtainable from GaAs cathodes has been observed from multilayer GaAs-GaAlAs structures. Work in progress to produce high beam polarization from II-IV-V/sub 2/ chalcopyrite photocathodes will also be described.

Sinclair, C.K.

1980-10-01

56

XXI. The formation of molecular aggregates in radon-gas mixtures containing polar molecules  

Microsoft Academic Search

By various methods gaseous mixtures containing radon and its decay products have been investigated for the presence of molecular aggregates. Since in every case studied aggregates were obtained when the mixture contained polar molecules, and since in no case were aggregates detected when only non-polar molecules were present, it would appear that polar molecules definitely favour and are possibly essential

E. L. Harrington; O. A. Gratias

1931-01-01

57

Tunable disorder in a crystal of cold polar molecules  

SciTech Connect

We show that a two-species mixture of polar molecules trapped on an optical lattice gives rise to a system of rotational excitons in the presence of tunable impurities. The exciton-impurity interactions can be controlled by an external electric field, which can be exploited for quantum simulation of localization phenomena in disordered media. We demonstrate that an external electric field can be used to induce resonant enhancement of the exciton-impurity scattering cross sections and delocalization of excitonic states in a correlated one-dimensional disorder potential.

Herrera, Felipe; Krems, Roman V. [Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); Litinskaya, Marina [Department of Chemistry, University of British Columbia, Vancouver, British Columbia, V6T 1Z1 (Canada); Institute of Spectroscopy RAS, Troitsk, Moscow Region 142190 (Russian Federation)

2010-09-15

58

Stable Topological Superfluid Phase of Ultracold Polar Fermionic Molecules  

SciTech Connect

We show that single-component fermionic polar molecules confined to a 2D geometry and dressed by a microwave field may acquire an attractive 1/r{sup 3} dipole-dipole interaction leading to superfluid p-wave pairing at sufficiently low temperatures even in the BCS regime. The emerging state is the topological p{sub x}+ip{sub y} phase promising for topologically protected quantum information processing. The main decay channel is via collisional transitions to dressed states with lower energies and is rather slow, setting a lifetime of the order of seconds at 2D densities approx10{sup 8} cm{sup -2}.

Cooper, N. R. [TCM Group, University of Cambridge, Cavendish Laboratory, J. J. Thomson Avenue, Cambridge CB3 0HE (United Kingdom); Laboratoire de Physique Theorique et Modeles Statistiques, Universite Paris Sud, CNRS, 91405 Orsay (France); Shlyapnikov, G. V. [Laboratoire de Physique Theorique et Modeles Statistiques, Universite Paris Sud, CNRS, 91405 Orsay (France); van der Waals-Zeeman Institute, University of Amsterdam, Valckenierstraat 65/67, 1018 XE Amsterdam (Netherlands)

2009-10-09

59

Controllable surface electrostatic velocity filter for polar molecules  

NASA Astrophysics Data System (ADS)

We propose a scheme of a surface electrostatic velocity filter capable of preparing cold polar molecules on the surface of a substrate by selecting a low-velocity component of an effusive beam from a thermal gas reservoir. Using ND3 as a molecular sample, the dependence of the performance of the filter on the parameters of both the filter setup and the incident molecular beam is investigated by using a theoretical model and Monte Carlo simulations. A detailed study of the guiding process of molecules, including the evolution of phase space density of the packet in the filter, is carried out and shows that the beam selection process is mainly completed in the front part of the filter.

Hou, Shunyong; Wang, Qin; Deng, Lianzhong; Yin, Jianping

2013-07-01

60

High frequency dynamic nuclear polarization.  

PubMed

During the three decades 1980-2010, magic angle spinning (MAS) NMR developed into the method of choice to examine many chemical, physical, and biological problems. In particular, a variety of dipolar recoupling methods to measure distances and torsion angles can now constrain molecular structures to high resolution. However, applications are often limited by the low sensitivity of the experiments, due in large part to the necessity of observing spectra of low-? nuclei such as the I = 1/2 species (13)C or (15)N. The difficulty is still greater when quadrupolar nuclei, such as (17)O or (27)Al, are involved. This problem has stimulated efforts to increase the sensitivity of MAS experiments. A particularly powerful approach is dynamic nuclear polarization (DNP) which takes advantage of the higher equilibrium polarization of electrons (which conventionally manifests in the great sensitivity advantage of EPR over NMR). In DNP, the sample is doped with a stable paramagnetic polarizing agent and irradiated with microwaves to transfer the high polarization in the electron spin reservoir to the nuclei of interest. The idea was first explored by Overhauser and Slichter in 1953. However, these experiments were carried out on static samples, at magnetic fields that are low by current standards. To be implemented in contemporary MAS NMR experiments, DNP requires microwave sources operating in the subterahertz regime, roughly 150-660 GHz, and cryogenic MAS probes. In addition, improvements were required in the polarizing agents, because the high concentrations of conventional radicals that are required to produce significant enhancements compromise spectral resolution. In the last two decades, scientific and technical advances have addressed these problems and brought DNP to the point where it is achieving wide applicability. These advances include the development of high frequency gyrotron microwave sources operating in the subterahertz frequency range. In addition, low temperature MAS probes were developed that permit in situ microwave irradiation of the samples. And, finally, biradical polarizing agents were developed that increased the efficiency of DNP experiments by factors of ?4 at considerably lower paramagnet concentrations. Collectively, these developments have made it possible to apply DNP on a routine basis to a number of different scientific endeavors, most prominently in the biological and material sciences. This Account reviews these developments, including the primary mechanisms used to transfer polarization in high frequency DNP, and the current choice of microwave sources and biradical polarizing agents. In addition, we illustrate the utility of the technique with a description of applications to membrane and amyloid proteins that emphasizes the unique structural information that is available in these two cases. PMID:23597038

Ni, Qing Zhe; Daviso, Eugenio; Can, Thach V; Markhasin, Evgeny; Jawla, Sudheer K; Swager, Timothy M; Temkin, Richard J; Herzfeld, Judith; Griffin, Robert G

2013-04-18

61

Dynamic nuclear polarization at high magnetic fields  

PubMed Central

Dynamic nuclear polarization (DNP) is a method that permits NMR signal intensities of solids and liquids to be enhanced significantly, and is therefore potentially an important tool in structural and mechanistic studies of biologically relevant molecules. During a DNP experiment, the large polarization of an exogeneous or endogeneous unpaired electron is transferred to the nuclei of interest (I) by microwave (?w) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (?e/?l), being ?660 for protons. In the early 1950s, the DNP phenomenon was demonstrated experimentally, and intensively investigated in the following four decades, primarily at low magnetic fields. This review focuses on recent developments in the field of DNP with a special emphasis on work done at high magnetic fields (?5 T), the regime where contemporary NMR experiments are performed. After a brief historical survey, we present a review of the classical continuous wave (cw) DNP mechanisms—the Overhauser effect, the solid effect, the cross effect, and thermal mixing. A special section is devoted to the theory of coherent polarization transfer mechanisms, since they are potentially more efficient at high fields than classical polarization schemes. The implementation of DNP at high magnetic fields has required the development and improvement of new and existing instrumentation. Therefore, we also review some recent developments in ?w and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments.

Maly, Thorsten; Debelouchina, Galia T.; Bajaj, Vikram S.; Hu, Kan-Nian; Joo, Chan-Gyu; Mak-Jurkauskas, Melody L.; Sirigiri, Jagadishwar R.; van der Wel, Patrick C. A.; Herzfeld, Judith; Temkin, Richard J.; Griffin, Robert G.

2009-01-01

62

Measurement of pick-up cross-sections of He clusters: Polar versus non-polar molecules  

Microsoft Academic Search

Pick-up cross-sections of free large He clusters formed in free jet expansions have been measured to determine the influence of the molecular properties of target molecules in the capture process. The pick-up cross-section depends strongly on the dipole moment of the molecule. For non-polar molecules, earlier measurements of pick-up cross-sections ranging from 2000 to 4300 Å2 were ponfirmed; for polar

Henry Hessj; Delmar S. Larsen; Adi A. Scheidemann

1999-01-01

63

Measurement of pick-up cross-sections of 4He clusters: polar versus non-polar molecules  

Microsoft Academic Search

Pick-up cross-sections of free large 4He clusters formed in free jet expansions have been measured to determine the influence of the molecular properties of target molecules in the capture process. The pick-up cross-section depends strongly on the dipole moment of the molecule. For non-polar molecules, earlier measurements of pick-up cross-sections ranging from 2000 to 4300 A2 were confirmed; for polar

Henry Hess; Delmar S. Larsen; Adi A. Scheidemann

1999-01-01

64

Charge exchange of a polar molecule at its cation  

SciTech Connect

The Landau-Herring method is used to derive an analytic expression for the one-electron exchange interaction of a polar molecule with its positively charged ion, induced by a {sigma}-electron. Analogously to the classical Van der Pole method, the exchange interaction potential is averaged over the rotational states of colliding particles. The resonant charge-transfer cross section is calculated, and the effect of the dipole moments of the core on the cross section is analyzed. It is shown that allowance for the dependence of the exchange potential on the orientation of the dipole moments relative to the molecular axis may change the dependence of the cross section on the velocity of colliding particles, which is typical of the resonant charge exchange, from the resonance to the quasi-resonance dependence.

Buslov, E. Yu., E-mail: buslov@phys.vsu.ru; Zon, B. A., E-mail: zon@niif.vsu.ru [Voronezh State University (Russian Federation)

2011-01-15

65

Interaction of a polar molecule with an ion channel  

SciTech Connect

The binding of a polar macromolecule to a large ion channel is studied theoretically, paying special attention to the influence of external conditions (applied voltage and ion strength of solution). The molecule behavior in bound state is considered as random thermal fluctuations within a limited fraction of its phase space. The mean duration of molecule binding (residence time {tau}{sub r}) is represented as the mean first passage time to reach the boundary of that restricted domain. By invoking the adiabatic approximation we reduce the problem to one dimension with the angle between macromolecule dipole and channel axes being the key variable of the problem. The model accounts for experimental measurements of {tau}{sub r} for the antibiotic Ampicillin within the bacterial porin OmpF of Escherichia coli. By assuming that the electrical interaction between Ampicillin dipole and OmpF ionizable groups affects the fluctuations, we find that the biased residence time-voltage dependence observed in experiments is the result of the strong transversal electric field in OmpF constriction with a tilt {approx}30 deg. aside the cis side.

Levadny, V. [Departamento de Ciencias Experimentales, Universidad Jaume I, 12080 Castellon (Spain); Scientific Council for Cybernetics, Russian Academy of Sciences, Vavilov str. 34, 333117 Moscow (Russian Federation); Aguilella, V.M.; Aguilella-Arzo, M. [Departamento de Ciencias Experimentales, Universidad Jaume I, 12080 Castellon (Spain); Belaya, M. [Institute of Plant Physiology, Russian Academy of Sciences, Botanicheskaya 35, 127276 Moscow (Russian Federation)

2004-10-01

66

Interaction of a polar molecule with an ion channel  

NASA Astrophysics Data System (ADS)

The binding of a polar macromolecule to a large ion channel is studied theoretically, paying special attention to the influence of external conditions (applied voltage and ion strength of solution). The molecule behavior in bound state is considered as random thermal fluctuations within a limited fraction of its phase space. The mean duration of molecule binding (residence time ?r ) is represented as the mean first passage time to reach the boundary of that restricted domain. By invoking the adiabatic approximation we reduce the problem to one dimension with the angle between macromolecule dipole and channel axes being the key variable of the problem. The model accounts for experimental measurements of ?r for the antibiotic Ampicillin within the bacterial porin OmpF of Escherichia coli. By assuming that the electrical interaction between Ampicillin dipole and OmpF ionizable groups affects the fluctuations, we find that the biased residence time-voltage dependence observed in experiments is the result of the strong transversal electric field in OmpF constriction with a tilt ˜30° aside the cis side.

Levadny, V.; Aguilella, V. M.; Aguilella-Arzo, M.; Belaya, M.

2004-10-01

67

Apparatus for Nuclear High Polarization Measurement in Polarized Target.  

National Technical Information Service (NTIS)

An apparatus for the measurement of high nuclear polarization in polarized targets is described. The usage of a rigid automatic tuning of the resonance circuit frequency (AFC) and automatic control of the radio frequency (RF) voltage phase of the AFC circ...

Y. F. Kiselev V. N. Matafonov

1976-01-01

68

Giant polarization in high polymers  

NASA Astrophysics Data System (ADS)

In the course of studying the properties of highly conjugated polymers we found that long range orbital delocalization conferred unexpected properties. The presence of giant electronic orbitals made these materials electroactive yet very stable. A new mode of electronic polarizability resulted, a giant nomadic polarization, making these organic polymers among the most polarizable materials ever encountered. In addition, yet other attributes could be found, such as remanent magnetization, or metallic conductivity, or unusual pressure sensitivity. The giant orbital concept opens up new vistas of materials properties. We note that one can tailor giant orbital polymers to produce pure and highly stable super-dielectrics with high dielectric constants, from 6 to 100,000. Such materials will be useful in the electric power control, as in large motor starting capacitors and in power factor correction. They will doubtless also be useful in low visibility coatings, in obscuration, in EMP shielding, in microcircuitry, in transducers, and in parametric circuits. It remains to be proven if this new molecular mode, nomadic polarization, proves superior in energy storage and loss to that of the conventional “dipole orientation” mode. Preliminary results indicate an advantage for the new giant orbital materials.

Pohl, Herbert A.

1986-07-01

69

Micro-optical polarizer with high efficiency.  

PubMed

Based on liquid crystal polymers (LCP) a compact micro-optical polarizer with high efficiency has been designed and realized. By using cylindrical microlens arrays made of LCP and index matching layer, a complete separation of both polarization components of the unpolarized input light is achieved. Combined with a patterned twisted nematic (TN) cell, allowing a rotation of only one polarization component, a polarizer with high efficiency (72,5% (measured) is realized. Simulations and measurements are presented. PMID:18542282

Ruffieux, Patrick; Scharf, Toralf; Herzig, Hans-Peter

2008-02-01

70

Simulation studies on mixtures of polarizable dipolar and polarizable non-polar linear molecules  

Microsoft Academic Search

In a previous paper liquid-liquid phase separation had been determined for mixtures of dipolar and non-polar two-centre Lennard-Jones molecules of elongation L = 0.505. Here we present isobaric-isothermal molecular dynamics simulation results for mixtures of dipolar with non-polar molecules where either the non-polar component (I) or both components (II) were made polarizable. The proper treatment of many-body inductive interaction effects,

Christian Kriebel; Jochen Winkelmann

1998-01-01

71

Toward scalable information processing with ultracold polar molecules in an electric field: A numerical investigation  

SciTech Connect

We numerically investigate the possibilities of driving quantum algorithms with laser pulses in a register of ultracold NaCs polar molecules in a static electric field. We focus on the possibilities of performing scalable logical operations by considering circuits that involve intermolecular gates (implemented on adjacent interacting molecules) to enable the transfer of information from one molecule to another during conditional laser-driven population inversions. We study the implementation of an arithmetic operation (the addition of 0 or 1 on a binary digit and a carry in) which requires population inversions only and the Deutsch-Jozsa algorithm which requires a control of the phases. Under typical experimental conditions, our simulations show that high-fidelity logical operations involving several qubits can be performed in a time scale of a few hundreds of microseconds, opening promising perspectives for the manipulation of a large number of qubits in these systems.

Bomble, Laeetitia; Pellegrini, Philippe; Ghesquiere, Pierre [Laboratoire de Chimie Physique, Universite Paris-Sud, UMR 8000, Orsay F-91405 (France); Desouter-Lecomte, Michele [Laboratoire de Chimie Physique, Universite Paris-Sud, UMR 8000, Orsay F-91405 (France); Departement de Chimie, Universite de Liege, Bat B6c Sart Tilman, B-4000 Liege Belgium (Belgium)

2010-12-15

72

Implementing quantum algorithms in hyperfine levels of ultracold polar molecules by optimal control.  

PubMed

We numerically implement quantum algorithms in hyperfine levels of ultracold polar molecules. Logical operations are driven by pulses optimized by optimal control theory. All implementations take place in the lowest two rotational levels of the ground vibrational state of the ground (1)?(+) electronic state, exploiting the richness of the hyperfine energy structure and state mixing in static external fields. We show that it is possible to realize high fidelity complex logical operations with microsecond pulses. The possibility to run algorithms implemented on two interacting molecules is also demonstrated. (41)K(85)Rb and (41)K(87)Rb molecules are considered for the numerical simulations but the results are general and can be extended to other species. PMID:21766136

Pellegrini, Philippe; Vranckx, Stéphane; Desouter-Lecomte, Michèle

2011-07-18

73

Guiding slow polar molecules with a charged wire  

SciTech Connect

We demonstrate experimentally the guiding of cold and slow ND{sub 3} molecules along a thin charged wire over a distance of {approx}0.34 m through an entire molecular beam apparatus. Trajectory simulations confirm that both linear and quadratic high-field-seeking Stark states can be efficiently guided from the beam source up to the detector. A density enhancement up to a factor 7 is reached for beams with velocities ranging down to {approx}150 m/s generated by the rotating nozzle technique.

Strebel, M.; Spieler, S.; Stienkemeier, F.; Mudrich, M. [Physikalisches Institut, Universitaet Freiburg, D-79104 Freiburg (Germany)

2011-11-15

74

Electrostatic versus polarization effects in the adsorption of aromatic molecules of varied polarity on an insulating hydrophobic surface  

NASA Astrophysics Data System (ADS)

Ab initio calculations have been used to investigate the electronic and energetic behaviour accompanying the adsorption of aromatic molecules of different polarities onto an insulating hydrophobic surface, as a convenient model for the study of characteristic weak adsorption processes in biochemistry (ligand-receptor interactions) and geochemistry (aromatic pollutants on soil minerals). Four poly-chlorinated dibenzo-p-dioxin molecules of different polarities were chosen as adsorbates; the surface was the (001) surface of pyrophyllite, a chemically inert, weakly polar, covalently bonded surface. The fairly weak interactions were observed to be dominated by local electrostatics rather than global multipoles or hybridization. The polarization induced on the adsorbate has been analysed. A small transfer of electron density was also observed from the molecule to the surface.

Austen, Kat F.; White, Toby O. H.; Marmier, Arnaud; Parker, Steve C.; Artacho, Emilio; Dove, Martin T.

2008-01-01

75

Growth-induced polarity formation in two-component crystals of organic molecules: A statistical analysis  

Microsoft Academic Search

On the basis of a layer-by-layer growth model, growth-induced polarity formation is investigated in two-component crystals (solid solutions) of polar H (host) and non-polar G (guest) or polar H and G molecules, with native H and G crystals being assumed centrosymmetric. These two types of chemical systems are compared with one another in terms of a statistical analysis being comprised

Thomas Wüst; Jürg Hulliger

2006-01-01

76

The Volume Dependence of Cohesive Energy for Nonpolar to Polar Molecules from Molecular Dynamics  

NASA Astrophysics Data System (ADS)

The dependence of the cohesive energy of a fluid on volume, E(V), is critically important in Scatchard-Hildebrand solubility parameter (?) theory, and otherwise modulates the heat of mixing of substances having differing E(V) behavior. Using MD simulations and a high accuracy force field (COMPASS), we have investigated E(V) for a range of small molecules - from those having very low solubility parameters (perfluorobutane) to very large values (ethylene glycol). We find power law behavior, E(V) = CV^-?, over fairly wide ranges of density, but with deviations that result from repulsive interactions at high densities. Electrostatics are shown to play an important role in compressing polar fluids into the repulsive region, thereby reducing the value of the exponent ?. In general, ? decreases with increasing polarity (increasing ?). The simulations are shown to be as reliable as the experimentally measured values.

Eichinger, B. E.

2001-03-01

77

Microgels for the encapsulation and stimulus-responsive release of molecules with distinct polarities.  

PubMed

A microfluidic strategy for the encapsulation and stimulus-responsive release of molecules with distinct polarities from the interior of microgels is reported. The approach relies on (i) the generation of a primary O/W emulsion by the ultrasonication method, (ii) MF emulsification of the primary emulsion, and (iii) photopolymerization of the monomer present in the aqueous phase of the droplets, thereby transforming them into microgels. Non-polar molecules are dissolved in oil droplets embedded in the microgels. Polar molecules are physically associated with the hydrogel network. Upon heating, the microgels contract and release polar and non-polar cargo molecules. The approach paves the way for stimuli-responsive vehicles for multiple drug delivery. PMID:21504069

Jagadeesan, Dinesh; Nasimova, Irina; Gourevich, Ilya; Starodubtsev, Sergey; Kumacheva, Eugenia

2011-04-19

78

Detection of bio-molecules of different polarities by Boron Nitride Nanotoube  

NASA Astrophysics Data System (ADS)

The effect of molecular polarity on the interaction between a boron nitride nanotube (BNNT) and amino acids is investigated with density functional theory. Three representative amino acids, namely, tryptophane (Trp), a nonpolar aromatic amino acid, and asparatic acid (Asp) and argenine (Arg), both polar amino acids are considered for their interactions with BNNT. The polar molecules, Asp and Arg, exhibit relatively stronger binding with the tubular surface of BNNT. The binding between the polar amino acid molecules and BNNT is accompanied by a charge transfer, suggesting that stabilization of the bioconjugated complex is mainly governed by electrostatic interactions. The results show modulation of the BNNT band gap by Trp. Interestingly, no change in band gap of BNNT is seen for the polar molecules Asp and Arg. The predicted higher sensitivity of BNNTs compared to carbon nanotubes (CNTs) toward amino acid polarity suggests BNNTs to be a better substrate for protein immobilization than CNTs.

Mukhopadhyay, Saikat; Scheicher, Ralph; Pandey, Ravindra; Karna, Shashi

2012-02-01

79

Topological p{sub x}+ip{sub y} superfluid phase of fermionic polar molecules  

SciTech Connect

We discuss the topological p{sub x}+ip{sub y} superfluid phase in a two-dimensional (2D) gas of single-component fermionic polar molecules dressed by a circularly polarized microwave field. This phase emerges because the molecules may interact with each other via a potential V{sub 0}(r) that has an attractive dipole-dipole 1/r{sup 3} tail, which provides p-wave superfluid pairing at fairly high temperatures. We calculate the amplitude of elastic p-wave scattering in the potential V{sub 0}(r) taking into account both the anomalous scattering due to the dipole-dipole tail and the short-range contribution. This amplitude is then used for the analytical and numerical solution of the renormalized BCS gap equation which includes the second-order Gor'kov-Melik-Barkhudarov corrections and the correction related to the effective mass of the quasiparticles. We find that the critical temperature T{sub c} can be varied within a few orders of magnitude by modifying the short-range part of the potential V{sub 0}(r). The decay of the system via collisional relaxation of molecules to dressed states with lower energies is rather slow due to the necessity of a large momentum transfer. The presence of a constant transverse electric field reduces the inelastic rate, and the lifetime of the system can be of the order of seconds even at 2D densities {approx}10{sup 9} cm{sup -2}. This leads to T{sub c} of up to a few tens of nanokelvins and makes it realistic to obtain the topological p{sub x}+ip{sub y} phase in experiments with ultracold polar molecules.

Levinsen, J.; Cooper, N. R. [T.C.M. Group, University of Cambridge, Cavendish Laboratory, J.J. Thomson Ave., Cambridge CB3 0HE (United Kingdom); Laboratoire de Physique Theorique et Modeles Statistiques, CNRS and Universite Paris Sud, UMR8626, 91405 Orsay (France); Shlyapnikov, G. V. [Laboratoire de Physique Theorique et Modeles Statistiques, CNRS and Universite Paris Sud, UMR8626, 91405 Orsay (France); Van der Waals-Zeeman Institute, University of Amsterdam, Science Park 904, 1098 XH Amsterdam (Netherlands); Kavli Institute for Theoretical Physics, University of California, Santa Barbara, California 93106-4030 (United States)

2011-07-15

80

ACCELERATING POLARIZED PROTONS TO HIGH ENERGY.  

SciTech Connect

The Relativistic Heavy Ion Collider (RHIC) is designed to provide collisions of high energy polarized protons for the quest of understanding the proton spin structure. Polarized proton collisions at a beam energy of 100 GeV have been achieved in RHIC since 2001. Recently, polarized proton beam was accelerated to 250 GeV in RHIC for the first time. Unlike accelerating unpolarized protons, the challenge for achieving high energy polarized protons is to fight the various mechanisms in an accelerator that can lead to partial or total polarization loss due to the interaction of the spin vector with the magnetic fields. We report on the progress of the RHIC polarized proton program. We also present the strategies of how to preserve the polarization through the entire acceleration chain, i.e. a 200 MeV linear accelerator, the Booster, the AGS and RHIC.

BAI, M.; AHRENS, L.; ALEKSEEV, I.G.; ALESSI, J.; BEEBE-WANG, J.; BLASKIEWICZ, M.; BRAVAR, A.; BRENNAN, J.M.; BRUNO, D.; BUNCE, G.; ET AL.

2006-10-02

81

Implementation of quantum logic gates using polar molecules in pendular states.  

PubMed

We present a systematic approach to implementation of basic quantum logic gates operating on polar molecules in pendular states as qubits for a quantum computer. A static electric field prevents quenching of the dipole moments by rotation, thereby creating the pendular states; also, the field gradient enables distinguishing among qubit sites. Multi-target optimal control theory is used as a means of optimizing the initial-to-target transition probability via a laser field. We give detailed calculations for the SrO molecule, a favorite candidate for proposed quantum computers. Our simulation results indicate that NOT, Hadamard and CNOT gates can be realized with high fidelity, as high as 0.985, for such pendular qubit states. PMID:23320665

Zhu, Jing; Kais, Sabre; Wei, Qi; Herschbach, Dudley; Friedrich, Bretislav

2013-01-14

82

Spin-Polarized Electron Induced Asymmetric Reactions in Chiral Molecules  

NASA Astrophysics Data System (ADS)

Understanding the origin of chirality in nature has been an active area of research since the time of Pasteur. In this chapter we examine one possible route by which this asymmetry could have arisen, namely chiral-specific chemistry induced by spin-polarized electrons. The various sources of spin-polarized electrons (parity violation, photoemission, and secondary processes) are discussed. Experiments aimed at exploring these interactions are reviewed starting with those based on the Vester-Ulbricht hypothesis through recent studies of spin polarized secondary electrons from a magnetic substrate. We will conclude with a discussion of possible new avenues of research that could impact this area.

Rosenberg, Richard A.

83

Vector correlations in photodissociation of polarized polyatomic molecules beyond the axial recoil limit.  

PubMed

We present the full quantum mechanical theory of the angular momentum distributions of photofragments produced in photolysis of oriented/aligned parent polyatomic molecules beyond the axial recoil limit. This paper generalizes the results of Underwood and Powis(28,29) to the case of non-axial recoil photodissociation of an arbitrary polyatomic molecule. The spherical tensor approach is used throughout this paper. We show that the recoil angular distribution of the angular momentum polarization of each of the photofragments can be presented in a universal spherical tensor form valid for photolysis in diatomic or polyatomic molecules, irrespective of the reaction mechanism. The angular distribution can be written as an expansion over the Wigner D-functions in terms of the set of the anisotropy-transforming coefficients c(K(i)q(i))(K) (k(d), K(0)) which contain all of the information about the photodissociation dynamics and can be either determined from experiment, or computed from quantum mechanical theory. An important new conservation rule is revealed through the analysis, namely that the component q(i) of the initial reagent polarization rank K(i) and the photofragment polarization rank K onto the photofragment recoil direction k is preserved in any photolysis reaction. Both laboratory and body frame expressions for the recoil angle dependence of the photofragment angular momentum polarization are presented. The parent molecule polarization is shown to lead to new terms in the obtained photofragment angular distributions compared with the isotropic case. In particular, the terms with |q(i)| > 2 can appear which are shown to manifest angular momentum helicity non-conservation in the reaction. The expressions for the coefficients c(K(i)q(i))(K) (k(d), K(0)) have been simplified using the quasiclassical approximation in the high-J limit which allows for introducing the dynamical functions and the rotation factors which describe the decreasing of the photofragment angular momentum orientation and alignment due to the rotation of the molecular axis during photodissociation. In this case, the resultant recoil angle dependence is also presented in a form where the anisotropy of the parent molecular ensemble is expressed in terms of the molecular axis distribution, rather than in terms of the molecular density matrix. PMID:21152623

Krasilnikov, Mikhail B; Kuznetsov, Vladislav V; Suits, Arthur G; Vasyutinskii, Oleg S

2010-12-13

84

Dynamical crystal creation with polar molecules or Rydberg atoms in optical lattices  

NASA Astrophysics Data System (ADS)

We investigate the dynamical formation of crystalline states with systems of polar molecules or Rydberg atoms loaded into a deep optical lattice. External fields in these systems can be used to couple the atoms or molecules between two internal states: one that is weakly interacting and one that exhibits a strong dipole-dipole interaction. By appropriate time variation of the external fields, we show that it is possible to produce crystalline states of the strongly interacting states with high filling fractions chosen via the parameters of the coupling. We study the coherent dynamics of this process in one dimension (1D) using a modified form of the time-evolving block decimation (TEBD) algorithm, and obtain crystalline states for system sizes and parameters corresponding to realistic experimental configurations. For polar molecules these crystalline states will be long-lived, assisting in a characterization of the state via the measurement of correlation functions. We also show that as the coupling strength increases in the model, the crystalline order is broken. This is characterized in 1D by a change in density-density correlation functions, which decay to a constant in the crystalline regime, but show different regions of exponential and algebraic decay for larger coupling strengths.

Schachenmayer, J.; Lesanovsky, I.; Micheli, A.; Daley, A. J.

2010-10-01

85

High efficiency reflective liquid crystal polarization gratings  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate a reflective-mode liquid crystal polarization grating with high reflectance, small grating period, and subms switching times. This switchable optical element can diffract ~100% into a single order, have highly polarization-sensitive first orders, and have a polarization-insensitive zero order. Here we introduce an absorbing layer that overcomes the reflection of the (ultraviolet) holographic beams, which otherwise prevents high quality fabrication. At a grating period of 2.1 ?m, we report 98% diffraction efficiency, 90% reflectance, ~600:1 contrast-ratio, and ~3000:1 polarization contrast. These elements can therefore be configured as polarization-independent modulators or switchable polarizing beam splitters, for use in telecommunications, displays, spatial-light modulators, and polarimetry.

Komanduri, R. K.; Escuti, M. J.

2009-08-01

86

Beam dynamics in a storage ring for neutral (polar) molecules  

SciTech Connect

The force from a non-uniform electric field on the electric dipole moment of a molecule may be used to circulate and focus molecules in a storage ring. The nature of the forces from multipole electrodes for bending and focusing are described for strong-field-seeking and for weak-field-seeking molecules. Fringe-field forces are analyzed. Examples of storage ring designs are presented; these include long straight sections and provide bunching and acceleration.

Lambertson, Glen R.

2003-05-01

87

Quantum magnetism with multicomponent polar molecules in an optical lattice  

Microsoft Academic Search

We consider dipolar molecules in an optical lattice prepared as a mixture of states with angular momentum l=0 and l=1. The 1\\/r^3 interaction between molecules for this system is produced by exchanging a quantum of angular momentum between two molecules. We show that Mott states of such systems have a large variety of non-trivial spin orderings including SDW state at

Ryan Barnett; Dmitry Petrov; Mikhail Lukin; Eugene Demler

2006-01-01

88

Universalities in ultracold reactions of alkali-metal polar molecules  

SciTech Connect

We consider ultracold collisions of ground-state heteronuclear alkali-metal dimers that are susceptible to four-center chemical reactions 2AB{yields}A{sub 2}+B{sub 2} even at submicrokelvin temperatures. These reactions depend strongly on species, temperature, electric field, and confinement in an optical lattice. We calculate ab initio van der Waals coefficients for these interactions and use a quantum formalism to study the scattering properties of such molecules under an external electric field and optical lattice. We also apply a quantum threshold model to explore the dependence of reaction rates on the various parameters. We find that, among the heteronuclear alkali-metal fermionic species, LiNa is the least reactive, whereas LiCs is the most reactive. For the bosonic species, LiK is the most reactive in zero field, but all species considered, LiNa, LiK, LiRb, LiCs, and KRb, share a universal reaction rate once a sufficiently high electric field is applied. For indistinguishable bosons, the inelastic/reactive rate increases as d{sup 2} in the quantum regime, where d is the dipole moment induced by the electric field. This is a weaker power-law dependence than for indistinguishable fermions, for which the rate behaves as d{sup 6}.

Quemener, Goulven; Bohn, John L.; Petrov, Alexander; Kotochigova, Svetlana [JILA, University of Colorado, Boulder, Colorado 80309 (United States); Temple University, Philadelphia, Pennsylvania 19122 (United States)

2011-12-15

89

Polarization Properties of AGN at High Frequencies  

NASA Astrophysics Data System (ADS)

I discuss variability of polarization in the core region of parsec scale radio jets and connections between 7 mm polarization in the VLBI core and polarization at shorter wavelengths from the whole source for a sample of AGN with highly relativistic jets known as blazars. The sources show pronounced diversity in polarization behavior that is not clearly understood. I discuss possible reasons for these differences as well as the role that VSOP-2 can play in exploring the magnetic field in the most compact regions of jets.

Jorstad, S. G.

2009-08-01

90

Observation of dipolar spin-exchange interactions with lattice-confined polar molecules.  

PubMed

With the production of polar molecules in the quantum regime, long-range dipolar interactions are expected to facilitate understanding of strongly interacting many-body quantum systems and to realize lattice spin models for exploring quantum magnetism. In ordinary atomic systems, where contact interactions require wavefunction overlap, effective spin interactions on a lattice can be mediated by tunnelling, through a process referred to as superexchange; however, the coupling is relatively weak and is limited to nearest-neighbour interactions. In contrast, dipolar interactions exist even in the absence of tunnelling and extend beyond nearest neighbours. This allows coherent spin dynamics to persist even for gases with relatively high entropy and low lattice filling. Measured effects of dipolar interactions in ultracold molecular gases have been limited to the modification of inelastic collisions and chemical reactions. Here we use dipolar interactions of polar molecules pinned in a three-dimensional optical lattice to realize a lattice spin model. Spin is encoded in rotational states of molecules that are prepared and probed by microwaves. Resonant exchange of rotational angular momentum between two molecules realizes a spin-exchange interaction. The dipolar interactions are apparent in the evolution of the spin coherence, which shows oscillations in addition to an overall decay of the coherence. The frequency of these oscillations, the strong dependence of the spin coherence time on the lattice filling factor and the effect of a multipulse sequence designed to reverse dynamics due to two-body exchange interactions all provide evidence of dipolar interactions. Furthermore, we demonstrate the suppression of loss in weak lattices due to a continuous quantum Zeno mechanism. Measurements of these tunnelling-induced losses allow us to determine the lattice filling factor independently. Our work constitutes an initial exploration of the behaviour of many-body spin models with direct, long-range spin interactions and lays the groundwork for future studies of many-body dynamics in spin lattices. PMID:24048478

Yan, Bo; Moses, Steven A; Gadway, Bryce; Covey, Jacob P; Hazzard, Kaden R A; Rey, Ana Maria; Jin, Deborah S; Ye, Jun

2013-09-18

91

Giant enhancement of photodissociation of polar diatomic molecules in electric fields.  

PubMed

We explore the photodissociation of polar diatomic molecules in static electric fields in the rotationally cold regime using the example of the LiCs molecule. A giant enhancement of the differential cross section is found for laboratory electric field strengths, and analyzed with varying rovibrational bound states, continuum energies as well as field strengths. PMID:21796279

González-Férez, R; Schmelcher, P

2011-07-27

92

Formation of an ordered Langmuir monolayer by a non-polar chain molecule  

Microsoft Academic Search

Amphiphilic molecules, which contain a polar 'head' group and a hydrophobic 'tail', will generally form monolayers at the air-water interface in which the molecules protrude from the interface with the tails in the air. These 'Langmuir monolayers' exhibit a variety of phases as a function of surface pressure and temperature, including an ordered, two-dimensional crystalline phase. It might be considered

Mengyang Li; Anibal A. Acero; Zhengqing Huang; Stuart A. Rice

1994-01-01

93

Changepoint Analysis for Single-Molecule Polarized Total Internal Reflection Fluorescence Microscopy Experiments  

PubMed Central

The experimental study of individual macromolecules has opened a door to determining the details of their mechanochemical operation. Motor enzymes such as the myosin family have been particularly attractive targets for such study, in part because some of them are highly processive and their “product” is spatial motion. But single-molecule resolution comes with its own costs and limitations. Often, the observations rest on single fluorescent dye molecules, which emit a limited number of photons before photobleaching and are subject to complex internal dynamics. Thus, it is important to develop methods that extract the maximum useful information from a finite set of detected photons. We have extended an experimental technique, multiple polarization illumination in total internal reflection fluorescence microscopy (polTIRF), to record the arrival time and polarization state of each individual detected photon. We also extended an analysis technique, previously applied to FRET experiments, that optimally determines times of changes in photon emission rates. Combining these improvements allows us to identify the structural dynamics of a molecular motor (myosin V) with unprecedented detail and temporal resolution.

Beausang, John F.; Goldman, Yale E.; Nelson, Philip C.

2011-01-01

94

Simple quantum model of ultracold polar molecule collisions  

SciTech Connect

We present a unified formalism for describing chemical reaction rates of trapped, ultracold molecules. This formalism reduces the scattering to its essential features, namely, a propagation of the reactant molecules through a gauntlet of long-range forces before they ultimately encounter one another, followed by a probability for the reaction to occur once they do. In this way, the electric-field dependence should be readily parametrized in terms of a pair of fitting parameters (along with a C{sub 6} coefficient) for each asymptotic value of partial-wave quantum numbers |L,M{sub L}>. From this, the electric-field dependence of the collision rates follows automatically. We present examples for reactive species, such as KRb, and nonreactive species, such as RbCs.

Idziaszek, Zbigniew; Quemener, Goulven; Bohn, John L.; Julienne, Paul S. [Faculty of Physics, University of Warsaw, PL-00-681 Warsaw (Poland); JILA, NIST, and University of Colorado, Boulder, Colorado, 80309-0440 (United States); Joint Quantum Institute, NIST, and the University of Maryland, Gaithersburg, Maryland 20899-8423 (United States)

2010-08-15

95

Automated transfer and injection of hyperpolarized molecules with polarization measurement prior to in vivo NMR.  

PubMed

Hyperpolarized magnetic resonance via dissolution dynamic nuclear polarization necessitates the transfer of the hyperpolarized molecules from the polarizer to the imager prior to in vivo measurements. This process leads to unavoidable losses in nuclear polarization, which are difficult to evaluate once the solution has been injected into an animal. We propose a method to measure the polarization of the hyperpolarized molecules inside the imager bore, 3?s following dissolution, at the time of the injection, using a precise quantification of the infusate concentration. This in situ quantification allows for distinguishing between signal modulations related to variations in the nuclear polarization at the time of the injection and signal modulations related to physiological processes such as tissue perfusion. In addition, our method includes a radical scavenging process that leads to a minor reduction in sample concentration and takes place within a couple of seconds following the dissolution in order to minimize the losses due to the presence of paramagnetic polarizing agent in the infusate. We showed that proton exchange between vitamin C, the scavenging molecule and the deuterated solvent shortens the long carboxyl (13) C longitudinal relaxation time in [1-(13) C]acetate. This additional source of dipolar relaxation can be avoided by using deuterated ascorbate. Overall, the method allows for a substantial gain in polarization and also leads to an extension of the time window available for in vivo measurements. Copyright © 2013 John Wiley & Sons, Ltd. PMID:23893539

Cheng, Tian; Mishkovsky, Mor; Bastiaansen, Jessica A M; Ouari, Olivier; Hautle, Patrick; Tordo, Paul; van den Brandt, Ben; Comment, Arnaud

2013-07-25

96

Universal ultracold collision rates for polar molecules of two alkali-metal atoms  

NASA Astrophysics Data System (ADS)

Highly reactive ultracold polar molecules have universal near-threshold reaction rate constants that depend only on the long-range interaction potential, as shown for the KRb molecule [1-3]. We extend these calculations to estimate universal reaction rate constants for the bosonic and fermionic isotopes of the reactive species LiNa, LiK, LiRb, LiCs, and also the universal vibrational quenching rate constants for vibrationally excited states of the non-reactive species NaK, NaRb, NaCs, KCs, and RbCs. We also examine the variation with electric field of the universal collision rates for these species in quasi-2D geometry in a one-dimensional optical lattice. For many of these species an electric field of a few kV/cm perpendicular to the lattice plane should be effective in shielding the molecules from destructive collisions even at relatively modest lattice confinement strength. [4pt] [1] Z. Idziaszek and P. S. Julienne, Phys. Rev. Lett. 104, 113202 (2010). [0pt] [2] A. Micheli, et al., Phys. Rev. Lett. 105, 073202 (2010). [0pt] [3] S. Ospelkaus, et al., Science 327, 853 (2010).

Julienne, Paul; Hanna, Thomas; Idziaszek, Zbigniew

2011-06-01

97

Bilayer superfluidity of fermionic polar molecules: Many-body effects  

SciTech Connect

We study the BCS superfluid transition in a single-component fermionic gas of dipolar particles loaded in a tight bilayer trap, with the electric dipole moments polarized perpendicular to the layers. Based on the detailed analysis of the interlayer scattering, we calculate the critical temperature of the interlayer superfluid pairing transition when the layer separation is both smaller (dilute regime) and on the order or larger (dense regime) than the mean interparticle separation in each layer. Our calculations go beyond the standard BCS approach and include the many-body contributions resulting in the mass renormalization, as well as additional contributions to the pairing interaction. We find that the many-body effects have a pronounced effect on the critical temperature and can either decrease (in the very dilute limit) or increase (in the dense and moderately dilute limits) the transition temperature as compared to the BCS approach.

Baranov, M. A. [Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria); Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck (Austria); RRC 'Kurchatov Institute', Kurchatov Square 1, 123182 Moscow (Russian Federation); Micheli, A.; Ronen, S.; Zoller, P. [Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria); Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences, A-6020 Innsbruck (Austria)

2011-04-15

98

Supersolid Phase with Cold Polar Molecules on a Triangular Lattice  

SciTech Connect

We study a system of heteronuclear molecules on a triangular lattice and analyze the potential of this system for the experimental realization of a supersolid phase. The ground state phase diagram contains superfluid, solid, and supersolid phases. At finite temperatures and strong interactions there is an additional emulsion region, in contrast with similar models with short-range interactions. We derive the maximal critical temperature T{sub c} and the corresponding entropy S/N=0.04(1) for supersolidity and find feasible experimental conditions for its realization.

Pollet, L. [Physics Department, Harvard University, Cambridge, Massachusetts 02138 (United States); Department of Physics, University of Massachusetts, Amherst, Massachusetts 01003 (United States); Theoretische Physik, ETH Zurich, 8093 Zurich (Switzerland); Picon, J. D. [Theoretische Physik, ETH Zurich, 8093 Zurich (Switzerland); Institute of Theoretical Physics, Ecole polytechnique federale de Lausanne, CH-1015 Lausanne (Switzerland); Buechler, H. P. [Institute of Theoretical Physics III, Universitaet Stuttgart, 70550 Stuttgart (Germany); Troyer, M. [Theoretische Physik, ETH Zurich, 8093 Zurich (Switzerland)

2010-03-26

99

The Highly Polarized Open Cluster Trumpler 27  

NASA Astrophysics Data System (ADS)

We have carried out multicolor linear polarimetry (UBVRI) of the brightest stars in the area of the open cluster Trumpler 27. Our data show a high level of polarization in the stellar light with a considerable dispersion, from P=4% to P=9.5%. The polarization vectors of the cluster members appear to be aligned. Foreground polarization was estimated from the data of some nonmember objects, for which two different components were resolved: the first one associated with a dust cloud close to the Sun producing P?max=1.3% and ?=146°, and a second component, the main source of polarization for the cluster members, originating in another dust cloud, which polarizes the light in the direction of ?=29.5d. From a detailed analysis, we found that the two components have associated values EB-V<0.45 for the first one and EB-V>0.75 for the other. Due the difference in the orientation of both polarization vectors, almost 90° (180° at the Stokes representation), the first cloud (?~146°) depolarizes the light strongly polarized by the second one (?~29.5d). Based on observations obtanined at Complejo Astronómico El Leoncito (CASLEO), operated under agreement between CONICET and the National Universities of La Plata, Córdoba, and San Juan, Argentina.

Feinstein, Carlos; Baume, Gustavo; Vazquez, Ruben; Niemela, Virpi; Cerruti, Miguel Angel

2000-10-01

100

Partial-photoelectron-wave analysis in diatomic molecule photoionization by fluorescence polarization experiments  

SciTech Connect

Parameters {beta}1 and {beta}2 describing the angular distribution of circularly polarized fluorescence photons emitted by randomly oriented diatomic molecules excited by circularly polarized radiation are derived. We prove theoretically that measuring these parameters allows a partial-wave analysis of the emitted photoelectrons in the case of closed-shell diatomic molecules. The determination of the relative partial cross sections for emission of the {epsilon}{sigma}, {epsilon}{pi}, and {epsilon}{delta} photoelectrons is of fundamental importance for a sensitive test of corresponding calculations.

Demekhin, Ph. V. [Institute of Physics and CINSaT, University of Kassel, D-34132 Kassel (Germany); Rostov State University of Transport Communications, 344038 Rostov-on-Don (Russian Federation); Petrov, I. D. [Rostov State University of Transport Communications, 344038 Rostov-on-Don (Russian Federation); Ehresmann, A. [Institute of Physics and CINSaT, University of Kassel, D-34132 Kassel (Germany)

2010-10-15

101

Single molecules probe the polarization dynamics of poly (methyl methacrylate) in external electric field  

NASA Astrophysics Data System (ADS)

We demonstrate the electric field (EF) induced polarization dynamics of poly (methyl methacrylate) (PMMA) by observing the fluorescence modulation of embedded non-polar single squaraine-derived rotaxane molecules. It is established that interaction between the molecular energy level and the potential valley formed by surrounding PMMA matrix can be detuned by the EF, which induces the changing of electron transfer rates between them effectively. The EF-induced response time of the fluorescence quenching or enhancement and the fluorescence recovery time reflect the diverse polarization and relaxation dynamics of PMMA.

Chen, Ruiyun; Zhang, Guofeng; Gao, Yan; Xiao, Liantuan; Jia, Suotang

2012-05-01

102

Ionization of oriented carbonyl sulfide molecules by intense circularly polarized laser pulses  

NASA Astrophysics Data System (ADS)

We present combined experimental and theoretical results on strong-field ionization of oriented carbonyl sulfide molecules by circularly polarized laser pulses. The obtained molecular frame photoelectron angular distributions show pronounced asymmetries perpendicular to the direction of the molecular electric dipole moment. These findings are explained by a tunneling model invoking the laser-induced Stark shifts associated with the dipoles and polarizabilities of the molecule and its unrelaxed cation. The focus of the present article is to understand the strong-field ionization of one-dimensionally-oriented polar molecules, in particular asymmetries in the emission direction of the photoelectrons. In the following article [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.83.023406 83, 023406 (2011)] the focus is to understand strong-field ionization from three-dimensionally-oriented asymmetric top molecules, in particular the suppression of electron emission in nodal planes of molecular orbitals.

Dimitrovski, Darko; Abu-Samha, Mahmoud; Madsen, Lars Bojer; Filsinger, Frank; Meijer, Gerard; Küpper, Jochen; Holmegaard, Lotte; Kalhøj, Line; Nielsen, Jens H.; Stapelfeldt, Henrik

2011-02-01

103

Ionization of oriented carbonyl sulfide molecules by intense circularly polarized laser pulses  

SciTech Connect

We present combined experimental and theoretical results on strong-field ionization of oriented carbonyl sulfide molecules by circularly polarized laser pulses. The obtained molecular frame photoelectron angular distributions show pronounced asymmetries perpendicular to the direction of the molecular electric dipole moment. These findings are explained by a tunneling model invoking the laser-induced Stark shifts associated with the dipoles and polarizabilities of the molecule and its unrelaxed cation. The focus of the present article is to understand the strong-field ionization of one-dimensionally-oriented polar molecules, in particular asymmetries in the emission direction of the photoelectrons. In the following article [Phys. Rev. A 83, 023406 (2011)] the focus is to understand strong-field ionization from three-dimensionally-oriented asymmetric top molecules, in particular the suppression of electron emission in nodal planes of molecular orbitals.

Dimitrovski, Darko; Abu-samha, Mahmoud; Madsen, Lars Bojer; Filsinger, Frank; Meijer, Gerard; Kuepper, Jochen [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark); Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); Holmegaard, Lotte; Kalhoej, Line [Department of Chemistry, Aarhus University, DK-8000 Aarhus C (Denmark); Nielsen, Jens H. [Department of Physics, Aarhus University, DK-8000 Aarhus C (Denmark); Stapelfeldt, Henrik [Department of Chemistry, Aarhus University, DK-8000 Aarhus C (Denmark); Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark)

2011-02-15

104

Dielectric relaxation phenomena of rigid polar liquid molecules under giga hertz electric field  

Microsoft Academic Search

The dielectric relaxation phenomena of rigid polar liquid molecules chloral and ethyltrichloroacetate (j) in benzene, n-hexane and n-heptane (i) under 4.2, 9.8 and 24.6 GHz electric fields at 30°C are studied to show the possible existence of double relaxation times\\u000a ?\\u000a 2 and ?\\u000a 1 for rotations of the whole and the flexible parts of molecules. The probability of showing

K. Dutta; SK Sit; S. Acharyya

2001-01-01

105

Student construction of small molecule models using Spartan Model to explore polarity  

NASA Astrophysics Data System (ADS)

This study compared the attitudes and the gains of knowledge concerning Lewis structures and polarity of molecules. The students performed a lab exercise in which they drew Lewis structures, constructed models of the molecules, determined the geometry of the molecules, and determined the polarity of the molecules. The control group students constructed models using physical ball-and-stick models. The treatment group students used Spartan Model to construct models. Students from a university and a community college participated in this study. Four lab classes at each school made up the treatment group. Five lab classes at the university and three lab classes at the community college made up the control group. The treatment group classes were selected based on available computer resources. All students in the study were given the Lab Pre Test, Lab Post Test, and the Lecture Post Test to assess the student's ability to answer questions pertaining to Lewis structures and polarity of molecules. An Attitudinal Survey assessed the attitudes of the students who participated in the study. Student interviews were performed to assess the student's attitudes towards the lab exercise. The interviews investigated attitudes about the modeling exercise, Lewis structures, and polarity of molecules. There were no significant differences in the performance of the treatment group when compared to the control group on the performance assessment instruments at the university or the community college. The treatment group students at the university had a more positive attitude about the lab activity. They believed that the lab activity helped them better understand the concepts of Lewis structure and molecular polarity. At the community college, the control group students had a more positive attitude about the lab activity. The students involved in the study believed that the lab activity helped them to understand the concepts of molecular geometry and polarity. The interviews of the treatment group students indicated that they strongly believed that the lab activity helped them better understand the concept of Lewis structures and of molecular polarity. As reflected in the interviews of the treatment group and the control group, the lab activity did not help the students be able to look at a Lewis structure and build a mental image of the molecule. The students believed the electrostatic potential plots generated by Spartan Model were very insightful into the concept of polarity. It gave them a visual representation of a difficult topic.

Dale, Glenn Lamar

106

Performance of the SLC polarized electron source with high polarization  

SciTech Connect

For the 1992 operating cycle of the SLAC Linear Collider (SLC), the polarized electron source (PES) during its maiden run successfully met the pulse intensity and overall efficiency requirements of the SLC. However, the polarization of the bulk GaAs cathode was low ({approximately}27%) and the pulse-to-pulse stability was marginal. We have shown that adequate charge for the SLC can be extracted from a strained layer cathode having P{sub e}{approximately}80% even though the quantum efficiency (QE) is < 1%. The recent addition of a separate chamber to the PES-which allows cathodes to be loaded into the gun after the vacuum bake and after high voltage (HV) processing without breaking vacuum-increases the reliability for achieving an adequate photoelectron yield. A new SLAC-built pulsed Ti:sapphire laser permits operation of the PES at the required wavelength with sufficient power to fully saturate the yield, and thus improve the e{sup {minus}} beam stability. The performance of the PES during the 1993 SLC operating cycle with these and other improvements is discussed.

Clendenin, J.E.; Alley, R.K.; Aoyagi, H. [and others

1993-04-01

107

HIGH LUMINOSITY POLARIZED PROTON COLLISIONS AT RHIC.  

SciTech Connect

The Brookhaven Relativistic Heavy Ion Collider (RHIC) provides the unique opportunity to collide polarized proton beams at a center-of-mass energy of up to 500 GeV and luminosities of up to 2 x 10{sup 32} cm{sup {minus}2} s{sup {minus}1}. Such high luminosity and high energy polarized proton collisions will open up the possibility of studying spin effects in hard processes. However, the acceleration of polarized beams in circular accelerators is complicated by the numerous depolarizing spin resonances. Using a partial Siberian snake and a rf dipole that ensure stable adiabatic spin motion during acceleration has made it possible to accelerate polarized protons to 25 GeV at the Brookhaven AGS. After successful operation of RHIC with gold beams polarized protons from the AGS have been successfully injected into RHIC and accelerated using a full Siberian snakes built from four superconducting helical dipoles. A new high energy proton polarimeter was also successfully commissioned. Operation with two snakes per RHIC ring is planned for next year.

ROSER,T.

2001-03-26

108

Photoelectron spectroscopic studies of polyatomic molecules: Spin-polarized electrons from Td point symmetry group molecules  

Microsoft Academic Search

This paper presents a study of angle- and spin-resolved photoelectron spectroscopy in a randomly oriented nonlinear molecule in the nonrelativistic, electric dipole approximation. The theory formulated in the preceding paper has been used along with the methods of the extended point (or spin-double) group to develop, perhaps in their simplest possible forms, the expressions for the five parameters needed to

N. Chandra

1989-01-01

109

Photoelectron spectroscopic studies of polyatomic molecules: Spin-polarized electrons from oriented Td molecules  

Microsoft Academic Search

This paper presents a theoretical study of angular distribution of spin-resolved electrons ejected by interaction of light in the nonrelativistic, electric dipole approximation with nonlinear molecules oriented in space. A theory, formulated in an earlier paper [N. Chandra, Phys. Rev. A 40, 752 (1989)] by taking full account of the group-theoretical transformation properties of a molecular target, is used to

N. Chandra

1991-01-01

110

Condensate wave function and elementary excitations of bosonic polar molecules: Beyond the first Born approximation  

Microsoft Academic Search

We investigate the condensate wave function and elementary excitations of strongly interacting bosonic polar molecules in a harmonic trap, treating the scattering amplitude beyond the standard first Born approximation (FBA). By using an appropriate trial wave function in the variational method, effects of the leading-order correction beyond the FBA have been investigated and shown to be significantly enhanced when the

C.-C. Huang; W.-C. Wu; D.-W. Wang

2010-01-01

111

Interaction-induced ferroelectricity in the rotational states of polar molecules  

Microsoft Academic Search

We show that a ferroelectric quantum phase transition can be driven by the dipolar interaction of polar molecules in the presence a microwave field. The obtained ferroelectricity crucially depends on the harmonic confinement potential, and the macroscopic dipole moment persists even when the external field is turned off adiabatically. The transition is shown to be second order for fermions and

C.-H. Lin; Y.-T. Hsu; Lee Hao; D.-W. Wang

2010-01-01

112

Polar Structures in the Theory of Conjugated Molecules. I. Identification of the Ethylene pi Electron States  

Microsoft Academic Search

This and two of three parts to be published subsequently are concerned mainly with the so-called valence-bond theory of conjugated and aromatic molecules. An improvement to the method is described, which consists in adding to the usual set of structures some extra ones which are 'polar' in the sense that they show two of the pi -electrons on one centre,

D. P. Craig

1950-01-01

113

Sustainable orientation of polar molecules induced by half-cycle pulses  

SciTech Connect

Subjecting polar linear molecules to appropriately designed half-cycle electromagnetic pulses induces strong orientation of the molecules. This is deduced by inspecting the quantum dynamics within a simplified model which yields analytical conditions for the parameters of the pulses that lead to strong molecular orientation sustainable for hundreds of picoseconds. These analytical predictions are largely confirmed by a full numerical time-dependent study of the orientation process for NaI molecules. Further strategies for increasing and maintaining the molecular orientation are proposed and numerically illustrated. Our finite-temperature calculations demonstrate that the molecular orientation persists at considerable temperatures.

Matos-Abiague, A.; Berakdar, J. [Max-Planck Institut fuer Mikrostrukturphysik, Weinberg 2, 06120 Halle (Germany)

2003-12-01

114

Strong-field ionization of polar molecules: Stark-shift-corrected strong-field approximation  

NASA Astrophysics Data System (ADS)

We extend the molecular strong-field approximation for ionization, in the tunneling limit, to include systematically the linear and quadratic static Stark shifts of the ionizing molecular orbital. This approach, simple to implement, is capable of describing the essential physics of the process of strong-field ionization of oriented polar molecules by circularly polarized laser pulses. The modification of the molecular orbitals in strong fields is also discussed and in cases of extreme polarization of inner electrons a simple model is devised. We find very good agreement between the results from our model and those obtained in the recent experiment on ionizaton of oriented carbonyl sulphide and benzonitrile molecules [L. Holmegaard , Nature Phys.SCIEAS1745-247310.1038/nphys1666 6, 428 (2010)].

Dimitrovski, D.; Martiny, C. P. J.; Madsen, L. B.

2010-11-01

115

Strong-field ionization of polar molecules: Stark-shift-corrected strong-field approximation  

SciTech Connect

We extend the molecular strong-field approximation for ionization, in the tunneling limit, to include systematically the linear and quadratic static Stark shifts of the ionizing molecular orbital. This approach, simple to implement, is capable of describing the essential physics of the process of strong-field ionization of oriented polar molecules by circularly polarized laser pulses. The modification of the molecular orbitals in strong fields is also discussed and in cases of extreme polarization of inner electrons a simple model is devised. We find very good agreement between the results from our model and those obtained in the recent experiment on ionizaton of oriented carbonyl sulphide and benzonitrile molecules [L. Holmegaard et al., Nature Phys. 6, 428 (2010)].

Dimitrovski, D.; Martiny, C. P. J.; Madsen, L. B. [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C (Denmark)

2010-11-15

116

d-wave superfluidity in optical lattices of ultracold polar molecules  

SciTech Connect

Recent work on ultracold polar molecules, governed by a generalization of the t-J Hamiltonian, suggests that molecules may be better suited than atoms for studying d-wave superfluidity due to stronger interactions and larger tunability of the system. We compute the phase diagram for polar molecules in a checkerboard lattice consisting of weakly coupled square plaquettes. In the simplest experimentally realizable case where there is only tunneling and an XX-type spin-spin interaction, we identify the parameter regime where d-wave superfluidity occurs. We also find that the inclusion of a density-density interaction destroys the superfluid phase and that the inclusion of a spin-density or an Ising-type spin-spin interaction can enhance the superfluid phase. We also propose schemes for experimentally realizing the perturbative calculations exhibiting enhanced d-wave superfluidity.

Kuns, Kevin A.; Gorshkov, Alexey V. [Institute for Quantum Information, California Institute of Technology, Pasadena, California 91125 (United States); Rey, Ana Maria [JILA, National Institute of Standards and Technology and University of Colorado, Boulder, Colorado 80309-0440 (United States) and Department of Physics, University of Colorado, Boulder, Colorado 80309-0390 (United States)

2011-12-15

117

Highly polarized electrons from superlattice photocathodes  

SciTech Connect

Our collaboration group have continued the research to develop the high performance photocathode and the guns to produce the highly polarized electron beam for high energy accelerator physics. In this report, the experimental results obtained from the photocathodes with superlattice structures, such as, AlGaAs-GaAs, InGaAs-GaAs and InGaAs-AlGaAs are described.

Nakanishi, T.; Okumi, S.; Togawa, K.; Takahashi, C.; Suzuki, C.; Furuta, F.; Ida, T.; Wada, K. [Dept. of Physics, Nagoya University, Chikusa-ku, Nagoya-464 (Japan); Omori, T.; Kurihara, Y.; Tawada, M.; Yoshioka, M. [High Energy Accelerator Research Organization, Tsukuba-305 (Japan); Horinaka, H.; Wada, K.; Matsuyama, T. [College of Engineering, University of Osaka Prefecture, Sakai-593 (Japan); Baba, T.; Mizuta, M. [Fundamental Research Laboratory, NEC Corporation, Tsukuba-305 (Japan)

1998-01-20

118

Charge transfer and polarization at interfaces with conjugated molecules  

NASA Astrophysics Data System (ADS)

The function and efficiency of organic electronic devices is determined to a significant extent by the electronic properties of organic/organic heterojunctions and interfaces between electrodes and organic semiconductors. The energy level alignment between metal electrodes and active organic layers can be adjusted over wide ranges by employing interlayers of strong molecular acceptors and donors that undergo charge transfer reactions with the metal. It will be shown that such interlayers lead to lower charge injection barriers than pristine metals, even when the work function is the same. It is argued that the molecularly modified electrodes are electronically more rigid than their pristine metal counterparts, i.e., the electron spill-out at the organic-terminated surface is less pronounced compared to metal surfaces. The energy levels at organic/organic heterojunctions comprising donors and acceptors as used in organic photovoltaic cells are essentially independent of deposition sequence, as long as supporting electrodes to not induce energy level pinning. When a high work function electrode is used, the energy levels may become Fermi-level pinned and an electric field drops right at the heterojunction. This effect is exemplified for the donor diindenoperylene and the acceptor C60. The electric field distribution within an organic opto-electronic device may thus be adjusted locally by employing interfacial energy level pinning, even at weakly interacting organic/organic interfaces.

Koch, Norbert

2012-02-01

119

Origin and implication of ellipticity in high-order harmonic generation from aligned molecules  

NASA Astrophysics Data System (ADS)

We address theoretically and numerically the possibility of observing ellipticity in high-order harmonic generation (HHG) from aligned molecules driven by linearly polarized fields—a subject of controversy in the recent literature with significant implications. To that end we develop a numerical method for solution of the electronic dynamics and extend a recently developed theory of HHG from aligned molecules. Our numerical results are in good agreement with recent experimental data. The theory explains analytically several observations of polarization experiments. We note the conditions under which ellipticity can be observed and the information content of elliptically polarized harmonics regarding the molecular system.

Ramakrishna, S.; Sherratt, Paul A. J.; Dutoi, Anthony D.; Seideman, Tamar

2010-02-01

120

Polarized electrons from high-gradient guns  

SciTech Connect

To take advantage of the lower emittance associated with extraction fields >> 10 MV/m, a number of technological hurdles must be overcome before photocathodes appropriate for generating polarized electrons can be utilized in high-gradient guns. Both rf guns and very fast ultra-high gradient ({ge} 1 GV/m) diode guns are anticipated. The known problems--some of which may be more than just technical--are delineated, and the present status of relevant research is reviewed.

Clendenin, J.E.; Mulhollan, G.A.

1998-09-01

121

Influence of black-body radiation on alkali-metal polar molecules  

NASA Astrophysics Data System (ADS)

Recent advances in the precise control of ultracold atomic systems led to the creation of ultracold molecules. Prospects of formation of heteronuclear alkali-metal molecules has attracted significant attention, due to its polar character, promising an extra level of control of these complicated systems. The presence of the permanent dipole moment in the polar molecule, however, makes it vulnerable to room temperature black body radiation. This thermal radiation can cause a redistribution of population between rovibrational molecular levels and partial loss of control. We calculate the ''thermal'' life time of the rovibrational levels of the X^1? and a^3? ground states of polar KRb and RbCs molecules. First, we perform a relativistic valence-bond calculation of electronic potentials and permanent dipole moments as a function of internuclear separation. Then we use this data to calculate the rovibrational wavefunctions of the two ground state potentials, as well as the transition matrix elements with the permanent dipole moment. Finally, the lifetimes are calculated. We find that these lifetimes are a few hundred seconds which is much larger than the duration of any current experiment with ultracold gasses.

Kotochigova, S.; Tiesinga, E.; Julienne, P. S.

2004-05-01

122

Laser-induced reactions between a Ca+ Coulomb crystal and polar molecules  

NASA Astrophysics Data System (ADS)

We have studied laser-induced reactions between a Ca+ Coulomb crystal and the polar molecules of NH3 and ND3 at room temperature. The reaction rates of Ca+*(3d2D3/2, 4p2P1/2) + NH3 (ND3) ? products have been determined from time variation of the size of fluorescence images of Ca+ Coulomb crystals. The results show that the reaction rates are very slow, and therefore the reaction-rate measurements between sympathetically cooled molecular ions and slow NH3 (ND3) molecules can be performed using a Ca+ Coulomb crystal as coolant.

Okada, K.; Kimura, N.; Suganuma, T.; Shiina, K.; Furukawa, T.; Takayanagi, T.; Wada, M.; Schuessler, H. A.

2012-11-01

123

Polarization-state dependence of the ionization dynamics of a chiral molecule in intense laser light  

NASA Astrophysics Data System (ADS)

Circular dichroism of a chiral molecule, S(+)2-butanol, is investigated in intense laser light. Although theory suggests the possibility of enhanced differences in absorption (leading to ionization) of circularly polarized light of a particular handedness by a random ensemble of chiral molecules, we report results of experiments that fail to observe such effects. While the ionization probability does not significantly change with the ellipticity of the incident light, fragmentation decreases with enhanced ellipticity. The kinetic-energy release accompanying CH+ formation decreases as the laser light becomes more intense, a possible manifestation of bond softening.

Krishnamurthy, M.; Mathur, D.

2000-06-01

124

Interaction-Induced Chiral Quantum States of the Ultracold Polar Molecules  

NASA Astrophysics Data System (ADS)

The ultracold polar molecules with the tunable dipole-dipole interaction, not only would enable explorations of a large class of exotic many-body physics phenomena, but also could be used for quantum information processing. In the present paper we demonstrate that this dipole-dipole interaction can generate the degenerate chiral quantum states acting as a qubit robust against noise when the ultracold polar molecules are confined by a triangular lattice. Moreover, we also find two first-order quantum phase transitions by controlling an external driving field. One is the transition with the change of the different degenerate chiral quantum states. The other is the transition with the breaking of the degenerate quantum chiral states to the nondegenerate state. In experiment, these first-order quantum phase transitions can be detected by measuring the collective molecular population.

Wang, Ming-Hao; Liang, Jiu-Qing; Ma, Jie; Chen, Gang; Jia, Suo-Tang

2012-11-01

125

The junctional adhesion molecule JAM-C regulates polarized transendothelial migration of neutrophils in vivo.  

PubMed

The migration of neutrophils into inflamed tissues is a fundamental component of innate immunity. A decisive step in this process is the polarized migration of blood neutrophils through endothelial cells (ECs) lining the venular lumen (transendothelial migration (TEM)) in a luminal-to-abluminal direction. By real-time confocal imaging, we found that neutrophils had disrupted polarized TEM ('hesitant' and 'reverse') in vivo. We noted these events in inflammation after ischemia-reperfusion injury, characterized by lower expression of junctional adhesion molecule C (JAM-C) at EC junctions, and they were enhanced by blockade or genetic deletion of JAM-C in ECs. Our results identify JAM-C as a key regulator of polarized neutrophil TEM in vivo and suggest that reverse TEM of neutrophils can contribute to the dissemination of systemic inflammation. PMID:21706006

Woodfin, Abigail; Voisin, Mathieu-Benoit; Beyrau, Martina; Colom, Bartomeu; Caille, Dorothée; Diapouli, Frantzeska-Maria; Nash, Gerard B; Chavakis, Triantafyllos; Albelda, Steven M; Rainger, G Ed; Meda, Paolo; Imhof, Beat A; Nourshargh, Sussan

2011-06-26

126

An analytic model of rotationally inelastic collisions of polar molecules in electric fields  

Microsoft Academic Search

We present an analytic model of thermal state-to-state rotationally inelastic collisions of polar molecules in electric fields. The model is based on the Fraunhofer scattering of matter waves and requires Legendre moments characterizing the ``shape'' of the target in the body-fixed frame as its input. The electric field orients the target in the space-fixed frame and thereby effects a striking

Mikhail Lemeshko; Bretislav Friedrich

2008-01-01

127

Laser-induced reactions between a Ca+ Coulomb crystal and polar molecules  

NASA Astrophysics Data System (ADS)

We have investigated laser-induced reactions between laser-cooled crystallized Ca+ ions and polar molecule NH3 at room temperature. Reaction rates of Ca+* (3d 2D3/2, 4p 2P1/2) + NH3 ? products have been determined from time variation of the size of fluorescence images of Ca+ Coulomb crystals. From the pressure dependence of the reaction rates we determined a lower limit of the reaction rate coefficients.

Kimura, N.; Okada, K.; Shiina, K.; Suganuma, T.; Wada, M.; Schuessler, H. A.

2012-11-01

128

Laser-polarization effects on coherent vibronic excitation of molecules with quasi-degenerate electronic states.  

PubMed

The laser-polarization effects on nonadiabatically coupled ?-electron rotation (ring current) and molecular vibration have been theoretically analyzed for aromatic molecules with quasi-degenerate excited states irradiated by an ultrashort laser pulse of arbitrary polarization. We first derived general formulations of the coherent electronic wave packet and expectation value of electronic angular momentum within a frozen-nuclei model. The relative quantum phase of the superposed quasi-degenerate states, which determines the oscillating behavior of angular momentum, can be manipulated by the ellipticity and orientation of the incident laser. Nuclear wave packet simulations with a model molecule confirmed the controllability of ?-electron rotation, although the angular momentum is gradually reduced by nonadiabatic couplings. The amplitude of molecular vibration depends prominently on the orientation of linear polarization vectors rather than the helicity of circular polarization. The characteristic feature in vibrational amplitudes is attributed to the interference in nonadiabatic transition governed by the relative quantum phase between nuclear wave packets. This offers a new strategy for laser control of molecular vibrations through the wave packet interference in nonadiabatic transition. PMID:22834970

Kanno, Manabu; Ono, Yukari; Kono, Hirohiko; Fujimura, Yuichi

2012-08-10

129

Polarization sensitive, three-dimensional, single-molecule imaging of cells with a double-helix system.  

PubMed

Double-helix point spread function photoactivation-localization microscopy allows three-dimensional (3D) superresolution imaging of objects smaller than the optical diffraction-limit. We demonstrate polarization sensitive detection with 3D super-localization of single-molecules and unveil 3D polarization specific characteristics of single-molecules within the intracellular structure of PtK1 cells expressing photoactivatable green fluorescent protein. The system modulates orthogonal polarization components of single-molecule emissions with a single spatial light modulator and detects them separately with a single detector. Information obtained from the two polarization channels demonstrates polarization based contrast in 3D superresolution imaging. Further, we show that the 3D information from the two channels can be optimally combined to yield up to 30% improvement in localization precision relative to a single polarization channel system. PMID:19997184

Pavani, Sri Rama Prasanna; DeLuca, Jennifer G; Piestun, Rafael

2009-10-26

130

High Resolution Observations of Interstellar Molecules  

NASA Astrophysics Data System (ADS)

Ultra-high resolution (R 500,000) spectroscopy of molecules in the interstellar medium can usually resolve the lines, and determine thermal or turbulent linewidths. Perhaps more importantly, individual velocity components can be isolated which allows considerably more precise comparisons of observations to theoretical models since column densities of individual components can be derived. To date, only relatively few studies have been carried out on molecules whereas the studies of atomic species has been more comprehensive. The study of Crane et al.( APJSupp. 1995, 99,107) resolved all the CH and CH+ lines along me 20 sight lines. This study has revealed interesting trends among these species. Follow-up observations of these sight lines is in progress for other species. Comparison with atomic data and the potential for future studies will be discussed.

Crane, P.

2000-05-01

131

Magnetic surface states in high polarization materials  

NASA Astrophysics Data System (ADS)

Surfaces are often different materials, and typically have a different electronic structure from the bulk and since the dawn of surface science, surface-localized electronic states, surface states, have been extensively studied and investigated with growing accuracy. Of particular importance to spintronics are magnetic surface states. Interfaces will play a very important role in many spintronics devices, yet the interface properties are often ignored, poorly understood or badly characterized. For many nominally half metal materials, materials that in some ground state calculations exhibit 100% spin polarization, the magnetic surface states may significantly reduce the effective spin polarization. We review the magnetic surface states of several well known and often highly touted high spin polarized materials such as NiMnSb, Fe3O4, CoS2 and CrO2. Finally, we summarize surface state measurements of magnetoelectric antiferromagnets Cr2O3, which has electrically controllable net surface spins, a major complication to the study of CrO2 by photoemission.

Wu, Ning; Dowben, Peter A.

2011-09-01

132

Stretching DNA molecules on a flexible substrate, a polarization-dependent fluorescence microscopy study  

NASA Astrophysics Data System (ADS)

DNA molecules absorbed and stretched onto surfaces can be used to analyze DNA structure by imaging fluorescence of labeled hybridization probes or enzymes. A recently proposed method for sequencing by electron microscopy requires either adsorbed single-stranded DNAs or untwisted double-stranded DNA. In this experiment, studies were performed on the adsorption of isolated DNA molecules to a flexible PDMS substrate, which permits continuous stretching, until breakage of the DNA molecules. Lambda and T4 DNAs (48.5 and 165.6 kilobase pairs, respectively) were absorbed onto PDMS out of solution by withdrawing a submerged substrate at a rate of 2mm/s, producing linear molecules deposited on the surface. Incident light polarization was varied and fluorescence emission intensity measured as a function of polarization angle and degree of stretching of the DNA. The stretching and breakage properties of lambda and T-4 DNA on the PDMS substrate were determined. The amount of stretching before breakage occurred was found to be up to 40% relative to the as-deposited length. Supported by NSF-DMR MRSEC program.

Zhu, Ke; Mele, John; Budassi, Julia; Sokolov, Jonathon

2013-03-01

133

Relationship between bipolar moments and molecule-frame polarization parameters in Doppler photofragment spectroscopy  

SciTech Connect

In terms of the molecular-frame polarization parameters {bold a}{sub {bold q}}{sup ({bold k})}(p), an equation is derived that describes the shape of a photofragment Doppler profile as a function of the three angles {Gamma}, {Delta}, and {Phi} that specify the photolysis and probe laser polarizations about the detection axis. This expression is specialized to linearly polarized photolysis and probe laser beams. For the particular value of the angle between the probe laser polarization and the detection axis, {Delta}={pi}/2, this equation can be reduced to the form of well-known laboratory-frame expressions that use the bipolar moment formalism introduced by Dixon. Comparison of these forms shows the equivalence of the two formalisms and gives the relationships between the bipolar moments {beta}{sub Q}{sup K}(k{sub 1}k{sub 2}) and the molecule-frame {bold a}{sub {bold q}}{sup ({bold k})}(p) parameters. We show that linear combinations of the bipolar moments completely describe photofragment polarization in the molecular frame and possess distinct quantum mechanical significance. In particular, it is shown that the coherent contribution to the photofragment alignment is proportional to the linear combination (1/5){beta}{sub 0}{sup 2}(02){minus}(1/7){beta}{sub 0}{sup 2}(22){minus}(12/35){beta}{sub 0}{sup 2}(42). {copyright} {ital 1999 American Institute of Physics.} thinsp

Rakitzis, T.P. [Institute of Electronic Structure and Laser, Foundation for Research and Technology-Hellas, 711 10 Heraklion-Crete (Greece); Hall, G.E.; Costen, M.L. [Chemistry Department, Brookhaven National Laboratory, Upton, New York 11973-5000 (United States); Zare, R.N. [Department of Chemistry, Stanford University, Stanford, California 94305-5080 (United States)

1999-11-01

134

Supramolecular structure of columnar liquid crystalline ?-conjugated oligothiophenes with highly polarized photoluminescence properties  

NASA Astrophysics Data System (ADS)

It is possible to control the alignment of columnar liquid crystalline ?-conjugated systems by controlling photoluminescence (PL) properties to yield a polarized PL effect by shear stress. A polarization ratio of 11.2 at the fluorescence peak was obtained using columnar liquid crystalline ?-conjugated oligothiophenes [T. Yasuda et al., Adv. Funct. Mater. 19, 411 (2009)]. We have therefore revealed the directional distribution of oligothiophene molecules inside the columns, which is the origin of a highly polarized PL emission, through detailed analysis of the dependence of PL polarization ratio on the detection polar angle, assuming that such PL emission is due to the summation of all dipole radiations from oligothiophene molecules in the measured area of the sample.

Minoura, Kiyoshi; Akama, Yusuke; Morita, Jun; Yasuda, Takuma; Kato, Takashi; Shimomura, Takeshi

2009-06-01

135

Ion-assisted ground-state cooling of a trapped polar molecule  

SciTech Connect

We propose and analyze a scheme for sympathetic cooling of the translational motion of polar molecules confined in the wells of a deep optical lattice and interacting one by one with laser-cooled ions in a radio-frequency trap. The energy gap between the excitation spectra of the particles in their respective trapping potentials is bridged by means of a parametric resonance, provided by the additional modulation of the rf field. We analyze two scenarios: simultaneous laser cooling and energy exchange between the ion and the molecule, and a scheme where these two processes take place separately. We calculate the lowest final energy of the molecule and the cooling rate depending on the amplitude of the parametric modulation. For small parametric modulation, the dynamics can be solved analytically within the rotating wave approximation.

Idziaszek, Zbigniew; Calarco, Tommaso; Zoller, Peter [Faculty of Physics, University of Warsaw, PL-00-681 Warsaw (Poland); Institute for Quantum Information Processing, University of Ulm, D-89081 Ulm (Germany); Institute for Quantum Optics and Quantum Information of the Austrian Academy of Sciences and Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria)

2011-05-15

136

Ion-assisted ground-state cooling of a trapped polar molecule  

NASA Astrophysics Data System (ADS)

We propose and analyze a scheme for sympathetic cooling of the translational motion of polar molecules confined in the wells of a deep optical lattice and interacting one by one with laser-cooled ions in a radio-frequency trap. The energy gap between the excitation spectra of the particles in their respective trapping potentials is bridged by means of a parametric resonance, provided by the additional modulation of the rf field. We analyze two scenarios: simultaneous laser cooling and energy exchange between the ion and the molecule, and a scheme where these two processes take place separately. We calculate the lowest final energy of the molecule and the cooling rate depending on the amplitude of the parametric modulation. For small parametric modulation, the dynamics can be solved analytically within the rotating wave approximation.

Idziaszek, Zbigniew; Calarco, Tommaso; Zoller, Peter

2011-05-01

137

Controlling the Hyperfine State of Rovibronic Ground-State Polar Molecules  

SciTech Connect

We report the preparation of a rovibronic ground-state molecular quantum gas in a single hyperfine state and, in particular, the absolute lowest quantum state. This addresses the last internal degree of freedom remaining after the recent production of a near quantum degenerate gas of molecules in their rovibronic ground state, and provides a crucial step towards full control over molecular quantum gases. We demonstrate a scheme that is general for bialkali polar molecules and allows the preparation of molecules in a single hyperfine state or in an arbitrary coherent superposition of hyperfine states. The scheme relies on electric-dipole, two-photon microwave transitions through rotationally excited states and makes use of electric nuclear quadrupole interactions to transfer molecular population between different hyperfine states.

Ospelkaus, S.; Ni, K.-K.; Quemener, G.; Neyenhuis, B.; Wang, D.; Miranda, M. H. G. de; Bohn, J. L.; Ye, J.; Jin, D. S. [JILA, National Institute of Standards and Technology and University of Colorado, and Department of Physics, University of Colorado, Boulder, Colorado 80309-0440 (United States)

2010-01-22

138

Dynamic Core Polarization in Strong-Field Ionization of CO Molecules  

NASA Astrophysics Data System (ADS)

The orientation-dependent strong-field ionization of CO molecules is investigated using the fully propagated three-dimensional time-dependent Hartree-Fock theory. The full ionization results are in good agreement with recent experiments. The comparisons between the full method and the single active orbital method show that although the core electrons are generally more tightly bound and contribute little to the total ionization yields, their dynamics cannot be ignored, which effectively modifies the behavior of electrons in the highest occupied molecular orbital. By incorporating it into the single active orbital method, we identify that the dynamic core polarization plays an important role in the strong-field tunneling ionization of CO molecules, which is helpful for the future development of the tunneling ionization theory of molecules beyond the single active electron approximation.

Zhang, Bin; Yuan, Jianmin; Zhao, Zengxiu

2013-10-01

139

Dielectric relaxation phenomena of rigid polar liquid molecules under giga hertz electric field  

NASA Astrophysics Data System (ADS)

The dielectric relaxation phenomena of rigid polar liquid molecules chloral and ethyltrichloroacetate (j) in benzene, n-hexane and n-heptane (i) under 4.2, 9.8 and 24.6 GHz electric fields at 30oC are studied to show the possible existence of double relaxation times t2 and t1 for rotations of the whole and the flexible parts of molecules. The probability of showing double relaxation is more in aliphatic solvents indicating their nonrigidity. The symmetric and asymmetric distribution parameters g and d are obtained from c 'ij /c 0ij and c''ij/c0ij at wj --> 0 where c'ij and c'ij are real and imaginary parts of the complex orientational susceptibility c*ij and c0ij is the low frequency susceptibility which is real. cij's are involved with the measured dielectric relative permittivities e'ij, e''ij, e 0ij and eij of solutions. The theoretical weighted contributions c1 and c2 towards dielectric dispersions by Fröhlich's method are compared with the experimental ones obtained from the graphical variation of c'ij /c0ij and c''ij/c0ij with weight fractions wj's at wj --> 0. The measured dipole moments m2 and m 1 of the whole and the flexible part of a polar molecule in terms of the linear coefficients b's of c'ij's with wj's and the estimated t2 and t1 reveal their associations with aliphatic solvents. The theoretical dipole moments mtheo's from the available bond angles and bond moments of the substituent polar groups of the molecules with the estimated m's suggest the mesomeric, inductive and electromeric effects in them under GHz electric field.

Dutta, K.; Sit, S. K.; Acharyya, S.

2001-10-01

140

High Intensity Polarized Electron Gun Studies at MIT-Bates  

SciTech Connect

A proposed new high-luminosity electron-ion collider requires a polarized electron source of extremely high intensity. An ion back bombardment of the cathode is the main factor limiting the intensity of modern polarized electron guns. This study examines the possibility of building a very high intensity polarized electron gun.

Tsentalovich, E. [MIT-Bates Linear Accelerator Center, Middleton, MA (United States)

2009-08-04

141

High-Resolution Studies of the Solar Polar Magnetic Fields  

NASA Astrophysics Data System (ADS)

Most observations of the polar magnetic fields of the Sun have been at relatively low resolution. High-resolution studies of the polar fields offer new insight into their evolution. We show that near sunspot maximum in 1989, the polar regions are covered with several unipolar regions, each region containing magnetic knots of both polarities. These knots have average lifetimes greater than 7 hours but less than 24 hours. In 1995, after the polar field reversal was complete, each pole exhibits one dominant polarity, and the dominant polarity knots are in a ratio of 5:1 to the opposite polarity. By measuring the displacement of magnetic knots over a 7 hour period a rotation rate can be determined which is consistent with the Snodgrass (1982) relation determined by cross correlations of Mt. Wilson magnetograms. Most knots are not seen in magnetic bipoles either when the overall polar fields are mixed or when one polarity is dominant.

Varsik, J. R.; Wilson, P. R.; Li, Y.

1996-05-01

142

Enhancement of metallic silver monomer evaporation by the adhesion of polar molecules to silver nanocluster ions  

SciTech Connect

We have compared the metallic evaporation channels from metastable [Ag{sub X=5,7,11}(AgI){sub Y=1-4}]{sup +} clusters in the first field free region of a double focusing mass spectrometer with that of the corresponding pure metallic clusters, [Ag{sub X=5,7,11}]{sup +}. It is found that the presence of the polar AgI molecules increases the rate of silver monomer evaporation relative to that of silver dimer evaporation. Using thermodynamic expressions for the heat of evaporation of the different evaporation processes and assuming the absence of reverse activation energies, an expression for the difference between the activation energy of silver monomer and dimer evaporation is derived. It is shown that dipole/induced-dipole forces resulting from the presence of AgI polar molecules lead to an enhancement of silver monomer evaporation if the polarizability of the pure metallic cluster ions increases with the number of Jellium electrons. Our theoretical calculations of the static polarizabilities of [Ag{sub x}]{sup +}, using time dependent density functional theory within the local density approximation, shows a smooth increase in the polarizabilities with the number of the Jellium electrons in these clusters. Finally, we observe that the enhancement of Ag monomer evaporation per AgI needed is smaller for clusters with an even number of AgI molecules than with an odd number of them. 46 refs., 5 figs., 2 tabs.

Fagerquist, C.K.; Sensharma, D.K.; El-Sayed, M.A. [Univ. of California, Los Angeles, CA (United States); Rubio, A.; Cohen, M.L. [Univ. of California, Berkeley, CA (United States)]|[Lawrence Berkeley Lab., CA (United States)

1995-05-11

143

Orientation analysis of uniaxially drawn polycarbonate films, doped with fluorescent molecules, by UV-dichroism, fluorescence polarization and birefringence  

Microsoft Academic Search

Bis-phenol-A-polycarbonate (PC) is dyed in solution with fluorescent molecules of different shapes and cast to films. Rectangular samples, cut from these films, are drawn varying draw ratio and drawing temperature. The orientation of the fluorescent probes is investigated by dichroism and fluorescence polarization, that of the polymer segments by birefringence. Hermans' orientation factors obtained by dichroism and fluorescence polarization are

H. Springer; R. Neuert; F. D. Miiller; G. Hinrichsen

1984-01-01

144

Circularly polarizing mirrors for high-powered lasers  

SciTech Connect

In this paper, the circular polarizing mirrors for high power lasers have been theoretically and experimentally studied, the circular polarizing mirror coated with multiple film, which could induce 90 deg phase retardation is prepared experimentally.

Chen, Q.; Zhou, F.; Li, X.; He, Y.; Wang, J.

1995-12-07

145

Highly polarized electron beams for linear colliders.  

National Technical Information Service (NTIS)

The SLC operates with electron beams having a polarization of (approximately) 80%. The physics opportunities for future colliders will be greatly enhanced if the beam polarization can be significantly higher. The prospects for achieving electron single-be...

J. E. Clendenin

1998-01-01

146

Multielectron signatures in the polarization of high-order harmonic radiation  

SciTech Connect

The polarization of high-order harmonic radiation emitted from N{sub 2} molecules interacting with a linearly polarized laser pulse is investigated theoretically. We find that the exchange effect between the recombining electron and the bound core electrons imprints a clear signature onto the high-order harmonic polarization and its dependence on the alignment angle between the molecular axis and driving laser electric field. Our analysis reveals an observable for the experimental investigation of many-electron dynamics in intense laser fields.

Zhao Zengxiu; Yuan Jianmin [Department of Physics, National University of Defense Technology, Changsha 410073 (China); Brabec, Thomas [Physics Department and Center for Research in Photonics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario, K1N 6N5 (Canada)

2007-09-15

147

Condensate wave function and elementary excitations of bosonic polar molecules: Beyond the first Born approximation  

SciTech Connect

We investigate the condensate wave function and elementary excitations of strongly interacting bosonic polar molecules in a harmonic trap, treating the scattering amplitude beyond the standard first Born approximation (FBA). By using an appropriate trial wave function in the variational method, effects of the leading-order correction beyond the FBA have been investigated and shown to be significantly enhanced when the system is close to the phase boundary of collapse. How such a leading-order effect of going beyond the FBA can be observed in a realistic experiment is also discussed.

Huang, C.-C.; Wu, W.-C. [Department of Physics, National Taiwan Normal University, Taipei 11650, Taiwan (China); Wang, D.-W. [Physics Department, National Tsing-Hua University, Hsinchu 300, Taiwan (China); Physics Division, National Center for Theoretical Sciences, Hsinchu 300, Taiwan (China)

2010-04-15

148

Condensate wave function and elementary excitations of bosonic polar molecules: Beyond the first Born approximation  

NASA Astrophysics Data System (ADS)

We investigate the condensate wave function and elementary excitations of strongly interacting bosonic polar molecules in a harmonic trap, treating the scattering amplitude beyond the standard first Born approximation (FBA). By using an appropriate trial wave function in the variational method, effects of the leading-order correction beyond the FBA have been investigated and shown to be significantly enhanced when the system is close to the phase boundary of collapse. How such a leading-order effect of going beyond the FBA can be observed in a realistic experiment is also discussed.

Huang, Chao-Chun; Wang, Daw-Wei; Wu, Wen-Chin

2010-04-01

149

Quantum phase transitions in a polarized gas of dipolar molecules forming flexible chain  

NASA Astrophysics Data System (ADS)

We numerically demonstrate the formation of quantum flexible chains in a gas of polar molecules confined into a stack of N 1d or 2d optical lattice layers, and with dipole moment aligned perpendicularly to the layers. Molecules interact via dipole-dipole interaction. Ab initio simulations of a single chain pinned at one end reveal quantum roughening transition. Multi-chain ensemble is studied in the J-current model approximation and chain superfluidity (CSF) is found. Increasing density of the chains leads to quantum phase transition from CSF to N-layered molecular superfluid (N-SF). We discuss the nature of this transition and its dependence on density, and the conditions for experimental realization and detection of the chain soup.

Capogrosso-Sansone, Barbara; Kuklov, Anatoly

2011-03-01

150

Nonadiabatic effects in long-pulse mixed-field orientation of a linear polar molecule  

NASA Astrophysics Data System (ADS)

We present a theoretical study of the impact of an electrostatic field combined with nonresonant linearly polarized laser pulses on the rotational dynamics of linear molecules. Within the rigid rotor approximation, we solve the time-dependent Schrödinger equation for several field configurations. Using the carbonyl sulfide molecule as the prototype, the field-dressed dynamics is analyzed in detail for experimentally accessible static-field strengths and laser pulses. Results for directional cosines are presented and compared to the predictions of the adiabatic theory. We demonstrate that for the prototypical field configuration used in current mixed-field orientation experiments, the molecular field dynamics is, in general, nonadiabatic, and a time-dependent description of these systems is mandatory. We investigate several field regimes identifying the sources of nonadiabatic effects and provide the field parameters under which the adiabatic dynamics would be achieved.

Omiste, Juan J.; González-Férez, Rosario

2012-10-01

151

Two-center minima in harmonic spectra from aligned polar molecules  

SciTech Connect

We extend a model of two-center interference to include the superposition of opposite orientations in aligned polar molecules. We show that the position of the minimum in the harmonic spectrum from both aligned and oriented CO depends strongly on the relative recombination strength at different atoms, not just the relative phase. We reinterpret the minimum in aligned CO as an interference between opposite orientations, and obtain good agreement with numerical calculations. Inclusion of the first-order Stark effect shifts the position of the interference minimum in aligned CO even though aligned molecules do not posses total permanent dipoles. We explain the shift in terms of the phase that the electron of oriented CO accumulates due to the Stark effect.

Etches, Adam [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C (Denmark); Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States); Gaarde, Mette B. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States); Madsen, Lars Bojer [Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, 8000 Aarhus C (Denmark)

2011-08-15

152

Polarized Protein-Specific Charges from Atoms-in-Molecule Electron Density Partitioning  

PubMed Central

Atomic partial charges for use in traditional force fields for biomolecular simulation are often fit to the electrostatic potentials of small molecules and, hence, neglect large-scale electronic polarization. On the other hand, recent advances in atoms-in-molecule charge derivation schemes show promise for use in flexible force fields but are limited in size by the underlying quantum mechanical calculation of the electron density. Here, we implement the density derived electrostatic and chemical charges method in the linear-scaling density functional theory code ONETEP. Our implementation allows the straightforward derivation of partial atomic charges for systems comprising thousands of atoms, including entire proteins. We demonstrate that the derived charges are chemically intuitive, reproduce ab initio electrostatic potentials of proteins and are transferable between closely related systems. Simulated NMR data derived from molecular dynamics of three proteins using force fields based on the ONETEP charges are in good agreement with experiment.

2013-01-01

153

Single Molecule Detection Technologies in Miniaturized High Throughput Screening: Fluorescence Correlation Spectroscopy  

Microsoft Academic Search

Fluorescence assay technologies used for miniaturized high throughput screening are broadly divided into two classes. Macroscopic fluorescence techniques (encompassing conventional fluorescence intensity, anisotropy [also often referred to as fluorescence polarization] and energy transfer) monitor the assay volume- and time-averaged fluorescence output from the ensemble of emitting fluorophores. In contrast, single-molecule detection (SMD) techniques and related approaches, such as fluorescence correlation

Keith J. Moore; Sandra Turconi; Stephen Ashman; Martin Ruediger; Ulrich Haupts; Victoria Emerick; Andrew J. Pope

1999-01-01

154

Solid phases and pairing in a mixture of polar molecules and atoms  

SciTech Connect

We consider a mixture of hard-core bosonic polar molecules, interacting via repulsive dipole-dipole interaction, and one atomic bosonic species. The mixture is confined on a two-dimensional square lattice and, at low enough temperatures, can be described by the two-component Bose-Hubbard model. The latter displays an extremely rich phase diagram including solid, superfluid, and supersolid phases. Here, we mainly focus on the checkerboard molecular solid, stabilized by the long-range dipolar interaction, and study how the presence of atoms affects its robustness both at zero and finite temperatures. We find that, due to atom-molecule interactions, solid phases can be stabilized at both (much) lower strengths of dipolar interaction and higher temperatures, than when no atoms are present. As a byproduct, atoms also order in a solid phase with the same melting temperatures as for molecules. Finally, we find that for large enough interaction between atoms and molecules, a paired supersolid phase can be stabilized.

Capogrosso-Sansone, B. [Institute for Theoretical Atomic, Molecular, and Optical Physics, Harvard-Smithsonian Center of Astrophysics, Cambridge, Massachusetts 02138 (United States)

2011-05-15

155

The Future of High Energy Polarized Proton Beams  

SciTech Connect

The acceleration and storage of high energy polarized proton beams has made tremendous progress over the last forty years challenging along the way the technologies, precision and the understanding of the beam dynamics of accelerators. This progress is most evident in that one can now contemplate high energy colliders with polarized beams and high luminosity at the same time. After a brief summary of the development and history of polarized proton beam acceleration the paper will focus on the highest energy polarized beams and the possibility of accelerating polarized beams to even higher energies in the future.

Roser, Thomas [Brookhaven National Laboratory, Upton, New York 11793-5000 (United States)

2009-08-04

156

Generation of a radially polarized doughnut mode of high quality  

Microsoft Academic Search

We present an experimental set-up to generate laser beams with locally varying polarization distribution. In a linear set-up, a radially polarized beam of high quality regarding intensity distribution, polarization and phase-front distortion is generated. This beam can be used for tight focusing. Further applications are discussed.

S. Quabis; R. Dorn; G. Leuchs

2005-01-01

157

Highly Polarized and Self-Waveguided Emission from Single-Crystalline Organic Nanobelts  

SciTech Connect

Well-defined single-crystalline nanobelts with strong fluorescence were fabricated from a perylene tetracarboxylic diimide molecule modified with specific side-chains that afford flip-flap stacking, rather than the common translated stacking, between the molecules along the long axis of the nanobelt. The nanobelts thus fabricated possess highly polarized, self-waveguided emission, making them ideal candidates for application in nanolasers and other angle-dependent optical nanodevices.

Che, Yanke; Yang, Xiaomei; Balakrishnan, Kaushik; Zuo, Jianmin; Zang, Ling; (UIUC); (Rice); (Utah)

2009-09-15

158

Ground state of the polar alkali-metal-atom-strontium molecules: Potential energy curve and permanent dipole moment  

SciTech Connect

In this study, we investigate the structure of the polar alkali-metal-atom-strontium diatomic molecules as possible candidates for the realization of samples of ultracold polar molecular species not yet investigated experimentally. Using a quantum chemistry approach based on effective core potentials and core polarization potentials, we model these systems as effective three-valence-electron systems, allowing for calculation of electronic properties with full configuration interaction. The potential curve and the permanent dipole moment of the {sup 2}{Sigma}{sup +} ground state are determined as functions of the internuclear distance for LiSr, NaSr, KSr, RbSr, and CsSr molecules. These molecules are found to exhibit a significant permanent dipole moment, though smaller than those of the alkali-metal-atom-Rb molecules.

Guerout, R. [Laboratoire Kastler-Brossel, CNRS, ENS, Univ Pierre et Marie Curie case 74, Campus Jussieu, F-75252 Paris Cedex 05 (France); Aymar, M.; Dulieu, O. [Laboratoire Aime Cotton, CNRS, UPR3321, Bat. 505, Univ Paris-Sud, F-91405 Orsay Cedex (France)

2010-10-15

159

Role of ellipticity in high-order harmonic generation by homonuclear diatomic molecules  

SciTech Connect

We present a theory of high-order harmonic generation by diatomic molecules exposed to an elliptically polarized laser field. This theory is based on the molecular strong-field approximation with the laser-field-dressed initial bound state and the undressed final state. The interference minima, observed for linear polarization, are blurred with the increase of the laser-field ellipticity. The nth harmonic emission rate has contributions of the components of the T-matrix element in the direction of the laser-field polarization and in the direction perpendicular to it. We analyze the destructive interference condition for this perpendicular component. Taking into account that the aligned molecules are an anisotropic medium for high-harmonic generation, we introduce elliptic dichroism as a measure of this anisotropy and discuss possibilities of its use for determining the molecular structure.

Odzak, S. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegowina); Milosevic, D. B. [Faculty of Science, University of Sarajevo, Zmaja od Bosne 35, 71000 Sarajevo (Bosnia and Herzegowina); Max-Born-Institut, Max-Born-Strasse 2a, D-12489 Berlin (Germany)

2010-08-15

160

ORIENTED POLAR MOLECULES DOPED PMMA POLYMERIC FILMS: CHARACTERIZATION BY KELVIN PROBE TECHNIQUE AND ATOMIC FORCE MICROSCOPY  

Microsoft Academic Search

1.Abstract Betaine type dipolar molecules have received considerable attention because of their large dipole moments and optical non-linearities. The host-guest systems are chosen. The high-electric field corona poling was used to generate dipole orientation of betaine molecules in polymer matrices. Atom force microscopy and surface potential studies yield useful information regarding both structural and electronic properties of casted host-guest polymer

D. Cepite; E. Fonavs; I. Muzikante; A. Tokmakov; D. Erts; B. Polakov

161

Induced and Form Birefringence in High-Frequency Polarization Gratings  

NASA Astrophysics Data System (ADS)

High-frequency phase polarization gratings are fabricated holographically in dichromated gelatin dyed with malachite green. It is observed that the intensity of the -1 diffracted beam is a sinusoidal function of the incident polarization angle. In addition, we analyze the dependence of the diffracted order polarization on grating frequency. It is evident from our results that form birefringence becomes significant when the grating period is smaller than the illumination wavelength, thus modifying the optically induced birefringence. Then, in polarization hologram reconstruction, it is not possible to obtain the polarization distribution at the recording step for high-frequency objects.

Martinez-Ponce, Geminiano; Solano, Cristina

2001-08-01

162

Cold ion-polar-molecule reactions studied with a combined Stark-velocity-filter-ion-trap apparatus  

NASA Astrophysics Data System (ADS)

We have developed a combined Stark-velocity-filter-ion-trap apparatus for the purpose of reaction-rate measurements between cold trapped ions and slow polar molecules under ultrahigh vacuum conditions. The prerequisite steps such as the characterization of velocity-selected polar molecules (PM), namely ND3, H2CO, and CH3CN, were performed using time-of-flight (TOF) measurements. We confirmed the generation of slow ND3, H2CO, and CH3CN molecules having thermal energies of a few Kelvin. Additionally, the number densities of the slow velocity-filtered polar molecules were determined to be in the range of n=104 to 106 cm-3 by calibrating the TOF signals. In a first experiment, the Stark velocity filter was connected to a cryogenic linear Paul trap and reaction-rate measurements between laser-cooled Ca+ Coulomb crystals and velocity-selected polar molecules were carried out. The observed reaction rates are of the order of 10-5 s-1, which are much slower than typical reaction rates of molecular ion-polar-molecule reactions at low temperatures. The present results confirm that reaction-rate measurements between velocity-selected polar molecules and sympathetically cooled molecular ions cooled by a laser-cooled Ca+ Coulomb crystal can be performed. Next we measured the reaction rates between sympathetically cooled nonfluorescent stored ion molecules namely N2H+ ions and velocity-selected CH3CN molecules at the average reaction energy of about 3 K. The measured reaction rate of 2.0(2)×10-3 s-1 is much faster than those of the Ca++PM reactions. This is strong evidence that the velocity-selected polar molecules undergo reactive collisions. We also confirmed that the present reaction-rate constant of CH3CN+N2H+ ? CH3CNH++N2 is consistent with the estimated values from the room temperature results and the trajectory-scaling formula of Su In the future, the present velocity-filter combined cryogenic trap apparatus will enable us to perform systematic measurements of cold ion-polar-molecule reactions, which are important problems from a fundamental viewpoint and also contribute to astrochemistry.

Okada, Kunihiro; Suganuma, Takuya; Furukawa, Takahiro; Takayanagi, Toshinobu; Wada, Michiharu; Schuessler, Hans A.

2013-04-01

163

Level anti-crossings in ParaHydrogen Induced Polarization experiments with Cs-symmetric molecules  

NASA Astrophysics Data System (ADS)

Hyperpolarization by means of ParaHydrogen Induced Polarization (PHIP) has found increasing applications since its discovery. However, in the last decade only a few experiments have been reported describing the hydrogenation of symmetric molecules. A general AA?BB? system is studied here. Calculations of the spin dynamics with the density matrix formalism support the experimental findings, providing profound understanding of the experiments in Cs-symmetric molecules. Level anti-crossings between states related to the triplet and the singlet state of one pair of the protons are identified as being responsible for hyperpolarization transfer in a PHIP experiment, when the former p-H2 protons occupy the sites AA?.The hydrogenation of acetylene dicarboxylic acid dimethylester with parahydrogen is used to illustrate the case. The theoretical treatment applied to this particular reaction explains the signal enhancements in both groups of protons in the spectrum when the sample is placed in the proper magnetic field strength, including the phase inversion of the signal of the methyl group.The treatment described here can be extended to every molecule which can be approximated as an AA?BB? system.

Buljubasich, L.; Franzoni, M. B.; Spiess, H. W.; Münnemann, K.

2012-06-01

164

Polarity inversion in high Mg-doped In-polar InN epitaxial layers  

SciTech Connect

To investigate the Mg-dopability in In-polar InN epilayers grown by molecular beam epitaxy, polarity inversion dependence on Mg-doping level is studied. A multiple-InN layer-structure sample with different Mg-doping levels is grown and analyzed by transmission electron microscopy. Formation of high density V-shaped inversion domains is observed for the Mg-doped InN with Mg concentration ([Mg]) of 2.9x10{sup 19} cm{sup -3}. These domains lead to polarity inversion from In to N polarity. Further study for Mg-doped InN epilayers shows that polarity inversion takes place when [Mg] increases above 1.6x10{sup 19} cm{sup -3}. It is also shown that the Mg-sticking coefficient is almost independent of the polarity.

Wang Xinqiang; Che, Song-Bek; Ishitani, Yoshihiro; Yoshikawa, Akihiko; Sasaki, Hirokazu; Shinagawa, Tatsuyuki; Yoshida, Seikoh [Graduate Course of Electrical and Electronics Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan) and InN-Project as a CREST program of JST, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522 (Japan); Yokohama R and D Laboratories, Furukawa Electric Co., Ltd., 2-4-3 Okano, Nishi-ku, Yokohama 220-0073 (Japan)

2007-08-20

165

Single-Molecule Fluorescence Polarization Study of Conformational Change in Archaeal Group II Chaperonin  

PubMed Central

Group II chaperonins found in archaea and in eukaryotic cytosol mediate protein folding without a GroES-like cofactor. The function of the cofactor is substituted by the helical protrusion at the tip of the apical domain, which forms a built-in lid on the central cavity. Although many studies on the change in lid conformation coupled to the binding and hydrolysis of nucleotides have been conducted, the molecular mechanism of lid closure remains poorly understood. Here, we performed a single-molecule polarization modulation to probe the rotation of the helical protrusion of a chaperonin from a hyperthermophilic archaeum, Thermococcus sp. strain KS-1. We detected approximately 35° rotation of the helical protrusion immediately after photorelease of ATP. The result suggests that the conformational change from the open lid to the closed lid state is responsible for the approximately 35° rotation of the helical protrusion.

Iizuka, Ryo; Ueno, Taro; Morone, Nobuhiro; Funatsu, Takashi

2011-01-01

166

Polarized stimulated emission from photonic molecule states in coupled microdisk lasers  

NASA Astrophysics Data System (ADS)

Recent studies have demonstrated the engineering of spin coherence via photon-spin interactions in microdisk lasers [S. Ghosh et al., Nature (Materials) 5, 261 (2006)], motivating the extension of such measurements to pairs of microdisks coupled through the evanescent electromagnetic field. Such coupled microdisks behave like ``photonic molecules'' (PMs) with bonding and antibonding states for the confined photon modes [A. Nakagawa et al., Appl. Phys. Lett. 86, 04112 (2005)]. We describe the fabrication and optical characterization of different PM geometries, consisting of laterally coupled GaAs/GaAlAs microdisks of both circular and elliptical shape. Steady state photoluminescence measurements reveal bonding and antibonding modes with distinct geometry-dependent polarization characteristics that are consistent with finite-difference time-domain simulations. We also discuss time-resolved optical measurements that probe both carrier and spin dynamics in these PMs.

Li, X.; Cooley, B. J.; Samarth, N.; Mendoza, F. M.; Myers, R. C.; Awschalom, D. D.

2007-03-01

167

Simultaneous magneto-optical trapping of lithium and ytterbium atoms towards production of ultracold polar molecules  

NASA Astrophysics Data System (ADS)

We have successfully implemented the first simultaneous magneto-optical trapping (MOT) of lithium (6Li) and ytterbium (174Yb) atoms towards production of ultracold polar molecules of LiYb. For this purpose, we developed the dual atomic oven which contains both atomic species as an atom source and successfully observed the spectra of the Li and Yb atoms in the atomic beams from the dual atomic oven. We constructed the vacuum chamber including the glass cell with the windows made of zinc selenium (ZnSe) for the CO2 lasers, which are the useful light sources of optical trapping for evaporative and sympathetic cooling. Typical atom numbers and temperatures in the compressed MOT are 7×103 atoms, 640 ?K for 6Li, 7×104 atoms, and 60 ?K for 174Yb, respectively.

Okano, M.; Hara, H.; Muramatsu, M.; Doi, K.; Uetake, S.; Takasu, Y.; Takahashi, Y.

2010-03-01

168

Spin polarized conductance study of self-assembled molecules on magnetic surface  

NASA Astrophysics Data System (ADS)

Using first-principles gradient corrected density functional method and super cell approach, we have investigated the adsorption of alkane thiol monolayer on the magnetic Ni(111) surface. Three fold hollow sites are found to be energetically more favorable sites for adsorption with binding energy of 2.6 eV, which is consistent with recent experimental measurement. Magnetic moment per atom for the adsorbed surface is found to be 0.68 ?B as compared to the 0.71 ?B per atom for bare Ni(111) surface. Spin polarized conductance at zero bias limit have been studied and the results are analyzed on the basis of local density of states, charge transfer from metal to molecule and location of molecular states relative to the equilibrium Fermi energy.

Pati, Ranjit; Nayak, Saroj K.

2004-03-01

169

Polarization optics for high-brightness synchrotron x rays  

Microsoft Academic Search

High-brightness synchrotron radiation sources provide highly polarized x-rays for a broad range of studies in materials science, biology, chemistry, and physics. Special insertion devices and x-ray optics such as phase plates can further enhance the purity and the tunability of the polarization of a synchrotron x-ray beam. There are therefore growing interests and activities in making better polarized x-ray sources,

Qun Shen

1996-01-01

170

Collectively Induced Quantum-Confined Stark Effect in Monolayers of Molecules Consisting of Polar Repeating Units  

PubMed Central

The electronic structure of terpyrimidinethiols is investigated by means of density-functional theory calculations for isolated molecules and monolayers. In the transition from molecule to self-assembled monolayer (SAM), we observe that the band gap is substantially reduced, frontier states increasingly localize on opposite sides of the SAM, and this polarization in several instances is in the direction opposite to the polarization of the overall charge density. This behavior can be analyzed by analogy to inorganic semiconductor quantum-wells, which, as the SAMs studied here, can be regarded as semiperiodic systems. There, similar observations are made under the influence of a, typically external, electric field and are known as the quantum-confined Stark effect. Without any external perturbation, in oligopyrimidine SAMs one encounters an energy gradient that is generated by the dipole moments of the pyrimidine repeat units. It is particularly strong, reaching values of about 1.6 eV/nm, which corresponds to a substantial electric field of 1.6 × 107 V/cm. Close-lying ?- and ?-states turn out to be a particular complication for a reliable description of the present systems, as their order is influenced not only by the docking groups and bonding to the metal, but also by the chosen computational approach. In the latter context we demonstrate that deliberately picking a hybrid functional allows avoiding pitfalls due to the infamous self-interaction error. Our results show that when aiming to build a monolayer with a specific electronic structure one can not only resort to the traditional technique of modifying the molecular structure of the constituents, but also try to exploit collective electronic effects.

2011-01-01

171

Collectively induced quantum-confined Stark effect in monolayers of molecules consisting of polar repeating units.  

PubMed

The electronic structure of terpyrimidinethiols is investigated by means of density-functional theory calculations for isolated molecules and monolayers. In the transition from molecule to self-assembled monolayer (SAM), we observe that the band gap is substantially reduced, frontier states increasingly localize on opposite sides of the SAM, and this polarization in several instances is in the direction opposite to the polarization of the overall charge density. This behavior can be analyzed by analogy to inorganic semiconductor quantum-wells, which, as the SAMs studied here, can be regarded as semiperiodic systems. There, similar observations are made under the influence of a, typically external, electric field and are known as the quantum-confined Stark effect. Without any external perturbation, in oligopyrimidine SAMs one encounters an energy gradient that is generated by the dipole moments of the pyrimidine repeat units. It is particularly strong, reaching values of about 1.6 eV/nm, which corresponds to a substantial electric field of 1.6 × 10(7) V/cm. Close-lying ?- and ?-states turn out to be a particular complication for a reliable description of the present systems, as their order is influenced not only by the docking groups and bonding to the metal, but also by the chosen computational approach. In the latter context we demonstrate that deliberately picking a hybrid functional allows avoiding pitfalls due to the infamous self-interaction error. Our results show that when aiming to build a monolayer with a specific electronic structure one can not only resort to the traditional technique of modifying the molecular structure of the constituents, but also try to exploit collective electronic effects. PMID:21955058

Rissner, Ferdinand; Egger, David A; Natan, Amir; Körzdörfer, Thomas; Kümmel, Stephan; Kronik, Leeor; Zojer, Egbert

2011-10-27

172

Detecting high-density ultracold molecules using atom-molecule collision  

NASA Astrophysics Data System (ADS)

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 X1?+g ground state 85Rb2 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 85Rb2 molecules in the optical trap was estimated to be >5.2 × 1011 cm-3.

Chen, Jun-Ren; Kao, Cheng-Yang; Chen, Hung-Bin; Liu, Yi-Wei

2013-04-01

173

Polymeric light-emitting diodes with highly polarized blue emission  

Microsoft Academic Search

Polymer light-emitting diodes (LED) with aligned conjugated molecules and polymers as the active layer can emit polarized light as shown recently in several reports. We have synthesized several liquid-crystalline polyfluorenes with different side chain patterns. The thin polymer films were aligned at elevated temperatures on a rubbed polyimide layer. For the most suitable substitution, a dichroic ratio of twelve was

Tzenka Miteva; Andreas Meisel; Heinz-Georg Nothofer; Ullrich Scherf; Wolfgang Knoll; Dieter Neher; Martin Grell; Donald Lupo; Akio Yasuda

1999-01-01

174

Generating long-lasting 1H and 13C hyperpolarization in small molecules with parahydrogen-induced polarization  

NASA Astrophysics Data System (ADS)

Recently, Levitt and co-workers demonstrated that conserving the population of long-lasting nuclear singlet states in weak magnetic fields can lead to a preservation of nuclear spin information over times substantially longer than governed by the (high-field) spin-lattice relaxation time T1. Potential benefits of the prolonged spin information for magnetic resonance imaging and spectroscopy were pointed out, particularly when combined with the parahydrogen induced polarization (PHIP) methodology. In this contribution, we demonstrate that an increase of the effective relaxation time by a factor up to three is achieved experimentally, when molecules hyperpolarized by PHIP are kept in a weak magnetic field instead of the strong field of a typical NMR magnet. This increased lifetime of spin information makes the known PHIP phenomena more compatible with the time scales of biological processes and, thus, more attractive for future investigations.

Jonischkeit, Thorsten; Bommerich, Ute; Stadler, Jörg; Woelk, Klaus; Niessen, Heiko G.; Bargon, Joachim

2006-05-01

175

Junctional adhesion molecule-A participates in the formation of apico-basal polarity through different domains  

Microsoft Academic Search

Junctional adhesion molecule (JAM)-A is an integral membrane protein at tight junctions of epithelial cells which associates with the cell polarity protein PAR-3. Here, we demonstrate that downregulation of JAM-A impairs the ability of MDCK II cells to form cysts in a three-dimensional matrix indicating the requirement of JAM-A for the development of apico-basal polarity. To define the regions of

Daniela Rehder; Sandra Iden; Ines Nasdala; Joachim Wegener; Maria-Katharina Meyer Zu Brickwedde; Dietmar Vestweber; Klaus Ebnet

2006-01-01

176

Pendular States of Highly Vibrationally Excited Molecules  

SciTech Connect

The behavior of coherent field-induced hybrids of field-free rotor states ({open_quotes}pendular states{close_quotes}) is studied in energy regions where intramolecular vibrational energy redistribution phenomena are important. The energy region corresponding to the 4{nu}{sub 1} band system of HCCF molecules, at approximately 12thinsp800 cm{sup {minus}1} , has been chosen as an example. The calculations show that the expectation value of the orientation of molecules prepared in nonstationary pendular bright states exhibits a slow decay to the equilibrium value. Therefore the molecules substantially conserve their initial orientation after intramolecular vibrational redistribution takes place. {copyright} {ital 1999} {ital The American Physical Society}

Ortigoso, J. [Instituto de Estructura de la Materia, CSIC, Serrano 121, 28006 Madrid (Spain); Ortigoso, J.; Fraser, G.T. [Optical Technology Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 (United States); Pate, B.H. [Department of Chemistry, University of Virginia, Charlottesville, Virginia 22901 (United States)

1999-04-01

177

Towards efficient ab initio calculations of electron scattering by polyatomic molecules: III. Modelling correlation-polarization interactions  

NASA Astrophysics Data System (ADS)

We explore an implementation of correlation-polarization interactions for electron scattering by polyatomic molecules. The short-range correlation is approximated by local and nonlocal density functional theory (DFT) models commonly used in quantum chemistry and solid-state physics. The long-range polarization is represented by general full tensor components. Furthermore, we propose a robust and stable technique to calculate momentum-space matrix elements of such a composite potential. The quality of several selected DFT potentials is tested by elastic scattering calculations for a class of small hydrocarbon molecules represented by propane and cyclopropane.

?urík, R.; Šulc, M.

2010-09-01

178

Intracluster Ion Molecule Reactions Following the Generation of Mg+ Within Polar Clusters  

PubMed Central

In this work we investigated the intracluster ion molecule reactions following the generation of Mg+ within the polar clusters (water, methanol, ether and acetonitrile), using time of flight mass spectrometry. In the case of Mg+/water and Mg+/methanol, dehydrogenation reactions are observed after the addition of five molecules. However, no dehydrogenation reactions are observed in the case of Mg+/ether or Mg+/acetonitrile clusters. This confirms the role of the H atom in (O–H) in the dehydrogenation reaction, and rules out any contribution from the H atom in the CH3 group. In addition, the magic numbers in the time of flight (TOF) mass spectra of the Mg+Xn clusters (X = H2O, CH3OH, CH3OCH3 and CH3CN) have been investigated. Finally, the role of ground electronic magnesium ion Mg+(2S1/2), and excited electronic magnesium ion Mg+(2P1/2) in the dehydrogenation reaction were investigated using Ion Mobility Mass spectrometry. The results offer direct evidence confirming the absence of the electronically excited, Mg+(2P1/2).

Alsharaeh, Edreese H.

2011-01-01

179

Orbital geometry determined by orthogonal high-order harmonic polarization components  

SciTech Connect

We study the polarization state of high-order harmonics produced by linearly polarized light interacting with two-center molecules. By generating high-harmonic 'polarization maps' from Radon transformations of excited electronic wave functions, we show that the polarization of the harmonic radiation can be linked to the geometry of the molecular orbital. While in the Radon transformation the plane-wave approximation for the rescattered electron is implicitly assumed, numerical solutions of the two-dimensional time-dependent Schro{center_dot}{center_dot}dinger equation, in which this approximation is not made, confirm the validity of this topological connection. We also find that measuring two orthogonal amplitude components of the harmonics provides a method for quantum tomography that substantially improves the quality of reconstructed molecular states.

Hijano, Eliot [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); Serrat, Carles [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); DTDI, Universitat de Vic, Carrer de la Laura 13, E-08500 Vic (Barcelona) (Spain); Gibson, George N. [Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States); Biegert, Jens [ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, E-08860 Castelldefels (Barcelona) (Spain); ICREA-Institucio Catalana de Recerca i Estudis Avancats, E-08010 Barcelona (Spain)

2010-04-15

180

Ultracold spin-polarized mixtures of 2? molecules with S-state atoms: Collisional stability and implications for sympathetic cooling  

NASA Astrophysics Data System (ADS)

The prospects of sympathetic cooling of polar molecules with magnetically cotrapped alkali-metal atoms are generally considered poor due to strongly anisotropic atom-molecule interactions leading to large spin relaxation rates. Using rigorous quantum scattering calculations based on ab initio interaction potentials, we show that inelastic spin relaxation in low-temperature collisions of CaH(2?) molecules with Li and Mg atoms occurs at a slow rate despite the strongly anisotropic interactions. This unexpected result, which we rationalize using multichannel quantum-defect theory, opens up the possibility of sympathetic cooling of polar 2? molecules with alkali-metal atoms in a magnetic trap and with alkaline-earth-metal atoms in an optical dipole trap.

Tscherbul, T. V.; K?os, J.; Buchachenko, A. A.

2011-10-01

181

Electric-field-dependent dynamic polarizability and state-insensitive conditions for optical trapping of diatomic polar molecules  

SciTech Connect

Selection of state-insensitive or 'magic' trapping conditions with ultracold atoms or molecules, where pairs of internal states experience identical trapping potentials, brings substantial benefits to precision measurements and quantum computing schemes. Working at such conditions could ensure that the detrimental effects of inevitable inhomogeneities across an ultracold sample are significantly reduced. However, this aspect of confinement remains unexplored for ultracold polar molecules. Here, we present means to control the ac Stark shift of rotational states of ultracold diatomic polar molecules, when subjected to both trapping laser light and an external electric field. We show that both the strength and relative orientation of the two fields influence the trapping potential. In particular, we predict 'magic electric field strengths' and a 'magic angle', where the Stark shift is independent of the dc external field for certain rotational states of the molecule.

Kotochigova, Svetlana [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122-6082 (United States); DeMille, David [Department of Physics, Yale University, New Haven, Connecticut 06520 (United States)

2010-12-15

182

Highly efficient generation of vector beams through polarization holograms  

NASA Astrophysics Data System (ADS)

We report a highly efficient and flexible method to yield vector beams (VBs) with spatially variant amplitude, phase and polarization by means of two polarization holograms (PHs). Left- and right-hand circularly polarized scalar beams, generated by the first hologram, are collinearly recombined by the second one to produce the vector beams. By taking advantage of the diffraction properties, the high efficiency, and the intrinsic achromaticity of the polarization holograms, the method aims to overcome the limitations related to stability and efficiency, making it attractive for applications. Theoretical analysis, based on the Jones formalism, and experimental results are shown.

Ruiz, U.; Pagliusi, P.; Provenzano, C.; Cipparrone, G.

2013-04-01

183

Singlet and triplet Bardeen-Cooper-Schrieffer pairs in a gas of two-species fermionic polar molecules  

SciTech Connect

Taking into account the deformation of the Fermi surface, we investigate the spin-singlet and -triplet BCS pairings in a mixture of fermionic polar molecules with two different hyperfine states. In particular, we explore the relation between the critical temperatures and the Fock-exchange interaction. We also show that, by tuning short-range interaction between interspecies molecules, the singlet- and triplet-paired superfluids may coexist.

Shi, T.; Zhang, J.-N.; Sun, C.-P.; Yi, S. [Key Laboratory of Frontiers in Theoretical Physics, Institute of Theoretical Physics, Chinese Academy of Sciences, Beijing 100190 (China)

2010-09-15

184

Highly Polarized Ion Sources for Electron Ion Colliders (EIC)  

SciTech Connect

The operation of the RHIC facility at BNL and the Electron Ion Colliders (EIC) under development at Jefferson Laboratory and BNL need high brightness ion beams with the highest polarization. Charge exchange injection into a storage ring or synchrotron and Siberian snakes have the potential to handle the needed polarized beam currents, but first the ion sources must create beams with the highest possible polarization to maximize collider productivity, which is proportional to a high power of the polarization. We are developing one universal H-/D- ion source design which will synthesize the most advanced developments in the field of polarized ion sources to provide high current, high brightness, ion beams with greater than 90% polarization, good lifetime, high reliability, and good power efficiency. The new source will be an advanced version of an atomic beam polarized ion source (ABPIS) with resonant charge exchange ionization by negative ions. An integrated ABPIS design will be prepared based on new materials and an optimized magnetic focusing system. Polarized atomic and ion beam formation, extraction, and transport for the new source will be computer simulated.

V.G. Dudnikov, R.P. Johnson, Y.S. Derbenev, Y. Zhang

2010-03-01

185

Functional Fixedness and Functional Reduction as Common Sense Reasonings in Chemical Equilibrium and in Geometry and Polarity of Molecules.  

ERIC Educational Resources Information Center

Focuses on learning difficulties in procedural knowledge, and assesses the procedural difficulties of grade 12 and first- and third-year university students based on common sense reasoning in two areas of chemistry--chemical equilibrium and geometry, and polarity of molecules. (Contains 55 references.) (Author/YDS)

Furio, C.; Calatayud, M. L.; Barcenas, S. L.; Padilla, O. M.

2000-01-01

186

Functional Fixedness and Functional Reduction as Common Sense Reasonings in Chemical Equilibrium and in Geometry and Polarity of Molecules.  

ERIC Educational Resources Information Center

|Focuses on learning difficulties in procedural knowledge, and assesses the procedural difficulties of grade 12 and first- and third-year university students based on common sense reasoning in two areas of chemistry--chemical equilibrium and geometry, and polarity of molecules. (Contains 55 references.) (Author/YDS)|

Furio, C.; Calatayud, M. L.; Barcenas, S. L.; Padilla, O. M.

2000-01-01

187

Polarized neutron reflectometry in high magnetic fields  

SciTech Connect

A simple method is described to maintain the polarization of a neutron beam on its way through the large magnetic stray fields produced by a vertical field of a cryomagnet with a split-coil geometry. The two key issues are the proper shielding of the neutron spin flippers and an additional radial field component in order to guide the neutron spin through the region of the null point (i.e., point of reversal for the vertical field component). Calculations of the neutron's spin rotation as well as polarized neutron reflectometry experiments on an ErFe{sub 2}/DyFe{sub 2} multilayer show the perfect performance of the used setup. The recently commissioned cryomagnet M5 with a maximum vertical field of up to 7.2 T in asymmetric mode for polarized neutrons and 9 T in symmetric mode for unpolarized neutrons was used on the C5 spectrometer in reflectometry mode, at the NRU reactor in Chalk River, Canada.

Fritzsche, H. [National Research Council Canada, Canadian Neutron Beam Centre, Chalk River Laboratories, Chalk River, Ontario K0J 1J0 (Canada)

2005-11-15

188

High-Resolution Studies of the Solar Polar Magnetic Fields  

NASA Astrophysics Data System (ADS)

We present high-resolution studies of the solar polar magnetic fields near sunspot maximum in 1989 and towards sunspot minimum in 1995. We show that, in 1989, the polar latitudes were covered by several unipolar regions of both polarities. In 1995, however, after the polar field reversal was complete, each pole exhibited only one dominant polarity region. Each unipolar region contains magnetic knots of both polarities but the number count of the knots of the dominant polarity exceeds that of the opposite polarity by a ratio of order 4:1, and it is rare to find opposite polarity pairs, i.e., magnetic bipoles. These knots have lifetimes greater than 7hours but less than 24hours. We interpret the longitudinal displacement of the knots over a 7-hour period as a measure of the local rotation rate. This rotation rate is found to be generally consistent with Snodgrass' (1983) magnetic rotation law. In an attempt to obtain some insight into the operation of the solar dynamo, sketches of postulated subsurface field configurations corresponding to the observed surface fields at these two epochs of the solar cycle are presented.

Varsik, J. R.; Wilson, P. R.; Li, Y.

1999-02-01

189

Relaxation of rotational angular momentum of polar diatomic molecules in simple liquids  

SciTech Connect

The relaxation processes of rotational angular momentum of polar diatomic molecules diluted in simple liquids are analyzed by applying a non-Markovian relaxation theory to the study of the binary time autocorrelation function of the angular momentum. This non-Markovian theory was previously applied to the study of the infrared and Raman spectroscopy, and also to the analysis of the rotational energy relaxation processes. We have obtained non-Markovian evolution equations for the two-time j-level angular momentum correlation components involved in the angular momentum correlation function. In these equations, the time-dependent angular momentum transfer rates and the pure orientational angular transfer rates are given in terms of the binary time autocorrelation function of the diatomic-solvent anisotropic interaction. The non-Markovian evolution equations converge to Markovian ones in the long time limit, reaching the angular momentum transfer rates in the usual time-independent form. Alternative time scales for the angular relaxation processes, relative to the individual rotational processes as well as to the global decay correlations, are introduced and analyzed. The theory is applied to the study of the angular momentum relaxation processes of HCl diluted in liquid SF{sub 6}, a system for which rotational energy relaxation and infrared and Raman spectroscopy was previously analyzed in the scope of the same theory.

Padilla, A.; Perez, J. [Departamento de Fisica Fundamental y Experimental, Electronica y Sistemas, Universidad de La Laguna, 38204 Tenerife (Spain)

2007-03-15

190

High Precision Polarization Strategy for the Qweak Experiment  

NASA Astrophysics Data System (ADS)

The Qweak experiment in Hall C at Jefferson Lab is measuring the weak charge of the proton to an uncertainty of 4.1% by scattering longitudinally polarized electrons from protons in a liquid hydrogen target. The electron beam polarization is budgeted as the largest experimental systematic uncertainty of 1.5%. Aiming for a polarization measurement to within 1%, two independent polarimeters monitored the beam polarization by measuring the asymmetry of the polarized electron beam scattering either via the Møller or Compton process. The Møller polarimeter detects the pair of electrons scattered from a highly polarized thin iron foil through two identical calorimeters. However, it was limited to running at much lower currents and measurements are invasive to the experiment. The Compton polarimeter was commissioned to remove this limitation by using a high powered Fabry-Pérot cavity laser to provide a polarized photon source. The use of Compton scattering allows for non-invasive measurements and the ability to run at the same currents as the main experiment. The Compton scattered photons and electrons are detected independently. I will discuss the polarimetry strategy and preliminary polarization results for the Qweak experiment using these three techniques.

Cornejo, Juan Carlos

2012-10-01

191

Connecting-layer-based polarizing beam splitter grating with high efficiency for both TE and TM polarizations  

NASA Astrophysics Data System (ADS)

We describe a novel polarizing beam splitter (PBS) of transmission connecting-layer-based grating, which can show high efficiency for TE polarization in the -1st order and TM polarization in the 0th order. According to the modal method, grating duty cycle and period are prescribed to obtain high efficiency for TM polarization. Using the rigorous coupled-wave analysis, grating depth and thickness of the connecting layer are optimized to achieve high efficiency for TE polarization. The presented PBS has advantages of wideband properties for incident wavelength and angle. Most importantly, the efficiency is improved greatly for TE polarization compared with the reported PBS based on fused-silica grating.

Wang, Bo; Lei, Liang; Chen, Li; Zhou, Jinyun

2012-10-01

192

Real dipolar moment associated with an ellipsoidal polar molecule and the static dielectric constant of mixtures of polar and non-polar liquids  

Microsoft Academic Search

We calculate, in condensed phase, the total dipole induced by a dipolar molecule on its environments. If the shape of the molecule can be assimilated to that of an ellipsoid, this average neighbourhood dipole does not vanish and is located between the ellipsoid and the smallest sphere in which the molecule can be contained. It is shown that, due to

G. Bossis

1982-01-01

193

Ionization of one- and three-dimensionally-oriented asymmetric-top molecules by intense circularly polarized femtosecond laser pulses  

SciTech Connect

We present a combined experimental and theoretical study on strong-field ionization of a three-dimensionally-oriented asymmetric top molecule, benzonitrile (C{sub 7}H{sub 5}N), by circularly polarized, nonresonant femtosecond laser pulses. Prior to the interaction with the strong field, the molecules are quantum-state selected using a deflector and three-dimensionally (3D) aligned and oriented adiabatically using an elliptically polarized laser pulse in combination with a static electric field. A characteristic splitting in the molecular frame photoelectron momentum distribution reveals the position of the nodal planes of the molecular orbitals from which ionization occurs. The experimental results are supported by a theoretical tunneling model that includes and quantifies the splitting in the momentum distribution. The focus of the present article is to understand strong-field ionization from 3D-oriented asymmetric top molecules, in particular the suppression of electron emission in nodal planes of molecular orbitals. In the preceding article [Dimitrovski et al., Phys. Rev. A 83, 023405 (2011)] the focus is to understand the strong-field ionization of one-dimensionally-oriented polar molecules, in particular asymmetries in the emission direction of the photoelectrons.

Hansen, Jonas L. [Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark); Holmegaard, Lotte; Kalhoej, Line; Kragh, Sofie Louise [Department of Chemistry, Aarhus University, DK-8000 Aarhus C (Denmark); Stapelfeldt, Henrik [Department of Chemistry, Aarhus University, DK-8000 Aarhus C (Denmark); Interdisciplinary Nanoscience Center (iNANO), Aarhus University, DK-8000 Aarhus C (Denmark); Filsinger, Frank; Meijer, Gerard; Kuepper, Jochen; Dimitrovski, Darko; Abu-samha, Mahmoud; Martiny, Christian Per Juul; Madsen, Lars Bojer [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, D-14195 Berlin (Germany); Lundbeck Foundation Theoretical Center for Quantum System Research, Department of Physics and Astronomy, Aarhus University, DK-8000 Aarhus C (Denmark)

2011-02-15

194

Spectroscopy, reaction, and photodissociation in highly vibrationally excited molecules  

SciTech Connect

Highly vibrationally excited molecules often control the course of chemical reactions in the atmosphere, combustion, plasmas, and many other environments. The research described in this Progress Report uses laser excitation and interrogation techniques to study and control the dynamics of highly vibrationally excited molecules. In particular, they show that it is possible to unravel the details and influence the course of photodissociation and bimolecular reaction. The experiments use laser excitation of overtone vibrations to prepare highly vibrationally excited molecules, frequently with single quantum state resolution, and laser spectroscopy to monitor the subsequent behavior of the excited molecule. We have studied the vibrationally mediated photodissociation and the bond- and state-selected bimolecular reaction of highly vibrationally excited molecules. In the first process, one photon creates a highly excited molecule, a second photon from another laser dissociates it, and light from a third laser detects the population of individual product quantum states. This approach allows us to explore otherwise inaccessible regions of the ground and excited state potential energy surface and, by exciting to the proper regions of the surface, to control the breaking of a selected chemical bond. In the second process, the highly vibrationally excited molecule reacts with an atom formed either in a microwave discharge or by photolysis and another laser interrogates the products. We have used this approach to demonstrate mode- and bond-selected bimolecular reactions in which the initial excitation controls the subsequent chemistry. 30 refs., 8 figs.

Not Available

1991-01-01

195

Highly polarized HLA class II antigen processing and presentation by human intestinal epithelial cells.  

PubMed Central

The high concentration of foreign antigen in the lumen of the gastrointestinal tract is separated from the underlying lymphocytes by a single cell layer of polarized epithelium. Intestinal epithelial cells can express HLA class II antigens and may function as antigen-presenting cells to CD4(+) T cells within the intestinal mucosa. Using tetanus toxoid specific and HLA-DR-restricted T lymphocytes, we show that polarized intestinal epithelial cells directed to express HLA-DR molecules are able to initiate class II processing only after internalization of antigen from their apical surface. Coexpression of the class II transactivator CIITA in these cells, which stimulates highly efficient class II processing without the characteristic decline in barrier function seen in polarized monolayers treated with the proinflammatory cytokine gamma-IFN, facilitates antigen processing from the basolateral surface. In both cases, peptide presentation to T cells via class II molecules was restricted to the basolateral surface. These data indicate a highly polarized functional architecture for antigen processing and presentation by intestinal epithelial cells, and suggest that the functional outcome of antigen processing by the intestinal epithelium is both dependent on the cellular surface at which the foreign antigen is internalized and by the underlying degree of mucosal inflammation.

Hershberg, R M; Cho, D H; Youakim, A; Bradley, M B; Lee, J S; Framson, P E; Nepom, G T

1998-01-01

196

High proton polarization in crystalline naphthalene by dynamic nuclear polarization with laser excitation at room temperature and liquid nitrogen temperature  

NASA Astrophysics Data System (ADS)

We have successfully polarized protons in naphthalene doped with pentacene at room temperature and liquid nitrogen temperature. Pentacene molecules have been excited with a laser beam and protons have been polarized dynamically in the triplet state of pentacene. We have obtained a polarization of about 13% at liquid nitrogen temperature in a field of about 3 kG with an N2 laser of about 150 mW. We expect to obtain a polarization higher than 30% with another type of laser.

Iinuma, M.; Shaké, I.; Takizawa, R.; Daigo, M.; Shimizu, H. M.; Takahashi, Y.; Masaike, A.; Yabuzaki, T.

1995-02-01

197

Effect of polar protic and polar aprotic solvents on negative-ion electrospray ionization and chromatographic separation of small acidic molecules.  

PubMed

A comprehensive study investigated the effect of polar protic (methanol and water) and polar aprotic (acetonitrile and acetone) solvents on the chromatographic separation and negative-ion electrospray (ESI) response of 49 diverse small, acidic molecules. Flow injection experiments on a triple quadrupole were used to measure the response in neat solvents after optimization of source conditions and implementation of a rigorous quality control program (the later ensured that changes in analyte response were due to the analyte/solvent measured and not changes in instrument performance over time). In all solvents, compounds with electron-withdrawing groups and extended conjugation ionized best due to resonance and inductive effects. Ionization was greatest in methanol or water for all compounds that elicited a response, thus revealing that enhanced sensitivity and lower limits of detection are achieved with polar protic solvents. Response in acetone was equal to or slightly lower than response in acetonitrile in flow injection experiments; however, the water/acetonitrile and water/acetone mobile phases produced the better chromatographic separation. Water/methanol produced slightly less satisfactory separation but the greatest overall response. This increase in response was attributed to the protic nature of methanol and the elution of compounds in a higher organic mobile phase composition (retention times were ?30% later in methanol). This work is intended to facilitate rational liquid chromatography/mass spectrometry method development for small molecule applications, including metabolomics. PMID:23066894

Huffman, Brian A; Poltash, Michael L; Hughey, Christine A

2012-11-02

198

Functional fixedness and functional reduction as common sense reasonings in chemical equilibrium and in geometry and polarity of molecules  

NASA Astrophysics Data System (ADS)

Many of the learning difficulties in the specific domain of chemistry are found not only in the ideas already possessed by students but in the strategic and procedural knowledge that is characteristic of everyday thinking. These defects in procedural knowledge have been described as functional fixedness and functional reduction. This article assesses the procedural difficulties of students (grade 12 and first and third year of university) based on common sense reasoning in two areas of chemistry: chemical equilibrium and geometry and polarity of molecules. In the first area, the theme of external factors affecting equilibria (temperature and concentration change) was selected because the explanations given by the students could be analyzed easily. The existence of a functional fixedness where Le Chatelier's principle was almost exclusively applied by rote could be observed, with this being the cause of the incorrect responses given to the proposed items. Functional fixedness of the Lewis structure also led to an incorrect prediction of molecular geometry. When molecular geometry was correctly determined by the students, it seemed that other methodological or procedural difficulties appeared when the task was to determine molecular polarity. The students showed a tendency, in many cases, to reduce the factors affecting molecular polarity in two possible ways: (a) assuming that polarity depends only on shape (geometric functional reduction) or (b) assuming that molecular polarity depends only on the polarity of bonds (bonding functional reduction).

Furió, C.; Calatayud, M. L.; Bárcenas, S. L.; Padilla, O. M.

2000-09-01

199

Single-molecule imaging at high hydrostatic pressure  

NASA Astrophysics Data System (ADS)

Direct microscopic fluorescence imaging of single molecules can provide a wealth of mechanistic information, but up to now, it has not been possible under high pressure conditions, due to limitations in microscope pressure cell design. We describe a pressure cell window design that makes it possible to image directly single molecules at high hydrostatic pressure. We demonstrate our design by imaging single molecules of Alexa Fluor 647 dye bound to DNA, at 120 and 210 bar, and following their fluorescence photodynamics. We further show that the failure pressure of this type of pressure cell window can be in excess of 1 kbar.

Vass, Hugh; Lucas Black, S.; Flors, Cristina; Lloyd, Diarmuid; Bruce Ward, F.; Allen, Rosalind J.

2013-04-01

200

Implementation of van der Waals Density Functional Approach to the Spin-Polarized System: Interaction Potential between Oxygen Molecules  

NASA Astrophysics Data System (ADS)

We propose a practical approach to spin-polarized systems within the van der Waals density functional (vdW-DF). The method was applied to a gas phase oxygen molecule and a parallel (H-type) pair of oxygen molecules. It was found that vdW-DF improves the equilibrium distance and binding energy. In particular, one type of vdW-DF can describe such systems reasonably well. The van der Waals interaction has been confirmed to have an energy comparable to the magnetic one, while emerging at a distance rather longer than the latter.

Obata, Masao; Nakamura, Makoto; Hamada, Ikutaro; Oda, Tatsuki

2013-09-01

201

Suppressed dependence of polarization on epitaxial strain in highly polar ferroelectrics  

SciTech Connect

A combined experimental and computational investigation of coupling between polarization and epitaxial strain in highly polar ferroelectric PbZr{sub 0.2}Ti{sub 0.8}O{sub 3} (PZT) thin films is reported. A comparison of the properties of relaxed (tetragonality c/a{approx}1.05) and highly strained (c/a{approx}1.09) epitaxial films shows that polarization, while being amongst the highest reported for PZT or PbTiO3 in either film or bulk forms Pr{approx}82{micro}C/cm{sup 2}, is almost independent of the epitaxial strain. We attribute this behavior to a suppressed sensitivity of the A-site cations to epitaxial strain in these Pb-based perovskites, where the ferroelectric displacements are already large, contrary to the case of less polar perovskites, such as BaTiO{sub 3}. In the latter case, the A-site cation (Ba) and equatorial oxygen displacements can lead to substantial polarization increases.

Lee, Ho Nyung [ORNL; Nakhmanson, Dr. Serge M. [Rutgers University; Chisholm, Matthew F [ORNL; Christen, Hans M [ORNL; Rabe, Karin M. [Rutgers University; Vandebilt, David [Rutgers University

2007-01-01

202

Suppressed dependence of polarization on epitaxial strain in highly polar ferroelectrics.  

SciTech Connect

A combined experimental and computational investigation of coupling between polarization and epitaxial strain in highly polar ferroelectric PbZr{sub 0.2}Ti{sub 0.8}O{sub 3} (PZT) thin films is reported. A comparison of the properties of relaxed (tetragonality c/a{approx}1.05) and highly strained (c/a{approx}1.09) epitaxial films shows that polarization, while being amongst the highest reported for PZT or PbTiO{sub 3} in either film or bulk forms (P{sub r}{approx}82 {mu}C/cm{sup 2}), is almost independent of the epitaxial strain. We attribute this behavior to a suppressed sensitivity of the A-site cations to epitaxial strain in these Pb-based perovskites, where the ferroelectric displacements are already large, contrary to the case of less polar perovskites, such as BaTiO{sub 3}. In the latter case, the A-site cation (Ba) and equatorial oxygen displacements can lead to substantial polarization increases.

Lee, H. N.; Nakhmanson, S. M.; Chisholm, M. F.; Christen, H. M.; Rabe, K. M.; Vanderbilt, D.; Materials Science Division; ORNL; Rutgers Univ.

2007-01-01

203

Polar vortex dynamics during spring and fall diagnosed using trace gas observations from the Atmospheric Trace Molecule Spectroscopy instrument  

Microsoft Academic Search

Trace gases measured by the Atmospheric Trace Molecule Spectroscopy (ATMOS) instrument during three Atmospheric Laboratory for Applications and Science (ATLAS) space-shuttle missions, in March\\/April 1992 (AT-1), April 1993 (AT-2), and November 1994 (AT-3) have been mapped into equivalent latitude\\/potential temperature (EqL\\/theta) coordinates. The asymmetry of the spring vortices results in coverage of subtropical to polar EqLs. EqL\\/theta fields of long-lived

G. L. Manney; H. A. Michelsen; M. L. Santee; M. R. Gunson; F. W. Irion; A. E. Roche; N. J. Livesey

1999-01-01

204

Exchange and polarization effect in high-order harmonic imaging of molecular structures  

SciTech Connect

We analyze the importance of exchange, polarization, and electron-electron correlation in high-order harmonic generation in molecules interacting with intense laser fields. We find that electron exchange can become particularly important for harmonic emission associated with intermediate excitations in the molecular ion. In particular, for orbitals associated with two-hole one-particle excitations, exchange effects can eliminate structure-related minima and maxima in the harmonic spectra. Laser-induced polarization of the neutral molecule may also have major effects on orbital structure-related minima and maxima in the harmonic spectra. Finally, we show how exchange terms in recombination can be viewed as a shakedownlike process induced by sudden electronic excitation in the ion.

Sukiasyan, Suren; Ivanov, Misha Yu. [Department of Physics, Imperial College London, South Kensington Campus, SW7 2AZ London (United Kingdom); Patchkovskii, Serguei [National Research Council, 100 Sussex Drive, Ottawa, Ontario K1A 0R6 (Canada); Smirnova, Olga [Max-Born Institute for Nonlinear Optics and Short Pulse Spectroscopy, Max-Born-Strasse 2A, D-12489 Berlin (Germany); Brabec, Thomas [Physics Department and Center for Research in Photonics, University of Ottawa, 150 Louis Pasteur, Ottawa, Ontario K1N 6N5 (Canada)

2010-10-15

205

Single DNA Molecule Patterning for High-Throughput Epigenetic Mapping  

PubMed Central

We present a method for profiling the 5-methyl cytosine distribution on single DNA molecules. Our method combines soft-lithography and molecular elongation to form ordered arrays of more than 250,000 individual DNA molecules immobilized on a solid substrate. The methylation state of the DNA is detected and mapped by binding of fluorescently labeled methyl-CpG binding domain peptides to the elongated dsDNA molecules and imaging of their distribution. The stretched molecules are fixed in their extended configuration by adsorption onto the substrate so analysis can be performed with high spatial resolution and signal averaging. We further prove this technique allows imaging of DNA molecules with different methylation states.

Cerf, Aline; Cipriany, Benjamin R.; Benitez, Jaime J.; Craighead, Harold G.

2013-01-01

206

Highly Parallel Translation of DNA Sequences into Small Molecules  

PubMed Central

A large body of in vitro evolution work establishes the utility of biopolymer libraries comprising 1010 to 1015 distinct molecules for the discovery of nanomolar-affinity ligands to proteins.[1], [2], [3], [4], [5] Small-molecule libraries of comparable complexity will likely provide nanomolar-affinity small-molecule ligands.[6], [7] Unlike biopolymers, small molecules can offer the advantages of cell permeability, low immunogenicity, metabolic stability, rapid diffusion and inexpensive mass production. It is thought that such desirable in vivo behavior is correlated with the physical properties of small molecules, specifically a limited number of hydrogen bond donors and acceptors, a defined range of hydrophobicity, and most importantly, molecular weights less than 500 Daltons.[8] Creating a collection of 1010 to 1015 small molecules that meet these criteria requires the use of hundreds to thousands of diversity elements per step in a combinatorial synthesis of three to five steps. With this goal in mind, we have reported a set of mesofluidic devices that enable DNA-programmed combinatorial chemistry in a highly parallel 384-well plate format. Here, we demonstrate that these devices can translate DNA genes encoding 384 diversity elements per coding position into corresponding small-molecule gene products. This robust and efficient procedure yields small molecule-DNA conjugates suitable for in vitro evolution experiments.

Weisinger, Rebecca M.; Wrenn, S. Jarrett; Harbury, Pehr B.

2012-01-01

207

Dispersion interactions with linear scaling DFT: a study of planar molecules on charged polar surfaces  

NASA Astrophysics Data System (ADS)

The placement of organic molecules such as CuPc (copper phthalocyanine) on wurtzite ZnO (zinc oxide) charged surfaces has been proposed as a way of creating photovoltaic solar cellsfootnotetextG.D. Sharma et al., Solar Energy Materials & Solar Cells 90, 933 (2006) ; optimising their performance may be aided by computational simulation. Electronic structure calculations provide high accuracy at modest computational cost but two challenges are encountered for such layered systems. First, the system size is at or beyond the limit of traditional cubic-scaling Density Functional Theory (DFT). Second, traditional exchange-correlation functionals do not account for van der Waals (vdW) interactions, crucial for determining the structure of weakly bonded systems. We present an implementation of recently developed approachesfootnotetextP.L. Silvestrelli, P.R.L. 100, 102 (2008) to include vdW in DFT within ONETEPfootnotetextC.-K. Skylaris, P.D. Haynes, A.A. Mostofi and M.C. Payne, J.C.P. 122, 084119 (2005) , a linear-scaling package for performing DFT calculations using a basis of localised functions. We have applied this methodology to simple planar organic molecules, such as benzene and pentacene, on ZnO surfaces.

Andrinopoulos, Lampros; Hine, Nicholas; Haynes, Peter; Mostofi, Arash

2010-03-01

208

Toward a 2-D magneto-optical trap for polar molecules  

NASA Astrophysics Data System (ADS)

The additional structure that arises from the rotational degree of freedom in diatomic molecules makes difficult the adaptation of a traditional atomic magneto-optical trap (MOT) for use with molecules. We describe progress toward development of a 2-D MOT for laser cooled yttrium monoxide molecules based on a resonant LC baseball coil geometry.

Hummon, Matthew; Stuhl, Benjamin; Yeo, Mark; Collopy, Alejandra; Ye, Jun

2012-06-01

209

Polarizing Agents and Mechanisms for High-Field Dynamic Nuclear Polarization of Frozen Dielectric Solids  

PubMed Central

This article provides an overview of polarizing mechanisms involved in high-frequency dynamic nuclear polarization (DNP) of frozen biological samples at temperatures maintained using liquid nitrogen, compatible with contemporary magic-angle spinning (MAS) nuclear magnetic resonance (NMR). Typical DNP experiments require unpaired electrons that are usually exogenous in samples via paramagnetic doping with polarizing agents. Thus, the resulting nuclear polarization mechanism depends on the electron and nuclear spin interactions induced by the paramagnetic species. The Overhauser Effect (OE) DNP, which relies on time-dependent spin-spin interactions, is excluded from our discussion due the lack of conducting electrons in frozen aqueous solutions containing biological entities. DNP of particular interest to us relies primarily on time-independent, spin interactions for significant electron-nucleus polarization transfer through mechanisms such as the Solid Effect (SE), the Cross Effect (CE) or Thermal Mixing (TM), involving one, two or multiple electron spins, respectively. Derived from monomeric radicals initially used in DNP experiments, bi- or multiple-radical polarizing agents facilitate CE/TM to generate significant NMR signal enhancements in dielectric solids at low temperatures (< 100 K). For example, large DNP enhancements (~300 times at 5 T) from a biologically compatible biradical, 1-(TEMPO-4-oxy)-3-(TEMPO-4-amino)propan-2-ol (TOTAPOL), have enabled high-resolution MAS NMR in sample systems existing in submicron domains or embedded in larger biomolecular complexes. The scope of this review is focused on recently developed DNP polarizing agents for high-field applications and leads up to future developments per the CE DNP mechanism. Because DNP experiments are feasible with a solid-state microwave source when performed at <20 K, nuclear polarization using lower microwave power (< 100 mW) is possible by forcing a high proportion of biradicals to fulfill the frequency matching condition of CE (two EPR frequencies separated by the NMR frequency) using the strategies involving hetero-radical moieties and/or molecular alignment. In addition, the combination of an excited triplet and a stable radical might provide alternative DNP mechanisms without the microwave requirement.

Hu, Kan-Nian

2011-01-01

210

Polarization control of a high power laser by adjoint feedback control  

Microsoft Academic Search

A novel technique of polarizing a high power laser with unstable resonator optics is described which places the polarizing elements in a low power feedback path external to the parent resonator structure. The technique has been used to polarize a high power industrial CO2 laser. Rejection ratios for the unwanted polarization can exceed 20 dB. The polarization vector can be

Paul R. Blaszuk; John A. Benda; James L. Forgham; Harold L. Cohen

1993-01-01

211

Strong nuclear ring currents and magnetic fields in pseudorotating OsH4 molecules induced by circularly polarized laser pulses.  

PubMed

We design a circularly polarized laser pulse in the infrared frequency and femtosecond time domains, for excitation of the OsH(4) molecule in its first excited pseudorotational state of the triply-degenerate bend. The OsH(4) molecule need not be pre-oriented. After excitation, the central nucleus Os carries out pseudorotation about the axis parallel to the direction of propagation of the laser pulse. This pseudorotation causes a strong electric ring current with a value I=1.53 e fs(-1). The mean value of the radius of the ring current is very small, R=0.0031 a(0), where a(0) is the Bohr radius. According to the Biot-Savart law (|B(R=0)| ~I/R)), this nuclear ring current induces the strongest magnetic field predicted so far in molecules, with a central peak absolute value |B(R=0)| =623 T. To monitor the effect, we propose an IR-pump-X-ray-probe versus an X-ray-probe-only experiment, at the K- and L-edges of X-ray ionization. The results are based on the general quantum theory of excitations of pseudorotations in tetrahedral molecules AB(4), driven by a circularly polarized laser pulse. PMID:22389250

Barth, Ingo; Bressler, Christian; Koseki, Shiro; Manz, Jörn

2012-03-02

212

Multiple electron capture processes between highly charged ions and molecules  

Microsoft Academic Search

We have determined the absolute cross sections for one electron capture and total electron capture between slow, highly charged ions and multi-electron molecule targets (H2, N2, CO, CO2, CH4) under single collision conditions. It is found that the cross sections increase as the charge of the projectile ions increases and as the ionization potential of the target molecules decreases, as

Kazumoto Hosaka; Hiroyuki Tawara; Ichihiro Yamada; Hiroyuki A. Sakaue; Franciszek Krok; Frederik J. Currell; Nobuyuki Nakamura; Shunsuke Ohtani; Hirofumi Watanabe; Atsunori Danjo; Masahiro Kimura; Atsushi Matsumoto; Makoto Sakurai; Masuhiro Yoshino

1997-01-01

213

Fusion with highly spin polarized HD and D sub 2  

SciTech Connect

During the course of this grant, we succeeded in overcoming essentially all of the obstacles on the route to carrying out ICF shots with polarized deuteron fuel in plastic target shells. ICF with polarized deuterons is expected to answer the question of survival of polarization in the high temperature plasma prior to fusion, as well as to give quantitative information on anisotropic particle emissions and possible suppression of particular fusion reactions. The techniques previously developed for high D polarization in large solid HD samples have been adapted to polystyrene target shells which are cooled conductively via very thin metal wire supports. An independent NMR experiment on a normal-D{sub 2}-filled glass target shell with 2 {mu}m copper-coated spider silk supports affirmed the thermal conduction adequacy by registering very low sample temperatures in the presence of the generation of considerable D{sub 2} conversion heat. In a permeation experiment employing very pure ortho-D{sub 2}, it was demonstrated that hydrogens diffuse into polystyrene shells at room temperature without molecular dissociation, a requirement for preservation of the composition of our HD samples used for polarization. An advanced version of the permeation apparatus was designed and constructed which permits preparation of target shells loaded with very high density HD or D{sub 2} fuels. That system includes provision for cryocondensation and cold-transfer either to the dilution refrigerator for polarization or to the OMEGA fusion chamber for ICF experiments with denser unpolarized fuel targets than were heretofore realizable in plastic target shells. a major effort resulted in improvements of cold-transfer inter-apparatus mating procedures which minimize the temperature rise of the target shells over that of the helium reservoir temperature. High D polarization in solid pure 0-D{sub 2} was shown to be retained into the liquid state after rapid melting.

Honig, A. (Syracuse Univ., NY (USA). Dept. of Physics); Kremens, R.; Skupsky, S. (Rochester Univ., NY (USA). Lab. for Laser Energetics)

1991-05-05

214

Stereoelectronic factors in the interaction with DNA of small aromatic molecules substituted with a short cationic chain: importance of the polarity of the aromatic system of the molecule.  

PubMed

We have performed a quantitative analysis of the interaction with DNA of several unfused aromatic compounds synthesized in our laboratory and substituted with one or two short cationic chains. These and similar literature compounds, for which DNA binding data are available, bind with DNA by partial intercalation of the aromatic system, groove interaction of the linker chain, and groove electrostatic interactions of the terminal cationic group. Several independent quantitative and qualitative approaches show consistently that the strength of the interaction of the aromatic unit of the molecule with DNA binding sites depends on the direction and magnitude of polarity of the aromatic system. The phenomenon is explained in terms of the greatest negative potential in the DNA grooves, a concept extensively elaborated by Pullman and Pullman [cf. Lavery, R. and Pullman, B. [(1985) J. Biomol. Struct. Dyn. 2, 1021-1032] and references therein]. Classical, fused-ring planar intercalators do not follow the polarity-DNA affinity correlation, presumably because the intercalative forces depend more strongly on polarizability than on polarity of the aromatic system. PMID:1384699

Strekowski, L; Mokrosz, J L; Wilson, W D; Mokrosz, M J; Strekowski, A

1992-11-10

215

How many molecular layers of polar solvent molecules control chemistry? The concept of compensating dipoles.  

PubMed

The extension of the solvent influence of the shell into the volume of a polar medium was examined by means of anti-collinear dipoles on the basis of the ET (30) solvent polarity scale (i.e., the molar energy of excitation of a pyridinium-N-phenolatebetaine dye; generally: ET =28?591?nm?kcal?mol(-1) /?max ) where no compensation effects were found. As a consequence, solvent polarity effects are concentrated to a very thin layer of a few thousand picometres around the solute where extensions into the bulk solvent become unimportant. A parallelism to the thin surface layer of water to the gas phase is discussed. PMID:23939588

Langhals, Heinz; Braun, Patricia; Dietl, Christian; Mayer, Peter

2013-08-12

216

Polar Worker Adaptability to Antarctic High Altitudes.  

National Technical Information Service (NTIS)

The examinations were carried out during the 27th Soviet Antarctic expedition. Baseline data were collected before the departure of the test subjects to the Antarctic Region. Prior to their ascent to the high mountain area they were divided into two group...

A. A. Aydaraliyev A. L. Maksimov T. B. Chernook

1988-01-01

217

Travelling wave deceleration of heavy polar molecules in weak-field seeking states  

NASA Astrophysics Data System (ADS)

Electrostatic forces can be used to decelerate neutral molecules via the Stark interaction. Most Stark decelerators to date use switched dc electric fields to manipulate light molecules in weak field seeking states. More massive molecules have smaller rotational constants and greater kinetic energies at a given velocity, and would require very long decelerators to bring them to rest. We have combined a new cryogenic source of YbF molecules, based on a pulsed solenoid valve cooled to 4K, with a 48cm long travelling wave Stark decelerator that is suitable for decelerating heavy molecules in weak-field seeking states. This decelerator uses continuously modulated sinusoidal electric fields to produce a series of moving 3-dimensional traps that can be continuously slowed to decelerate the molecules within them. We have decelerated YbF molecules from 300m/s to 276m/s. This implies that a 3 metre long decelerator could produce trapped YbF molecules at rest. In a different configuration, our source produces broader pulses of YbF molecules with speeds of 200m/s or less that could be brought to rest with a decelerator that is just 1 metre in length.

Hendricks, Richard; Bulleid, Nicholas; Skoff, Sarah; Segal, Daniel; Sauer, Ben; Tarbutt, Michael; Hinds, Edward; Meek, Samuel; Osterwalder, Andreas; Parsons, Maxwell; Santambrogio, Gabriele; Meijer, Gerard

2012-06-01

218

Direct observation of a highly spin-polarized organic spinterface at room temperature  

PubMed Central

Organic semiconductors constitute promising candidates toward large-scale electronic circuits that are entirely spintronics-driven. Toward this goal, tunneling magnetoresistance values above 300% at low temperature suggested the presence of highly spin-polarized device interfaces. However, such spinterfaces have not been observed directly, let alone at room temperature. Thanks to experiments and theory on the model spinterface between phthalocyanine molecules and a Co single crystal surface, we clearly evidence a highly efficient spinterface. Spin-polarised direct and inverse photoemission experiments reveal a high degree of spin polarisation at room temperature at this interface. We measured a magnetic moment on the molecule's nitrogen ? orbitals, which substantiates an ab-initio theoretical description of highly spin-polarised charge conduction across the interface due to differing spinterface formation mechanisms in each spin channel. We propose, through this example, a recipe to engineer simple organic-inorganic interfaces with remarkable spintronic properties that can endure well above room temperature.

Djeghloul, F.; Ibrahim, F.; Cantoni, M.; Bowen, M.; Joly, L.; Boukari, S.; Ohresser, P.; Bertran, F.; Le Fevre, P.; Thakur, P.; Scheurer, F.; Miyamachi, T.; Mattana, R.; Seneor, P.; Jaafar, A.; Rinaldi, C.; Javaid, S.; Arabski, J.; Kappler, J. -P; Wulfhekel, W.; Brookes, N. B.; Bertacco, R.; Taleb-Ibrahimi, A.; Alouani, M.; Beaurepaire, E.; Weber, W.

2013-01-01

219

Direct observation of a highly spin-polarized organic spinterface at room temperature.  

PubMed

Organic semiconductors constitute promising candidates toward large-scale electronic circuits that are entirely spintronics-driven. Toward this goal, tunneling magnetoresistance values above 300% at low temperature suggested the presence of highly spin-polarized device interfaces. However, such spinterfaces have not been observed directly, let alone at room temperature. Thanks to experiments and theory on the model spinterface between phthalocyanine molecules and a Co single crystal surface, we clearly evidence a highly efficient spinterface. Spin-polarised direct and inverse photoemission experiments reveal a high degree of spin polarisation at room temperature at this interface. We measured a magnetic moment on the molecule's nitrogen ? orbitals, which substantiates an ab-initio theoretical description of highly spin-polarised charge conduction across the interface due to differing spinterface formation mechanisms in each spin channel. We propose, through this example, a recipe to engineer simple organic-inorganic interfaces with remarkable spintronic properties that can endure well above room temperature. PMID:23412079

Djeghloul, F; Ibrahim, F; Cantoni, M; Bowen, M; Joly, L; Boukari, S; Ohresser, P; Bertran, F; Le Fèvre, P; Thakur, P; Scheurer, F; Miyamachi, T; Mattana, R; Seneor, P; Jaafar, A; Rinaldi, C; Javaid, S; Arabski, J; Kappler, J-P; Wulfhekel, W; Brookes, N B; Bertacco, R; Taleb-Ibrahimi, A; Alouani, M; Beaurepaire, E; Weber, W

2013-01-01

220

Correcting systematic errors in high-sensitivity deuteron polarization measurements  

NASA Astrophysics Data System (ADS)

This paper reports deuteron vector and tensor beam polarization measurements taken to investigate the systematic variations due to geometric beam misalignments and high data rates. The experiments used the In-Beam Polarimeter at the KVI-Groningen and the EDDA detector at the Cooler Synchrotron COSY at Jülich. By measuring with very high statistical precision, the contributions that are second-order in the systematic errors become apparent. By calibrating the sensitivity of the polarimeter to such errors, it becomes possible to obtain information from the raw count rate values on the size of the errors and to use this information to correct the polarization measurements. During the experiment, it was possible to demonstrate that corrections were satisfactory at the level of 10-5 for deliberately large errors. This may facilitate the real time observation of vector polarization changes smaller than 10-6 in a search for an electric dipole moment using a storage ring.

Brantjes, N. P. M.; Dzordzhadze, V.; Gebel, R.; Gonnella, F.; Gray, F. E.; van der Hoek, D. J.; Imig, A.; Kruithof, W. L.; Lazarus, D. M.; Lehrach, A.; Lorentz, B.; Messi, R.; Moricciani, D.; Morse, W. M.; Noid, G. A.; Onderwater, C. J. G.; Özben, C. S.; Prasuhn, D.; Levi Sandri, P.; Semertzidis, Y. K.; da Silva E Silva, M.; Stephenson, E. J.; Stockhorst, H.; Venanzoni, G.; Versolato, O. O.

2012-02-01

221

Hydrophobic bond energy of non-polar molecules: Application to ? -ionone and 11- cis retinal  

Microsoft Academic Search

A method for calculating the hydrophobic bond energy (HPE) of a nonpolar molecule at room temperature was presented by assuming that the whole HPE is the sum of HPE of each group or atom composing the molecule. This method was applied to ?-ionone and 11-cis retinal and those HPE's were found to be considerable. Some comparison of the present method

T. Kakitani; H. Kakitani; S. Yomosa

1980-01-01

222

Spin Polarization in High Density Quark Matter  

NASA Astrophysics Data System (ADS)

We investigate the occurrence of a ferromagnetic phase transition in high density hadronic matter (e.g., in the interior of a neutron star). This could be induced by a four-fermion interaction analogous to the one which is responsible for chiral symmetry breaking in the Nambu-Jona-Lasinio model, to which it is related through a Fierz transformation. Flavor SU(2) and flavor SU(3) quark matter are considered. A second-order phase transition is predicted at densities about 5 times the normal nuclear matter density. It is also found that in flavor SU(3) quark matter, a first-order transition from the so-called 2 flavor super-conducting phase to the ferromagnetic phase arises. The color-flavor-locked phase may be completely hidden by the FP.

Bohr, Henrik; Panda, Prafulla K.; Providência, Constança; da Providência, João

2013-04-01

223

Solvatochromic shifts of polar and non-polar molecules in ambient and supercritical water: a sequential quantum mechanics/molecular mechanics study including solute-solvent electron exchange-correlation.  

PubMed

Polar and non-polar solutes (acetone and benzene) dissolved in ambient water and supercritical water are investigated theoretically using a sequential quantum mechanics (QM)/molecular mechanics (MM) method which combines classical molecular dynamics simulations and QM/MM calculations. From the detailed analysis of the dependence of the QM region size and point charge background region size as well as the different functionals, it is found that the inclusion of the solvent molecules within the first solvation shell into the QM region to account for the exchange-correlation between a solute and neighboring solvent molecules is important for the highly accurate spectral shift calculations, especially vital for the non-polar solutes whose interactions with the solvents are dominated by the quantum dispersions. At the same time, sufficiently large surrounding partial charge region (r(cutoff) ?15 A?) as well as the functional corrections to describe the long-range dispersion-corrections are also essential for the study of the electronic excited states in condensed phase. Our calculated solvatochromic shift values and their density dependencies at ambient and high temperature conditions are found to be in good agreements with experimental observations. This indicates that sound theoretical studies of solvatochromic shift can be achieved provided that a reasonable computational scheme with sufficiently large N(water) (QM) and r(cutoff) values is implemented. We also find both of aqueous acetone and aqueous benzene under high temperatures present three distinctive regions: low-density gas-like region, supercritical region, and high-density liquid-like region. The plateau behavior of solvatochromic shift in the supercritical region can be ascribed to the solvent clustering around the solute, which is a fundamental phenomenon of supercritical fluids (SCFs). The density dependence of our calculated coordination number of the first solvation shell nicely reproduces the trend of spectral shift and verifies the solvent clustering phenomenon of SCFs and its relationship with SCF's physicochemical properties. PMID:23231248

Ma, Haibo; Ma, Yingjin

2012-12-01

224

Solvatochromic shifts of polar and non-polar molecules in ambient and supercritical water: A sequential quantum mechanics/molecular mechanics study including solute-solvent electron exchange-correlation  

NASA Astrophysics Data System (ADS)

Polar and non-polar solutes (acetone and benzene) dissolved in ambient water and supercritical water are investigated theoretically using a sequential quantum mechanics (QM)/molecular mechanics (MM) method which combines classical molecular dynamics simulations and QM/MM calculations. From the detailed analysis of the dependence of the QM region size and point charge background region size as well as the different functionals, it is found that the inclusion of the solvent molecules within the first solvation shell into the QM region to account for the exchange-correlation between a solute and neighboring solvent molecules is important for the highly accurate spectral shift calculations, especially vital for the non-polar solutes whose interactions with the solvents are dominated by the quantum dispersions. At the same time, sufficiently large surrounding partial charge region (rcutoff >=15 A?) as well as the functional corrections to describe the long-range dispersion-corrections are also essential for the study of the electronic excited states in condensed phase. Our calculated solvatochromic shift values and their density dependencies at ambient and high temperature conditions are found to be in good agreements with experimental observations. This indicates that sound theoretical studies of solvatochromic shift can be achieved provided that a reasonable computational scheme with sufficiently large NwaterQM and rcutoff values is implemented. We also find both of aqueous acetone and aqueous benzene under high temperatures present three distinctive regions: low-density gas-like region, supercritical region, and high-density liquid-like region. The plateau behavior of solvatochromic shift in the supercritical region can be ascribed to the solvent clustering around the solute, which is a fundamental phenomenon of supercritical fluids (SCFs). The density dependence of our calculated coordination number of the first solvation shell nicely reproduces the trend of spectral shift and verifies the solvent clustering phenomenon of SCFs and its relationship with SCF's physicochemical properties.

Ma, Haibo; Ma, Yingjin

2012-12-01

225

Control of the high harmonic generation spectra by changing the molecule-laser field relative orientation  

SciTech Connect

The time dependent Schroedinger equation of a homonuclear diatomic molecule in the presence of a linearly polarized laser field is numerically solved by means of a split-operator parallel code. The calculations are carried out by assuming a single active electron model with fixed nuclei; a simplified two-dimensional model of the system is used. The highly nonlinear response of the electron wave function to the laser electric field stimulates the molecule to emit electromagnetic radiation consisting of a wide plateau of odd harmonics of the laser field. It is shown that the emitted spectrum can be finely controlled by changing the angle between the laser electric field and the molecular axis; this can be used to achieve a tunable source of high frequency radiation.

Daniele, Rosalba; Castiglia, Giuseppe; Corso, Pietro Paolo; Orlando, Gianfranco; Fiordilino, Emilio [Dipartimento di Scienze Fisiche e Astronomiche, Universita degli Studi di Palermo, Via Archirafi 36, 90123 Palermo (Italy); Morales, Francesca [Dipartimento di Fisica e Tecnologie Relative, Universita degli Studi di Palermo, Viale delle Scienze, 90128 Palermo (Italy)

2010-04-15

226

Role of orbital symmetry in high-order harmonic generation from aligned molecules  

SciTech Connect

High-order harmonic generation has been explored theoretically and experimentally in CO{sub 2}, a linear molecule characterized by doubly antisymmetric highest-occupied molecular orbitals. For the first time to our knowledge, the high-harmonic yield is studied as a function of the angle between the molecular axis and the polarization direction. A minimum yield is found at 0 deg. for all harmonics, which constitutes evidence for destructively interfering terms in the ionization probability amplitude playing an important role in strong-field phenomena in molecules. The maximum yield is always found at intermediate angles, but the detailed behavior is harmonic specific. Numerical simulations reproduce the main features observed in the experiment.

Nalda, R. de; Heesel, E.; Hay, N.; Springate, E.; Marangos, J.P. [Blackett Laboratory, Imperial College London, Prince Consort Road, London SW7 2BW (United Kingdom); Lein, M. [Max Planck Institute for the Physics of Complex Systems, Noethnitzer Strasse 38, 01187 Dresden (Germany); Velotta, R. [Istituto Nazionale Fisica della Materia, Dipartimento Scienze Fisiche, Via Cintia 26, 80126 Naples (Italy); Castillejo, M. [Instituto de Quimica-Fisica Rocasolano, Serrano 119, 28006 Madrid (Spain)

2004-03-01

227

Endless Polarization Stabilizer for High Bit-rate Polarization-Division Multiplexed Optical Systems  

Microsoft Academic Search

An endless polarization stabilization method is applied to a 40-Gbit\\/s RZ-DQPSK polarization-division multiplexed optical system. The effectivness of the polarization stabilizer in allowing the polarization demultiplexing of the two orthogonally polarized channels is experimentally verified.

Paolo Martelli; Pierpaolo Boffi; Maddalena Ferrario; Lucia Marazzi; Paola Parolari; Silvia M. Pietralunga; Aldo Righetti; Rocco Siano; Matteo Torregiani; Mario Martinelli

2008-01-01

228

Tensor polarization of the varphi meson photoproduced at high t  

Microsoft Academic Search

As part of a measurement [E. Anciant et al., Phys. Rev. Lett. 85, 4682 (2000)] of the cross section of varphi meson photoproduction to high momentum transfer, we measured the polar angular decay distribution of the outgoing K+ in the channel varphi--> K+ K- in the varphi center-of-mass frame (the helicity frame). We find that s -channel helicity conservation (SCHC)

K. McCormick; G. Audit; J. M. Laget; G. Adams; P. Ambrozewicz; E. Anciant; M. Anghinolfi; B. Asavapibhop; T. Auger; H. Avakian; H. Bagdasaryan; J. P. Ball; S. Barrow; M. Battaglieri; K. Beard; M. Bektasoglu; M. Bellis; N. Benmouna; B. L. Berman; N. Bianchi; A. S. Biselli; S. Boiarinov; B. E. Bonner; S. Bouchigny; R. Bradford; W. K. Brooks; V. D. Burkert; C. Butuceanu; J. R. Calarco; D. S. Carman; B. Carnahan; C. Cetina; S. Chen; P. L. Cole; A. Coleman; J. Connelly; D. Cords; P. Corvisiero; D. Crabb; H. Crannell; J. P. Cummings; E. de Sanctis; R. Devita; P. V. Degtyarenko; H. Denizli; L. Dennis; K. V. Dharmawardane; C. Djalali; G. E. Dodge; D. Doughty; P. Dragovitsch; M. Dugger; S. Dytman; O. P. Dzyubak; M. Eckhause; H. Egiyan; K. S. Egiyan; L. Elouadrhiri; P. Eugenio; L. Farhi; R. J. Feuerbach; J. Ficenec; T. A. Forest; V. Frolov; H. Funsten; S. J. Gaff; M. Gai; M. Garçon; G. Gavalian; S. Gilad; G. P. Gilfoyle; K. L. Giovanetti; P. Girard; C. I. Gordon; K. Griffioen; M. Guidal; M. Guillo; L. Guo; V. Gyurjyan; C. Hadjidakis; R. S. Hakobyan; D. Hancock; J. Hardie; D. Heddle; F. W. Hersman; K. Hicks; R. S. Hicks; M. Holtrop; C. E. Hyde-Wright; M. M. Ito; D. Jenkins; K. Joo; H. G. Juengst; J. H. Kelley; M. Khandaker; W. Kim; A. Klein; F. J. Klein; A. Klimenko; M. Klusman; M. Kossov; L. H. Kramer; Y. Kuang; S. E. Kuhn; J. Kuhn; J. Lachniet; J. Langheinrich; D. Lawrence; Ji Li; K. Lukashin; W. Major; J. J. Manak; C. Marchand; S. McAleer; J. W. McNabb; B. A. Mecking; S. Mehrabyan; J. J. Melone; M. D. Mestayer; C. A. Meyer; R. Minehart; M. Mirazita; R. Miskimen; L. Morand; S. A. Morrow; V. Muccifora; J. Mueller; G. S. Mutchler; J. Napolitano; R. Nasseripour; S. O. Nelson; S. Niccolai; G. Niculescu; I. Niculescu; B. B. Niczyporuk; R. A. Niyazov; M. Nozar; M. Osipenko; E. Pasyuk; G. Peterson; S. A. Philips; N. Pivnyuk; D. Pocanic; O. Pogorelko; E. Polli; B. M. Preedom; J. W. Price; Y. Prok; D. Protopopescu; L. M. Qin; B. A. Raue; G. Riccardi; G. Ricco; M. Ripani; B. G. Ritchie; F. Ronchetti; P. Rossi; D. Rowntree; P. D. Rubin; F. Sabatié; K. Sabourov; C. Salgado; J. P. Santoro; M. Sanzone-Arenhovel; V. Sapunenko; M. Sargsyan; R. A. Schumacher; V. S. Serov; A. Shafi; Y. G. Sharabian; J. Shaw; A. V. Skabelin; E. S. Smith; T. Smith; L. C. Smith; D. I. Sober; M. Spraker; S. Stepanyan; P. Stoler; S. Strauch; M. Taiuti; S. Taylor; D. J. Tedeschi; U. Thoma; R. Thompson; L. Todor; C. Tur; M. Ungaro; M. F. Vineyard; A. V. Vlassov; K. Wang; L. B. Weinstein; H. Weller; D. P. Weygand; C. S. Whisnant; M. Witkowski; E. Wolin; M. H. Wood; A. Yegneswaran; J. Yun; J. Zhao; Z. Zhou

2004-01-01

229

Polarization-induced pairing in high-temperature superconductivity  

SciTech Connect

We propose a mechanism for the pairing of electrons at the copper sites on the spin of quasi-one-dimensional Cu-O chains induced by the electronic polarization of the oxygen atoms in the side chains. We use a model Hamiltonian for a cluster of Cu-O chains and calculate the various correlation functions for a wide range of parameters. We examine the conditions for the onset of polarization-induced pairing states. Our results may be relevant to high-T/sub c/ superconductor YBa/sub 2/Cu/sub 3/O/sub 7-//sub x/. .AE

Callaway, J.; Kanhere, D.G.; Misra, P.K.

1987-11-01

230

Influences of DMI on spin-polarized current through a single-molecule magnet  

NASA Astrophysics Data System (ADS)

We theoretically investigate the influences of the Dzyaloshinskii-Moriya interaction (DMI) on the spin-polarized transport through a single-molecular magnets, which is weakly coupled to ferromagnetic lead-L(pL) and nonmagnetic lead-R. The spin current is obtained by means of the rate-equation approach in the sequential-tunneling region. Due to the coherent superposition of the molecular state |1 induced by the DMI, we can observe the continuous pure spin current and negative differential conductance (NDC) under the full polarization pL=1 condition and polarization reversal of spin-current in the case of 0

Luo, Bo; Liu, Juan; Yao, Kai-Lun

2013-11-01

231

A Pair Polarimeter for Linearly Polarized High Energy Photons  

SciTech Connect

Electron-positron pair production, the main process for high energy photon interaction with matter, has a large analyzing power for linear polarized photons. Our calculations show that in the GeV energy range a compact polarimeter based on silicon micro-strip detectors is feasible. We calculated the cross section as a function of the angle between the polarization plane and the line between positron and electron positions in the detector. For a thin radiator and equal energies of the positron and electron, the ratio sigma{parallel}/sigma{perpendicular} is about 1.6. At a beam intensity of 10{sup 6} photons per second a polarization measurement with a 1% statistical accuracy will require less than one hour of data taking.

Bogdan Wojtsekhowski; D. Tedeschi; B. Vlahovic

2002-10-01

232

High-order-harmonic generation in homonuclear and heteronuclear diatomic molecules: Exploration of multiple orbital contributions  

SciTech Connect

We present a time-dependent density functional theory (TDDFT) approach with proper asymptotic long-range potential for nonperturbative treatment of high-order harmonic generation (HHG) of diatomic molecules with their molecular axis parallel to the laser field polarization. A time-dependent two-center generalized pseudospectral method in prolate spheroidal coordinate system is used for accurate and efficient treatment of the TDDFT equations in space and time. The theory is applied to a detailed all-electron nonperturbative investigation of HHG processes of homonuclear (N{sub 2} and F{sub 2}) and heteronuclear (CO, BF, and HF) molecules in intense ultrashort laser pulses with the emphasis on the role of multiple molecular orbitals (MOs). The results reveal intriguing and substantially different nonlinear optical response behaviors for homonuclear and heteronuclear molecules. In particular, we found that the HHG spectrum for homonuclear molecules features a destructive interference of MO contributions while heteronuclear molecules show mostly constructive interference of orbital contributions.

Heslar, John [Center for Quantum Science and Engineering, Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Telnov, Dmitry [Department of Physics, St. Petersburg State University, 198504 St. Petersburg (Russian Federation); Chu, Shih-I [Center for Quantum Science and Engineering, Department of Physics, National Taiwan University, Taipei 10617, Taiwan (China); Department of Chemistry, University of Kansas, Lawrence, Kansas 66045 (United States)

2011-04-15

233

Generation of macroscopic entangled coherent states for distant ensembles of polar molecules via effective coupling to a superconducting charge qubit  

NASA Astrophysics Data System (ADS)

We propose a potentially practical scheme for creating macroscopic entangled coherent states (ECSs) between two distant ensembles of polar molecules (PMs) placed, respectively, in separate transmission-line resonators (TLRs) interconnected by a superconducting charge qubit. The ECS between two PM ensembles can be generated in the dispersive regime through control of the superconducting qubit under classical strong-driving conditions, during which the TLRs are only virtually excited. The tunable coupling of the TLR hybrid system provides us the potential of extending the ECS generation to multimode cases. The experimental feasibility of the scheme is discussed briefly based on currently available techniques.

Chen, Qiong; Yang, Wanli; Feng, Mang

2012-10-01

234

Signatures of the molecular potential in the ellipticity of high-order harmonics from aligned molecules  

NASA Astrophysics Data System (ADS)

We explore the information content of the polarization of high-order harmonics emitted from aligned molecules driven by a linearly polarized field. The study builds upon our previous work [Ramakrishna , Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.81.021802 81, 021802(R) (2010)], which illustrated that the phase of the continuum electronic wave function, and hence the underlying molecular potential, is responsible, at least in part, for the ellipticity observed in harmonic spectra. We use a simple model potential and systematically vary the potential parameters to investigate the sense in which, and the degree to which, the shape of the molecular potential is imprinted onto the polarization of the emitted harmonics. Strong ellipticity is observed over a wide range of potential parameters, suggesting that the emission of elliptically polarized harmonics is a general phenomenon, yet qualitatively determined by the molecular properties. The sensitivity of the ellipticity to the model parameters invites the use of ellipticity measurements as a probe of the continuum wave function and the underlying molecular potential.

Sherratt, Paul A. J.; Ramakrishna, S.; Seideman, Tamar

2011-05-01

235

High throughput single molecule detection for monitoring biochemical reactions  

PubMed Central

The design, performance and application of a novel optical system for high throughput single molecule detection (SMD) configured in a continuous flow format using microfluidics is reported. The system consisted of a microfabricated polymer-based multi-channel fluidic network situated within the optical path of a laser source (?ex = 660 nm) with photon transduction accomplished using an electron-multiplying charge coupled device (EMCCD) operated in a frame transfer mode that allowed tracking single molecules as they passed through a large field-of-view (FoV) illumination zone. The microfluidic device consisted of 30 microchannels possessing dimensions of 30 ?m (width) × 20 ?m (depth) with a 25 mm pitch. Individual molecules were electrokinetically driven through the fluidic network and excited within the wide-field illumination area with the resulting fluorescence collected via an objective and imaged onto the EMCCD camera. The detection system demonstrated sufficient sensitivity to detect single DNA molecules labeled with a fluorescent tag (AlexaFluor 660) identified through their characteristic emission wavelength and the burst of photons produced during their transit through the excitation volume. In its present configuration and fluidic architecture, the sample processing throughput was ?4.02 × 105 molecules s?1, but could be increased dramatically through the use of narrower channels and a smaller pitch. The system was further evaluated using a single molecule-based fluorescence quenching assay for measuring the population differences between duplexed and single-stranded DNA molecules as a function of temperature for determining the duplex melting temperature, Tm.

Okagbare, Paul I.; Soper, Steven A.

2009-01-01

236

Electron exchange between a dipole-bound anion and a polar molecule and dimer formation in dipole-bound anions  

NASA Astrophysics Data System (ADS)

We consider collision between a dipole-bound molecular anion and a neutral polar molecule and show that the excess electron can bind two neutral molecules into a dimer. Using a variational approach similar to the Heitler-London model of H2+ ion, we obtain the energy terms of such a dimer. Their difference determines the cross section of electron transfer from the anion to the neutral molecule in quasiclassical near-resonant Born-Oppenheimer approximation. We obtain for the cross section an analytical expression containing the weak (logarithmic) factor depending on the molecular dipole moment and the collision velocity. With the prelogarithmic factor proportional to inverse binding energy of the electron in the molecular anion, such weak dependence on the collision velocity is somewhat similar to the expressions appearing in the hard-sphere collision model. However the large logarithmic factor connected with long-range dipole-dipole interaction between the colliding molecules contradict to the hard-sphere approximation even for qualitative description of the charge transfer. Our analytical calculations are in a good accordance with the results of a recent experiment [Y. Liu, M. Cannon, L. Suess, F. B. Dunning, V. E. Chernov, and B. A. Zon, Chem. Phys. Lett. 433, 1 (2006)].

Chernov, V. E.; Danilyan, A. V.; Zon, B. A.

2009-08-01

237

Orientation analysis of uniaxially drawn polystyrene films doped with fluorescent molecules by fluorescence polarization, UV-and IR-dichroism and birefringence  

Microsoft Academic Search

Atactic polystyrene (PS) is doped in solution with various fluorescent molecules and cast to films. Rectangular samples, cut from these films, are uniaxially drawn at 100 °C and 110 °C. The orientation of the fluorescent probes is characterized by UV-dichroism and fluorescence polarization, that of the polymer segments by IR-dichroism and birefringence. It is observed that the fluorescent molecules depending

R. Neuert; H. Springer; G. Hinrichsen

1985-01-01

238

Quantitative polarized Raman spectroscopy in highly turbid bone tissue  

NASA Astrophysics Data System (ADS)

Polarized Raman spectroscopy allows measurement of molecular orientation and composition and is widely used in the study of polymer systems. Here, we extend the technique to the extraction of quantitative orientation information from bone tissue, which is optically thick and highly turbid. We discuss multiple scattering effects in tissue and show that repeated measurements using a series of objectives of differing numerical apertures can be employed to assess the contributions of sample turbidity and depth of field on polarized Raman measurements. A high numerical aperture objective minimizes the systematic errors introduced by multiple scattering. We test and validate the use of polarized Raman spectroscopy using wild-type and genetically modified (oim/oim model of osteogenesis imperfecta) murine bones. Mineral orientation distribution functions show that mineral crystallites are not as well aligned (p<0.05) in oim/oim bones (28+/-3 deg) compared to wild-type bones (22+/-3 deg), in agreement with small-angle X-ray scattering results. In wild-type mice, backbone carbonyl orientation is 76+/-2 deg and in oim/oim mice, it is 72+/-4 deg (p>0.05). We provide evidence that simultaneous quantitative measurements of mineral and collagen orientations on intact bone specimens are possible using polarized Raman spectroscopy.

Raghavan, Mekhala; Sahar, Nadder D.; Wilson, Robert H.; Mycek, Mary-Ann; Pleshko, Nancy; Kohn, David H.; Morris, Michael D.

2010-05-01

239

Strong Circularly Polarized Luminescence from Highly Emissive Terbium Complexes in Aqueous Solution  

SciTech Connect

Two luminescent terbium(III) complexes have been prepared from chiral ligands containing 2-hydroxyisophthalamide (IAM) antenna chromophores and their non-polarized and circularly-polarized luminescence properties have been studied. These tetradentate ligands, which form 2:1 ligand/Tb{sup III} complexes, utilize diaminocyclohexane (cyLI) and diphenylethylenediamine (dpenLI) backbones, which we reasoned would impart conformational rigidity and result in Tb{sup III} complexes that display both large luminescence quantum yield ({phi}) values and strong circularly polarized luminescence (CPL) activities. Both Tb{sup III} complexes are highly emissive, with {phi} values of 0.32 (dpenLI-Tb) and 0.60 (cyLI-Tb). Luminescence lifetime measurements in H{sub 2}O and D{sub 2}O indicate that while cyLI-Tb exists as a single species in solution, dpenLI-Tb exists as two species: a monohydrate complex with one H{sub 2}O molecule directly bound to the Tb{sup III} ion and a complex with no water molecules in the inner coordination sphere. Both cyLI-Tb and dpenLI-Tb display increased CPL activity compared to previously reported Tb{sup III} complexes made with chiral IAM ligands. The CPL measurements also provide additional confirmation of the presence of a single emissive species in solution in the case of cyLI-Tb, and multiple emissive species in the case of dpenLI-Tb.

Samuel, Amanda; Lunkley, Jamie; Muller, Gilles; Raymond, Kenneth

2010-03-15

240

A high-power high-gain single-polarization EDFA  

Microsoft Academic Search

Summary form only given. High power erbium doped fiber amplifiers (EDFAs) are key elements in both fiber optic distribution networks and free-space communications. Single-polarization EDFAs provide additional capabilities for polarization diplexing and improved communication performance since orthogonally polarized amplified spontaneous emission (ASE) can be eliminated at both receiver and transmitter. Such features can offer substantial benefit in free-space links where

D. O. Caplan; F. Hakimi

2000-01-01

241

Collective phenomena in a quasi-two-dimensional system of fermionic polar molecules: Band renormalization and excitons  

SciTech Connect

We theoretically analyze a quasi-two-dimensional system of fermionic polar molecules trapped in a harmonic transverse confining potential. The renormalized energy bands are calculated by solving the Hartree-Fock equation numerically for various trap and dipolar interaction strengths. The intersubband excitations of the system are studied in the conserving time-dependent Hartree-Fock (TDHF) approximation from the perspective of lattice modulation spectroscopy experiments. We find that the excitation spectrum consists of both intersubband particle-hole excitation continua and antibound excitons whose antibinding behavior is associated to the anisotropic nature of dipolar interactions. The excitonic modes are shown to capture the majority of the spectral weight. We evaluate the intersubband transition rates in order to investigate the nature of the excitonic modes and find that they are antibound states formed from particle-hole excitations arising from several subbands. We discuss the sum rules in the context of lattice modulation spectroscopy experiments and utilize them to check the consistency of the obtained results. Our results indicate that the excitonic effects persist for interaction strengths and temperatures accessible in the current experiments with polar molecules.

Babadi, Mehrtash; Demler, Eugene [Physics Department, Harvard University, Cambridge, Massachusetts 02138 (United States)

2011-09-15

242

Starch granules as a probe for the polarization at the sample plane of a high resolution multiphoton microscope  

NASA Astrophysics Data System (ADS)

Because of its polarization sensitivity, SHG microscopy can provide information about the orientation and degree of structural organization inside biological samples. To fully exploit the above potential, the state of the polarization at the sample plane needs to be known. In this work we present starch granules as a reliable probe for the polarization state of the excitation beam at the sample plane of a high resolution multiphoton microscope. Polarization dependent SHG series of images demonstrated the radial distribution of SHG active molecules inside starch granules. This allowed the granule to exhibit symmetrical SHG emission regions. The pattern rotates along with the rotation of a ?/2 waveplate and thus, can demonstrate the polarization at the sample plane. Maximum signal in the forward detected geometry appears when imaging starch granules exactly at the hemisphere plane. Symmetric SHG regions rotating with the incoming linear polarization were also recorded in the backward detected geometry. A portion of the backwards detected SHG signal, which corresponds to two rotating equator arcs, does not overlap with the forward SHG signal. Importantly, polarization measurements, performed either in the forward or the backwards directions, have demonstrated the suitability and flexibility of this technique for both detection schemes. As result, observation of the starch signal allowed us to know the polarization of our SHG microscope. Furthermore, by coding this information in an angular representation, we corrected the input values in a theoretical model that predicts the average orientation of SHG active molecules. This has allowed us to map the mean orientation of SHG active molecules in body walls muscle of Caenorhabditis elegans, with pixel resolution.

Psilodimitrakopoulos, Sotiris; Amat-Roldán, Ivan; Santos, Susana; Mathew, Manoj; Thayil K. N., Anisha; Zalvidea, Dobryna; Artigas, David; Loza-Alvarez, Pablo

2008-03-01

243

High harmonic spectroscopy of the Cooper minimum in molecules.  

PubMed

The Cooper minimum (CM) has been studied using high harmonic generation solely in atoms. Here, we present detailed experimental and theoretical studies on the CM in molecules probed by high harmonic generation using a range of near-infrared light pulses from ?=1.3 to 1.8 ?m. We demonstrate the CM to occur in CS(2) and CCl(4) at ~42 and ~40 eV, respectively, by comparing the high harmonic spectra with the known partial photoionization cross sections of different molecular orbitals, confirmed by theoretical calculations of harmonic spectra. We use CM to probe electron localization in Cl-containing molecules (CCl(4), CH(2)Cl(2), and trans-C(2)H(2)Cl(2)) and show that the position of the minimum is influenced by the molecular environment. PMID:23373923

Wong, M C H; Le, A-T; Alharbi, A F; Boguslavskiy, A E; Lucchese, R R; Brichta, J-P; Lin, C D; Bhardwaj, V R

2013-01-18

244

Students' Use of Three Different Visual Representations to Interpret Whether Molecules Are Polar or Nonpolar  

ERIC Educational Resources Information Center

|Visualizing molecular properties is often crucial for constructing conceptual understanding in chemistry. However, research has revealed numerous challenges surrounding students' meaningful interpretation of the relationship between the geometry and electrostatic properties of molecules. This study explored students' (n = 18) use of three visual…

Host, Gunnar E.; Schonborn, Konrad J.; Palmerius, Karljohan E. Lundin

2012-01-01

245

Dielectric Method of Determination of the Association Energy Between Polar Molecules in Nematic Liquid Crystal  

Microsoft Academic Search

Effective values of the parallel and perpendicular components of the molecular dipole moment per one molecule have been calculated for the 5CB compound, from the values of the parallel and perpendicular components of the dielectric permittivity tensor, using Maier and Meier equations. Necessary molecular parameters, such as transverse and longitudinal polarizabilities, as well as temperature dependence of nematic order parameter

Z. Raszewski; J. Rutkowska; J. K?dzierski; J. Zieli?ski; P. Perkowski; W. Piecek; J. Zmija

1994-01-01

246

Displacement of protein-bound aptamers with small molecules screened by fluorescence polarization  

Microsoft Academic Search

Small molecule inhibitors of proteins are invaluable tools in research and as starting points for drug development. However, their screening can be tedious, as most screening methods have to be tailored to the corresponding drug target. Here, we describe a detailed protocol for a modular and generally applicable assay for the identification of small organic compounds that displace an aptamer

Markus Hafner; Elena Vianini; Barbara Albertoni; Laura Marchetti; Imke Grüne; Christian Gloeckner; Michael Famulok

2008-01-01

247

Incorporated oriented polar molecules in PMMA polymeric films: characterization by Kelvin probe technique and atomic force microscopy  

Microsoft Academic Search

Betaine type dipolar molecules have received considerable attention because of their large dipole moments and optical non-linearities. The host-guest systems are chosen. The high-electric field corona poling was used to generate dipole orientation of betaine molecules in polymer matrices. Atomic force microscopy and surface potential studies yield useful information regarding both structural and electronic properties of casted host-guest polymer films.

I. Muzikante; D. Cepite; E. Fonavs; A. Tokmakov; D. Erts; B. Polakov

2002-01-01

248

High-fidelity linear optical quantum computing with polarization encoding  

SciTech Connect

We show that the KLM scheme [Knill, Laflamme, and Milburn, Nature 409, 46 (2001)] can be implemented using polarization encoding, thus reducing the number of path modes required by half. One of the main advantages of this new implementation is that it naturally incorporates a loss detection mechanism that makes the probability of a gate introducing a non-detected error, when non-ideal detectors are considered, dependent only on the detector dark-count rate and independent of its efficiency. Since very low dark-count rate detectors are currently available, a high-fidelity gate (probability of error of order 10{sup -6} conditional on the gate being successful) can be implemented using polarization encoding. The detector efficiency determines the overall success probability of the gate but does not affect its fidelity. This can be applied to the efficient construction of optical cluster states with very high fidelity for quantum computing.

Spedalieri, Federico M. [Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 126-347, 4800 Oak Grove Drive, Pasadena, California 91109-8099 (United States); Lee, Hwang [Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 126-347, 4800 Oak Grove Drive, Pasadena, California 91109-8099 (United States); Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States); Dowling, Jonathan P. [Jet Propulsion Laboratory, California Institute of Technology, Mail Stop 126-347, 4800 Oak Grove Drive, Pasadena, California 91109-8099 (United States); Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803-4001 (United States); Institute for Quantum Studies, Department of Physics, Texas A and M University, College Station, Texas 77843-4242 (United States)

2006-01-15

249

High-fidelity linear optical quantum computing with polarization encoding  

NASA Astrophysics Data System (ADS)

We show that the KLM scheme [Knill, Laflamme and Milburn, Nature 409, 46] can be implemented using polarization encoding, thus reducing the number of path modes required by half. One of the main advantages of this new implementation is that it naturally incorporates a loss detection mechanism that makes the probability of a gate introducing a non-detected error, when non-ideal detectors are considered, dependent only on the detector dark-count rate and independent of its efficiency. Since very low dark-count rate detectors are currently available, a high-fidelity gate (probability of error of order 10-6 conditional on the gate being successful) can be implemented using polarization encoding. The detector efficiency determines the overall success probability of the gate but does not affect its fidelity. This can be applied to the efficient construction of optical cluster states with very high fidelity for quantum computing.

Spedalieri, Federico; Lee, Hwang; Dowling, Jonathan

2006-03-01

250

High-fidelity linear optical quantum computing with polarization encoding  

NASA Astrophysics Data System (ADS)

We show that the KLM scheme [Knill, Laflamme, and Milburn, Nature 409, 46 (2001)] can be implemented using polarization encoding, thus reducing the number of path modes required by half. One of the main advantages of this new implementation is that it naturally incorporates a loss detection mechanism that makes the probability of a gate introducing a non-detected error, when non-ideal detectors are considered, dependent only on the detector dark-count rate and independent of its efficiency. Since very low dark-count rate detectors are currently available, a high-fidelity gate (probability of error of order 10-6 conditional on the gate being successful) can be implemented using polarization encoding. The detector efficiency determines the overall success probability of the gate but does not affect its fidelity. This can be applied to the efficient construction of optical cluster states with very high fidelity for quantum computing.

Spedalieri, Federico M.; Lee, Hwang; Dowling, Jonathan P.

2006-01-01

251

Status of high polarization DC high voltage Gallium Arsenide photoelectron guns  

SciTech Connect

Users receive very high beam polarization from reliable GaAs photoelectron guns at facilities worldwide. Satisfaction with beam quality (and a number of lab closures) has reduced the level of polarized source R&D from the heyday of 1990s. However, new experiments and new accelerators proposals including high current unpolarized machines, require GaAs photoguns with capabilities that exceed today's state of the art. This submission describes the capabilities of today's high- polarization DC high voltage GaAs photoguns and discusses issues that must be addressed to meet new demands.

M. Poelker, P. Adderley, J. Brittian, J. Clark, J. Grames, J. Hansknecht, J. McCarter, M. Stutzman, R. Suleiman, K. Surles-Law

2008-01-01

252

Polarization Mode Dispersion in High-Speed Optical Communication Systems  

Microsoft Academic Search

We review the research progress concerning some fundamental issues related to polarization-mode dispersion (PMD) in high-speed fiber-optic transmission systems. We pay particular attention to issues such as the PMD-induced pulse broadening, PMD measurement and emulation, as well as PMD compensation. An electrical equalization technique based on a transversal filter and an optical technique based on a nonlinear chirped fiber Bragg

M. F. FERREIRA; A. N. PINTO; P. S. ANDRÉ; N. J. MUGA; J. E. MACHADO; R. N. NOGUEIRA; S. V. LATAS; M. H. SOUSA; J. F. ROCHA

2005-01-01

253

Decay of Polarons and Molecules in a Strongly Polarized Fermi Gas  

SciTech Connect

The ground state of an impurity immersed in a Fermi sea changes from a polaron to a molecule as the interaction strength is increased. We show here that the coupling between these two states is strongly suppressed due to a combination of phase-space effects and Fermi statistics, and that it vanishes much faster than the energy difference between the two states, thereby confirming the first order nature of the polaron-molecule transition. In the regime where each state is metastable, we find quasiparticle lifetimes which are much longer than what is expected for a usual Fermi liquid. Our analysis indicates that the decay rates are sufficiently slow to be experimentally observable.

Bruun, G. M.; Massignan, P. [Mathematical Physics, Lund Institute of Technology, P.O. Box 118, SE-22100 Lund (Sweden); Grup de Fisica Teorica, Universitat Autonoma de Barcelona, 08193 Bellaterra (Spain) and ICFO-Institut de Ciencies Fotoniques, Mediterranean Technology Park, 08860 Castelldefels, Barcelona (Spain)

2010-07-09

254

Polarization control of a high power laser by adjoint feedback control  

Microsoft Academic Search

A technique for polarizing a high-power laser with unstable resonator optics that places the polarizing elements in a low power feedback path external to the parent resonator structure is described. The technique has been used to polarize a high-power industrial CO2 laser. Rejection ratios for the unwanted polarizations can exceed 20 dB. The polarization vector can be rotated at will

Paul R. Blaszuk; John A. Benda; James L. Forgham; Harold L. Cohen

1993-01-01

255

Rotational cooling of polar molecules by Stark-tuned cavity resonance  

SciTech Connect

A general scheme for rotational cooling of diatomic heteronuclear molecules is proposed. It uses a superconducting microwave cavity to enhance the spontaneous decay via Purcell effect. Rotational cooling can be induced by sequentially tuning each rotational transition to cavity resonance, starting from the highest transition level to the lowest one using an electric field. Electrostatic multipoles can be used to provide large confinement volume with essentially homogeneous background electric field.

Ooi, C. H. Raymond [Fachbereich Physik der Universitaet Konstanz, Fach M674, D-78457 Konstanz, (Germany)

2003-07-01

256

A High-Intensity Highly-Polarized Electron Beam for High-Energy Physics  

SciTech Connect

A new high-energy parity violation (PV) experiment at SLAC as well as particle-physics experiments using future e{sup +}e{sup -} colliders (such as NLC) operating at energies above the scale of unification of the electromagnetic and weak interactions require a highly-polarized electron beam with intensities previously unachievable due to a surface charge limit (SCL) effect at the cathode of the polarized electron source. A newly developed photocathode which allows these high intensities is being used for the SLAC PV experiment E-158. The intensity stability required for stable machine operation is determined by the source laser stability, which has been reduced to 0.5%. Temporal pulse shaping is performed on the laser beam using an improved pulse shaper. Details of the beam generation, energy compensation, and linac performance recently achieved for the SLAC parity violation experiment E-158 are discussed.

Turner, James L

2002-05-30

257

Studies of parity and time reversal violations in heavy polar molecules  

NASA Astrophysics Data System (ADS)

Investigation of phenomena involving parity (P) and time reversal (T) symmetry violations is of fundamental importance in physics. A few experiments to search for the P,T-odd effects have been performed on TlF and YbF molecules and considerable progress for PbO and PbF molecules is on the way. For the interpretation of the measured experimental data, it is necessary to calculate a few molecular properties which cannot be measured experimentally. These molecular properties establish some connection between the measured data and well studied fundamental constants. Very accurate and reliable calculations of these properties usually require accurate accounting for both relativistic and correlation effects in heavy-atom systems. In this review, we discuss the P, T-odd interaction constants W d and W s. The interaction constant W d arises from the interaction of electron electric dipole moment (EDM) d e with the molecular electric field, and the constant W s arises due to the electron-nucleus scalar-pseudoscalar (S-PS) interaction. The knowledge of W d is essential to put a reliable limit on the electron EDM d e , where as the knowledge of W s is necessary to get the information about the electron-nucleus (S-PS) coupling constant k s , and to test the Standard Model (SM) of particle physics. Presently available theoretical results of W d and W s for the ground states of YbF and BaF molecules are also presented.

Nayak, Malaya K.

2010-06-01

258

Studies of parity and time reversal violations in heavy polar molecules  

NASA Astrophysics Data System (ADS)

Investigation of phenomena involving parity (P) and time reversal (T) symmetry violations is of fundamental importance in physics. A few experiments to search for the P,T-odd effects have been performed on TlF and YbF molecules and considerable progress for PbO and PbF molecules is on the way. For the interpretation of the measured experimental data, it is necessary to calculate a few molecular properties which cannot be measured experimentally. These molecular properties establish some connection between the measured data and well studied fundamental constants. Very accurate and reliable calculations of these properties usually require accurate accounting for both relativistic and correlation effects in heavy-atom systems. In this review, we discuss the P, T-odd interaction constants W d and W s. The interaction constant W d arises from the interaction of electron electric dipole moment (EDM) d e with the molecular electric field, and the constant W s arises due to the electron-nucleus scalar-pseudoscalar (S-PS) interaction. The knowledge of W d is essential to put a reliable limit on the electron EDM d e , where as the knowledge of W s is necessary to get the information about the electron-nucleus (S-PS) coupling constant k s , and to test the Standard Model (SM) of particle physics. Presently available theoretical results of W d and W s for the ground states of YbF and BaF molecules are also presented.

Nayak, Malaya K.

259

High harmonic generation spectra of aligned benzene in circular polarized laser field  

NASA Astrophysics Data System (ADS)

We present model calculations of high-order harmonic generation in benzene, aligned in the polarization plane of circular polarized laser field. The resonance states of the system are obtained using complex scaling Floquet approach (i.e., within non-Hermitian quantum mechanics) combined with (t,t') time propagation method. Our results show that the photo-induced dynamics of the model benzene molecule at the laser wavelength of 800 nm is dominated by a single long-lived resonance state up to the intensity of about 90 TW cm-2. The high-order harmonics emitted by the system obey the selection rules derived in [Phys. Rev. Lett. 80, 3743 (1998)] on the basis of the dynamical symmetry of the system, namely the emitted harmonics possess the frequencies (6+/-1)?,(12+/-1)?,..., where ? is the incident laser frequency. These symmetry-allowed harmonics are found to be the dominant ones in the spectrum also when the laser polarization deviates from the ``ideal'' circular one by about 5%. The nonlinear response of the model benzene molecule is found to originate mainly from the field-induced transitions between the bound states, in accordance with the earlier analytical theory. The cut-off position in the calculated high-order harmonic generation spectra depends linearly on the field strength in the studied intensity interval. Our numerical calculations reveal the enhancements of particular high-order harmonics in the plateau region of the spectrum at certain field intensities. We show that these enhancements occur under conditions of avoided crossing of two or several resonance quasi-energies in the complex energy plane.

Ž?ánská, Petra; Averbukh, Vitali; Moiseyev, Nimrod

2003-05-01

260

Thermopower Measurements of Highly Conducting Single-Molecule Devices  

NASA Astrophysics Data System (ADS)

We measure the conductance (G) and thermopower (S) of highly conducting single-molecule junctions with Au electrodes. The junctions are formed and measured using a scanning tunneling microscope-based break-junction technique. The target molecules are synthesized with SnMe3 terminations that cleave off in situ, allowing for the formation of direct Au-C covalent bonds to the electrodes[1,2]. We compare the conductance and thermopower for two families of molecules: pi-conjugated polyphenyls, which have a high conductance and thermopower, and sigma-bonded alkyl systems, where we observe a significant thermopower despite the low conductance. For these measurements, we use the most probable thermopower to determine a power factor, GS^2, for each molecular junction studied. Our results show that the molecular thermopower increases systematically and non-linearly with molecular length and also that the power factor is exceptionally large for the case of the biphenyl. [1] Z. L. Cheng, R. Skouta, H. Vazquez et al., Nat. Nano. 6, 353 (2011). [2] W. Chen, J. R. Widawsky, H. Vázquez et al., J. Am. Chem. Soc. 133, 17160 (2011).

Widawsky, Jonathan R.; Chen, Wenbo; Vazquez, Hector; Kim, Taekyeong; Hybertsen, Mark S.; Breslow, Ronald; Venkataraman, Latha

2013-03-01

261

Recoil-proton polarization in high-energy deuteron photodisintegration with circularly polarized photons.  

PubMed

We measured the angular dependence of the three recoil-proton polarization components in two-body photodisintegration of the deuteron at a photon energy of 2 GeV. These new data provide a benchmark for calculations based on quantum chromodynamics. Two of the five existing models have made predictions of polarization observables. Both explain the longitudinal polarization transfer satisfactorily. Transverse polarizations are not well described, but suggest isovector dominance. PMID:17501566

Jiang, X; Arrington, J; Benmokhtar, F; Camsonne, A; Chen, J P; Choi, S; Chudakov, E; Cusanno, F; Deur, A; Dutta, D; Garibaldi, F; Gaskell, D; Gayou, O; Gilman, R; Glashauser, C; Hamilton, D; Hansen, O; Higinbotham, D W; Holt, R J; de Jager, C W; Jones, M K; Kaufman, L J; Kinney, E R; Kramer, K; Lagamba, L; de Leo, R; Lerose, J; Lhuillier, D; Lindgren, R; Liyanage, N; McCormick, K; Meziani, Z-E; Michaels, R; Moffit, B; Monaghan, P; Nanda, S; Paschke, K D; Perdrisat, C F; Punjabi, V; Qattan, I A; Ransome, R D; Reimer, P E; Reitz, B; Saha, A; Schulte, E C; Sheyor, R; Slifer, K; Solvignon, P; Sulkosky, V; Urciuoli, G M; Voutier, E; Wang, K; Wijesooriya, K; Wojtsekhowski, B; Zhu, L

2007-05-01

262

High Proton Polarization by Microwave-Induced Optical Nuclear Polarization at 77 K  

Microsoft Academic Search

Protons in naphthalene and p-terphenyl doped with pentacene have been polarized up to 32% and 18%, respectively, at liquid nitrogen temperature in a magnetic field of 0.3 T by means of microwave-induced optical nuclear polarization. The polarization was measured by nuclear magnetic resonance as well as by the neutron transmission method. The relaxation time of the proton polarization at 0.0007

M. Iinuma; Y. Takahashi; I. Shaké; M. Oda; A. Masaike; T. Yabuzaki; H. M. Shimizu

2000-01-01

263

High-Resolution, Single-Molecule Measurements of Biomolecular Motion  

PubMed Central

Many biologically important macromolecules undergo motions that are essential to their function. Biophysical techniques can now resolve the motions of single molecules down to the nanometer scale or even below, providing new insights into the mechanisms that drive molecular movements. This review outlines the principal approaches that have been used for high-resolution measurements of single-molecule motion, including centroid tracking, fluorescence resonance energy transfer, magnetic tweezers, atomic force microscopy, and optical traps. For each technique, the principles of operation are outlined, the capabilities and typical applications are examined, and various practical issues for implementation are considered. Extensions to these methods are also discussed, with an eye toward future application to outstanding biological problems.

Greenleaf, William J.; Woodside, Michael T.; Block, Steven M.

2007-01-01

264

Production of a highly polarized sodium atomic beam  

Microsoft Academic Search

Two experimental techniques for preparing atoms in selected states were combined in order to obtain a highly polarized sodium\\u000a beam: Firstly state selection by an inhomogeneous magnetic field and secondly optical pumping with laser light. This results\\u000a in a dominating population of the 3s\\u000a 2\\u000a S\\u000a 1\\/2 ground state levelF=2M\\u000a F=+2 (or alternativelyF=2M\\u000a F=?2) corresponding to high electron as well

D. Hils; W. Jitschin; H. Kleinpoppen

1981-01-01

265

Study of P,T-Parity Violation Effects in Polar Heavy-Atom Molecules  

Microsoft Academic Search

Investigation of P,T-parity nonconservation (PNC) phenomena is of fundamental\\u000aimportance for physics. Experiments to search for PNC effects have been\\u000aperformed on TlF and YbF molecules and are in progress for PbO and PbF\\u000amolecules. For interpretation of molecular PNC experiments it is necessary to\\u000acalculate those needed molecular properties which cannot be measured. In\\u000aparticular, electronic densities in heavy-atom

A. V. Titov; N. S. Mosyagin; A. N. Petrov; T. A. Isaev; D. DeMille

2005-01-01

266

Broadening and shifting of the methanol 119 {mu}m gain line of linear and circular polarization by collision with chiral molecules  

SciTech Connect

Evidence of circular dichroism has been observed in the spectral properties of a gas of left-right symmetric molecules. This dichroism comes about as the result of collisions of the symmetric molecules with left-right asymmetric molecules introduced as a buffer gas. In this sense, the dichroism can be said to have been transferred from the chiral buffer molecules to the symmetric, non-chiral molecules of the background vapor. This transferred dichroism appears as broadening in the gain line of the symmetric molecule which is asymmetric with respect to the right or left handedness of a circularly polarized probe. The broadening of the 119 {mu}m line of the methanol molecule was observed using infrared-far infrared double resonance spectroscopy.

J.S. Bakos; G. Djotyan; Zsuzsa Soerlei; J. Szigeti; D. K. Mansfield; J. Sarkozi

2000-06-21

267

Response functions for dimers and square-symmetric molecules in four-wave-mixing experiments with polarized light.  

PubMed

Four-wave-mixing nonlinear-response functions are given for intermolecular and intramolecular vibrations of a perpendicular dimer and intramolecular vibrations of a square-symmetric molecule containing a doubly degenerate state. A two-dimensional particle-in-a-box model is used to approximate the electronic wave functions and obtain harmonic potentials for nuclear motion. Vibronic interactions due to symmetry-lowering distortions along Jahn-Teller active normal modes are discussed. Electronic dephasing due to nuclear motion along both symmetric and asymmetric normal modes is included in these response functions, but population transfer between states is not. As an illustration, these response functions are used to predict the pump-probe polarization anisotropy in the limit of impulsive excitation. PMID:16095341

Smith, Eric Ryan; Farrow, Darcie A; Jonas, David M

2005-07-22

268

High Proton Polarization by Microwave-Induced Optical Nuclear Polarization at 77 K  

NASA Astrophysics Data System (ADS)

Protons in naphthalene and p-terphenyl doped with pentacene have been polarized up to 32% and 18%, respectively, at liquid nitrogen temperature in a magnetic field of 0.3 T by means of microwave-induced optical nuclear polarization. The polarization was measured by nuclear magnetic resonance as well as by the neutron transmission method. The relaxation time of the proton polarization at 0.0007 T and 77 K was found to be almost 3 h and the polarization enhancement reached a record value of 8×104. The usefulness of the method in many areas of physics and chemistry is discussed.

Iinuma, M.; Takahashi, Y.; Shaké, I.; Oda, M.; Masaike, A.; Yabuzaki, T.; Shimizu, H. M.

2000-01-01

269

High proton polarization by microwave-induced optical nuclear polarization at 77 K  

PubMed

Protons in naphthalene and p-terphenyl doped with pentacene have been polarized up to 32% and 18%, respectively, at liquid nitrogen temperature in a magnetic field of 0.3 T by means of microwave-induced optical nuclear polarization. The polarization was measured by nuclear magnetic resonance as well as by the neutron transmission method. The relaxation time of the proton polarization at 0.0007 T and 77 K was found to be almost 3 h and the polarization enhancement reached a record value of 8x10(4). The usefulness of the method in many areas of physics and chemistry is discussed. PMID:11015862

Iinuma; Takahashi; Shake; Oda; Masaike; Yabuzaki; Shimizu

2000-01-01

270

Dipole moments of ultra-cold polar molecules: a quantum Monte Carlo study  

NASA Astrophysics Data System (ADS)

Recently, there has been a great deal of interest in the production of ultra-cold heteronuclear molecules having large electric dipole moments [1]. This is of interest both for fundamental reasons as well as for applications such as qubits for quantum computing [2]. In this work, we calculate the dipole moment of a potentially implementable two-atom alkaline-alkaline-earth molecule, LiSr. We use correlated wave-function methods including both the quantum chemical configuration interaction (CI) method, and a stochastic quantum Monte Carlo (QMC), to calculate the potential energy surface and dipole moment. We study the dipole moment with increasing accuracy of correlated wave-functions. We then variationally re-optimize the wave-functions, which then serve as the representation of the Fermion nodes in the fixed-node QMC. To treat the Sr atom we employ two types of effective core potentials (ECPs), large core ECPs have only s-states in the valence space, while the small core ECP's valence space includes also the highest s and p semi-core sub-shells. We find significant sensitivity of thedipole moment on both the size of the valence space and on the accuracy of the Fermion nodes. [1] B. Damski, et. al Phys. Rev. Lett. 90, 110401 (2003). [2] D. DeMille, Phys. Rev. Lett. 88, 067901 (2002).

Bajdich, Michal; Guo, Shi; Mitas, Lubos; Reynolds, Peter J.

2009-03-01

271

High bandwidth single polarization fiber with elliptical central air hole  

Microsoft Academic Search

A novel design of single polarization fiber is presented. The structure of the fiber comprises an elliptical central air hole with depressed cladding surrounding the core. Parameters that affect the performance of the single polarization fiber in terms of the location of the single polarization operating window and single polarization bandwidth are analyzed. The analysis results in the identification of

Ming-Jun Li; Xin Chen; D. A. Nolan; G. E. Berkey; Ji Wang; W. A. Wood; L. A. Zenteno

2005-01-01

272

Integration of high k and polar oxides with gallium nitride  

NASA Astrophysics Data System (ADS)

GaN-based transistors offer great promise in high power high frequency applications. Recent understanding of the role of surface effects in AlGaN/GaN based high electron mobility transistor (HEMT) structures and the resulting ability to control these effects has led to the demonstration of very high power densities and near ideal power added efficiencies. Even with these advances, gate leakage is a critical issue that requires further attention. Many different dielectrics have been investigated on GaN, with the most extensive research in SiO2 and Si3N4. While these dielectrics have been shown to effectively reduce gate leakage, the added series capacitance due to the dielectric under the gate and low k of the dielectrics leads to decrease in transconductance as well as an increased threshold voltage. To reduce gate leakage while minimizing the adverse affects of the gate dielectric on these other device properties, high k gate dielectrics were investigated in this work. Barium strontium titanate (BST) was shown to be an effective gate dielectric; however, the rf magnetron sputtering used to deposit the dielectric was shown to damage the underlying HEMT structures. A non-energetic method of oxide deposition was therefore required. To this end, it was also demonstrated that molecular beam epitaxy (MBE) grown rutile TiO2 effectively reduces gate leakage in HEMT devices as well without impacting the underlying AlGaN/GaN structure. Studies of the oxidation of thin e-beam evaporated titanium layers in an UV-generated ozone environment to form TiO2 were also initiated. The high k of these dielectrics resulted in a minimal impact on both transconductance and threshold voltages of the devices. The understanding of polarization in the GaN materials system has recently led to the development of polarization engineered devices. Polar oxides can offer a spontaneous polarization up to almost an order of magnitude higher than that in the AlGaN/GaN system. The integration of rf magnetron sputtered lithium niobate (LiNbO3) with GaN and AlGaN/GaN was investigated in this work.

Hansen, Peter James

273

Electric Quadrupole Transition Measurements of Hydrogen Molecule with High Precision  

NASA Astrophysics Data System (ADS)

Molecular hydrogen is the most fundamental, and the only neutral molecule expected to be both calculated and measured with extremely high accuracy. High-precision measurements of its spectroscopy, especially the levels at the electric ground state, play an important role in the examination of precise quantum chemistry calculations and some fundamental physical constants. In the infrared region, H_2, being a homonuclear diatomic molecule, only has very weak electric quadrupole transitions. We established a new spectroscopy approach with ultra-high precision and sensitivity as well, based on a laser-locked cavity ring-down spectrometer. An equivalent absorption path-length of thousands of kilometers and a frequency precision of 10^{-5} cm^{-1} have been achieved. Ro-vibrational spectra of the second overtone of H_2 have been recorded. The obtained results will provide a direct examination of the high-accuracy quantum theory. It also shades light on the determination of fundamental physical constants such as the electron/proton mass ratio in a molecular system.

Cheng, Cun-Feng; Wang, Jin; Tan, Yan; Liu, An-Wen; Hu, Shui-Ming

2013-06-01

274

High Resolution Studies of Electron Attachment to Molecules  

SciTech Connect

In this paper, we survey recent progress in studies of anion formation via (dissociative) electron attachment (DEA) to simple molecules, as measured with the laser photoelectron attachment (LPA) method at high resolution. The limiting (E{yields}0) threshold behavior of the cross sections is elucidated for s-wave and p-wave attachment. Cusps at onsets for vibrational excitation (VE), due to interaction of the DEA channnel with the VE channel, are clearly detected, and vibrational Feshbach resonances just below vibrational onsets are observed for molecules with sufficiently strong long-range attraction between the electron and the molecule. From the LPA anion yields, absolute DEA cross sections (energy range typically E = 0.001-2 eV) are determined with reference to rate coefficients for thermal electron attachment at the appropriate gas temperature (normally T{sub G} = 300 K). The experimental data are compared with theoretical cross sections, calculated within the framework of an R-matrix or an Effective Range theory approach.

Braun, M.; Ruf, M.-W.; Hotop, H. [Fachbereich Physik, Technische Universitaet Kaiserslautern, 67653 Kaiserslautern (Germany); Fabrikant, I. I. [Fachbereich Physik, Technische Universitaet Kaiserslautern, 67653 Kaiserslautern (Germany); Department of Physics and Astronomy, University of Nebraska, Lincoln, NE (United States)

2009-05-02

275

Single-molecule high-resolution imaging with photobleaching  

NASA Astrophysics Data System (ADS)

Conventional light microscopy is limited in its resolving power by the Rayleigh limit to length scales on the order of 200 nm. On the other hand, spectroscopic techniques such as fluorescence resonance energy transfer cannot be used to measure distances >10 nm, leaving a "gap" in the ability of optical techniques to measure distances on the 10- to 100-nm scale. We have previously demonstrated the ability to localize single dye molecules to a precision of 1.5 nm with subsecond time resolution. Here we locate the position of two dyes and determine their separation with 5-nm precision, using the quantal photobleaching behavior of single fluorescent dye molecules. By fitting images both before and after photobleaching of one of the dyes, we may localize both dyes simultaneously and compute their separation. Hence, we have circumvented the Rayleigh limit and achieved nanometer-scale resolution. Specifically, we demonstrate the technique by measuring the distance between single fluorophores separated by 10-20 nm via attachment to the ends of double-stranded DNA molecules immobilized on a surface. In addition to bridging the gap in optical resolution, this technique may be useful for biophysical or genomic applications, including the generation of super-high-density maps of single-nucleotide polymorphisms.

Gordon, Matthew P.; Ha, Taekjip; Selvin, Paul R.

2004-04-01

276

Experimental and theoretical polarized Raman linear difference spectroscopy of small molecules with a new alignment method using stretched polyethylene film.  

PubMed

This paper reports the development of the new technique of Raman linear difference (RLD) spectroscopy and its application to small molecules: anthracene and nucleotides adenosine-5'-monophosphate, thymidine-5'-monophosphate, guanosine-5'-monophosphate, and cytidine-5'-monophosphate. In this work we also present a new alignment method for Raman spectroscopy where stretched polyethylene films are used as the matrix. Raman spectra using light polarized along the orientation direction and perpendicular to it are reported. The polyethylene (PE) film spectra are consistent with powder samples and films deposited on quartz. RLD spectra determined from the difference of the parallel and perpendicular polarized light Raman spectra are also reported. The equations describing RLD are derived, and RLD spectra of anthracene and thymidine are calculated from these equations using Density Functional Theory and assuming perfect orientation of the samples. Because of the wealth of spectroscopic information in the vibrational spectra of biomolecules together with our ability to calculate spectra as a function of orientation, we conclude that RLD has the potential to provide structural information for biological samples that currently cannot be extracted from any other method. PMID:22122486

Kowalska, Patrycja; Cheeseman, James R; Razmkhah, Kasra; Green, Ben; Nafie, Laurence A; Rodger, Alison

2012-01-11

277

Stripe and line textures in the B2 phase of bent-shape molecules in samples with polar surface anchoring.  

PubMed

In the B2 phase formed by bent-shaped molecules a dense line texture is frequently observed. For the texture description a model is proposed consisting of a periodic system of anticlinic antiferroelectric bulk domains with opposite chiralities separated by ? walls in which polarization rotates. The bulk domains are situated between layers of synclinic ferroelectric phase near the upper and lower surfaces. In the surface layers induced by polar anchoring domains of opposite chirality are separated by defect lines. Under the electric field the ferroelectric layer near one sample surface is growing against the antiferroelectric structure in the sample bulk and the stripe texture is fading out, but still in the saturated field surface lines or walls persist separating ferroelectric domains of opposite chirality. The proposed model is adapted also for a case when the anticlinic antiferroelectric structure in the sample bulk is sandwiched between anticlinic ferroelectric layers near the surfaces. In that case the applied electric field eliminates all the lines because the resulting anticlinic ferroelectric structure is racemic, with no chiral domains. PMID:22304103

Lej?ek, Lubor; Novotná, Vladimíra; Glogarová, Milada

2011-12-01

278

Polar switching in the smectic- A(d)P(A) phase composed of asymmetric bent-core molecules.  

PubMed

We have studied mesogenic properties in the smectic- A(d)P(A) phase of an asymmetric bent-core liquid crystal by means of polarizing optical microscopy, second-harmonic generation (SHG), electro-optical (EO), and dielectric measurements. In homeotropically aligned cells, EO switching is clearly observed from a schlieren texture with both four- and two-brush defects to a uniform bright domain under the application of very low in-plane electric field below 1 V/microm. The phase is SHG active under an electric field, i.e., SHG gradually increases without a threshold and saturates with the increasing field. In homogeneous cells, by applying triangular wave field at saturated voltage, the splitting of the polarization switching current peak is observed, indicating that the mesophase is antiferroelectric. The dielectric studies indicate a Debye-type relaxation of the transverse dipoles associated with the rotation of the molecules about their long axis. The dc bias-dependent dielectric relaxation time and the dielectric strength suggest that a field-induced antiferroelectric-ferroelectric phase transition occurs continuously beyond 1.2 V/microm and is reversible. The field-dependent texture observation is consistent with the dielectric measurements. Two possible models are proposed to interpret the continuous phase transition. PMID:20365387

Guo, Lingfeng; Dhara, Surajit; Sadashiva, B K; Radhika, S; Pratibha, R; Shimbo, Yoshio; Araoka, Fumito; Ishikawa, Ken; Takezoe, Hideo

2010-01-20

279

Longitudinal complex dielectric polarizability and relaxation times of polar molecules in a biaxial liquid crystal phase  

NASA Astrophysics Data System (ADS)

The longitudinal relaxation time and the complex dielectric polarizability of rod-like molecules with dipole moment parallel to the long axis in a biaxial nematic liquid crystal are calculated using as model the rotational Brownian motion in a mean field potential so reducing the problem to a set of linear differential-recurrence relations for the appropriate equilibrium orientational correlation functions. The solution of this set is obtained by matrix continued fractions. Simple analytic equations (based on the exponential separation of the time scales of the intrawell and overbarrier (interwell) relaxation processes), allowing one to understand the qualitative behavior of the system and accurately predicting the longitudinal complex polarizability for a wide range of the barrier height and anisotropy parameters, are proposed.

Kalmykov, Yuri; Coffey, William; Ouari, Bachir; Titov, Sergey

2006-03-01

280

Junctional adhesion molecule-C (JAM-C) regulates polarized neutrophil transendothelial cell migration in vivo  

PubMed Central

Neutrophil migration into inflamed tissues is a fundamental component of innate immunity. A decisive step in this process is the polarised migration of blood neutrophils through endothelial cells (ECs) lining the venular lumen (transendothelial cell migration; TEM) in a luminal to abluminal direction. Using real-time confocal imaging we report that neutrophils can exhibit disrupted polarised TEM (“hesitant” and “reverse”) in vivo. These events were noted in inflammation following ischemia-reperfusion injury, characterised by reduced expression of junctional adhesion molecule C (JAM-C) from EC junctions, and were enhanced by EC JAM-C blockade or genetic deletion. The results identify JAM-C as a key regulator of polarised neutrophil TEM in vivo and suggest that reverse TEM neutrophils can contribute to dissemination of systemic inflammation.

Woodfin, Abigail; Voisin, Mathieu-Benoit; Beyrau, Martina; Colom, Bartomeu; Caille, Dorothee; Diapouli, Frantzeska-Maria; Nash, Gerard B; Chavakis, Triantafyllos; Albelda, Steven M.; Rainger, G Ed; Meda, Paolo; Imhof, Beat A.; Nourshargh, Sussan

2011-01-01

281

Energy levels of a polarizable linear polar molecule in a dc electric field obtained by analogy with the nonrelativistic hydrogen atom  

SciTech Connect

We note that an equation governing the dynamics of a polarizable linear polar molecule in a dc electric field coincides with one of two equations describing a hydrogen atom in the prolate spheroidal coordinate system. Using this analogy, as well as the known algebra of the angular momentum and Runge-Lenz-Pauli operators for the case of a hydrogen atom, the energy levels of a polarizable linear polar molecule in a dc electric field are calculated. For some cases, these energy values are exact.

Sekatskii, S. K. [Laboratoire de Physique de la Matiere Vivante, IPMC, Ecole Polytechnique Federale de Lausanne, BSP, CH 1015 Lausanne (Switzerland)

2007-05-15

282

Anisotropic-Fermi-liquid theory of ultracold fermionic polar molecules: Landau parameters and collective modes  

SciTech Connect

We study the Fermi liquid properties of the cold atomic dipolar Fermi gases with the explicit dipolar anisotropy using perturbative approaches. Due to the explicit dipolar anisotropy, Fermi surfaces exhibit distortions of the d{sub r}{sup 2}{sub -3z}{sup 2} type in three dimensions and of the d{sub x}{sup 2}{sub -y}{sup 2} type in two dimensions. The fermion self-energy, effective mass, and Fermi velocity develop the same anisotropy at the Hartree-Fock level proportional to the interaction strength. The Landau interaction parameters in the isotropic Fermi liquids become the tridiagonal Landau interaction matrices in the dipolar Fermi liquids which renormalize thermodynamic susceptibilities. With large dipolar interaction strength, the Fermi surface collapses along directions perpendicular to the dipole orientation. The dynamic collective zero sound modes exhibit an anisotropic dispersion with the largest sound velocity propagating along the polar directions. Similarly, the longitudinal p-wave channel spin mode becomes a propagating mode with an anisotropic dispersion in multicomponent dipolar systems.

Chan, Ching-Kit; Wu Congjun; Lee, Wei-Cheng [Department of Physics, University of California, San Diego, California 92093 (United States); Sarma, S. Das [Condensed Matter Theory Center, Department of Physics, University of Maryland, College Park, Maryland 20742 (United States)

2010-02-15

283

Ultracold spin-polarized mixtures of {sup 2}{Sigma} molecules with S-state atoms: Collisional stability and implications for sympathetic cooling  

SciTech Connect

The prospects of sympathetic cooling of polar molecules with magnetically cotrapped alkali-metal atoms are generally considered poor due to strongly anisotropic atom-molecule interactions leading to large spin relaxation rates. Using rigorous quantum scattering calculations based on ab initio interaction potentials, we show that inelastic spin relaxation in low-temperature collisions of CaH({sup 2}{Sigma}) molecules with Li and Mg atoms occurs at a slow rate despite the strongly anisotropic interactions. This unexpected result, which we rationalize using multichannel quantum-defect theory, opens up the possibility of sympathetic cooling of polar {sup 2}{Sigma} molecules with alkali-metal atoms in a magnetic trap and with alkaline-earth-metal atoms in an optical dipole trap.

Tscherbul, T. V. [Harvard-MIT Center for Ultracold Atoms, Cambridge, Massachusetts 02138 (United States); ITAMP, Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts 02138 (United States); Klos, J. [Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742 (United States); Buchachenko, A. A. [Department of Chemistry, Moscow State University, Moscow RU-119991 (Russian Federation)

2011-10-15

284

Polar CAP Model for Pulsar High-Energy Emission  

NASA Astrophysics Data System (ADS)

The study of physical processes associated with particle acceleration in the open field line region above the polar cap (PC) of an isolated neutron star (NS) plays a fundamental role in our understanding and interpretation of high-energy emission from pulsars. The systematic study of particle acceleration and formation of electron-positron pair fronts above the PCs of NSs was initiated two decades ago. The detailed analysis of these processes is now possible with the development of pair cascade codes that enables us to calculate the spectra and pulse profiles of high-energy emission from pulsars. The calculation of pair formation and gamma-ray production is being improved to include new results on the PC physics. We briefly outline the current status of the PC model for pulsar high-energy emission, focusing on some of our most recent results on the theoretical modeling of the PC acceleration and gamma-ray emission.

Harding, A. K.; Muslimov, A. G.

285

Relationships Between Polar Highs Activity and Air Temperature Anomalies in the North Pacific Region  

Microsoft Academic Search

Because of thermal deficit in the Arctic Basin region which reign throughout the year and especially during the winter season, polar air masses break out from the North Pole equatorward as polar highs. Polar highs which circulate across the North Pacific region descend from North Eastern Siberia. They travel the Pacific Ocean by Bering, Okhotsk, Japan and East China seas,

A. Favre; M. Leroux; A. Gershunov

2003-01-01

286

Highly specialized microbial diversity in hyper-arid polar desert.  

PubMed

The McMurdo Dry Valleys in Antarctica are a cold hyperarid polar desert that present extreme challenges to life. Here, we report a culture-independent survey of multidomain microbial biodiversity in McKelvey Valley, a pristine example of the coldest desert on Earth. We demonstrate that life has adapted to form highly-specialized communities in distinct lithic niches occurring concomitantly within this terrain. Endoliths and chasmoliths in sandstone displayed greatest diversity, whereas soil was relatively depauperate and lacked a significant photoautotrophic component, apart from isolated islands of hypolithic cyanobacterial colonization on quartz rocks in soil contact. Communities supported previously unreported polar bacteria and fungi, but archaea were absent from all niches. Lithic community structure did not vary significantly on a landscape scale and stochastic moisture input due to snowmelt resulted in increases in colonization frequency without significantly affecting diversity. The findings show that biodiversity near the cold-arid limit for life is more complex than previously appreciated, but communities lack variability probably due to the high selective pressures of this extreme environment. PMID:19850879

Pointing, Stephen B; Chan, Yuki; Lacap, Donnabella C; Lau, Maggie C Y; Jurgens, Joel A; Farrell, Roberta L

2009-10-22

287

Self-assembly of disc-like molecules on polar surfaces  

NASA Astrophysics Data System (ADS)

Solution-processable solar cells provide the potential to reduce the cost and increase the availability of solar electricity. Long-range molecular order in active media of solution-processable solar cells is essential for charge transfer, and self-assembly provides a simple and efficient process to achieve molecular order on a large scale. Obtaining spontaneous alignment of charge-transfer media that maximizes light-to-electricity conversion while minimizing energy waste is essential long-range molecular order development. Molecular order decreases the potential of hole and electron pair recombination and provides a direct path for the electron to reach the electrode and produce energy. Graphene quantum dots (GQD) are ideal for solution-processable solar cells due to the abundance of carbon and a large absorption cross-section in the visible light range. Hexabenzocoronene tri-acid (HBCTA) is a smaller system that has ideal properties for preliminary investigation of molecular order. In this study, we investigate the assembly of HBCTA and different GQDs on water and mica substrates with Langmuir techniques and atomic force microscopy (AFM). GQD of varying size and functionality, and HBCTA were observed to have isothermal compression behavior involving gas, liquid, and condensed phase transitions. We further characterized these molecular behaviors at particular pressures by Langmuir deposition to mica substrates. AFM imagining reveals monolayer assemblies of "face-on" orientation for larger quantum dots and "edge-on" orientation for smaller quantum dots. These assembly features are attributed to the numbers of carboxylic acid groups in the GQDs and their geometrical arrangement. HBCTA shows a concentration and pressure-dependent arrangement of molecules.

Hamilton, Irma P.

288

High voltage processing of the SLC polarized electron gun  

SciTech Connect

The SLC polarized electron gun operates at 120 kV with very low dark current to maintain the ultra high vacuum (UHV). This strict requirement protects the extremely sensitive photocathode from contaminants caused by high voltage (HV) activity. Thorough HV processing is thus required x-ray sensitive photographic film, a nanoammeter in series with gun power supply, a radiation meter, a sensitive residual gas analyzer and surface x-ray spectrometry were used to study areas in the gun where HV activity occurred. By reducing the electric field gradients, carefully preparing the HV surfaces and adhering to very strict clean assembly procedures, we found it possible to process the gun so as to reduce both the dark current at operating voltage and the probability of HV discharge. These HV preparation and processing techniques are described.

Saez, P.; Clendenin, J.; Garden, C.; Hoyt, E.; Klaisner, L.; Prescott, C.; Schultz, D.; Tang, H.

1993-04-01

289

High sensitivity optical microscope for single molecule spectroscopy studies  

NASA Astrophysics Data System (ADS)

We describe the setup and apply two algorithms for fast imaging in a sample raster scanning two photon microscope. Imaging can be performed at a rate of 1-100 lines per second with a closed loop piezo actuator, and the detection is performed via avalanche photodiodes. This allows to investigate single molecule emission with 50 ms time resolution. In a slow scanning algorithm we have implemented fluorescence fluctuation analysis by computing the photon counting histogram (PCH) on each pixel of the image. In a fast-scan acquistion method the image acquistion rate is 5 lines per second on a large field of view and high resolution(50 nm scanning step, 100×100 ?m2 field of view) and ?100 lines per second on smaller field of views with optically limited resolution (200 nm scanning step, 20×20 ?m2 field of view). This figure, which is lower than the typical value for normal confocal scanning imaging (?500 lines per second), allows nevertheless to perform imaging studies of extended samples in reasonable times for intracellular kinetics and interactions. With this setup and by means of the PCH analysis we are able to discriminate between local concentration and molecular brightness on extended samples also at the level of the single molecule.

Malengo, Gabriele; Milani, Roberto; Cannone, Fabio; Krol, Silke; Diaspro, Alberto; Chirico, Giuseppe

2004-08-01

290

Origin of spontaneous polarization, tilt, and chiral structure of smectic liquid-crystal phases composed of bent-core molecules: a molecular model.  

PubMed

A simple molecular model is proposed for novel bent-core smectic phases that enables one to explain the origin of the experimentally observed chiral structure of the B2 phase composed of nonchiral banana-shaped molecules. It is shown that in the perfectly ordered smectic phase the distributed dispersion interaction between banana-shaped molecules stabilizes the spontaneous polarization and may be responsible for the tilt of the director. The orientation of the spontaneous polarization with respect to the tilt plane is determined by the balance between the dispersion and electrostatic dipole-dipole intermolecular interactions. In particular, sufficiently strong dipole-dipole interaction promotes the B2 phase where the polarization is normal to the tilt plane. The actual chiral structure of each smectic layer in the B2 phase appears as a result of the symmetry breaking. In the case of small molecular dipoles the nonchiral polar smectic phase is formed where the spontaneous polarization is parallel to the tilt plane. The role of the opening angle and of the axial ratio of banana-shaped molecules is also considered and a phase diagram is presented. PMID:15447506

Emelyanenko, A V; Osipov, M A

2004-08-31

291

Quantum Drude oscillator model of atoms and molecules: Many-body polarization and dispersion interactions for atomistic simulation  

NASA Astrophysics Data System (ADS)

Treating both many-body polarization and dispersion interactions is now recognized as a key element in achieving the level of atomistic modeling required to reveal novel physics in complex systems. The quantum Drude oscillator (QDO), a Gaussian-based, coarse grained electronic structure model, captures both many-body polarization and dispersion and has linear scale computational complexity with system size, hence it is a leading candidate next-generation simulation method. Here, we investigate the extent to which the QDO treatment reproduces the desired long-range atomic and molecular properties. We present closed form expressions for leading order polarizabilities and dispersion coefficients and derive invariant (parameter-free) scaling relationships among multipole polarizability and many-body dispersion coefficients that arise due to the Gaussian nature of the model. We show that these “combining rules” hold to within a few percent for noble gas atoms, alkali metals, and simple (first-row hydride) molecules such as water; this is consistent with the surprising success that models with underlying Gaussian statistics often exhibit in physics. We present a diagrammatic Jastrow-type perturbation theory tailored to the QDO model that serves to illustrate the rich types of responses that the QDO approach engenders. QDO models for neon, argon, krypton, and xenon, designed to reproduce gas phase properties, are constructed and their condensed phase properties explored via linear scale diffusion Monte Carlo (DMC) and path integral molecular dynamics (PIMD) simulations. Good agreement with experimental data for structure, cohesive energy, and bulk modulus is found, demonstrating a degree of transferability that cannot be achieved using current empirical models or fully ab initio descriptions.

Jones, Andrew P.; Crain, Jason; Sokhan, Vlad P.; Whitfield, Troy W.; Martyna, Glenn J.

2013-04-01

292

SLC polarized beam source ultra-high-vacuum design  

SciTech Connect

This paper describes the design of the ultra-high vacuum system for the beam-line from the 160-kV polarized electron gun to the linac injector in the Stanford Linear Collider (SLC). The polarized electron source is a GaAs photocathode, requiring 10{sup {minus}11}-Torr-range pressure for adequate quantum efficiency and longevity. The photo-cathode is illuminated by 3-nsec-long laser pulses. Photo-cathode maintenance and improvements require occasional substitution of guns with rapid restoration of UHV conditions. Differential pumping is crucial since the pressure in the injector is more than 10 times greater than the photocathode can tolerate, and since electron-stimulated gas desorption from beam loss in excess of 0.1% of the 20-nC pulses may poison the photocathode. Our design for the transport line contains a differential pumping region isolated by a pair of valves. Exchange of guns requires venting only this isolated region which can be restored to UHV rapidly by baking. The differential pumping is performed by non-evaporable getters (NEGs) and an ion pump. 3 refs., 3 figs.

Lavine, T.L.; Clendenin, J.E.; Garwin, E.L.; Hoyt, E.W.; Hoyt, M.W.; Miller, R.H.; Nuttall, J.A.; Schultz, D.C.; Wright, D.

1991-05-01

293

Anti-Hyperon polarization in high energy pp collisions withpolarized beams  

SciTech Connect

We study the longitudinal polarization of the {bar {Sigma}}{sup -}, {bar {Sigma}}{sup +}, {bar {Xi}}{sup 0} and {bar {Xi}}{sup +} anti-hyperons in polarized high energy pp collisions at large transverse momenta, extending a recent study for the {bar {Lambda}} antihyperon. We make predictions by using different parameterizations of the polarized parton densities and models for the polarized fragmentation functions. Similar to the {bar {Lambda}} polarization, the {bar {Xi}}{sup 0} and {bar {Xi}}{sup +} polarizations are found to be sensitive to the polarized anti-strange sea, {Delta}{bar s}(x), in the nucleon. The {bar {Sigma}}{sup -} and {bar {Sigma}}{sup +} polarizations show sensitivity to the light sea quark polarizations, {Delta}{bar u}(x) and {Delta}{bar d}(x), and their asymmetry.

Chen, Ye; Liang, Zuo-tang; Sichtermann, Ernst; Xu, Qing-hua; Zhou, Shan-shan

2007-11-20

294

Generation of High Efficiency Longitudinally Polarized Beam using High NA Lens Axicon and Dedicated Phase Filter  

SciTech Connect

We propose to use pure phase filter in combination with high NA lens axicon to achieve high efficient longitudinally polarized beam with a subwavelength spot size and large depth of focus using hyper geometric Gaussian beam. Using this system, the spot size is reduced to 0.392 {lambda} and the depth of focus is increased to 7 {lambda}. The efficiency of such system is found to be 87%. This high efficient longitudinally polarized beam generated by hyper geometric Gaussian beam is useful for most of the near-field optics applications.

Rajesh, K. B.; Mohankumar, R.; Prathibajanet, C. Amala; Pillai, T. V. S. [Department of Physics, Anna University of Technology Tirunelveli (India); Jaroszewicz, Z. [Institute of Applied Optics, Department of Physical Optics, Warsaw (Poland)

2011-10-20

295

Prospects for sympathetic cooling of polar molecules: NH with alkali-metal and alkaline-earth atoms - a new hope  

Microsoft Academic Search

We explore the potential energy surfaces for NH molecules interacting with alkali-metal and alkaline-earth atoms using highly correlated ab initio electronic structure calculations. The surfaces for interaction with alkali-metal atoms have deep wells dominated by covalent forces. The result- ing strong anisotropies will produce strongly inelastic collisions. The surfaces for interaction with alkaline-earth atoms have shallower wells that are dominated

Pavel Soldan

296

Excitation of atoms and molecules by highly relativistic ions  

NASA Astrophysics Data System (ADS)

We study the cross section for inelastic collisions of atoms and small molecules under the influence of highly relativistic charged ions as they occur in storage rings and accelerators. Starting from fully time-resolved calculations of the electronic dynamics, we study a set of complementing approximations, a sudden approximation for the extremely fast collision at low impact parameter combined with time-dependent perturbation theory for the weak and slow collisions at large impact parameters. This leads eventually to a simple, yet reliable, estimate in terms of the ion-hydrogen cross section and the variance of the dipole moment for the actual system. We discuss, in particular, the systems H, He, C, N, O, Ne, H2 , and N2 .

Bär, M.; Jakob, B.; Reinhard, P.-G.; Toepffer, C.

2006-02-01

297

Excitation of atoms and molecules by highly relativistic ions  

SciTech Connect

We study the cross section for inelastic collisions of atoms and small molecules under the influence of highly relativistic charged ions as they occur in storage rings and accelerators. Starting from fully time-resolved calculations of the electronic dynamics, we study a set of complementing approximations, a sudden approximation for the extremely fast collision at low impact parameter combined with time-dependent perturbation theory for the weak and slow collisions at large impact parameters. This leads eventually to a simple, yet reliable, estimate in terms of the ion-hydrogen cross section and the variance of the dipole moment for the actual system. We discuss, in particular, the systems H, He, C, N, O, Ne, H{sub 2}, and N{sub 2}.

Baer, M.; Jakob, B.; Reinhard, P.-G.; Toepffer, C. [Institut fuer Theoretische Physik II, Universitaet Erlangen-Nuernberg, Staudtstrasse 7, D-91058 Erlangen (Germany)

2006-02-15

298

A High-Throughput Screening Method to Identify Small Molecule Inhibitors of Thyroid Hormone Receptor Coactivator Binding  

NSDL National Science Digital Library

To provide alternative methods for regulation of gene transcription initiated by the binding of thyroid hormone (T3) to the thyroid receptor (TR), we have developed a high-throughput method for discovering inhibitors of the interaction of TR with its transcriptional coactivators. The screening method is based on fluorescence polarization (FP), one of the most sensitive and robust high-throughput methods for the study of protein-protein interactions. A fluorescently labeled coactivator is excited by polarized light. The emitted polarized light is a function of the molecular properties of the labeled coactivator, especially Brownian molecular rotation, which is very sensitive to changes in the molecular mass of the labeled complex. Dissociation of hormone receptor from fluorescently labeled coactivator peptide in the presence of small molecules can be detected by this competition method, and the assay can be performed in a high-throughput screening format. Hit compounds identified by this method are evaluated by several secondary assay methods, including a dose-response analysis, a semiquantitative glutathione-S-transferase assay, and a hormone displacement assay. Subsequent in vitro transcription assays can detect inhibition of thyroid signaling at low micromolar concentrations of small molecules in the presence of T3.

Leggy A. Arnold (; REV); Eva Estebanez-Perpina (; REV); Marie Togashi (San Francisco;University of California REV); Anang Shelat (; REV); Cory A. Ocasio (San Francisco;University of California REV); Andrea C. McReynolds (San Francisco;University of California REV)

2006-06-27

299

Tensor polarization of the phi meson photoproduced at high t  

SciTech Connect

As part of a measurement [E. Anciant et al., Phys. Rev. Lett. 85, 4682 (2000)] of the cross section of phi meson photoproduction to high momentum transfer, we measured the polar angular decay distribution of the outgoing K+ in the channel K+K- in the phi center-of-mass frame (the helicity frame). We find that phi s-channel helicity conservation (SCHC) holds in the kinematical range where t-channel exchange dominates (up to -t {approx}2.5 GeV2 for E = 3.6 GeV). Above this momentum, phi u-channel production of a meson dominates and induces a violation of SCHC. The deduced value of the phi NN coupling constant lies in the upper range of previously reported values.

K. McCormick; G. Audit; J. M. Laget; G. Adams; P. Ambrozewicz; E. Anciant; M. Anghinolfi; B. Asavapibhop; T. Auger; H. Avakian; H. Bagdasaryan; J. P. Ball; S. Barrow; M. Battaglieri; K. Beard; M. Bektasoglu; M. Bellis; N. Benmouna; B. L. Berman; N. Bianchi; A. S. Biselli; S. Boiarinov; B. E. Bonner; S. Bouchigny; R. Bradford; W. K. Brooks; V. D. Burkert; C. Butuceanu; J. R. Calarco; D. S. Carman; B. Carnahan; C. Cetina; S. Chen; P. L. Cole; A. Coleman; J. Connelly; D. Cords; P. Corvisiero; D. Crabb; H. Crannell; J. P. Cummings; E. De Sanctis; R. DeVita; P. V. Degtyarenko; H. Denizli; L. Dennis; K. V. Dharmawardane; C. Djalali; G. E. Dodge; D. Doughty; P. Dragovitsch; M. Dugger; S. Dytman; O. P. Dzyubak; M. Eckhause; H. Egiyan; K. S. Egiyan; L. Elouadrhiri; P. Eugenio; L. Farhi; R. J. Feuerbach; J. Ficenec; T. A. Forest; V. Frolov; H. Funsten; S. J. Gaff; M. Gai; M. Garcon; G. Gavalian; S. Gilad; G. P. Gilfoyle

2004-03-22

300

Linear Polarization Imaging with Very Long Baseline Interferometry at High Frequencies  

Microsoft Academic Search

We describe a new method to self-calibrate the instrumental polarization characteristics in polarimetric very long baseline interferometry (VLBI) observations. The method is especially useful at high frequencies where no suitable calibrator sources with known polarization properties are available. In a test experiment with the Very Long Baseline Array (VLBA), the feed polarization parameters (D factors) were calibrated to within 0.2%

K. J. Leppanen; J. A. Zensus; P. J. Diamond

1995-01-01

301

POLARIZED ION SOURCES FOR HIGH ENERGY ACCELERATORS AND COLLIDERS  

SciTech Connect

The recent progress in polarized ion source development is reviewed. In dc operation a 1.0 mA polarized H{sup -} ion current is now available from the Optically-Pumped Polarized Ion Source (OPPIS) . In pulsed operation a 10 mA polarized H{sup -} ion current was demonstrated at the TRIUMF pulsed OPPIS test bench and a 3.5 mA peak current was obtained from an Atomic Beam Source (ABS) at the INR Moscow test bench. The possibilities for future improvements with both techniques are discussed. A new OPPIS for RHIC spin physics is described. The OPPIS reliably delivered polarized beam for the polarized run at RHIC. The results obtained with a new pulsed ABS injector for the IUCF Cooler Ring are also discussed.

ZELENSKI,A.N.

2000-10-16

302

POLARIZED ION SOURCES FOR HIGH ENERGY ACCELERATORS AND COLLIDERS  

SciTech Connect

The recent progress in polarized ion source development is reviewed. In dc operation a 1.0 mA polarized H{sup -} ion current is now available from the Optically-Pumped Polarized Ion Source (OPPIS). In pulsed operation a 10 mA polarized H{sup -} ion current was demonstrated at the TRIUMF pulsed OPPIS test bench and a 3.5 mA peak current was obtained from an Atomic Beam Source (ABS) at the INR Moscow test bench. The possibilities for future improvements with both techniques are discussed. A new OPPIS for RHIC spin physics is described. The OPPIS reliably delivered polarized beam for the polarized run at RHIC. The results obtained with a new pulsed ABS injector for the IUCF Cooler Ring are also discussed.

ZELENSKI,A.N.

2000-10-16

303

Polarization Transfer in Proton Compton Scattering at High Momentum Transfer  

Microsoft Academic Search

Compton scattering from the proton was investigated at s=6.9 GeV2 and t=-4.0 GeV2 via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in disagreement with a prediction of perturbative QCD based on a two-gluon exchange mechanism, but agree well with a prediction based on a reaction

D. J. Hamilton; V. H. Mamyan; K. A. Aniol; J. R. Annand; P. Y. Bertin; L. Bimbot; P. Bosted; J. R. Calarco; A. Camsonne; G. C. Chang; T.-H. Chang; Seonho Choi; E. Chudakov; A. Danagoulian; P. Degtyarenko; C. W. de Jager; A. Deur; D. Dutta; K. Egiyan; H. Gao; F. Garibaldi; O. Gayou; R. Gilman; A. Glamazdin; C. Glashausser; J. Gomez; J.-O. Hansen; D. Higinbotham; W. Hinton; T. Horn; C. Howell; T. Hunyady; C. E. Hyde-Wright; X. Jiang; M. K. Jones; M. Khandaker; A. Ketikyan; V. Kubarovsky; K. Kramer; G. Kumbartzki; G. Laveissière; J. Lerose; R. A. Lindgren; D. J. Margaziotis; P. Markowitz; K. McCormick; Z.-E. Meziani; R. Michaels; P. Moussiegt; S. Nanda; A. M. Nathan; D. M. Nikolenko; V. Nelyubin; B. E. Norum; K. Paschke; L. Pentchev; C. F. Perdrisat; E. Piasetzky; R. Pomatsalyuk; V. A. Punjabi; I. Rachek; A. Radyushkin; B. Reitz; R. Roche; M. Roedelbronn; G. Ron; F. Sabatie; A. Saha; N. Savvinov; A. Shahinyan; Y. Shestakov; S. Sirca; K. Slifer; P. Solvignon; P. Stoler; S. Tajima; V. Sulkosky; L. Todor; B. Vlahovic; L. B. Weinstein; K. Wang; B. Wojtsekhowski; H. Voskanyan; H. Xiang; X. Zheng; L. Zhu

2005-01-01

304

Large, accessible, highly polarized frozen-spin solid HD targets  

SciTech Connect

New advances in frozen-spin polarized solid HD make practical the use of large targets of independently polarizable H and D for experiments in fusion, photonuclear and particle physics. Long polarization-retention times of about a year at 1.5 K and 7.5 Tesla allow multiple target production and long term storage in economical cryostats, for off-the-shelf availability of polarized HD material and targets. Polarization-retention times at sub-Tesla fields, which exceed a week, provide a fair match between polarization-production time and target-utilization time in moderate fields, for weakly ionizing beam fluxes in which radiation damage to the target is small. Because of the convenient 1.5{endash}4 K frozen-spin temperature range, cold-transfer (4 K) portable apparatuses, which have already been constructed and used, can move the targets readily from polarization-production systems to storage or in-beam cryostats with negligible polarization loss. This permits total separation of polarization-production and target-utilization apparatuses, and the possibility of assembling very large targets. {copyright} {ital 1995 American Institute of Physics.}

Honig, A.; Fan, Q.; Wei, X. [Physics Dept., Syracuse University, Syracuse, New York 13244 (United States); Rigney, M. [IN2P3, IPN Orsay (France); Sandorfi, A.M. [LEGS Project, Brookhaven National Laboratory, Upton, New York 11973 (United States); Whisnant, C.S. [Physics Dept., University of S. Carolina, Columbia, South Carolina 29208 (United States)

1995-09-01

305

High precision measurement of the polarization in solid state polarized targets using NMR  

NASA Astrophysics Data System (ADS)

The factors are reviewed that can affect the systematic uncertainties in CW-NMR measurements of the polarization in solid state polarized targets. The main problem with large signals, typically obtained with protons, is non-linearity arising from failure of the constant RF drive current assumption. The non-linearity can be reduced by operation at lower than normal signal levels. With the much smaller size deuteron signals, a limiting factor may be the instability of the background signal generated by the resonant length cable, used in the standard system. A new system is demonstrated, using non-resonant length cables, which is expected to reduce these uncertainties to a low level.

Court, G. R.; Houlden, M. A.; Bültmann, S.; Crabb, D. G.; Day, D. B.; Prok, Y. A.; Penttila, S. I.; Keith, C. D.

2004-07-01

306

Multielectron effects in high harmonic generation in N2 and benzene: simulation using a non-adiabatic quantum molecular dynamics approach for laser-molecule interactions.  

PubMed

A mixed quantum-classical approach is introduced which allows the dynamical response of molecules driven far from equilibrium to be modeled. This method is applied to the interaction of molecules with intense, short-duration laser pulses. The electronic response of the molecule is described using time-dependent density functional theory (TDDFT) and the resulting Kohn-Sham equations are solved numerically using finite difference techniques in conjunction with local and global adaptations of an underlying grid in curvilinear coordinates. Using this approach, simulations can be carried out for a wide range of molecules and both all-electron and pseudopotential calculations are possible. The approach is applied to the study of high harmonic generation in N(2) and benzene using linearly polarized laser pulses and, to the best of our knowledge, the results for benzene represent the first TDDFT calculations of high harmonic generation in benzene using linearly polarized laser pulses. For N(2) an enhancement of the cut-off harmonics is observed whenever the laser polarization is aligned perpendicular to the molecular axis. This enhancement is attributed to the symmetry properties of the Kohn-Sham orbital that responds predominantly to the pulse. In benzene we predict that a suppression in the cut-off harmonics occurs whenever the laser polarization is aligned parallel to the molecular plane. We attribute this suppression to the symmetry-induced response of the highest-occupied molecular orbital. PMID:22612091

Dundas, Daniel

2012-05-21

307

Prospects for sympathetic cooling of polar molecules: NH with alkali-metal and alkaline-earth atoms – a new hope  

Microsoft Academic Search

We explore the potential energy surfaces for NH molecules interacting with\\u000aalkali-metal and alkaline-earth atoms using highly correlated ab-initio\\u000aelectronic structure calculations. The surfaces for interaction with\\u000aalkali-metal atoms have deep wells dominated by covalent forces. The resulting\\u000astrong anisotropies will produce strongly inelastic collisions. The surfaces\\u000afor interaction with alkaline-earth atoms have shallower wells that are\\u000adominated by induction

Pavel Soldán; Piotr S. ?uchowski; Jeremy M. Hutson

2009-01-01

308

A Simple High Performance Beamline for Small Molecule Chemical Crystallography  

SciTech Connect

An innovative beamline for small molecule chemical crystallography has been built at the Advanced Light Source. The system permits the study of crystals as small as 10{mu}m x 10{mu}m x 10{mu}m. The beamline produces a 7-17 keV x-ray beam focused to a 280{mu}m x 90{mu}m spot. A channel-cut Si<111> monochromator and a toroidal mirror are inside the synchrotron shield wall only 7m from the bending magnet source point. The monochromator is cooled with a small Joule-Thomson refrigerator to produce a very small beam motion with different heat loads. The experimental hutch contains a vertically mounted sample goniometer and a CCD detector. An on-axis visual alignment camera allows the small crystals to be accurately centered within the x-ray beam. Examples of the crystal structures solved with this system are given. The beamline is also used for high-pressure powder diffraction experiments using a diamond anvil cell that is mounted on a stage system that can be quickly installed and removed.

Thompson, A.C.; Padmore, H.A.; Celestre, R.S.; Clark, S.M.; Domning, E.E.; Franck, K.D.; Morrison, G.Y. [Lawrence Berkeley Laboratory (United States); Oliver, A.G. [Chemistry Dept., University of California at Berkeley (United States); Teat, S.J. [Daresbury Laboratory (United Kingdom)

2004-05-12

309

High-Resolution Optical Tweezers for Single-Molecule Manipulation  

PubMed Central

Forces hold everything together and determine its structure and dynamics. In particular, tiny forces of 1-100 piconewtons govern the structures and dynamics of biomacromolecules. These forces enable folding, assembly, conformational fluctuations, or directional movements of biomacromolecules over sub-nanometer to micron distances. Optical tweezers have become a revolutionary tool to probe the forces, structures, and dynamics associated with biomacromolecules at a single-molecule level with unprecedented resolution. In this review, we introduce the basic principles of optical tweezers and their latest applications in studies of protein folding and molecular motors. We describe the folding dynamics of two strong coiled coil proteins, the GCN4-derived protein pIL and the SNARE complex. Both complexes show multiple folding intermediates and pathways. ATP-dependent chromatin remodeling complexes translocate DNA to remodel chromatin structures. The detailed DNA translocation properties of such molecular motors have recently been characterized by optical tweezers, which are reviewed here. Finally, several future developments and applications of optical tweezers are discussed. These past and future applications demonstrate the unique advantages of high-resolution optical tweezers in quantitatively characterizing complex multi-scale dynamics of biomacromolecules.

Zhang, Xinming; Ma, Lu; Zhang, Yongli

2013-01-01

310

Polarization mosaicing: high dynamic range and polarization imaging in a wide field of view  

Microsoft Academic Search

We present an approach for imaging the polarization state of scene points in a wide field of view, while enhancing the radiometric dynamic range of imaging systems. This is achieved by a simple modification of image mosaicking, which is a common technique in remote sensing. In traditional image mosaics, images taken in varying directions or positions are stitched to obtain

Yoav Y. Schechner; Shree K. Nayar

2003-01-01

311

A novel high-throughput scanning microscope for label-free detection of protein and small-molecule chemical microarrays  

PubMed Central

We describe a novel scanning optical microscope based on a polarization-modulated nulling ellipsometry. The new microscope employs a combination of scanning mirror and sample translation and thus enables high-throughput label-free detection of biomolecular microarrays with more than 10,000 protein or small molecule targets. For illustration, we show the image of a 2760-spot protein microarray on a functionalized glass slide obtained with such a microscope. The new scanning microscope is also capable of determining, in parallel, the real-time binding kinetics of multiple molecular species under aqueous conditions.

Fei, Y.Y.; Landry, J.P.; Sun, Y.S.; Luo, J.T.; Wang, X.B.; Lam, K.S; Zhu, X.D.

2009-01-01

312

Selective addressing of high-rank atomic polarization moments.  

PubMed

We describe a method of selective generation and study of polarization moments of up to the highest-rank kappa=2F possible for a quantum state with total angular momentum F. The technique is based on nonlinear magneto-optical rotation with frequency-modulated light. Various polarization moments are distinguished by the periodicity of light-polarization rotation induced by the atoms during Larmor precession and exhibit distinct light-intensity and frequency dependences. We apply the method to study polarization moments of 87Rb atoms contained in a vapor cell with antirelaxation coating. Distinct ultranarrow (1-Hz wide) resonances, corresponding to different multipoles, appear in the magnetic-field dependence of the optical rotation. The use of the highest-multipole resonances supported by a given system has important applications in quantum and nonlinear optics and in magnetometry. PMID:12857128

Yashchuk, V V; Budker, D; Gawlik, W; Kimball, D F; Malakyan, Yu P; Rochester, S M

2003-06-26

313

High deuteron polarization in trityl radical doped deuterated polystyrene  

NASA Astrophysics Data System (ADS)

Deuterated polystyrene for polarized solid targets has been prepared by chemical doping with the trityl radical 'Finland D36' (AH 110 355 deutero acid form). Thin foils doped with various radical densities have been produced using tetrahydrofuran as solvent. Dynamic nuclear polarization technique has been applied to polarize deuterons in the samples (98%-D) at the temperature range of about 1 K and magnetic fields of 2.5 T and 5.0 T. A maximum deuteron polarization of ?61.5% with a build-up time of 100 min has been achieved at 5.0 T and about 500 mK at a radical density of 1.16×1019 spins/g.

Wang, Li; Berlin, A.; Doshita, N.; Herick, J.; Hess, C.; Iwata, T.; Kondo, K.; Meyer, W.; Reicherz, G.

2013-11-01

314

Investigation of the Potential of the Dissolution Dynamic Nuclear Polarization Method for General Sensitivity Enhancement in Small-Molecule NMR Spectroscopy  

Microsoft Academic Search

.  We report results of applying a commercial implementation of the dissolution dynamic nuclear polarization (DNP) methodology\\u000a developed by K. G. Golman et al. to a range of molecular species in the mass range of 100–400 Da. The molecules are typical\\u000a of those that might be encountered in natural product chemistry or pharmaceutical analysis. Using an experimental protocol\\u000a previously reported, in

I. J. Day; J. C. Mitchell; M. J. Snowden; A. L. Davis

2008-01-01

315

Dual linear polarization patch antenna array with high isolation  

Microsoft Academic Search

This paper describes the design and experimental results of a wideband dual linear polarization patch antenna array for PCS base stations. This antenna is designed to operate from 1.71 to 1.88 GHz, centered at 1.8 GHz. It is built as two sets of 2×1 antenna arrays working with linear polarization that is perpendicular to each other. The impedance bandwidth (return

K. L. Lau; K. M. Luk

2001-01-01

316

Polarization studies on the radiative recombination of highly charged bare ions  

SciTech Connect

The polarization of the emitted photons is studied for the radiative recombination of free electrons into the bound states of bare, highly charged ions. We apply density matrix theory in order to investigate how the photon polarization is affected if the incident electrons are themselves spin polarized. For K-shell electron capture, for instance, the linear polarization of the light, which is measured out of the reaction plane, is defined by the degree of polarization of the electrons and may be used as a tool for studying the polarization properties of the electron targets and/or the projectile ions. Detailed computations of the Stokes parameters of x-ray emission following the radiative recombination of bare uranium ions U{sup 92+} are carried out for a wide range of projectile energies and for different polarization states of the incident electrons.

Surzhykov, Andrey; Fritzsche, Stephan; Stoehlker, Thomas; Tachenov, Stanislav [Universitaet Kassel, Heinrich-Plett-Strasse 40, D-34132 Kassel, (Germany); Gesellschaft fuer Schwerionenforschung (GSI), D-64291 Darmstadt, (Germany)

2003-08-01

317

Broadband polarization rotator based on multi-order plasmon resonances and high impedance surfaces  

NASA Astrophysics Data System (ADS)

We experimentally investigate the electromagnetic (EM) responses of a broadband reflective polarization rotator under normal incidence. It is found that the rotator can generate multi-order plasmon resonances at three neighboring frequencies. At each frequency, the rotator behaves as a high impedance surface along one axis while as a metallic reflective surface along the other axis. Thus, a 180° phase difference is generated between the two orthogonal components of reflected waves. When the incident wave is polarized by 45° with respect to the symmetry axis of the rotator, the polarization of reflected waves is rotated by 90°. The designed rotator presents broadband properties. It can perform perfect 90° polarization rotation at three frequencies and maintains a polarization conversion efficiency greater than 56% in 2.0-3.5 GHz. The rotator provides a route to broadband polarization rotation and has application values in polarization control.

Feng, Mingde; Wang, Jiafu; Ma, Hua; Mo, Weidong; Ye, Hongjun; Qu, Shaobo

2013-08-01

318

Linear dynamic Kerr effect response of polar molecules in coupled ac and dc bias fields: Account of inertial effects via the J-diffusion model  

NASA Astrophysics Data System (ADS)

The dynamic Kerr response of noninteracting rigid polar linear molecules in superimposed strong dc and weak ac electric fields including inertial effects is investigated. The calculations are carried out for rotation in space in the context of linear response theory for the extended rotational (J-diffusion) model and extend the results of previous work. The birefringence spectrum is evaluated for typical values of the model parameters. Simple analytical equations for the spectrum are obtained for the limiting cases of rare and frequent collisions. The limit of frequent collisions allows us to compare the J-diffusion model with the Fokker-Planck model in the overdamped limit, where the inertial effects are neglected. It is found just as in dielectric relaxation that the birefringence relaxation times are very similar for the two models, but not identical. Also a crossover region between the low and high damping limits is exhibited by the Kerr effect relaxation time just as in Kramers' escape rate theory. In addition, this crossover region is shifted to higher friction parameter values when the applied dc field is increased. A comparison with previous theories is given.

Déjardin, P. M.

2000-05-01

319

High performance small-molecule organic thin film transistors  

NASA Astrophysics Data System (ADS)

The roadmap of developing microelectronics has a new branch: organic electronics. Organic electronics, which utilizes the electrical properties of organic materials in the active or passive layers, is an emerging technology that has received much attention. In conjunction with today's demands for new materials and devices, many technologies have emerged for developing organic electronics and consolidating applications and markets. An organic thin-film transistor is the essential device in this paradigm in addition to organic photodiodes and organic light emitting diodes. This thesis presents advances made in design and fabrication of organic thin-film transistors (OTFTs) using small-molecule organic semiconductors (pentacene, anthradithiophene, and their derivatives) as the active layer with record device performance. In this work OTFT test structures fabricated on oxidized silicon substrates were utilized to provide a convenient substrate, gate contact, and gate insulator for the processing and characterization of vapor-deposited organic materials and their transistors. By developing a gate dielectric treatment using silane coupling agents the performance and yield of pentacene OTFTs was improved and a field-effect mobility of larger than 2 cm2/V-s was achieved. Such device performance is comparable to a-Si:H TFTs and have the potential for electronic applications. In addition, the first direct photolithographic process for top contacts to pentacene OTFTs on oxidized silicon with an acceptable performance (a field-effect mobility of 0.3 cm2/V-s, an on/off current ratio of 10 7, and a subthreshold slope of 1 V/decade) was developed. The multiple layer photoresist process demonstrated the feasibility of creating source and drain metallic electrodes on vapor-deposited pentacene thin films with a resolution less than 10 mum. Subsequently, solution-processed OTFTs were then investigated and high performance transistors, with field-effect mobilities > 1 cm2/V-s and an on/off current ratio of 106.5, were developed with a processing-temperature of less than 90°C. This record performance was obtained with devices based on triethylsilylethynyl anthradithiophene (TES ADT) and triisopropylsilylethynyl pentacene (TIPS pentacene). Chemically modified source and drain contacts and gate dielectric were used to achieve such device performance, a performance that is still limited by the contacts. The studies were extended to several solution deposition methods which included blade coating, bar coating, dip casting, and spin casting. In addition to the above two materials, the design and characterization of four synthesized organic semiconductors with substituted functional groups was carried out. In this work it was found that the stacking of molecules with a large and two-dimensional pi-orbital overlap is crucial in determining its device performance and electron transport. The results of such molecular design approach offer great potential of obtaining suitable materials for large-area, low-cost electronic applications using low-temperature solution-processing technology. It is shown in this work that desirable performance can be achieved from both vapor-deposited and solution-processed OTFTs.

Kuo, Chung-Chen

320

Spectroscopic and dynamical studies of highly energized small polyatomic molecules  

SciTech Connect

The formyl radical and the acetylene molecule were chosen for these studies. The visible and fluorescence spectra of the formyl radical were recorded, and the spectral results are used as a basis to explain the electronic structure. Optical-optical double resonance studies of acetylene were recorded, and the spectral results are interpreted. The results of Zeeman and Stark anticrossing and quantum beat studies of acetylene are reported, and they provide an unusually detailed view of both Intersystem Crossing and Internal Conversion in small polyatomic molecules. 22 references are cited as resulting from Department of Energy sponsorship of this project.

Field, R.W.; Silbey, R.J.

1990-01-01

321

Intensity distribution near focal point of high aperture optical system formed by partly polarized light  

NASA Astrophysics Data System (ADS)

The paper presents the mathematical technique for calculation of three dimensional intensity distribution near a focal point of a high aperture optical system in case of quasi monochromatic partly polarized light. This technique is extension of the vector diffraction theory for high aperture optical systems. It is based on Huygens-Fresnel principle: spherical wave at an exit pupil is considered as a numerous set of elementary secondary partly polarized light sources. The total intensity is calculated as superposition of complex wave amplitudes taking into account polarization orientation, degree of polarization defined by Stokes parameters, orientation of detector aperture and coherence length of quasi-monochromatic light.

Borovytsky, Volodymyr; Chorna, Viktoriia

2009-08-01

322

Evaluation of Chromatographic Methods for Drug Products Containing Polar and Non-Polar Molecules Using Reversed Phase, Hydrophilic Interaction, and Ion Exchange Chromatography  

Microsoft Academic Search

In recent years the pharmaceutical industry has developed an increasing variety of complex double or triple combination drug therapies. Method development for these combination drug products is particularly challenging when the analytes have significantly different polarities, often requiring multiple chromatographic methods for each active component. An alternative to the commonly used practice of developing multiple reversed phase chromatographic methods for

Lance A. Rogers; Karen E. Crews; Susan G. Long; Kristin M. Patterson; John E. McCune

2009-01-01

323

High-resolution of positron annihilation on molecules  

Microsoft Academic Search

The use of positrons as atomic and molecular probes opens new avenues to understanding of atomic and molecular structure. The mechanism responsible for unexpectedly large positron annihilation rates exhibited by certain large molecules has remained an unsolved problem in this field for decades. To date, experimental attempts to gain insight into the cause of these large rates used thermal distributions

L. D. Barnes; S. J. Gilbert; C. M. Surko

2002-01-01

324

Real time, high resolution studies of protein adsorption and structure at the solid liquid interface using dual polarization interferometry  

NASA Astrophysics Data System (ADS)

A novel method for the analysis of thin biological films, called dual polarization interferometry (DPI), is described. This high resolution (<1 Å), laboratory-based technique allows the thickness and refractive index (density) of biological molecules adsorbing or reacting at the solid-liquid interface to be measured in real time (up to 10 measurements per second). Results from the adsorption of bovine serum albumin (BSA) on to a silicon oxynitride chip surface are presented to demonstrate how time dependent molecular behaviour can be examined using DPI. Mechanistic and structural information relating to the adsorption process is obtained as a function of the solution pH.

Freeman, Neville J.; Peel, Louise L.; Swann, Marcus J.; Cross, Graham H.; Reeves, Andrew; Brand, Stuart; Lu, Jian R.

2004-07-01

325

Relativistic Effects and Polarization in Three High-Energy Pulsar Models  

Microsoft Academic Search

We present the influence of the special relativistic effects of aberration and light-travel time delay on pulsar high-energy light curves and polarization characteristics predicted by three models: the two-pole caustic model, the outer gap model, and the polar cap model. Position angle curves and degree of polarization are calculated for the models and compared with the optical data on the

J. Dyks; Alice K. Harding; B. Rudak

2004-01-01

326

Studies of electron-molecule collisions on highly parallel computers  

SciTech Connect

The authors report on results of their studies of the cross sections for collisions of low-energy electrons with polyatomic molecules. These results are obtained using a multichannel extension of Schwinger`s variational principle and an implementation of key steps of the associated computational procedure on distributed-memory parallel computers. After a brief discussion of some relevant aspects of the formulation and of their parallel implementation, the authors present results from recent studies of electronic excitation by electron impact in several polyatomic molecules, including SiH{sub 4}, CF{sub 3}Cl, (CH{sub 3}){sub 2}CO, p-C{sub 6}H{sub 4}O{sub 2}, and the C{sub 5}H{sub 6} isomer propellane.

McKoy, V.; Winstead, C. [California Institute of Technology, Pasadena, CA (United States)

1993-12-01

327

Fusion with highly spin polarized HD and D sub 2  

SciTech Connect

This report discusses the following topics relating to inertial confinement with spin polarized hydrogen targets: low temperature implementation of mating a target to omega; dilution-refrigerator cold-entry and retrieval system; target shell tensile strength characterization at low temperatures; and proton and deuteron spin-lattice relaxation measurements in HD in the millikelvin temperature range. (LSP)

Honig, A.

1992-06-29

328

Fusion with highly spin polarized HD and D(2)  

NASA Astrophysics Data System (ADS)

This report discusses the following topics relating to inertial confinement with spin polarized hydrogen targets: low temperature implementation of mating a target to omega; dilution-refrigerator cold-entry and retrieval system; target shell tensile strength characterization at low temperatures; and proton and deuteron spin-lattice relaxation measurements in HD in the millikelvin temperature range.

Honig, A.

1992-06-01

329

Cosmic Microwave Background Polarization Detector with High Efficiency, Broad Bandwidth, and Highly Symmetric Coupling to Transition Edge Sensor Bolometers  

Microsoft Academic Search

We describe a prototype detector system designed for precise measurements of Cosmic Microwave Background polarization. The\\u000a design combines a quasi-optical polarization modulator, a metal feedhorn, a superconducting planar microwave circuit, and\\u000a a pair of transition-edge sensor (TES) bolometers operating at <100 mK. The circular feedhorn produces highly symmetric beams\\u000a with very low cross-polarization. The planar circuit preserves symmetry in coupling

T. Stevenson; D. Benford; C. Bennett; N. Cao; D. Chuss; K. Denis; W. Hsieh; A. Kogut; S. Moseley; J. Panek; G. Schneider; D. Travers; K. U-Yen; G. Voellmer; E. Wollack

2008-01-01

330

High-efficiency polarization-independent diffraction by transmission grating with a connecting layer  

NASA Astrophysics Data System (ADS)

We describe a novel transmission grating with a connecting layer to achieve high efficiency diffraction with polarization-independence. The grating duty cycle and period are optimized by modal method. Accurate grating depth and connecting layer thickness are optimized using rigorous coupled-wave analysis. High efficiencies of 99.21% for TE polarization and 99.12% for TM polarization can be achieved with the optimized grating parameters. Furthermore, the grating with a connecting layer can show efficiencies larger than 97% for both TE and TM polarizations within the given range of grating depth and connecting layer thickness, which will be significant for practical applications of such a high-efficiency polarization-independent grating with a connecting layer.

Wang, Bo; Lei, Liang; Chen, Li; Zhou, Jinyun

2013-02-01

331

High-performance optical fiber polarizers based on long-period gratings in birefringent optical fibers  

Microsoft Academic Search

We have demonstrated the feasibility of achieving high-performance fiber polarizers (insertion loss 30 dB), based on polarization mode dispersion in a long-period grating. Chirped operation with 100-nm bandwidth has also been achieved, showing the possibility of a broad-band device.

B. Ortega; L. Dong; W. F. Liu; J. P. de Sandro; L. Reekie; S. I. Tsypina; V. N. Bagratashvili; R. I. Laming

1997-01-01

332

A High-Isolation, Wideband and Dual-Linear Polarization Patch Antenna  

Microsoft Academic Search

The design of a dual-polarization stacked patch antenna to be used in GSM-UMTS base station arrays is presented. The patch shows a high matching level in a broadband and isolation between elements that make it a suitable radiating element for base station arrays. Moreover, the most relevant achievement of this element is the isolation between the two polarization ports of

Mariano Barba

2008-01-01

333

Interaction of NH(X 3Sigma) Molecules with Rubidium Atoms: Implications for Sympathetic Cooling and the Formation of Extremely Polar Molecules  

Microsoft Academic Search

The Rb-NH interaction is investigated as a prototype for interactions between alkali-metal atoms and stable molecules. For spin-aligned Rb and NH that interact on a quartet surface (4A''), the interaction is relatively weak, with a well depth of 0.078eV. However, there are also doublet surfaces of ion-pair character that are very much deeper (well depth 1.372eV). They may be important

Pavel Soldán; Jeremy M. Hutson

2004-01-01

334

The streptococcal M protein: a highly versatile molecule.  

PubMed

Interaction of the M-protein of group A Streptococcus (GAS) with its numerous host binding partners might assist the bacteria in evading host immune responses. Although the extensive diversity of this protein has been highlighted by different GAS typing schemes, most of the structural and functional information has been obtained from a limited number of types. Increasing numbers of epidemiological, clinical and biological reports suggest that the structure and function of the M protein is less conserved than previously thought. This review focuses on the known interactions between M proteins and host ligand proteins, emphasizing that our understanding of this well-studied molecule is fragmented. PMID:20347595

Smeesters, Pierre R; McMillan, David J; Sriprakash, Kadaba S

2010-03-27

335

Development of the ZJU polarized near-infrared high spectral resolution lidar  

NASA Astrophysics Data System (ADS)

Quantitative measurements of atmospheric aerosol optical properties are required for studies of the Earth's radiation budget and climate change. Taking advantage of the broad spectrum of the Cabannes-Brillouin scattering from atmospheric molecules, the high spectral resolution lidar (HSRL) technique employs a narrow spectral filter to reject the aerosol Mie scattering component in the lidar return signals. Therefore, an HSRL can directly measure the extinction and backscatter coefficient as well as the lidar ratio. Since the backscattering signal is proportional to 1/?4, it presents high requirements for the spectral filter to build a near-infrared HSRL. The atomic/molecular absorption filters are limited by the wavelength and it is also challenging for Fabry-Perot interferometers (FPI) due to their small field of view(FOV). The field-widened Michelson interferometer, which has a large FOV, is considered to be a good candidate for the spectral filter of near-infrared HSRL. A polarized near-infrared HSRL instrument, which employs a field-widened Michelson interferometer as the spectral filter, is under development at the Zhejiang University (ZJU), China. In this paper, the methodology and design process of the instrument will be described in detail. The capability of the HSRL in determining the properties of the atmosphere will be addressed. The retrieval of the aerosol optical properties, such as extinction-to-backscatter ratio and aerosol depolarization ratio, will be presented. Sensitivity of the aerosol retrieval to errors in characterizing the spectral filter will also be investigated.

Liu, Dong; Yang, Yongying; Cheng, Zhongtao; Huang, Hanlu; Zhang, Bo; Shen, Yibing

2013-09-01

336

FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): High Polarization Single Mode Photonic Crystal Microlaser  

NASA Astrophysics Data System (ADS)

Generally, dipole mode is a doubly degenerate mode. Theoretical calculations have indicated that the single dipole mode of two-dimensional photonic crystal single point defect cavity shows high polarization property. We present a structure with elongated lattice, which only supports a single y-dipole mode. With this structure we can eliminate the degeneracy, control the lasing action of the cavity and demonstrate the high polarization property of the single dipole mode. In our experiment, the polarization extinction ratio of the y-dipole mode is as high as 51:1.

Chen, Wei; Xing, Ming-Xin; Zhou, Wen-Jun; Liu, An-Jin; Zheng, Wan-Hua

2009-08-01

337

Metal-organic frameworks from chiral square-pyramidal copper(II) complexes: Enantiospecific inclusion and perfectly polar alignment of guest and host molecules  

SciTech Connect

The physical properties of [CuL{sup 1} {sub 2}(H{sub 2}O)] (1) and [CuL{sup 2} {sub 2}(H{sub 2}O)] (2) and preparation and crystal structures of the inclusion compounds 1.(P)-C{sub 2}H{sub 4}Br{sub 2}, 2.(M)-C{sub 2}H{sub 4}Br{sub 2}, 1.CH{sub 3}CN and 2.CH{sub 3}CN are described. HL{sup 1} and HL{sup 2} (H represents the dissociable phenolic proton) are the N,O-donor chiral reduced Schiff bases N-(2-hydroxy-5-nitrobenzyl)-(R)-{alpha}-methyl-benzylamine and N-(2-hydroxy-5-nitrobenzyl)-(S)-{alpha}-methylbenzylamine, respectively. All the compounds crystallize in the non-centrosymmetric space group C2. In the crystal lattice, the host [CuL {sup n} {sub 2}(H{sub 2}O)] (1 and 2) molecules connected by O-H...O and C-H...O interactions form perfectly polar two-dimensional networks. In these chiral and polar host frameworks, enantiospecific inclusion with polar ordering of the right-handed (P) and the left-handed (M) gauche form of 1,2-dibromoethane as well as polar alignment of acetonitrile molecules are observed. The host and guest molecules are linked by C-H...O interactions. The O-atoms of the nitro substituent on the ligands of 1 and 2 act as the acceptors in all these intermolecular O-H...O and C-H...O interactions. The structures reported in this work provide rare examples of enantiospecific trapping of the chiral rotamers of 1,2-dibromoethane as well as perfectly polar alignment of both guest and host molecules. - Graphical abstract: The square-pyramidal Cu(II) complexes [CuL {sup n} {sub 2}(H{sub 2}O)] with the bidentate HL {sup n} (HL{sup 1}=N-(2-hydroxy-5-nitrobenzyl)-(R)-{alpha}-methyl-benzylamine and HL{sup 2}=N-(2-hydroxy-5-nitrobenzyl)-(S)-{alpha}-methylbenzylamine) form 1:1 host-guest compounds with Br(CH{sub 2}){sub 2}Br and CH{sub 3}CN. The X-ray structures of these species reveal the enantiospecific confinement of the chiral rotamers of Br(CH{sub 2}){sub 2}Br and perfectly polar ordering of both host and guest molecules in the crystal lattice. The figure shows the polar alignments of (a) [CuL{sup 1} {sub 2}(H{sub 2}O)].(P)-C{sub 2}H{sub 4}Br{sub 2} and (b) [CuL{sup 2} {sub 2}(H{sub 2}O)].CH{sub 3}CN.

Muppidi, Vamsee Krishna [School of Chemistry, University of Hyderabad, Hyderabad 500 046 (India); Zacharias, Panthapally S. [School of Chemistry, University of Hyderabad, Hyderabad 500 046 (India); Pal, Samudranil [School of Chemistry, University of Hyderabad, Hyderabad 500 046 (India)], E-mail: spsc@uohyd.ernet.in

2007-01-15

338

High-order harmonic generation from two-center molecules: Time-profile analysis of nuclear contributions  

SciTech Connect

We solve the exact three-dimensional time-dependent Schroedinger equation for H{sub 2}{sup +} (with fixed nuclei) interacting with an intense laser pulse with an arbitrary oriented linear polarization. We find that at equilibrium internuclear distance, the ionization probability of H{sub 2}{sup +} is maximum for the parallel orientation of the molecule with respect to the laser polarization, and is minimum for the perpendicular orientation. The contribution of each nucleus to the harmonic spectrum is evaluated, so that interference effects between the two contributions are assessed unambiguously. We show that every half-cycle, high order harmonics are emitted by each nucleus when the electron wave packet returns for a recollision with both nuclei, and that the resulting harmonic emission is predominant for the nucleus that experiences the first recollision. In general, each nucleus emits both even and odd harmonics, but even harmonics are destroyed by interferences between contributions from each nucleus. In general, this destructive interference occurs over a large spread of harmonic orders, which depends on the angle between the molecular axis and the laser polarization.

Kamta, G. Lagmago; Bandrauk, A.D. [Laboratoire de Chimie Theorique, Faculte des Sciences, Universite de Sherbrooke, Sherbrooke, Quebec J1K 2R1 (Canada)

2004-07-01

339

Long-range interaction effects in a formation of dipole-bound anions induced by collisions of Rydberg atoms with polar molecules  

NASA Astrophysics Data System (ADS)

We report results of theoretical studies of dipole-bound anion formation reactions in collisions of polar molecules CH3NO2,CH3CN, and C3H4O3 with Rydberg atoms Cs(ns),Xe(nf), and Rb(nl) (l = 0, 3, and n ? 1). It is shown that the inclusion of the long-range interaction effects into the calculations of the Rydberg-covalent–ionic coupling terms is crucial for a reliable quantitative description of such processes. A particular attention is paid to the comparison of the results obtained with the calculations performed using previous models and with the experiment.

Lebedev, V. S.; Narits, A. A.

2013-09-01

340

High Energy Proton Ejection from Hydrocarbon Molecules Driven by Highly Efficient Field Ionization  

NASA Astrophysics Data System (ADS)

We report on the ejection of protons with surprisingly high kinetic energies up to 60 eV from a series of polyatomic hydrocarbon molecules exposed to Titanium-Sapphire laser pulses with moderate laser peak intensities of a few 1014 W/cm2. Using multi-particle coincidence imaging we are able to decompose the observed proton energy spectra into the contributions of individual fragmentation channels. It is shown that the molecules can completely fragment into bare atomic ions already at relatively low peak intensities, and that the protons are ejected in a concerted Coulomb explosion from unexpectedly high charge states. We propose that a thus far undescribed process, namely that enhanced ionization (EI) taking place at all C-H bonds in parallel, is responsible for the high charge states and high proton energies. The proposition is successfully tested by using (stretched) few-cycle pulses with a bandwidth limited duration as short as 4.3 fs, for which the C-H nuclear motion is too slow to reach the critical internuclear distance for EI.

Roither, S.; Xie, X.; Kartashov, D.; Zhang, L.; Schöffler, M.; Xu, H.; Iwasaki, A.; Okino, T.; Yamanouchi, K.; Baltuška, A.; Kitzler, M.

341

New materials research for high spin polarized current  

NASA Astrophysics Data System (ADS)

The author reports here a thorough investigation of structural and magnetic properties of Co2FeAl0.5Si0.5 Heusler alloy films, and the tunnel magnetoresistance effect for junctions with Co2FeAl0.5Si0.5 electrodes, spin injection into GaAs semiconductor from Co2FeAl0.5Si0.5, and spin filtering phenomena for junctions with CoFe2O4 ferrite barrier. It was observed that tunnel magnetoresistance ratio up to 832%(386%) at 9 K (room temperature), which corresponds to the tunnel spin polarization of 0.90 (0.81) for the junctions using Co2FeAl0.5Si0.5 Heusler electrodes by optimizing the fabrication condition. It was also found that the tunnel magnetoresistance ratio are almost the same between the junctions with Co2FeAl0.5Si0.5 Heusler electrodes on Cr buffered (1 0 0) and (1 1 0) MgO substrates, which indicates that tunnel spin polarization of Co2FeAl0.5Si0.5 for these two direction are almost the same. The next part of this paper is a spin filtering effect using a Co ferrite. The spin filtering effect was observed through a thin Co-ferrite barrier. The inverse type tunnel magnetoresistance ratio of -124% measured at 10 K was obtained. The inverse type magnetoresistance suggests the negative spin polarization of Co-ferrite barrier. The magnetoresistance ratio of -124% corresponds to the spin polarization of -0.77 by the Co-ferrite barrier. The last part is devoted to the spin injection from Co2FeAl0.5Si0.5 into GaAs. The spin injection signal was clearly obtained by three terminal Hanle measurement. The spin relaxation time was estimated to be 380 ps measured at 5 K.

Tezuka, Nobuki

2012-10-01

342

High Resolution Measures of Polarization and Color of Selected Lunar Areas.  

National Technical Information Service (NTIS)

High resolution observations of intensity, color (UBV) and polarization were obtained with scanning techniques for a number of lunar areas of special interest, including boundaries of some of the brightest and darkest lunar regions, certain Apollo landing...

J. S. Hall L. A. Riley

1972-01-01

343

High Chemical Diversity of Solvent Soluble Polar Fractions of the Tissint Shergottite  

NASA Astrophysics Data System (ADS)

Here we report on the chemical diversity of the polar fraction in the methanol extracts of different Tissint sample fractions (crust, bulk, olivine macrocrists, vitrifications) using high field ultrahigh-resolution mass spectrometry.

Schmitt-Kopplin, Ph.; Harir, M.; Hertkorn, N.; Chennaoui Aoudjehane, H.; Fernandes-Remolar, D. C.; Hinman, N.; Gabelica, Z.

2012-09-01

344

Engineering Very-High-n Polarized Rydberg States Using Tailored Half-Cycle-Pulse Sequences  

SciTech Connect

We show that strongly polarized very-high-n (n~600) potassium Rydberg atoms can be produced by manipulating lower-n (n~350) polarized atoms using a tailored sequence of ultrashort half-cycle pulses (HCPs). The protocol for this involves first a weak HCP that generates transient phase-space localization whereupon a second large HCP of opposite polarity excites the electron to a broad distribution of highly elongated states. This distribution is then refocused by a short periodic train of HCPs using the properties of (un)stable manifolds near fixed points in phase space.

Zhao, W. [Rice University; Mestayer, J. J. [Rice University; Lancaster, J. C. [Rice University; Dunning, F. B. [Rice University; Reinhold, Carlos O [ORNL; Yoshida, S. [Institute for Theoretical Physics, Vienna University of Technology, Austria; Burgdorfer, J. [Institute for Theoretical Physics, Vienna University of Technology, Austria

2005-10-01

345

A high-throughput screening fluorescence polarization assay for fatty acid adenylating enzymes in Mycobacterium tuberculosis  

PubMed Central

Mycobacterium tuberculosis, the etiological agent of tuberculosis (TB), encodes for an astonishing 34 fatty acid adenylating enzymes (FadDs), which play key roles in lipid metabolism. FadDs involved in lipid biosynthesis are functionally nonredundant and serve to link fatty acid and polyketide synthesis to produce some of the most architecturally complex natural lipids including the essential mycolic acids as well as the virulence-conferring phthiocerol dimycocerosates, phenolic glycolipids, and mycobactins. Here we describe the systematic development and optimization of a fluorescence polarization assay to identify small molecule inhibitors as potential antitubercular agents. We fluorescently labeled a bisubstrate inhibitor to generate a fluorescent probe/tracer, which bound with a KD of 245 nM to FadD28. Next, we evaluated assay performance by competitive binding experiments with a series of known ligands and assessed the impact of control parameters including incubation time, stability of the signal, temperature, and DMSO concentration. As a final level of validation the LOPAC1280™ library was screened in a 384-well plate format and the assay performed with a Z-factor of 0.75 demonstrating its readiness for high-throughput screening.

Grimes, Kimberly D.; Aldrich, Courtney C.

2011-01-01

346

A high-throughput screening fluorescence polarization assay for fatty acid adenylating enzymes in Mycobacterium tuberculosis.  

PubMed

Mycobacterium tuberculosis, the etiological agent of tuberculosis (TB), encodes for an astonishing 34 fatty acid adenylating enzymes (FadDs), which play key roles in lipid metabolism. FadDs involved in lipid biosynthesis are functionally nonredundant and serve to link fatty acid and polyketide synthesis to produce some of the most architecturally complex natural lipids including the essential mycolic acids as well as the virulence-conferring phthiocerol dimycocerosates, phenolic glycolipids, and mycobactins. Here we describe the systematic development and optimization of a fluorescence polarization assay to identify small molecule inhibitors as potential antitubercular agents. We fluorescently labeled a bisubstrate inhibitor to generate a fluorescent probe/tracer, which bound with a K(D) of 245 nM to FadD28. Next, we evaluated assay performance by competitive binding experiments with a series of known ligands and assessed the impact of control parameters including incubation time, stability of the signal, temperature, and DMSO concentration. As a final level of validation the LOPAC1280 library was screened in a 384-well plate format and the assay performed with a Z-factor of 0.75, demonstrating its readiness for high-throughput screening. PMID:21771578

Grimes, Kimberly D; Aldrich, Courtney C

2011-07-02

347

Highly parallel computational techniques for electron-molecule collisions  

SciTech Connect

In this paper, we will describe our methodology for implementing the calculation of low energy electron-molecule scattering cross sections on massively parallel computers. Our emphasis here will be on the adaptation of a problem in molecular quantum mechanics to parallel computation and on the performance achievable, and our hope is that some of the techniques described here will be of use to others who are contemplating the parallelization of similar computations. The present work updates and extends a previous account along similar lines; for a discussion of various computational methods for electron collisions and a survey of recent results obtained by those methods. In Section II, we summarize the theory behind our numerical method, showing how we arrive at working equations for the scattering amplitude beginning from Schroedinger`s equation. Section III discusses the parallel implementation of our method and associated issues. An illustrative example is presented in Section IV, and concluding remarks are offered in Section V. 37 refs., 3 figs.

Winstead, C.; McKoy, V. [California Institute of Technology, Pasadena, CA (United States)

1996-12-31

348

Spectroscopy, reaction, and photodissociation in highly vibrationally excited molecules. Technical progress report  

SciTech Connect

Highly vibrationally excited molecules often control the course of chemical reactions in the atmosphere, combustion, plasmas, and many other environments. The research described in this Progress Report uses laser excitation and interrogation techniques to study and control the dynamics of highly vibrationally excited molecules. In particular, they show that it is possible to unravel the details and influence the course of photodissociation and bimolecular reaction. The experiments use laser excitation of overtone vibrations to prepare highly vibrationally excited molecules, frequently with single quantum state resolution, and laser spectroscopy to monitor the subsequent behavior of the excited molecule. We have studied the vibrationally mediated photodissociation and the bond- and state-selected bimolecular reaction of highly vibrationally excited molecules. In the first process, one photon creates a highly excited molecule, a second photon from another laser dissociates it, and light from a third laser detects the population of individual product quantum states. This approach allows us to explore otherwise inaccessible regions of the ground and excited state potential energy surface and, by exciting to the proper regions of the surface, to control the breaking of a selected chemical bond. In the second process, the highly vibrationally excited molecule reacts with an atom formed either in a microwave discharge or by photolysis and another laser interrogates the products. We have used this approach to demonstrate mode- and bond-selected bimolecular reactions in which the initial excitation controls the subsequent chemistry. 30 refs., 8 figs.

Not Available

1991-12-31

349

Toward the Extension of High Order Harmonic Spectroscopy to Complex Molecules: Investigation of Aligned Hydrocarbons  

NASA Astrophysics Data System (ADS)

High-order harmonic generation is as a powerful tool for the study of molecular properties. Up to now this investigation tool has been confined to simple molecules, with a relatively high ionization potential, since ionization saturation hindered its exploitation to fragile molecules. In this work we show that such limitation can be overcome by using mid-IR ultrashort driving pulses; as prototypical molecules we considered hydrocarbons. Clear signatures of the highest occupied molecular orbital were found in the harmonic spectra generated in unsaturated aligned hydrocarbons like acetylene, ethylene, allene and 1,3-butadiene. Our findings demonstrate that high-order harmonic generation spectroscopy can be extended to complex molecular species.

Vozzi, C.; Torres, R.; Negro, M.; Brugnera, L.; Siegel, T.; Altucci, C.; Velotta, R.; Frassetto, F.; Villoresi, P.; Poletto, L.; De Silvestri, S.; Marangos, J. P.; Stagira, S.

350

High Sensitivity PEA System with Dual Polarity Pulse Generator  

NASA Astrophysics Data System (ADS)

The pulsed electroacoustic (PEA) method has been widely used to observe space charge distributions in various solid dielectric materials. The sensitivity of the conventional PEA system is around 1 C/m3. When the charge density is less than 1 C/m3, however, it is difficult to obtain an accurate result because the signal due to the Maxwell stress becomes comparable with the signal to be measured. The Maxwell stress is generated by applying the pulsed electric field to the dielectrics, and independent from the existence of either induced charges by dc bias voltage or internal charges. In order to eliminate the influence of the Maxwell stress, we have developed a new PEA system with a dual polarity pulse generator. The system achieved to measure space charge density around 0.03 C/m3.

Matsui, Kohei; Tanaka, Yasuhiro; Takada, Tatsuo; Fukao, Tadashi; Maeno, Takashi

351

Single molecule investigations of DNA looping using the tethered particle method and translocation by acto-myosin using polarized total internal reflection fluorescence microscopy  

NASA Astrophysics Data System (ADS)

Single molecule biophysics aims to understand biological processes by studying them at the single molecule level in real time. The proteins and nucleic acids under investigation typically exist in an aqueous environment within ˜ ten degrees of room temperature. These seemingly benign conditions are actually quite chaotic at the nanoscale, where single bio-molecules perform their function. As a result, sensitive experiments and statistical analyses are required to separate the weak single molecule signal from its background. Protein-DNA interactions were investigated by monitoring DNA looping events in tethered particle experiments. A new analysis technique, called the Diffusive hidden Markov method, was developed to extract kinetic rate constants from experimental data without any filtering of the raw data; a common step that improves the signal to noise ratio, but at the expense of lower time resolution. In the second system, translocation of the molecular motor myosin along its actin filament track was studied using polarized total internal reflection (polTIRF) microscopy, a technique that determines the orientation and wobble of a single fluorophore attached to the bio-molecule of interest. The range of resolvable angles was increased 4-fold to include a hemisphere of possible orientations. As a result, the handedness of actin filament twirling as it translocated along a myosin-coated surface was determined to be left-handed. The maximum time resolution of a polTIRF setup was increased 50-fold, in part by recording the arrival times and polarization state of single photons using a modified time-correlated single photon counting device. A new analysis, the Multiple Intensity Change Point algorithm, was developed to detect changes in molecular orientation and wobble using the raw time-stamped data with no user-defined bins or thresholds. The analysis objectively identified changes in the orientation of a bifunctional-rhodamine labeled calmodulin that was attached to a myosin V molecule translocating along an actin filament. Long intervals corresponding to stable positions between tilting motions of the lever arm during each step were routinely observed. Substeps in the cycle that preceded these long dwells were measured, but only occasionally most likely because of the low number of photons detected during these rapid events.

Beausang, John F.

352

Neuronal Polarity and the Kinesin Superfamily Proteins  

NSDL National Science Digital Library

Neurons are highly polarized cells, typically with a long axon and relatively short dendrites. A wealth of recent data has identified a number of signaling molecules that are involved in neuronal polarization. Kinesin superfamily proteins (KIFs) contribute to the establishment and maintenance of neuronal polarity by selectively transporting various proteins and vesicles to either the axon or dendrites. Now evidence is emerging that KIFs also play an important role in axonal formation, the initial event of neuronal polarization. In particular, KIF13B transports phosphatidylinositol (3,4,5)-trisphosphate, which, based on current hypotheses, is one of the most upstream molecules in the intracellular signaling cascades involved in axonal formation.

Takao Nakata (University of Tokyo;Department of Cell Biology and Anatomy REV); Nobutaka Hirokawa (University of Tokyo;Department of Cell Biology and Anatomy REV)

2007-02-06

353

High energy sources and materials: High-temperature molecules and molecular energy storage  

NASA Astrophysics Data System (ADS)

The objective of this research was the characterization of molecular species which are important because of (a) their occurrence in high-temperature environments, as for example in the vapor over refractory solids, and in combustion, flames, and propellant burning; (b) their relevance to clarification and/or extension of the basic theory of molecular properties. The molecules studied were usually highly reactive or metastable and often inaccessible by the usual gas-phase spectroscopic methods. They were therefore trapped in a solid matrix, usually neon or orgon, at 4 K and investigated by optical and electron-spin-resonance (ESR) spectroscopies. This isolation procedure is known to produce only small perturbations and to yield information pertinent to the gas-phase species. The species studied included boron and bromine atoms, methylene radicals, diatomic boron, beryllium hydroxide, diatomic chlorine anion, carbonyl silene, diazasilene, the first-row transition-metal mono, di, and trifluorides and their corresponding hydrides and oxides, and a few rare-earth hydrides and fluorides. Vibrational frequencies, electronic transitions, g factors, spin-rotation constants, hyperfine coupling constants, zero-field-splittings, ground-state multiplicities, and perhaps some information about structure, were obtained. The molecules contained from one to seven unpaired electrons.

Weltner, W., Jr.

1980-10-01

354

High-Field Dynamic Nuclear Polarization for Solid and Solution Biological NMR  

PubMed Central

Dynamic nuclear polarization (DNP) results in a substantial nuclear polarization enhancement through a transfer of the magnetization from electrons to nuclei. Recent years have seen considerable progress in the development of DNP experiments directed towards enhancing sensitivity in biological nuclear magnetic resonance (NMR). This review covers the applications, hardware, polarizing agents, and theoretical descriptions that were developed at the Francis Bitter Magnet Laboratory at Massachusetts Institute of Technology for high-field DNP experiments. In frozen dielectrics, the enhanced nuclear polarization developed in the vicinity of the polarizing agent can be efficiently dispersed to the bulk of the sample via 1H spin diffusion. This strategy has been proven effective in polarizing biologically interesting systems, such as nanocrystalline peptides and membrane proteins, without leading to paramagnetic broadening of the NMR signals. Gyrotrons have been used as a source of high-power (5–10 W) microwaves up to 460 GHz as required for the DNP experiments. Other hardware has also been developed allowing in situ microwave irradiation integrated with cryogenic magic-angle-spinning solid-state NMR. Advances in the quantum mechanical treatment are successful in describing the mechanism by which new biradical polarizing agents yield larger enhancements at higher magnetic fields. Finally, pulsed methods and solution experiments should play a prominent role in the future of DNP.

Barnes, A.B.; Paepe, G. De; van der Wel, P.C.A.; Hu, K.-N.; Joo, C.-G.; Bajaj, V.S.; Mak-Jurkauskas, M.L.; Sirigiri, J.R.; Herzfeld, J.; Temkin, R.J.; Griffin, R.G.

2008-01-01

355

Tunable high-power high-brightness linearly polarized vertical-external-cavity surface-emitting lasers  

NASA Astrophysics Data System (ADS)

We report on the development and the demonstration of tunable high-power high-brightness linearly polarized vertical-external-cavity surface-emitting lasers (VECSELs). A V-shaped cavity, in which the antireflection-coated VECSEL chip (active mirror) is located at the fold, and a birefringent filter are employed to achieve a large wavelength tuning range. Multiwatt cw linearly polarized TEM00 output with a 20 nm tuning range and narrow linewidth is demonstrated at room temperature.

Fan, Li; Fallahi, Mahmoud; Murray, James T.; Bedford, Robert; Kaneda, Yushi; Zakharian, Aramis R.; Hader, Jörg; Moloney, Jerome V.; Stolz, Wolfgang; Koch, Stephan W.

2006-01-01

356

Probe single cyanine dye molecules' photo isomerization.  

NASA Astrophysics Data System (ADS)

Cyanine dyes are interested in the photosensitization, nonlinear optics, and their photophysical and photochemical behaviors. In particular, cyanine molecules, like DiI, plays an important role in single molecule fluorescence investigations. The high photo-stability, good QE, and low inter-system crossing rates, make it an good example for the single molecule investigations. We present the single molecule fluorescence investigation on the DiI molecules. In the investigation, we observe some (but not all) molecules exhibits reversible and quasi-stepwise polarization change. The decay dynamics is also changed correspondingly. Clear on-off blinking behaviors indicate the change in polarization from a single molecule, rather than the background noise, and we speculate it as the photo isomerization of the dye molecule. More detail analysis indicates some isomerization occurred at the singlet excited states, and it takes longer timescale (> ms) than expected.

Chen, Zih-Hao; Lee, Chang-Yeh; Lee, Chao-Kuei; Chuang, Yu-Tsu; Hsu, Jui-Hung

2006-03-01

357

Effect of photon-assisted tunneling through the leads on spin current polarization in ac-driven quantum dot molecules  

NASA Astrophysics Data System (ADS)

A new scheme for realizing spin pumping and spin filtering has been recently proposed using an ac-driven double quantum dot in the Coulomb blockade regime. Using a master equation approach for the density matrix, it was shown^1 that the spin polarization of the current through the system can be controlled by tuning the parameters (amplitude and frequency) of the ac-field. In the present work we extend our previous model to include photon-assisted tunneling through the contact barriers. This introduces new features in the current due to absorption and emission processes affecting the spin polarization of the current. We discuss these new features, their dependence on the ac-field parameters and the effects on the robustness of the proposed device as a spin pump and spin filter. In particular, we find that the spin filtering property depends strongly on the intensity of the applied ac field. The effect of photoassisted cotunneling on the spin current polarization will also be discussed.^ 1E.Cota, R. Aguado and G. Platero, Phys. Rev. Lett. 94, 107202 (2005)

Cota, Ernesto; Sanchez, Rafael; Aguado, Ramon; Platero, Gloria

2006-03-01

358

High Brightness and High Polarization Electron Source for Spin-LEEM  

NASA Astrophysics Data System (ADS)

A point-like emission mechanism is required for a GaAs polarized electron source to produce an electron beam with high brightness. This is realized by changing the direction of injection laser from a front-side to a back-side of the photocathode. Based on this concept, a 20 keV gun (JPES-1) was constructed and a transmission photocathode including an active layer of a GaAs-GaAsP superlattice was installed. It produced a laser spot diameter as small as 1.3 ?m for the 760~810 nm laser wavelength, and the brightness of ~2×107 A.cm-2.sr-1 corresponding to a reduced brightness of ~1.0×107 A.cm-2.sr-1.V-1 was obtained for an extracted current of 5.3 ?A. This brightness is still smaller than those of W-field-emitters, but one order of magnitude higher than those of LaB6 emitters. The peak polarization of ~90% was achieved at the same time by the photocathode which has an inserted GaAs thin layer between the GaAsP substrate and the GaAaP buffer layer. It demonstrated that the strain-control of the GaAsP buffer layer is indispensable to achieve the highest polarization. The charge density lifetime of 1.8×108 C/cm2 was observed for an extracted current of ~3 ?A. The second gun system (JPES-2) was already constructed and mounted to a LEEM apparatus operated at OECU.

Nakanishi, T.; Yamamoto, N.; Mano, A.; Nakagawa, Y.; Konomi, T.; Yamamoto, M.; Okumi, S.; Jin, X.; Ujihara, T.; Takeda, Y.; Ohshima, T.; Kohashi, T.; Yasue, T.; Koshikawa, T.; Saka, T.; Kato, T.

2009-08-01

359

High Brightness and High Polarization Electron Source for Spin-LEEM  

SciTech Connect

A point-like emission mechanism is required for a GaAs polarized electron source to produce an electron beam with high brightness. This is realized by changing the direction of injection laser from a front-side to a back-side of the photocathode. Based on this concept, a 20 keV gun (JPES-1) was constructed and a transmission photocathode including an active layer of a GaAs-GaAsP superlattice was installed. It produced a laser spot diameter as small as 1.3 {mu}m for the 760{approx}810 nm laser wavelength, and the brightness of {approx}2x10{sup 7} A{center_dot}cm{sup -2}{center_dot}sr{sup -1} corresponding to a reduced brightness of {approx}1.0x10{sup 7} A{center_dot}cm{sup -2}{center_dot}sr{sup -1}{center_dot}V{sup -1} was obtained for an extracted current of 5.3 {mu}A. This brightness is still smaller than those of W-field-emitters, but one order of magnitude higher than those of LaB{sub 6} emitters. The peak polarization of {approx}90% was achieved at the same time by the photocathode which has an inserted GaAs thin layer between the GaAsP substrate and the GaAaP buffer layer. It demonstrated that the strain-control of the GaAsP buffer layer is indispensable to achieve the highest polarization. The charge density lifetime of 1.8x10{sup 8} C/cm{sup 2} was observed for an extracted current of {approx}3 {mu}A. The second gun system (JPES-2) was already constructed and mounted to a LEEM apparatus operated at OECU.

Nakanishi, T.; Yamamoto, N.; Mano, A.; Nakagawa, Y.; Konomi, T.; Yamamoto, M.; Okumi, S. [Graduate School of Science, Nagoya University, Nagoya 464-8602 (Japan); Jin, X.; Ujihara, T.; Takeda, Y. [Graduate School of Engineering, Nagoya University, Nagoya 464-8601 (Japan); Ohshima, T.; Kohashi, T. [Central Research Laboratory, Hitachi Ltd. Tokyo, 185-8601 (Japan); Yasue, T.; Koshikawa, T. [Fundamental Electronics Research Center, Osaka Electro-Communication University, Osaka 572-8530 (Japan); Saka, T. [Daido Institute of Technology, Nagoya 457-8531 (Japan); Kato, T. [Daido Steel Co. Ltd., Nagoya 457-8531 (Japan)

2009-08-04

360

3C 286: a bright, compact, stable, and highly polarized calibrator for millimeter-wavelength observations  

NASA Astrophysics Data System (ADS)

Context. Several millimeter and submillimeter facilities with linear polarization observing capabilities have started operating during the last years. These facilities, as well as other previous millimeter telescopes and interferometers, require bright and stable linear polarization calibrators to calibrate new instruments and to monitor their instrumental polarization. The current limited number of adequate calibrators implies difficulties in the acquisition of these calibration observations. Aims: Looking for additional linear polarization calibrators in the millimeter spectral range, we started monitoring 3C 286 in mid-2006. This source is a standard and highly stable polarization calibrator for radio observations. Methods: Here we present the 3 mm and 1 mm monitoring observations obtained between September 2006 and January 2012 with the XPOL polarimeter on the IRAM 30 m Millimeter Telescope. Results: Our observations show that 3C 286 is a bright source of constant total flux with 3 mm flux density S3 mm = (0.91 ± 0.02) Jy. The 3 mm linear polarization degree (p3 mm = [13.5 ± 0.3] %) and polarization angle (?3 mm = [37.3 ± 0.8] °, expressed in the equatorial coordinate system) were also constant during the time span of our observations. Although with poorer time sampling and signal-to-noise ratio, our 1 mm observations of 3C 286 are also reproduced by a constant source of 1 mm flux density (S1 mm = [0.30 ± 0.03] Jy), polarization fraction (p1 mm = [14.4 ± 1.8] %), and polarization angle (?1 mm = [33.1 ± 5.7] °). Conclusions: This, together with the previously known compact structure of 3C 286 - extended by ~3.5'' in the sky - allow us to propose 3C 286 as a new calibrator for both single-dish and interferometric polarization observations at 3 mm, and possibly at shorter wavelengths.

Agudo, I.; Thum, C.; Wiesemeyer, H.; Molina, S. N.; Casadio, C.; Gómez, J. L.; Emmanoulopoulos, D.

2012-05-01

361

Quark Recombination Model for Spin Polarization in High Energy Inclusive Hadron Reactions  

NASA Astrophysics Data System (ADS)

We study the polarizations and the analyzing powers in high energy inclusive hadron reactions based on the quark recombination (QRC) mechanism. The QRC model reproduces the empirical rule of DeGrand and Miettinen with a relativistic description for the parton-parton interaction. We apply the QRC model to the polarizations of various hadron production processes and demonstrate its success by comparing with experiment. We discuss the importance of relativistic effects in the formulation of the quark recombination process and their significance with regard to spin polarization phenomena in hadron reactions together with quark momentum distributions in hadrons.

Yamamoto, Y.; Kubo, K.; Toki, H.

1997-07-01

362

High performance, large cross-section S-bender for neutron polarization  

NASA Astrophysics Data System (ADS)

An 80 mm long polarizing S-bender with a large cross-section of 30×100 mm2 for the instrument MIRA at the FRM II has been simulated, built and tested. The results of the experiment show for the wavelength of 4.4 Å a homogenous polarization of more than 98% across the bender cross-section and a high transmission of above 65% of the spin up component of the neutron beam. The bender design has the advantage of delivering the polarized beam in the direction of the incoming beam.

Krist, Th.; Rucker, F.; Brandl, G.; Georgii, R.

2013-01-01

363

The effect of surface chemical functional groups on the adsorption and desorption of a polar molecule, acetone, from a model carbonaceous surface, graphite  

Microsoft Academic Search

The role of surface chemical heterogeneity in adsorption on a model carbonaceous surface (highly oriented pyrolitic graphite, HOPG) was investigated by temperature programmed desorption of acetone, a representative polar volatile organic compound. It was observed that oxygen-containing functional groups exist on air cleaved HOPG. The presence of surface functional groups reduces the binding energy, while increasing the uptake kinetics at

S. Kwon; R. Vidic; E. Borguet

2003-01-01

364

ABSOLUTE MEASUREMENT OF THE POLARIZATION OF HIGH ENERGY PROTON BEAMS AT RHIC  

SciTech Connect

The spin physics program at the Relativistic Heavy Ion Collider (RHIC) requires knowledge of the beam polarization to better than 5%. Such a goal is made the more difficult by the lack of knowledge of the analyzing power of high energy nuclear physics processes. To overcome this, a polarized hydrogen jet target was constructed and installed at one intersection region in RHIC where it intersects both beams and utilizes the precise knowledge of the jet atomic hydrogen beam polarization to measure the analyzing power in proton-proton elastic scattering in the Nuclear Coulomb Interference (CNI) region at the prescribed RHIC proton beam energy. The reverse reaction is used to assess the absolute beam polarization. Simultaneous measurements taken with fast high statistics polarimeters that measure the p-Carbon elastic scattering process also in the CNI region use the jet results to calibrate the latter.

MAKDISI,Y.; BRAVAR, A. BUNCE, G. GILL, R.; HUANG, H.; ET AL.

2007-06-25

365

High-efficiency white OLEDs based on small molecules  

NASA Astrophysics Data System (ADS)

Eastman Kodak Company and SANYO Electric Co., Ltd. recently demonstrated a 15" full-color, organic light-emitting diode display (OLED) using a high-efficiency white emitter combined with a color-filter array. Although useful for display applications, white emission from organic structures is also under consideration for other applications, such as solid-state lighting, where high efficiency and good color rendition are important. By incorporating adjacent blue and orange emitting layers in a multi-layer structure, highly efficient, stable white emission has been attained. With suitable host and dopant combinations, a luminance yield of 20 cd/A and efficiency of 8 lm/W have been achieved at a drive voltage of less than 8 volts and luminance level of 1000 cd/m2. The estimated external efficiency of this device is 6.3% and a high level of operational stability is observed. To our knowledge, this is the highest performance reported so far for white organic electroluminescent devices. We will review white OLED technology and discuss the fabrication and operating characteristics of these devices.

Hatwar, Tukaram K.; Spindler, Jeffrey P.; Ricks, M. L.; Young, Ralph H.; Hamada, Yuuhiko; Saito, N.; Mameno, Kazunobu; Nishikawa, Ryuji; Takahashi, Hisakazu; Rajeswaran, G.

2004-02-01

366

Automated High Resolution Optical Mapping Using Arrayed, Fluid-Fixed DNA Molecules  

NASA Astrophysics Data System (ADS)

New mapping approaches construct ordered restriction maps from fluorescence microscope images of individual, endonuclease-digested DNA molecules. In optical mapping, molecules are elongated and fixed onto derivatized glass surfaces, preserving biochemical accessibility and fragment order after enzymatic digestion. Measurements of relative fluorescence intensity and apparent length determine the sizes of restriction fragments, enabling ordered map construction without electrophoretic analysis. The optical mapping system reported here is based on our physical characterization of an effect using fluid flows developed within tiny, evaporating droplets to elongate and fix DNA molecules onto derivatized surfaces. Such evaporation-driven molecular fixation produces well elongated molecules accessible to restriction endonucleases, and notably, DNA polymerase I. We then developed the robotic means to grid DNA spots in well defined arrays that are digested and analyzed in parallel. To effectively harness this effect for high-throughput genome mapping, we developed: (i) machine vision and automatic image acquisition techniques to work with fixed, digested molecules within gridded samples, and (ii) Bayesian inference approaches that are used to analyze machine vision data, automatically producing high-resolution restriction maps from images of individual DNA molecules. The aggregate significance of this work is the development of an integrated system for mapping small insert clones allowing biochemical data obtained from engineered ensembles of individual molecules to be automatically accumulated and analyzed for map construction. These approaches are sufficiently general for varied biochemical analyses of individual molecules using statistically meaningful population sizes.

Jing, Junping; Reed, Jason; Huang, John; Hu, Xinghua; Clarke, Virginia; Edington, Joanne; Housman, Dan; Anantharaman, Thomas S.; Huff, Edward J.; Mishra, Bud; Porter, Brett; Shenker, Alexander; Wolfson, Estarose; Hiort, Catharina; Kantor, Ron; Aston, Christopher; Schwartz, David C.

1998-07-01

367

High-definition vertically aligned liquid crystal microdisplays using a circularly polarized light  

NASA Astrophysics Data System (ADS)

A high-definition vertically aligned liquid crystal (LC) microdisplay exhibits a excellent contrast ratio, but its fringing field effect splits the bright state unevenly and leads to a very slow response time. By utilizing a circularly polarized light instead of conventional linearly polarized light, we have overcome the long-standing problems of poor sharpness, low brightness, and slow response time. Confirming computer simulations agree with the experimental results well. This approach can be applied to both reflective and transmissive LC microdisplays.

Fan-Chiang, Kuan-Hsu; Chen, Shu-Hsia; Wu, Shin-Tson

2005-07-01

368

Physiological Ecology of Mesozoic Polar Forests in a High CO2 Environment  

Microsoft Academic Search

Fossils show that coniferous forests extended into polar regions during the Mesozoic, a time when models and independent palaeo-CO2 indicators suggest that the atmospheric CO2 concentration was at least double that of the present day. Consequently, such polar forests would have experienced high CO2 interacting with an extreme variation in light. Here we describe an experiment investigating this plant-environment interaction

D. J. B EERLING; C. P. O SBORNE

2002-01-01

369

High-intensity, high-brightness polarized and unpolarized beam production in charge-exchange collisions  

SciTech Connect

Basic limitations on the high-intensity H{sup -} ion beam production were experimentally studied in charge-exchange collisions of the neutral atomic hydrogen beam in the Na-vapour jet ionizer cell. These studies are the part of the polarized source upgrade (to 10 mA peak current and 85% polarization) project for RHIC. In the source the atomic hydrogen beam of a 5-10 keV energy and total (equivalent) current up to 5 A is produced by neutralization of proton beam in pulsed hydrogen gas target. Formation of the proton beam (from the surface of the plasma emitter with a low transverse ion temperature {approx}0.2 eV) is produced by four-electrode spherical multi-aperture ion-optical system with geometrical focusing. The hydrogen atomic beam intensity up to 1.0 A/cm{sup 2} (equivalent) was obtained in the Na-jet ionizer aperture of a 2.0 cm diameter. At the first stage of the experiment H-beam with 36 mA current, 5 keV energy and {approx}1.0 cm {center_dot} mrad normalized emittance was obtained using the flat grids and magnetic focusing.

Zelenski, A.; Ritter, J.; Zubets, V.; Steski, D.; Atoian, G.; Davydenko, V.; Ivanov, A.; Kolmogorov, A.

2011-03-28

370

High precision fabrication of polarization insensitive resonant grating filters  

NASA Astrophysics Data System (ADS)

Resonant subwavelength gratings have been designed and fabricated as wavelength-specific reflectors for application as a rotary position encoder utilizing ebeam based photolithography. The first grating design used a two-dimensional layout to provide polarization insensitivity with separate layers for the grating and waveguide. The resulting devices had excellent pattern fidelity and the resonance peaks and widths closely matched the expected results. Unfortunately, the gratings were particularly angle sensitive and etch depth errors led to shifts in the center wavelength of the resonances. A second design iteration resulted in a double grating period to reduce the angle sensitivity as well as different materials and geometry; the grating and waveguide being the same layer. The inclusion of etch stop layers provided more accurate etch depths; however, the tolerance to changes in the grating duty cycle was much tighter. Results from these devices show the effects of small errors in the pattern fidelity. The fabrication process flows for both iterations of devices will be reviewed as well as the performance of the fabricated devices. A discussion of the relative merits of the various design choices provides insight into the importance of fabrication considerations during the design stage.

Boye, R. R.; Peters, D. W.; Wendt, J. R.; Samora, S.; Stevens, J.; Shul, R. J.; Hunker, J.; Kellogg, R. A.; Kemme, S. A.

2012-02-01

371

High circular polarization ratios in radar scattering from geologic targets  

NASA Astrophysics Data System (ADS)

We examine and model the occurrence of circular polarization ratio (CPR or ?c) values greater than unity in terrestrial and planetary radar observations as a guide to the range of associated surface morphology. Lunar crater deposits exhibit maximum ?c values at 12.6 and 70-cm wavelength of 2 to 3. CPR values for Maxwell Montes on Venus range up to about 1.5 at 12.6-cm wavelength. Echoes from SP Flow in Arizona exhibit ?c up to 2 at 24-cm wavelength. Scattering from rock edges and cracks (dipole-like) produces ?c of unity for single scattering and up to about 2 for multiple reflections. Scattering from natural corner reflectors (dihedrals) formed by pairs of rock facets can yield an average ?c of 3-4, but likely requires non-random or scale-limited surface roughness properties in order to dominate the observed echo. The dihedral mechanism is required to satisfy the highest lunar ?c observations, while echoes from SP Flow and Maxwell Montes could be explained by just the dipole mechanism. The dihedral scenario requires rocky facets on scales many times the radar wavelength, which the blocks at SP Flow (and the unknown surface texture of Maxwell) may not provide. The random dipole model is less demanding in terms of structures and scales, and likely increases the CPR of lunar or asteroid regoliths through scattering from and between rocks.

Campbell, Bruce A.

2012-06-01

372

RHIC: The World's First High-Energy, Polarized-Proton Collider (423rd Brookhaven Lecture)  

SciTech Connect

The Relativistic Heavy Ion Collider (RHIC) at BNL has been colliding polarized proton at a beam energy of 100 billion electron volts (GeV) since 2001. In addition to reporting upon the progress of RHIC polarized-proton program, this talk will focus upon the mechanisms that cause the beam to depolarize and the strategies developed to overcome this. As the world first polarized-proton collider, RHIC is designed to collide polarized protons up to an energy of 250 GeV, thereby providing an unique opportunity to measure the contribution made by the gluon to a proton's spin and to study the spin structure of proton. Unlike other high-energy proton colliders, however, the challenge for RHIC is to overcome the mechanisms that cause partial or total loss of beam polarization, which is due to the interaction of the spin vector with the magnetic fields. In RHIC, two Siberian snakes have been used to avoid these spin depolarizing resonances, which are driven by vertical closed-orbit distortion and vertical betatron oscillations. As a result, polarized-proton beams have been accelerated to 100 GeV without polarization loss, although depolarization has been observed during acceleration from 100 GeV to 205 GeV.

Bai, Mei (Collider-Accelerator Department)

2007-03-28

373

RHIC: The World's First High-Energy, Polarized-Proton Collider (423rd Brookhaven Lecture)  

ScienceCinema

The Relativistic Heavy Ion Collider (RHIC) at BNL has been colliding polarized proton at a beam energy of 100 billion electron volts (GeV) since 2001. In addition to reporting upon the progress of RHIC polarized-proton program, this talk will focus upon the mechanisms that cause the beam to depolarize and the strategies developed to overcome this. As the world first polarized-proton collider, RHIC is designed to collide polarized protons up to an energy of 250 GeV, thereby providing an unique opportunity to measure the contribution made by the gluon to a proton's spin and to study the spin structure of proton. Unlike other high-energy proton colliders, however, the challenge for RHIC is to overcome the mechanisms that cause partial or total loss of beam polarization, which is due to the interaction of the spin vector with the magnetic fields. In RHIC, two Siberian snakes have been used to avoid these spin depolarizing resonances, which are driven by vertical closed-orbit distortion and vertical betatron oscillations. As a result, polarized-proton beams have been accelerated to 100 GeV without polarization loss, although depolarization has been observed during acceleration from 100 GeV to 205 GeV.

374

Polarization of high-energy emission in a pulsar striped wind  

NASA Astrophysics Data System (ADS)

Recent observations of the polarization of the optical pulses from the Crab pulsar motivated detailed comparative studies of the emission predicted by the polar cap, the outer gap and the two-pole caustics models. In this work, we study the polarization properties of the synchrotron emission emanating from the striped wind model. We use an explicit asymptotic solution for the large-scale field structure related to the oblique split monopole and valid for the case of an ultra-relativistic plasma. This is combined with a crude model for the emissivity of the striped wind and of the magnetic field within the dissipating stripes themselves. We calculate the polarization properties of the high-energy pulsed emission and compare our results with optical observations of the Crab pulsar. The resulting radiation is linearly polarized. In the off-pulse region, the electric vector lies in the direction of the projection on the sky of the rotation axis of the pulsar, in good agreement with the data. Other properties such as a reduced degree of polarization and a characteristic sweep of the polarization angle within the pulses are also reproduced.

Pétri, Jérôme; Kirk, John

2008-02-01

375

Polarization of high-energy emission in a pulsar striped wind  

SciTech Connect

Recent observations of the polarization of the optical pulses from the Crab pulsar motivated detailed comparative studies of the emission predicted by the polar cap, the outer gap and the two-pole caustics models. In this work, we study the polarization properties of the synchrotron emission emanating from the striped wind model. We use an explicit asymptotic solution for the large-scale field structure related to the oblique split monopole and valid for the case of an ultra-relativistic plasma. This is combined with a crude model for the emissivity of the striped wind and of the magnetic field within the dissipating stripes themselves. We calculate the polarization properties of the high-energy pulsed emission and compare our results with optical observations of the Crab pulsar. The resulting radiation is linearly polarized. In the off-pulse region, the electric vector lies in the direction of the projection on the sky of the rotation axis of the pulsar, in good agreement with the data. Other properties such as a reduced degree of polarization and a characteristic sweep of the polarization angle within the pulses are also reproduced.

Petri, Jerome; Kirk, John [Max-Planck-Institut fuer Kernphysik, Saupfercheckweg 1, 69117 Heidelberg (Germany)

2008-02-27

376

Polarization properties of dye-based random lasers  

NASA Astrophysics Data System (ADS)

We present the first systematic study on the emission polarization of coherent random lasing (RL). Employing a single-shot spectro-polarimeter the complete polarization state and the degree of polarization could be recovered for individual RL modes. It turned out that the polarization of RL modes is strongly dependent on the pump polarization, which can be explained with the dipolar nature of the dye molecules. Furthermore, by using a highly viscous solvent for the laser-dye and a linear pump polarization, it was possible to force all random-lasing modes into just the same linear polarization.

Knitter, Sebastian; Kues, Michael; Fallnich, Carsten

2013-03-01

377

Development of a high average current polarized electron source with long cathode operational lifetime  

SciTech Connect

Substantially more than half of the electromagnetic nuclear physics experiments conducted at the Continuous Electron Beam Accelerator Facility of the Thomas Jefferson National Accelerator Facility (Jefferson Laboratory) require highly polarized electron beams, often at high average current. Spin-polarized electrons are produced by photoemission from various GaAs-based semiconductor photocathodes, using circularly polarized laser light with photon energy slightly larger than the semiconductor band gap. The photocathodes are prepared by activation of the clean semiconductor surface to negative electron affinity using cesium and oxidation. Historically, in many laboratories worldwide, these photocathodes have had short operational lifetimes at high average current, and have often deteriorated fairly quickly in ultrahigh vacuum even without electron beam delivery. At Jefferson Lab, we have developed a polarized electron source in which the photocathodes degrade exceptionally slowly without electron emission, and in which ion back bombardment is the predominant mechanism limiting the operational lifetime of the cathodes during electron emission. We have reproducibly obtained cathode 1/e dark lifetimes over two years, and 1/e charge density and charge lifetimes during electron beam delivery of over 2?105???C/cm2 and 200 C, respectively. This source is able to support uninterrupted high average current polarized beam delivery to three experimental halls simultaneously for many months at a time. Many of the techniques we report here are directly applicable to the development of GaAs photoemission electron guns to deliver high average current, high brightness unpolarized beams.

C. K. Sinclair; P. A. Adderley; B. M. Dunham; J. C. Hansknecht; P. Hartmann; M. Poelker; J. S. Price; P. M. Rutt; W. J. Schneider; M. Steigerwald

2007-02-01

378

Integration of high k and polar oxides with gallium nitride  

Microsoft Academic Search

GaN-based transistors offer great promise in high power high frequency applications. Recent understanding of the role of surface effects in AlGaN\\/GaN based high electron mobility transistor (HEMT) structures and the resulting ability to control these effects has led to the demonstration of very high power densities and near ideal power added efficiencies. Even with these advances, gate leakage is a

Peter James Hansen

2004-01-01

379

Burn depth determination using high-speed polarization-sensitive Mueller optical coherence tomography with continuous polarization modulation  

NASA Astrophysics Data System (ADS)

National Health Interview Survey (NHIS) estimates more than 1.1 million burn injuries per year in the United States, with nearly 15,000 fatalities from wounds and related complications. An imaging modality capable of evaluating burn depths non-invasively is the polarization-sensitive optical coherence tomography. We report on the use of a high-speed, fiber-based Mueller-matrix OCT system with continuous source-polarization modulation for burn depth evaluation. The new system is capable of imaging at near video-quality frame rates (8 frames per second) with resolution of 10 ?m in biological tissue (index of refraction: 1.4) and sensitivity of 78 dB. The sample arm optics is integrated in a hand-held probe simplifying the in vivo experiments. The applicability of the system for burn depth determination is demonstrated using biological samples of porcine tendon and porcine skin. The results show an improved imaging depth (1 mm in tendon) and a clear localization of the thermally damaged region. The burnt area determined from OCT images compares well with the histology, thus proving the system's potential for burn depth determination.

Todorovi?, Miloš; Ai, Jun; Pereda Cubian, David; Stoica, George; Wang, Lihong

2006-03-01

380

Rhenium-catalyzed insertion of nonpolar and polar unsaturated molecules into an olefinic C-H bond.  

PubMed

Treatment of olefins bearing a directing group with alpha,beta-unsaturated carbonyl compounds, alkynes, or aldehydes in the presence of a catalytic amount of a rhenium complex, [ReBr(CO)(3)(thf)](2) gave gamma,delta-unsaturated carbonyl compounds, dienes, and allyl silyl ethers, respectively. This reaction proceeds via C-H bond activation, insertion of unsaturated molecules into the formed rhenium-carbon bond, and then reductive elimination (or transmetalation in the case of aldehydes). PMID:19469520

Kuninobu, Yoichiro; Fujii, Yasuo; Matsuki, Takashi; Nishina, Yuta; Takai, Kazuhiko

2009-06-18

381

High-Order Harmonic Generation of Homonuclear and Heteronuclear Diatomic Molecules: Exploration of Multiple Orbital Contributions  

NASA Astrophysics Data System (ADS)

We extend the self-interaction-free time-dependent density functional theory (TDDFT) approach with proper asymptotic long-range potential for nonperturbative treatment of high-order harmonic generation (HHG) of diatomic molecules. A time-dependent two-center generalized pseudospectral method in prolate spheroidal coordinate system is used for accurate and efficient treatment of the TDDFT equations in space and time. The theory is applied to a detailed all-electron nonperturbative investigation of HHG processes of homonuclear (N2 and F2) and heteronuclear (CO, BF, and HF) molecules in intense ultrashort laser pulses with the emphasis on the role of multiple molecular orbitals (MOs). The results reveal intriguing and substantially different nonlinear optical response behaviors for homonuclear and heteronuclear molecules. In particular, we found that the HHG spectrum for homonuclear molecules features a destructive interference of MO contributions while heteronuclear molecules show mostly constructive interference of orbital contributions.

Heslar, John; Telnov, Dmitry A.; Chu, Shih-I.

2011-06-01

382

Magnetic coupling of Fe-porphyrin molecules adsorbed on clean and c(2×2) oxygen-reconstructed Co(100) investigated by spin-polarized photoemission spectroscopy  

NASA Astrophysics Data System (ADS)

The spin-polarized electronic structure of iron octaethylporphyrin (FeOEP) molecules adsorbed on a pristine and on a c(2×2) oxygen-reconstructed Co(100) surface has been analyzed by means of spin-polarized photoemission spectroscopy (SPPES) and first-principles density functional theory with the on-site Coulomb repulsion U term (DFT+U) calculations with and without Van der Waals corrections. The aim is to examine the magnetic exchange mechanism between the FeOEP molecules and the Co(100) substrate in the presence or absence of the oxygen mediator. The results demonstrate that the magnetic coupling from the ferromagnetic substrate to the adsorbed FeOEP molecules is ferromagnetic, whereas, the coupling is antiferromagnetic for the FeOEP on the c(2×2)O/Co(100) system. Spin-resolved partial densities of states extracted from ab initio DFT+U modeling are in fairly good comparison with the electronic spectral densities seen in angle-integrated SPPES energy dispersion curves for submonolayer coverages of FeOEP. Through combined analysis of these spectra and theoretical results, we determine that hybridization of 2p orbitals of N and O with Co 3d orbitals facilitates indirect magnetic exchange interactions between Fe and Co, whereas, a direct Fe-Co interaction involving the Fe dz2 orbital is also found for FeOEP on Co. It is observed through SPPES that the spin polarization of the photoemission-visible molecular overlayers decreases to zero as coverage is increased beyond the submonolayer regime, indicating that only interfacial magnetic coupling is at work. Microspot low-energy electron diffraction and low-energy electron microscopy were performed to characterize the physical order of the molecular coverage, revealing that FeOEP structural domains are orders of magnitude greater in size on c(2×2)O/Co(100) than on clean Co(100), which coincides with reduced scattering from the disorder and sharper features seen in SPPES.

Weber, A. P.; Caruso, A. N.; Vescovo, E.; Ali, Md. E.; Tarafder, K.; Janjua, S. Z.; Sadowski, J. T.; Oppeneer, P. M.

2013-05-01

383

Creation of transversely polarized high-energy electrons and positrons in crystals  

SciTech Connect

It is shown that when high-energy ..gamma.. quanta pass through a crystal at small angles to the crystallographic planes (axes) a new phenomenon arises: creation of transversely polarized electrons and positrons by unpolarized ..gamma.. quanta. Estimates based on the theory developed in this paper for this phenomenon show that it can be used to obtain transversely polarized electrons and positrons with degree of polarization 50--90% and with energies of hundreds and thousands GeV in the case of incidence of the ..gamma.. quanta on atomic planes, and starting with an energy of several tens of GeV in the case of incidence on atomic axes. Concrete calculations are made of the polarization, number, and angular distributions of positrons produced by 350-GeV ..gamma.. quanta incident on the (110) family of planes of a tungsten plate of thickness 3 x 10 cm. The features of the manifestation of the described phenomenon in bent crystals are analyzed.

Baryshevskii, V.B.; Tikhomirov, V.V.

1983-07-01

384

"Lossless" compression of high resolution mass spectra of small molecules  

PubMed Central

Fourier transform ion cyclotron resonance (FTICR) provides the highest resolving power of any commercially available mass spectrometer. This advantage is most significant for species of low mass-to-charge ratio (m/z), such as metabolites. Unfortunately, FTICR spectra contain a very large number of data points, most of which are noise. This is most pronounced at the low m/z end of spectra, where data point density is the highest but peak density low. We therefore developed a filter that offers lossless compression of FTICR mass spectra from singly charged metabolites. The filter relies on the high resolving power and mass measurement precision of FTICR and removes only those m/z channels that cannot contain signal from singly charged organic species. The resulting pseudospectra still contain the same signal as the original spectra but less uninformative background. The filter does not affect the outcome of standard downstream chemometric analysis methods, such as principal component analysis, but use of the filter significantly reduces memory requirements and CPU time for such analyses. We demonstrate the utility of the filter for urinary metabolite profiling using direct infusion electrospray ionization and a 15 tesla FTICR mass spectrometer. Electronic supplementary material The online version of this article (doi:10.1007/s11306-010-0202-2) contains supplementary material, which is available to authorized users.

Blanckenburg, Bo; van der Burgt, Yuri E. M.; Deelder, Andre M.

2010-01-01

385

Magnetic anisotropy and high-spin effects in single-molecule transistors  

NASA Astrophysics Data System (ADS)

Fabrication of single-molecule transistors where electron transport occurs through an individual molecule has become possible due to the recent progress in molecular electronics. Three-terminal configuration allows charging molecules and performing transport spectroscopy in multiple redox states. Single-molecule magnets combining large spin with uniaxial anisotropy are of special interest as appealing candidates for high density memory applications and quantum information processing. We study single-molecule magnets Fe4. Three-terminal junctions are fabricated using electromigration of gold nanowires followed by a self-breaking. High-spin Kondo effect and inelastic cotunneling excitations show up in transport measurements. Several excitations feature the energy close to the energy of zero-field splitting (ZFS) of a ground spin multiplet in bulk. This splitting is caused by the anisotropy and is a hallmark of single-molecule magnets. We observe nonlinear Zeeman effect due to a misalignment of an anisotropy axis and a magnetic field direction. The ZFS energy is increased in oxidized and reduced states of the molecule indicating enhancement of the anisotropy in these states.

Zyazin, Alexander; van den Berg, Johan; Osorio, Edgar; Konstantinidis, Nikos; Leijnse, Martin; May, Falk; Hofstetter, Walter; Danieli, Chiara; Cornia, Andrea; Wegewijs, Maarten; van der Zant, Herre

2011-03-01

386

Observation of New Dynamics in the State-Resolved Collisional Relaxation of Highly Excited Molecules  

NASA Astrophysics Data System (ADS)

The dynamics of collisional deactivation of highly energized molecules, pyrazine-h_{4} and pyrazine-d_{4}, by HCl molecules at 300 K show evidence of a new mechanism for collisional energy transfer. Highly vibrationally excited (E_{vib} = 37,900 wn) pyrazine-h_{4} and pyrazine-d_{4} molecules are produced in separate experiments by pulsed excitation with the fourth harmonic output of a Nd:YAG laser at ? = 266 nm. Collisions between the energized isotopes and HCl molecules are monitored by measuring the nascent transient IR absorption of scattered HCl in individual rotational states. The results indicate that HCl molecules are scattered with a gain in rotational and translational energy, but the largest recoil energies are observed for the lowest rotational energy states of HCl. This behavior is opposite to that seen for other bath molecules including DCl and CO_{2}. The results point to differences in intermolecular interactions between the energy donor and acceptor molecules as contributing factors to the observed differences in the mechanism of energy transfer.

Echebiri, Geraldine O.; Smarte, Matthew; Walters, Wendell W.; Cleveland, Jill M.; McCarl, Christine; Kunin, Alice; Mullin, Amy S.

2013-06-01

387

Notch Signaling Molecules Activate TGF-? in Rat Mesangial Cells under High Glucose Conditions  

PubMed Central

The involvement of the Notch signaling pathway in the cellular differentiation of the mammalian kidney is established. Recently, the dysregulation of Notch signaling molecules has been identified in acute and chronic renal injuries, fibrosis models, and diabetic kidney biopsies. The canonical Notch ligand , Jagged1, is upregulated in a transforming growth factor-beta- (TGF-?-) dependent manner during chronic kidney disease. TGF-?, a central mediator of renal fibrosis, also is a major contributor to the development of diabetic nephropathy. To explore the roles and possible mechanisms of Notch signaling molecules in the pathogenesis of diabetic nephropathy, we exposed cultured rat mesangial cells to a ?-secretase inhibitor (DAPT) or high glucose and measured the expression of Notch signaling molecules and the fibrosis index. Notch pathway-related molecules, TGF-?, and fibronectin increased with exposure to high glucose and decreased with DAPT treatment. Our results suggest that the Notch signaling pathway may precipitate diabetic nephropathy via TGF-? activation.

Liu, Li; Gao, Chenlin; Chen, Guo; Li, Xia; Li, Jia; Wan, Qin; Xu, Yong

2013-01-01

388

Polarized Electrons for Polarized Positrons  

NASA Astrophysics Data System (ADS)

Recently, the nuclear and high-energy physics communities have shown a growing interest in the availability of high current, highly spin-polarized positron beams. The Polarized Electrons for Polarized Positrons (PEPPo) experiment at the Thomas Jefferson National Accelerator Facility (Jefferson Lab) aims to measure the transfer of polarization from a low energy 10 MeV highly spin polarized electron beam to positrons. A sufficiently energetic polarized photon or lepton may generate, via bremsstrahlung and pair creation processes within a target foil, electron-positron pairs that will carry a fraction of the initial polarization. This approach has been successfully tested using polarized photons created with a multi-GeV unpolarized electron beam, resulting in positrons with polarization of 80%. Although pair creation yield is reduced at lower energy, recent advances in high current milliampere spin-polarized electron sources at Jefferson Lab offer the perspective of creating polarized positrons using a low energy electron beam. A successful demonstration of this technique would provide an alternative scheme to produce low energy polarized positrons, as well as useful information to optimize the design of a polarized positron source using sub-GeV electron beam. An overview and status of the PEPPo experiment will be presented, along with some of the motivations in the context of the Jefferson Lab nuclear physics program.

Fanchini, Erica

2012-03-01

389

Speckle noise reduction in high speed polarization sensitive spectral domain optical coherence tomography.  

PubMed

We present a high speed polarization sensitive spectral domain optical coherence tomography system based on polarization maintaining fibers and two high speed CMOS line scan cameras capable of retinal imaging with up to 128 k A-lines/s. This high imaging speed strongly reduces motion artifacts and therefore averaging of several B-scans is possible, which strongly reduces speckle noise and improves image quality. We present several methods for averaging retardation and optic axis orientation, the best one providing a 5 fold noise reduction. Furthermore, a novel scheme of calculating images of degree of polarization uniformity is presented. We quantitatively compare the noise reduction depending on the number of averaged frames and discuss the limits of frame numbers that can usefully be averaged. PMID:21934820

Götzinger, Erich; Pircher, Michael; Baumann, Bernhard; Schmoll, Tilman; Sattmann, Harald; Leitgeb, Rainer A; Hitzenberger, Christoph K

2011-07-18

390

Colloidal lenses allow high-temperature single-molecule imaging and improve fluorophore photostability  

Microsoft Academic Search

Although single-molecule fluorescence spectroscopy was first demonstrated at near-absolute zero temperatures (1.8 K), the field has since advanced to include room-temperature observations, largely owing to the use of objective lenses with high numerical aperture, brighter fluorophores and more sensitive detectors. This has opened the door for many chemical and biological systems to be studied at native temperatures at the single-molecule

Jerrod J. Schwartz; Stavros Stavrakis; Stephen R. Quake

2010-01-01

391

Polarization-selective beam splitter based on a highly efficient simple binary diffraction grating.  

PubMed

A polarization beam splitter (PBS) based on a giant-reflection to zero-order (GIRO) grating is presented. The GIRO grating is a simple binary diffraction grating with parameters chosen such that the excited optical modes in the grating interfere constructively and destructively at the respective interfaces. This interference results in high-zero-order reflection (>99%) with a high polarization-selective extinction ratio (+/-30 dB). The grating shows a low aspect ratio. The GIRO PBS is theoretically and experimentally shown to be an adequate PBS for use as an optical isolator in combination with a quarter-wave plate in a CO2-laser system. PMID:15605556

Delbeke, Danaë; Baets, Roel; Muys, Peter

2004-11-20

392

Generation of high-order polarized vortex beam by achromatic meniscus axicon doublet  

NASA Astrophysics Data System (ADS)

A method for generating a high-order (?2) polarized vortex beam by using achromatic meniscus axicon doublets (MADs) is described. The MAD has a rotationally symmetric structure and consists of a pair of identical meniscus axicons with the same apex angle. It exploits four total internal reflections when collimated rays pass through it to produce a half-wave retardation, but with azimuth-variant polarization orientations. The characteristics of high achromatism of retardance, reasonable acceptance angular aperture for MAD, are numerically demonstrated. The effect of the remaining stress birefringence of optical materials on retardation is also discussed.

Zhang, Xusheng; Qiu, Lirong

2013-08-01

393

Extension of high harmonic spectroscopy in molecules by a 1300 nm laser field.  

PubMed

The emerging techniques of molecular spectroscopy by high order harmonic generation have hitherto been conducted only with Ti:Sapphire lasers which are restricted to molecules with high ionization potentials. In order to gain information on the molecular structure, a broad enough range of harmonics is required. This implies using high laser intensities which would saturate the ionization of most molecular systems of interest, e.g. organic molecules. Using a laser at 1300 nm, we are able to extend the technique to molecules with relatively low ionization potentials (approximately 11 eV), observing wide harmonic spectra reaching up to 60 eV. This energy range improves spatial resolution of the high harmonic spectroscopy to the point where interference minima in harmonic spectra of N(2)O and C(2)H(2) can be observed. PMID:20174156

Torres, R; Siegel, T; Brugnera, L; Procino, I; Underwood, Jonathan G; Altucci, C; Velotta, R; Springate, E; Froud, C; Turcu, I C E; Ivanov, M Yu; Smirnova, O; Marangos, J P

2010-02-01

394

Vibrationally induced inversion of photoelectron forward-backward asymmetry in chiral molecule photoionization by circularly polarized light  

PubMed Central

Electron–nuclei coupling accompanying excitation and relaxation processes is a fascinating phenomenon in molecular dynamics. A striking and unexpected example of such coupling is presented here in the context of photoelectron circular dichroism measurements on randomly oriented, chiral methyloxirane molecules, unaffected by any continuum resonance. Here, we report that the forward-backward asymmetry in the electron angular distribution, with respect to the photon axis, which is associated with photoelectron circular dichroism can surprisingly reverse direction according to the ion vibrational mode excited. This vibrational dependence represents a clear breakdown of the usual Franck–Condon assumption, ascribed to the enhanced sensitivity of photoelectron circular dichroism (compared with other observables like cross-sections or the conventional anisotropy parameter-?) to the scattering phase off the chiral molecular potential, inducing a dependence on the nuclear geometry sampled in the photoionization process. Important consequences for the interpretation of such dichroism measurements within analytical contexts are discussed.

Garcia, Gustavo A.; Nahon, Laurent; Daly, Steven; Powis, Ivan

2013-01-01

395

Vibrationally induced inversion of photoelectron forward-backward asymmetry in chiral molecule photoionization by circularly polarized light.  

PubMed

Electron-nuclei coupling accompanying excitation and relaxation processes is a fascinating phenomenon in molecular dynamics. A striking and unexpected example of such coupling is presented here in the context of photoelectron circular dichroism measurements on randomly oriented, chiral methyloxirane molecules, unaffected by any continuum resonance. Here, we report that the forward-backward asymmetry in the electron angular distribution, with respect to the photon axis, which is associated with photoelectron circular dichroism can surprisingly reverse direction according to the ion vibrational mode excited. This vibrational dependence represents a clear breakdown of the usual Franck-Condon assumption, ascribed to the enhanced sensitivity of photoelectron circular dichroism (compared with other observables like cross-sections or the conventional anisotropy parameter-?) to the scattering phase off the chiral molecular potential, inducing a dependence on the nuclear geometry sampled in the photoionization process. Important consequences for the interpretation of such dichroism measurements within analytical contexts are discussed. PMID:23828557

Garcia, Gustavo A; Nahon, Laurent; Daly, Steven; Powis, Ivan

2013-07-01

396

Polarized high-brilliance and high-resolution soft x-ray source at ELETTRA: The performance of beamline BACH  

NASA Astrophysics Data System (ADS)

BACH, a soft x-ray beamline for polarization-dependent experiments at the Italian synchrotron radiation facility ELETTRA, was recently completed and characterized. Its performance, in terms of energy resolution, flux and polarization, is presented. Based on two APPLE II undulators, BACH covers the energy range between 35 and 1600 eV with the control of the light polarization. The monochromator is equipped with four gratings and allows one to work either in a high resolution or in a high flux mode. After the monochromator, the beamline is split into two branches with different refocusing properties. One is optimized to exploit the performance of the soft x-ray spectrometer (ComIXS) available at the beamline. Resolving powers between 12000 at 90 eV photon energy and 6600 near 867 eV were achieved using the high-resolution gratings and the smallest available slit width (10 ?m). For the high-brilliance grating, which works between 290 and 1600 eV, resolving powers between 7000 at 400 eV and 2200 at 867 eV were obtained. The flux in the experimental chamber, measured with the high-resolution gratings for linearly polarized light at the best achievable resolution, ranges between 4×1011 photons/s at 125 eV and 2×1010 photons/s between 900 and 1250 eV. In circularly polarized mode the flux is two times larger for energies up to 380 eV. A gain of nearly one order of magnitude is obtained for the high-brilliance grating, in accordance with theoretical predictions. Flux beyond 1.3×1011 photons/s was measured up to 1300 eV, and thus over nearly the complete energy range covered by this high-brilliance grating, with a maximum of 1.6×1011 photons/s between 800 and 1100 eV. First results from polarization measurements confirm a polarization above 99.7% for both linearly and circularly polarized modes at low energies. Circular dichroism experiments indicate a circular polarization beyond 90% at the Fe L2/L3 edge near 720 eV.

Zangrando, M.; Zacchigna, M.; Finazzi, M.; Cocco, D.; Rochow, R.; Parmigiani, F.

2004-01-01

397

Production of ultracold potassium molecules and development of high sensitivity spectroscopic methods  

NASA Astrophysics Data System (ADS)

In the first part of this dissertation we develop and successfully demonstrate two methods, based on photoassociation of ultracold potassium atoms, for producing ultracold K2 molecules, with sub mK temperatures, in deeply bound vibrational levels of the ground XS+g 1 state. The principal objective has been to develop an ``ultracold molecule factory'' that can be used to support experiments on spectroscopy, collisions, and chemistry of ultracold molecules. In the first experiment the ground-state molecules are produced by the radiative decay of excited, n?191 AS+u 1 state molecules, photoassociated from ultracold potassium atoms in a vapor-cell MOT. The decay is primarily into the vibrational continuum, but a small fraction decays into bound levels of the X state near n = 36. The experimentally observed molecule production rate is about 103 per second. In our second experiment, we use two-step laser excitation to effect an ``R-transfer'' from long-range to intermediate internuclear separations, greatly increasing the efficiency for radiative production of low- n molecules in the X state. Molecules are formed in the Pg1 state by photoassociation, then excited by a second laser to the 51Pu or 61Pu Rydberg states, in selected vibrational levels from n = 13-18. Finally, radiative decay produces very large numbers of X state molecules with n?25 and significant numbers of molecules in very low vibrational levels, including n = 0. We have observed production rates up to about 105 molecules/second per vibrational level. In both experiments the ground-state molecules are detected with a sensitive and selective resonant two- color photoionization with nanosecond pulses. In the second part of this dissertation we demonstrate a novel method for high sensitivity absorption measurements, that combines a phase modulated, high- resolution pulsed laser with an actively stabilized optical cavity to achieve a sensitivity of ~10-9 per cm. This is comparable to the best existing methods for pulsed absorption measurements, but unlike most other methods, it can also be readily extended to the UV region and to Doppler-free spectroscopy.

Nikolov, Anguel Nikolov

2000-10-01

398

Visualization of the polarity of isolated titin molecules: a single globular head on a long thin rod as the M band anchoring domain?  

Microsoft Academic Search

TII, the extractable form of titin, was purified from myofibrils and separated by high resolu- tion gel permeation chromatography into two fractions (TII^ and TIIa). Novel specimen orientation methods used before metal shadowing and EM result in striking pictures of the two forms. Molecules layered on mica become uniformly oriented when subjected to centrifu- gation. TIIa comprises a very homogeneous

Rfidiger Nave; Dieter O. Fiirst; Klaus Weber

1989-01-01

399

High-extinction-ratio micro polarizing beam splitter for short wavelength optical storage applications.  

PubMed

A surface-micromachined high-extinction-ratio polarizing beam splitter (PBS) using low absorptive silicon nitride layers for blue wavelength applications are demonstrated. The micro polarizing beam splitter consists of novel stack of two silicon nitride layers separated by an air gap. A PBS optimization model is established to achieve both high extinction-ratio and adequate process margin. The polarization extinction ratios of 25 dB for the reflected light and 15 dB for the transmitted light were experimentally achieved at lambda=405 nm. The fabrication of the PBS is compatible with other micro diffractive elements to build a micro optical bench, thus, feasible for short wavelength optical storage applications. PMID:19503244

Lee, Chi-Hung; Chiu, Yi; Shieh, Han-Ping D

2005-12-12

400

Transport of dust to high northern latitudes in a Martian polar warming  

NASA Astrophysics Data System (ADS)

The transport of dust in the Martian atmosphere into high northern latitudes as a result of a Martian polar-warming (and global-dust-storm) event was investigated using a simplified transport model in conjunction with a beta-plane dynamical model to simulate the transport of dust. Numerical experiments were performed to examine the influence of different warming dynamics and to assess the sensitivity of the transport to the initial dust distribution. Results indicate that substantial amounts of dust could be transported and deposited at high northern latitudes (extending to the pole) in a polar-warming event. The potential for the transport of water was also examined through simulations, with results indicating that large amounts of water could be transported to the north polar region in a warming, on the condition that substantial condensation and precipitation do not take place in the subpolar regions. However, the warmth of the Martian atmosphere during global dust storms makes the latter possible.

Barnes, J. R.

1990-02-01

401

Vector transmission matrix for the polarization behavior of light propagation in highly scattering media.  

PubMed

Recently the optical transmission matrix (TM) has been shown to be useful in controlling the propagation of light in highly scattering media. In this paper, we present the vector transmission matrix (VTM) which, unlike the TM, captures both the intensity and polarization transmission property of the scattering medium. We present an experimental technique for measuring the absolute values of the VTM elements which is in contrast to existing techniques whereby the TM elements are measured to within a scaling factor. The usefulness of the VTM is illustrated by showing that it can be used to both predict and control the magnitude of the complex polarization ratio of the light focused through the scattering medium. To the best of our knowledge, this is the first study to show the possibility of controlling the polarization of the light transmitted through highly scattering media. PMID:22772297

Tripathi, Santosh; Paxman, Richard; Bifano, Thomas; Toussaint, Kimani C

2012-07-01

402

Double electron transfer in slow, highly charged ion-molecule collisions  

Microsoft Academic Search

During collisions between slow highly charged ions and neutral atoms or molecules, a lot of electrons can be transferred into multiply excited levels of the highly charged ions, and finally the product ions are stabilized by ejection of electrons (autoionization decay) or photons (radiative decay). The ratios of the radiative decay to the autoionization decay after double-electron transfer processes in

F. Krok; H. Tawara; I. Yu Tolstikhina; H. A. Sakaue; I. Yamada; K. Hosaka; M. Kimura; A. Matsumoto; N. Nakamura; S. Ohtani; M. Sakurai; H. Watanabe; M. Yoshino

1997-01-01

403

Degradation and segregation: Thermal stability and highly ordered epitaxial thin films of large aromatic molecules  

Microsoft Academic Search

The authors present an investigation of highly ordered epitaxial thin films of large organic molecules, namely quaterrylene derivatives. Even though the raw material quaterrylene tetracarboxylic diimide (QTCDI) starts to decompose below its sublimation temperature, epitaxial monolayers could be grown. By modifying the preparation procedure, highly ordered domains of quaterrylene dicarboxylic monoimide, being the main decomposition product of QTCDI, could also

C. Wagner; R. Franke; T. Dienel; R. Forker; R. Jacob; T. Fritz

2007-01-01

404

High-throughput metabolic engineering: advances in small-molecule screening and selection.  

PubMed

Metabolic engineering for the overproduction of high-value small molecules is dependent upon techniques in directed evolution to improve production titers. The majority of small molecules targeted for overproduction are inconspicuous and cannot be readily obtained by screening. We provide a review on the development of high-throughput colorimetric, fluorescent, and growth-coupled screening techniques, enabling inconspicuous small-molecule detection. We first outline constraints on throughput imposed during the standard directed evolution workflow (library construction, transformation, and screening) and establish a screening and selection ladder on the basis of small-molecule assay throughput and sensitivity. An in-depth analysis of demonstrated screening and selection approaches for small-molecule detection is provided. Particular focus is placed on in vivo biosensor-based detection methods that reduce or eliminate in vitro assay manipulations and increase throughput. We conclude by providing our prospectus for the future, focusing on transcription factor-based detection systems as a natural microbial mode of small-molecule detection. PMID:20367033

Dietrich, Jeffrey A; McKee, Adrienne E; Keasling, Jay D

2010-01-01

405

Differential feeding as a concept for the realization of broadband dual-polarized antennas with very high polarization purity  

Microsoft Academic Search

In this paper a new concept for the design of the ultra broadband antennas with dual-orthogonal, linear polarization is introduced. It enables an outstanding polarization decoupling over the very wide frequency range. The antenna built accordingly to this concept can be realized in the planar technology, where the radiation occurs perpendicularly to the antenna surface. This feature is not common

Grzegorz Adamiuk; Werner Wiesbeck; Thomas Zwick

2009-01-01

406

Polarization holographic high-density optical data storage in bacteriorhodopsin film  

NASA Astrophysics Data System (ADS)

Optical films containing the genetic variant bacteriorhodopsin BR-D96N were experimentally studied in view of their properties as media for holographic storage. Different polarization recording schemes were tested and compared. The influence of the polarization states of the recording and readout waves on the retrieved diffractive image's intensity and its signal-to-noise ratio were analyzed. The experimental results showed that, compared with the other tested polarization relations during holographic recording, the discrimination between the polarization states of diffracted and scattered light is optimized with orthogonal circular polarization of the recording beams, and thus a high signal-to-noise ratio and a high diffraction efficiency are obtained. Using a He-Ne laser (633 nm,3 mW) for recording and readout, a spatial light modulator as a data input element, and a 2D-CCD sensor for data capture in a Fourier-transform holographic setup, a storage density of 2×108 bits/cm2 was obtained on a 60×42 µm2 area in the BR-D96N film. The readout of encoded binary data was possible with a zero-error rate at the tested storage density.

Yao, Baoli; Ren, Zhiwei; Menke, Neimule; Wang, Yingli; Zheng, Yuan; Lei, Ming; Chen, Guofu; Hampp, Norbert

2005-12-01

407

Polarization holographic high-density optical data storage in bacteriorhodopsin film.  

PubMed

Optical films containing the genetic variant bacteriorhodopsin BR-D96N were experimentally studied in view of their properties as media for holographic storage. Different polarization recording schemes were tested and compared. The influence of the polarization states of the recording and readout waves on the retrieved diffractive image's intensity and its signal-to-noise ratio were analyzed. The experimental results showed that, compared with the other tested polarization relations during holographic recording, the discrimination between the polarization states of diffracted and scattered light is optimized with orthogonal circular polarization of the recording beams, and thus a high signal-to-noise ratio and a high diffraction efficiency are obtained. Using a He-Ne laser (633 nm, 3 mW) for recording and readout, a spatial light modulator as a data input element, and a 2D-CCD sensor for data capture in a Fourier transform holographic setup, a storage density of 2 x 10(8) bits/cm2 was obtained on a 60 x 42 microm2 area in the BR-D96N film. The readout of encoded binary data was possible with a zero-error rate at the tested storage density. PMID:16353805

Yao, Baoli; Ren, Zhiwei; Menke, Neimule; Wang, Yingli; Zheng, Yuan; Lei, Ming; Chen, Guofu; Hampp, Norbert

2005-12-01

408

Physiological ecology of Mesozoic polar forests in a high CO2 environment.  

PubMed

Fossils show that coniferous forests extended into polar regions during the Mesozoic, a time when models and independent paleo-CO2 indicators suggest that the atmospheric CO2 concentration was at least double that of the present day. Consequently, such polar forests would have experienced high CO2 interacting with an extreme variation in light. Here we describe an experiment investigating this plant-environment interaction for extant tree species that were important components of polar forests, and give results from the first year of treatment. Specifically, we tested the hypotheses that growth in elevated CO2 (1) stimulates photosynthesis; (2) reduces photoinhibition during the polar summer; and (3) reduces respiration of above- and below-ground plant organs. Our results indicate that CO2 fertilization generally does not affect photosynthesis under continuous daylight characteristic of the polar summer but does increase it when the period of illumination is shorter. Growth in elevated CO2 did not alter the potential for photoinhibition. CO2 enrichment significantly reduced leaf and root respiration rates by 50 and 25 %, respectively, in a range of evergreen taxa. Incorporating these observed CO2 effects into numerical simulations using a process-based model of coniferous forest growth indicates that a high paleo-CO2 concentration would have increased the productivity of Cretaceous conifer forests in northern Alaska. This results from decreased respiratory costs that more than compensate for the absence of high CO2-high temperature interactions during the polar summer. The longer-term effects of CO2 enrichment on seasonal changes in the above- and below-ground carbon balance of trees are discussed. PMID:12096745

Beerling, D J; Osborne, C P

2002-03-01

409

High-Intensity Highly-Polarized Electron Beam for High-Energy Physics.  

National Technical Information Service (NTIS)

A new high-energy parity violation (PV) experiment at SLAC as well as particle-physics experiments using future e+e- colliders (such as NLC) operating at energies above the scale of unification of the electromagnetic and weak interactions require a highly...

J. L. Turner

2002-01-01

410

Recoil Polarization Measurements of the Proton Electromagnetic Form Factor Ratio to High Momentum Transfer  

SciTech Connect

The electromagnetic form factors of the nucleon characterize the effect of its internal structure on its response to an electromagnetic probe as studied in elastic electronnucleon scattering. These form factors are functions of the squared four-momentum transfer Q2 between the electron and the proton. The two main classes of observables of this reaction are the scattering cross section and polarization asymmetries, both of which are sensitive to the form factors in different ways. When considering large f momentum transfers, double-polarization observables offer superior sensitivity to the electric form factor. This thesis reports the results of a new measurement of the ratio of the electric and magnetic form factors of the proton at high momentum transfer using the recoil polarization technique. A polarized electron beam was scattered from a liquid hydrogen target, transferring polarization to the recoiling protons. These protons were detected in a magnetic spectrometer which was used to reconstruct their kinematics, including their scattering angles and momenta, and the position of the interaction vertex. A proton polarimeter measured the polarization of the recoiling protons by measuring the azimuthal asymmetry in the angular distribution of protons scattered in CH2 analyzers. The scattered electron was detected in a large acceptance electromagnetic calorimeter in order to suppress inelastic backgrounds. The measured ratio of the transverse and longitudinal polarization components of the scattered proton is directly proportional to the ratio of form factors GpE=GpM. The measurements reported in this thesis took place at Q2 =5.2, 6.7, and 8.5 GeV2, and represent the most accurate measurements of GpE in this Q2 region to date.

Andrew Puckett

2010-02-01

411

Solution-processed small molecules using different electron linkers for high-performance solar cells.  

PubMed

Conjugated acceptor-donor-acceptor small molecules using different electron linkers are designed, synthesized, and used in organic solar cells. All of these small molecules show high photoconversion efficiencies (PCEs), ranging from 3.18-6.15% under simulated AM 1.5G condition. A maximum PCE of 6.15% combined with a high Voc of 0.85 V, a Jsc of 10.79 mA cm(-2) and a notable FF of 67.1% are achieved with T3/PC71 BM blend based devices using polydimethylsiloxane as additive. PMID:23824701

Liu, Yongsheng; Yang, Yang Michael; Chen, Chun-Chao; Chen, Qi; Dou, Letian; Hong, Ziruo; Li, Gang; Yang, Yang

2013-07-04

412

FUNDAMENTAL AREAS OF PHENOMENOLOGY (INCLUDING APPLICATIONS): High Polarization Single Mode Photonic Crystal Microlaser  

Microsoft Academic Search

Generally, dipole mode is a doubly degenerate mode. Theoretical calculations have indicated that the single dipole mode of two-dimensional photonic crystal single point defect cavity shows high polarization property. We present a structure with elongated lattice, which only supports a single y-dipole mode. With this structure we can eliminate the degeneracy, control the lasing action of the cavity and demonstrate

Wei Chen; Ming-Xin Xing; Wen-Jun Zhou; An-Jin Liu; Wan-Hua Zheng

2009-01-01

413

Absolute Measurement of the Polarization of High Energy Proton Beams at RHIC.  

National Technical Information Service (NTIS)

The spin physics program at the Relativistic Heavy Ion Collider (RHIC) requires knowledge of the beam polarization to better than 5%. Such a goal is made the more difficult by the lack of knowledge of the analyzing power of high energy nuclear physics pro...

A. Bravar A. Kponou A. Nass G. Bunce H. Huang R. Gill W. Meng Y. Makdisi Z. Li

2007-01-01

414

Fluorescence Polarization and Anisotropy in High Throughput Screening: Perspectives and Primer  

Microsoft Academic Search

Fluorescence polarization and anisotropy are two nearly equivalent techniques that have together, over the past 5 years, achieved wide use in high throughput screening in drug discovery. These are single-label methods that can be used to construct homogeneous assays that are fast, sensitive, and resistant to some significant interferences. Moreover, the assays are relatively inexpensive. This review surveys the peer-reviewed

John C. Owicki

2000-01-01

415

A high power gain switched diode laser oscillator and amplifier for the CEBAF polarized electron injector  

SciTech Connect

The photocathode in the polarized electron source at Jefferson Lab is illuminated with pulsed laser light from a gain switched diode laser and diode optical amplifier. Laser pulse repetition rates up to 2,000 MHz, optical pulsewidths between 31 and 123 ps, and average power > 100 mW are demonstrated. The laser system is highly reliable and completely remotely controlled.

Poelker, M.; Hansknecht, J.

1996-12-31

416

Polarization studies on the two-step radiative recombination of highly charged, heavy ions  

Microsoft Academic Search

Radiative recombination of a free electron into an excited state of a bare, high-Z ion is studied, together with its subsequent decay, within the framework of the density matrix theory and Dirac's relativistic equation. Special attention is paid to the polarization and angular correlations between the recombination and the decay photons. In order to perform a systematic analysis of these

A. V. Maiorova; A. Surzhykov; S. Tashenov; V. M. Shabaev; S. Fritzsche; G. Plunien; Th Stöhlker

2009-01-01

417

Dielectric relaxation of para polar liquids under high frequency electric field  

Microsoft Academic Search

The structural and associational aspects of nonspherical para polar liquids (j) in nonpolar solvents (i) are studied through high frequency conductivities ?ij's of solutions. The relaxation time ? of the respective liquids under 3cm. wavelength electric field at various experimental temperatures in °C are estimated from the slope of individual variations of real ??ij and imaginary ??ij parts of hf

N Ghosh; R. C Basak; S. K Sit; S Acharyya

2000-01-01

418

Polarized high pressure {sup 3}H-vectore target at MAMI  

SciTech Connect

In the frame of the A1-Collaboration at the Mainz Microtron a test measurement of doubly polarized {sup 3}H-vectore(e-vector,e{sup '}n) scattering from a high pressure target was performed in July aiming for the determination of the neutron electric form factor G{sub en} at high momentum transfer (Q{sup 2}=0.7(GeV/c){sup 2}). Due to the small value of G{sub en} compared to G{sub mn} a preferred procedure is to determine the asymmetry in the exclusive quasi elastic scattering of polarized electrons (P{approx_equal}70%, I{>=}2{mu}A) from polarized {sup 3}H-vectore. The scattered electrons are detected in a high resolution magnetic spectrometer while the scattering angles of the outgoing neutrons are measured in a plastic scintillator. In this reaction the polarized {sup 3}H-vectore nucleus serves as an effective polarized neutron target. Because of the large magnetic field gradients caused by the spectrometer and limited space at the target place, the {sup 3}H-vectore gas is polarized elsewhere and transported to the target place in specially prepared glass cells. The glass cells are designed for high pressure (up to 10 bar) and with thin windows to prevent background. To reduce the relaxation due to the magnetic field gradients a {mu}-metal shielded guiding field of 4 Gauss is used. The guiding field is generated by three independent coils which permit the rotation of the target spin in any direction desired, especially perpendicular and parallel with respect to q-vector. So we are able to take the ratio of the asymmetries A{sub perpendicular}/A{sub parallel}, which in first order depends only on kinematical factors and the ratio G{sub en}/G{sub mn}. The method of metastable optical pumping is used to polarize the {sup 3}H-vectore at about 1 mbar with a LNA laser ({approx_equal}6W). Subsequently the gas is compressed by means of a two-stage-piston compressor up to 6 bar with a polarization of roughly 45%.

Rohe, Daniela; Becker, J.; Bermuth, J.; Deninger, A.; Ebert, M.; Grossmann, T.; Lauer, L.; Otten, E. W.; Rohe, D.; Surkau, R. [Institut fuer Physik, Universitaet Mainz, D-55099 Mainz (Germany); Bartsch, P.; Baumann, D.; Boehm, R.; Caprano, T.; Clawiter, N.; Derber, S.; Ding, M.; Distler, M.; Ebbes, A.; Ewald, I. [Institut fuer Kernphysik, Universitaet Mainz, D-55099 Mainz (Germany)] (and others)

1998-01-20

419

Highly Polarized Raman Scattering Anisotropy in Single GaN Nanowires  

SciTech Connect

Single GaN nanowires and larger GaN ensembles are investigated by Raman spectroscopy. Spectra of nanowire ensembles prove the high crystal quality and are in agreement with selection rules for the wurtzite structure. Single nanowires are studied with a spatial resolution of the order of 400 nm for different polarization directions of the incident laser beam relative to the nanowire axis. In the single wire spectrum, only the A{sub 1}(TO) was observed and the Raman intensity was suppressed for perpendicular polarization. These results confirm that Raman scattering in isolated GaN nanowires is governed by size effects.

Sutter, E.; Schäfer-Nolte, E.O.; Stoica, T.; Gotschke, T.; Limbach, F.; Sutter, P.; Calarco, R.

2010-03-01

420

Optical rotation quasi-phase-matching for circularly polarized high harmonic generation.  

PubMed

A scheme for quasi-phase-matching high harmonic generation of circularly polarized radiation is proposed: optical rotation quasi-phase-matching (ORQPM). In ORQPM, propagation of the driving radiation in a system exhibiting circular birefringence causes its plane of polarization to rotate; by appropriately matching the period of rotation to the coherence length, it is possible to avoid destructive interference of the generated radiation. It is shown that ORQPM is approximately five times more efficient than conventional QPM, and half as efficient as true phase-matching. PMID:22739926

Liu, Lewis Z; O'Keeffe, Kevin; Hooker, Simon M

2012-06-15