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Sample records for highly polar molecules

  1. Resonant quenching of Rydberg atomic states by highly polar molecules

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    The results of theoretical studies of the resonant quenching and ion-pair formation processes induced by collisions of Rydberg atoms with highly polar molecules possessing small electron affinities are reported. We elaborate an approach for describing collisional dynamics of both processes and demonstrate the predominant role of resonant quenching channel of reaction for the destruction of Rydberg states by electron-attaching molecules. The approach is based on the solution of the coupled differential equations for the transition amplitudes between the ionic and Rydberg covalent terms of a quasimolecule formed during a collision of particles. It takes into account the possibility of the dipole-bound anion decay in the Coulomb field of the positive ionic core and generalizes previous models of charge-transfer processes involving Rydberg atoms to the cases, when the multistate Landau–Zener approaches become inapplicable. Our calculations for {{Rb}}({nl}) atom perturbed by {{{C}}}2{{{H}}}4{{SO}}3, {{CH}}2{CHCN}, {{CH}}3{{NO}}2, {{CH}}3{CN}, {{{C}}}3{{{H}}}2{{{O}}}3, and {{{C}}}3{{{H}}}4{{{O}}}3 molecules show that the curves representing the dependence of the resonant quenching cross sections on the principal quantum number n are bell-shaped with the positions of maxima being shifted towards lower values of n and the peak values, {σ }{max}({{q})}, several times higher than those for the ion-pair formation, {σ }{max}({{i})}. We obtain a simple power relation between the energy of electron affinity of a molecule and the position of maximum in n-dependence of the resonant quenching cross section. It can be used as an additional means for determining small binding energies of dipole-bound anions from the experimental data on resonant quenching of Rydberg states by highly polar molecules.

  2. Polarization and ellipticity of high-order harmonics from aligned molecules generated by linearly polarized intense laser pulses

    NASA Astrophysics Data System (ADS)

    Le, Anh-Thu; Lucchese, R. R.; Lin, C. D.

    2010-08-01

    We present theoretical calculations for polarization and ellipticity of high-order harmonics from aligned N2, CO2, and O2 molecules generated by linearly polarized lasers. Within the rescattering model, the two polarization amplitudes of the harmonics are determined by the photo-recombination amplitudes for photons emitted with polarization parallel or perpendicular to the direction of the same returning electron wave packet. Our results show clear species-dependent polarization states, in excellent agreement with experiments. We further note that the measured polarization ellipse of the harmonic furnishes the needed parameters for a “complete” experiment in molecules.

  3. Understanding ultracold polar molecules

    NASA Astrophysics Data System (ADS)

    Julienne, Paul

    2009-05-01

    The successful production of a dense sample of ultracold ground state KRb polar molecules [1] opens the door to a new era of research with dipolar gases and lattices of such species. This feat was achieved by first associating a K and a Rb atom to make a weakly bound Feshbach molecule and then coherently transferring the population to the ground vibrational level of the molecule. This talk focuses on theoretical issues associated with making and using ultracold polar molecules, using KRb as an example [2]. Full understanding of this species and the processes by which it is made requires taking advantage of accurate molecular potentials [3], ab initio calculations [4], and the properties of the long-range potential. A highly accurate model is available for KRb for all bound states below the ground state separated atom limit and could be constructed for other species. The next step is to develop an understanding of the interactions between polar molecules, and their control in the ultracold domain. Understanding long-range interactions and threshold resonances will be crucial for future work. [1] K.-K. Ni, et al, Science 322, 231(2008). [2] P. S. Julienne, arXiv:0812:1233. [3] Pashov et al., Phys. Rev. A76, 022511 (2007). [4] S. Kotochigova, et al., arXiv:0901.1486.

  4. Ultracold polar KRb molecules

    NASA Astrophysics Data System (ADS)

    Neyenhuis, Brian; Chotia, Amodsen; Moses, Steven; Ye, Jun; Jin, Deborah

    2011-05-01

    Ultracold polar molecules in the quantum degenerate regime open the possibility of realizing quantum gases with long-range, and spatially anisotropic, interparticle interactions. Currently, we can create a gas of ultracold fermionic ground-state KRb molecules in with a peak density of 1012 cm-3 and a temperature just 1.4 times the Fermi temperature. We will report on efforts to further cool this gas of molecules. One possibility is to evaporatively cool a spin-polarized molecular Fermi gas confined in quasi-2D, where we would rely on dipole-dipole interactions for rethermalization. We acknowledge funding from NIST, NSF, and AFOSR-MURI.

  5. Collisional decoherence of polar molecules

    NASA Astrophysics Data System (ADS)

    Walter, Kai; Stickler, Benjamin A.; Hornberger, Klaus

    2016-06-01

    The quantum state of motion of a large and rotating polar molecule can lose coherence through the collisions with gas atoms. We show how the associated quantum master equation for the center of mass can be expressed in terms of the orientationally averaged differential and total scattering cross sections, for which we provide approximate analytic expressions. The master equation is then utilized to quantify collisional decoherence in a interference experiment with polar molecules.

  6. Highly efficient spin polarizer based on individual heterometallic cubane single-molecule magnets

    NASA Astrophysics Data System (ADS)

    Dong, Damin

    2015-09-01

    The spin-polarized transport across a single-molecule magnet [Mn3Zn(hmp)3O(N3)3(C3H5O2)3].2CHCl3 has been investigated using a density functional theory combined with Keldysh non-equilibrium Green's function formalism. It is shown that this single-molecule magnet has perfect spin filter behaviour. By adsorbing Ni3 cluster onto non-magnetic Au electrode, a large magnetoresistance exceeding 172% is found displaying molecular spin valve feature. Due to the tunneling via discrete quantum-mechanical states, the I-V curve has a stepwise character and negative differential resistance behaviour.

  7. Shifting nodal-plane suppressions in high-order-harmonic spectra from diatomic molecules in orthogonally polarized driving fields

    NASA Astrophysics Data System (ADS)

    Das, T.; Figueira de Morisson Faria, C.

    2016-08-01

    We analyze the imprint of nodal planes in high-order-harmonic spectra from aligned diatomic molecules in intense laser fields whose components exhibit orthogonal polarizations. We show that the typical suppression in the spectra associated to nodal planes is distorted, and that this distortion can be employed to map the electron's angle of return to its parent ion. This investigation is performed semianalytically at the single-molecule response and single-active orbital level, using the strong-field approximation and the steepest descent method. We show that the velocity form of the dipole operator is superior to the length form in providing information about this distortion. However, both forms introduce artifacts that are absent in the actual momentum-space wave function. Furthermore, elliptically polarized fields lead to larger distortions in comparison to two-color orthogonally polarized fields. These features are investigated in detail for O2, whose highest occupied molecular orbital provides two orthogonal nodal planes.

  8. Strongly interacting ultracold polar molecules

    NASA Astrophysics Data System (ADS)

    Gadway, Bryce; Yan, Bo

    2016-08-01

    This paper reviews recent advances in the study of strongly interacting systems of dipolar molecules. Heteronuclear molecules feature large and tunable electric dipole moments, which give rise to long-range and anisotropic dipole–dipole interactions. Ultracold samples of dipolar molecules with long-range interactions offer a unique platform for quantum simulations and the study of correlated many-body physics. We provide an introduction to the physics of dipolar quantum gases, both electric and magnetic, and summarize the multipronged efforts to bring dipolar molecules into the quantum regime. We discuss in detail the recent experimental progress in realizing and studying strongly interacting systems of polar molecules trapped in optical lattices, with particular emphasis on the study of interacting spin systems and non-equilibrium quantum magnetism. Finally, we conclude with a brief discussion of the future prospects for studies of strongly interacting dipolar molecules.

  9. High lubrication performance of tribologically oriented fluoropolymer molecules analyzed by polarized infrared microspectroscopy

    NASA Astrophysics Data System (ADS)

    Sugimoto, Iwao; Miyake, Shojiro

    1990-05-01

    The molecular structural changes induced in sputtered fluoropolymer film by tribological effects is pursued using polarized micro-Fourier-transform-infrared (micro-FTIR) spectroscopy. Hydrogenation of the carbon radicals produced by CF or CC bond cleavage is detected in the mildly rubbed region, together with C■C bond formation. Polarization measurements reveal that a rigid C■C-bond-rich framework is oriented along the sliding direction in a hardly rubbed region. This rigid carbon framework involves CF bonds with low polarizability. This structure greatly contributes to stable lubrication with a low friction coefficient, after the fluctuating lubrication characteristics that occur in the early rubbing stage have stabilized. These molecular structures are decomposed into C 3/4 C and C■C■C bonds through further elimination of CF moieties by abrasive hard rubbing by all means. Finally, they extremely decompose into amorphous carbon and metal carbide under severe conditions involving the reactive metals which appear after the film molecules are worn out.

  10. Vibrational spectroscopy of polar molecules with superradiance

    NASA Astrophysics Data System (ADS)

    Lin, Guin-Dar; Yelin, Susanne F.

    2013-07-01

    We investigate cooperative phenomena and superradiance for vibrational transitions in polar molecule spectroscopy of high optical-depth samples. Such cooperativity comes from the build-up of inter-particle coherence through dipole-dipole interactions and leads to speed-up of decay processes. We compare our calculation to recent work and find very good agreement, suggesting that superradiant effects need to be taken into account in a wide variety of ultracold molecule experiments, including vibrational and rotational states.

  11. High-throughput fluorescence polarization assay to identify small molecule inhibitors of BRCT domains of breast cancer gene 1.

    PubMed

    Lokesh, G L; Rachamallu, Aparna; Kumar, G D Kishore; Natarajan, Amarnath

    2006-05-01

    The C-terminus region of the 1863 residue early onset of breast cancer gene 1 (BRCA1) nuclear protein contains a tandem globular carboxy terminus domain termed BRCT. The BRCT repeats in BRCA1 are phosphoserine- and/or phosphothreonine-specific binding modules. The interaction of the BRCT(BRCA1) domains with phosphorylated BRCA1-associated carboxyl terminal helicase (BACH1) is cell cycle regulated and is essential for DNA damage-induced checkpoint control during the transition from the G(2) phase to the M phase of the cell cycle. Development of a competitive, homogeneous, high-throughput fluorescence polarization (FP) assay to identify small molecule inhibitors of BRCT(BRCA1)-BACH1 interaction is reported here. The FP assay was used for measuring binding affinities and inhibition constants of BACH1 peptides and small molecule inhibitors of BRCT(BRCA1) domains, respectively. A fluorescently labeled wild-type BACH1 decapeptide (BDP1) containing the critical phosphoserine, a phenylalanine at (P+3), and a GST-BRCT fusion protein were used to establish the FP assay. BDP1 has a dissociation constant (K(d)) of 1.58+/-0.01microM and a dynamic range (DeltamP) of 164.9+/-1.9. The assay tolerates 20% dimethyl sulfoxide, which enables screening poorly soluble compounds. Under optimized conditions, a Z' factor of 0.87 was achieved in a 384-well format for high-throughput screening. PMID:16500609

  12. High-order harmonic generation of N2 molecule in two-color circularly polarized laser fields

    NASA Astrophysics Data System (ADS)

    Hui, Du; Jun, Zhang; Shuai, Ben; Hui-Ying, Zhong; Tong-Tong, Xu; Jing, Guo; Xue-Shen, Liu

    2016-04-01

    The generation of high-order harmonics and the attosecond pulse of the N2 molecule in two-color circularly polarized laser fields are investigated by the strong-field Lewenstein model. We show that the plateau of spectra is dramatically extended and a continuous harmonic spectrum with the bandwidth of 113 eV is obtained. When a static field is added to the x direction, the quantum path control is realized and a supercontinuum spectrum can be obtained, which is beneficial to obtain a shorter attosecond pulse. The underlying physical mechanism is well explained by the time–frequency analysis and the semi-classical three-step model with a finite initial transverse velocity. By superposing several orders of harmonics in the combination of two-color circularly polarized laser fields and a static field, an isolated attosecond pulse with a duration of 30 as can be generated. Project supported by the National Natural Science Foundation of China (Grant Nos. 61575077, 11271158, and 11574117).

  13. Production and Trapping of Ultracold Polar Molecules

    SciTech Connect

    David, DeMille

    2015-04-21

    We report a set of experiments aimed at the production and trapping of ultracold polar molecules. We begin with samples of laser-cooled and trapped Rb and Cs atoms, and bind them together to form polar RbCs molecules. The binding is accomplished via photoassociation, which uses a laser to catalyze the sticking process. We report results from investigation of a new pathway for photoassociation that can produce molecules in their absolute ground state of vibrational and rotational motion. We also report preliminary observations of collisions between these ground-state molecules and co-trapped atoms.

  14. Circularly Polarized Luminescence from Simple Organic Molecules.

    PubMed

    Sánchez-Carnerero, Esther M; Agarrabeitia, Antonia R; Moreno, Florencio; Maroto, Beatriz L; Muller, Gilles; Ortiz, María J; de la Moya, Santiago

    2015-09-21

    This article aims to show the identity of "circularly polarized luminescent active simple organic molecules" as a new concept in organic chemistry due to the potential interest of these molecules, as availed by the exponentially growing number of research articles related to them. In particular, it describes and highlights the interest and difficulty in developing chiral simple (small and non-aggregated) organic molecules able to emit left- or right-circularly polarized light efficiently, the efforts realized up to now to reach this challenging objective, and the most significant milestones achieved to date. General guidelines for the preparation of these interesting molecules are also presented. PMID:26136234

  15. Fluorescence Polarization Assays in Small Molecule Screening

    PubMed Central

    Lea, Wendy A.; Simeonov, Anton

    2011-01-01

    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. PMID:22328899

  16. Formation and analysis of ultracold polar molecules

    NASA Astrophysics Data System (ADS)

    Juarros, Elizabeth Ann

    Alkali hydride molecules are polar, exhibiting large ground-state dipole moments. As ultracold sources of alkali atoms, as well as hydrogen, have been created in the laboratory, we explore theoretically the feasibility of forming such molecules from a mixture of the ultracold atomic gases, employing various photoassociation schemes. In this work we use lithium and sodium hydride as benchmark systems to calculate molecule formation rates through stimulated one-photon radiative association directly from the continuum as well as two-photon stimulated radiative association (Raman transfer) and excitation to bound levels of an excited state followed by spontaneous emission to the ground state. Using accurate molecular potential energy curves and dipole transition moments and with laser intensities and MOT densities that are easily attainable experimentally, we have found that substantial molecule formation rates can be realized even after the effect of back-stimulation has been accounted for. We examine the spontaneous emission cascade which takes place from the upper vibrational levels of the singlet ground state on a time scale of milliseconds. Because photon emission in the cascade process does not contribute to trap loss, a sizable population of molecules in the lowest vibrational level can be achieved. The triplet ground electronic state is of particular interest for experimental efforts since, although it has never been observed experimentally, molecular structure calculations of the a3Sigma+ state for LiH and NaH predict a small van der Waals attraction, with a potential energy well so shallow that it can support only one bound rotational-vibrational level. Any molecule formed in the triplet ground state would then be immediately in the lowest and most stable level of that state and would be quite long-lived, unlike molecules in high vibrational levels which have significantly shorter lifetimes. As an analysis of our method of calculating molecule formation rates

  17. 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

    Busuladzic, M.; Gazibegovic-Busuladzic, A.; Milosevic, D. B.

    2009-07-15

    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.

  18. 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

    NASA Astrophysics Data System (ADS)

    Busuladžić, M.; Gazibegović-Busuladžić, A.; Milošević, D. B.

    2009-07-01

    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 O2 molecule (characterized by πg symmetry) the maximum yield is observed for some value of the ellipticity ɛ different from zero. On the other hand, in the same circumstances, the N2 molecule (σg) behaves as an atom, i.e., the yield is maximum for ɛ=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.

  19. Spin polarization effect for Fe2 molecule

    NASA Astrophysics Data System (ADS)

    Yan, Shi-Ying; Zhu, Zheng-He

    2006-07-01

    This paper uses the density functional theory (DFT)(B3p86) of Gaussian03 to optimize the structure of Fe2 molecule. The result shows that the ground state for Fe2 molecule is a 9-multiple state, which shows spin polarization effect of Fe2 molecule of transition metal elements for the first time. Meanwhile, we have not found any spin pollution because the wavefunction of the ground state does not mingle with wavefunctions with higher energy states. So, that the ground state for Fe2 molecule is a 9-multiple state is indicative of the spin polarization effect of Fe2 molecule of transition metal elements. That is, there exist 8 parallel spin electrons. The non-conjugated electron is greatest in number. These electrons occupy different spacious tracks, so that the energy of the Fe2 molecule is minimized. It can be concluded that the effect of parallel spin of the Fe2 molecule is larger than the effect of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell-Sorbie potential functions with the parameters for the ground state and other states of Fe2 molecule are derived. Dissociation energy De for the ground state of Fe2 molecule is 2.8586ev, equilibrium bond length Re is 0.2124nm, vibration frequency ωe is 336.38 cm-1. Its force constants f2, f3, and f4 are 1.8615aJ.nm-2, -8.6704aJ.nm-3, 29.1676aJ.nm-4 respectively. The other spectroscopic data for the ground state of Fe2 molecule ωeχe,Be, αe are 1.5461 cm-1, 0.1339 cm-1, 7.3428×10-4 cm-1 respectively.

  20. Orientation detection of a single molecule using pupil filter with electrically controllable polarization pattern

    NASA Astrophysics Data System (ADS)

    Hashimoto, Mamoru; Yoshiki, Keisuke; Kurihara, Makoto; Hashimoto, Nobuyuki; Araki, Tsutomu

    2015-12-01

    We have developed a system for measuring the orientation of single molecules using a conventional wide-field fluorescence microscope with a polarization filter consisting of a polarizer and a compact polarization mode converter. The polarization filter electrically controls the pattern of polarization filtering. Since the polarization of the fluorescence from a single molecule highly depends on the angle between the observation direction and the molecular direction, polarization pattern filtering at the pupil plane of the objective lens allows the orientation of a single molecule to be visualized. Using this system, we demonstrated the orientation detection of single molecules.

  1. Assembling Ultracold Polar Molecules From Single Atoms

    NASA Astrophysics Data System (ADS)

    Liu, Lee R.; Hutzler, Nicholas R.; Yu, Yichao; Zhang, Jessie T.; Ni, Kang-Kuen

    2016-05-01

    Ultracold polar molecules are promising candidates for studying quantum many-body phenomena and building quantum information systems, due to their long-range, anisotropic, and tunable interactions. This calls for a technique to create low entropy samples of ultracold polar molecules with a large dipole moment. The lowest entropy molecular gas to date was created from atomic quantum gases in bulk or in optical lattices. The entropy is limited by that of the constituent atomic gases. We propose a method that addresses this limitation by assembling sodium cesium (NaCs) molecules from individually manipulated atoms. First, we load single Na and Cs atoms in separate optical tweezers from MOTs. We will cool them to their motional ground state using Raman sideband cooling and then merge them into a single tweezer. The tweezer confinement provides enhanced wavefunction overlap between the atom pair and molecule states. Using coherent two-photon techniques, we will then transfer the atom pair into a molecule. Our method offers reduced apparatus complexity and cycle time, single-site manipulation and imaging resolution, and should be readily extended to different species.

  2. Ultracold polar molecules near quantum degeneracy.

    PubMed

    Ospelkaus, S; Ni, K K; de Miranda, M H G; Neyenhuis, B; Wang, D; Kotochigova, S; Julienne, P S; Jin, D S; Ye, J

    2009-01-01

    We report the creation and characterization of a near quantum-degenerate gas of polar 40K-87Rb molecules in their absolute rovibrational ground state. Starting from weakly bound heteronuclear KRb Feshbach molecules, we implement precise control of the molecular electronic, vibrational, and rotational degrees of freedom with phase-coherent laser fields. In particular, we coherently transfer these weakly bound molecules across a 125 THz frequency gap in a single step into the absolute rovibrational ground state of the electronic ground potential. Phase coherence between lasers involved in the transfer process is ensured by referencing the lasers to two single components of a phase-stabilized optical frequency comb. Using these methods, we prepare a dense gas of 4 x 10(4) polar molecules at a temperature below 400 nK. This fermionic molecular ensemble is close to quantum degeneracy and can be characterized by a degeneracy parameter of T/T(F) = 3. We have measured the molecular polarizability in an optical dipole trap where the trap lifetime gives clues to interesting decay mechanisms. Given the large measured dipole moment of the KRb molecules of 0.5 Debye, the study of quantum degenerate molecular gases interacting via strong dipolar interactions is now within experimental reach. PACS numbers: 37.10.Mn, 37.10.Pq. PMID:20151553

  3. Optical Production of Ultracold Polar Molecules

    SciTech Connect

    Sage, Jeremy M.; Sainis, Sunil; DeMille, David; Bergeman, Thomas

    2005-05-27

    We demonstrate the production of ultracold polar RbCs molecules in their vibronic ground state, via photoassociation of laser-cooled atoms followed by a laser-stimulated state transfer process. The resulting sample of X{sup 1}{sigma}{sup +}(v=0) molecules has a translational temperature of {approx}100 {mu}K and a narrow distribution of rotational states. With the method described here it should be possible to produce samples even colder in all degrees of freedom, as well as other bialkali species.

  4. Dynamics of reactive ultracold alkali polar molecules

    NASA Astrophysics Data System (ADS)

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

    2011-05-01

    Recently, ultracold polar molecules of KRb have been created. These molecules are chemically reactive and their lifetime in a trap is limited. However, their lifetime increases when they are loaded into a 1D optical lattice in the presence of an electric field. 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. 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. This work was supported by a MURI-AFOSR grant.

  5. Multichannel quantum defect theory for polar molecules

    NASA Astrophysics Data System (ADS)

    Elfimov, Sergei V.; Dorofeev, Dmitrii L.; Zon, Boris A.

    2014-02-01

    Our work is devoted to developing a general approach for nonpenetrating Rydberg states of polar molecules. We propose a method to estimate the accuracy of calculation of their wave functions and quantum defects. Basing on this method we estimate the accuracy of Born-Oppenheimer (BO) and inverse Born-Oppenheimer (IBO) approximations for these states. This estimation enables us to determine the space and energy regions where BO and IBO approximations are valid. It depends on the interplay between l coupling (due to dipole potential of the core) and l uncoupling (due to rotation the core). Next we consider the intermediate region where both BO and IBO are not valid. For this intermediate region we propose a modification of Fano's multichannel quantum defect theory to match BO and IBO wave functions and show that it gives more reliable results. They are demonstrated on the example of SO molecule.

  6. Aspects of Quantum Computing with Polar Paramagnetic Molecules

    NASA Astrophysics Data System (ADS)

    Karra, Mallikarjun; Friedrich, Bretislav

    2015-05-01

    Since the original proposal by DeMille, arrays of optically trapped ultracold polar molecules have been considered among the most promising prototype platforms for the implementation of a quantum computer. The qubit of a molecular array is realized by a single dipolar molecule entangled via its dipole-dipole interaction with the rest of the array's molecules. A superimposed inhomogeneous electric field precludes the quenching of the body-fixed dipole moments by rotation and a time dependent external field controls the qubits to perform gate operations. Much like our previous work in which we considered the simplest cases of a polar 1 Σ and a symmetric top molecule, here we consider a X2Π3 / 2 polar molecule (exemplified by the OH radical) which, by virtue of its nonzero electronic spin and orbital angular momenta, is, in addition, paramagnetic. We demonstrate entanglement tuning by evaluating the concurrence (and the requisite frequencies needed for gate operations) between two such molecules in the presence of varying electric and magnetic fields. Finally, we discuss the conditions required for achieving qubit addressability (transition frequency difference, Δω , as compared with the concomitant Stark and Zeeman broadening) and high fidelity. International Max Planck Research School - Functional Interfaces in Physics and Chemistry.

  7. Towards Hybrid Quantum Information Processing with Polar Molecules

    NASA Astrophysics Data System (ADS)

    Rabl, Peter

    2008-05-01

    With the ongoing miniaturization of on-chip traps for atoms and ions it is timely to think about coherent interfaces between AMO and solid state systems with potential applications for new hybrid implementations for quantum computers. In this talk I will discuss a potential scenario, where ensembles of polar molecules serve as long-lived quantum memories for superconducting qubits and quantum information is transmitted via a high-Q microwave cavity. Polar molecules combine the exceptional features of a large electric dipole moment and long-lived rotational states with level splittings in the GHz regime. When trapped close to the surface of a chip this combination allows strong interactions with coherent solid state devices, e.g., superconducting microwave cavities or Josephson qubits. I will first introduce the system consisting of a single polar molecule coupled to a stripline cavity which realizes a cavity QED system in the microwave regime and discuss applications for quantum information processing, state detection and new cavity-assisted cooling schemes for polar molecules. I will then switch to molecular ensemble qubits where quantum information is encoded in collective spin or rotational excitations of an ensemble of N molecules. Ensemble qubits benefit from a collectively enhanced coupling ˜√N which allows quantum state transfer between the molecules and, e.g., a charge qubit on a timescale that is compatible with typical coherence times in a solid state environment. With the goal to protect ensemble qubits from collisions, I will finally discuss a scenario, where molecules are prepared in a crystalline phase under 1D trapping conditions and dipole moments aligned by an external field.

  8. Detecting Chirality in Molecules by Linearly Polarized Laser Fields.

    PubMed

    Yachmenev, Andrey; Yurchenko, Sergei N

    2016-07-15

    A new scheme for enantiomer differentiation of chiral molecules using a pair of linearly polarized intense ultrashort laser pulses with skewed mutual polarization is presented. The technique relies on the fact that the off-diagonal anisotropic contributions to the electric polarizability tensor for two enantiomers have different signs. Exploiting this property, we are able to excite a coherent unidirectional rotation of two enantiomers with a π phase difference in the molecular electric dipole moment. The approach is robust and suitable for relatively high temperatures of molecular samples, making it applicable for selective chiral analysis of mixtures, and to chiral molecules with low barriers between enantiomers. As an illustration, we present nanosecond laser-driven dynamics of a tetratomic nonrigid chiral molecule with short-lived chirality. The ultrafast time scale of the proposed technique is well suited to study parity violation in molecular systems in short-lived chiral states. PMID:27472111

  9. Detecting Chirality in Molecules by Linearly Polarized Laser Fields

    NASA Astrophysics Data System (ADS)

    Yachmenev, Andrey; Yurchenko, Sergei N.

    2016-07-01

    A new scheme for enantiomer differentiation of chiral molecules using a pair of linearly polarized intense ultrashort laser pulses with skewed mutual polarization is presented. The technique relies on the fact that the off-diagonal anisotropic contributions to the electric polarizability tensor for two enantiomers have different signs. Exploiting this property, we are able to excite a coherent unidirectional rotation of two enantiomers with a π phase difference in the molecular electric dipole moment. The approach is robust and suitable for relatively high temperatures of molecular samples, making it applicable for selective chiral analysis of mixtures, and to chiral molecules with low barriers between enantiomers. As an illustration, we present nanosecond laser-driven dynamics of a tetratomic nonrigid chiral molecule with short-lived chirality. The ultrafast time scale of the proposed technique is well suited to study parity violation in molecular systems in short-lived chiral states.

  10. Toroidal nanotraps for cold polar molecules

    DOE PAGESBeta

    Salhi, Marouane; Passian, Ali; Siopsis, George

    2015-09-14

    Electronic excitations in metallic nanoparticles in the optical regime that have been of great importance in surface-enhanced spectroscopy and emerging applications of molecular plasmonics, due to control and confinement of electromagnetic energy, may also be of potential to control the motion of nanoparticles and molecules. Here, we propose a concept for trapping polarizable particles and molecules using toroidal metallic nanoparticles. Specifically, gold nanorings are investigated for their scattering properties and field distribution to computationally show that the response of these optically resonant particles to incident photons permit the formation of a nanoscale trap when proper aspect ratio, photon wavelength, andmore » polarization are considered. However, interestingly the resonant plasmonic response of the nanoring is shown to be detrimental to the trap formation. The results are in good agreement with analytic calculations in the quasistatic limit within the first-order perturbation of the scalar electric potential. The possibility of extending the single nanoring trapping properties to two-dimensional arrays of nanorings is suggested by obtaining the field distribution of nanoring dimers and trimers.« less

  11. Toroidal nanotraps for cold polar molecules

    NASA Astrophysics Data System (ADS)

    Salhi, Marouane; Passian, Ali; Siopsis, George

    2015-09-01

    Electronic excitations in metallic nanoparticles in the optical regime that have been of great importance in surface-enhanced spectroscopy and emerging applications of molecular plasmonics, due to control and confinement of electromagnetic energy, may also be of potential to control the motion of nanoparticles and molecules. Here, we propose a concept for trapping polarizable particles and molecules using toroidal metallic nanoparticles. Specifically, gold nanorings are investigated for their scattering properties and field distribution to computationally show that the response of these optically resonant particles to incident photons permit the formation of a nanoscale trap when proper aspect ratio, photon wavelength, and polarization are considered. However, interestingly the resonant plasmonic response of the nanoring is shown to be detrimental to the trap formation. The results are in good agreement with analytic calculations in the quasistatic limit within the first-order perturbation of the scalar electric potential. The possibility of extending the single nanoring trapping properties to two-dimensional arrays of nanorings is suggested by obtaining the field distribution of nanoring dimers and trimers.

  12. Toroidal nanotraps for cold polar molecules

    SciTech Connect

    Salhi, Marouane; Passian, Ali; Siopsis, George

    2015-09-14

    Electronic excitations in metallic nanoparticles in the optical regime that have been of great importance in surface-enhanced spectroscopy and emerging applications of molecular plasmonics, due to control and confinement of electromagnetic energy, may also be of potential to control the motion of nanoparticles and molecules. Here, we propose a concept for trapping polarizable particles and molecules using toroidal metallic nanoparticles. Specifically, gold nanorings are investigated for their scattering properties and field distribution to computationally show that the response of these optically resonant particles to incident photons permit the formation of a nanoscale trap when proper aspect ratio, photon wavelength, and polarization are considered. However, interestingly the resonant plasmonic response of the nanoring is shown to be detrimental to the trap formation. The results are in good agreement with analytic calculations in the quasistatic limit within the first-order perturbation of the scalar electric potential. The possibility of extending the single nanoring trapping properties to two-dimensional arrays of nanorings is suggested by obtaining the field distribution of nanoring dimers and trimers.

  13. Ultracold polar molecules as a quantum simulator

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    One of the main goals of quantum simulation is to experimentally realize tunable quantum systems as a way to gain insight into strongly correlated many-body phenomena. We have taken the first steps toward this goal in our system of ultracold polar KRb molecules. By encoding spin in rotational states, we have observed spin exchanges of molecules confined in a deep three-dimensional optical lattice. The interactions manifest as a density dependent decay of the spin coherence of the system. In addition, the spin contrast oscillates, with frequency components consistent with the dipolar interaction energies. We vary the interaction strength by using two different pairs of rotational states, and find the decay and oscillations to be roughly twice as fast in the case of stronger interactions. Our experiments are developing in tandem with new theory techniques to describe far-from-equilibrium, long-range interacting systems. In this way, our experiments have led to the development of improved theoretical tools which can be applied to other systems and motivate further experiments on strongly correlated quantum systems. For example, higher lattice fillings in our experiment could enable the study of transport of excitations in an out-of-equilibrium, long-range interacting system. We acknowledge funding from NIST, NSF, DOE, AFOSR-MURI, DARPA, and the NDSEG Graduate Fellowship.

  14. Novel p-wave superfluids of fermionic polar molecules

    NASA Astrophysics Data System (ADS)

    Fedorov, A. K.; Matveenko, S. I.; Yudson, V. I.; Shlyapnikov, G. V.

    2016-06-01

    Recently suggested subwavelength lattices offer remarkable prospects for the observation of novel superfluids of fermionic polar molecules. It becomes realistic to obtain a topological p-wave superfluid of microwave-dressed polar molecules in 2D lattices at temperatures of the order of tens of nanokelvins, which is promising for topologically protected quantum information processing. Another foreseen novel phase is an interlayer p-wave superfluid of polar molecules in a bilayer geometry.

  15. Novel p-wave superfluids of fermionic polar molecules

    PubMed Central

    Fedorov, A. K.; Matveenko, S. I.; Yudson, V. I.; Shlyapnikov, G. V.

    2016-01-01

    Recently suggested subwavelength lattices offer remarkable prospects for the observation of novel superfluids of fermionic polar molecules. It becomes realistic to obtain a topological p-wave superfluid of microwave-dressed polar molecules in 2D lattices at temperatures of the order of tens of nanokelvins, which is promising for topologically protected quantum information processing. Another foreseen novel phase is an interlayer p-wave superfluid of polar molecules in a bilayer geometry. PMID:27278711

  16. Novel p-wave superfluids of fermionic polar molecules.

    PubMed

    Fedorov, A K; Matveenko, S I; Yudson, V I; Shlyapnikov, G V

    2016-01-01

    Recently suggested subwavelength lattices offer remarkable prospects for the observation of novel superfluids of fermionic polar molecules. It becomes realistic to obtain a topological p-wave superfluid of microwave-dressed polar molecules in 2D lattices at temperatures of the order of tens of nanokelvins, which is promising for topologically protected quantum information processing. Another foreseen novel phase is an interlayer p-wave superfluid of polar molecules in a bilayer geometry. PMID:27278711

  17. Cross polarization and magic angle sample spinning NMR spectra of model organic compounds. 1. Highly protonated molecules

    SciTech Connect

    Alemany, L.B.; Grant, D.M.; Pugmire, R.J.; Alger, T.D.; Zilm, K.W.

    1983-04-20

    CP/MAS /sup 13/C NMR spectra were obtained at various contact times on ten solid organic compounds containing a variety of simple functional groups. The spectra show that signal intensities that agree with atomic ratios can be obtained with a contact time of 2.25 ms and often with a contact time as short as about 1 ms. Computer analysis of signal intensities obtained at a minimum of ten different contact times provides T/sub CH/ data that are consistent with these experimental results. The experimental results are also consistent with the previously reported lack of significant variation in the spectra of complex organic solids obtained with contact times of about 1 to 3 ms. In general, nonprotonated carbon atoms polarize more slowly than protonated carbon atoms. The compounds exhibit a wide range of proton spin lattice relaxation times. Some compounds exhibit more resonances than are found in the /sup 13/C(/sup 1/H) spectra of the compounds in solution because the crystalline environment removes the nominal spatial equivalence found for carbon atoms related to each other by unimolecular symmetry elements.

  18. High-Throughput Screening for Small Molecule Inhibitors of LARG-Stimulated RhoA Nucleotide Binding via a Novel Fluorescence Polarization Assay

    PubMed Central

    Evelyn, Chris R.; Ferng, Timothy; Rojas, Rafael J.; Larsen, Martha J.; Sondek, John; Neubig, Richard R.

    2009-01-01

    Guanine nucleotide-exchange factors (GEFs) stimulate guanine nucleotide exchange and the subsequent activation of Rho-family proteins in response to extracellular stimuli acting upon cytokine, tyrosine kinase, adhesion, integrin, and G-protein coupled receptors (GPCRs). Upon Rho activation, several downstream events occur, such as morphological and cytokskeletal changes, motility, growth, survival, and gene transcription. The RhoGEF Leukemia-Associated RhoGEF (LARG) is a member of the Regulators of G-protein Signaling Homology Domain (RH) family of GEFs originally identified as a result of chromosomal translocation in acute myeloid leukemia. Using a novel fluorescence polarization guanine nucleotide binding assay utilizing BODIPY-Texas Red-GTPγS (BODIPY-TR-GTPγS), we performed a ten-thousand compound high-throughput screen for inhibitors of LARG-stimulated RhoA nucleotide binding. Five compounds identified from the high-throughput screen were confirmed in a non-fluorescent radioactive guanine nucleotide binding assay measuring LARG-stimulated [35S] GTPγS binding to RhoA, thus ruling out non-specific fluorescent effects. All five compounds selectively inhibited LARG-stimulated RhoA [35S] GTPγS binding, but had little to no effect upon RhoA or Gαo [35S] GTPγS binding. Therefore, these five compounds should serve as promising starting points for the development of small molecule inhibitors of LARG-mediated nucleotide exchange as both pharmacological tools and therapeutics. In addition, the fluorescence polarization guanine nucleotide binding assay described here should serve as a useful approach for both high-throughput screening and general biological applications. PMID:19196702

  19. Continuous Optical Production of Ultracold Vibronic Ground State Polar Molecules

    NASA Astrophysics Data System (ADS)

    Bruzewicz, Colin David

    We present recent results on the formation of ultracold polar molecules via photoassociation. Beginning with pre-cooled samples of Rb and Cs atoms, we produce electronically-excited molecules that inherit the ultracold temperature of their atomic precursors. In order to create large samples of ultracold molecules in their vibrational and rotational X 1Sigma+(upsilon=J=0) ground state, we study two different photoassociative regimes. In the first, molecules are created in a particular highly vibrationally-excited molecular state and decay strongly to a weakly-bound vibrational level in the ground a3Sigma + state. To study a possible population transfer scheme from this state to the X1Sigma+(upsilon=J=0) ground state, we present high-resolution depletion spectroscopy of the a 3Sigma+ c3Sigma+ transition for use in the first stage of a proposed Stimulated Raman Adiabatic Passage (STIRAP) transfer. In the second photoassociative regime, molecules are created in deeply-bound, electronically-excited vibrational levels that decay directly to the X1Sigma+(upsilon=0) state, obviating the need for population transfer. Through theoretical analysis and subsequent experimental verification, we demonstrate continuous formation of X 1Sigma+(upsilon=0) RbCs molecules at rates in excess of 103/s. We then conclude with detailed calculations of a method to purify the molecular sample of unwanted excited molecular states, based on inelastic scattering with ultracold Cs atoms.

  20. Study of radial compression elasticity of single xanthan molecules by vibrating scanning polarization force microscopy.

    PubMed

    Wang, Huabin; Zhou, Xingfei; An, Hongjie; Sun, Jielin; Zhang, Yi; Hu, Jun

    2008-08-01

    Individual xanthan molecules were prepared on highly oriented pyrolytic graphite surface with a modified spin-casting technique. Then the radial compression elasticity of single xanthan molecules was investigated by vibrating scanning polarization force microscopy. The effective elastic moduli of xanthan molecules are estimated to be approximately 20-100 MPa under loads below 0.4 nN. PMID:19049142

  1. A quantum gas of polar molecules in an optical lattice

    NASA Astrophysics Data System (ADS)

    Moses, Steven A.

    Ultracold polar molecules, because of their long-range, spatially anisotropic interactions, are a new quantum system in which to study novel many-body phenomena. In our lab, we have produced the first quantum gas of 40K 87Rb polar molecules. These molecules were found to undergo exothermic chemical reactions, and this led to interesting studies of chemistry near absolute zero. By creating the molecules at individual sites of a 3D optical lattice, we completely suppress these chemical reactions, and the polar molecule gas becomes stable and lives for tens of seconds. This thesis documents our efforts to explore coherent, many-body phenomena resulting from long-range dipolar interactions in the lattice. By encoding a spin-1/2 system in the rotational states of the molecules, we were able to realize spin-exchange interactions based on a spin Hamiltonian, which is one of the first steps in studying quantum magnetism with polar molecules. While this study was the first realization of such coherent dipolar interactions with polar molecules in a lattice, its full potential was limited by the low lattice filling fractions. Using our ability to exquisitely control the initial atomic gas mixture, we loaded a Mott insulator of Rb and a band insulator of K into the lattice. This quantum synthesis approach led to significantly higher molecular filling fractions and represents the first fully connected system of polar molecules in an optical lattice. This low-entropy quantum gas of polar molecules opens the door to interesting quantum simulations, which should be attainable in the next generation of the experiment.

  2. High Harmonic Generation from Rotationally Excited Molecules

    NASA Astrophysics Data System (ADS)

    Lock, Robynne M.

    2011-12-01

    High harmonic generation (HHG) is understood through a three-step model. A strong laser field ionizes an atom or molecule. The free electron propagates in the laser field and may recombine with the atom or molecule leading to the generation of extreme ultraviolet or soft x-ray light at odd harmonics of the fundamental. Since the wavelength of the recombining electron is on the order of internuclear distances in molecules, HHG acts as a probe of molecular structure and dynamics. Conversely, control of the molecules leads to control of the properties (intensity, phase, and polarization) of the harmonic emission. Rotationally exciting molecules provides field-free molecular alignment at time intervals corresponding to fractions of the rotational period of the molecule. Alignment is necessary for understanding how the harmonic emission depends on molecular structure and alignment. Additionally, HHG acts as a probe of the rotational wavepackets. This thesis reports three experiments on HHG from rotationally excited molecules. Before we can use HHG as a probe of complex molecular dynamics or control harmonic properties through molecules, the harmonic emission from aligned, linear molecules must first be understood. To that end, the first experiment measures the intensity and phase of harmonics generated from N 2O and N2 near times of strong alignment revealing interferences during recombination. The second experiment demonstrates HHG as a sensitive probe of rotational wavepacket dynamics in CO2 and N2O, revealing new revival features not detected by any other probe. The final experiment focuses on understanding and controlling the polarization state of the harmonic emission. Generating elliptically polarized harmonics would be very useful for probing molecular and materials systems. We observe an elliptical dichroism in polarization-resolved measurements of the harmonic emission from aligned N2 and CO2 molecules, revealing evidence for electron-hole dynamics between the

  3. Polar confinement modulates solvation behavior of methane molecules

    NASA Astrophysics Data System (ADS)

    Xu, Weixin; Mu, Yuguang

    2008-06-01

    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.

  4. Quantum phase gate and controlled entanglement with polar molecules

    SciTech Connect

    Charron, Eric; Keller, Arne; Atabek, Osman; Milman, Perola

    2007-03-15

    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.

  5. Quantum Fluids of Self-Assembled Chains of Polar Molecules

    SciTech Connect

    Wang, D.-W.; Lukin, Mikhail D.; Demler, Eugene

    2006-11-03

    We study polar molecules in a stack of strongly confined pancake traps. When dipole moments point perpendicular to the planes of the traps and are sufficiently strong, the system is stable against collapse but attractive interaction between molecules in different layers leads to the formation of dipolar chains, analogously to the chaining phenomenon in classical rheological electro- and magnetofluids. We analyze properties of the resulting quantum liquid of dipolar chains and show that only the longest chains undergo Bose-Einstein condensation with a strongly reduced condensation temperature. We discuss several experimental methods for studying chains of polar molecules.

  6. Polarization Shaping for Unidirectional Rotational Motion of Molecules

    NASA Astrophysics Data System (ADS)

    Karras, G.; Ndong, M.; Hertz, E.; Sugny, D.; Billard, F.; Lavorel, B.; Faucher, O.

    2015-03-01

    Control of the orientation of the angular momentum of linear molecules is demonstrated by means of laser polarization shaping. For this purpose, we combine two orthogonally polarized and partially time-overlapped femtosecond laser pulses so as to produce a spinning linear polarization which in turn induces unidirectional rotation of N2 molecules. The evolution of the rotational response is probed by a third laser beam that can be either linearly or circularly polarized. The physical observable is the frequency shift imparted to the probe beam as a manifestation of the angular Doppler effect. Our experimental results are confirmed by theoretical computations, which allow one to gain a deep physical insight into the laser-molecule interaction.

  7. Polarization shaping for unidirectional rotational motion of molecules.

    PubMed

    Karras, G; Ndong, M; Hertz, E; Sugny, D; Billard, F; Lavorel, B; Faucher, O

    2015-03-13

    Control of the orientation of the angular momentum of linear molecules is demonstrated by means of laser polarization shaping. For this purpose, we combine two orthogonally polarized and partially time-overlapped femtosecond laser pulses so as to produce a spinning linear polarization which in turn induces unidirectional rotation of N2 molecules. The evolution of the rotational response is probed by a third laser beam that can be either linearly or circularly polarized. The physical observable is the frequency shift imparted to the probe beam as a manifestation of the angular Doppler effect. Our experimental results are confirmed by theoretical computations, which allow one to gain a deep physical insight into the laser-molecule interaction. PMID:25815926

  8. Reactive collisions of ultracold polar molecules

    NASA Astrophysics Data System (ADS)

    Makrides, Constantinos; Kotochigova, Svetlana; Petrov, Alexander

    2013-05-01

    There has been a recent increase in the number of experimental and theoretical efforts in describing and controlling ultra cold chemistry. A number of groups have been able to create and trap a number of cold molecules and are now looking to move into controlling more exotic molecular systems. Critical to this movement is understanding the various interactions between the atoms and molecules in the trap. We offer here a study of the these interactions using Li + LiYb as a test system of interest. Using ab initio calculations we are able to obtain the long range interactions for the current system and connect to the short range interactions to provide a description of the interaction landscape. With this information, chemical reactions such as the exchange reaction (Li + LiYb --> Yb + Li2) can be practically approached in scattering calculations. We acknowledge funding from the ARO MURI on quantum control of chemical reactions and the National Science Foundation.

  9. Enantiospecific spin polarization of electrons photoemitted through layers of homochiral organic molecules.

    PubMed

    Niño, Miguel Ángel; Kowalik, Iwona Agnieszka; Luque, Francisco Jesús; Arvanitis, Dimitri; Miranda, Rodolfo; de Miguel, Juan José

    2014-11-26

    Electrons photoemitted through layers of purely organic chiral molecules become strongly spin-polarized even at room temperature and for double-monolayer thicknesses. The substitution of one enantiomer for its mirror image does not revert the sign of the spin polarization, rather its direction in space. These findings might lead to the obtention of highly efficient spin filters for spintronic applications. PMID:25183637

  10. Polarization-dependent single-molecule spectroscopy on photosystem I

    NASA Astrophysics Data System (ADS)

    Skandary, S.; Konrad, A.; Hussels, M.; Meixner, A. J.; Brecht, M.

    2015-08-01

    Single-molecule spectroscopy (SMS) at low temperature was used to study the spectral properties, heterogeneities and spectral dynamics of the chlorophyll a (Chl a) molecules responsible for the fluorescence emission of photosystem I (PS I). The fluorescence spectra of single PS I complexes are dominated by several red-shifted Chl a molecules categorized into red pools called C708 and C719. By polarization dependent measurements we demonstrate spectrally separate emissions corresponding to C708 and C719 in single PS I monomers and trimers. Moreover, we compared the results of SMS polarization dependent between monomeric and trimeric PS I complexes and give an estimation for the orientation between these red pools. As a consequence, we get new insight into the energy transfer towards and between the red Chl a molecules in PS I complexes.

  11. Giant molecules composed of polar molecules and atoms in mixed dimensions

    NASA Astrophysics Data System (ADS)

    Qi, Ran; Tan, Shina

    2014-05-01

    Two or three polar molecules, confined to one or two dimensions, can form stable bound states with a single atom living in three dimensions, if the molecule and the atom can interact resonantly such that their mixed dimensional scattering length is large. We call these bound states ``giant molecules'' since it's a molecule composed of smaller molecules and atoms. We study their properties using techniques including exact numerical solution, exact qunatum diffusion Monte Carlo (QMC), Born-Oppenheimer approximation (BOA), and semiclassical approximation. These bound states have a hierarchical structure reminiscent of the celestial systems.

  12. Interactions between Rydberg atoms and ultracold polar molecules

    NASA Astrophysics Data System (ADS)

    Jayaseelan, Maitreyi; Haruza, Marek; Bigelow, Nicholas P.

    2015-05-01

    We investigate dipolar interactions arising in a hybrid system containing both ultracold polar molecules and atomic Rydberg states. Ultracold NaCs molecules are produced by photoassociation from laser cooled mixtures of sodium and cesium atoms and detected through resonant multi-photon ionization (REMPI). Rydberg atoms with large dipole moments are excited in the atomic cloud using a multi-photon process and detected via field-ionization. We look for evidence of the interactions in the observed spectra.

  13. Universal Matchgate Quantum Computing With Cold Polar Molecules

    NASA Astrophysics Data System (ADS)

    Herrera, Felipe

    2015-03-01

    Polar molecules in optical lattices are attractive for quantum simulation and computation due to the ability to implement a variety of spin-lattice models using static, microwave and optical fields to engineer the long-range dipolar interaction between molecular qubits. Quantum simulation of spin models requires global control over the molecular ensemble, while quantum computation requires control of individual molecules with sub-wavelength resolution. In this talk, we describe the implementation of a matchgate quantum processor with an ensemble of polar molecules in an optical lattice. The scheme uses few-body qubit encoding and sequential control of two-body dipolar interactions over small plaquetes on a square lattice to perform universal quantum computing without single-site addressing. Effective spin-spin interactions with matchgate symmetry between open-shell polar molecules (e.g., SrF, OH) are driven by two infrared control pulses in the absence of static electric fields. The resulting matchgates are robust with respect to realistic imperfections in the driving fields and lattice trapping. Applications of the architecture for the simulation of interacting fermions in quantum chemistry are discussed, considering an imperfect lattice filling.

  14. Polarization response of clathrate hydrates capsulated with guest molecules

    NASA Astrophysics Data System (ADS)

    Zeng, Qun; Li, Jinshan; Huang, Hui; Wang, Xinqin; Yang, Mingli

    2016-05-01

    Clathrate hydrates are characterized by their water cages encapsulating various guest atoms or molecules. The polarization effect of these guest-cage complexes was studied with combined density functional theory and finite-field calculations. An addition rule was noted for these systems whose total polarizability is approximately equal to the polarizability sum of the guest and the cage. However, their distributional polarizability computed with Hirshfeld partitioning scheme indicates that the guest-cage interaction has considerable influence on their polarization response. The polarization of encapsulated guest is reduced while the polarization of water cage is enhanced. The counteraction of these two opposite effects leads to the almost unchanged total polarizability. Further analysis reveals that the reduced polarizability of encapsulated guest results from the shielding effect of water cage against the external field and the enhanced polarizability of water cage from the enhanced bonding of hydrogen bonds among water molecules. Although the charge transfer through the hydrogen bonds is rather small in the water cage, the polarization response of clathrate hydrates is sensitive to the changes of hydrogen bonding strength. The guest encapsulation strengthens the hydrogen bonding network and leads to enhanced polarizability.

  15. Polarization response of clathrate hydrates capsulated with guest molecules.

    PubMed

    Zeng, Qun; Li, Jinshan; Huang, Hui; Wang, Xinqin; Yang, Mingli

    2016-05-28

    Clathrate hydrates are characterized by their water cages encapsulating various guest atoms or molecules. The polarization effect of these guest-cage complexes was studied with combined density functional theory and finite-field calculations. An addition rule was noted for these systems whose total polarizability is approximately equal to the polarizability sum of the guest and the cage. However, their distributional polarizability computed with Hirshfeld partitioning scheme indicates that the guest-cage interaction has considerable influence on their polarization response. The polarization of encapsulated guest is reduced while the polarization of water cage is enhanced. The counteraction of these two opposite effects leads to the almost unchanged total polarizability. Further analysis reveals that the reduced polarizability of encapsulated guest results from the shielding effect of water cage against the external field and the enhanced polarizability of water cage from the enhanced bonding of hydrogen bonds among water molecules. Although the charge transfer through the hydrogen bonds is rather small in the water cage, the polarization response of clathrate hydrates is sensitive to the changes of hydrogen bonding strength. The guest encapsulation strengthens the hydrogen bonding network and leads to enhanced polarizability. PMID:27250307

  16. Polarized Raman optical activity of menthol and related molecules

    NASA Astrophysics Data System (ADS)

    Barron, L. D.; Hecht, L.; Blyth, S. M.

    1989-01-01

    Polarized and depolarized Raman optical activity spectra of menthol, menthyl chloride, neomenthol and neothiomenthol from 800 to 1500 cm -1 are reported. Despite axial symmetry in all the bonds, the presence of the heteroatoms O or S seems to induce large deviations from the expected ratio of 2:1 between the polarized and depolarized Raman optical activity intensities, but Cl does not. These deviations might originate in large electric quadrupole contributions induced by excited state interactions involving O or S Rydberg p orbitals and valence orbitals on other parts of the molecule. Such interactions appear to undermine the bond polarizability theory of Raman intensities.

  17. Measuring dipolar spin exchanges in ultracold polar KRb molecules

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    By encoding spin in rotational states, we have observed spin exchanges of ultracold polar KRb molecules that are confined in a deep three dimensional optical lattice [Yan et al., Nature 501, 521 (2013)]. The interactions manifest as a density dependent decay of the spin coherence of the system, which is probed via Ramsey spectroscopy. In addition to decaying, there are oscillations in the contrast, with frequency components that are consistent with the dipolar interaction energies. By adding additional pulses, we can suppress pairwise dipolar interactions. We have studied these spin exchanges for two different pairs of rotational states, which differ by a factor of two in interaction strength, and find the decay and oscillations to be roughly twice as fast in the case of stronger interactions. This work lays the foundation for future studies of quantum magnetism with polar molecules in optical lattices. We acknowledge funding from NIST, NSF, DOE, AFOSR-MURI, DARPA, and the NDSEG Graduate Fellowship.

  18. Polar molecule reactive collisions in quasi-1D systems

    NASA Astrophysics Data System (ADS)

    Simoni, A.; Srinivasan, S.; Launay, J.-M.; Jachymski, K.; Idziaszek, Z.; Julienne, P. S.

    2015-01-01

    We study polar molecule scattering in quasi-one-dimensional geometries. Elastic and reactive collision rates are computed as a function of collision energy and electric dipole moment for different confinement strengths. The numerical results are interpreted in terms of first order scattering and of adiabatic models. Universal dipolar scattering is also discussed. Our results are relevant to experiments where control of the collision dynamics through one-dimensional confinement and an applied electric field is envisioned.

  19. Spectromicroscopy Study of the Organic Molecules Utilizing Polarized Radiation

    SciTech Connect

    Hsu, Y.J.; Wei, D.H.; Yin, G.C.; Chung, S.C.; Hu, W.S.; Tao, Y.T.

    2004-05-12

    Spectromicroscopy combined with polarized synchrotron radiation is a powerful tool for imaging and characterizing the molecular properties on surface. In this work we utilized the photoemission electron microscopy (PEEM) with linear polarized radiation provided by an elliptically polarized undulator to investigate the molecular orientations of pentacene on self-assembled monolayer (SAMs) modified gold surface and to observe the cluster domain of mixed monolayers after reorganization on silver. Varying the electric vector parallel or perpendicular to the surface, the relative intensity of {pi}* and {sigma}* transition in carbon K-edge can be used to determine the orientation of the planar-shaped pentacene molecule or long carbon chain of carboxylic acids which are important for organic semiconductor.

  20. Microwave-mediated magneto-optical trap for polar molecules

    NASA Astrophysics Data System (ADS)

    Dizhou, Xie; Wenhao, Bu; Bo, Yan

    2016-05-01

    Realizing a molecular magneto-optical trap has been a dream for cold molecular physicists for a long time. However, due to the complex energy levels and the small effective Lande g-factor of the excited states, the traditional magneto-optical trap (MOT) scheme does not work very well for polar molecules. One way to overcome this problem is the switching MOT, which requires very fast switching of both the magnetic field and the laser polarizations. Switching laser polarizations is relatively easy, but fast switching of the magnetic field is experimentally challenging. Here we propose an alternative approach, the microwave-mediated MOT, which requires a slight change of the current experimental setup to solve the problem. We calculate the MOT force and compare it with the traditional MOT and the switching MOT scheme. The results show that we can operate a good MOT with this simple setup. Project supported by the Fundamental Research Funds for the Central Universities of China.

  1. Formation of ultracold polar molecules in a single quantum state

    SciTech Connect

    Cote, Robin; Juarros, Elizabeth; Kirby, Kate

    2010-06-15

    We compute the formation rate of a polar molecule, LiH, into the lowest triplet electronic state, a {sup 3{Sigma}+}, via population of the intermediate excited electronic state, b {sup 3{Pi}}, followed by radiative decay. We find large formation rates into the single rovibrational bound state (v=0,J=0) of the a {sup 3{Sigma}+}, which can be explained by the unusually large overlap of its wave function with those of the two upper-most bound levels of the b {sup 3{Pi}}. With conservative parameters, we estimate that over 10{sup 4} molecules/s could be produced in the single rovibrational level of the a {sup 3{Sigma}+} state. We also discuss scattering properties of LiH triplet molecules and their relevance to ultracold chemical reactions.

  2. Formation of ultracold polar molecules via Raman excitation

    NASA Astrophysics Data System (ADS)

    Taylor-Juarros, E.; Côté, R.; Kirby, K.

    2004-11-01

    Alkali hydride molecules are very polar, exhibiting large ground-state dipole moments. As ultracold sources of alkali atoms, as well as hydrogen, have been created in the laboratory, we explore theoretically the feasibility of forming such molecules from a mixture of the ultracold atomic gases, employing a two-photon stimulated radiative association process — Raman excitation. Using accurate molecular potential energy curves and dipole transition moments, we have calculated the rate coefficients for populating all the vibrational levels of the X^1Σ+ state of LiH via the excited A^1Σ+ state. We have found that significant molecule formation rates can be realized with laser intensities and atomic densities that are attainable experimentally. Because of the large X state dipole moment, rapid cascade occurs down the ladder of vibrational levels to v=0. The calculated recoil momentum imparted to the molecule is small, and thus negligible trap loss results from the cascade process. This allows for the build-up of a large population of v=0 trapped molecules.

  3. Spin-orbital dynamics in a system of polar molecules

    NASA Astrophysics Data System (ADS)

    Syzranov, Sergey; Wall, Michael; Gurarie, Victor; Rey, Ana Maria

    2015-05-01

    We consider the dynamics of a two-dimensional system of ultracold polar molecules weakly perturbed from a stationary state. We demonstrate that dipole-dipole interactions in such a system generate chiral excitations with a non-trivial Berry phase 2 π . These excitations, which we call chirons, resemble low-energy quasiparticles in bilayer graphene and emerge regardless of the quantum statistics and for arbitrary ratios of kinetic to interaction energies. Chirons manifest themselves in the dynamics of the spin density profile, spin currents, and spin coherences, even for molecules pinned in a deep optical lattice. We derive the kinetic equation that describes chiron dynamics and calculate the distributions of physical observables for experimentally realisable initial conditions. This work was supported by NIST: JILA-NSF-PFC-1125844, NSF-PIF-1211914, NSF-PHY11-25915, ARO, ARO-DARPA-OLE, AFOSR, AFOSR-MURI; NSF: DMR-1001240, PHY-1125844, and the Alexander von Humboldt Foundation.

  4. Static trapping of polar molecules in a traveling wave decelerator.

    PubMed

    Quintero-Pérez, Marina; Jansen, Paul; Wall, Thomas E; van den Berg, Joost E; Hoekstra, Steven; Bethlem, Hendrick L

    2013-03-29

    We present experiments on decelerating and trapping ammonia molecules using a combination of a Stark decelerator and a traveling wave decelerator. In the traveling wave decelerator, a moving potential is created by a series of ring-shaped electrodes to which oscillating high voltages (HV) are applied. By lowering the frequency of the applied voltages, the molecules confined in the moving trap are decelerated and brought to a standstill. As the molecules are confined in a true 3D well, this kind of deceleration has practically no losses, resulting in a great improvement on the usual Stark deceleration techniques. The necessary voltages are generated by amplifying the output of an arbitrary wave generator using fast HV amplifiers, giving us great control over the trapped molecules. We illustrate this by experiments in which we adiabatically cool trapped NH3 and ND3 molecules and resonantly excite their motion. PMID:23581314

  5. A quantum gas of polar KRb molecules in an optical lattice

    NASA Astrophysics Data System (ADS)

    Covey, Jacob; Miecnikowski, Matthew; Moses, Steven; Fu, Zhengkun; Jin, Deborah; Ye, Jun

    2016-05-01

    Ultracold polar molecules provide new opportunities for investigation of strongly correlated many-body spin systems such as many-body localization and quantum magnetism. In an effort to access such phenomena, we load polar KRb molecules into a three-dimensional optical lattice. In this system, we observed many-body spin dynamics between molecules pinned in a deep lattice, even though the filling fraction of the molecules was only 5%. We have recently performed a thorough investigation of the molecule creation process in an optical lattice, and consequently improved our filling fraction to 30% by preparing and overlapping Mott and band insulators of the initial atomic gases. More recently, we switched to a second generation KRb apparatus that will allow application of large, stable electric fields as well as high-resolution addressing and detection of polar molecules in optical lattices. We plan to use these capabilities to study non-equilibrium spin dynamics in an optical lattice with nearly single site resolution. I will present the status and direction of the second generation apparatus.

  6. High polarization photocathode R D at SLAC

    SciTech Connect

    Maruyama, Takashi; Garwin, E.L. ); Prepost, R.; Zaplac, G.H. . Dept. of Physics)

    1993-01-01

    This paper describes recent progress on the development of high polarization photocathodes for polarized electron sources. A strained InGaAs cathode has achieved a maximum electron-spin polarization of 71% and has demonstrated the strain enhancement of polarization for the first time. Strained GaAs cathodes have yielded polarizations as high as 90% with much higher quantum efficiency.

  7. Charge exchange of a polar molecule at its cation

    SciTech Connect

    Buslov, E. Yu. Zon, B. A.

    2011-01-15

    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.

  8. High Intensity Polarized Electron Sources

    NASA Astrophysics Data System (ADS)

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

    2008-02-01

    During the 1990s, at numerous facilities world wide, extensive R&D devoted to constructing reliable GaAs photoguns helped ensure successful accelerator-based nuclear and high-energy physics programs using spin polarized electron beams. Today, polarized electron source technology is considered mature, with most GaAs photoguns meeting accelerator and experiment beam specifications in a relatively trouble-free manner. Proposals for new collider facilities however, require electron beams with parameters beyond today's state-of-the-art and serve to renew interest in conducting polarized electron source R&D. And at CEBAF/Jefferson Lab, there is an immediate pressing need to prepare for new experiments that require considerably more beam current than before. One experiment in particular—Q-weak, a parity violation experiment that will look for physics beyond the Standard Model—requires 180 uA average current at polarization >80% for a duration of one year, with run-averaged helicity correlated current asymmetry less than 0.1 ppm. Neighboring halls will continue taking beam during Q-weak, pushing the total average beam current from the gun beyond 300 uA. This workshop contribution describes R&D at Jefferson Lab, dedicated toward extending the operating current of polarized electron sources to meet the requirements of high current experiments at CEBAF and to better appreciate the technological challenges of new accelerators, particularly high average current machines like eRHIC that require at least 25 mA at high polarization.

  9. High frequency dynamic nuclear polarization.

    PubMed

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

    2013-09-17

    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-γ 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

  10. High Frequency Dynamic Nuclear Polarization

    PubMed Central

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

    2013-01-01

    Conspectus 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-γ nuclei such as the I = ½ species 13C or 15N. The difficulty is still greater when quadrupolar nuclei, like 17O or 27Al, 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

  11. High Intensity Polarized Electron Gun

    SciTech Connect

    Redwine, Robert P.

    2012-07-31

    The goal of the project was to investigate the possibility of building a very high intensity polarized electron gun for the Electron-Ion Collider. This development is crucial for the eRHIC project. The gun implements a large area cathode, ring-shaped laser beam and active cathode cooling. A polarized electron gun chamber with a large area cathode and active cathode cooling has been built and tested. A preparation chamber for cathode activation has been built and initial tests have been performed. Major parts for a load-lock chamber, where cathodes are loaded into the vacuum system, have been manufactured.

  12. Doublon dynamics and polar molecule production in an optical lattice.

    PubMed

    Covey, Jacob P; Moses, Steven A; Gärttner, Martin; Safavi-Naini, Arghavan; Miecnikowski, Matthew T; Fu, Zhengkun; Schachenmayer, Johannes; Julienne, Paul S; Rey, Ana Maria; Jin, Deborah S; Ye, Jun

    2016-01-01

    Polar molecules in an optical lattice provide a versatile platform to study quantum many-body dynamics. Here we use such a system to prepare a density distribution where lattice sites are either empty or occupied by a doublon composed of an interacting Bose-Fermi pair. By letting this out-of-equilibrium system evolve from a well-defined, but disordered, initial condition, we observe clear effects on pairing that arise from inter-species interactions, a higher partial-wave Feshbach resonance and excited Bloch-band population. These observations facilitate a detailed understanding of molecule formation in the lattice. Moreover, the interplay of tunnelling and interaction of fermions and bosons provides a controllable platform to study Bose-Fermi Hubbard dynamics. Additionally, we can probe the distribution of the atomic gases in the lattice by measuring the inelastic loss of doublons. These techniques realize tools that are generically applicable to studying the complex dynamics of atomic mixtures in optical lattices. PMID:27075831

  13. Doublon dynamics and polar molecule production in an optical lattice

    NASA Astrophysics Data System (ADS)

    Covey, Jacob P.; Moses, Steven A.; Gärttner, Martin; Safavi-Naini, Arghavan; Miecnikowski, Matthew T.; Fu, Zhengkun; Schachenmayer, Johannes; Julienne, Paul S.; Rey, Ana Maria; Jin, Deborah S.; Ye, Jun

    2016-04-01

    Polar molecules in an optical lattice provide a versatile platform to study quantum many-body dynamics. Here we use such a system to prepare a density distribution where lattice sites are either empty or occupied by a doublon composed of an interacting Bose-Fermi pair. By letting this out-of-equilibrium system evolve from a well-defined, but disordered, initial condition, we observe clear effects on pairing that arise from inter-species interactions, a higher partial-wave Feshbach resonance and excited Bloch-band population. These observations facilitate a detailed understanding of molecule formation in the lattice. Moreover, the interplay of tunnelling and interaction of fermions and bosons provides a controllable platform to study Bose-Fermi Hubbard dynamics. Additionally, we can probe the distribution of the atomic gases in the lattice by measuring the inelastic loss of doublons. These techniques realize tools that are generically applicable to studying the complex dynamics of atomic mixtures in optical lattices.

  14. Doublon dynamics and polar molecule production in an optical lattice

    PubMed Central

    Covey, Jacob P.; Moses, Steven A.; Gärttner, Martin; Safavi-Naini, Arghavan; Miecnikowski, Matthew T.; Fu, Zhengkun; Schachenmayer, Johannes; Julienne, Paul S.; Rey, Ana Maria; Jin, Deborah S.; Ye, Jun

    2016-01-01

    Polar molecules in an optical lattice provide a versatile platform to study quantum many-body dynamics. Here we use such a system to prepare a density distribution where lattice sites are either empty or occupied by a doublon composed of an interacting Bose-Fermi pair. By letting this out-of-equilibrium system evolve from a well-defined, but disordered, initial condition, we observe clear effects on pairing that arise from inter-species interactions, a higher partial-wave Feshbach resonance and excited Bloch-band population. These observations facilitate a detailed understanding of molecule formation in the lattice. Moreover, the interplay of tunnelling and interaction of fermions and bosons provides a controllable platform to study Bose-Fermi Hubbard dynamics. Additionally, we can probe the distribution of the atomic gases in the lattice by measuring the inelastic loss of doublons. These techniques realize tools that are generically applicable to studying the complex dynamics of atomic mixtures in optical lattices. PMID:27075831

  15. Measurement of Peptide Binding to MHC Class II Molecules by Fluorescence Polarization.

    PubMed

    Yin, Liusong; Stern, Lawrence J

    2014-01-01

    Peptide binding to major histocompatibility complex class II (MHCII) molecules is a key process in antigen presentation and CD4+ T cell epitope selection. This unit describes a fairly simple but powerful fluorescence polarization-based binding competition assay to measure peptide binding to soluble recombinant MHCII molecules. The binding of a peptide of interest to MHCII molecules is assessed based on its ability to inhibit the binding of a fluorescence-labeled probe peptide, with the strength of binding characterized as IC50 (concentration required for 50% inhibition of probe peptide binding). Data analysis related to this method is discussed. In addition, this unit includes a support protocol for fluorescence labeling peptide using an amine-reactive probe. The advantage of this protocol is that it allows simple, fast, and high-throughput measurements of binding for a large set of peptides to MHCII molecules. PMID:25081912

  16. Creation of a low-entropy quantum gas of polar molecules in an optical lattice

    NASA Astrophysics Data System (ADS)

    Moses, Steven A.; Covey, Jacob P.; Miecnikowski, Matthew T.; Yan, Bo; Gadway, Bryce; Ye, Jun; Jin, Deborah S.

    2015-11-01

    Ultracold polar molecules, with their long-range electric dipolar interactions, offer a unique platform for studying correlated quantum many-body phenomena. However, realizing a highly degenerate quantum gas of molecules with a low entropy per particle is challenging. We report the synthesis of a low-entropy quantum gas of potassium-rubidium molecules (KRb) in a three-dimensional optical lattice. We simultaneously load into the optical lattice a Mott insulator of bosonic Rb atoms and a single-band insulator of fermionic K atoms. Then, using magnetoassociation and optical state transfer, we efficiently produce ground-state molecules in the lattice at those sites that contain one Rb and one K atom. The achieved filling fraction of 25% should enable future studies of transport and entanglement propagation in a many-body system with long-range dipolar interactions.

  17. Creation of a low-entropy quantum gas of polar molecules in an optical lattice.

    PubMed

    Moses, Steven A; Covey, Jacob P; Miecnikowski, Matthew T; Yan, Bo; Gadway, Bryce; Ye, Jun; Jin, Deborah S

    2015-11-01

    Ultracold polar molecules, with their long-range electric dipolar interactions, offer a unique platform for studying correlated quantum many-body phenomena. However, realizing a highly degenerate quantum gas of molecules with a low entropy per particle is challenging. We report the synthesis of a low-entropy quantum gas of potassium-rubidium molecules (KRb) in a three-dimensional optical lattice. We simultaneously load into the optical lattice a Mott insulator of bosonic Rb atoms and a single-band insulator of fermionic K atoms. Then, using magnetoassociation and optical state transfer, we efficiently produce ground-state molecules in the lattice at those sites that contain one Rb and one K atom. The achieved filling fraction of 25% should enable future studies of transport and entanglement propagation in a many-body system with long-range dipolar interactions. PMID:26542566

  18. Enhancement of spin polarization in transport through protein-like single-helical molecules

    NASA Astrophysics Data System (ADS)

    Wu, Hai-Na; Wang, Xiao; Zhang, Ya-Jing; Yi, Guang-Yu; Gong, Wei-Jiang

    2016-06-01

    We investigate the spin-polarized electron transport through the single-helical molecules connected with two normal metallic leads. On the basis of an effective model Hamiltonian, influences of the structural parameters on the conductance and the spin polarization are calculated by using the Landauer-Büttiker formula. The optimal structural parameters for the maximal spin polarization are analyzed. Our results show that the dephasing term is an important factor to enhance the spin polarization, in addition to the intrinsic parameters of the single-helical molecule. This work can be helpful in optimizing the spin polarization in the protein-like single-helical molecules.

  19. On the correlation factor of pure polar fluids whose molecules dimerize to nonpolar dimers

    NASA Astrophysics Data System (ADS)

    Mognaschi, E. R.; Laboranti, L. M.; Chierico, A.

    The dipolar correlation of pure polar fluids whose molecules undergo dimerization, resulting in the formation of nonpolar ring dimers and polar monomers in statistical equilibrium, has been studied. Such a system has been treated as a solution of polar molecules (monomers) in an apolar solvent (dimers). This approach allowed us to introduce a new parameter that accounts for the correlation among polar monomers, besides the well known Kirkwood-Fröhlich correlation factor. A relation between the two correlation factors, involving the degree of association, has been established. The above summarized model was applied to the case of five monocarboxylic fatty acids: propionic, n-butyric, n-valeric, caprylic, and pelargonic. On going from high to low molecular mass terms the room temperature static dielectric constant of the considered series of acids increases together with the degree of association, obtained from adiabatic compressibility data on the hypothesis that only dimerization occurs. This behaviour of the static dielectric constant, unexpected on the basis of the decrease of polar monomer density due to the increase of the degree of association, has been interpreted taking into account the dipolar correlation among monomers.

  20. Deterministically Polarized Fluorescence from Single Dye Molecules Aligned in Liquid Crystal Host

    SciTech Connect

    Lukishova, S.G.; Schmid, A.W.; Knox, R.; Freivald, P.; Boyd, R. W.; Stroud, Jr., C. R.; Marshall, K.L.

    2005-09-30

    We demonstrated for the first time to our konwledge deterministically polarized fluorescence from single dye molecules. Planar aligned nematic liquid crystal hosts provide deterministic alignment of single dye molecules in a preferred direction.

  1. A microwave trap for sympathetic cooling of polar molecules

    NASA Astrophysics Data System (ADS)

    Dunseith, Devin; Truppe, Stefan; Hendricks, Richard; Sauer, Ben; Hinds, Edward; Tarbutt, Michael

    2015-03-01

    We have been developing techniques to cool molecules into the microkelvin regime. One method is to use sympathetic cooling, using ultracold atoms as a refrigerant to cool molecules. Previous work has suggested that atoms and molecules can be trapped in the antinode of a Fabry­-Pérot microwave cavity. We couple microwave power into this cavity from a rectangular waveguide via a small hole in one mirror. We have developed an analytical model that helps us understand this coupling, and gives us an idea of how the size of the hole affects the cavity's coupling and finesse. We carried out finite-­difference time­-domain simulations and performed experiments on a prototype cavity to verify this model. We have now designed and built this trap for operation under ultra­high vacuum, with the ability to cool the mirrors to 77 K and couple in up to 2 kW of microwave power. This will allow us to trap molecules with a moderate dipole moment at temperatures of hundreds of millikelvin, as well as atoms at a few millikelvin. We will present our work in creating and understanding the microwave trap, as well as our first results demonstrating trapping of lithium atoms in the microwave trap. The authors would like to thank EPSRC for supporting this work.

  2. A switched ring Stark decelerator for both light and heavy polar molecules

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    There is increasing interest in cold heavy polar molecular species for their applications in fundamental physics, such as the tests of the electron’s electric dipole moment. Here we propose a switched ring Stark decelerator suitable for slowing both light and heavy polar molecules. Two typical polar molecular species, ND3 and 205TlF, are employed to test the feasibility of our scheme with the help of trajectory calculation. Our proposed scheme is found to share many advantages with the state-of-the-art traveling wave decelerator, yet with relatively simple electronics and flexible operation modes. Sub-millikelvin molecular samples can be conveniently obtained in our decelerator using a combined operation mode. These monochromatic beams are ideal starting points for precise studies of molecular collision, cold chemistry and high-resolution spectroscopy.

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

    SciTech Connect

    Bomble, Laeetitia; Pellegrini, Philippe; Ghesquiere, Pierre; Desouter-Lecomte, Michele

    2010-12-15

    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.

  4. Dynamic nuclear polarization at high magnetic fields

    PubMed Central

    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

    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 (μw) irradiation of the sample. The maximum theoretical enhancement achievable is given by the gyromagnetic ratios (γe/γl), 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 μw and probe technology, followed by an overview of DNP applications in biological solids and liquids. Finally, we outline some possible areas for future developments. PMID:18266416

  5. High Power Polarized Positron Source

    NASA Astrophysics Data System (ADS)

    Mikhailichenko, Alexander

    2009-09-01

    We discuss the basics of polarized positron production by low energy polarized electrons. Efficiency of conversion ˜0.1-1% might be interesting for the Continuous Electron Beam Accelerator Facility (CEBAF) and the International Linear Collider (ILC).

  6. Laser-assisted Stark deceleration of polar diatomic molecules in the Χ1Σ state

    NASA Astrophysics Data System (ADS)

    Huang, Yunxia; Xu, Shuwu; Yang, Xiaohua

    2016-07-01

    The traditional Stark deceleration method is difficult to apply in chemically stable polar diatomic molecules in their ground (Χ1Σ) state because the Χ1Σ state normally experiences little Stark shift and the rovibronic ground level is mostly high-field-seeking. To solve this problem, we propose a laser-assisted Stark deceleration scheme to decelerate such molecules in the present paper. Our results show that, owing to the transverse bunching effect of the applied red-detuning laser beam, the molecules of the high-field-seeking level |J = 0, M = 0> in the Χ1Σ state can be effectively decelerated. Furthermore, the present scheme is more effective because the interaction between the molecules and the combined fields can produce the pseudo-first-order Stark effect, and thus increase the depth of the effective potential. Compared to those molecules in the low-field-seeking state |J = 1, MΩ = ‑1> in the usual electrostatic Stark deceleration, a higher molecular density and lower velocity can be achieved under an equivalent initial phase angle.

  7. Increasing the filling fraction of ultracold polar KRb molecules in a 3D optical lattice

    NASA Astrophysics Data System (ADS)

    Moses, Steven; Gadway, Bryce; Yan, Bo; Covey, Jacob; Jin, Deborah; Ye, Jun

    2013-05-01

    Gases of ultracold polar molecules with sufficiently low entropy are an ideal experimental scenario to look for signatures of long-range many-body interactions. Having a high filling fraction in a 3D lattice is one way to achieve a low entropy state. In earlier work, we showed that preformed pairs of K and Rb in a 3D lattice (sites that have exactly one K and one Rb) are converted to KRb Feshbach molecules with nearly 100% efficiency. Since the STIRAP transfer from Feshbach molecules to ground-state molecules is 90-100% efficient, loading a 3D lattice with a large fraction of preformed pairs will lead to a large filling fraction of ground-state molecules. Our scheme is to load a Mott insulator of Rb and band insulator of K. After we have loaded a lattice with a high filling fraction, we will investigate effects of dipolar interactions in a many-body system. We acknowledge funding from NIST, NSF, AFOSR-MURI, and the NDSEG Graduate Fellowship.

  8. Galactic dust polarized emission at high latitudes and CMB polarization

    NASA Astrophysics Data System (ADS)

    Prunet, S.; Sethi, S. K.; Bouchet, F. R.; Miville-Deschenes, M.-A.

    1998-11-01

    With recent instrumental advances, it might become possible to measure the polarization of the Cosmic Microwave Background (CMB), e.g. by future space missions like MAP and Planck Surveyor. In this paper, we estimate the dust polarized emission in our galaxy which is the major foreground to cope with for measuring the CMB polarization in the Wien part of CMB spectrum. We model the dust polarized emission in the galaxy using the three-dimensional HI maps of the Leiden/Dwingeloo survey at high galactic latitudes. We use the fact that the dust emission, for a wide range of wavelengths, has a tight correlation with the HI emission maps of this survey (Boulanger et al. 1996). Assuming the dust grains to be oblate with axis ratio =~ 2/3, which recent studies support, we determine the intrinsic dust polarized emissivity. The distribution of magnetic field with respect to the dust grain distribution is quite uncertain, we thus consider three extreme cases: (1) The magnetic field is aligned with the major axis of the dust structure, (2) the magnetic field has a random direction in the plane perpendicular to the direction of major axis of the dust structure, and (3) the magnetic field is unidirectional throughout. We further assume, as recent observations and theoretical analyses support, that the dust grains align with the magnetic field independently of its strength. The polarization reduction factor from misalignment of the direction of polarization from the plane of the sky and the differential polarization along a line of sight is calculated using these maps, to construct two-dimensional maps of dust polarized emission. We calculate the angular power spectrum of dust polarized emission from these maps and cast it in variables which allow a direct comparison with the polarized component of the CMB. Our results, at frequencies =~ 100 GHz, suggest that: (a) This foreground contamination is smaller than the scalar-induced polarization of the CMB at l ga 200 while the tensor

  9. [Progress in sample preparation and analytical methods for trace polar small molecules in complex samples].

    PubMed

    Zhang, Qianchun; Luo, Xialin; Li, Gongke; Xiao, Xiaohua

    2015-09-01

    Small polar molecules such as nucleosides, amines, amino acids are important analytes in biological, food, environmental, and other fields. It is necessary to develop efficient sample preparation and sensitive analytical methods for rapid analysis of these polar small molecules in complex matrices. Some typical materials in sample preparation, including silica, polymer, carbon, boric acid and so on, are introduced in this paper. Meanwhile, the applications and developments of analytical methods of polar small molecules, such as reversed-phase liquid chromatography, hydrophilic interaction chromatography, etc., are also reviewed. PMID:26753274

  10. Measurement of the nuclear polarization of hydrogen and deuterium molecules using a Lamb-shift polarimeter

    SciTech Connect

    Engels, Ralf Gorski, Robert; Grigoryev, Kiril; Mikirtychyants, Maxim; Rathmann, Frank; Seyfarth, Hellmut; Ströher, Hans; Weiss, Philipp; Kochenda, Leonid; Kravtsov, Peter; Trofimov, Viktor; Tschernov, Nikolay; Vasilyev, Alexander; Vznuzdaev, Marat; Schieck, Hans Paetz gen.

    2014-10-15

    Lamb-shift polarimeters are used to measure the nuclear polarization of protons and deuterons at energies of a few keV. In combination with an ionizer, the polarization of hydrogen and deuterium atoms was determined after taking into account the loss of polarization during the ionization process. The present work shows that the nuclear polarization of hydrogen or deuterium molecules can be measured as well, by ionizing the molecules and injecting the H{sub 2}{sup +} (or D{sub 2}{sup +}) ions into the Lamb-shift polarimeter.

  11. Small-molecule axon-polarization studies enabled by a shear-free microfluidic gradient generator

    PubMed Central

    Xu, Hui; Ferreira, Meghaan M.

    2014-01-01

    A deep understanding of the mechanisms behind neurite polarization and axon path-finding is important for interpreting how the human body guides neurite growth during development and response to injury. Further, it is of great clinical importance to identify diffusible chemical cues that promote neurite regeneration for nervous tissue repair. Despite the fast development of various types of concentration gradient generators, it has been challenging to fabricate neuron friendly (i.e. shear-free and biocompatible for neuron growth and maturation) devices to create stable gradients, particularly for fast diffusing small molecules, which typically require high flow and shear rates. Here we present a finite element analysis for a polydimethylsiloxane/polyethylene glycol diacrylate (PDMS/PEG-DA) based gradient generator, describe the microfabrication process, and validate its use for neuronal axon polarization studies. This device provides a totally shear-free, biocompatible microenvironment with a linear and stable concentration gradient of small molecules such as forskolin. The gradient profile in this device can be customized by changing the composition or width of the PEG-DA barriers during direct UV photo-patterning within a permanently bonded PDMS device. Primary rat cortical neurons (embryonic E18) exposed to soluble forskolin gradients for 72 hr exhibited statistically significant polarization and guidance of their axons. This device provides a useful platform for both chemotaxis and directional guidance studies, particularly for shear sensitive and non-adhesive cell cultures, while allowing fast new device design prototyping at a low cost. PMID:24781157

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

    SciTech Connect

    Lambertson, Glen R.

    2003-05-01

    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.

  13. Novel cathode interlayers based on neutral alcohol-soluble small molecules with a triphenylamine core featuring polar phosphonate side chains for high-performance polymer light-emitting and photovoltaic devices.

    PubMed

    Chen, Dongcheng; Zhou, Hu; Liu, Ming; Zhao, Wei-Ming; Su, Shi-Jian; Cao, Yong

    2013-04-12

    A new family of neutral alcohol-soluble small molecular materials comprised of electron-rich triphenylamine (TPA) and fluorene featuring phosphonate side chains (FEP) is reported, namely 3TPA-FEP, 2TPA-2FEP and TPA-3FEP, which have different TPA and FEP contents. Due to their good solubility in polar solvents like alcohol, multilayer devices can be fabricated by a wet process from orthogonal solvents. Polymer light-emitting devices with these materials as a cathode interlayer and Al as the cathode show greatly enhanced efficiencies in contrast to control devices without such a cathode interlayer, and their efficiencies are comparable with or even higher than devices with the low work-function metal Ba/Al as the cathode. In addition, high-performance polymer solar cells based on the poly[N-9''-hepta-decanyl-2,7-carbazole-alt-5,5-(4',7'-di-2-thienyl-2',1',3'-benzothiadiazole)] (PCDTBT):[6,6]-phenyl C71 -butyric acid methyl ester (PC71 BM) system are also achieved with power conversion efficiencies of 7.21%, 6.90% and 6.89%, by utilizing 3TPA-FEP, 2TPA-2FEP and TPA-3FEP as the cathode interlayer, respectively. These efficiencies are also much higher than those for control devices without the cathode interlayer. Although TPA is well-known as a hole-transport unit, the current findings indicate that alcohol-soluble TPA-based small molecules are also a promising cathode interlayer for both electron injection and extraction. PMID:23386362

  14. Orientational imaging of single molecules by using azimuthal and radial polarizations.

    PubMed

    Ishitobi, Hidekazu; Nakamura, Issei; Hayazawa, Norihiko; Sekkat, Zouheir; Kawata, Satoshi

    2010-03-01

    Three-dimensional molecular orientations of single fluorescence molecules in polymeric thin films were measured by focused azimuthally and radially polarized light, in which we found that the fluorescence intensity was dependent on the depth position of the molecule with respect to the film surface. We found that the fluorescence intensity for a molecule which is 80 nm deep in the film excited by radial polarization is appreciably larger when compared with the fluorescence intensity for a molecule which is also excited by radial polarization but which is closer to the polymer/air interface, a feature which leads to different fluorescence intensities, under excitation by radial polarization, for molecules with the same polar orientation but with different depths inside the film. We also found that the variation of fluorescence intensity from a molecule inside an 80 nm film in radial polarization is appreciably larger compared with one in azimuthal polarization. These findings were confirmed by comparing experiments using different thickness films with theoretically calculated electric field distributions. PMID:20146536

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

    PubMed

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

    2011-05-14

    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

  16. Investigations of electron helicity in optically active molecules using polarized beams of electrons and positrons

    NASA Technical Reports Server (NTRS)

    Gidley, D. W.; Rich, A.; Van House, J. C.; Zitzewitz, P. W.

    1981-01-01

    A positronium-formation experiment with a high sensitivity to a possible relation between the helicity of beta particles emitted in nuclear beta decay and the optical asymmetry of biological molecules is presented. The experiment is based on a mechanism in which the electrons in optically active molecules possess a helicity of less than 0.001, too weak to detect in radiolysis experiments, the sign of which depends on the chirality of the isomer. A helicity-dependent asymmetry is sought in the formation of the triplet ground state of positronium when a low-energy beam of polarized positrons of reversible helicity interacts with an optically active substance coating a channel electron multiplier. Asymmetries between positronium decays observed at positive and negative helicities for the same substance can thus be determined with a sensitivity of 0.0001, which represents a factor of 100 improvement over previous positronium experiments.

  17. Universalities in ultracold reactions of alkali-metal polar molecules

    NASA Astrophysics Data System (ADS)

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

    2011-12-01

    We consider ultracold collisions of ground-state heteronuclear alkali-metal dimers that are susceptible to four-center chemical reactions 2AB→A2+B2 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 d2 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 d6.

  18. One-photon-assisted formation of ultracold polar molecules

    NASA Astrophysics Data System (ADS)

    Juarros, Elizabeth; Pellegrini, Philippe; Kirby, Kate; Côté, Robin

    2006-04-01

    Alkali-metal hydride molecules have large dipole moments in their ground electronic states. We explore the possibility of forming such molecules from a mixture of the ultracold atomic gases, employing a one-photon stimulated radiative association process. Using accurate molecular potential-energy curves and dipole moments, we have calculated the rate coefficients for populating each of the vibrational levels of the XΣ+1 states of LiH and NaH. We have found that significant molecule formation rates into the upper vibrational levels can be realized with laser intensities and atomic densities that are easily attainable experimentally. We examine the spontaneous emission cascade which takes place from these upper vibrational levels on a time scale of milliseconds, and calculate the resulting rotational populations in v=0 . We show that photon emission in the cascade process does not contribute to trap loss and that a large population of molecules in v=0 can be achieved.

  19. Optoelectrical Cooling of Polar Molecules to Submillikelvin Temperatures

    NASA Astrophysics Data System (ADS)

    Prehn, Alexander; Ibrügger, Martin; Glöckner, Rosa; Rempe, Gerhard; Zeppenfeld, Martin

    2016-02-01

    We demonstrate direct cooling of gaseous formaldehyde (H2 CO ) to the microkelvin regime. Our approach, optoelectrical Sisyphus cooling, provides a simple dissipative cooling method applicable to electrically trapped dipolar molecules. By reducing the temperature by 3 orders of magnitude and increasing the phase-space density by a factor of ˜104, we generate an ensemble of 3 ×105 molecules with a temperature of about 420 μ K , populating a single rotational state with more than 80% purity.

  20. Highly polarized components of integrated pulse profiles

    NASA Astrophysics Data System (ADS)

    Wang, P. F.; Han, J. L.

    2016-08-01

    Highly polarized components of pulse profiles are investigated by analyzing observational data and simulating the emission processes. The highly polarized components appear at the leading or trailing part of a pulse profile, which preferably have a flat spectrum and a flat polarization angle curve compared with the low polarized components. By considering the emission processes and propagation effects, we simulate the distributions of wave modes and fractional linear polarization within the entire pulsar emission beam. We show that the highly polarized components can appear at the leading, central, and/or trailing parts of pulse profiles in the models, depending on pulsar geometry. The depolarization is caused by orthogonal modes or scattering. When a sight line cuts across pulsar emission beam with a small impact angle, the detected highly polarized component will be of the O mode, and have a flat polarization angle curve and/or a flat spectrum as observed. Otherwise, the highly polarized component will be of the X mode and have a steep polarization angle curve.

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

    PubMed

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

    2013-09-26

    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

  2. Proposal for the formation of ultracold paramagnetic polar molecules

    NASA Astrophysics Data System (ADS)

    Dulieu, Olivier; Borsalino, Dimitri; Luc, Eliane; Bouloufa-Maafa, Nadia; Zuchowski, Piotr

    2016-05-01

    Alkali-alkaline-earth dimers, such as RbCa and RbSr, possess (in their ground electronic state) both a permanent magnetic and electric dipole moment in the molecular frame, allowing their manipulation with external fields at ultracold temperatures. Such molecules have been proposed as candidates for quantum simulators. We propose an efficient method combining a photoassociation step and a stimulated Raman process to create ultracold RbSr and RbCa molecules in their absolute ground state, suitable for studying dipolar interactions in quantum gases. Our model is based on new accurate quantum chemistry computations of potential energy surfaces of ground and excited molecular states and of relevant transition dipole moments of these molecules. The results are in good agreement with recent low-resolution spectroscopic data recorded with Helium nanodroplets.

  3. Two-electron exchange interaction between polar molecules and atomic ions — Asymptotic approach

    NASA Astrophysics Data System (ADS)

    Karbovanets, Oleksandr M.; Karbovanets, Myroslav I.; Khoma, Mykhaylo V.; Lazur, Volodymyr Yu.

    2015-05-01

    We have described the asymptotic approach for calculation of the two-electron exchange interaction between atomic ion and polar molecule responsible for direct double electron transfer processes. The closed analytic expression for matrix element of exchange interaction has been obtained in the framework of the semiclassical version of the asymptotic theory and point-dipole approximation for description of the polar molecule. Contribution to the Topical Issue "Elementary Processes with Atoms and Molecules in Isolated and Aggregated States", edited by Friedrich Aumayr, Bratislav Marinkovic, Štefan Matejčik, John Tanis and Kurt H. Becker.

  4. Circular-polarization-sensitive metamaterial based on triple-quantum-dot molecules.

    PubMed

    Kotetes, Panagiotis; Jin, Pei-Qing; Marthaler, Michael; Schön, Gerd

    2014-12-01

    We propose a new type of chiral metamaterial based on an ensemble of artificial molecules formed by three identical quantum dots in a triangular arrangement. A static magnetic field oriented perpendicular to the plane breaks mirror symmetry, rendering the molecules sensitive to the circular polarization of light. By varying the orientation and magnitude of the magnetic field one can control the polarization and frequency of the emission spectrum. We identify a threshold frequency Ω, above which we find strong birefringence. In addition, Kerr rotation and circular-polarized lasing action can be implemented. We investigate the single-molecule lasing properties for different energy-level arrangements and demonstrate the possibility of circular-polarization conversion. Finally, we analyze the effect of weak stray electric fields or deviations from the equilateral triangular geometry. PMID:25526146

  5. Circular-Polarization-Sensitive Metamaterial Based on Triple-Quantum-Dot Molecules

    NASA Astrophysics Data System (ADS)

    Kotetes, Panagiotis; Jin, Pei-Qing; Marthaler, Michael; Schön, Gerd

    2014-12-01

    We propose a new type of chiral metamaterial based on an ensemble of artificial molecules formed by three identical quantum dots in a triangular arrangement. A static magnetic field oriented perpendicular to the plane breaks mirror symmetry, rendering the molecules sensitive to the circular polarization of light. By varying the orientation and magnitude of the magnetic field one can control the polarization and frequency of the emission spectrum. We identify a threshold frequency Ω , above which we find strong birefringence. In addition, Kerr rotation and circular-polarized lasing action can be implemented. We investigate the single-molecule lasing properties for different energy-level arrangements and demonstrate the possibility of circular-polarization conversion. Finally, we analyze the effect of weak stray electric fields or deviations from the equilateral triangular geometry.

  6. Effect of dipole polarizability on positron binding by strongly polar molecules

    NASA Astrophysics Data System (ADS)

    Gribakin, G. F.; Swann, A. R.

    2015-11-01

    A model for positron binding to polar molecules is considered by combining the dipole potential outside the molecule with a strongly repulsive core of a given radius. Using existing experimental data on binding energies leads to unphysically small core radii for all of the molecules studied. This suggests that electron-positron correlations neglected in the simple model play a large role in determining the binding energy. We account for these by including the polarization potential via perturbation theory and non-perturbatively. The perturbative model makes reliable predictions of binding energies for a range of polar organic molecules and hydrogen cyanide. The model also agrees with the linear dependence of the binding energies on the polarizability inferred from the experimental data (Danielson et al 2009 J. Phys. B: At. Mol. Opt. Phys. 42 235203). The effective core radii, however, remain unphysically small for most molecules. Treating molecular polarization non-perturbatively leads to physically meaningful core radii for all of the molecules studied and enables even more accurate predictions of binding energies to be made for nearly all of the molecules considered.

  7. A ratiometric solvent polarity sensing Schiff base molecule for estimating the interfacial polarity of versatile amphiphilic self-assemblies.

    PubMed

    Majumder, Rini; Sarkar, Yeasmin; Das, Sanju; Jewrajka, Suresh K; Ray, Ambarish; Parui, Partha Pratim

    2016-05-23

    A newly synthesised Schiff base molecule (PMP) existing in equilibrium between non-ionic and zwitterionic forms displays solvent polarity induced ratiometric interconversion from one form to another, such novelty being useful to detect the medium polarity. The specific interface localisation of PMP in versatile amphiphilic self-assembled systems has been exploited to monitor their interfacial polarity by evaluating such interconversion equilibrium with simple UV-Vis spectroscopy. In spite of the large differences in pH and/or viscosity between the bulk and interface, the unchanged equilibrium between the two molecular forms on varying the medium pH or viscosity provides a huge advantage for the exclusive detection of interfacial polarity. PMID:27174234

  8. Mitigation of charged impurity effects in graphene field-effect transistors with polar organic molecules (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Worley, Barrett C.; Kim, Seohee; Akinwande, Deji; Rossky, Peter J.; Dodabalapur, Ananth

    2015-09-01

    Recent developments in monolayer graphene production allow its use as the active layer in field-effect transistor technology. Favorable electrical characteristics of monolayer graphene include high mobility, operating frequency, and good stability. These characteristics are governed by such key transport physical phenomena as electron-hole transport symmetry, Dirac point voltage, and charged impurity effects. Doping of graphene occurs during device fabrication, and is largely due to charged impurities located at or near the graphene/substrate interface. These impurities cause scattering of charge carriers, which lowers mobility. Such scattering is detrimental to graphene transistor performance, but our group has shown that coating with fluoropolymer thin films or exposure to polar organic vapors can restore favorable electrical characteristics to monolayer graphene. By partially neutralizing charged impurities and defects, we can improve the mobility by approximately a factor of 2, change the Dirac voltage by fairly large amounts, and reduce the residual carrier density significantly. We hypothesize that this phenomena results from screening of charged impurities by the polar molecules. To better understand such screening interactions, we performed computational chemistry experiments to observe interactions between polar organic molecules and monolayer graphene. The molecules interacted more strongly with defective graphene than with pristine graphene, and the electronic environment of graphene was altered. These computational observations correlate well with our experimental results to support our hypothesis that polar molecules can act to screen charged impurities on or near monolayer graphene. Such screening favorably mitigates charge scattering, improving graphene transistor performance.

  9. Supersolid Phase with Cold Polar Molecules on a Triangular Lattice

    SciTech Connect

    Pollet, L.; Picon, J. D.; Buechler, H. P.; Troyer, M.

    2010-03-26

    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.

  10. Reactive collisions of ultracold polar molecules in quasi-one-dimensional traps

    NASA Astrophysics Data System (ADS)

    Idziaszek, Zbigniew; Jachymski, Krzysztof; Julienne, Paul; Simoni, Andrea

    2011-05-01

    We investigate reactive and elastic rates of quasi-one-dimensional collisions of highly reactive polar molecules. Such molecules exhibit universal near-threshold rates dependent only on the long-range part of the interaction potential,, and their collision rates are determined by the van der Waals coefficient, the dipole moment, and the trap frequency. We consider a setup with an electric field perpendicular to the axis of a quasi-one-dimensional trap. In such a geometry the reactive rates will be suppressed for sufficiently strong dipole-dipole interactions. Based on the adiabatic approximation, we calculate correlation diagrams and collision rates of some reactive bialkali molecules: KRb, LiNa, LiK, LiRb and LiCs. The adiabatic results are further verified by comparing to exact analytical expressions in the limit of a zero electric field, and to the unitarized Born approximation for elastic rates at nonzero electric fields. Supported by an AFOSR MURI and a Polish government grant.

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

    NASA Astrophysics Data System (ADS)

    Julienne, Paul; Hanna, Thomas; Idziaszek, Zbigniew

    2011-05-01

    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. 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. Supported by an AFOSR MURI and a Polish government grant.

  12. Augmented stability of hydrogen clathrate hydrates by weakly polar molecules.

    PubMed

    Nakayama, Takato; Koga, Kenichiro; Tanaka, Hideki

    2009-12-01

    Thermodynamic stability of hydrogen clathrate hydrates has been examined in a wide range of pressure based solely on the intermolecular interactions involved. We show that the stability is indeed augmented by a second guest species (here acetone) called a promoter, a consequence of which is notable reduction in the dissociation pressure of the hydrates encaging hydrogen alone. This evaluation is made by extension of the van der Waals-Platteeuw theory combined with semi-grand-canonical Monte Carlo (GCMC) simulations where the number of hydrogen molecules is allowed to vary while those of host water and promoter acetone molecules are fixed. The GCMC simulations then provide various types of cage occupancies of hydrogen from single to quadruple, from which the chemical potential of water in the clathrate hydrate is obtained as a function of the cage occupancy by acetone and the pressure. These occupancies are used to calculate the chemical potential of water in the clathrate hydrate. The stability is estimated by comparison of the chemical potential of water in the clathrate hydrate with that in hexagonal ice. We show the extent to which the dissociation pressure is reduced with increasing the occupancy of the larger cages by acetone. PMID:19968350

  13. Augmented stability of hydrogen clathrate hydrates by weakly polar molecules

    NASA Astrophysics Data System (ADS)

    Nakayama, Takato; Koga, Kenichiro; Tanaka, Hideki

    2009-12-01

    Thermodynamic stability of hydrogen clathrate hydrates has been examined in a wide range of pressure based solely on the intermolecular interactions involved. We show that the stability is indeed augmented by a second guest species (here acetone) called a promoter, a consequence of which is notable reduction in the dissociation pressure of the hydrates encaging hydrogen alone. This evaluation is made by extension of the van der Waals-Platteeuw theory combined with semi-grand-canonical Monte Carlo (GCMC) simulations where the number of hydrogen molecules is allowed to vary while those of host water and promoter acetone molecules are fixed. The GCMC simulations then provide various types of cage occupancies of hydrogen from single to quadruple, from which the chemical potential of water in the clathrate hydrate is obtained as a function of the cage occupancy by acetone and the pressure. These occupancies are used to calculate the chemical potential of water in the clathrate hydrate. The stability is estimated by comparison of the chemical potential of water in the clathrate hydrate with that in hexagonal ice. We show the extent to which the dissociation pressure is reduced with increasing the occupancy of the larger cages by acetone.

  14. Single Molecule Raman Spectroscopy Under High Pressure

    NASA Astrophysics Data System (ADS)

    Fu, Yuanxi; Dlott, Dana

    2014-06-01

    Pressure effects on surface-enhanced Raman scattering spectra of Rhdoamine 6G adsorbed on silver nanoparticle surfaces was studied using a confocal Raman microscope. Colloidal silver nanoparticles were treated with Rhodamine 6G (R6G) and its isotopically substituted partner, R6G-d4. Mixed isotopomers let us identify single-molecule spectra, since multiple-molecule spectra would show vibrational transitions from both species. The nanoparticles were embedded into a poly vinyl alcohol film, and loaded into a diamond anvil cell for the high-pressure Raman scattering measurement. Argon was the pressure medium. Ambient pressure Raman scattering spectra showed few single-molecule spectra. At moderately high pressure ( 1GPa), a surprising effect was observed. The number of sites with observable spectra decreased dramatically, and most of the spectra that could be observed were due to single molecules. The effects of high pressure suppressed the multiple-molecule Raman sites, leaving only the single-molecule sites to be observed.

  15. Polarization justified Fukui functions: The theory and applications for molecules

    NASA Astrophysics Data System (ADS)

    Komorowski, Ludwik; Lipiński, Józef; Szarek, Paweł; Ordon, Piotr

    2011-07-01

    The Fukui functions based on the computable local polarizability vector have been presented for a group of simple molecules. The necessary approximation for the density functional theory softness kernel has been supported by a theoretical analysis unifying and generalizing early concepts produced by the several authors. The exact relation between local polarizability vector and the derivative of the nonlocal part of the electronic potential over the electric field has been demonstrated. The resulting Fukui functions are unique and represent a reasonable refinement when compared to the classical ones that are calculated as the finite difference of the density in molecular ions. The new Fukui functions are strongly validated by their direct link to electron dipole polarizabilities that are reported experimentally and by other computational methods.

  16. Influence of intrinsic decoherence on tripartite entanglement and bipartite fidelity of polar molecules in pendular states.

    PubMed

    Han, Jia-Xing; Hu, Yuan; Jin, Yu; Zhang, Guo-Feng

    2016-04-01

    An array of ultracold polar molecules trapped in an external electric field is regarded as a promising carrier of quantum information. Under the action of this field, molecules are compelled to undergo pendular oscillations by the Stark effect. Particular attention has been paid to the influence of intrinsic decoherence on the model of linear polar molecular pendular states, thereby we evaluate the tripartite entanglement with negativity, as well as fidelity of bipartite quantum systems for input and output signals using electric dipole moments of polar molecules as qubits. According to this study, we consider three typical initial states for both systems, respectively, and investigate the temporal evolution with variable values of the external field intensity, the intrinsic decoherence factor, and the dipole-dipole interaction. Thus, we demonstrate the sound selection of these three main parameters to obtain the best entanglement degree and fidelity. PMID:27059571

  17. Switching surface polarization of atomic force microscopy probe utilizing photoisomerization of photochromic molecules

    SciTech Connect

    Aburaya, Yoshihiro; Nomura, Hikaru; Kageshima, Masami; Naitoh, Yoshitaka; Li, Yan Jun; Sugawara, Yasuhiro

    2011-03-15

    An attempt to develop an atomic force microscopy (AFM) probe with optically switchable polarization is described. Modification with a single molecular layer of photochromic molecules was attempted onto a Si substrate that is a prototype for a probe surface. Polarization switching caused by alternate irradiation of UV and visible lights were detected using the electrostatic force?>spectroscopy (EFS) technique. Si substrates modified with spiropyran and azobenzene exhibited reversible polarization switching that caused changes in CPD of about 100 and 50 mV, respectively. Modification with spiropyran was also attempted onto a Si probe and resulted in a CPD change of about 100 mV. It was confirmed that modification of an AFM probe or substrate with a single molecular layer of photochromic molecules can generate surface polarization switching of a mechanically detectable level.

  18. Bis(haloBODIPYs) with Labile Helicity: Valuable Simple Organic Molecules That Enable Circularly Polarized Luminescence.

    PubMed

    Ray, César; Sánchez-Carnerero, Esther M; Moreno, Florencio; Maroto, Beatriz L; Agarrabeitia, Antonia R; Ortiz, María J; López-Arbeloa, Íñigo; Bañuelos, Jorge; Cohovi, Komlan D; Lunkley, Jamie L; Muller, Gilles; de la Moya, Santiago

    2016-06-20

    Simple organic molecules (SOM) based on bis(haloBODIPY) are shown to enable circularly polarized luminescence (CPL), giving rise to a new structural design for technologically valuable CPL-SOMs. The established design comprises together synthetic accessibility, labile helicity, possibility of reversing the handedness of the circularly polarized emission, and reactive functional groups, making it unique and attractive as advantageous platform for the development of smart CPL-SOMs. PMID:27123965

  19. Polar Switching in a Lyotropic Columnar Nematic Liquid Crystal Made of Bowl-Shaped Molecules.

    PubMed

    Guilleme, Julia; Cavero, Emma; Sierra, Teresa; Ortega, Josu; Folcia, César L; Etxebarria, Jesus; Torres, Tomás; González-Rodríguez, David

    2015-08-01

    A polar response in a lyotropic columnar nematic material is reported. The material accommodates bowl-shaped molecules with strong axial dipole moments in column segments without head-to-tail invariance. Optical second-harmonic-generation methods confirm that the nematic columns align unidirectionally under an applied electric field and the material develops remnant macroscopic polarization observable for hours. The switching takes place by a flip of the columns. PMID:26078047

  20. Spin-polarized transport through single-molecule magnet Mn6 complexes

    NASA Astrophysics Data System (ADS)

    Cremades, Eduard; Pemmaraju, C. D.; Sanvito, Stefano; Ruiz, Eliseo

    2013-05-01

    The coherent transport properties of a device, constructed by sandwiching a Mn6 single-molecule magnet between two gold surfaces, are studied theoretically by using the non-equilibrium Green's function approach combined with density functional theory. Two spin states of such Mn6 complexes are explored, namely the ferromagnetically coupled configuration of the six MnIII cations, leading to the S = 12 ground state, and the low S = 4 spin state. For voltages up to 1 volt the S = 12 ground state shows a current one order of magnitude larger than that of the S = 4 state. Furthermore this is almost completely spin-polarized, since the Mn6 frontier molecular orbitals for S = 12 belong to the same spin manifold. As such the high-anisotropy Mn6 molecule appears as a promising candidate for implementing, at the single molecular level, both spin-switches and low-temperature spin-valves.The coherent transport properties of a device, constructed by sandwiching a Mn6 single-molecule magnet between two gold surfaces, are studied theoretically by using the non-equilibrium Green's function approach combined with density functional theory. Two spin states of such Mn6 complexes are explored, namely the ferromagnetically coupled configuration of the six MnIII cations, leading to the S = 12 ground state, and the low S = 4 spin state. For voltages up to 1 volt the S = 12 ground state shows a current one order of magnitude larger than that of the S = 4 state. Furthermore this is almost completely spin-polarized, since the Mn6 frontier molecular orbitals for S = 12 belong to the same spin manifold. As such the high-anisotropy Mn6 molecule appears as a promising candidate for implementing, at the single molecular level, both spin-switches and low-temperature spin-valves. Electronic supplementary information (ESI) available: Calculated total and projected density of states of an isolated [Mn6O2(Et-sao)6{O2CPh(Me)2}2(EtOH)6] original SMM complex (Fig. S1). Calculated total and projected

  1. High Energy Polarized e+e‑ Beams

    NASA Astrophysics Data System (ADS)

    Shatunov, Yu.; Koop, I.; Otboev, A.; Mane, S.

    2016-02-01

    Recently, the wide discussion about Higgs-factory design again returns to problem of high energy polarized electrons and positrons. It’s good known the radiative beam polarization at LEP-collider. It was obtained after spin resonance suppression at Z0 pick, but didn’t appear at energies above 70 GeV due to an enhancement of unavoidable depolarization effects. We examine in this paper various ideas for radiative polarization at TLEP/FCC-ee and formulate some estimates for the polarization buildup time and the asymptotic polarization. Using wigglers, a useful degree of polarization (for energy calibration), with a time constant of about 1 h, may be possible up to the threshold of W pair production. At higher energies such as the threshold of Higgs production, attaining a useful level of polarization may be difficult in a planar ring. With Siberian Snakes, wigglers and some imagination, polarization of reasonable magnitude, with a reasonable time constant (of not more than about 1 h), may be achievable at very high energies.

  2. Managing light polarization via plasmon-molecule interactions within an asymmetric metal nanoparticle trimer

    SciTech Connect

    Shegai, Timur; Li, Zhipeng; Zhang, Zhenyu; Xu, Hongxing; Haran, Gilad

    2008-01-01

    The interaction of light with metal nanoparticles leads to novel phenomena mediated by surface plasmon excitations. In this paper we use single molecules to characterize the interaction of surface plasmons with light, and show that such interaction can strongly modulate the polarization of the emitted light. The simplest nanostructures that enable such polarization modulation are asymmetric silver nanocrystal trimers, where individual Raman scattering molecules are located in the gap between two of the nanoparticles. The third particle breaks the dipolar symmetry of the two-particle junction, generating a wavelength-dependent polarization pattern. Indeed, the scattered light becomes elliptically polarized and its intensity pattern is rotated in the presence of the third particle. We use a combination of spectroscopic observations on single molecules, scanning electron microscope imaging, and generalized Mie theory calculations to provide a full picture of the effect of particles on the polarization of the emitted light. Furthermore, our theoretical analysis allows us to show that the observed phenomenon is very sensitive to the size of the trimer particles and their relative position, suggesting future means for precise control of light polarization on the nanoscale.

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

    SciTech Connect

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

    2011-02-15

    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.

  4. Polarization properties of light scattered off solutions of chiral molecules in non-forward direction

    NASA Astrophysics Data System (ADS)

    Vidal, Xavier; Fernandez-Corbaton, Ivan; Barbara, Alex F.; Molina-Terriza, Gabriel

    2015-11-01

    Measuring the optical activity from an ensemble of chiral molecules is a common tool to know their stereo-structure. These measurements are done in the same propagation direction of the probe beam of light, because that is the direction where most signal is emitted. We provide experimental and theoretical evidence that, even though other interesting information may be gathered when collecting light emitted in other directions, for most molecules, the phenomenon of optical activity is only present in the forward scattering direction. The fundamental reason behind this is that forward scattered light preserves the circular polarization states due to the cylindrical symmetry of the system, an essential requirement for optical activity. An important exemption happens in dual molecules, i.e., molecules which present the same response to electric and magnetic fields. We present a series of experiments measuring the optical activity and the scattering of chiral solutions in the forward and perpendicular directions. We experimentally show that these molecules present optical activity and preservation of circular polarization in the forward direction, while the polarization pattern in non-forward directions is much more complex and, in particular, does not preserve the circular polarization. Finally, we show that when probing the particle with different wavelengths, the scattering in non-forward directions presents some interesting structural features which are hidden in the forward measurements.

  5. Polarization properties of light scattered off solutions of chiral molecules in non-forward direction

    SciTech Connect

    Vidal, Xavier Barbara, Alex F.; Fernandez-Corbaton, Ivan; Molina-Terriza, Gabriel

    2015-11-23

    Measuring the optical activity from an ensemble of chiral molecules is a common tool to know their stereo-structure. These measurements are done in the same propagation direction of the probe beam of light, because that is the direction where most signal is emitted. We provide experimental and theoretical evidence that, even though other interesting information may be gathered when collecting light emitted in other directions, for most molecules, the phenomenon of optical activity is only present in the forward scattering direction. The fundamental reason behind this is that forward scattered light preserves the circular polarization states due to the cylindrical symmetry of the system, an essential requirement for optical activity. An important exemption happens in dual molecules, i.e., molecules which present the same response to electric and magnetic fields. We present a series of experiments measuring the optical activity and the scattering of chiral solutions in the forward and perpendicular directions. We experimentally show that these molecules present optical activity and preservation of circular polarization in the forward direction, while the polarization pattern in non-forward directions is much more complex and, in particular, does not preserve the circular polarization. Finally, we show that when probing the particle with different wavelengths, the scattering in non-forward directions presents some interesting structural features which are hidden in the forward measurements.

  6. Monitoring Nanoscale Deformations in a Drawn Polymer Melt with Single-Molecule Fluorescence Polarization Microscopy.

    PubMed

    Krause, Stefan; Neumann, Martin; Fröbe, Melanie; Magerle, Robert; von Borczyskowski, Christian

    2016-02-23

    Elongating a polymer melt causes polymer segments to align and polymer coils to deform along the drawing direction. Despite the importance of this molecular response for understanding the viscoelastic properties and relaxation behavior of polymeric materials, studies on the single-molecule level are rare and were not performed in real time. Here we use single-molecule fluorescence polarization microscopy for monitoring the position and orientation of single fluorescent perylene diimide molecules embedded in a free-standing thin film of a polymethyl acrylate (PMA) melt with a time resolution of 500 ms during the film drawing and the subsequent stress relaxation period. The orientation distribution of the perylene diimide molecules is quantitatively described with a model of rod-like objects embedded in a uniaxially elongated matrix. The orientation of the fluorescent probe molecules is directly coupled to the local deformation of the PMA melt, which we derive from the distances between individual dye molecules. In turn, the fluorescence polarization monitors the shape deformation of the polymer coils on a length scale of 5 nm. During stress relaxation, the coil shape relaxes four times more slowly than the mechanical stress. This shows that stress relaxation involves processes on length scales smaller than a polymer coil. Our work demonstrates how optical spectroscopy and microscopy can be used to study the coupling of individual fluorescent probe molecules to their embedding polymeric matrix and to an external mechanical stimulus on the single-molecule level. PMID:26831762

  7. Near-circularly polarized single attosecond pulse generation from nitrogen molecules in spatially inhomogeneous laser fields

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaofan; Li, Yang; Zhu, Xiaosong; Zhang, Qingbin; Lan, Pengfei; Lu, Peixiang

    2016-01-01

    The generation of an attosecond pulse in nitrogen molecules using spatially inhomogeneous laser fields is investigated by numerically solving the time-dependent Schrödinger equation. It is found that an isolated attosecond pulse with elliptical polarization can be generated using linearly polarized laser fields. By changing polarization direction with respect to the molecular axis, the ellipticity of the attosecond pulse can be easily controlled. At some specific angles, the intensities of the two mutually vertical harmonic components, parallel and perpendicular to the driving laser polarization direction, are comparable. Additionally, the relative phase between the two components is about π/2. As a result, it supports the generation of the isolated near-circularly polarized attosecond pulse with a duration of 155 as.

  8. High Energy Polarization of Blazars: Detection Prospects

    NASA Astrophysics Data System (ADS)

    Chakraborty, N.; Pavlidou, V.; Fields, B. D.

    2015-01-01

    Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (with X-Calibur offering the most promising prospects), space-based missions should detect the brightest blazars for polarization fractions down to a few percent. Typical flaring activity of blazars could boost the overall number of polarimetric detections by nearly a factor of five to six purely accounting for flux increase of the brightest of the comprehensive, all-sky, Fermi-LAT blazar distribution. The instantaneous increase in the number of detections is approximately a factor of two, assuming a duty cycle of 20% for every source. The detectability of particular blazars may be reduced if variations in the flux and polarization fraction are anticorrelated. Simultaneous use of variability and polarization trends could guide the selection of blazars for high-energy polarimetric observations.

  9. HIGH ENERGY POLARIZATION OF BLAZARS: DETECTION PROSPECTS

    SciTech Connect

    Chakraborty, N.; Pavlidou, V.; Fields, B. D.

    2015-01-01

    Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (with X-Calibur offering the most promising prospects), space-based missions should detect the brightest blazars for polarization fractions down to a few percent. Typical flaring activity of blazars could boost the overall number of polarimetric detections by nearly a factor of five to six purely accounting for flux increase of the brightest of the comprehensive, all-sky, Fermi-LAT blazar distribution. The instantaneous increase in the number of detections is approximately a factor of two, assuming a duty cycle of 20% for every source. The detectability of particular blazars may be reduced if variations in the flux and polarization fraction are anticorrelated. Simultaneous use of variability and polarization trends could guide the selection of blazars for high-energy polarimetric observations.

  10. Copper Keplerates: High-Symmetry Magnetic Molecules.

    PubMed

    Palacios, Maria A; Moreno Pineda, Eufemio; Sanz, Sergio; Inglis, Ross; Pitak, Mateusz B; Coles, Simon J; Evangelisti, Marco; Nojiri, Hiroyuki; Heesing, Christian; Brechin, Euan K; Schnack, Jürgen; Winpenny, Richard E P

    2016-01-01

    Keplerates are molecules that contain metal polyhedra that describe both Platonic and Archimedean solids; new copper keplerates are reported, with physical studies indicating that even where very high molecular symmetry is found, the low-temperature physics does not necessarily reflect this symmetry. PMID:26530901

  11. Deceleration and Trapping of Polar Molecules using Time-varying Electric Fields

    NASA Astrophysics Data System (ADS)

    Bethlem, Hendrick L.

    2004-03-01

    Over the last two decades, physicists have steadily learned to control the motion of particles, ranging from neutrons, to ions, atoms and finally molecules. These methods have led to a renaissance in atomic physics and have the potential to do the same for molecular physics. Ultracold atoms are used in time standards and in precision tests of quantum electrodynamics and various other fundamental physics theories. Atom cooling methods have also made possible the realization of Bose-Einstein condensation in dilute atomic vapors and the atom laser. Not surprisingly, physicists and chemists now want to perform the same tricks with molecules. But molecules have much more to offer than simply extending the experiments already performed with atoms to more complex species. For instance, the dipole-dipole interaction in a molecular Bose-Einstein condensate gives a molecular condensate new and intriguing properties. Polar Fermi gases may be used to observe the superfluid transition. Cooling molecules will also make it possible to improve the resolution of various fundamental physics studies. For instance, specific molecules such as YbF and PbO are considered ideal for testing the time reversal symmetry postulate and chiral molecules are being used to study parity violation. Furthermore, cold molecules offer various interesting possibilities for chemistry. Cooling molecules to ultracold temperatures gives access to an exotic regime for chemical reactivity, where the thermal de Broglie wavelength exceeds the size of the collision complex. Similarly, the formation of long-lived, transiently bound molecular complexes enables reactions to occur via tunnelling through reaction barriers, thus opening novel routes for low-temperature chemistry. Over the last few years we have been involved in a project to decelerate a pulsed beam of dipolar molecules by time-varying electric fields. A polar molecule experiences a force in an inhomogeneous electric field. Using this force neutral

  12. Prospects for quantum computing with an array of ultracold polar paramagnetic molecules.

    PubMed

    Karra, Mallikarjun; Sharma, Ketan; Friedrich, Bretislav; Kais, Sabre; Herschbach, Dudley

    2016-03-01

    Arrays of trapped ultracold molecules represent a promising platform for implementing a universal quantum computer. DeMille [Phys. Rev. Lett. 88, 067901 (2002)] has detailed a prototype design based on Stark states of polar (1)Σ molecules as qubits. Herein, we consider an array of polar (2)Σ molecules which are, in addition, inherently paramagnetic and whose Hund's case (b) free-rotor pair-eigenstates are Bell states. We show that by subjecting the array to combinations of concurrent homogeneous and inhomogeneous electric and magnetic fields, the entanglement of the array's Stark and Zeeman states can be tuned and the qubit sites addressed. Two schemes for implementing an optically controlled CNOT gate are proposed and their feasibility discussed in the face of the broadening of spectral lines due to dipole-dipole coupling and the inhomogeneity of the electric and magnetic fields. PMID:26957163

  13. Prospects for quantum computing with an array of ultracold polar paramagnetic molecules

    NASA Astrophysics Data System (ADS)

    Karra, Mallikarjun; Sharma, Ketan; Friedrich, Bretislav; Kais, Sabre; Herschbach, Dudley

    2016-03-01

    Arrays of trapped ultracold molecules represent a promising platform for implementing a universal quantum computer. DeMille [Phys. Rev. Lett. 88, 067901 (2002)] has detailed a prototype design based on Stark states of polarmolecules as qubits. Herein, we consider an array of polarmolecules which are, in addition, inherently paramagnetic and whose Hund's case (b) free-rotor pair-eigenstates are Bell states. We show that by subjecting the array to combinations of concurrent homogeneous and inhomogeneous electric and magnetic fields, the entanglement of the array's Stark and Zeeman states can be tuned and the qubit sites addressed. Two schemes for implementing an optically controlled CNOT gate are proposed and their feasibility discussed in the face of the broadening of spectral lines due to dipole-dipole coupling and the inhomogeneity of the electric and magnetic fields.

  14. How small polar molecules protect membrane systems against osmotic stress: the urea-water-phospholipid system.

    PubMed

    Costa-Balogh, Fátima O; Wennerström, Håkan; Wadsö, Lars; Sparr, Emma

    2006-11-30

    We investigate how a small polar molecule, urea, can act to protect a phospholipid bilayer system against osmotic stress. Osmotic stress can be caused by a dry environment, by freezing, or by exposure to aqueous systems with high osmotic pressure due to solutes like in saline water. A large number of organisms regularly experience osmotic stress, and it is a common response to produce small polar molecules intracellularly. We have selected a ternary system of urea-water-dimyristoyl phosphatidylcholine (DMPC) as a model to investigate the molecular mechanism behind this protective effect, in this case, of urea, and we put special emphasis on the applications of urea in skin care products. Using differential scanning calorimetry, X-ray diffraction, and sorption microbalance measurements, we studied the phase behavior of lipid systems exposed to an excess of solvent of varying compositions, as well as lipid systems exposed to water at reduced relative humidities. From this, we have arrived at a rather detailed thermodynamic characterization. The basic findings are as follows: (i) In excess solvent, the thermally induced lipid phase transitions are only marginally dependent on the urea content, with the exception being that the P(beta) phase is not observed in the presence of urea. (ii) For lipid systems with limited access to solvent, the phase behavior is basically determined by the amount (volume) of solvent irrespective of the urea content. (iii) The presence of urea has the effect of retaining the liquid crystalline phase at relative humidities down to 64% (at 27 degrees C), whereas, in the absence of urea, the transition to the gel phase occurs already at a relative humidity of 94%. This demonstrates the protective effect of urea against osmotic stress. (iv) In skin care products, urea is referred to as a moisturizer, which we find slightly misleading as it replaces the water while keeping the physical properties unaltered. (v) In other systems, urea is known to

  15. Production of Highly Polarized Positrons Using Polarized Electrons at MeV Energies

    NASA Astrophysics Data System (ADS)

    Abbott, D.; Adderley, P.; Adeyemi, A.; Aguilera, P.; Ali, M.; Areti, H.; Baylac, M.; Benesch, J.; Bosson, G.; Cade, B.; Camsonne, A.; Cardman, L. S.; Clark, J.; Cole, P.; Covert, S.; Cuevas, C.; Dadoun, O.; Dale, D.; Dong, H.; Dumas, J.; Fanchini, E.; Forest, T.; Forman, E.; Freyberger, A.; Froidefond, E.; Golge, S.; Grames, J.; Guèye, P.; Hansknecht, J.; Harrell, P.; Hoskins, J.; Hyde, C.; Josey, B.; Kazimi, R.; Kim, Y.; Machie, D.; Mahoney, K.; Mammei, R.; Marton, M.; McCarter, J.; McCaughan, M.; McHugh, M.; McNulty, D.; Mesick, K. E.; Michaelides, T.; Michaels, R.; Moffit, B.; Moser, D.; Muñoz Camacho, C.; Muraz, J.-F.; Opper, A.; Poelker, M.; Réal, J.-S.; Richardson, L.; Setiniyaz, S.; Stutzman, M.; Suleiman, R.; Tennant, C.; Tsai, C.; Turner, D.; Ungaro, M.; Variola, A.; Voutier, E.; Wang, Y.; Zhang, Y.; PEPPo Collaboration

    2016-05-01

    The Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous Electron Beam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization from electrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electron beam in a high-Z target. Positron polarization up to 82% have been measured for an initial electron beam momentum of 8.19 MeV /c , limited only by the electron beam polarization. This technique extends polarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positron beam physics to a wide community.

  16. Production of Highly Polarized Positrons Using Polarized Electrons at MeV Energies.

    PubMed

    Abbott, D; Adderley, P; Adeyemi, A; Aguilera, P; Ali, M; Areti, H; Baylac, M; Benesch, J; Bosson, G; Cade, B; Camsonne, A; Cardman, L S; Clark, J; Cole, P; Covert, S; Cuevas, C; Dadoun, O; Dale, D; Dong, H; Dumas, J; Fanchini, E; Forest, T; Forman, E; Freyberger, A; Froidefond, E; Golge, S; Grames, J; Guèye, P; Hansknecht, J; Harrell, P; Hoskins, J; Hyde, C; Josey, B; Kazimi, R; Kim, Y; Machie, D; Mahoney, K; Mammei, R; Marton, M; McCarter, J; McCaughan, M; McHugh, M; McNulty, D; Mesick, K E; Michaelides, T; Michaels, R; Moffit, B; Moser, D; Muñoz Camacho, C; Muraz, J-F; Opper, A; Poelker, M; Réal, J-S; Richardson, L; Setiniyaz, S; Stutzman, M; Suleiman, R; Tennant, C; Tsai, C; Turner, D; Ungaro, M; Variola, A; Voutier, E; Wang, Y; Zhang, Y

    2016-05-27

    The Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous Electron Beam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization from electrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electron beam in a high-Z target. Positron polarization up to 82% have been measured for an initial electron beam momentum of 8.19  MeV/c, limited only by the electron beam polarization. This technique extends polarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positron beam physics to a wide community. PMID:27284661

  17. Production of Highly Polarized Positrons Using Polarized Electrons at MeV Energies

    DOE PAGESBeta

    Abbott, D.; Adderley, P.; Adeyemi, A.; Aguilera, P.; Ali, M.; Areti, H.; Baylac, M.; Benesch, J.; Bosson, G.; Cade, B.; et al

    2016-05-27

    The Polarized Electrons for Polarized Positrons experiment at the injector of the Continuous Electron Beam Accelerator Facility has demonstrated for the first time the efficient transfer of polarization from electrons to positrons produced by the polarized bremsstrahlung radiation induced by a polarized electron beam in a high-Z target. Positron polarization up to 82% have been measured for an initial electron beam momentum of 8.19~MeV/c, limited only by the electron beam polarization. We report that this technique extends polarized positron capabilities from GeV to MeV electron beams, and opens access to polarized positron beam physics to a wide community.

  18. Electric manipulation of ultracold polar ^40K^87Rb molecules in a magnetic field

    NASA Astrophysics Data System (ADS)

    Quéméner, Goulven; Bohn, John

    2009-05-01

    Ultracold fermionic polar molecules of ^40K^87Rb in their absolute rovibronic ground state (v=0,n=0,^1σ) have been created recently [1] in a magnetic trap and open new perspectives to create fermionic degenerate gases of polar molecules. To achieve this goal, it is very important to understand the collisional properties of such molecules under magnetic and electric fields. In our presentation, we investigate ground state fermionic ^40K^87Rb + ^40K^87Rb collisions in the presence of a magnetic field and explore the possibility to control these collisions when an electric field is applied. We will explore the main physical processes that can lead to such manipulation. This problem is complicated by the Zeeman and Stark splitting of all levels of the polar molecules and by the possibility of forming ^40K2 + ^87Rb2 chemical products. 1 - K.-K. Ni, S. Ospelkaus, M. H. G. de Miranda, A. Pe'er, B. Neyenhuis, J. J. Zirbel, S. Kotochigova, P. S. Julienne, D. S. Jin, and J. Ye, Science 322, 231 (2008).

  19. Systematic analysis of long-range interactions between vibrating polar bialkali molecules

    NASA Astrophysics Data System (ADS)

    Dulieu, Olivier; Vexiau, Romain; Lepers, Maxence; Aymar, Mireille; Bouloufa, Nadia

    2012-06-01

    The determination of the long-range anisotropic interactions between polar bialkali molecules is of crucial importance for the achievement of a quantum gas of ultracold polar molecules. In particular, the dispersion coefficient C6 of the van der Waals interaction depends on the dynamic polarizability of the molecule evaluated at imaginary frequencies, expressed as a sum over all possible radiative transitions of electronic dipole moments. Using a mixture of up-to-date spectroscopic data and accurate ab initio data for potential energy curves, and permanent and transition dipole moments, we have obtained the values of the dispersion coefficients between identical polar molecules (LiNa, LiK, LiRb, LiCs, NaK, NaRb, NaCs, KRb, KCs, RbCs) in an arbitrary vibrational level of their electronic ground state. A careful analysis of the importance of the various kinds of transitions contributing to the sum has been performed. The C6 values significantly decrease with increasing vibrational levels towards the sum of the C6 coefficients between the four involved atomic pairs. For the lowest vibrational levels the C6 parameter varies from about 10^4 atomic units for KRb up to 10^7 atomic units for NaCs, which will lead to different collisional regimes at ultracold temperature.

  20. High-harmonic generation in aligned water molecules

    NASA Astrophysics Data System (ADS)

    Wang, Song; Devin, Julien; Hoffmann, Matthias; Cryan, James; Kaldun, Andreas; Bucksbaum, Philip

    2016-05-01

    In recent years, the use of high harmonic generation (HHG) in aligned molecular vapors has become a powerful tool to study ultrafast dynamics of electronic and nuclear wave packets. In our new experimental setup, we are able to orient H2 O and D2 O molecules using a single cycle terahertz (THz) pulse. Aligning water is especially interesting as the highest occupied molecular orbital (HOMO) of water contains a node in the xz plane of the molecular frame, allowing us to perform HHG from second highest occupied molecular orbital (HOMO-1) only, by setting the polarization of the fundamental laser along the z-axis of the aligned water molecules. We are particularly interested in the HOMO-1 state, as there is fast motion of the H-O-H angle leading to sub-wavelength dynamics. On this poster we present our all-optical alignment setup where HHG and single-cycle THz generation take place in high-vacuum, where measurements with arbitrary polarization angles between the two are possible. In addition, we discuss the effects of the molecular orientation on HHG, including symmetry breaking that could produce even harmonics and isotope effects between H2 O and D2 O due to different vibrational energies. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division.

  1. Highly stretchable, printable nanowire array optical polarizers.

    PubMed

    Kwon, Soonshin; Lu, Dylan; Sun, Zhelin; Xiang, Jie; Liu, Zhaowei

    2016-09-21

    Designing optical components such as polarizers on substrates with high mechanical deformability have potential to realize new device platforms in photonics, wearable electronics, and sensors. Conventional manufacturing approaches that rely highly on top-down lithography, deposition and the etching process can easily confront compatibility issues and high fabrication complexity. Therefore, an alternative integration scheme is necessary. Here, we demonstrate fabrication of highly flexible and stretchable wire grid polarizers (WGPs) by printing bottom-up grown Ge or Ge/Si core/shell nanowires (NWs) on device substrates in a highly dense and aligned fashion. The maximum contrast ratio of 104 between transverse electric (TE) and transverse magnetic (TM) fields and above 99% (maximum 99.7%) of light blocking efficiency across the visible spectrum range are achieved. Further systematic analyses are performed both in experimental and numerical models to reveal the correspondence between physical factors (coverage ratio of NW arrays and diameter) and polarization efficiency. Moreover, we demonstrate distinctive merits of our approach: (i) high flexibility in the choice of substrates such as glass, plastic, or elastomer; (ii) easy combination with additional novel functionalities, for example, air permeability, flexibility/stretchability, biocompatibility, and a skin-like low mechanical modulus; (iii) selective printing of polarizers on a designated local area. PMID:27537105

  2. Novel high-sensitivity fluorescence polarization reader

    NASA Astrophysics Data System (ADS)

    Hoyt, Clifford C.; Levenson, Richard M.; Banks, Peter

    2001-05-01

    We have developed a new fluorescence polarization (FP) reader suitable for high-throughput screening (HST) and ultra-HTS whose assay-performance and sample-throughput are both considerably improved over present state-of-the-art instrumentation. The SymmetryTM reader possesses a number of features that differ from conventional HTS FP readers. These include: laser-based excitation, liquid crystal polarization optics that rapidly and accurately measure polarization states; and CCD detectors to capture emission from multiple wells. We show that the performance in assays relevant to the drug discovery process, such as G- protein coupled receptor-based assays, is significantly enhanced due to a dramatic improvement in precision. Furthermore, the CCD-detection system used can substantially improve sample throughput compared to sequential readers while maintaining high performance.

  3. Field-free molecular alignment of asymmetric top molecules using elliptically polarized laser pulses

    NASA Astrophysics Data System (ADS)

    Rouzée, A.; Guérin, S.; Faucher, O.; Lavorel, B.

    2008-04-01

    We show theoretically that a short specific elliptically polarized laser pulse driving an asymmetric top molecule can induce postpulse revivals of three-dimensional (3D) alignment. By choosing the field ellipticity resulting in the best compromise between the alignment of two molecular axes, we demonstrate that efficient 3D alignment can be achieved at low temperature. In the experiment, the field-free alignment of moderately cool ethylene molecules is probed by using a technique based on the optical Kerr effect. Control of 3D field-free alignment opens the door to a large range of applications in chemistry as well as in molecular optics.

  4. Pseudo-polar tilted smectic phases exhibited by bent-core hockey stick shaped molecules.

    PubMed

    Malkar, Deepshika; Sadashiva, B K; Roy, Arun

    2016-06-14

    We report experimental and theoretical studies on two new achiral fluid lamellar phases exhibited by bent-core hockey stick shaped molecules. The packing of these bent-core hockey stick shaped molecules in the layers leads to a pseudo-polar order in these tilted smectic phases. An anticlinic SmCA type stacking of the pseudo-polar layers is observed in the higher temperature smectic phase, while in the lower temperature phase the difference in the azimuthal angles of the tilt directions in successive layers is between zero and π with a randomized tilt organization between the successive layers. The randomness arises due to the sign degeneracy of the azimuthal angle difference of the tilt directions in successive layers. Both of these smectic phases show a strong electro-optic response which can be exploited for potential applications. PMID:27157895

  5. Molecule-modulated photoconductivity and gain-amplified selective gas sensing in polar GaN nanowires

    NASA Astrophysics Data System (ADS)

    Chen, R. S.; Lu, C. Y.; Chen, K. H.; Chen, L. C.

    2009-12-01

    We report the strong molecular effects on the surface-dominant photoconductivity with high-gain transport in the polar GaN nanowires. Both the transient and steady-state photocurrents are sensitive and selective to the adsorptions of oxygen and hydrogen. The surface band bending of GaN nanowires is proposed to be effectively reduced or enhanced by oxygen or hydrogen, respectively, as a donorlike or acceptorlike surface state. The molecular effect, corroborated with the high-gain photoresponse nature of GaN nanowires is found to amplify the molecule-selective photocurrent signal by near three orders of magnitude higher than its counterpart in dark current. The molecule-tunable photoconductivity, as demonstrated here, would benefit a variety of applications, ranging from the high-gain optoelectronic devices, photoelectric energy transducer, as well as gas and chemical sensors.

  6. Polarization propagator approach to the dynamic nuclear electric shielding in LiH molecule

    NASA Astrophysics Data System (ADS)

    Lazzeretti, P.; Rossi, E.; Zanasi, R.

    1983-07-01

    The frequency dependence of the dipole electric polarizability and electric shielding tensors of hydrogen and lithium nuclei in the LiH molecule has been studied via some approximations to the polarization propagator method, i.e., STA, TDA, and RPA, allowing for dipole length, velocity, acceleration, and mixed formalisms. The RPA nuclear electric shieldings are in a fairly good agreement with the corresponding experimental data, a discrepancy being observed for the parallel component at the Li nucleus.

  7. Field-free orientation of diatomic molecule via the linearly polarized resonant pulses

    NASA Astrophysics Data System (ADS)

    Li, Su-Yu; Guo, Fu-Ming; Wang, Jun; Yang, Yu-Jun; Jin, Ming-Xing

    2015-10-01

    We propose a scheme to coherently control the field-free orientation of NO molecule whose rotational temperature is above 0 K. It is found that the maximum molecular orientation is affected by two factors: one is the sum of the population of M = 0 rotational states and the other is their distribution, however, their distribution plays a much more significant role in molecular orientation than the sum of their population. By adopting a series of linearly polarized pulses resonant with the rotational states, the distribution of M = 0 rotational states is well rearranged. Though the number of pulses used is small, a relatively high orientation degree can be obtained. This scheme provides a promising approach to the achievement of a good orientation effect. Project supported by the National Basic Research Program of China (Grant No. 2013CB922200), the National Natural Science Foundation of China (Grant Nos. 11034003, 11474129, 11274141, and 11304116), the Research Fund for the Doctoral Program of Higher Education of China (Grant No. 20130061110021), and the Graduate Innovation Fund of Jilin University (Grant No. 2015091).

  8. Enzymatic cleavage and mass amplification strategy for small molecule detection using aptamer-based fluorescence polarization biosensor.

    PubMed

    Kang, Liping; Yang, Bin; Zhang, Xiaobing; Cui, Liang; Meng, Hongmin; Mei, Lei; Wu, Cuichen; Ren, Songlei; Tan, Weihong

    2015-06-16

    Fluorescence polarization (FP) assays incorporated with fluorophore-labeled aptamers have attracted great interest in recent years. However, detecting small molecules through the use of FP assays still remains a challenge because small-molecule binding only results in negligible changes in the molecular weight of the fluorophore-labeled aptamer. To address this issue, we herein report a fluorescence polarization (FP) aptamer assay that incorporates a novel signal amplification strategy for highly sensitive detection of small molecules. In the absence of adenosine, our model target, free FAM-labeled aptamer can be digested by nuclease, resulting in the release of FAM-labeled nucleotide segments from the dT-biotin/streptavidin complex with weak background signal. However, in the presence of target, the FAM-labeled aptamer-target complex protects the FAM-labeled aptamer from nuclease cleavage, allowing streptavidin to act as a molar mass amplifier. The resulting increase in molecular mass and FP intensity of the aptamer-target complex provides improved sensitivity for concentration measurement. The probe could detect adenosine from 0.5 μM to 1000 μM, with a detection limit of 500 nM, showing that the sensitivity of the probe is superior to aptamer-based FP approaches previously reported for adenosine. Importantly, FP could resist environmental interferences, making it useful for complex biological samples without any tedious sample pretreatments. Our results demonstrate that this dual-amplified, aptamer-based strategy can be used to design fluorescence polarization probes for rapid, sensitive, and selective measurement of small molecules in complicated biological environment. PMID:26002482

  9. Polarized fluorescence of polyatomic fragments produced through photodissociation of polyatomic molecules in the gas phase

    NASA Astrophysics Data System (ADS)

    Blokhin, A. P.; Gelin, M. F.; Kalosha, I. I.; Polubisok, S. A.; Tolkachev, V. A.

    1999-01-01

    A combined theoretical and experimental study is carried of the polarized emission of polyatomic products produced through photodissociation of polyatomic molecules. A general approach, based on the formalism of dissociation kernels and orientational correlation functions, is developed to predict anisotropy of the fluorescence of photoproducts. We consider the most general case of asymmetric top parent and product molecules. The rotational predissociation effect is taken into account. Various kinds of photoreactions are studied: those when fragments after dissociation are in the electronically excited states and those when fragments are in the ground electronic states so that additional laser pulse is necessary to excite their fluorescence. Particular attention is concentrated on those practically important extreme cases, when predissociation times and lifetimes of the electronically excited states of photoproducts are short or long as compared to the averaged period of free rotation. The steady state polarized fluorescence of radicals produced through dissociation of several disulfides into two identical radicals is measured. The results are interpreted in the framework of the free recoil model (FRM). In this model, photoproducts are assumed to experience no torque and fly apart freely, so that the only origin of the fragment rotation is rotation of the parent molecule. Predictions of the impulsive model (IM), in which fragments are supposed to suffer instantaneous torque due to the rupture of the chemical bonds of the parent molecule, are demonstrated to disagree strongly with our experimental data. This gives an additional confirmation of the validity of the FRM in describing dissociation of polyatomic molecules into polyatomic fragments. The FRM can therefore be invoked to estimate interrelation between the characteristic times, governing the processes of dissociation and emission, and the averaged period of free molecular rotation. Also, the FRM can be used

  10. Investigation of fingerprints for small polar molecules by using a tunable monochromatic THz source

    NASA Astrophysics Data System (ADS)

    Sun, Hongqian

    Over the past 20 years, considerable efforts have been dedicated to the generation and the application of electromagnetic waves in the Terahertz (THz) regime. Among all of the proposed applications, the THz spectroscopy is probably the most mature and promising one. According to the previous reports, the THz spectroscopy has been extensively applied into many analysis fields, including the investigation of vibrational modes for the crystalline solids, the characterization of electron transport in the condense matters and the identification of explosive materials at a standoff distance. More interestingly, since most gas phase chemicals exhibit unique transition peaks in the THz spectra, one could in principle achieve highly accurate molecular fingerprinting and chemical sensing as well. However, all of the practical THz spectroscopy applications were still greatly hampered by the lack of suitable sources and detectors. In this thesis, a unique approach to measure the THz spectrum is developed based on a novel tunable narrowband source. Unlike the previous THz systems, high power THz pulses were generated by the difference frequency generation processes between two collinearly propagated near infrared laser beams. To tune the output THz signal frequency, one can simply adjust one of the incident beam frequencies. Therefore, based on a convenient wavelength tuning scheme, the transmission spectra can be measured for a series of polar gases with either similar or distinct molecular structures. According to the measured spectra, it is found that the obtained transition frequencies, absorption intensities and molecular constants are all in good agreement with the theoretical results tabulated in the molecular spectroscopic databases, such as the HITRAN database. By further analyzing the transition frequencies, it is also discovered that one can confidently identify each polar molecule and differentiate between various isotopic variants based on their characteristic

  11. Magnetic moment enhancement and spin polarization switch of the manganese phthalocyanine molecule on an IrMn(100) surface

    SciTech Connect

    Sun, X.; Wang, B.; Pratt, A.; Yamauchi, Y.

    2014-07-21

    The geometric, electronic, and magnetic structures of a manganese phthalocyanine (MnPc) molecule on an antiferromagnetic IrMn(100) surface are studied by density functional theory calculations. Two kinds of orientation of the adsorbed MnPc molecule are predicted to coexist due to molecular self-assembly on the surface—a top-site geometry with the Mn–N bonds aligned along the 〈100〉 direction, and a hollow-site orientation in which the Mn–N bonds are parallel to the 〈110〉 direction. The MnPc molecule is antiferromagnetically coupled to the substrate at the top site with a slight reduction in the magnetic moment of the Mn atom of the MnPc molecule (Mn{sub mol}). In contrast, the magnetic moment of the Mn{sub mol} is enhanced to 4.28 μB at the hollow site, a value larger than that in the free MnPc molecule (3.51 μB). Molecular distortion induced by adsorption is revealed to be responsible for the enhancement of the magnetic moment. Furthermore, the spin polarization of the Mn{sub mol} atom at around the Fermi level is found to change from negative to positive through an elongation of the Mn–N bonds of the MnPc. We propose that a reversible switch of the low/high magnetic moment and negative/positive spin polarization might be realized through some mechanical engineering methods.

  12. Polarization effects on the electric properties of urea and thiourea molecules in solid phase

    SciTech Connect

    Santos, O. L.; Fonseca, T. L. Sabino, J. R.; Georg, H. C.; Castro, M. A.

    2015-12-21

    We present theoretical results for the dipole moment, linear polarizability, and first hyperpolarizability of the urea and thiourea molecules in solid phase. The in-crystal electric properties were determined by applying a supermolecule approach in combination with an iterative electrostatic scheme, in which the surrounding molecules are represented by point charges. It is found for both urea and thiourea molecules that the influence of the polarization effects is mild for the linear polarizability, but it is marked for the dipole moment and first hyperpolarizability. The replacement of oxygen atoms by sulfur atoms increases, in general, the electric responses. Our second-order Møller–Plesset perturbation theory based iterative scheme predicts for the in-crystal dipole moment of urea and thiourea the values of 7.54 and 9.19 D which are, respectively, increased by 61% and 58%, in comparison with the corresponding isolated values. The result for urea is in agreement with the available experimental result of 6.56 D. In addition, we present an estimate of macroscopic quantities considering explicit unit cells of urea and thiourea crystals including environment polarization effects. These supermolecule calculations take into account partially the exchange and dispersion effects. The results illustrate the role played by the electrostatic interactions on the static second-order nonlinear susceptibility of the urea crystal.

  13. Infrared-dressed entanglement of cold open-shell polar molecules for universal matchgate quantum computing

    NASA Astrophysics Data System (ADS)

    Herrera, Felipe; Cao, Yudong; Kais, Sabre; Whaley, K. Birgitta

    2014-07-01

    Implementing a scalable quantum information processor using polar molecules in optical lattices requires precise control over the long-range dipole-dipole interaction between molecules in selected lattice sites. We present here a scheme using trapped open-shell ^{2}\\Sigma polar molecules that allows dipolar exchange processes between nearest and next-nearest neighbors to be controlled in order to construct a generalized transverse Ising spin Hamiltonian with tunable XX, YY and XY couplings in the rotating frame of the driving lasers. The scheme requires a moderately strong bias magnetic field together with near-infrared light to provide local tuning of the qubit energy gap, and mid-infrared pulses to perform rotational state transfer via stimulated Raman adiabatic passage. No interaction between qubits occurs in the absence of the infrared driving. We analyze the fidelity of the resulting two-qubit matchgate, and demonstrate its robustness as a function of the driving parameters. We discuss a realistic application of the system for universal matchgate quantum computing in optical lattices.

  14. Magnetic surface states in high polarization materials

    NASA Astrophysics Data System (ADS)

    Wu, Ning; Dowben, Peter A.

    2011-10-01

    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.

  15. Nuclear magnetic resonance of laser-polarized noble gases in molecules, materials and organisms

    SciTech Connect

    Goodson, Boyd M.

    1999-12-01

    Conventional nuclear magnetic resonance (NMR) spectroscopy and magnetic resonance imaging (MRI) are fundamentally challenged by the insensitivity that stems from the ordinarily low spin polarization achievable in even the strongest NMR magnets. However, by transferring angular momentum from laser light to electronic and nuclear spins, optical pumping methods can increase the nuclear spin polarization of noble gases by several orders of magnitude, thereby greatly enhancing their NMR sensitivity. This dissertation is primarily concerned with the principles and practice of optically pumped nuclear magnetic resonance (OPNMR). The enormous sensitivity enhancement afforded by optical pumping noble gases can be exploited to permit a variety of novel NMR experiments across many disciplines. Many such experiments are reviewed, including the void-space imaging of organisms and materials, NMR and MRI of living tissues, probing structure and dynamics of molecules in solution and on surfaces, and zero-field NMR and MRI.

  16. Controlling magnetic Feshbach resonances in polar open-shell molecules with nonresonant light.

    PubMed

    Tomza, Michał; González-Férez, Rosario; Koch, Christiane P; Moszynski, Robert

    2014-03-21

    Magnetically tunable Feshbach resonances for polar paramagnetic ground-state diatomics are too narrow to allow for magnetoassociation starting from trapped, ultracold atoms. We show that nonresonant light can be used to engineer the Feshbach resonances in their position and width. For nonresonant field intensities of the order of 10(9) W/cm(2), we find the width to be increased by 3 orders of magnitude, reaching a few Gauss. This opens the way for producing ultracold molecules with sizable electric and magnetic dipole moments and thus for many-body quantum simulations with such particles. PMID:24702365

  17. Solids and Supersolids of Three-Body Interacting Polar Molecules on an Optical Lattice

    SciTech Connect

    Schmidt, Kai P.; Dorier, Julien; Laeuchli, Andreas M.

    2008-10-10

    We study the physics of cold polar molecules loaded into an optical lattice in the regime of strong three-body interactions, as put forward recently by Buechler et al.[Nature Phys. 3, 726 (2007)]. To this end, quantum Monte Carlo simulations, exact diagonalization, and a semiclassical approach are used to explore hard-core bosons on the 2D square lattice which interact solely by long-ranged three-body terms. The resulting phase diagram shows a sequence of solid and supersolid phases. Our findings are directly relevant for future experimental implementations and open a new route towards the discovery of a lattice supersolid phase in experiment.

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

    NASA Astrophysics Data System (ADS)

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

    2010-04-01

    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.

  19. Two-center minima in harmonic spectra from aligned polar molecules

    SciTech Connect

    Etches, Adam; Gaarde, Mette B.; Madsen, Lars Bojer

    2011-08-15

    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.

  20. Efficient conversion of ultracold Feshbach-resonance-related polar molecules into ultracold ground state (X 1Σ^+ v = 0, J = 0) molecules

    NASA Astrophysics Data System (ADS)

    Stwalley, W. C.

    2004-11-01

    It is proposed that bound states of ultracold heteronuclear alkali dimer molecules derived from Feshbach resonances can be efficiently converted into true ground state ultracold molecules (X 1Σ + v = 0, J = 0) by a stimulated Raman process via b 3{Pi} ˜ A 1Σ + mixed levels. This is illustrated and discussed for five of the ten polar heteronuclear alkali dimers: LiNa, NaK, NaRb, RbCs, and especially KRb.

  1. Low-Temperature Reactivity of C2n+1N(-) Anions with Polar Molecules.

    PubMed

    Joalland, Baptiste; Jamal-Eddine, Nour; Kłos, Jacek; Lique, François; Trolez, Yann; Guillemin, Jean-Claude; Carles, Sophie; Biennier, Ludovic

    2016-08-01

    Following the recent discovery of molecular anions in the interstellar medium, we report on the kinetics of proton transfer reactions between cyanopolyynide anions C2n+1N(-) (n = 0, 1, 2) and formic acid HCOOH. The results, obtained from room temperature down to 36 K by means of uniform supersonic flows, show a surprisingly weak temperature dependence of the CN(-) reaction rate, in contrast with longer chain anions. The CN(-) + HCOOH reaction is further studied theoretically via a reduced dimensional quantum model that highlights a tendency of the reaction probability to decrease with temperature, in agreement with experimental data but at the opposite of conventional long-range capture theories. In return, comparing HCOOH to HC3N as target molecules suggests that dipole-dipole interactions must play an active role in overcoming this limiting effect at low temperatures. This work provides new fundamental insights on prototypical reactions between polar anions and polar molecules along with critical data for astrochemical modeling. PMID:27399038

  2. Spin-polarization inversion at small organic molecule/Fe{sub 4}N interfaces: A first-principles study

    SciTech Connect

    Zhang, Qian; Mi, Wenbo

    2015-09-21

    We report the first-principles calculations on the electronic structure and simulation of the spin-polarized scan tunneling microscopy graphic of the small organic molecules (benzene, thiophene, and cyclopentadienyl)/Fe{sub 4}N interfaces. It is found that the plane of benzene and thiophene keeps parallel to Fe{sub 4}N surface, while that of cyclopentadienyl does not. For all the systems, the organic molecules bind strongly with Fe{sub 4}N. Due to the hybridization between molecule p{sub z} orbitals and d orbitals of Fe, i.e., Zener interaction, all the three systems realize the spin-polarization inversion, whereas the spatial spin-polarization inversion distribution shows different intensities influenced by the competition between the spin polarization of C p{sub z} and Fe d states.

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

    SciTech Connect

    Guerout, R.; Aymar, M.; Dulieu, O.

    2010-10-15

    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.

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

    SciTech Connect

    Odzak, S.; Milosevic, D. B.

    2010-08-15

    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.

  5. High Performance Circularly Polarized Microstrip Antenna

    NASA Technical Reports Server (NTRS)

    Bondyopadhyay, Probir K. (Inventor)

    1997-01-01

    A microstrip antenna for radiating circularly polarized electromagnetic waves comprising a cluster array of at least four microstrip radiator elements, each of which is provided with dual orthogonal coplanar feeds in phase quadrature relation achieved by connection to an asymmetric T-junction power divider impedance notched at resonance. The dual fed circularly polarized reference element is positioned with its axis at a 45 deg angle with respect to the unit cell axis. The other three dual fed elements in the unit cell are positioned and fed with a coplanar feed structure with sequential rotation and phasing to enhance the axial ratio and impedance matching performance over a wide bandwidth. The centers of the radiator elements are disposed at the corners of a square with each side of a length d in the range of 0.7 to 0.9 times the free space wavelength of the antenna radiation and the radiator elements reside in a square unit cell area of sides equal to 2d and thereby permit the array to be used as a phased array antenna for electronic scanning and is realizable in a high temperature superconducting thin film material for high efficiency.

  6. Multielectron signatures in the polarization of high-order harmonic radiation

    SciTech Connect

    Zhao Zengxiu; Yuan Jianmin; Brabec, Thomas

    2007-09-15

    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.

  7. Detecting high-density ultracold molecules using atom-molecule collision

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    Utilizing single-photon photoassociation, we have achieved ultracold rubidium molecules with a high number density that provides a new efficient approach toward molecular quantum degeneracy. A new detection mechanism for ultracold molecules utilizing inelastic atom-molecule collision is demonstrated. The resonant coupling effect on the formation of the X1Σ+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.

  8. Integrated polarizers based on tapered highly birefringent photonic crystal fibers.

    PubMed

    Romagnoli, Priscila; Biazoli, Claudecir R; Franco, Marcos A R; Cordeiro, Cristiano M B; de Matos, Christiano J S

    2014-07-28

    This paper proposes and demonstrates the creation of sections with a high polarization dependent loss (PDL) in a commercial highly birefringent (polarization maintaining) photonic crystal fiber (PCF), via tapering with pressure applied to the holes. The tapers had a 1-cm-long uniform section with a 66% scale reduction, in which the original microstructure aspect ratio was kept by the pressure application. The resulting waveguides show polarizing action across the entire tested wavelength range, 1510-1600 nm, with a peak PDL of 35.3 dB/cm (c.f. ~1 dB/cm for a typical commercial polarizing fiber). The resulting structure, as well as its production, is extremely simple, and enable a small section with a high PDL to be obtained in a polarization maintaining PCF, meaning that the polarization axes in the polarizing and polarization maintaining sections are automatically aligned. PMID:25089397

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

    SciTech Connect

    Che, Yanke; Yang, Xiaomei; Balakrishnan, Kaushik; Zuo, Jianmin; Zang, Ling

    2009-09-15

    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.

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

    PubMed Central

    2011-01-01

    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 σ- and π-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

  11. Spin-labeled gel for the production of radical-free dynamic nuclear polarization enhanced molecules for NMR spectroscopy and imaging

    NASA Astrophysics Data System (ADS)

    McCarney, Evan R.; Han, Songi

    2008-02-01

    Dynamic nuclear polarization (DNP) has recently received much attention as a viable approach to enhance the sensitivity of nuclear magnetic resonance (NMR) spectroscopy and the contrast of magnetic resonance imaging (MRI), where the significantly higher electron spin polarization of stable radicals is transferred to nuclear spins. In order to apply DNP-enhanced NMR and MRI signal to biological and in vivo systems, it is crucial to obtain highly polarized solution samples at ambient temperatures. As stable radicals are employed as the source for the DNP polarization transfer, it is also crucial that the highly polarized sample lacks residual radical concentration because the polarized molecules will be introduced to a biological system that will be sensitive to the presence of radicals. We developed an agarose-based porous media that is covalently spin-labeled with stable radicals. The loading of solvent accessible radical is sufficiently high and their mobility approximates that in solution, which ensures high efficiency for Overhauser mechanism induced DNP without physically releasing any measurable radical into the solution. Under ambient conditions at 0.35 T magnetic field, we measure the DNP enhancement efficiency of 1H signal of stagnant and continuously flowing water utilizing immobilized stable nitroxide radicals that contain two or three ESR hyperfine splitting lines and compare them to the performance of freely dissolved radicals.

  12. The effect of a permanent dipole moment on the polar molecule cavity quantum electrodynamics

    NASA Astrophysics Data System (ADS)

    Jing-Yun, Zhao; Li-Guo, Qin; Xun-Ming, Cai; Qiang, Lin; Zhong-Yang, Wang

    2016-04-01

    A dressed-state perturbation theory beyond the rotating wave approximation (RWA) is presented to investigate the interaction between a two-level electronic transition of polar molecules and a quantized cavity field. Analytical expressions can be explicitly derived for both the ground- and excited-state-energy spectrums and wave functions of the system, where the contribution of permanent dipole moments (PDM) and the counter-rotating wave term (CRT) can be shown separately. The validity of these explicit results is discussed by comparison with the direct numerical simulation. Compared to the CRT coupling, PDM results in the coupling of more dressed states and the energy shift is proportional to the square of the normalized permanent dipole difference, and a greater Bloch–Siegert shift can be produced in the giant dipole molecule cavity QED. In addition, our method can also be extended to the solution of the two-level atom Rabi model Hamiltonian beyond the RWA. Project supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB01010200), the Hundred Talents Program of the Chinese Academy of Sciences (Grant No. Y321311401), the National Natural Science Foundation of China (Grant Nos. 61475139, 11347147, and 11247014), the National Basics Research Program of China (Grant No. 2013CB329501), and the Zhejiang Provincial Natural Science Foundation (Grant No. LQ13A040006).

  13. Search for Asymmetric Interactions between Chiral Molecules and Spin-Polarized Electrons

    NASA Astrophysics Data System (ADS)

    Dreiling, Joan; Litaker, Eric; Gay, Timothy

    2013-05-01

    We present our preliminary asymmetry results for the transmission of longitudinally spin-polarized electrons through a vapor of chirally-pure bromocamphor (C10H15BrO) molecules. We define the asymmetry for transmission as A = [(I ↑-I ↓) /(I ↑ + I ↓) ]R- [(I ↑-I ↓) /(I ↑ + I ↓) ]L, where I ↑ (I ↓) is the transmitted current measured for spin-up (spin-down) electrons and the ``L'' and ``R'' subscripts correspond to the left- and right-handed chirality of the molecules. At present, we have measured A at 1.5 eV electron scattering energy to be 5.4(2.5)*10-5 when the transmitted, magnetically collimated electron beam is attenuated to 10% of its initial value, corresponding to a pressure of a few millitorr in a cell of length 2.54 cm. This should be compared with the measurements of Mayer et al., where they report an asymmetry (by our definition) of about 3.4(0.2)*10-4 for the same incident energy and electron beam attenuation. We discuss possible reasons for this discrepancy.

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

    PubMed Central

    Alsharaeh, Edreese H.

    2011-01-01

    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). PMID:22272121

  15. Intracluster ion molecule reactions following the generation of Mg+ within polar clusters.

    PubMed

    Alsharaeh, Edreese H

    2011-01-01

    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 CH(3) group. In addition, the magic numbers in the time of flight (TOF) mass spectra of the Mg(+)X(n) clusters (X = H(2)O, CH(3)OH, CH(3)OCH(3) and CH(3)CN) have been investigated. Finally, the role of ground electronic magnesium ion Mg(+)((2)S(1/2)), and excited electronic magnesium ion Mg(+)((2)P(1/2)) in the dehydrogenation reaction were investigated using Ion Mobility Mass spectrometry. The results offer direct evidence confirming the absence of the electronically excited, Mg(+)((2)P(1/2)). PMID:22272121

  16. Polarization Splay as the Origin of Modulation in the B1 and B7 Smectic Phases of Bent-Core Molecules

    SciTech Connect

    Coleman,D.; Jones, C.; Nakata, M.; Clark, N.; Walba, D.; Weissflog, W.; Fodor-Csorba, K.; Watanabe, J.; Novotna, V.; Hamplova, V.

    2008-01-01

    We report a generalized scenario for the formation of modulated smectic phases of bent-core molecules based on locally ferroelectric layering and spontaneous splay of the polarization. Twelve phases are proposed, distinguished by neighboring splay stripes with either syn- or antiorder of the polarization and undulation slope, in addition to layer continuity versus layer discontinuity at the intervening defects. We outline the experimental techniques necessary to differentiate among the phases and interpret previous results in the present context, using high resolution x-ray scattering diffraction and block and undulation models of the layer organization to distinguish among the three 2D lattice types which emerge.

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

    SciTech Connect

    Kotochigova, Svetlana; DeMille, David

    2010-12-15

    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.

  18. High energy polarized beams from hyperon decays

    SciTech Connect

    Underwood, D.G.

    1986-01-01

    The use of various ways to utilize lambda decays to obtain polarized beams of protons and antiprotons is emphasized. Examples described are the Fermilab polarized beam, now under construction, and the use of similar techniques at other energies. Beam transport, spin precession and reversal systems, and polarimeters are also discussed. 8 refs., 4 figs.

  19. High Spin Polarization at Ferromagnetic Metal-Organic Interfaces: A Generic Property.

    PubMed

    Djeghloul, Fatima; Gruber, Manuel; Urbain, Etienne; Xenioti, Dimitra; Joly, Loic; Boukari, Samy; Arabski, Jacek; Bulou, Hervé; Scheurer, Fabrice; Bertran, François; Le Fèvre, Patrick; Taleb-Ibrahimi, Amina; Wulfhekel, Wulf; Garreau, Guillaume; Hajjar-Garreau, Samar; Wetzel, Patrick; Alouani, Mebarek; Beaurepaire, Eric; Bowen, Martin; Weber, Wolfgang

    2016-07-01

    A high spin polarization of states around the Fermi level, EF, at room temperature has been measured in the past at the interface between a few molecular candidates and the ferromagnetic metal Co. Is this promising property for spintronics limited to these candidates? Previous reports suggested that certain conditions, such as strong ferromagnetism, i.e., a fully occupied spin-up d band of the ferromagnet, or the presence of π bonds on the molecule, i.e., molecular conjugation, needed to be met. What rules govern the presence of this property? We have performed spin-resolved photoemission spectroscopy measurements on a variety of such interfaces. We find that this property is robust against changes to the molecule and ferromagnetic metal's electronic properties, including the aforementioned conditions. This affirms the generality of highly spin-polarized states at the interface between a ferromagnetic metal and a molecule and augurs bright prospects toward integrating these interfaces within organic spintronic devices. PMID:27266579

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

    ERIC Educational Resources Information Center

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

    2000-01-01

    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)

  1. Fluorescence Polarization Screening Assays for Small Molecule Allosteric Modulators of ABL Kinase Function

    PubMed Central

    Grover, Prerna; Shi, Haibin; Baumgartner, Matthew; Camacho, Carlos J.; Smithgall, Thomas E.

    2015-01-01

    The ABL protein-tyrosine kinase regulates intracellular signaling pathways controlling diverse cellular processes and contributes to several forms of cancer. The kinase activity of ABL is repressed by intramolecular interactions involving its regulatory Ncap, SH3 and SH2 domains. Small molecules that allosterically regulate ABL kinase activity through its non-catalytic domains may represent selective probes of ABL function. Here we report a screening assay for chemical modulators of ABL kinase activity that target the regulatory interaction of the SH3 domain with the SH2-kinase linker. This fluorescence polarization (FP) assay is based on a purified recombinant ABL protein consisting of the N-cap, SH3 and SH2 domains plus the SH2-kinase linker (N32L protein) and a short fluorescein-labeled probe peptide that binds to the SH3 domain. In assay development experiments, we found that the probe peptide binds to the recombinant ABL N32L protein in vitro, producing a robust FP signal that can be competed with an excess of unlabeled peptide. The FP signal is not observed with control N32L proteins bearing either an inactivating mutation in the SH3 domain or enhanced SH3:linker interaction. A pilot screen of 1200 FDA-approved drugs identified four compounds that specifically reduced the FP signal by at least three standard deviations from the untreated controls. Secondary assays showed that one of these hit compounds, the antithrombotic drug dipyridamole, enhances ABL kinase activity in vitro to a greater extent than the previously described ABL agonist, DPH. Docking studies predicted that this compound binds to a pocket formed at the interface of the SH3 domain and the linker, suggesting that it activates ABL by disrupting this regulatory interaction. These results show that screening assays based on the non-catalytic domains of ABL can identify allosteric small molecule regulators of kinase function, providing a new approach to selective drug discovery for this important

  2. Theoretically predicted Fox-7 based new high energy density molecules

    NASA Astrophysics Data System (ADS)

    Ghanta, Susanta

    2016-08-01

    Computational investigation of CHNO based high energy density molecules (HEDM) are designed with FOX-7 (1, 1-dinitro 2, 2-diamino ethylene) skeleton. We report structures, stability and detonation properties of these new molecules. A systematic analysis is presented for the crystal density, activation energy for nitro to nitrite isomerisation and the C-NO2 bond dissociation energy of these molecules. The Atoms in molecules (AIM) calculations have been performed to interpret the intra-molecular weak H-bonding interactions and the stability of C-NO2 bonds. The structure optimization, frequency and bond dissociation energy calculations have been performed at B3LYP level of theory by using G03 quantum chemistry package. Some of the designed molecules are found to be more promising HEDM than FOX-7 molecule, and are proposed to be candidate for synthetic purpose.

  3. High circular polarization in electroluminescence from MoSe2

    NASA Astrophysics Data System (ADS)

    Onga, Masaru; Zhang, Yijin; Suzuki, Ryuji; Iwasa, Yoshihiro

    2016-02-01

    The coupling between the valley degree of freedom and the optical helicity is one of the unique phenomena in transition metal dichalcogenides. The significant valley polarization evaluated from circularly polarized photoluminescence (PL) has been reported in many transition metal dichalcogenides, except in MoSe2. This compound is an anomalous material showing ultra-fast relaxation of the valley polarized states, which causes negligible polarization in the PL. Meanwhile, circularly polarized electroluminescence (EL) has been recently reported in a WSe2 light-emitting transistor, providing another method for using the valley degree of freedom. Here, we report the EL properties of MoSe2, demonstrating electrical switching of the optical helicity. Importantly, we observed high circular polarization reaching 66%. The results imply that the dominant mechanism of circularly polarized EL is robust against intervalley scattering, in marked contrast to the PL.

  4. High-Resolution South Polar Cap Mosaics

    NASA Technical Reports Server (NTRS)

    2000-01-01

    The layered terrains of the polar regions of Mars are among the most exotic planetary landscapes in our Solar System. The layers exposed in the south polar residual cap, vividly shown in the top view, are thought to contain detailed records of Mars' climate history over the last 100 million years or so. The materials that comprise the south polar layers may include frozen carbon dioxide, water ice, and fine dust. The bottom picture shows complex erosional patterns that have developed on the south polar cap, perhaps by a combination of sublimation, wind erosion, and ground-collapse. Because the south polar terrains are so strange and new to human eyes, no one (yet) has entirely adequate explanations as to what is being seen.

    These images were acquired by the Mars Orbiter Camera aboard the Mars Global Surveyor spacecraft during the southern spring season in October 1999. Each of these two pictures is a mosaic of many individual MOC images acquired at about 12 m/pixel scale that completely cover the highest latitude (87oS) visible to MOC on each orbital pass over the polar region. Both mosaics cover areas of about 10 x 4 kilometers (6.2 x 2.5 miles) near 87oS, 10oW in the central region of the permanent--or residual--south polar cap. They show features at the scale of a small house. Sunlight illuminates each scene from the left.'Gaps' at the upper and lower right of the second mosaic, above, are areas that were not covered by MOC in October 1999.

  5. Completely monolithic linearly polarized high-power fiber laser oscillator

    NASA Astrophysics Data System (ADS)

    Belke, Steffen; Becker, Frank; Neumann, Benjamin; Ruppik, Stefan; Hefter, Ulrich

    2014-03-01

    We have demonstrated a linearly polarized cw all-in-fiber oscillator providing 1 kW of output power and a polarization extinction ratio (PER) of up to 21.7 dB. The design of the laser oscillator is simple and consists of an Ytterbium-doped polarization maintaining large mode area (PLMA) fiber and suitable fiber Bragg gratings (FBG) in matching PLMA fibers. The oscillator has nearly diffraction-limited beam quality (M² < 1.2). Pump power is delivered via a high power 6+1:1 pump coupler. The slope efficiency of the laser is 75 %. The electro/optical efficiency of the complete laser system is ~30 % and hence in the range of Rofin's cw non-polarized fiber lasers. Choosing an adequate bending diameter for the Yb-doped PLMA fiber, one polarization mode as well as higher order modes are sufficiently supressed1. Resulting in a compact and robust linearly polarized high power single mode laser without external polarizing components. Linearly polarized lasers are well established for one dimensional cutting or welding applications. Using beam shaping optics radially polarized laser light can be generated to be independent from the angle of incident to the processing surface. Furthermore, high power linearly polarized laser light is fundamental for nonlinear frequency conversion of nonlinear materials.

  6. Spectroscopy, reaction, and photodissociation in highly vibrationally excited molecules

    SciTech Connect

    Not Available

    1991-01-01

    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.

  7. Topological phases in atoms and molecules in spin-polarized electron scattering

    NASA Astrophysics Data System (ADS)

    Williams, James; Pravica, Luka; Samarin, Sergey; Kathi, Sudarshan; Guagliardo, Paul; CentreAtomic, Molecular; Surface Physics Team

    2013-05-01

    Observations of spin-polarized electron impact excitation of zinc atoms, ionization of helium atoms and dissociative excitation of molecules indicate a topological phase. The parallel transport of the spin vector gives rise to an effective `monopole' magnetic field and an apparent spin-orbit interaction. In excitation, the Stokes parameters of radiated photons show alignment and orientation. Excitation of a superposition of 2s and 2p states on atomic hydrogen in an external electric field show beats in Lyman alpha radiation as predicted for a circular vortex. Ionization of helium atoms show minima in (e,2e) angular and energy differential cross sections associated with a linear vortex (Macek, Feagin). Exchange dissociative excitation of methane shows radiated photons from a Jahn-Teller ``avoided crossing'' of potential energy curves (Mead and Truhlar). The observations are consistent with fundamental principles that a gauge-invariant quantity is potentially a physical observable and the topology of a ring indicates a magnetic-flux line enclosed by the ring is equivalent to a vortex line. Funding was received from the Australian Research Council and The University of Western Australia.

  8. Single-molecule imaging at high hydrostatic pressure

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

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

    SciTech Connect

    Hansen, Jonas L.; Holmegaard, Lotte; Kalhoej, Line; Kragh, Sofie Louise; Stapelfeldt, Henrik; Filsinger, Frank; Meijer, Gerard; Kuepper, Jochen; Dimitrovski, Darko; Abu-samha, Mahmoud; Martiny, Christian Per Juul; Madsen, Lars Bojer

    2011-02-15

    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.

  10. Single DNA Molecule Patterning for High-Throughput Epigenetic Mapping

    PubMed Central

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

    2013-01-01

    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. PMID:21981444

  11. High resolution electron crystallography of protein molecules

    SciTech Connect

    Glaeser, R.M. |; Downing, K.H.

    1993-06-01

    Electron diffraction data and high resolution images can now be used to obtain accurate, three-dimensional density maps of biological macromolecules. These density maps can be interpreted by building an atomic-resolution model of the structure into the experimental density. The Cowley-Moodie formalism of dynamical diffraction theory has been used to validate the use of kinematic diffraction theory, strictly the weak phase object approximation, in producing such 3-D density maps. Further improvements in the preparation of very flat specimens and in the retention of diffraction to a resolution of 0.2 nm or better could result in electron crystallography becoming as important a technique as x-ray crystallography currently is for the field of structural molecular biology.

  12. Organic molecules in the polar ice: from chemical analysis to environmental proxies

    NASA Astrophysics Data System (ADS)

    Barbante, Carlo; Zennaro, Piero; Giorio, Chiara; Kehrwald, Natalie; Benton, Alisa K.; Wolff, Eric W.; Kalberer, Markus; Kirchgeorg, Torben; Zangrando, Roberta; Barbaro, Elena; Gambaro, Andrea

    2015-04-01

    The molecular and isotopic compositions of organic matter buried in ice contains information that helps reconstruct past environmental conditions, evaluate histories of climate change, and assess impacts of humans on ecosystems. In recent years novel analytical techniques were developed to quantify molecular compounds in ice cores. As an example, biomass burning markers, including monosaccharide anhydrides, lightweight carboxylic acids, lignin and resin pyrolysis products, black carbon, and charcoal records help in reconstructing past fire activity across seasonal to millennial time scales. Terrestrial biomarkers, such as plant waxes (e.g. long-chain n-alkanes) are also a promising paleo vegetation proxy in ice core studies. Polycyclic aromatic hydrocarbons are ubiquitous pollutants recently detected in ice cores. These hydrocarbons primarily originate from incomplete combustion of organic matter and fossil fuels (e.g. diesel engines, domestic heating, industrial combustion) and therefore can be tracers of past combustion activities. In order to be suitable for paloeclimate purposes, organic molecular markers detected in ice cores should include the following important features. Markers have to be stable under oxidizing atmospheric conditions, and ideally should not react with hydroxyl radicals, during their transport to polar regions. Organic markers must be released in large amounts in order to be detected at remote distances from the sources. Proxies must be specific, in order to differentiate them from other markers with multiple sources. The extraction of glaciochemical information from ice cores is challenging due to the low concentrations of some impurities, thereby demanding rigorous control of external contamination sources and sensitive analytical techniques. Here, we review the analysis and use of organic molecules in ice as proxies of important environmental and climatic processes.

  13. Polarized neutron reflectometry in high magnetic fields

    SciTech Connect

    Fritzsche, H.

    2005-11-15

    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.

  14. M-CARS and EFISHG study of the influence of a static electric field on a non-polar molecule

    NASA Astrophysics Data System (ADS)

    Capitaine, E.; Louot, C.; Ould-Moussa, N.; Lefort, C.; Kaneyasu, J. F.; Kano, H.; Pagnoux, D.; Couderc, V.; Leproux, P.

    2016-03-01

    The influence of a static electric field on a non-polar molecule has been studied by means of multiplex coherent anti-Stokes Raman scattering (M-CARS). A parallel measurement of electric field induced second harmonic generation (EFISHG) has also been led. Both techniques suggest a reorientation of the molecule due to the presence of an electric field. This phenomenon can be used to increase the chemical selectivity and the signal to non-resonant background ratio, namely, the sensitivity of the M-CARS spectroscopy.

  15. High Precision Assembly Line Synthesis for Molecules with Tailored Shapes

    PubMed Central

    Burns, Matthew; Essafi, Stephanie; Bame, Jessica R.; Bull, Stephanie P.; Webster, Matthew P.; Balieu, Sebastien; Dale, James W.; Butts, Craig P.; Harvey, Jeremy N.; Aggarwal, Varinder K.

    2014-01-01

    Molecular assembly lines, where molecules undergo iterative processes involving chain elongation and functional group manipulation are hallmarks of many processes found in Nature. We have sought to emulate Nature in the development of our own molecular assembly line through iterative homologations of boronic esters. Here we report a reagent (α-lithioethyl triispopropylbenzoate) which inserts into carbon-boron bonds with exceptionally high fidelity and stereocontrol. Through repeated iteration we have converted a simple boronic ester into a complex molecule (a carbon chain with ten contiguous methyl groups) with remarkably high precision over its length, its stereochemistry and therefore its shape. Different stereoisomers were targeted and it was found that they adopted different shapes (helical/linear) according to their stereochemistry. This work should now enable scientists to rationally design and create molecules with predictable shape, which could have an impact in all areas of molecular sciences where bespoke molecules are required. PMID:25209797

  16. Theory of coherent polarization anisotropy in time-resolved two-photon ionization of isolated molecules. Effects of Coriolis couplings

    NASA Astrophysics Data System (ADS)

    Sato, S.; Nomura, Y.; Fujimura, Y.

    1987-09-01

    Effects of vibration-rotation (Coriolis) couplings on the coherent polarization anisotropy are theoretically studied in a time-resolved two-photon ionization of a symmetric top molecule. This polarization anisotropy originates from a coherent excitation of the resonant rovibronic molecular eigenstates (rovibronic coherence) whose zeroth order states are mixed through the Coriolis coupling. Expressions for the time-dependent degree of polarization after the coherent excitation of the rovibronic states produced by the Coriolis coupling are derived as a function of the delay time in the pump-probe two-photon ionization. Model calculations of the time-dependent degree of polarization as well as the probabilities of the two-photon ionization are performed to demonstrate the Coriolis coupling effects in the low excess energy regions of the resonant intermediate state. It is shown that oscillatory behaviors in the time-dependent degree of polarization should be observed as a result of the creation of the rovibronic coherence. It is demonstrated that oscillations of the degree of polarization involve both contribution of the purely rotational J-coherence and that of the rovibronic coherence in the resonant manifold when the rotational branches are coherently excited and the characteristic rotation-vibration interaction energy is larger than a typical free rotational energy under jet-cooled condition.

  17. Probing non polar interstellar molecules through their protonated form: Detection of protonated cyanogen (NCCNH+)★

    PubMed Central

    Agúndez, M.; Cernicharo, J.; de Vicente, P.; Marcelino, N.; Roueff, E.; Fuente, A.; Gerin, M.; Guélin, M.; Albo, C.; Barcia, A.; Barbas, L.; Bolaño, R.; Colomer, F.; Diez, M. C.; Gallego, J. D.; Gómez-González, J.; López-Fernández, I.; López-Fernández, J. A.; López-Pérez, J. A.; Malo, I.; Serna, J. M.; Tercero, F.

    2015-01-01

    Cyanogen (NCCN) is the simplest member of the series of dicyanopolyynes. It has been hypothesized that this family of molecules can be important constituents of interstellar and circumstellar media, although the lack of a permanent electric dipole moment prevents its detection through radioastronomical techniques. Here we present the first solid evidence of the presence of cyanogen in interstellar clouds through the detection of its protonated form toward the cold dark clouds TMC-1 and L483. Protonated cyanogen (NCCNH+) has been identified through the J = 5 – 4 and J = 10 – 9 rotational transitions using the 40m radiotelescope of Yebes and the IRAM 30m telescope. We derive beam averaged column densities for NCCNH+ of (8.6 ± 4.4) × 1010 cm−2 in TMC-1 and (3.9 ± 1.8) × 1010 cm−2 in L483, which translate to fairly low fractional abundances relative to H2, in the range (1-10) × 10−12. The chemistry of protonated molecules in dark clouds is discussed, and it is found that, in general terms, the abundance ratio between the protonated and non protonated forms of a molecule increases with increasing proton affinity. Our chemical model predicts an abundance ratio NCCNH+/NCCN of ~ 10−4, which implies that the abundance of cyanogen in dark clouds could be as high as (1-10) × 10−8 relative to H2, i.e., comparable to that of other abundant nitriles such as HCN, HNC, and HC3N. PMID:26543239

  18. Polarization of high harmonic generated spectra in H+2ion

    NASA Astrophysics Data System (ADS)

    Castiglia, Giuseppe; Corso, Pietro Paolo; Daniele, Rosalba; Fiordilino, Emilio; Morales, Francesca

    2013-10-01

    We study the polarization of the harmonics generated by a homonuclear diatomic molecule in the presence of an intense, linearly polarized laser field. The polarization parameters of the emitted radiation are investigated as a function of the angle ? between the laser electric field and the molecular axis. The calculations are carried out by assuming a single active electron model with fixed nuclei; a two-dimensional model of the system is used. We find a different dependence of the parameters of the harmonics vs ? in the first or second half of the emitted spectrum. In particular, the differences are accentuated for ?, while for higher angles, until the perpendicular orientation, almost all the harmonics present similar characteristics.

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

    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.

  20. Spectroscopy, reaction, and photodissociation of highly vibrationally excited molecules

    SciTech Connect

    Crim, F.F.

    1990-01-01

    This research is designed to determine the nature of highly vibrationally excited molecules, probe unimolecular reactions at the level of individual quantum states, and study the dynamics of electronic photodissociation from highly vibrationally excited states. In our experiments, pulsed laser excitation of a vibrational overtone transition prepares a highly vibrationally excited molecule and time-resolved spectroscopic detection of products monitors their subsequent decomposition. We have used this scheme to follow unimolecular reactions of large and small molecules in both room temperature gases and supersonic expansions and to investigate the role that vibrational excitation plays in electronic photodissociation dynamics. Most recently we have used the localized nature of the highly vibrationally excited states we create to selectively break bonds in photodissociation and biomolecular reactions.

  1. An electron spin polarization study of the interaction of photoexcited triplet molecules with mono- and polynitroxyl stable free radicals

    SciTech Connect

    Turro, N.J.; Khudyakov, I.V.; Bossmann, S.H. ); Dwyer, D.W. )

    1993-02-11

    Time-resolved electron spin resonance (TR ESR) has been used to investigate the chemically induced dynamic electron polarization (CIDEP) generated by the interaction of stable free radicals with the triplet states of benzophenone, benzil, and 2-acetylnaphthalene. The stable radicals were mono-, di-, tri-, and tetranitroxyl free radicals possessing the 2,2,6,6-tetramethylpiperidine-N-oxyl moiety. All of the stable radical systems investigated were found to be emissively polarized by interaction with the triplet states, and the phase of polarization was independent of the sign of zero-field splitting (D) of the interacting triple molecule. Possible and likely mechanisms of polarization transfer (creation) resulting from the interaction of photoexcited triplet molecules with nitroxyls in the strong electron exchange are discussed. The emissive CIDEP of nitroxyls observed in the interactions with triplet benzil, which has D > 0, provides strong support for the operation of the radical-triplet pair mechanism. Within the time scale of TR ESR experiments ([approximately]10[sup [minus]7]--10[sup [minus]6] s) no significant variation in the shape of the CIDEP spectra of the nitroxyls was observed, either in viscous media or in micelles. It is concluded that intramolecular spin exchange (or conformational change) of polynitroyls occurs much faster than the time resolution of the experiment. 24 refs., 6 figs., 1 tab.

  2. Circularly polarized attosecond pulses from molecular high-order harmonic generation by ultrashort intense bichromatic circularly and linearly polarized laser pulses

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Bandrauk, André D.

    2012-04-01

    We describe the generation of high-order elliptically and circularly polarized harmonic spectra in an aligned H+2 molecule ion by a combination of two-colour ultrashort intense laser fields from numerical solutions of the corresponding time-dependent Schrödinger equation (TDSE). In intense bichromatic circularly and linearly or circularly polarized laser pulses with intensity I0 and angular frequencies ω0 and 2ω0, it is found that maximum molecular high-order harmonic generation (MHOHG) energies are functions of the molecular internuclear distance. Based on a classical model of laser-induced electron collisions with neighbouring ions, the optimal values of the pulse relative carrier envelope phase phi, the molecular internuclear distance R and the angle thetav of molecular alignment to the laser polarization axis are obtained for efficiently producing MHOHG spectra with the maximum harmonic energy Ip + 13.5Up, where Ip is the ionization potential of the molecule and Up = I0/4meω20 is the ponderomotive energy of the continuum electron at intensity I0 and frequency ω0 of the laser pulse. The results have been confirmed from corresponding TDSE nonperturbative numerical simulations. The polarization property of the generated harmonics is also presented. The mechanism of MHOHG is further characterized with a Gabor time frequency analysis. It is confirmed that a single collision trajectory of the continuum electron with neighbouring ions dominates in the MHOHG processes. The high efficiency of the proposed MHOHG scheme provides a possible source for production of elliptically and/or circularly polarized attosecond extreme ultraviolet pulses. Circularly polarized attosecond pulses can also be generated by using intense ultrashort circularly polarized laser pulses in combination with static electric fields of comparable intensity for H+2 at equilibrium. A time frequency analysis also confirms the role of single recollisions as the dominant mechanism of the generation

  3. Orientation and Rotational Motions of Single Molecules by Polarized Total Internal Reflection Fluorescence Microscopy (polTIRFM)

    PubMed Central

    Beausang, John F.; Sun, Yujie; Quinlan, Margot E.; Forkey, Joseph N.; Goldman, Yale E.

    2013-01-01

    In this article, we describe methods to detect the spatial orientation and rotational dynamics of single molecules using polarized total internal reflection fluorescence microscopy (polTIRFM). polTIRFM determines the three-dimensional angular orientation and the extent of wobble of a fluorescent probe bound to the macromolecule of interest. We discuss single-molecule versus ensemble measurements, as well as single-molecule techniques for orientation and rotation, and fluorescent probes for orientation studies. Using calmodulin (CaM) as an example of a target protein, we describe a method for labeling CaM with bifunctional rhodamine (BR). We also describe the physical principles and experimental setup of polTIRFM. We conclude with a brief introduction to assays using polTIRFM to assess the interaction of actin and myosin. PMID:22550303

  4. Role of interspecies interactions in the preparation of a low-entropy gas of polar molecules in a lattice

    NASA Astrophysics Data System (ADS)

    Safavi-Naini, A.; Wall, M. L.; Rey, A. M.

    2015-12-01

    The preparation of a quantum degenerate gas of heteronuclear molecules has been an outstanding challenge. We use path-integral quantum Monte Carlo simulations to understand the role of interactions and finite temperature effects in the protocol currently employed to adiabatically prepare a low-entropy gas of polar molecules in a lattice starting from an ultracold Bose-Fermi mixture. We find that interspecies interactions affect the final temperature of the mixture after the adiabatic loading procedure and detrimentally limit the molecular peak filling. Our conclusions are in agreement with recent experimental measurements [Moses et al., Science 350, 659 (2015), 10.1126/science.aac6400] and therefore are of immediate relevance for the myriad experiments that aim to form molecules from dual-species atomic gases.

  5. Luminescent systems based on the isolation of conjugated PI systems and edge charge compensation with polar molecules on a charged nanostructured surface

    DOEpatents

    Ivanov, Ilia N.; Puretzky, Alexander A.; Zhao, Bin; Geohegan, David B.; Styers-Barnett, David J.; Hu, Hui

    2014-07-15

    A photoluminescent or electroluminescent system and method of making a non-luminescent nanostructured material into such a luminescent system is presented. The method of preparing the luminescent system, generally, comprises the steps of modifying the surface of a nanostructured material to create isolated regions to act as luminescent centers and to create a charge imbalance on the surface; applying more than one polar molecule to the charged surface of the nanostructured material; and orienting the polar molecules to compensate for the charge imbalance on the surface of the nanostructured material. The compensation of the surface charge imbalance by the polar molecules allows the isolated regions to exhibit luminescence.

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

    SciTech Connect

    Sukiasyan, Suren; Ivanov, Misha Yu.; Patchkovskii, Serguei; Smirnova, Olga; Brabec, Thomas

    2010-10-15

    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.

  7. Next generation techniques in the high resolution spectroscopy of biologically relevant molecules.

    PubMed

    Neill, Justin L; Douglass, Kevin O; Pate, Brooks H; Pratt, David W

    2011-04-28

    Recent advances in the technology of test and measurement equipment driven by the computer and telecommunications industries have made possible the development of a new broadband, Fourier-transform microwave spectrometer that operates on principles similar to FTNMR. This technique uses a high sample-rate arbitrary waveform generator to construct a phase-locked chirped microwave pulse that gives a linear frequency sweep over a wide frequency range in 1 μs. The chirped pulse efficiently polarizes the molecular sample at all frequencies lying within this band. The subsequent free induction decay of this polarization is measured with a high-speed digitizer and then fast Fourier-transformed to yield a broadband, frequency-resolved rotational spectrum, spanning up to 11.5 GHz and containing lines that are as narrow as 100 kHz. This new technique is called chirped-pulse Fourier transform microwave (CP-FTMW) spectroscopy. The technique offers the potential to determine the structural and dynamical properties of very large molecules solely from fully resolved pure rotational spectra. FTMW double resonance techniques employing a low-resolution UV laser facilitate an easy assignment of overlapping spectra produced by different conformers in the sample. Of particular interest are the energy landscapes of conformationally flexible molecules of biological importance, including studies of their interaction with solvent and/or other weakly bound molecules. An example is provided from the authors' work on p-methoxyphenethylamine, a neurotransmitter, and its complexes with water. PMID:21394332

  8. Polar Lows in Reanalyses and High Resolution Global Climate Models

    NASA Astrophysics Data System (ADS)

    Shaffrey, Len; Zappa, Giuseppe; Hodges, Kevin; Vidale, Pier Luigi

    2015-04-01

    Polar lows are maritime meso-cyclones associated with intense surface wind speeds and oceanic heat fluxes at high latitudes. The ability of the ERA-Interim (ERAI) reanalysis to represent polar lows in the North Atlantic is assessed by comparing ERAI and the ECMWF operational analysis for the period 2008-2011. The operational analysis has vorticity structures that better resemble the observed cloud patterns and stronger surface wind speed intensities compared to those in ERAI. By applying objective identification criteria, about 55% of the satellite observed polar lows are identified and tracked in ERAI, while this fraction increases to about 70% in the operational analysis. Particularly in ERAI, the remaining observed polar lows are mainly not identified because they have too weak wind speed and vorticity intensity compared to the tested criteria. The implications of the tendency of ERAI to underestimate the polar low dynamical intensity for future studies of polar lows is discussed. The ability of the Met Office HadGEM3 global climate model at different horizontal resolutions (150km, 60km and 25km) to capture Polar Lows will also be discussed.

  9. Polarizing agents and mechanisms for high-field dynamic nuclear polarization of frozen dielectric solids.

    PubMed

    Hu, Kan-Nian

    2011-09-01

    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-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 high-field 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 <20K, nuclear polarization using lower microwave power (<100 mW) is possible by forcing a high proportion of biradicals to

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

    SciTech Connect

    Heslar, John; Telnov, Dmitry; Chu, Shih-I

    2011-04-15

    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.

  11. Stochastic electrotransport selectively enhances the transport of highly electromobile molecules.

    PubMed

    Kim, Sung-Yon; Cho, Jae Hun; Murray, Evan; Bakh, Naveed; Choi, Heejin; Ohn, Kimberly; Ruelas, Luzdary; Hubbert, Austin; McCue, Meg; Vassallo, Sara L; Keller, Philipp J; Chung, Kwanghun

    2015-11-17

    Nondestructive chemical processing of porous samples such as fixed biological tissues typically relies on molecular diffusion. Diffusion into a porous structure is a slow process that significantly delays completion of chemical processing. Here, we present a novel electrokinetic method termed stochastic electrotransport for rapid nondestructive processing of porous samples. This method uses a rotational electric field to selectively disperse highly electromobile molecules throughout a porous sample without displacing the low-electromobility molecules that constitute the sample. Using computational models, we show that stochastic electrotransport can rapidly disperse electromobile molecules in a porous medium. We apply this method to completely clear mouse organs within 1-3 days and to stain them with nuclear dyes, proteins, and antibodies within 1 day. Our results demonstrate the potential of stochastic electrotransport to process large and dense tissue samples that were previously infeasible in time when relying on diffusion. PMID:26578787

  12. Stochastic electrotransport selectively enhances the transport of highly electromobile molecules

    PubMed Central

    Kim, Sung-Yon; Cho, Jae Hun; Murray, Evan; Bakh, Naveed; Choi, Heejin; Ohn, Kimberly; Ruelas, Luzdary; Hubbert, Austin; McCue, Meg; Vassallo, Sara L.; Keller, Philipp J.; Chung, Kwanghun

    2015-01-01

    Nondestructive chemical processing of porous samples such as fixed biological tissues typically relies on molecular diffusion. Diffusion into a porous structure is a slow process that significantly delays completion of chemical processing. Here, we present a novel electrokinetic method termed stochastic electrotransport for rapid nondestructive processing of porous samples. This method uses a rotational electric field to selectively disperse highly electromobile molecules throughout a porous sample without displacing the low-electromobility molecules that constitute the sample. Using computational models, we show that stochastic electrotransport can rapidly disperse electromobile molecules in a porous medium. We apply this method to completely clear mouse organs within 1–3 days and to stain them with nuclear dyes, proteins, and antibodies within 1 day. Our results demonstrate the potential of stochastic electrotransport to process large and dense tissue samples that were previously infeasible in time when relying on diffusion. PMID:26578787

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

    PubMed Central

    Hu, Kan-Nian

    2011-01-01

    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

  14. High Brightness and high polarization electron source using transmission photocathode

    SciTech Connect

    Yamamoto, Naoto; Jin Xiuguang; Ujihara, Toru; Takeda, Yoshikazu; Mano, Atsushi; Nakagawa, Yasuhide; Nakanishi, Tsutomu; Okumi, Shoji; Yamamoto, Masahiro; Konomi, Taro; Ohshima, Takashi; Saka, Takashi; Kato, Toshihiro; Horinaka, Hiromichi; Yasue, Tsuneo; Koshikawa, Takanori

    2009-08-04

    A transmission photocathode was fabricated based on GaAs-GaAsP strained superlattice layers on a GaP substrate and a 20 kV-gun was built to generate the polarized electron beams with the diameter of a few micro-meter. As the results, the reduced brightness of 1.3x10{sup 7} A/cm{sup 2}/sr and the polarization of 90% were achieved.

  15. Prospects for the formation of ultracold polar ground state KCs molecules via an optical process

    NASA Astrophysics Data System (ADS)

    Borsalino, D.; Vexiau, R.; Aymar, M.; Luc-Koenig, E.; Dulieu, O.; Bouloufa-Maafa, N.

    2016-03-01

    Heteronuclear alkali-metal dimers represent the class of molecules of choice for creating samples of ultracold molecules exhibiting an intrinsic large permanent electric dipole moment. Among them, the KCs molecule, with a permanent dipole moment of 1.92 Debye still remains to be observed in ultracold conditions. Based on spectroscopic studies available in the literature completed by accurate quantum chemistry calculations, we propose several optical coherent schemes to create ultracold bosonic and fermionic KCs molecules in their absolute rovibrational ground level, starting from a weakly bound level of their electronic ground state manifold. The processes rely on the existence of convenient electronically excited states allowing an efficient stimulated Raman adiabatic transfer of the level population.

  16. Coupled Hartree-Fock calculations of atomic polar tensors and the dipole polarisability of the benzene molecule

    NASA Astrophysics Data System (ADS)

    Lazzeretti, P.; Malagoli, M.; Zanasi, R.

    1990-03-01

    Coupled Hartree-Fock perturbation theory has been applied within the framework of high-quality basis sets to estimate the Hartree-Fock limit for the nuclear electric shielding tensors and the electric polarisability of the benzene molecule.

  17. Fusion with highly spin polarized HD and D sub 2

    SciTech Connect

    Honig, A. . Dept. of Physics); Kremens, R.; Skupsky, S. . Lab. for Laser Energetics)

    1991-05-05

    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.

  18. High Harmonic Spectroscopy of the Cooper Minimum in Molecules

    NASA Astrophysics Data System (ADS)

    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.

    2013-01-01

    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 λ=1.3 to 1.8μm. We demonstrate the CM to occur in CS2 and CCl4 at ˜42 and ˜40eV, 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 (CCl4, CH2Cl2, and trans-C2H2Cl2) and show that the position of the minimum is influenced by the molecular environment.

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

    PubMed Central

    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

    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 π 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

  20. Possibilities with pulsed polarized high density slow positrons

    NASA Astrophysics Data System (ADS)

    Mills, A. P., Jr.

    2014-04-01

    A particularly bright and intense polarized slow positron beam could be formed from isotopically enriched 79Kr produced at a reactor. After moderation with solid Ne, accumulation, compression, and bunching, this type of positron beam would enable a number of experiments including: (1) Long term storage of a neutral polarized electron-positron plasma in a cold box; (2) Pulsed e+ ACAR with a pulsed magnet to measure Fermi surfaces of paramagnetic metals; (3) Single shot measurements of positron annihilation in laser-imploding plasmas; (4) Study of a spin-polarized positronium gas at a density around that of ordinary air to produce a Ps Bose-Einstein condensate at room temperature; (5) High energy polarized positron channelling experiments to study polarized electron spatial wave functions in ferromagnets; and (6) Study of supersonic free expansion spin polarized BEC Ps jets formed from, for example, 1011 m=1 triplet Ps atoms created within an open ended 1 μm diameter cylindrical cavity 100 μm in length.

  1. Single-detector polarization-sensitive optical frequency domain imaging using high-speed intra A-line polarization modulation

    PubMed Central

    Oh, W. Y.; Vakoc, B. J.; Yun, S. H.; Tearney, G. J.; Bouma, B. E.

    2009-01-01

    We demonstrate a novel high-speed polarization-sensitive optical frequency domain imaging system employing high-speed polarization modulation. Rapid and continuous polarization modulation of light prior to illumination of the sample is accomplished by shifting the frequency of one polarization eigenstate by an amount equal to one quarter of the digitization sampling frequency. This approach enables polarization-sensitive imaging with a single detection channel and overcomes artifacts that may arise from temporal variations of the birefringence in fiber-optic imaging probes and spatial variation of birefringence in the sample. PMID:18552948

  2. A Monte Carlo study of the mesophases formed by polar bent-shaped molecules.

    PubMed

    Orlandi, Silvia; Berardi, Roberto; Steltzer, Joachim; Zannoni, Claudio

    2006-03-28

    Liquid crystal phases formed by bent-shaped (or "banana") molecules are currently of great interest. Here we investigate by Monte Carlo computer simulations the phases formed by rigid banana molecules modeled combining three Gay-Berne sites and containing either one central or two lateral and transversal dipoles. We show that changing the dipole position and orientation has a profound effect on the mesophase stability and molecular organization. In particular, we find a uniaxial nematic phase only for off-center dipolar models and tilted phases only for the one with terminal dipoles. PMID:16599725

  3. A Monte Carlo study of the mesophases formed by polar bent-shaped molecules

    NASA Astrophysics Data System (ADS)

    Orlandi, Silvia; Berardi, Roberto; Steltzer, Joachim; Zannoni, Claudio

    2006-03-01

    Liquid crystal phases formed by bent-shaped (or "banana") molecules are currently of great interest. Here we investigate by Monte Carlo computer simulations the phases formed by rigid banana molecules modeled combining three Gay-Berne sites and containing either one central or two lateral and transversal dipoles. We show that changing the dipole position and orientation has a profound effect on the mesophase stability and molecular organization. In particular, we find a uniaxial nematic phase only for off-center dipolar models and tilted phases only for the one with terminal dipoles.

  4. Biogeography of photoautotrophs in the high polar biome

    PubMed Central

    Pointing, Stephen B.; Burkhard Büdel; Convey, Peter; Gillman, Len N.; Körner, Christian; Leuzinger, Sebastian; Vincent, Warwick F.

    2015-01-01

    The global latitudinal gradient in biodiversity weakens in the high polar biome and so an alternative explanation for distribution of Arctic and Antarctic photoautotrophs is required. Here we identify how temporal, microclimate and evolutionary drivers of biogeography are important, rather than the macroclimate features that drive plant diversity patterns elsewhere. High polar ecosystems are biologically unique, with a more central role for bryophytes, lichens and microbial photoautotrophs over that of vascular plants. Constraints on vascular plants arise mainly due to stature and ontogenetic barriers. Conversely non-vascular plant and microbial photoautotroph distribution is correlated with favorable microclimates and the capacity for poikilohydric dormancy. Contemporary distribution also depends on evolutionary history, with adaptive and dispersal traits as well as legacy influencing biogeography. We highlight the relevance of these findings to predicting future impacts on diversity of polar photoautotrophs and to the current status of plants in Arctic and Antarctic conservation policy frameworks. PMID:26442009

  5. High resolution studies of atoms and small molecules

    SciTech Connect

    Bushaw, B.A.; Tonkyn, R.G.; Miller, R.J.

    1992-10-01

    High resolution, continuous wave lasers have been utilized successfully in studies of small molecules. Examples of two-photon excitation schemes and of multiple resonance excitation sequences will be discussed within the framework of the spectroscopy and dynamics of selected Rydberg states of nitric oxide. Initial results on the circular dichroism of angular distributions in photoelectron spectra of individual hyperfine states of cesium will also be discussed, but no data given.

  6. Molecular Dynamics Simulations on Parallel Computers: a Study of Polar Versus Nonpolar Media Effects in Small Molecule Solvation.

    NASA Astrophysics Data System (ADS)

    Debolt, Stephen Edward

    Solvent effects were studied and described via molecular dynamics (MD) and free energy perturbation (FEP) simulations using the molecular mechanics program AMBER. The following specific topics were explored:. Polar solvents cause a blue shift of the rm nto pi^* transition band of simple alkyl carbonyl compounds. The ground- versus excited-state solvation effects responsible for the observed solvatochromism are described in terms of the molecular level details of solute-solvent interactions in several modeled solvents spanning the range from polar to nonpolar, including water, methanol, and carbon tetrachloride. The structure and dynamics of octanol media were studied to explore the question: "why is octanol/water media such a good biophase analog?". The formation of linear and cyclic polymers of hydrogen-bonded solvent molecules, micelle-like clusters, and the effects of saturating waters are described. Two small drug-sized molecules, benzene and phenol, were solvated in water-saturated octanol. The solute-solvent structure and dynamics were analysed. The difference in their partitioning free energies was calculated. MD and FEP calculations were adapted for parallel computation, increasing their "speed" or the time span accessible by a simulation. The non-cyclic polyether ionophore salinomycin was studied in methanol solvent via parallel FEP. The path of binding and release for a potassium ion was investigated by calculating the potential of mean force along the "exit vector".

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

    SciTech Connect

    Babadi, Mehrtash; Demler, Eugene

    2011-09-15

    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.

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

    ERIC Educational Resources Information Center

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

    2012-01-01

    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…

  9. The microsporidian polar tube: A highly specialised invasion organelle

    PubMed Central

    Xu, Yanji; Weiss, Louis M.

    2011-01-01

    All of the members of the Microsporidia possess a unique, highly specialised structure, the polar tube. This article reviews the available data on the organisation, structure and function of this invasion organelle. It was over 100 years ago that Thelohan accurately described the microsporidian polar tube and the triggering of its discharge. In the spore, the polar tube is connected at the anterior end, and then coils around the sporoplasm. Upon appropriate environmental stimulation the polar tube rapidly discharges out of the spore pierces a cell membrane and serves as a conduit for sporoplasm passage into the new host cell. The mechanism of germination of spores, however, remains to be definitively determined. In addition, further studies on the characterisation of the early events in the rupture of the anterior attachment complex, eversion of the polar tube as well as the mechanism of host cell attachment and penetration are needed in order to clarify the function and assembly of this structure. The application of immunological and molecular techniques has resulted in the identification of three polar tube proteins referred to as PTP1, PTP2 and PTP3. The interactions of these identified proteins in the formation and function of the polar tube remain to be determined. Data suggest that PTP1 is an O-mannosylated glycoprotein, a post-translational modification that may be important for its function. With the availability of the Encephalitozoon cuniculi genome it is now possible to apply proteomic techniques to the characterisation of the components of the microsporidian spore and invasion organelle. PMID:16005007

  10. High-Resolution, Single-Molecule Measurements of Biomolecular Motion

    PubMed Central

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

    2007-01-01

    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. PMID:17328679

  11. The theoretical study of the ground-state polar chromium-alkali-metal-atom molecules

    NASA Astrophysics Data System (ADS)

    Deng, Lijuan; Gou, Dezhi; Chai, Junshuai

    2016-04-01

    Potential energy curves and permanent dipole moments of the 6Σ+ and 8Σ+ ground state of CrX (X = Li, Na, K, Rb and Cs) are calculated by employing the complete active space self-consistent field (CASSCF) and multi-reference configuration interaction (MRCI) methods. The spectroscopic constants for the 6Σ+ and 8Σ+ ground state of these molecules are calculated. Moreover, CrK, CrRb and CrCs molecules with large values of permanent dipole moment (CrK: 5.553 D, CrRb: 6.341 D and CrCs: 6.731 D) at the equilibrium bond distance are potentially interesting candidates for ultracold anisotropic long-range dipole-dipole interactions and many-body physics studies.

  12. Theoretical study of a positron-attachment to vibrational excited states for non-polar carbon disulfide molecule

    NASA Astrophysics Data System (ADS)

    Takeda, Yu; Kita, Yukiumi; Tachikawa, Masanori

    2016-06-01

    We theoretically analyzed a positron affinity (PA), which is the binding energy of a positron, of the non-polar carbon disulfide (CS2) molecule at vibrational excited states to elucidate the effect of molecular vibrations on the binding of positron to the molecule. Using the configuration interaction method of the multi-component molecular orbital theory and anharmonic vibrational state analysis with vibrational quantum Monte Carlo technique, the vibrational averaged PA values are calculated as 0.39, 2.03, and 5.02 meV for the ground state, fundamental tone, and overtone states of asymmetric stretching mode, respectively. The PA value of CS2 molecule is found to be enhanced by the vibrational excitation of only asymmetric stretching mode compared to the value at the vibrational ground state. With the linear regression analysis, we have confirmed that such enhancement of vibrational averaged PA values mainly arises from the increment of molecular permanent dipole moment due to the vibrational excitations of the asymmetric stretching mode.

  13. Long-range interactions between polar bialkali ground-state molecules in arbitrary vibrational levels

    NASA Astrophysics Data System (ADS)

    Vexiau, R.; Lepers, M.; Aymar, M.; Bouloufa-Maafa, N.; Dulieu, O.

    2015-06-01

    We have calculated the isotropic C6 coefficients characterizing the long-range van der Waals interaction between two identical heteronuclear alkali-metal diatomic molecules in the same arbitrary vibrational level of their ground electronic state X1Σ+. We consider the ten species made up of 7Li, 23Na, 39K, 87Rb, and 133Cs. Following our previous work [Lepers et al., Phys. Rev. A 88, 032709 (2013)], we use the sum-over-state formula inherent to the second-order perturbation theory, composed of the contributions from the transitions within the ground state levels, from the transition between ground-state and excited state levels, and from a crossed term. These calculations involve a combination of experimental and quantum-chemical data for potential energy curves and transition dipole moments. We also investigate the case where the two molecules are in different vibrational levels and we show that the Moelwyn-Hughes approximation is valid provided that it is applied for each of the three contributions to the sum-over-state formula. Our results are particularly relevant in the context of inelastic and reactive collisions between ultracold bialkali molecules in deeply bound or in Feshbach levels.

  14. Long-range interactions between polar bialkali ground-state molecules in arbitrary vibrational levels

    SciTech Connect

    Vexiau, R.; Lepers, M. Aymar, M.; Bouloufa-Maafa, N.; Dulieu, O.

    2015-06-07

    We have calculated the isotropic C{sub 6} coefficients characterizing the long-range van der Waals interaction between two identical heteronuclear alkali-metal diatomic molecules in the same arbitrary vibrational level of their ground electronic state X{sup 1}Σ{sup +}. We consider the ten species made up of {sup 7}Li, {sup 23}Na, {sup 39}K, {sup 87}Rb, and {sup 133}Cs. Following our previous work [Lepers et al., Phys. Rev. A 88, 032709 (2013)], we use the sum-over-state formula inherent to the second-order perturbation theory, composed of the contributions from the transitions within the ground state levels, from the transition between ground-state and excited state levels, and from a crossed term. These calculations involve a combination of experimental and quantum-chemical data for potential energy curves and transition dipole moments. We also investigate the case where the two molecules are in different vibrational levels and we show that the Moelwyn-Hughes approximation is valid provided that it is applied for each of the three contributions to the sum-over-state formula. Our results are particularly relevant in the context of inelastic and reactive collisions between ultracold bialkali molecules in deeply bound or in Feshbach levels.

  15. High-order disclinations in space-variant polarization

    NASA Astrophysics Data System (ADS)

    Khajavi, B.; Galvez, E. J.

    2016-08-01

    We present the investigation of high-order disinclination patterns in the spatially variable polarization of a light beam. The beam was prepared by encoding two distinct high-order optical vortices on each of the circular polarization components of the beam. As a consequence, we were able to produce high-index lemon and star patterns, which have positive and negative indices, respectively. By varying the asymmetry of one of the vortices we were able to transform one symmetric pattern (lemon or star) into another (lemon or star). With one exception, monstar patterns always appear for specific ranges of asymmetry regardless of the end symmetric patterns. Mapping of all disclinations within each case is contained in a spherical space, where monstar regions are cusp-shaped. We found that high-order monstar patterns can have positive or negative index.

  16. Single-molecule high-resolution imaging with photobleaching

    NASA Astrophysics Data System (ADS)

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

    2004-04-01

    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.

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

    SciTech Connect

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

    2010-03-15

    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.

  18. Predicting polarization performance of high-numerical aperture inspection lenses

    NASA Astrophysics Data System (ADS)

    Fahr, Stephan; Werschnik, Jan; Bening, Matthias; Uhlendorf, Kristina

    2015-09-01

    Along the course of increasing through-put and improving signal to noise ratio in optical wafer and mask inspection, demands on wave front aberrations and polarization characteristics are ever increasing. The system engineers and optical designers involved in the development of such optical systems will be responsible for specifying the quality of the optical material and the mechanical tolerances. Among optical designers it is well established how to estimate the wave front error of assembled and adjusted optical devices via sensitivity or Monte-Carlo analysis. However, when compared with the scalar problem of wave front estimation, the field of polarization control deems to pose a more complex problem due to its vectorial nature. Here we show our latest results in how to model polarization affecting aspects. In the realm of high numerical aperture (NA) inspection optics we will focus on the impact of coatings, stress induced birefringence due to non-perfect lens mounting, and finally the birefringence of the optical material. With all these tools at hand, we have a more complete understanding of the optical performance of our assembled optical systems. Moreover, we are able to coherently develop optical systems meeting demanding wave front criteria as well as high end polarization specifications.

  19. When is O+ Observed in the High Altitude Polar Cap?

    NASA Technical Reports Server (NTRS)

    Elliott, H. A.; Comfort, R. H.; Craven, P. D.; Chandler, M. O.; Moore, T. E.

    2000-01-01

    Solar wind and IMF properties are correlated with the properties of O+ and H+ in the polar cap at altitudes greater than 5.5 Re geocentric using the Thermal Ion Dynamics Experiment (TIDE) on the Polar satellite. O+ is of primary interest in this study because the fraction of O+ present in the magnetosphere is commonly used as a measure of the ionospheric contribution to the magnetosphere. O+ is observed to be most abundant at lower latitudes when the solar wind speed is low and across most of the polar cap at high solar winds speeds and Kp. As the solar wind dynamic pressures increases more O+ is present in the polar cap. The O+ density is also shown to be more highly correlated with the solar wind dynamic pressure when IMF Bz is positive. H+ was not as well correlated with solar wind and IMF parameters although some correlation with IMF By is observed. H+ is more plentiful when IMF By is negative than when it is positive. In this data set H+ is very dominate so that if this plasma makes it to the plasma sheet its contribution to the plasma sheet would have a very low O+ to H+ ratio.

  20. Radio properties of the highly polarized, quiescent quasar OI 287

    NASA Technical Reports Server (NTRS)

    Ulvestad, James S.; Antonucci, Robert R. J.

    1988-01-01

    The highly polarized, quiescent quasar OI 287 has been observed with high resolution at 2 cm and 6 cm in an effort to determine the origin of some of the object's peculiar properties. The results seem to rule out the classification of OI 287 as a blazar. Extrapolation of the radio core spectrum to midinfrared wavelengths fails to predict the infrared flux by at least an order of magnitude. This supports the conclusion that the infrared emission and the radio emission do not originate in the same synchrotron-emitting component. The high optical polarization could be related to possible broad absorption lines in the unobserved UV regime, or it could be caused by reflection into the line of sight by scattering agents distributed in a thin disk.

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

    SciTech Connect

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

    2000-06-21

    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.

  2. High contrast single molecule tracking in the pericellular coat

    NASA Astrophysics Data System (ADS)

    Scrimgeour, Jan; McLane, Louis T.; Curtis, Jennifer E.

    2014-03-01

    The pericellular coat is a robust, hydrated, polymer brush-like structure that can extend several micrometers into the extracellular space around living cells. By controlling access to the cell surface, acting as a filter and storage reservoir for proteins, and actively controlling tissue-immune system interactions, the cell coat performs many important functions at scales ranging from the single cell to whole tissues. The cell coat consists of a malleable backbone - the large polysaccharide hyaluronic acid (HA) - with its structure, material properties, and ultimately its bio-functionality tuned by a diverse set of HA binding proteins. These proteins add charge, cross-links and growth factor-like ligands to the coat To probe the dynamic behavior of this soft biomaterial we have used high contrast single molecule imaging, based on highly inclined laser illumination, to observe individual fluorescently labeled HA binding proteins within the cell coat. Our work focuses on the cell coat of living chondrocyte (cartilage) cells, and in particular the effect of the large, highly charged, protein aggrecan on the properties of the coat. Through single molecule imaging we observe that aggrecan is tightly tethered to HA, and plays an important role in cell coat extension and stiffening.

  3. Quantum control of ultracold NaK polar molecules in optical traps

    NASA Astrophysics Data System (ADS)

    Li, Ming; Petrov, Alexander; Makrides, Constantinos; Kotochigova, Svetlana

    2016-05-01

    Selection of trapping conditions with ultracold molecules, where internal states experience identical trapping potentials, brings substantial benefits for the ultimate control of their internal degrees of freedom. Here we present our work on the control of NaK molecules, when they are subjected to both trapping laser light and external electric and magnetic fields. First, we calculated parallel and perpendicular polarizabilities using a coupled-cluster method at the CCSD level. This enables us to determine the differential Stark shifts of rotational levels of NaK as a function of orientation of external fields. The hyperfine and Zeeman structure of these rotational states was obtained using an effective spin Hamiltonian. We find that under the experimental conditions with NaK, the hyperfine sublevels of the J = 1 rotational state are significantly mixed by the trapping laser light so that the simplified model of Ref. for ``magic'' conditions can not be applied. Adding a modest static electric field, however, can minimize the mixing of magnetic sublevels and make it easier to find ``magic'' conditions. This work is supported by the ARO-MURI Grant No. W911NF-12-1-0476 and the NSF Grant No. PHY-1308573.

  4. Applications of highly spin-polarized xenon in NMR

    SciTech Connect

    Long, H.W. |

    1993-09-01

    The main goal of the work presented in this thesis is produce highly spin-polarized xenon to create much greater signal intensities (up to 54,000 times greater) so as to allow studies to be made on systems with low surface area and long spin-lattice relaxation times. The spin-exchange optical pumping technique used to create high nuclear spin polarization is described in detail in chapter two. This technique is initially applied to some multiple-pulse optically detected NMR experiments in low magnetic field (50G) that allow the study of quadrupoler interactions with a surface of only a few square centimeters. In chapter three the apparatus used to allow high field {sup 129}Xe NMR studies to be performed with extremely high sensitivity is described and applied to experiments on diamagnetic susceptibility effects in thin ({approximately}2000 layers) films of frozen xenon. Preliminary surface investigations of laser polarized {sup 129}Xe adsorbed an a variety of materials (salts, molecular crystals, amorphous carbon, graphite) are then discussed. A full detailed study of the surface of a particular polymer, poly(acrylic acid), is presented in chapter four which shows the kind of detailed information that can be obtained from this technique. Along with preliminary results for several similar polymers, a summary is given of xenon studies of a novel ultra-high surface area polymer, poly(triarylcarbinol). Finally in chapter five the exciting possibility of transferring the high spin order of the laser polarized xenon has been used to transfer nuclear spin order to {sup 13}CO{sub 2} in a xenon matrix and to protons on poly(triarylcarbinol).

  5. Microwave studies of collision-induced transitions between rotational levels. VIII. Collisions between NH/sub 3/ and polar molecules

    SciTech Connect

    Fabris, A.R.; Oka, T.

    1983-03-15

    The technique of four-level microwave double resonance has been applied to the study of rotation-inversion transitions of NH/sub 3/ induced by collisions with various polar molecules. H/sub 2/O, D/sub 2/O, CH/sub 3/OH, CH/sub 3/X and CHX/sub 3/ (X = F, Cl, Br, I), NO, CO, and OCS were used as collision partners. The values of eta = ..delta..I/I observed for many four-level systems which are connected by dipole-type transitions (..delta..J = +- 1, ..delta..K = 0, parity +bold-arrow-left-right-) are given and qualitatively explained taking into account the long-range dipole--dipole interaction and the pattern of rotational energy levels of the collision partners.

  6. Ferromagnetic Polarization: The Quantum Picture of Switching On/Off Single-Molecule Magnetism.

    PubMed

    Cao, Fan; Wei, Rong-Min; Li, Jing; Yang, Li; Han, Yuan; Song, You; Dou, Jian-Min

    2016-06-20

    The mixed 3d-4f pentanuclear complex (Bu4N)[Mn(III)4Y(III)(shi)4(OAc)4(CH3OH)4]·CH3OH·H2O (1) (H3shi = salicylhydroxamic acid) was synthesized by the direct reaction of Y(NO3)3·6H2O, Mn(OAc)2·4H2O, and H3shi. When an additional ligand, (NHBu3)3[W(CN)8]·2H2O, was added, the mixed 3d-4f-5d hexanuclear complex (Et4N)5[Mn(III)4Y(III)(shi)4(OAc)4W(V)(CN)8](WO4)0.5 (2) was obtained. X-ray crystallographic analysis shows that the 3d-4f complex 1 represents a 12-metallacrown-4 (12-MC-4) structure, in which the metallacrown ring [Mn-N-O]4 connection captures one Y(III) ion with four bridging acetate anions, completing the eight-coordinated environment around Y(III) ion, while four methanol molecules each coordinate to the Mn(III) ions on the other side of the Y(III) ion. After octacyanotungstate is introduced, the [W(V)(CN)8] group substitutes for four methanol molecules of 1 to form complex 2. Magnetic studies indicate the overall antiferromagnetic coupling present within the MC ring of complex 1. However, interestingly, the dominant ferromagnetic coupling between Mn(III) ions was observed in complex 2. A susceptibility analysis shows that the natural spin alignments in 12-MC-4 metallacrowns are tuned from overall antiferromagnetic to dominant ferromagnetic fashions by magnetic coupling between Mn(III) ions and the W(V) ion. Complex 1 [Mn(III)4Y(III)] retains an S = 0 ground state, and complex 2 [Mn(III)4Y(III)W(V)] shows obvious single-molecule magnet (SMM) behavior with an ST = 11/2 ground state, respectively, before and after introduction of the octacyanotungstate group. The spin frustration geometrical structure constructed by four Mn(III) ions and one W(V) ion was considered as the key factor for switching on the SMM properties of the 12-MC-4 system. PMID:27228007

  7. Mechanism of dynamic nuclear polarization in high magnetic fields

    NASA Astrophysics Data System (ADS)

    Farrar, C. T.; Hall, D. A.; Gerfen, G. J.; Inati, S. J.; Griffin, R. G.

    2001-03-01

    Solid-state NMR signal enhancements of about two orders of magnitude (100-400) have been observed in dynamic nuclear polarization (DNP) experiments performed at high magnetic field (5 T) and low temperature (10 K) using the nitroxide radical 4-amino TEMPO as the source of electron polarization. Since the breadth of the 4-amino TEMPO EPR spectrum is large compared to the nuclear Larmor frequency, it has been assumed that thermal mixing (TM) is the dominate mechanism by which polarization is transferred from electron to nuclear spins. However, theoretical explanations of TM generally assume a homogeneously broadened EPR line and, since the 4-amino TEMPO line at 5 T is inhomogeneously broadened, they do not explain the observed DNP enhancements. Accordingly, we have developed a treatment of DNP that explicitly uses electron-electron cross-relaxation to mediate electron-nuclear polarization transfer. The process proceeds via spin flip-flops between pairs of electronic spin packets whose Zeeman temperatures differ from one another. To confirm the essential features of the model we have studied the field dependence of electron-electron double resonance (ELDOR) data and DNP enhancement data. Both are well simulated using a simple model of electron cross-relaxation in the inhomogeneously broadened 4-amino TEMPO EPR line.

  8. Anchoring transitions of transversely polar liquid-crystal molecules on perfluoropolymer surfaces.

    PubMed

    Dhara, Surajit; Kim, Jin Ki; Jeong, Soon Moon; Kogo, Reiri; Araoka, Fumito; Ishikawa, Ken; Takezoe, Hideo

    2009-06-01

    We report a strong discontinuous orientational transition (anchoring transition) of liquid-crystal molecules with a large transverse dipole moment. A perfluoropolymer was used as an alignment layer and the transition was observed from planar to homeotropic with decreasing temperature in the nematic phase. Conversely a gradual variation in tilt angle from homeotropic to conical was observed in a liquid crystal with a comparatively smaller transverse dipole moment on the same alignment layer. The experimental results clearly demonstrate the competition between a short-range dipolar force and long-range van der Waals force at the interfacial region. Using discontinuous anchoring transition in the sample, we demonstrate a possible bistable device for memory and light-driven display. PMID:19658464

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

    PubMed Central

    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

    2011-01-01

    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. PMID:21706006

  10. High-fidelity linear optical quantum computing with polarization encoding

    SciTech Connect

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

    2006-01-15

    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.

  11. Photoelectron momentum distributions of molecules in bichromatic circularly polarized attosecond UV laser fields

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Chelkowski, Szczepan; Bandrauk, André D.

    2016-05-01

    We theoretically investigate molecular photoelectron momentum distributions (MPMDs) by bichromatic [frequencies (ω1,ω2)] circularly polarized attosecond UV laser pulses. Simulations performed on aligned single-electron H2+ by numerically solving the corresponding three-dimensional time-dependent Schrödinger equation within a static nucleus frame show that MPMDs exhibit a spiral structure for both co-rotating and counter-rotating schemes. Results are analyzed by attosecond perturbation ionization models. Coherent electron wave packets created, respectively, by the two color pulses in the continuum interfere with each other. Photoionization distributions are functions of the photoelectron momentum p and the ejection angle θ , thus leading to spiral MPMDs. The dependence of spiral MPMDs on the time delay between the bicircular pulses and their relative phases is also presented. The spiral interference patterns are determined by the helicities and frequencies (ω1,ω2 ) of the bicircular fields. It is also found that the spiral patterns are sensitive to the molecular alignment and suppressed by two-center ionization interference, thus offering new tools for imaging molecular geometry.

  12. High transmittance silicon terahertz polarizer using wafer bonding technology

    NASA Astrophysics Data System (ADS)

    Yu, Ting-Yang; Tsai, Hsin-Cheng; Wang, Shiang-Yu; Luo, Chih-Wei; Chen, Kuan-Neng

    2015-08-01

    Due to the difficulties faced in fabricating robust Terahertz (THz) optical components with low Fresnel reflection loss, the need to increase the efficiency of THz system with reduced cost is still considered as one of the most essential tasks. In this report, a new low cost THz polarizer with robust structure is proposed and demonstrated. This new THz wire grid polarizer was based on an anti-reflection (AR) layer fabricated with low temperature metal bonding and deep reactive ion etching (DRIE). After patterning Cu wire gratings and the corresponding In/Sn solder ring on the individual silicon wafers, the inner gratings were sealed by wafer-level Cu to In/Sn guard ring bonding, providing the protection against humidity oxidation and corrosion. With the low eutectic melting point of In/Sn solder, wafers could be bonded face to face below 150°C. Two anti-reflection layers on both outward surfaces were fabricated by DRIE. With the mixing of empty holes and silicon, the effective refractive index was designed to be the square root of the silicon refractive index. The central frequency of the anti-reflection layers was designed between 0.5THz to 2THz with an approximate bandwidth of 0.5THz. The samples were measured with a commercial free-standing wire grid polarizer by a THz time domain spectroscopy (THz-TDS) from 0.2THz to 2.2THz. The power transmittance is close to 100% at central frequency. Extinction ratio of the polarizer is between 20dB to 40dB depending on the frequency. The advantages of this new polarizer include high transmittance, robust structure and low cost with no precision optical alignment required.

  13. Quantum switching of π-electron rotations in a nonplanar chiral molecule by using linearly polarized UV laser pulses.

    PubMed

    Mineo, Hirobumi; Yamaki, Masahiro; Teranishi, Yoshiaki; Hayashi, Michitoshi; Lin, Sheng Hsien; Fujimura, Yuichi

    2012-09-01

    Nonplanar chiral aromatic molecules are candidates for use as building blocks of multidimensional switching devices because the π electrons can generate ring currents with a variety of directions. We employed (P)-2,2'-biphenol because four patterns of π-electron rotations along the two phenol rings are possible and theoretically determine how quantum switching of the π-electron rotations can be realized. We found that each rotational pattern can be driven by a coherent excitation of two electronic states under two conditions: one is the symmetry of the electronic states and the other is their relative phase. On the basis of the results of quantum dynamics simulations, we propose a quantum control method for sequential switching among the four rotational patterns that can be performed by using ultrashort overlapped pump and dump pulses with properly selected relative phases and photon polarization directions. The results serve as a theoretical basis for the design of confined ultrafast switching of ring currents of nonplanar molecules and further current-induced magnetic fluxes of more sophisticated systems. PMID:22889209

  14. Manipulating the dipole layer of polar organic molecules on metal surfaces via different charge-transfer channels

    NASA Astrophysics Data System (ADS)

    Lin, Meng-Kai; Nakayama, Yasuo; Zhuang, Ying-Jie; Wang, Chin-Yung; Pi, Tun-Wen; Ishii, Hisao; Tang, S.-J.

    The key properties of organic films such as energy level alignment (ELA), work functions, and injection barriers are closely linked to this dipole layer. Using angle resolved photoemission spectroscopy (ARPES), we systemically investigate the coverage-dependent work functions and spectra line shapes of occupied molecular orbital states of a polar molecule, chloroaluminium phthalocyanine (ClAlPc), grown on Ag(111) to show that the orientations of the first ClAlPc layer can be manipulated via the molecule deposition rate and post annealing, causing ELA at organic-metal interface to differ for about 0.3 eV between Cl-up and Cl-down configuration. Moreover, by comparing the experimental results with the calculations based on both gas-phase model and realistic model of ClAlPc on Ag(111) , we evidence that the different orientations of ClAlPc dipole layers lead to different charge-transfer channels between ClAlPc and Ag, a key factor that controls the ELA at organic-metal interface.

  15. A 3D-printed high power nuclear spin polarizer.

    PubMed

    Nikolaou, Panayiotis; Coffey, Aaron M; Walkup, Laura L; Gust, Brogan M; LaPierre, Cristen D; Koehnemann, Edward; Barlow, Michael J; Rosen, Matthew S; Goodson, Boyd M; Chekmenev, Eduard Y

    2014-01-29

    Three-dimensional printing with high-temperature plastic is used to enable spin exchange optical pumping (SEOP) and hyperpolarization of xenon-129 gas. The use of 3D printed structures increases the simplicity of integration of the following key components with a variable temperature SEOP probe: (i) in situ NMR circuit operating at 84 kHz (Larmor frequencies of (129)Xe and (1)H nuclear spins), (ii) <0.3 nm narrowed 200 W laser source, (iii) in situ high-resolution near-IR spectroscopy, (iv) thermoelectric temperature control, (v) retroreflection optics, and (vi) optomechanical alignment system. The rapid prototyping endowed by 3D printing dramatically reduces production time and expenses while allowing reproducibility and integration of "off-the-shelf" components and enables the concept of printing on demand. The utility of this SEOP setup is demonstrated here to obtain near-unity (129)Xe polarization values in a 0.5 L optical pumping cell, including ∼74 ± 7% at 1000 Torr xenon partial pressure, a record value at such high Xe density. Values for the (129)Xe polarization exponential build-up rate [(3.63 ± 0.15) × 10(-2) min(-1)] and in-cell (129)Xe spin-lattice relaxation time (T1 = 2.19 ± 0.06 h) for 1000 Torr Xe were in excellent agreement with the ratio of the gas-phase polarizations for (129)Xe and Rb (PRb ∼ 96%). Hyperpolarization-enhanced (129)Xe gas imaging was demonstrated with a spherical phantom following automated gas transfer from the polarizer. Taken together, these results support the development of a wide range of chemical, biochemical, material science, and biomedical applications. PMID:24400919

  16. A 3D-Printed High Power Nuclear Spin Polarizer

    PubMed Central

    Nikolaou, Panayiotis; Coffey, Aaron M.; Walkup, Laura L.; Gust, Brogan M.; LaPierre, Cristen D.; Koehnemann, Edward; Barlow, Michael J.; Rosen, Matthew S.; Goodson, Boyd M.; Chekmenev, Eduard Y.

    2015-01-01

    Three-dimensional printing with high-temperature plastic is used to enable spin exchange optical pumping (SEOP) and hyperpolarization of xenon-129 gas. The use of 3D printed structures increases the simplicity of integration of the following key components with a variable temperature SEOP probe: (i) in situ NMR circuit operating at 84 kHz (Larmor frequencies of 129Xe and 1H nuclear spins), (ii) <0.3 nm narrowed 200 W laser source, (iii) in situ high-resolution near-IR spectroscopy, (iv) thermoelectric temperature control, (v) retroreflection optics, and (vi) optomechanical alignment system. The rapid prototyping endowed by 3D printing dramatically reduces production time and expenses while allowing reproducibility and integration of “off-the-shelf” components and enables the concept of printing on demand. The utility of this SEOP setup is demonstrated here to obtain near-unity 129Xe polarization values in a 0.5 L optical pumping cell, including ~74 ± 7% at 1000 Torr xenon partial pressure, a record value at such high Xe density. Values for the 129Xe polarization exponential build-up rate [(3.63 ± 0.15) × 10−2 min−1] and in-cell 129Xe spin−lattice relaxation time (T1 = 2.19 ± 0.06 h) for 1000 Torr Xe were in excellent agreement with the ratio of the gas-phase polarizations for 129Xe and Rb (PRb ~ 96%). Hyperpolarization-enhanced 129Xe gas imaging was demonstrated with a spherical phantom following automated gas transfer from the polarizer. Taken together, these results support the development of a wide range of chemical, biochemical, material science, and biomedical applications. PMID:24400919

  17. Kohn-Sham approach to Fermi gas superfluidity: The bilayer of fermionic polar molecules

    NASA Astrophysics Data System (ADS)

    Ancilotto, Francesco

    2016-05-01

    By using a well-established "ab initio" theoretical approach developed in the past to quantitatively study the superconductivity of condensed matter systems, based on the Kohn-Sham density functional theory, I study the superfluid properties and the BCS-BEC crossover of two parallel bi-dimensional layers of fermionic dipolar molecules, where the pairing mechanism leading to superfluidity is provided by the interlayer coupling between dipoles. The finite temperature superfluid properties of both the homogeneous system and one where the fermions in each layer are confined by a square optical lattice are studied at half filling conditions, and for different values of the strength of the confining optical potential. The T = 0 results for the homogeneous system are found to be in excellent agreement with diffusion Monte Carlo results. The superfluid transition temperature in the BCS region is found to increase, for a given interlayer coupling, with the strength of the confining optical potential. A transition occurs at sufficiently small interlayer distances, where the fermions becomes localized within the optical lattice sites in a square geometry with an increased effective lattice constant, forming a system of localized composite bosons. This transition should be signaled by a sudden drop in the superfluid fraction of the system.

  18. Tomographic reconstruction of circularly polarized high-harmonic fields: 3D attosecond metrology

    PubMed Central

    Chen, Cong; Tao, Zhensheng; Hernández-García, Carlos; Matyba, Piotr; Carr, Adra; Knut, Ronny; Kfir, Ofer; Zusin, Dimitry; Gentry, Christian; Grychtol, Patrik; Cohen, Oren; Plaja, Luis; Becker, Andreas; Jaron-Becker, Agnieszka; Kapteyn, Henry; Murnane, Margaret

    2016-01-01

    Bright, circularly polarized, extreme ultraviolet (EUV) and soft x-ray high-harmonic beams can now be produced using counter-rotating circularly polarized driving laser fields. Although the resulting circularly polarized harmonics consist of relatively simple pairs of peaks in the spectral domain, in the time domain, the field is predicted to emerge as a complex series of rotating linearly polarized bursts, varying rapidly in amplitude, frequency, and polarization. We extend attosecond metrology techniques to circularly polarized light by simultaneously irradiating a copper surface with circularly polarized high-harmonic and linearly polarized infrared laser fields. The resulting temporal modulation of the photoelectron spectra carries essential phase information about the EUV field. Utilizing the polarization selectivity of the solid surface and by rotating the circularly polarized EUV field in space, we fully retrieve the amplitude and phase of the circularly polarized harmonics, allowing us to reconstruct one of the most complex coherent light fields produced to date. PMID:26989782

  19. Identification of Small-Molecule Inhibitors of the HuR/RNA Interaction Using a Fluorescence Polarization Screening Assay Followed by NMR Validation

    PubMed Central

    Wang, Zhonghua; Bhattacharya, Akash; Ivanov, Dmitri N.

    2015-01-01

    The human antigen R (HuR) stabilizes many mRNAs of proto-oncogene, transcription factors, cytokines and growth factors by recognizing AU-rich elements (AREs) presented in their 3’ or 5’ untranslated region (UTR). Multiple lines of experimental evidence suggest that this process plays a key role in cancer development. Thus, destabilizing HuR/RNA interaction by small molecules presents an opportunity for cancer treatment/prevention. Here we present an integrated approach to identify inhibitors of HuR/RNA interaction using a combination of fluorescence-based and NMR-based high throughput screening (HTS). The HTS assay with fluorescence polarization readout and Z’-score of 0.8 was used to perform a screen of the NCI diversity set V library in a 384 well plate format. An NMR-based assay with saturation transfer difference (STD) detection was used for hits validation. Protein NMR spectroscopy was used to demonstrate that some hit compounds disrupt formation of HuR oligomer, whereas others block RNA binding. Thus, our integrated high throughput approach provides a new avenue for identification of small molecules targeting HuR/RNA interaction. PMID:26390015

  20. Polarization interferometric nulling coronagraph for high-contrast imaging.

    PubMed

    Murakami, Naoshi; Yokochi, Kaito; Nishikawa, Jun; Tamura, Motohide; Kurokawa, Takashi; Takeda, Mitsuo; Baba, Naoshi

    2010-06-01

    We propose a novel, high-contrast imager called a polarization interferometric nulling coronagraph (PINC) for direct detection of extrasolar planets. The PINC uses achromatic half-wave plates (HWPs) installed in a fully symmetric beam combiner based on polarizing beam splitters. Jones calculus suggests that a stellar halo suppression level of 10(-10) can be achieved at 5 lambda/D for a broad wavelength range from 1.6 to 2.2 microm by using Fresnel-rhomb HWPs made of BK7. Laboratory experiments on the PINC used two laser light sources (wavelengths of lambda=532 and 671 nm), and we obtained a halo suppression level of approximately 10(-6) at 5 lambda/D for both wavelengths. PMID:20517351

  1. Evidence for accretion disks in highly polarized quasars

    NASA Technical Reports Server (NTRS)

    Smith, Paul S.; Elston, Richard; Berriman, Graham; Allen, Richard G.; Balonek, Thomas J.

    1988-01-01

    The results of a search for thermal components in 11 highly polarized quasars (HPQs) using UVBRI polarimetry and photometry are reported. The 2000-2500 A luminosities of the thermal components are calculated and the estimated luminosities of the broad-line region (BLR) are given in the same wavelength for comparison. The observed optical continua are modeled as a combination of polarized synchrotron emission, unpolarized emission from the BLR, and an unpolarized flat spectral component that may be optically thick thermal emission from an accretion disk. Evidence for thermal emission components is found in three HPQs: PKS 0420-014, B2 1156+295, and 3C 454.3, with marginal evidence in another two, PKS 1510-089 and PKS 2345-167.

  2. Invited Article: Broadband highly efficient dielectric metadevices for polarization control

    NASA Astrophysics Data System (ADS)

    Kruk, Sergey; Hopkins, Ben; Kravchenko, Ivan I.; Miroshnichenko, Andrey; Neshev, Dragomir N.; Kivshar, Yuri S.

    2016-06-01

    Metadevices based on dielectric nanostructured surfaces with both electric and magnetic Mie-type resonances have resulted in the best efficiency to date for functional flat optics with only one disadvantage: a narrow operational bandwidth. Here we experimentally demonstrate broadband transparent all-dielectric metasurfaces for highly efficient polarization manipulation. We utilize the generalized Huygens principle, with a superposition of the scattering contributions from several electric and magnetic multipolar modes of the constituent meta-atoms, to achieve destructive interference in reflection over a large spectral bandwidth. By employing this novel concept, we demonstrate reflectionless (˜90% transmission) half-wave plates, quarter-wave plates, and vector beam q-plates that can operate across multiple telecom bands with ˜99% polarization conversion efficiency.

  3. Bioluminescence in the high Arctic during the polar night.

    PubMed

    Berge, J; Båtnes, A S; Johnsen, G; Blackwell, S M; Moline, M A

    2012-01-01

    This study examines the composition and activity of the planktonic community during the polar night in the high Arctic Kongsfjord, Svalbard. Our results are the first published evidence of bioluminescence among zooplankton during the Arctic polar night. The observations were collected by a bathyphotometer detecting bioluminescence, integrated into an autonomous underwater vehicle, to determine the concentration and intensity of bioluminescent flashes as a function of time of day and depth. To further understand community dynamics and composition, plankton nets were used to collect organisms passing through the bathyphotometer along with traditional vertical net tows. Additionally, using a moored bathyphotometer closed to the sampling site, the bioluminescence potential itself was shown not to have a diurnal or circadian rhythm. Rather, our results provide evidence for a diel vertical migration of bioluminescent zooplankton that does not correspond to any externally detectable changes in illumination. PMID:24489409

  4. Recoil-Proton Polarization in High-Energy Deuteron Photodisintegration with Circularly Polarized Photons

    SciTech Connect

    Jiang, X.; Benmokhtar, F.; Glashauser, C.; McCormick, K.; Ransome, R. D.; Arrington, J.; Holt, R. J.; Reimer, P. E.; Schulte, E. C.; Wijesooriya, K.; Camsonne, A.

    2007-05-04

    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.

  5. Recoil-Proton Polarization in High-Energy Deuteron Photodisintegration with Circularly Polarized Photons

    SciTech Connect

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

    2007-05-01

    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.

  6. Quantitative isoform-profiling of highly diversified recognition molecules

    PubMed Central

    Schreiner, Dietmar; Simicevic, Jovan; Ahrné, Erik; Schmidt, Alexander; Scheiffele, Peter

    2015-01-01

    Complex biological systems rely on cell surface cues that govern cellular self-recognition and selective interactions with appropriate partners. Molecular diversification of cell surface recognition molecules through DNA recombination and complex alternative splicing has emerged as an important principle for encoding such interactions. However, the lack of tools to specifically detect and quantify receptor protein isoforms is a major impediment to functional studies. We here developed a workflow for targeted mass spectrometry by selected reaction monitoring that permits quantitative assessment of highly diversified protein families. We apply this workflow to dissecting the molecular diversity of the neuronal neurexin receptors and uncover an alternative splicing-dependent recognition code for synaptic ligands. DOI: http://dx.doi.org/10.7554/eLife.07794.001 PMID:25985086

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

    NASA Astrophysics Data System (ADS)

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

    1999-08-01

    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/θ) coordinates. The asymmetry of the spring vortices results in coverage of subtropical to polar EqLs. EqL/θ fields of long-lived tracers in spring in both hemispheres show the net effects of descent at high EqL throughout the winter, reflecting strong descent in the upper stratosphere, decreasing descent at lower altitudes, and evidence of greater descent at the edge of the lower stratospheric vortex than in the vortex center; these results are consistent with trajectory calculations examining the history of the air measured by ATMOS in the month prior to each mission. EqL/θ tracer fields, the derived fields CH4-CH4* (CH4* is the expected CH4 calculated from a prescribed relationship with N2O for fall) and NOy-NOy* (analogous to CH4*), and parcel histories all indicate regions of strong mixing in the 1994 Southern Hemisphere (SH) spring vortex above 500 K, with the strongest mixing confined to the vortex edge region between 500 and 700 K, and mixing throughout the Northern Hemisphere (NH) spring vortex in 1993 below about 850 K. Parcel histories indicate mixing of extravortex air with air near the vortex edge below 500 K in the SH but not with air in the vortex core; they show extravortex air mixing well into the vortex above ˜450 K in the NH and into the vortex edge region below. The effects of severe denitrification are apparent in EqL/θ HNO3 in the SH lower stratospheric spring vortex. The morphology of HNO3 in the Arctic spring lower stratospheric vortex is consistent with the effects of descent. EqL/θ fields of ATMOS NOy-NOy* show decreases consistent with the effects of mixing throughout the NH lower stratospheric vortex. The Eq

  8. Microbial Communities in a High Arctic Polar Desert Landscape

    PubMed Central

    McCann, Clare M.; Wade, Matthew J.; Gray, Neil D.; Roberts, Jennifer A.; Hubert, Casey R. J.; Graham, David W.

    2016-01-01

    The High Arctic is dominated by polar desert habitats whose microbial communities are poorly understood. In this study, we used next generation sequencing to describe the α- and β-diversity of microbial communities in polar desert soils from the Kongsfjorden region of Svalbard. Ten phyla dominated the soils and accounted for 95% of all sequences, with the Proteobacteria, Actinobacteria, and Chloroflexi being the major lineages. In contrast to previous investigations of Arctic soils, relative Acidobacterial abundances were found to be very low as were the Archaea throughout the Kongsfjorden polar desert landscape. Lower Acidobacterial abundances were attributed to characteristic circumneutral soil pHs in this region, which has resulted from the weathering of underlying carbonate bedrock. In addition, we compared previously measured geochemical conditions as possible controls on soil microbial communities. Phosphorus, pH, nitrogen, and calcium levels all significantly correlated with β-diversity, indicating landscape-scale lithological control of available nutrients, which in turn, significantly influenced soil community composition. In addition, soil phosphorus and pH significantly correlated with α-diversity, particularly with the Shannon diversity and Chao 1 richness indices. PMID:27065980

  9. Microbial Communities in a High Arctic Polar Desert Landscape.

    PubMed

    McCann, Clare M; Wade, Matthew J; Gray, Neil D; Roberts, Jennifer A; Hubert, Casey R J; Graham, David W

    2016-01-01

    The High Arctic is dominated by polar desert habitats whose microbial communities are poorly understood. In this study, we used next generation sequencing to describe the α- and β-diversity of microbial communities in polar desert soils from the Kongsfjorden region of Svalbard. Ten phyla dominated the soils and accounted for 95% of all sequences, with the Proteobacteria, Actinobacteria, and Chloroflexi being the major lineages. In contrast to previous investigations of Arctic soils, relative Acidobacterial abundances were found to be very low as were the Archaea throughout the Kongsfjorden polar desert landscape. Lower Acidobacterial abundances were attributed to characteristic circumneutral soil pHs in this region, which has resulted from the weathering of underlying carbonate bedrock. In addition, we compared previously measured geochemical conditions as possible controls on soil microbial communities. Phosphorus, pH, nitrogen, and calcium levels all significantly correlated with β-diversity, indicating landscape-scale lithological control of available nutrients, which in turn, significantly influenced soil community composition. In addition, soil phosphorus and pH significantly correlated with α-diversity, particularly with the Shannon diversity and Chao 1 richness indices. PMID:27065980

  10. Plasma density increase in the high altitude polar cap

    NASA Astrophysics Data System (ADS)

    Kitanoya, Yugo; Abe, Takumi; Mukai, Toshifumi

    In general situation, the electron density in the ionosphere decreases with altitude. As for the latitudinal variation, the electron density is generally smaller in the polar cap than in the midor low-latitude region. Few reliable measurements have been made to estimate thermal electron density and temperature with a simple instrument such as Langmuir probe in the highaltitude polar cap region. For example, only the limited amount of the electron temperature and density data are available for the high-altitude (> 3000 km) polar cap, where the density is generally less than 2.0*103 [/cm3 ]. Since the plasma density significantly correlates with the solar activity, thermal plasma density becomes smaller for the minimum solar activity period. Thermal Electron energy Distribution (TED) instrument onboard "AKEBONO" (EXOS-D) satellite has been operated in two modes; 1) DC mode to obtain the probe characteristic, 2) SH (second harmonic) mode to estimate the electron energy distribution function based on Druyvesteyn method, from which the electron temperature and density can be estimated even on the condition of low electron density. On the basis of statistical study of the Akebono observation for over 10 years, it is found that the electron number density occasionally increases up to 3.0-4.0*103 [/cm3 ] above altitude of 3000 km. While the electron temperature is believed to be about 8000 K at such a high altitude, the temperature inside the high density region is observed to be lower than that by several thousand degrees. It is noticeable that such a density enhancement occurs during the geomagnetically active period at solar maximum. The high density region is observed to exist not in whole but in part of the polar cap. In addition, it is obvious from the Suprathermal Mass Spectrometer (SMS) observations that the H+ velocity parallel to the upward field aligned direction is observed to be lower in the high density region than the surrounding region. Also, it is

  11. High performance photovoltaic applications using solution-processed small molecules.

    PubMed

    Chen, Yongsheng; Wan, Xiangjian; Long, Guankui

    2013-11-19

    Energy remains a critical issue for the survival and prosperity of humancivilization. Many experts believe that the eventual solution for sustainable energy is the use of direct solar energy as the main energy source. Among the options for renewable energy, photovoltaic technologies that harness solar energy offer a way to harness an unlimited resource and minimum environment impact in contrast with other alternatives such as water, nuclear, and wind energy. Currently, almost all commercial photovoltaic technologies use Si-based technology, which has a number of disadvantages including high cost, lack of flexibility, and the serious environmental impact of the Si industry. Other technologies, such as organic photovoltaic (OPV) cells, can overcome some of these issues. Today, polymer-based OPV (P-OPV) devices have achieved power conversion efficiencies (PCEs) that exceed 9%. Compared with P-OPV, small molecules based OPV (SM-OPV) offers further advantages, including a defined structure for more reproducible performance, higher mobility and open circuit voltage, and easier synthetic control that leads to more diversified structures. Therefore, while largely undeveloped, SM-OPV is an important emerging technology with performance comparable to P-OPV. In this Account, we summarize our recent results on solution-processed SM-OPV. We believe that solution processing is essential for taking full advantage of OPV technologies. Our work started with the synthesis of oligothiophene derivatives with an acceptor-donor-acceptor (A-D-A) structure. Both the backbone conjugation length and electron withdrawing terminal groups play an important role in the light absorption, energy levels and performance of the devices. Among those molecules, devices using a 7-thiophene-unit backbone and a 3-ethylrhodanine (RD) terminal unit produced a 6.1% PCE. With the optimized conjugation length and terminal unit, we borrowed from the results with P-OPV devices to optimize the backbone. Thus we

  12. Highly repeatable all-solid-state polarization-state generator

    NASA Astrophysics Data System (ADS)

    Yao, X. Steve; Yan, Lianshan; Shi, Yongqiang

    2005-06-01

    We report an all solid-state polarization-state generator that uses magneto-optic polarization rotators. The device can generate either five or six distinctive polarization states uniformly across a Poincaré sphere with repeatability better than 0.1°. It is ideal for polarization analysis, swept-wavelength measurement, and monitoring of polarization-related parameters and signal-to-noise ratios of optical networks.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

  14. Tomographic Reconstruction of Circularly Polarized High Harmonic Fields: 3D Attosecond Metrology

    NASA Astrophysics Data System (ADS)

    Chen, Cong; Tao, Zhensheng; Hernández-García, Carlos; Matyba, Piotr; Carr, Adra; Knut, Ronny; Kfir, Ofer; Zusin, Dimitry; Gentry, Christian; Grychtol, Patrick; Cohen, Oren; Plaja, Lius; Becker, Andreas; Jaron-Becker, Agnieszka; Kapteyn, Henry; Murnane, Margaret

    Bright, circularly polarized, extreme ultraviolet (EUV) and soft X-ray high harmonic beams can now be produced using counter-rotating circularly polarized driving laser fields. In the time domain, the field is predicted to emerge as a complex series of rotating linearly polarized bursts, varying rapidly in amplitude, frequency and polarization. Here, we extend attosecond metrology techniques to circularly polarized light for the first time by simultaneously irradiating a copper surface with circularly polarized high harmonic and linearly polarized infrared laser fields. The resulting temporal modulation of the photoelectron spectra carries essential phase information about the EUV field. Utilizing the polarization selectivity of the solid surface and by rotating the circularly polarized EUV field in space, we fully retrieve the amplitude and phase of the circularly polarized harmonics, allowing us to reconstruct one of the most complex coherent light fields produced to date.

  15. Highly polar spiroisoxazolines from the sponge Aplysina fulva.

    PubMed

    Rogers, Evan W; Molinski, Tadeusz F

    2007-07-01

    Two new highly polar brominated spiroisoxazolines, araplysillin N9-sulfamate (1) and an N-[5S,10R)-7,9-dibromo-10-hydroxy-8-methoxy-1-oxa-2-azaspiro[4.5]deca-2,6,8-triene-3-carboxy]-4-aminobutanoic acid (2), were isolated from a sample of Aplysina fulva collected in the Florida Keys. The absolute stereostructures of the new compounds were determined from analysis of MS, 1H and 13C NMR, and CD spectroscopy. Compound 2 provides a structural clue that may unify the biosynthesis of brominated spiroisoxazolines. PMID:17579462

  16. Polarization-dependent coupling between a polarization-independent high-index-contrast subwavelength grating and waveguides

    NASA Astrophysics Data System (ADS)

    Katayama, Takeo; Ito, Jun; Kawaguchi, Hitoshi

    2016-07-01

    We investigated the optical coupling between a polarization-independent high-index-contrast subwavelength grating (HCG) and two orthogonal in-plane waveguides. We fabricated the HCG with waveguides on a silicon-on-insulator substrate and demonstrated that a waveguide with a strong output is switched by changing the polarization of light injected into the HCG. The light coupled more strongly to the waveguide in the direction perpendicular to the polarization of the incident light than to that in the parallel direction. If this waveguide-coupled HCG is incorporated into a polarization bistable vertical-cavity surface-emitting laser (VCSEL), the output waveguide can be switched by changing the lasing polarization of the VCSEL.

  17. PVDF shock sensors: applications to polar materials and high explosives.

    PubMed

    Bauer, F

    2000-01-01

    Ferroelectric polymers (PVDF) with well-defined and precisely known electrical properties are now routinely available from commercial sources. Electrical processing with the Bauer cyclic poling method can produce individual films with well-defined remanent polarization up to 9 /spl mu/C/cm/sup 2/. These polymers provide an unusual opportunity to study the structure and physical properties of materials subjected to shock loading. The behavior of PVDF has been studied over a wide range of pressures using high-pressure shock loading and has yielded well-behaved, reproducible data up to 25 GPa in inert materials. The application of PVDF gauges for recording shock waves induced in polar materials such as Kel-F, PMMA, or in reactive materials is hampered by observations of anomalous responses due to shock-induced polarization or an electrical charge released inside a shock-compressed explosive. A solution using an appropriate electrical shielding has been identified and applied to PVDF for shock measurement studies of Kel-F, and for Hugoniot measurements of high explosives (PH). Furthermore, shock pressure profiles obtained with in situ PVDF gauges in porous HE (Formex) in a detonation regime have been achieved. Typical results of shock pressure profile versus time show a fast superpressure of a few nanoseconds followed by a pressure release down to a plateau level and then by a pressure decay. More accurate measurements are reported with electrically improved PVDF gauges as well as with 0.25 mm/sup 2/ active area PVDF gauges. PMID:18238691

  18. A method to polarize stored antiprotons to a high degree.

    PubMed

    Rathmann, F; Lenisa, P; Steffens, E; Contalbrigo, M; Dalpiaz, P F; Kacharava, A; Lehrach, A; Lorentz, B; Maier, R; Prasuhn, D; Ströher, H

    2005-01-14

    Polarized antiprotons can be produced in a storage ring by spin-dependent interaction in a purely electron-polarized hydrogen gas target. The polarizing process is based on spin transfer from the polarized electrons of the target atoms to the orbiting antiprotons. After spin filtering for about two beam lifetimes at energies T approximately equal 40-170 MeV using a dedicated large acceptance ring, the antiproton beam polarization would reach P=0.2-0.4. Polarized antiprotons would open new and unique research opportunities for spin-physics experiments in p(-) p interactions. PMID:15698088

  19. Highly specialized microbial diversity in hyper-arid polar desert

    PubMed Central

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

    2009-01-01

    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

  20. Molybdenum disulfide as a highly efficient adsorbent for non-polar gases.

    PubMed

    Yu, Ningning; Wang, Lu; Li, Min; Sun, Xiaotian; Hou, Tingjun; Li, Youyong

    2015-05-01

    Molybdenum disulfide (MoS2), a kind of graphene-like, two-dimensional material, has attracted great interest because of its unique properties and potential applications in electronics and sensors. In this paper, first-principle calculations and grand canonical Monte Carlo (GCMC) simulations are performed and used to show that the MoS2 layer is efficient at absorbing non-polar gases. Compared with the popular gas sorbents (metal organic frameworks and carbon-based materials), MoS2 has additional advantages, including large surface to volume ratio and tunable properties. The non-polar gas [carbon dioxide (CO2) and methane (CH4)] adsorption on the MoS2 layer with and without vacancies has been systematically studied. The perfect MoS2 shows little or no adsorption for CO2 and CH4 molecules, but the MoS2 with a single S vacancy and double S vacancies exhibits an excellent adsorption ability for CO2 and CH4 gases. The adsorption energies were 65 kJ mol(-1) for CO2 and 47 kJ mol(-1) for CH4 (van der Waals-D2), respectively. An orbital coupling between the p orbital of the CO2 (or CH4) molecule and the d orbital of the Mo atom was observed. GCMC simulation results show that MoS2 with a single S vacancy could absorb 42.1 wt% of CO2 and 37.6 wt% of CH4 under a pressure of 80 bar at room temperature. The results given in this paper indicate that monolayer MoS2 with defects is a highly efficient absorbent for non-polar gases. PMID:25865455

  1. On the dynamics of high Rydberg states of large molecules

    NASA Astrophysics Data System (ADS)

    Jortner, Joshua; Bixon, M.

    1995-04-01

    In this paper we explore the level structure, the optical excitation modes and the dynamics of a mixed Stark manifold of very high Rydberg states (with principal quantum numbers n=80-250) of large molecules, e.g., 1,4 diaza bicyclo [2,2,2] octane (DABCO) and bis (benzene) chromium (BBC) [U. Even, R. D. Levine, and R. Bersohn, J. Phys. Chem. 98, 3472 (1994)] and of autoionizing Rydbergs of atoms [F. Merkt, J. Chem. Phys. 100, 2623 (1994)], interrogated by time-resolved zero-electron kinetic energy (ZEKE) spectroscopy. We pursue the formal analogy between the level structure, accessibility and decay of very high Rydbergs in an external weak (F≂0.1-1 V cm-1) electric field and intramolecular (interstate and intrastate) relaxation in a bound molecular level structure. The onset n=nM of the strong mixing (in an external field F and in the field exerted by static ions) of a doorway state, which is characterized by a low azimuthal quantum number l, a finite quantum defect δ, and a total nonradiative width Γs≂Γ0/n3, with the inactive high l manifold is specified by nM≂80.6δ1/5(F/V cm-1)-1/5. At n≥nM the level structure and dynamics are characterized by the product γρ, where ρ is the density of states and γ=ΓsD(n) is the average decay width of the eigenstates, with the dilution factor D(n)≊n-2 for (lml) mixing and D(n)≂n-1 for (l) mixing, whereupon γρ=(Γ0/4δR)(nM/n)5, being independent of D(n). The sparse level structure is realized for γρ≪1, while the dense level structure prevails for γρ≳1, resulting in two limiting situations; (a) a dense limit for n≥nM and a sparse limit for n≫nM, and (b) a sparse limit for all n≥nM. The experimental information currently available on the decay dynamics of molecular (DABCO and BBC) and atomic (Ar) Rydbergs for n≥nM corresponds to case (b). The time-resolved dynamics was characterized in terms of the excited state total population probability P(t) and the population probability I(t) of the doorway

  2. High-Resolution Optical Tweezers for Single-Molecule Manipulation

    PubMed Central

    Zhang, Xinming; Ma, Lu; Zhang, Yongli

    2013-01-01

    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. PMID:24058311

  3. High pressure chemistry of red phosphorus by photoactivated simple molecules

    NASA Astrophysics Data System (ADS)

    Ceppatelli, Matteo; Bini, Roberto; Fanetti, Samuele; Caporali, Maria; Peruzzini, Maurizio

    2013-06-01

    High pressure (HP) is very effective in reducing intermolecular distances and inducing unexpected chemical reactions. In particular the photoactivation of the reactants in HP conditions can lead to very efficient and selective processes. The chemistry of phosphorus is currently based on the white molecular form. The red polymeric allotrope, despite more stable and much less toxic, has not attracted much attention so far. However, switching from the white to the red form would benefit any industrial procedure, especially from an environmental point of view. On the other side, water and ethanol are renewable, environmental friendly and largely available molecules, usable as reactants and photoactivators in HP conditions. Here we report a study on the HP photoinduced reactivity of red phosphorus with water and ethanol, showing the possibility of very efficient and selective processes, leading to molecular hydrogen and valuable phosphorus compounds. The reactions have been studied by means of FTIR and Raman spectroscopy and pressure has been generated using DAC and SAC. HP reactivity has been activated by the two-photon absorption of near-UV wavelengths and occured in total absence of solvents, catalysts and radical initiators, at room T and mild pressure conditions (0.2-1.5 GPa).

  4. Polarization Measurements in High-Energy Deuteron Photodisintegration

    SciTech Connect

    Adam Sarty; Andrei Afanasev; Arunava Saha; Bogdan Wojtsekhowski; Brendan Fox; C. Chang; Cathleen Jones; Charles Glashausser; Charles Perdrisat; Cornelis De Jager; Cornelis de Jager; D. Crovelli; Daniel Simon; David Meekins; Demetrius Margaziotis; Dipangkar Dutta; Edgar Kooijman; Edward Brash; Edward Kinney; Elaine Schulte; Eugene Chudakov; Feng Xiong; Franco Garibaldi; Garth Huber; Gerfried Kumbartzki; Guido Urciuoli; Haiyan Gao; James Kelly; Javier Gomez; Jens-Ole Hansen; Jian-Ping Chen; John Calarco; John LeRose; Jordan Hovdebo; Joseph Mitchell; Juncai Gao; Kamal Benslama; Kathy McCormick; Kevin Fissum; Konrad Aniol; Krishni Wijesooriya; Louis Bimbot; Ludyvine Morand; Luminita Todor; Marat Rvachev; Mark Jones; Martin Epstein; Meihua Liang; Michael Kuss; Moskov Amarian; Nilanga Liyanage; Oleksandr Glamazdin; Olivier Gayou; Paul Ulmer; Pete Markowitz; Peter Bosted; R. Holt; Riad Suleiman; Richard Lindgren; Rikki Roche; Robert Michaels; Roman Pomatsalyuk; Ronald Gilman; Ronald Ransome; Salvatore Frullani; Scott Dumalski; Seonho Choi; Sergey Malov; Sonja Dieterich; Steffen Strauch; Stephen Becher; Steve Churchwell; Ting Chang; Viktor Gorbenko; Vina Punjabi; Xiaodong Jiang; Zein-Eddine Meziani; Zhengwei Chai; Wang Xu

    2001-04-01

    We present measurements of the recoil proton polarization for the d(polarized y, polarized p)n reaction at thetac.m. = 90 degrees for photon energies up to 2.4 GeV. These are the first data in this reaction for polarization transfer with circularly polarized photons. The induced polarization py vanishes above 1 GeV, contrary to meson-baryon model expectations, in which resonances lead to large polarizations. However, the polarization transfer Cx does not vanish above 1 GeV, inconsistent with hadron helicity conservation. Thus, we show that the scaling behavior observed in the d(y,p)n cross sections is not a result of perturbative QCD. These data should provide important tests of new nonperturbative calculations in the intermediate energy regime.

  5. Ultra-wideband and high-efficiency polarization rotator based on metasurface

    NASA Astrophysics Data System (ADS)

    Jia, Yongtao; Liu, Ying; Zhang, Wenbo; Gong, Shuxi

    2016-08-01

    An ultra-wideband and high-efficiency polarization rotator based on a metasurface is proposed in this paper. The unit cell of the proposed polarization rotator consists of two pairs of L-shaped metallic patches printed on a substrate, which is backed by a metallic ground and covered by a superstrate. The superstrate is composed of a dielectric layer and a pair of L-shaped metallic patches printed on the dielectric layer. The proposed polarization rotator can rotate the polarization of linearly polarized electromagnetic (EM) wave to its orthogonal counterpart after reflection when the incident EM wave is y-/x-polarized. Simulated results show that the polarization rotator can perform 90° polarization rotation with very high efficiency at seven different frequencies and achieve a polarization conversion ratio higher than 0.9 in the frequency range of 7.8-34.7 GHz at normal incidence. Good agreement between the experimental results and simulated ones has been obtained.

  6. High thermopower of mechanically stretched single-molecule junctions

    PubMed Central

    Tsutsui, Makusu; Morikawa, Takanori; He, Yuhui; Arima, Akihide

    2015-01-01

    Metal-molecule-metal junction is a promising candidate for thermoelectric applications that utilizes quantum confinement effects in the chemically defined zero-dimensional atomic structure to achieve enhanced dimensionless figure of merit ZT. A key issue in this new class of thermoelectric nanomaterials is to clarify the sensitivity of thermoelectricity on the molecular junction configurations. Here we report simultaneous measurements of the thermoelectric voltage and conductance on Au-1,4-benzenedithiol (BDT)-Au junctions mechanically-stretched in-situ at sub-nanoscale. We obtained the average single-molecule conductance and thermopower of 0.01 G0 and 15 μV/K, respectively, suggesting charge transport through the highest occupied molecular orbital. Meanwhile, we found the single-molecule thermoelectric transport properties extremely-sensitive to the BDT bridge configurations, whereby manifesting the importance to design the electrode-molecule contact motifs for optimizing the thermoelectric performance of molecular junctions. PMID:26112999

  7. High thermopower of mechanically stretched single-molecule junctions.

    PubMed

    Tsutsui, Makusu; Morikawa, Takanori; He, Yuhui; Arima, Akihide; Taniguchi, Masateru

    2015-01-01

    Metal-molecule-metal junction is a promising candidate for thermoelectric applications that utilizes quantum confinement effects in the chemically defined zero-dimensional atomic structure to achieve enhanced dimensionless figure of merit ZT. A key issue in this new class of thermoelectric nanomaterials is to clarify the sensitivity of thermoelectricity on the molecular junction configurations. Here we report simultaneous measurements of the thermoelectric voltage and conductance on Au-1,4-benzenedithiol (BDT)-Au junctions mechanically-stretched in-situ at sub-nanoscale. We obtained the average single-molecule conductance and thermopower of 0.01 G0 and 15 μV/K, respectively, suggesting charge transport through the highest occupied molecular orbital. Meanwhile, we found the single-molecule thermoelectric transport properties extremely-sensitive to the BDT bridge configurations, whereby manifesting the importance to design the electrode-molecule contact motifs for optimizing the thermoelectric performance of molecular junctions. PMID:26112999

  8. Status of High Polarization DC High Voltage GaAs Photoguns

    SciTech Connect

    P. A. Adderley; J. Brittian; J. Clark; J. Grames; J. Hansknecht; J. McCarter; M. Poelker; M. L. Stutzman; R. Suleiman; K. E. L. Surles-Law

    2007-08-01

    This talk will review the state of the art of high polarization GaAs photoguns used worldwide. Subject matter will include drive laser technology, photocathode material, gun design, vacuum requirements and photocathode lifetime as a function of beam current. Recent results have demonstrated high current, 85% polarized beams with high reliability and long lifetime under operational conditions. Research initiatives for ensuring production of high average and peak current beams for future accelerator facilities such as ELIC and the ILC will be also discussed.

  9. Pulse-to-pulse polarization-switching method for high-repetition-rate lasers

    NASA Astrophysics Data System (ADS)

    Hahne, Steffen; Johnston, Benjamin F.; Withford, Michael J.

    2007-02-01

    We report a method that enables dynamic switching of the pulse-to-pulse linear polarization orientation of a high-pulse-rate laser. The implications for laser micromachining, where polarization direction can be important, are also discussed.

  10. High voltage processing of the SLC polarized electron gun

    SciTech Connect

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

    1993-04-01

    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.

  11. Moesin Interacts with the Cytoplasmic Region of Intercellular Adhesion Molecule-3 and Is Redistributed to the Uropod of T Lymphocytes during Cell Polarization

    PubMed Central

    Serrador, Juan M.; Alonso-Lebrero, José L.; Pozo, Miguel A. del; Furthmayr, Heinz; Schwartz-Albiez, Reinhard; Calvo, Javier; Lozano, Francisco; Sánchez-Madrid, Francisco

    1997-01-01

    During activation, T lymphocytes become motile cells, switching from a spherical to a polarized shape. Chemokines and other chemotactic cytokines induce lymphocyte polarization with the formation of a uropod in the rear pole, where the adhesion receptors intercellular adhesion molecule-1 (ICAM-1), ICAM-3, and CD44 redistribute. We have investigated membrane–cytoskeleton interactions that play a key role in the redistribution of adhesion receptors to the uropod. Immunofluorescence analysis showed that the ERM proteins radixin and moesin localized to the uropod of human T lymphoblasts treated with the chemokine RANTES (regulated on activation, normal T cell expressed, and secreted), a polarization-inducing agent; radixin colocalized with arrays of myosin II at the neck of the uropods, whereas moesin decorated the most distal part of the uropod and colocalized with ICAM-1, ICAM-3, and CD44 molecules. Two other cytoskeletal proteins, β-actin and α-tubulin, clustered at the cell leading edge and uropod, respectively, of polarized lymphocytes. Biochemical analysis showed that moesin coimmunoprecipitates with ICAM-3 in T lymphoblasts stimulated with either RANTES or the polarization- inducing anti–ICAM-3 HP2/19 mAb, as well as in the constitutively polarized T cell line HSB-2. In addition, moesin is associated with CD44, but not with ICAM-1, in polarized T lymphocytes. A correlation between the degree of moesin–ICAM-3 interaction and cell polarization was found as determined by immunofluorescence and immunoprecipitation analysis done in parallel. The moesin–ICAM-3 interaction was specifically mediated by the cytoplasmic domain of ICAM-3 as revealed by precipitation of moesin with a GST fusion protein containing the ICAM-3 cytoplasmic tail from metabolically labeled Jurkat T cell lysates. The interaction of moesin with ICAM-3 was greatly diminished when RANTES-stimulated T lymphoblasts were pretreated with the myosin-disrupting drug butanedione monoxime, which

  12. SLC polarized beam source ultra-high-vacuum design

    SciTech Connect

    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

    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.

  13. NCTM of liquids at high temperatures using polarization techniques

    NASA Technical Reports Server (NTRS)

    Krishnan, Shankar; Weber, J. K. Richard; Nordine, Paul C.; Schiffman, Robert A.

    1990-01-01

    Temperature measurement and control is extremely important in any materials processing application. However, conventional techniques for non-contact temperature measurement (mainly optical pyrometry) are very uncertain because of unknown or varying surface emittance. Optical properties like other properties change during processing. A dynamic, in-situ measurement of optical properties including the emittance is required. Intersonics is developing new technologies using polarized laser light scattering to determine surface emittance of freely radiating bodies concurrent with conventional optical pyrometry. These are sufficient to determine the true surface temperature of the target. Intersonics is currently developing a system called DAPP, the Division of Amplitude Polarimetric Pyrometer, that uses polarization information to measure the true thermodynamic temperature of freely radiating objects. This instrument has potential use in materials processing applications in ground and space based equipment. Results of thermophysical and thermodynamic measurements using laser reflection as a temperature measuring tool are presented. The impact of these techniques on thermophysical property measurements at high temperature is discussed.

  14. Distinguishing between aligned and randomly oriented polar molecules by using a combination of strong laser field with a weak static field

    NASA Astrophysics Data System (ADS)

    Moiseyev, Nimrod; Gupta, Ashish Kumar

    2012-08-01

    The harmonic generation spectra (HGS) of two different ensembles of the same heteronuclear (polar) diatomic molecule are studied. In one ensemble the molecules are aligned (i.e. CO ↔ OC) whereas in the second ensemble the molecules are randomly distributed in different directions (and therefore not all molecules have the same orientation, e.g. CO or OC along one of the axes in the laboratory frame). Using the non-Hermitian formalism of quantum mechanics we prove that the HGS of the two ensembles consist of odd-order harmonics only, provided the photo-induced dynamics is controlled by a single resonance (metastable) state. As we show here by using the Friedrich and Herschbach approach [J. Phys. Chem. A 103, 10280 (1999); J. Chem. Phys. 111, 6157 (1999)], it is possible to distinguish between the ensemble of 'perfectly' aligned molecules and an ensemble of molecules with a random directional distribution, provided the dc-field is turned on adiabatically slow and all aligned molecules are in the same quantum state. As an illustrative numerical example the HGS of aligned and ensemble of random directional distributed CO molecules with and without dc field were computed by carrying out ab initio electronic structure calculations.

  15. Generation of wavelength-tunable soliton molecules in a 2-μm ultrafast all-fiber laser based on nonlinear polarization evolution.

    PubMed

    Wang, Pan; Bao, Chengying; Fu, Bo; Xiao, Xiaosheng; Grelu, Philippe; Yang, Changxi

    2016-05-15

    We report on the experimental observation of stable single solitons and soliton molecules in a 2-μm thulium-holmium-doped fiber laser mode-locked through the nonlinear polarization evolution technique within an anomalously dispersive cavity. Single 0.65 nJ solitons feature a 7.3 nm spectral FWHM and 540 fs temporal duration, yielding a time-bandwidth product close to the Fourier-transform limitation. Under the same pumping power of 740 mW, stable out-of-phase twin-soliton molecules, featuring a temporal separation of 2.5 ps between the two ∼700  fs pulses, are generated in a deterministic way, while the central wavelength of the soliton molecules can be tuned from 1920 to 1940 nm. Finally, we present strong experimental evidence of vibrating soliton molecules. PMID:27176976

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

    NASA Astrophysics Data System (ADS)

    Dundas, Daniel

    2012-05-01

    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 N2 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 N2 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.

  17. Fabrication of AIN Nano-Structures Using Polarity Control by High Temperature Metalorganic Chemical Vapor Deposition.

    PubMed

    Eom, Daeyong; Kim, Jinwan; Lee, Kyungjae; Jeon, Minhwan; Heo, Cheon; Pyeon, Jaedo; Nam, Okhyun

    2015-07-01

    This study investigates the crystallographic polarity transition of AIN layers grown by high temperature metalorganic chemical vapor deposition (HT-MOCVD), with varying trimethylaluminum (TMAI) pre-flow rates. AIN layers grown without TMAI pre-flow had a mixed polarity, consisting of Al- and N-polarity, and exhibited a rough surface. With an increasing rate of TMAI pre-flow, the AIN layer was changed to an Al-polarity, with a smooth surface morphology. Finally, AIN nano-pillars and nano-rods of Al-polarity were fabricated by etching a mixed polarity AIN layer using an aqueous KOH solution. PMID:26373093

  18. Dissociation energies of some high temperature molecules containing aluminum

    NASA Technical Reports Server (NTRS)

    Stearns, C. A.; Kohl, F. J.

    1972-01-01

    The Knudsen cell mass spectrometric method has been used to investigate the gaseous molecules Al2, AlSi,AlSiO, AlC2, Al2C2, and AlAuC2. Special attention was given to the experimental considerations and techniques needed to identify and to measure ion intensities for very low abundance molecular species. Second- and third-law procedures were used to obtain reaction enthalpies for pressure calibration independent and isomolecular exchange reactions. Dissociation energies for the molecules were derived from the measured ion intensities, free-energy functions obtained from estimated molecular constants, and auxiliary thermodynamic data. The bonding and stability of these aluminum containing molecules are compared with other similar species.

  19. Topical Developments in High-Field Dynamic Nuclear Polarization

    PubMed Central

    Kiesewetter, Matthew K.; Frantz, Derik K.; Walish, Joseph J.; Ravera, Enrico; Luchinat, Claudio; Swager, Timothy M.; Griffin, Robert G.

    2015-01-01

    We report our recent efforts directed at improving high-field DNP experiments. We investigated a series of thiourea nitroxide radicals and the associated DNP enhancements ranging from ε = 25 to 82 that demonstrate the impact of molecular structure on performance. We directly polarized low-gamma nuclei including 13C, 2H, and 17O using trityl via the cross effect. We discuss a variety of sample preparation techniques for DNP with emphasis on the benefit of methods that do not use a glass-forming cryoprotecting matrix. Lastly, we describe a corrugated waveguide for use in a 700 MHz / 460 GHz DNP system that improves microwave delivery and increases enhancements up to 50%. PMID:25977588

  20. Polarization gating of high harmonic generation in the water window

    NASA Astrophysics Data System (ADS)

    Li, Jie; Ren, Xiaoming; Yin, Yanchun; Cheng, Yan; Cunningham, Eric; Wu, Yi; Chang, Zenghu

    2016-06-01

    We implement the polarization gating (PG) technique with a two-cycle, 1.7 μm driving field to generate an attosecond supercontinuum extending to the water window spectral region. The ellipticity dependence of the high harmonic yield over a photon energy range much broader than previous work is measured and compared with a semi-classical model. When PG is applied, the carrier-envelope phase (CEP) is swept to study its influence on the continuum generation. PG with one-cycle (5.7 fs) and two-cycle (11.3 fs) delay are tested, and both give continuous spectra spanning from 50 to 450 eV under certain CEP values, strongly indicating the generation of isolated attosecond pulses in the water window region.

  1. High performance small-molecule organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Kuo, Chung-Chen

    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

  2. Spectroscopic and dynamical studies of highly energized small polyatomic molecules

    SciTech Connect

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

    1990-01-01

    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.

  3. Highly polarized light emission by isotropic quantum dots integrated with magnetically aligned segmented nanowires

    SciTech Connect

    Uran, Can; Erdem, Talha; Guzelturk, Burak; Perkgöz, Nihan Kosku; Jun, Shinae; Jang, Eunjoo; Demir, Hilmi Volkan

    2014-10-06

    In this work, we demonstrate a proof-of-concept system for generating highly polarized light from colloidal quantum dots (QDs) coupled with magnetically aligned segmented Au/Ni/Au nanowires (NWs). Optical characterizations reveal that the optimized QD-NW coupled structures emit highly polarized light with an s-to p-polarization (s/p) contrast as high as 15:1 corresponding to a degree of polarization of 0.88. These experimental results are supported by the finite-difference time-domain simulations, which demonstrate the interplay between the inter-NW distance and the degree of polarization.

  4. POLARIZED ION SOURCES FOR HIGH ENERGY ACCELERATORS AND COLLIDERS

    SciTech Connect

    ZELENSKI,A.N.

    2000-10-16

    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.

  5. POLARIZED ION SOURCES FOR HIGH ENERGY ACCELERATORS AND COLLIDERS

    SciTech Connect

    ZELENSKI,A.N.

    2000-10-16

    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.

  6. Lunar Crater Interiors with High Circular Polarization Signatures

    NASA Astrophysics Data System (ADS)

    Weitz, C. M.; Campbell, B. A.; Morgan, G.

    2015-12-01

    We analyzed 12.6-cm Earth-based radar images of the Moon to search for older craters (pre-Copernican) that display high values of the circular polarization ratio (CPR) on their interior walls. These craters have highly eroded rims and ejecta, indicating that there must be a source exposed within the crater interior that is continuously creating a rougher surface. Of particular interest are craters between 10-25 km in diameter that occur in smooth plains in the highlands, where competent layers are not expected as they are for the mare. After identifying these high-CPR interiors in pre-Copernican craters, we studied LROC NAC and Kaguya TC images to search for possible albedo and layering on crater interior walls that might signal the presence of anomalous material. Our results indicate that high-CPR craters generally have boulder fields clustered around their upper interior walls. We divide the high-CPR craters into three types: (1) craters on the layered mare lava flows; (2) craters in the highlands that correlate to mapped locations of smooth plains; and (3) craters on the highlands that are not associated with smooth plains. Most of the high-CPR craters in the highlands are associated with Eratosthenian-period craters, and most of these are also on smooth plains, indicating that impact melt sheets are a likely source for the boulders exposed on their interior walls. Statistical analyses will be performed after incorporating multiple lunar datasets into GIS to quantify these preliminary interpretations. Figure 1. Example of high-CPR crater Zagut A located on smooth plains in the highlands. LROC images showing boulders on (a) northern crater interior wall and (b) southern crater interior wall. (c) Stronlgy enhanced values of CPR are observed for the interior of Zagut A.

  7. High-throughput multispot single-molecule spectroscopy

    PubMed Central

    Colyer, Ryan A.; Scalia, Giuseppe; Kim, Taiho; Rech, Ivan; Resnati, Daniele; Marangoni, Stefano; Ghioni, Massimo; Cova, Sergio; Weiss, Shimon; Michalet, Xavier

    2011-01-01

    Solution-based single-molecule spectroscopy and fluorescence correlation spectroscopy (FCS) are powerful techniques to access a variety of molecular properties such as size, brightness, conformation, and binding constants. However, this is limited to low concentrations, which results in long acquisition times in order to achieve good statistical accuracy. Data can be acquired more quickly by using parallelization. We present a new approach using a multispot excitation and detection geometry made possible by the combination of three powerful new technologies: (i) a liquid crystal spatial light modulator to produce multiple diffraction-limited excitation spots; (ii) a multipixel detector array matching the excitation pattern and (iii) a low-cost reconfigurable multichannel counting board. We demonstrate the capabilities of this technique by reporting FCS measurements of various calibrated samples as well as single-molecule burst measurements. PMID:21643532

  8. Submillimeterwave Spectroscopy of Highly Astrophysical Interest Molecule: Hydroxyacetonitrile

    NASA Astrophysics Data System (ADS)

    Margules, L.; Motiyenko, R. A.; Guillemin, J.-C.

    2013-06-01

    Hydroxyacetonitrile is a simple derivative of methanol. This molecule has a strong astrophysical interest. In astrophysical environment, the formation of hydroxyacetonitrile (HOCH_2CN), has been shown to compete with aminomethanol (NH_2CH_2OH), a glycine precursor, through the Strecker synthesis, in addition its photochemistry leads to the formation of formylcyanide (CHOCN), ketenimine (CH_2CNH), formaldehyde (CH_2O), hydrogen cyanide (HCN), carbon monoxyde (CO). Its detection in the ISM will provide crucial hints in the formation process of complex organic molecules. The lack of data about this molecule, only studied up to 50 GHz, is mainly due to two reasons. First, this is not commercially available, the synthesis should be perform. Second, the most stable conformer is the gauche one. This exhibits large amplitude motion due to the two equivalent configurations possible. Due to tunneling effect, each level is split into 0^+ and 0^- substates. This makes the analysis of the spectra delicate. We will report here the very first results obtained. This work was supported by the CNES and the Action sur Projets de l'INSU, PCMI. Danger, G. et al.ApJ {756}, (2012) 11 Danger, G. et al.A&A {549}, (2012) A93 Cazzoli, G. et al.J. Chem. Soc., Faraday Trans. 2 {69}, (1973) 569

  9. A high-pressure polarized 3He gas target for nuclear-physics experiments using a polarized photon beam

    NASA Astrophysics Data System (ADS)

    Ye, Q.; Laskaris, G.; Chen, W.; Gao, H.; Zheng, W.; Zong, X.; Averett, T.; Cates, G. D.; Tobias, W. A.

    2010-04-01

    Following the first experiment on three-body photodisintegration of polarized 3He utilizing circularly polarized photons from High-Intensity Gamma Source (HI γ S) at Duke Free Electron Laser Laboratory (DFELL), a new high-pressure polarized 3He target cell made of pyrex glass coated with a thin layer of sol-gel doped with aluminum nitrate nonahydrate has been built in order to reduce the photon beam-induced background. The target is based on the technique of spin exchange optical pumping of hybrid rubidium and potassium and the highest polarization achieved is ˜ 62% determined from both NMR-AFP and EPR polarimetries. The phenomenological parameter that reflects the additional unknown spin relaxation processes, X , is estimated to be ˜ 0.10 and the performance of the target is in good agreement with theoretical predictions. We also present beam test results from this new target cell and the comparison with the GE180 3He target cell used previously at HI γ S. This is the first time that the sol-gel coating technique has been used in a polarized 3He target for nuclear-physics experiments.

  10. Complexity of H-bonding between polar molecules on Si(100)-2 × 1 and Ge(100)-2 × 1 surfaces

    NASA Astrophysics Data System (ADS)

    Huang, Xiang; Tian, Ren-Yu; Yang, Xiao-Bao; Zhao, Yu-Jun

    2016-09-01

    The adsorption of various combinations of three polar molecules (NH3, H2O, and HF) on Si/Ge(100) surface is studied by first-principles calculations. On a given pre-adsorbed substrate, the H-bonding and dative bonding always show a synergistic effect, together with the electrostatic attraction, dominating the adsorption and dissociation of polar molecules on Si/Ge(100). Both H2O and HF are found to be energetically favored to cluster with the pre-adsorbed H2O molecule on Si/Ge(100) surface. Catalyzed by H2O, the dissociation barriers of H2O on Ge(100) decrease from ~ 0.7 to ~ 0.4 eV, in comparison with the nearly an order of magnitude reduction on Si(100). Furthermore, H2O molecule dissociates spontaneously on Si(100) and the barriers are lowered to ~ 0.2 eV on Ge(100) when catalyzed by HF, providing an efficient approach for dissociation of H2O on Si(100) and Ge(100) surfaces.

  11. Calamitic Smectic A-Polar Smectic APA Transition Observed in Bent Molecules with Large Bent-Angle Central Core of 4,6-Dichlorobenzene and Alkylthio Terminal Tail

    NASA Astrophysics Data System (ADS)

    Nguyen, Ha; Kang, Sungmin; Tokita, Masatoshi; Watanabe, Junji

    2011-07-01

    New homologs of bent molecules with a large bent-angle central core of 4,6-dichloro benzene and an alkylthio terminal tail have been synthesized. Although the corresponding alkoxy-tail homologs show only the calamitic phases because of its large bent angles around 160°, the new homologs with an alkylthio tail exhibit the antiferroelectric smectic APA (SmAPA) banana phase that is transformed on cooling from the calamitic smectic A (SmA) phase. The biaxial polar packing of bent molecules in the SmAPA phase is considered to arise from the hindered rotation around the molecular long axis due to the expansion of the mesophase temperatures to a lower temperature region. This study indicates that the bent molecules, even with a large bent angle, have the potential to form a switchable banana phase with a remarkable decrease in its phase temperature range to around 60 °C.

  12. Vibrationally highly excited molecules and intramolecular mode coupling through high-overtone spectroscopy

    SciTech Connect

    Wong, J.S.; Moore, C.B.

    1981-08-01

    High overtone spectra of organic molecules can be interpreted using the local mode model for absorptions by the inequivalent C-H bonds. The spectra can be assigned using either observed C-H bond lengths or isolated fundamental frequencies. The spectra of trihalomethanes indicate that the dominant intramolecular mode coupling for the C-H stretching overtones is Fermi resonance with combination states with one less C-H stretching quantum plus two quanta of the C-H bending vibrations.

  13. Enhancing the intestinal absorption of molecules containing the polar guanidino functionality: a double-targeted prodrug approach

    PubMed Central

    Sun, Jing; Dahan, Arik; Amidon, Gordon L.

    2011-01-01

    A prodrug strategy was applied to guanidino-containing analogs to increase oral absorption via hPEPT1 and hVACVase. L-Valine, L-isoleucine and L-phenylalanine esters of [3-(hydroxymethyl)phenyl]guanidine (3-HPG) were synthesized and evaluated for transport and activation. In HeLa/hPEPT1 cells, Val-3-HPG and Ile-3-HPG exhibited high affinity to hPEPT1 (IC50: 0.65 and 0.63 mM, respectively), and all three L-amino acid esters showed higher uptake (2.6- to 9-fold) than the parent compound 3-HPG. Val-3-HPG and Ile-3-HPG demonstrated remarkable Caco-2 permeability enhancement, and Val-3-HPG exhibited comparable permeability to valacyclovir. In rat perfusion studies, Val-3-HPG and Ile-3-HPG permeabilities were significantly higher than 3-HPG, and exceeded/matched the high-permeability standard metoprolol, respectively. All the L-amino acid 3-HPG esters were effectively activated in HeLa and Caco-2 cell homogenates, and were found to be good substrates of hVACVase (kcat/Km in mM−1·s−1: Val-3-HPG, 3370; Ile-3-HPG, 1580; Phe-3-HPG, 1660). In conclusion, a prodrug strategy is effective at increasing the intestinal permeability of polar guanidino analogs via targeting hPEPT1 for transport and hVACVase for activation. PMID:19957998

  14. Polarization Transfer in Proton Compton Scattering at High Momentum Transfer

    SciTech Connect

    Hamilton, D.J.; Annand, J.R.M.; Mamyan, V.H.; Aniol, K.A.; Margaziotis, D.J.; Bertin, P.Y.; Camsonne, A.; Laveissiere, G.; Bosted, P.; Paschke, K.; Calarco, J.R.; Chang, G.C.; Horn, T.; Savvinov, N.; Chang, T.-H.; Danagoulian, A.; Nathan, A.M.; Roedelbronn, M.; Chen, J.-P.

    2005-06-24

    Compton scattering from the proton was investigated at s=6.9 GeV{sup 2} and t=-4.0 GeV{sup 2} 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 mechanism in which the photon interacts with a single quark carrying the spin of the proton.

  15. Polarization Transfer in Proton Compton Scattering at High Momentum Transfer

    SciTech Connect

    D.J. Hamilton; Vahe Mamyan

    2004-10-01

    Compton scattering from the proton was investigated at s = 6.9 GeV{sup 2} and t = -4.0 TeV{sup 2} via polarization transfer from circularly polarized incident photons. The longitudinal and transverse components of the recoil proton polarization were measured. The results are in excellent agreement with a prediction based on a reaction mechanism in which the photon interacts with a single quark carrying the spin of the proton and in disagreement with a prediction of pQCD based on a two-gluon exchange mechanism.

  16. Effectiveness of organic molecules for spin filtering in an organic spin valve: Reaction-induced spin polarization for Co atop Alq 3

    NASA Astrophysics Data System (ADS)

    Lam, Tu-Ngoc; Lai, Yu-Ling; Chen, Chih-Han; Chen, Po-Hung; Chan, Yuet-Loy; Wei, Der-Hsin; Lin, Hong-Ji; Chen, C. T.; Wang, Jeng-Han; Sheu, Jeng-Tzong; Hsu, Yao-Jane

    2015-01-01

    The spin polarization of organic-ferromagnetic interfaces in an organic spin valve critically affects the efficiency of spin injection or detection. We examined the chemical and electronic properties of ferromagnetic Co deposited on organic Al q3 and the interfacial spin-polarized capability of the electronic states. Our x-ray photoemission spectra and calculations with density-functional theory indicate a sequential and unequal distribution of charge from Co clusters to N and then to O atoms in Al q3 . The preferential orbital hybridization at specific functional sites produces efficient spin polarization of organic molecules. Element-specific measurements of x-ray magnetic circular dichroism demonstrate the preferential spin polarization in the lowest unoccupied molecular orbital state of N atoms at the complex interface for Co atop Al q3 , which agrees satisfactorily with calculation. Our results indicate that an induced interfacial spin polarization on engineering the dominant reaction of Co with mainly N and O atoms in Al q3 might pave a way for effective spin filtering in organic spintronics.

  17. Spectroscopic and dynamical studies of highly energized small polyatomic molecules

    SciTech Connect

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

    1993-12-01

    The authors have initiated a program to perform spectroscopic and dynamic studies of small molecules. Large amplitude motions in excited acetylene were discussed along with plans to record the dispersed fluorescence (DF) and the stimulated emission pumping (SEP) spectra. SEP spectra were reported for the formyl radical. A Fourier transform spectrometer was discussed with respect to its ability to probe the structure of radicals. This instrument is capable of performing studies using various techniques such as magnetic rotation spectroscopy and sub-Doppler sideband-OODR Zeman (SOODRZ) spectroscopy.

  18. Highly anisotropic metasurface: a polarized beam splitter and hologram

    PubMed Central

    Zheng, Jun; Ye, Zhi-Cheng; Sun, Nan-Ling; Zhang, Rui; Sheng, Zheng-Ming; Shieh, Han-Ping D.; Zhang, Jie

    2014-01-01

    Two-dimensional metasurface structures have recently been proposed to reduce the challenges of fabrication of traditional plasmonic metamaterials. However, complex designs and sophisticated fabrication procedures are still required. Here, we present a unique one-dimensional (1-D) metasurface based on bilayered metallic nanowire gratings, which behaves as an ideal polarized beam splitter, producing strong negative reflection for transverse-magnetic (TM) light and efficient reflection for transverse-electric (TE) light. The large anisotropy resulting from this TE-metal-like/TM-dielectric-like feature can be explained by the dispersion curve based on the Bloch theory of periodic metal-insulator-metal waveguides. The results indicate that this photon manipulation mechanism is fundamentally different from those previously proposed for 2-D or 3-D metastructures. Based on this new material platform, a novel form of metasurface holography is proposed and demonstrated, in which an image can only be reconstructed by using a TM light beam. By reducing the metamaterial structures to 1-D, our metasurface beam splitter exhibits the qualities of cost-efficient fabrication, robust performance, and high tunability, in addition to its applicability over a wide range of working wavelengths and incident angles. This development paves a foundation for metasurface structure designs towards practical metamaterial applications. PMID:25262791

  19. Highly anisotropic metasurface: a polarized beam splitter and hologram.

    PubMed

    Zheng, Jun; Ye, Zhi-Cheng; Sun, Nan-Ling; Zhang, Rui; Sheng, Zheng-Ming; Shieh, Han-Ping D; Zhang, Jie

    2014-01-01

    Two-dimensional metasurface structures have recently been proposed to reduce the challenges of fabrication of traditional plasmonic metamaterials. However, complex designs and sophisticated fabrication procedures are still required. Here, we present a unique one-dimensional (1-D) metasurface based on bilayered metallic nanowire gratings, which behaves as an ideal polarized beam splitter, producing strong negative reflection for transverse-magnetic (TM) light and efficient reflection for transverse-electric (TE) light. The large anisotropy resulting from this TE-metal-like/TM-dielectric-like feature can be explained by the dispersion curve based on the Bloch theory of periodic metal-insulator-metal waveguides. The results indicate that this photon manipulation mechanism is fundamentally different from those previously proposed for 2-D or 3-D metastructures. Based on this new material platform, a novel form of metasurface holography is proposed and demonstrated, in which an image can only be reconstructed by using a TM light beam. By reducing the metamaterial structures to 1-D, our metasurface beam splitter exhibits the qualities of cost-efficient fabrication, robust performance, and high tunability, in addition to its applicability over a wide range of working wavelengths and incident angles. This development paves a foundation for metasurface structure designs towards practical metamaterial applications. PMID:25262791

  20. Polar Kerr effect in high temperature cuprate superconductors

    NASA Astrophysics Data System (ADS)

    Tewari, Sumanta; Sharma, Girish; Goswami, Pallab; Yakovenko, Victor; Chakravarty, Sudip

    A mechanism is proposed for the tantalizing evidence of polar Kerr effect in a class of high temperature superconductors-the signs of the Kerr angle from two opposite faces of the same sample are identical and magnetic field training is non-existent. The mechanism does not break global time reversal symmetry, as in an antiferromagnet, and results in zero Faraday effect. It is best understood in a phenomenological model of bilayer cuprates, such as YBCO, in which intra-bilayer tunneling nucleates a chiral d-density wave such that the individual layers have opposite chirality. Although the presentation is specific to the chiral d-density wave, the mechanism may be more general to any quasi-two-dimensional orbital antiferromagnet in which time reversal symmetry is broken in each plane, but not when averaged macroscopically. St and GS supported by AFOSR (FA9550-13-1-0045), PG supported by JQI-NSF-PFC, SC supported by NSF-DMR-1004520.

  1. Evaluation of Small Molecules as Front Cell Donor Materials for High-Efficiency Tandem Solar Cells.

    PubMed

    Zhang, Qian; Wan, Xiangjian; Liu, Feng; Kan, Bin; Li, Miaomiao; Feng, Huanran; Zhang, Hongtao; Russell, Thomas P; Chen, Yongsheng

    2016-08-01

    Three small molecules as front cell donors for tandem cells are thoroughly evaluated and a high power conversion efficiency of 11.47% is achieved, which demonstrates that the oligomer-like small molecules offer a good choice for high-performance tandem solar cells. PMID:27214707

  2. Highly precise and accurate terahertz polarization measurements based on electro-optic sampling with polarization modulation of probe pulses.

    PubMed

    Nemoto, Natsuki; Higuchi, Takuya; Kanda, Natsuki; Konishi, Kuniaki; Kuwata-Gonokami, Makoto

    2014-07-28

    We have developed an electro-optic (EO) sampling method with polarization modulation of probe pulses; this method allows us to measure the direction of a terahertz (THz) electric-field vector with a precision of 0.1 mrad in a data acquisition time of 660 ms using a 14.0-kHz repetition rate pulsed light source. Through combination with a THz time-domain spectroscopy technique, a time-dependent two-dimensional THz electric field was obtained. We used a photoelastic modulator for probe-polarization modulation and a (111)-oriented zincblende crystal as the EO crystal. Using the tilted pulse front excitation method with stable regeneratively amplified pulses, we prepared stable and intense THz pulses and performed pulse-by-pulse analog-to-digital conversion of the signals. These techniques significantly reduced statistical errors and enabled sub-mrad THz polarization measurements. We examined the performance of this method by measuring a wire-grid polarizer as a sample. The present method will open a new frontier of high-precision THz polarization sensitive measurements. PMID:25089412

  3. High-Order Interference Effect Introduced by Polarization Mode Coupling in Polarization--Maintaining Fiber and Its Identification.

    PubMed

    Li, Chuang; Yang, Jun; Yu, Zhangjun; Yuan, Yonggui; Zhang, Jianzhong; Wu, Bing; Peng, Feng; Yuan, Libo

    2016-01-01

    The high-order interference (HOI)-The interferogram introduced by polarization mode couplings (PMC) of multiple perturbations-Will cause misjudgment of the realistic coupling points in polarization-maintaining fiber (PMF) which is tested with a white light interferometer (WLI) with large dynamic range. We present an optical path tracking (OPT) method for simplifying the analysis of HOI, and demonstrate the enhancement and suppression conditions for the HOIs. A strategy is proposed to readily identify HOI by altering the spliced angle between polarizers' pigtails and the PMF under test. Moreover, a PMF experiment with two perturbation points, for simplicity, is given as an example. As a result, all the characteristic interferograms including HOIs can be distinguished through just four measurements. Utilizing this identification method, we can estimate the realistic coupling points in PMFs and distinguish them from the interference signals including numerous HOIs. PMID:27011191

  4. High Power Dynamic Polarization Control Using Plasma Photonics

    NASA Astrophysics Data System (ADS)

    Turnbull, D.; Michel, P.; Chapman, T.; Tubman, E.; Pollock, B. B.; Chen, C. Y.; Goyon, C.; Ross, J. S.; Divol, L.; Woolsey, N.; Moody, J. D.

    2016-05-01

    We report the first experimental demonstration of a plasma wave plate based on laser-induced birefringence. An elliptically polarized input was converted into a nearly ideal circularly polarized beam using an optical system composed of a second laser beam and a plasma. The results are in excellent agreement with linear theory and three-dimensional simulations up to phase delays exceeding π /4 , thus establishing the feasibility of laser-plasma photonic devices that are ultrafast, damage-resistant, and easily tunable.

  5. Mapping the electrostatic force field of single molecules from high-resolution scanning probe images

    NASA Astrophysics Data System (ADS)

    Hapala, Prokop; Švec, Martin; Stetsovych, Oleksandr; van der Heijden, Nadine J.; Ondráček, Martin; van der Lit, Joost; Mutombo, Pingo; Swart, Ingmar; Jelínek, Pavel

    2016-05-01

    How electronic charge is distributed over a molecule determines to a large extent its chemical properties. Here, we demonstrate how the electrostatic force field, originating from the inhomogeneous charge distribution in a molecule, can be measured with submolecular resolution. We exploit the fact that distortions typically observed in high-resolution atomic force microscopy images are for a significant part caused by the electrostatic force acting between charges of the tip and the molecule of interest. By finding a geometrical transformation between two high-resolution AFM images acquired with two different tips, the electrostatic force field or potential over individual molecules and self-assemblies thereof can be reconstructed with submolecular resolution.

  6. Highly conductive single-molecule wires with controlled orientation by coordination of metalloporphyrins.

    PubMed

    Aragonès, Albert C; Darwish, Nadim; Saletra, Wojciech J; Pérez-García, Lluïsa; Sanz, Fausto; Puigmartí-Luis, Josep; Amabilino, David B; Díez-Pérez, Ismael

    2014-08-13

    Porphyrin-based molecular wires are promising candidates for nanoelectronic and photovoltaic devices due to the porphyrin chemical stability and unique optoelectronic properties. An important aim toward exploiting single porphyrin molecules in nanoscale devices is to possess the ability to control the electrical pathways across them. Herein, we demonstrate a method to build single-molecule wires with metalloporphyrins via their central metal ion by chemically modifying both an STM tip and surface electrodes with pyridin-4-yl-methanethiol, a molecule that has strong affinity for coordination with the metal ion of the porphyrin. The new flat configuration resulted in single-molecule junctions of exceedingly high lifetime and of conductance 3 orders of magnitude larger than that obtained previously for similar porphyrin molecules but wired from either end of the porphyrin ring. This work presents a new concept of building highly efficient single-molecule electrical contacts by exploiting metal coordination chemistry. PMID:24978587

  7. High-Throughput Single-Molecule Studies of Protein-DNA Interactions

    PubMed Central

    Robison, Aaron D.; Finkelstein, Ilya J.

    2014-01-01

    Fluorescence and force-based single-molecule studies of protein-nucleic acid interactions continue to shed critical insights into many aspects of DNA and RNA processing. As single-molecule assays are inherently low-throughput, obtaining statistically relevant datasets remains a major challenge. Additionally, most fluorescence-based single-molecule particle-tracking assays are limited to observing fluorescent proteins that are in the low-nanomolar range, as spurious background signals predominate at higher fluorophore concentrations. These technical limitations have traditionally limited the types of questions that could be addressed via single-molecule methods. In this review, we describe new approaches for high-throughput and high-concentration single-molecule biochemical studies. We conclude with a discussion of outstanding challenges for the single-molecule biologist and how these challenges can be tackled to further approach the biochemical complexity of the cell. PMID:24859086

  8. Polarization effects in low-energy electron scattering from silane molecules in an exact static-exchange model

    SciTech Connect

    Jain, A. )

    1991-07-01

    We have investigated the effects of various model polarization potentials in low-energy (below 15 eV) electron-SiH{sub 4} collisions in which electron-exchange correlation is treated exactly via an iterative procedure. Two models of the parameter-free polarization potential are employed; one, the {ital V}{sub pol}{sup JT} potential, introduced by Jain and Thompson (J. Phys. B 15, L631 (1982)), is based on the polarized-orbital theory; the other, the correlation-polarization potential {ital V}{sub pol}{sup CP}, first proposed by O'Connel and Lane (Phys. Rev. A 27, 1893 (1983)), is given as a density functional. In this low-energy region, the differential as well as integral cross sections are greatly influenced by such short-range-correlation and long-range-polarization interactions. We found that a local parameter-free model to mimic charge-distortion effects is quite successful if it is determined under the polarized-orbital-type approach rather than based on density-functional theory.

  9. Highly stable polarization independent Mach-Zehnder interferometer

    SciTech Connect

    Mičuda, Michal Doláková, Ester; Straka, Ivo; Miková, Martina; Dušek, Miloslav; Fiurášek, Jaromír; Ježek, Miroslav

    2014-08-15

    We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27×40 cm offers individually accessible paths and shows phase deviation less than 0.4° during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3° or 7 nm for 1.5 h without any active stabilization. The polarization insensitive design is verified by measuring interference visibility as a function of input polarization. For both interferometer's output ports and all tested polarization states the visibility stays above 93%. The discrepancy in visibility for horizontal and vertical polarization about 3.5% is caused mainly by undesired polarization dependence of splitting ratio of the beam splitter used. The presented interferometer device is suitable for quantum-information and other sensitive applications where active stabilization is complicated and common-mode interferometer is not an option as both the interferometer arms have to be accessible individually.

  10. Highly stable polarization independent Mach-Zehnder interferometer.

    PubMed

    Mičuda, Michal; Doláková, Ester; Straka, Ivo; Miková, Martina; Dušek, Miloslav; Fiurášek, Jaromír; Ježek, Miroslav

    2014-08-01

    We experimentally demonstrate optical Mach-Zehnder interferometer utilizing displaced Sagnac configuration to enhance its phase stability. The interferometer with footprint of 27×40 cm offers individually accessible paths and shows phase deviation less than 0.4° during a 250 s long measurement. The phase drift, evaluated by means of Allan deviation, stays below 3° or 7 nm for 1.5 h without any active stabilization. The polarization insensitive design is verified by measuring interference visibility as a function of input polarization. For both interferometer's output ports and all tested polarization states the visibility stays above 93%. The discrepancy in visibility for horizontal and vertical polarization about 3.5% is caused mainly by undesired polarization dependence of splitting ratio of the beam splitter used. The presented interferometer device is suitable for quantum-information and other sensitive applications where active stabilization is complicated and common-mode interferometer is not an option as both the interferometer arms have to be accessible individually. PMID:25173242

  11. Dual-band high-efficiency polarization converter using an anisotropic metasurface

    NASA Astrophysics Data System (ADS)

    Lin, Baoqin; Wang, Buhong; Meng, Wen; Da, Xinyu; Li, Wei; Fang, Yingwu; Zhu, Zihang

    2016-05-01

    In this work, a dual-band and high-efficiency reflective cross-polarization converter based on an anisotropic metasurface for linearly polarized electromagnetic waves is proposed. Its unit cell is composed of an elliptical disk-ring mounted on grounded dielectric substrate, which is an anisotropic structure with a pair of mutually perpendicular symmetric axes u and v along ± 45 ° directions with respect to y-axis direction. Both the simulation and measured results show that the polarization converter can convert x- or y-polarized incident wave to its cross polarized wave in the two frequency bands (6.99-9.18 GHz, 11.66-20.40 GHz) with the conversion efficiency higher than 90%; moreover, the higher frequency band is an ultra-wide one with a relative bandwidth of 54.5% for multiple plasmon resonances. In addition, we present a detailed analysis for the polarization conversion of the polarization converter, and derive a formula to calculate the cross- and co-polarization reflections at y-polarized incidence according to the phase differences between the two reflected coefficients at u-polarized and v-polarized incidences. The simulated, calculated, and measured results are all in agreement with the entire frequency regions.

  12. Intrinsic Differences in the Inner Jets of High and Low Optically Polarized Radio Quasars

    NASA Technical Reports Server (NTRS)

    Lister, M.; Smith, P.

    2000-01-01

    We have conducted a high-resolution polarization study with the VLBA at 22 and 43 GHz to look for differences in the parsec-scale magnetic field structures of 18 high- and low-optically polarized, compact radio-loud quasars (HPQs and LPRQs, respectively).

  13. Superior adsorption of pharmaceutical molecules by highly porous BN nanosheets.

    PubMed

    Liu, Dan; Lei, Weiwei; Qin, Si; Klika, Karel D; Chen, Ying

    2016-01-01

    Highly porous boron nitride nanosheets (BNNSs) were tested as a re-usable adsorbent for the removal of pharmaceuticals from aqueous solution. The BNNSs exhibit both unprecedentedly high adsorption capacities and excellent recyclability while maintaining their high adsorption capacity by a simple regeneration process. These advantages render BNNSs a promising material for water remediation applications. PMID:26618906

  14. High-throughput single-molecule screen for small-molecule perturbation of splicing and transcription kinetics.

    PubMed

    Day, Christopher R; Chen, Huimin; Coulon, Antoine; Meier, Jordan L; Larson, Daniel R

    2016-03-01

    In eukaryotes, mRNA synthesis is catalyzed by RNA polymerase II and involves several distinct steps, including transcript initiation, elongation, cleavage, and transcript release. Splicing of RNA can occur during (co-transcriptional) or after (post-transcriptional) RNA synthesis. Thus, RNA synthesis and processing occurs through the concerted activity of dozens of enzymes, each of which is potentially susceptible to perturbation by small molecules. However, there are few, if any, high-throughput screening strategies for identifying drugs which perturb a specific step in RNA synthesis and processing. Here we have developed a high-throughput fluorescence microscopy approach in single cells to screen for inhibitors of specific enzymatic steps in RNA synthesis and processing. By utilizing the high affinity interaction between bacteriophage capsid proteins (MS2, PP7) and RNA stem loops, we are able to fluorescently label the intron and exon of a β-globin reporter gene in human cells. This approach allows one to measure the kinetics of transcription, splicing and release in both fixed and living cells using a tractable, genetically encoded assay in a stable cell line. We tested this reagent in a targeted screen of molecules that target chromatin readers and writers and identified three compounds that slow transcription elongation without changing transcription initiation. PMID:26655523

  15. High Power Dynamic Polarization Control Using Plasma Photonics.

    PubMed

    Turnbull, D; Michel, P; Chapman, T; Tubman, E; Pollock, B B; Chen, C Y; Goyon, C; Ross, J S; Divol, L; Woolsey, N; Moody, J D

    2016-05-20

    We report the first experimental demonstration of a plasma wave plate based on laser-induced birefringence. An elliptically polarized input was converted into a nearly ideal circularly polarized beam using an optical system composed of a second laser beam and a plasma. The results are in excellent agreement with linear theory and three-dimensional simulations up to phase delays exceeding π/4, thus establishing the feasibility of laser-plasma photonic devices that are ultrafast, damage-resistant, and easily tunable. PMID:27258871

  16. Dual-band and high-efficiency polarization converter based on metasurfaces at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Liu, Yajun; Xia, Song; Shi, Hongyu; Zhang, Anxue; Xu, Zhuo

    2016-06-01

    We present a dual-band and high-efficiency polarization converter in microwave regime. The proposed converter can convert a linearly polarized wave to its cross-polarized wave for two distinct bands: Ku (11.5-20.0 GHz) and Ka (28.8-34.0 GHz). It can also convert the linearly polarized wave to a circularly polarized wave at four other frequencies. The experimental results are in good agreement with simulation results for both frequency bands. The polarization conversion ratio is above 0.94 for the Ku-band and 0.90 for the Ka-band. Furthermore, the converter can achieve dual-band and high-efficiency polarization conversion over angles of incidence up to 45°. The converter is also polarization-selective in that only the x- and y-polarized waves can be converted. The physical mechanism of the dual-band polarization conversion effect is interpreted via decomposed electric field components that couple with different plasmon resonance modes of the structure.

  17. Investigation of parameter-free model polarization potentials for electron-molecule scattering calculations including the nuclear motion

    SciTech Connect

    Morrison, M.A.; Saha, B.C.

    1986-10-01

    A correlation-polarization potential originally introduced by O'Connell and Lane (Phys. Rev. A 27, 1893 (1983)) is used in e-H/sub 2/ scattering calculations in which the vibrational motion of the target is taken into account. Eigenphase sums (as a function of internuclear separation) and cross sections for elastic scattering and for rovibrational excitations are compared to their counterparts calculated using the ab initio nonadiabatic model polarization potential of Gibson and Morrison (Phys. Rev. A 29, 2497 (1984)). At low energies, these scattering quantities are found to be quite sensitive to the treatment of polarization. To assess these model potentials, theoretical total, momentum transfer, and rotational- and vibrational-excitation cross sections are compared to experimental data.

  18. A high extinction ratio THz polarizer fabricated by double-bilayer wire grid structure

    NASA Astrophysics Data System (ADS)

    Lu, Bin; Wang, Haitao; Shen, Jun; Yang, Jun; Mao, Hongyan; Xia, Liangping; Zhang, Weiguo; Wang, Guodong; Peng, Xiao-Yu; Wang, Deqiang

    2016-02-01

    We designed a new style of broadband terahertz (THz) polarizer with double-bilayer wire grid structure by fabricating them on both sides of silicon substrate. This THz polarizer shows a high average extinction ratio of 60dB in 0.5 to 2.0 THz frequency range and the maximum of 87 dB at 1.06 THz, which is much higher than that of conventional monolayer wire grid polarizers and single-bilayer wire grid ones.

  19. Polarization-independent optical circulator for high accuracy Faraday depolarization lidar.

    PubMed

    Shiina, Tatsuo; Noguchi, Kazuo; Fukuchi, Tetsuo

    2012-03-01

    A high precision, polarization-independent optical circulator was developed for high accuracy Faraday depolarization lidar. Glan laser prisms and other novel optics were utilized in the circulator optics, resulting in a high extinction ratio of polarization of >30 dB. High accuracy is needed to detect a small rotation angle in the polarization plane of the propagating beam. It is generated by the Faraday effect due to the lightning discharge. The developed circulator delivered high performance of insertion loss and isolation as laser transmitter and echo receiver in the inline lidar optics. PMID:22410893

  20. Fusion with highly spin polarized HD and D sub 2

    SciTech Connect

    Honig, A.

    1992-06-29

    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)

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

    SciTech Connect

    Not Available

    1991-12-31

    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.

  2. Quantum coherent π-electron rotations in a non-planar chiral molecule induced by using a linearly polarized UV laser pulse

    NASA Astrophysics Data System (ADS)

    Mineo, Hirobumi; Fujimura, Yuichi

    2015-06-01

    We propose an ultrafast quantum switching method of π-electron rotations, which are switched among four rotational patterns in a nonplanar chiral aromatic molecule (P)-2,2’- biphenol and perform the sequential switching among four rotational patterns which are performed by the overlapped pump-dump laser pulses. Coherent π-electron dynamics are generated by applying the linearly polarized UV pulse laser to create a pair of coherent quasidegenerated excited states. We also plot the time-dependent π-electron ring current, and discussed ring current transfer between two aromatic rings.

  3. Efficient production of polar molecular Bose-Einstein condensates via an all-optical R-type atom-molecule adiabatic passage

    NASA Astrophysics Data System (ADS)

    Qian, Jing; Zhou, Lu; Zhang, Keye; Zhang, Weiping

    2010-03-01

    We propose a scheme of 'R-type' photoassociative adiabatic passage (PAP) to create polar molecular condensates from two different species of ultracold atoms. Due to the presence of a quasi-coherent population trapping state in the scheme, it is possible to associate atoms into molecules with a low-power photoassociation (PA) laser. One remarkable advantage of our scheme is that a tunable atom-molecule coupling strength can be achieved by using a time-dependent PA field, which exhibits larger flexibility than using a tunable magnetic field. In addition, our results show that the PA intensity required in the 'R-type' PAP could be greatly reduced compared to that in a conventional 'Λ-type' one.

  4. Polarization-independent and high-efficiency dielectric metasurfaces for visible light.

    PubMed

    Li, Qi-Tong; Dong, Fengliang; Wang, Bong; Gan, Fengyuan; Chen, Jianjun; Song, Zhiwei; Xu, Lixua; Chu, Weiguo; Xiao, Yun-Feng; Gong, Qihuang; Li, Yan

    2016-07-25

    Dielectric metasurfaces are capable of completely manipulating the phase, amplitude, and polarization of light with high spatial resolutions. The emerging design based on high-index and low-loss dielectrics has led to the realization of novel metasurfaces with high transmissions, but these devices usually operate at the limited bandwidth, and are sensitive to the incident polarization. Here, we report the realization of the polarization-independent and high-efficiency silicon metasurfaces spanning the visible wavelengths about 200 nm. The fabricated computer-generated meta-holograms exhibit a 90% diffraction efficiency, which are verified by gradient metasurfaces with measured efficiencies up to 93% at 670 nm, and exceeding 75% at the wavelengths from 600 to 800 nm for the two orthogonally polarized incidences. These dielectric metasurfaces effectively decouple the phase modulation from the polarization states and frequencies for visible light, which hold great potential for novel flat optical devices operating over a broad spectrum. PMID:27464084

  5. Development of high harmonic generation spectroscopy of organic molecules and biomolecules

    NASA Astrophysics Data System (ADS)

    Marangos, J. P.

    2016-07-01

    In this review we will discuss the topic of high order harmonic generation (HHG) from samples of organic and bio-molecules. The possibility to extract useful dynamical and structural information from the measurement of the HHG emission, a technique termed high harmonic generation spectroscopy (HHGS), will be the special focus of our discussions. We will begin by introducing the salient facts of HHG from atoms and simple molecules and explaining the principles behind HHGS. Next the technical difficulties associated with HHG from samples of organic molecules and biomolecules, principally the low sample density and the low ionization potential, will be examined. Then we will present some recent experiments where HHG spectra from samples of these molecules have been measured and discuss what has been learned from these measurements. Finally we will look at the future prospects for HHG spectroscopy of organic molecules, discussing some of the technical and in principle limits of the technique and methods that may ameliorate these limits.

  6. The artificial control of enhanced optical processes in fluorescent molecules on high-emittance metasurfaces

    NASA Astrophysics Data System (ADS)

    Iwanaga, Masanobu; Choi, Bongseok; Miyazaki, Hideki T.; Sugimoto, Yoshimasa

    2016-05-01

    Plasmon-enhanced optical processes in molecules have been extensively but individually explored for Raman scattering, fluorescence, and infrared light absorption. In contrast to recent progress in the interfacial control of hot electrons in plasmon-semiconductor hybrid systems, plasmon-molecule hybrid systems have remained to be a conventional scheme, mainly assuming electric-field enhancement. This was because it was difficult to control the plasmon-molecule interface in a well-controlled manner. We here experimentally substantiate an obvious change in artificially enhanced optical processes of fluorescence/Raman scattering in fluorescent molecules on high-emittance plasmo-photonic metasurfaces with/without a self-assembled monolayer of sub-nm thickness. These results indicate that the enhanced optical processes were successfully selected under artificial configurations without any additional chemical treatment that modifies the molecules themselves. Although Raman-scattering efficiency is generally weak in high-fluorescence-yield molecules, it was found that Raman scattering becomes prominent around the molecular fingerprint range on the metasurfaces, being enhanced by more than 2000 fold at the maximum for reference signals. In addition, the highly and uniformly enhancing metasurfaces are able to serve as two-way functional, reproducible, and wavelength-tunable platforms to detect molecules at very low densities, being distinct from other platforms reported so far. The change in the enhanced signals suggests that energy diagrams in fluorescent molecules are changed in the configuration that includes the metal-molecule interface, meaning that plasmon-molecule hybrid systems are rich in the phenomena beyond the conventional scheme.Plasmon-enhanced optical processes in molecules have been extensively but individually explored for Raman scattering, fluorescence, and infrared light absorption. In contrast to recent progress in the interfacial control of hot electrons

  7. High-resolution observations of the polar magnetic fields of the sun

    NASA Technical Reports Server (NTRS)

    Lin, H.; Varsik, J.; Zirin, H.

    1994-01-01

    High-resolution magnetograms of the solar polar region were used for the study of the polar magnetic field. In contrast to low-resolution magnetograph observations which measure the polar magnetic field averaged over a large area, we focused our efforts on the properties of the small magnetic elements in the polar region. Evolution of the filling factor (the ratio of the area occupied by the magnetic elements to the total area) of these magnetic elements, as well as the average magnetic field strength, were studied during the maximum and declining phase of solar cycle 22, from early 1991 to mid-1993. We found that during the sunspot maximum period, the polar regions were occupied by about equal numbers of positive and negative magnetic elements, with equal average field strength. As the solar cycle progresses toward sunspot minimum, the magnetic field elements in the polar region become predominantly of one polarity. The average magnetic field of the dominant polarity elements also increases with the filling factor. In the meanwhile, both the filling factor and the average field strength of the non-dominant polarity elements decrease. The combined effects of the changing filling factors and average field strength produce the observed evolution of the integrated polar flux over the solar cycle. We compared the evolutionary histories of both filling factor and average field strength, for regions of high (70-80 deg) and low (60-70 deg) latitudes. For the south pole, we found no significant evidence of difference in the time of reversal. However, the low-latitude region of the north pole did reverse polarity much earlier than the high-latitude region. It later showed an oscillatory behavior. We suggest this may be caused by the poleward migration of flux from a large active region in 1989 with highly imbalanced flux.

  8. Superhard Coatings Synthesis Assisted by Pulsed Beams of High-Energy Gas Molecules

    NASA Astrophysics Data System (ADS)

    Metel, Alexander; Bolbukov, Vasily; Volosova, Marina; Grigoriev, Sergei; Melnik, Yury; Department of high-efficiency machining technologies Team

    2015-09-01

    For production of nanocomposite superhard (HV 5000) and fracture-tough coatings on dielectric substrates a source of metal atoms accompanied by pulsed beams of 30-keV neutral molecules was used. The source is equipped with two parallel equipotential grids placed between a magnetron target and a substrate. Negative high-voltage pulses applied to the high-transparency grids accelerate from the magnetron plasma ions, which are transformed into high-energy neutral molecules due to charge-exchange collisions with gas molecules between the grids. Mixing of the substrate and coating materials through bombardment by high-energy gas molecules results in an adequate compressive stress of the coating and interface width exceeding 1 μm, which allows deposition of 100- μm-thick coatings with a perfect adhesion. The work was supported by the Grant No. 14-29-00297 of the Russian Science Foundation.

  9. Charmonium production in polarized high-energy collisions

    NASA Astrophysics Data System (ADS)

    Klasen, M.; Kniehl, B. A.; Mihaila, L. N.; Steinhauser, M.

    2003-08-01

    We investigate the inclusive production of prompt J/ψ mesons in polarized hadron-hadron, photon-hadron, and photon-photon collisions in the factorization formalism of nonrelativistic quantum chromodynamics (NRQCD) providing all contributing partonic cross sections in analytic form. In the case of photoproduction, we also include the resolved-photon contributions. We present numerical results appropriate for BNL RHIC-Spin, the approved SLAC fixed-target experiment E161, and the e+e- and γγ modes of DESY TESLA. Specifically, we assess the feasibility to access the spin-dependent parton distributions in the polarized proton and photon. We also point out that preliminary data on J/ψ inclusive production taken by the PHENIX Collaboration in unpolarized proton-proton collisions at RHIC tend to favor the NRQCD factorization hypothesis, while they significantly overshoot the theoretical prediction of the color-singlet model at large values of transverse momentum.

  10. Highly Crystalline Films of Organic Small Molecules with Alkyl Chains Fabricated by Weak Epitaxy Growth.

    PubMed

    Zhu, Yangjie; Chen, Weiping; Wang, Tong; Wang, Haibo; Wang, Yue; Yan, Donghang

    2016-05-12

    Because side-chain engineering of organic conjugated molecules has been widely utilized to tune organic solid-state optoelectronic properties, the achievement of their high-quality films is important for realizing high-performance devices. Here, highly crystalline films of an organic molecule with short alkyl chains, 5,8,15,18-tetrabutyl-5,8,15,18-tetrahydroindolo[3,2-a]indole[30,20:5,6]quinacridone (C4-IDQA), are fabricated by weak epitaxy growth, and highly oriented, large-area, and continuous films are obtained. Because of the soft matter properties, the C4-IDQA molecules can adjust themselves to realize commensurate epitaxy growth on the inducing layers and exhibited good lattice matching in the thin film phase. The crystalline phase is also observed in thicker C4-IDQA films. The growth behavior of C4-IDQA on the inducing layer is further investigated, including the strong dependence of film morphologies on substrate temperatures and deposition rates due to the poor diffusion ability of C4-IDQA molecules. Moreover, highly crystalline films and high electron field-effect mobility are also obtained for the small molecule N,N'-dioctyl-3,4:9,10-perylene tetracarboxylic diimide (C8-PTCDI), which demonstrate that the weak epitaxy growth method could be an effective way to fabricate highly crystalline films of organic small molecules with flexible side chains. PMID:27116036

  11. High dynamic, spectral, and polarized natural light environment acquisition

    NASA Astrophysics Data System (ADS)

    Porral, Philippe; Callet, Patrick; Fuchs, Philippe; Muller, Thomas; Sandré-Chardonnal, Etienne

    2015-03-01

    In the field of image synthesis, the simulation of material's appearance requires a rigorous resolution of the light transport equation. This implies taking into account all the elements that may have an influence on the spectral radiance, and that are perceived by the human eye. Obviously, the reflectance properties of the materials have a major impact in the calculations, but other significant properties of light such as spectral distribution and polarization must also be taken into account, in order to expect correct results. Unfortunately real maps of the polarized or spectral environment corresponding to a real sky do not exist. Therefore, it seemed necessary to focus our work on capturing such data, in order to have a system that qualifies all the properties of light and capable of powering simulations in a renderer software. As a consequence, in this work, we develop and characterize a device designed to capture the entire light environment, by taking into account both the dynamic range of the spectral distribution and the polarization states, in a measurement time of less than two minutes. We propose a data format inspired by polarimetric imaging and fitted for a spectral rendering engine, which exploits the "Stokes-Mueller formalism."

  12. The artificial control of enhanced optical processes in fluorescent molecules on high-emittance metasurfaces.

    PubMed

    Iwanaga, Masanobu; Choi, Bongseok; Miyazaki, Hideki T; Sugimoto, Yoshimasa

    2016-06-01

    Plasmon-enhanced optical processes in molecules have been extensively but individually explored for Raman scattering, fluorescence, and infrared light absorption. In contrast to recent progress in the interfacial control of hot electrons in plasmon-semiconductor hybrid systems, plasmon-molecule hybrid systems have remained to be a conventional scheme, mainly assuming electric-field enhancement. This was because it was difficult to control the plasmon-molecule interface in a well-controlled manner. We here experimentally substantiate an obvious change in artificially enhanced optical processes of fluorescence/Raman scattering in fluorescent molecules on high-emittance plasmo-photonic metasurfaces with/without a self-assembled monolayer of sub-nm thickness. These results indicate that the enhanced optical processes were successfully selected under artificial configurations without any additional chemical treatment that modifies the molecules themselves. Although Raman-scattering efficiency is generally weak in high-fluorescence-yield molecules, it was found that Raman scattering becomes prominent around the molecular fingerprint range on the metasurfaces, being enhanced by more than 2000 fold at the maximum for reference signals. In addition, the highly and uniformly enhancing metasurfaces are able to serve as two-way functional, reproducible, and wavelength-tunable platforms to detect molecules at very low densities, being distinct from other platforms reported so far. The change in the enhanced signals suggests that energy diagrams in fluorescent molecules are changed in the configuration that includes the metal-molecule interface, meaning that plasmon-molecule hybrid systems are rich in the phenomena beyond the conventional scheme. PMID:27227964

  13. 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)

    Beausang, John F.

    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

  14. High speed and high power polarization insensitive germanium photodetector with lumped structure.

    PubMed

    Chen, Guanyu; Yu, Yu; Xiao, Xi; Zhang, Xinliang

    2016-05-01

    We propose and demonstrate a high speed and high power polarization insensitive germanium photodetector (Ge PD) with lumped structure based on related parallel Ge absorption regions. Two absorption regions are double sides illuminated to optimize the space charge density and the two dimensional (2D) grating coupler is adopted for both coupling and polarization independent operation. Being different from previous reported high power scheme with separate absorption areas, the proposed structure is specifically designed with doubled but related Ge absorption regions, forming the equivalent parallel resistor and thus the parasitic parameter can be engineered to ensure a simultaneous large bandwidth. The bandwidth is measured to be >35 GHz, while the maximum current density is measured to be 1.152 mA/μm3. The dark current and the responsivity of the proposed Ge PD are measured to be 1.82 μΑ and 1.06 A/W. Modulated signals experimentally validate the high speed operation and doubled power handling capacity for the proposed scheme. Furthermore, the bit error rate results show the superior performance for the proposed Ge PD at high photocurrent. PMID:27137613

  15. Cooperative Emission of Dye Molecules at High Dephasing Rates

    NASA Astrophysics Data System (ADS)

    Klochkov, V. P.; Verkhovskiĭ, E. B.

    2000-05-01

    The dependence of the emission of a concentrated (˜1019 cm-3 solution of Rhodamine C on the power density Φ of exciting laser radiation was studied. The emission intensity for the power density of exciting radiation above ˜1025 cm-2 s-1 was found to have a nearly quadratic dependence on the power density Φ, and this emission was interpreted as the cooperative spontaneous emission of a Dicke type. For Φ≲1025 cm-2 s-1, the emission intensity increased with increasing Φ according to the exponential law. This emission was interpreted as the amplified spontaneous emission. The spectra of cooperative emission depended on the pump radiation power only weakly. The absence of lasing in dye solutions at high concentrations, which is a well-known phenomenon, was shown to be caused by the development of the cooperative spontaneous emission and not by the concentration quenching, and the former process is more rapid than the latter.

  16. Bright high-order harmonic generation with controllable polarization from a relativistic plasma mirror.

    PubMed

    Chen, Zi-Yu; Pukhov, Alexander

    2016-01-01

    Ultrafast extreme ultraviolet (XUV) sources with a controllable polarization state are powerful tools for investigating the structural and electronic as well as the magnetic properties of materials. However, such light sources are still limited to only a few free-electron laser facilities and, very recently, to high-order harmonic generation from noble gases. Here we propose and numerically demonstrate a laser-plasma scheme to generate bright XUV pulses with fully controlled polarization. In this scheme, an elliptically polarized laser pulse is obliquely incident on a plasma surface, and the reflected radiation contains pulse trains and isolated circularly or highly elliptically polarized attosecond XUV pulses. The harmonic polarization state is fully controlled by the laser-plasma parameters. The mechanism can be explained within the relativistically oscillating mirror model. This scheme opens a practical and promising route to generate bright attosecond XUV pulses with desirable ellipticities in a straightforward and efficient way for a number of applications. PMID:27531047

  17. Bright high-order harmonic generation with controllable polarization from a relativistic plasma mirror

    PubMed Central

    Chen, Zi-Yu; Pukhov, Alexander

    2016-01-01

    Ultrafast extreme ultraviolet (XUV) sources with a controllable polarization state are powerful tools for investigating the structural and electronic as well as the magnetic properties of materials. However, such light sources are still limited to only a few free-electron laser facilities and, very recently, to high-order harmonic generation from noble gases. Here we propose and numerically demonstrate a laser–plasma scheme to generate bright XUV pulses with fully controlled polarization. In this scheme, an elliptically polarized laser pulse is obliquely incident on a plasma surface, and the reflected radiation contains pulse trains and isolated circularly or highly elliptically polarized attosecond XUV pulses. The harmonic polarization state is fully controlled by the laser–plasma parameters. The mechanism can be explained within the relativistically oscillating mirror model. This scheme opens a practical and promising route to generate bright attosecond XUV pulses with desirable ellipticities in a straightforward and efficient way for a number of applications. PMID:27531047

  18. Polarization spectroscopy of x-ray transitions from beam-excited highly charged ions

    SciTech Connect

    Beiersdorfer, P.; Lopez-Urrutia, J.C.; Decaux, V.; Widmann, K.; Neill, P.

    1997-01-01

    Polarization spectroscopy of x-ray lines represents a diagnostic tool to ascertain the presence of electron beams in high-temperature plasmas. Making use of the Livermore electron beam ion trap, which optimizes the linear x-ray line polarization by exciting highly charged ions with a monoenergetic electron beam, we have begun to develop polarization diagnostics and test theoretical models. Our measurement relies on the sensitivity of crystal spectrometers to the linear polarization of x-ray lines which depends on the value of the Bragg angle. We employed two spectrometers with differing analyzing crystals and simultaneously recorded the K-shell emission from heliumlike Fe{sup 24+} and lithiumlike Fe{sup 23+} ions at two different Bragg angles. A clear difference in the relative intensities of the dominant transitions is observed, which is attributed to the amount of linear polarization of the individual lines. {copyright} {ital 1997 American Institute of Physics.}

  19. Non-collinear generation of angularly isolated circularly polarized high harmonics

    NASA Astrophysics Data System (ADS)

    Hickstein, Daniel D.; Dollar, Franklin J.; Grychtol, Patrik; Ellis, Jennifer L.; Knut, Ronny; Hernández-García, Carlos; Zusin, Dmitriy; Gentry, Christian; Shaw, Justin M.; Fan, Tingting; Dorney, Kevin M.; Becker, Andreas; Jaroń-Becker, Agnieszka; Kapteyn, Henry C.; Murnane, Margaret M.; Durfee, Charles G.

    2015-11-01

    We generate angularly isolated beams of circularly polarized extreme ultraviolet light through the first implementation of non-collinear high harmonic generation with circularly polarized driving lasers. This non-collinear technique offers numerous advantages over previous methods, including the generation of higher photon energies, the separation of the harmonics from the pump beam, the production of both left and right circularly polarized harmonics at the same wavelength and the capability of separating the harmonics without using a spectrometer. To confirm the circular polarization of the beams and to demonstrate the practicality of this new light source, we measure the magnetic circular dichroism of a 20 nm iron film. Furthermore, we explain the mechanisms of non-collinear high harmonic generation using analytical descriptions in both the photon and wave models. Advanced numerical simulations indicate that this non-collinear mixing enables the generation of isolated attosecond pulses with circular polarization.

  20. Baroclinic Instability in High Latitudes Induced by Polar Vortex: A Connection to the Arctic Oscillation.

    NASA Astrophysics Data System (ADS)

    Tanaka, H. L.; Tokinaga, Hiroki

    2002-01-01

    In this study, baroclinic instability of the northern winter atmosphere is investigated in the context of the dynamical interpretation of the Arctic oscillation. The unstable solutions, obtained by a method of 3D normal mode expansion, are compared for observed zonal basic states with strong and weak polar vortices in reference to the Arctic oscillation index.As a result of the eigenvalue problem of the linear stability analysis, a characteristic unstable solution is obtained that dominates in high latitudes when the polar vortex is strong. The mode is called a monopole Charney mode M1, which is similar to an ordinary Charney mode MC in midlatitudes. In order to understand the origin of the M1 mode, a hypothetical zonal basic state that has only the polar jet with no subtropical jet is analyzed. It is found that the M1 mode in high latitudes is excited by the baroclinicity associated with the polar vortex. The M1 mode in high latitudes is dynamically the same Charney mode as MC but is excited by the baroclinicity of the polar jet instead of the subtropical jet.As the MC mode intensifies the subtropical jet by the eddy momentum transfer, the M1 mode transfers eddy momentum to high latitudes to intensify the polar jet. Since M1 mode appears during the strong polar jet and feeds the westerly momentum to the polar jet, there is a positive feedback between the M1 mode and the polar vortex. This positive feedback would produce a persistent strong polar jet, which may in tern result in the occurrence of the annular mode of the Arctic oscillation.


  1. Retrieval and analysis of a polarized high-spectral-resolution lidar for profiling aerosol optical properties.

    PubMed

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

    2013-06-01

    Taking advantage of the broad spectrum of the Cabannes-Brillouin scatter from atmospheric molecules, the high spectral resolution lidar (HSRL) technique employs a narrow spectral filter to separate the aerosol and molecular scattering components in the lidar return signals and therefore can obtain the aerosol optical properties as well as the lidar ratio (i.e., the extinction-to-backscatter ratio) which is normally selected or modeled in traditional backscatter lidars. A polarized HSRL instrument, which employs an interferometric spectral filter, is under development at the Zhejiang University (ZJU), China. In this paper, the theoretical basis to retrieve the aerosol lidar ratio, depolarization ratio and extinction and backscatter coefficients, is presented. Error analyses and sensitivity studies have been carried out on the spectral transmittance characteristics of the spectral filter. The result shows that a filter that has as small aerosol transmittance (i.e., large aerosol rejection rate) and large molecular transmittance as possible is desirable. To achieve accurate retrieval, the transmittance of the spectral filter for molecular and aerosol scattering signals should be well characterized. PMID:23736562

  2. High-order-harmonic generation in molecular sequential double ionization by intense circularly polarized laser pulses

    NASA Astrophysics Data System (ADS)

    Yuan, Kai-Jun; Lu, Huizhong; Bandrauk, André D.

    2015-08-01

    We present effects of electron energy transfer by electron collisions on high-order-harmonic generation (HHG) in molecular sequential double ionization by intense circularly polarized laser pulses. Results from numerical solutions of time-dependent Schrödinger equations for extended (large internuclear distance) H2 where electrons are entangled and hence delocalized by exchange show that HHG with cutoff energy up to Ip+24 Up can be obtained, where Ip is the molecule ionization potential and Up=I0/4 ω02 (in atomic units) is the ponderomotive energy for pulse intensity I0 and frequency ω0. A time-frequency analysis is employed to identify electron collisions for the generation of harmonics. Extended HHG arises from electron energy exchange, which agrees well with the prediction of a classical two electron collision model. Results for nonsymmetric HHe+ where initially electrons are localized on He are also compared and confirm the role of initial electron delocalization via entanglement for obtaining extended HHG plateaus.

  3. A highly parallel microfluidic droplet method enabling single-molecule counting for digital enzyme detection

    PubMed Central

    Guan, Zhichao; Zou, Yuan; Zhang, Mingxia; Lv, Jiangquan; Shen, Huali; Yang, Pengyuan; Zhang, Huimin; Zhu, Zhi; James Yang, Chaoyong

    2014-01-01

    Although digital detection of nucleic acids has been achieved by amplification of single templates in uniform microfluidic droplets and widely used for genetic analysis, droplet-based digital detection of proteins has rarely been reported, largely due to the lack of an efficient target amplification method for protein in droplets. Here, we report a key step towards digital detection of proteins using a highly parallel microfluidic droplet approach for single enzyme molecule detection in picoliter droplets via enzyme catalyzed signal amplification. An integrated microfluidic chip was designed for high throughput uniform droplet generation, monolayer droplet collection, incubation, detection, and release. Single β-galatosidase (β-Gal) molecules and the fluorogenic substrate fluorescein di-β-D-galactopyranoside were injected from two separated inlets to form uniform 20 μm droplets in fluorinated oil at a frequency of 6.6 kHz. About 200 000 droplets were captured as a monolayer in a capture well on-chip for subsequent imaging detection. A series of β-Gal solutions at different concentrations were analyzed at the single-molecule level. With no enzyme present, no droplets were found to fluoresce, while brightly fluorescent droplets were observed under single-enzyme molecule conditions. Droplet fluorescence intensity distribution analysis showed that the distribution of enzyme molecules under single-molecule conditions matched well with theoretical prediction, further proving the feasibility of detecting single enzyme molecules in emulsion droplets. Moreover, the population of fluorescent droplets increased as the β-Gal concentration increased. Based on a digital counting method, the measured concentrations of the enzyme were found to match well with input enzyme concentration, establishing the accuracy of the digital detection method for the quantification of β-Gal enzyme molecules. The capability of highly parallel detection of single enzyme molecules in

  4. Magnetic anisotropy and high-spin effects in single-molecule transistors

    NASA Astrophysics Data System (ADS)

    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

    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 Fe 4 . 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.

  5. Observation of New Dynamics in the State-Resolved Collisional Relaxation of Highly Excited Molecules

    NASA Astrophysics Data System (ADS)

    Echebiri, Geraldine O.; Smarte, Matthew; Walters, Wendell W.; Cleveland, Jill M.; McCarl, Christine; Kunin, Alice; Mullin, Amy S.

    2013-06-01

    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 λ = 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.

  6. Highly Repeatable Dissolution Dynamic Nuclear Polarization for Heteronuclear NMR Metabolomics.

    PubMed

    Bornet, Aurélien; Maucourt, Mickaël; Deborde, Catherine; Jacob, Daniel; Milani, Jonas; Vuichoud, Basile; Ji, Xiao; Dumez, Jean-Nicolas; Moing, Annick; Bodenhausen, Geoffrey; Jannin, Sami; Giraudeau, Patrick

    2016-06-21

    At natural (13)C abundance, metabolomics based on heteronuclear NMR is limited by sensitivity. We have recently demonstrated how hyperpolarization by dissolution dynamic nuclear polarization (D-DNP) assisted by cross-polarization (CP) provides a reliable way of enhancing the sensitivity of heteronuclear NMR in dilute mixtures of metabolites. In this Technical Note, we evaluate the precision of this experimental approach, a critical point for applications to metabolomics. The higher the repeatability, the greater the likelihood that one can detect small biologically relevant differences between samples. The average repeatability of our state-of-the-art D-DNP NMR equipment for samples of metabolomic relevance (20 mg dry weight tomato extracts) is 3.6% for signals above the limit of quantification (LOQ) and 6.4% when all the signals above the limit of detection (LOD) are taken into account. This first report on the repeatability of D-DNP highlights the compatibility of the technique with the requirements of metabolomics and confirms its potential as an analytical tool for such applications. PMID:27253320

  7. Reexamining the high-order harmonic generation of HD molecule in non-Born-Oppenheimer approximation

    NASA Astrophysics Data System (ADS)

    Du, Hongchuan; Yue, Shengjun; Wang, Huiqiao; Wu, Hongmei; Hu, Bitao

    2016-03-01

    The high-order harmonic generation of the HD molecule is studied in non-Born-Oppenheimer approximation. It is found that there are only the odd harmonics in the harmonic spectrum of the HD molecule though the generation of even harmonics is possible in principle. Theoretical analysis [T. Kreibich et al., Phys. Rev. Lett. 87, 103901 (2001)] reveals that the nuclear dipole moment can contribute to the generation of the even harmonics, but the acceleration of the nucleus is about three orders of magnitude less than that of the electron. Hence, the even harmonics cannot be observed in the harmonic spectrum of the HD molecule.

  8. Ultra high-throughput single molecule spectroscopy with a 1024 pixel SPAD

    PubMed Central

    Colyer, Ryan A.; Scalia, Giuseppe; Villa, Federica A.; Guerrieri, Fabrizio; Tisa, Simone; Zappa, Franco; Cova, Sergio; Weiss, Shimon; Michalet, Xavier

    2013-01-01

    Single-molecule spectroscopy is a powerful approach to measuring molecular properties such as size, brightness, conformation, and binding constants. Due to the low concentrations in the single-molecule regime, measurements with good statistical accuracy require long acquisition times. Previously we showed a factor of 8 improvement in acquisition speed using a custom-CMOS 8x1 SPAD array. Here we present preliminary results with a 64X improvement in throughput obtained using a liquid crystal on silicon spatial light modulator (LCOS-SLM) and a novel standard CMOS 1024 pixel SPAD array, opening the way to truly high-throughput single-molecule spectroscopy. PMID:24386535

  9. Exchange Coupling Inversion in a High-Spin Organic Triradical Molecule.

    PubMed

    Gaudenzi, R; Burzurí, E; Reta, D; Moreira, I de P R; Bromley, S T; Rovira, C; Veciana, J; van der Zant, H S J

    2016-03-01

    The magnetic properties of a nanoscale system are inextricably linked to its local environment. In adatoms on surfaces and inorganic layered structures, the exchange interactions result from the relative lattice positions, layer thicknesses, and other environmental parameters. Here, we report on a sample-dependent sign inversion of the magnetic exchange coupling between the three unpaired spins of an organic triradical molecule embedded in a three-terminal device. This ferro-to-antiferromagnetic transition is due to structural distortions and results in a high-to-low spin ground-state change in a molecule traditionally considered to be a robust high-spin quartet. Moreover, the flexibility of the molecule yields an in situ electric tunability of the exchange coupling via the gate electrode. These findings open a route to the controlled reversal of the magnetic states in organic molecule-based nanodevices by mechanical means, electrical gating, or chemical tailoring. PMID:26862681

  10. Mapping the electrostatic force field of single molecules from high-resolution scanning probe images

    PubMed Central

    Hapala, Prokop; Švec, Martin; Stetsovych, Oleksandr; van der Heijden, Nadine J.; Ondráček, Martin; van der Lit, Joost; Mutombo, Pingo; Swart, Ingmar; Jelínek, Pavel

    2016-01-01

    How electronic charge is distributed over a molecule determines to a large extent its chemical properties. Here, we demonstrate how the electrostatic force field, originating from the inhomogeneous charge distribution in a molecule, can be measured with submolecular resolution. We exploit the fact that distortions typically observed in high-resolution atomic force microscopy images are for a significant part caused by the electrostatic force acting between charges of the tip and the molecule of interest. By finding a geometrical transformation between two high-resolution AFM images acquired with two different tips, the electrostatic force field or potential over individual molecules and self-assemblies thereof can be reconstructed with submolecular resolution. PMID:27230940

  11. Effect of the surface condition of silicas with grafted monofunctional polyfluoroalkylsilanes on the adsorption of polar molecules

    NASA Astrophysics Data System (ADS)

    Roshchina, T. M.; Shoniya, N. K.; Tayakina, O. Ya.; Tkachenko, O. P.; Kustov, L. M.

    2013-08-01

    Lyophobized silicas containing relatively small numbers of grafted perfluorohexyl (1.1 nm-2) and perfluorobutyl (1.7 nm-2) groups are studied by means of gas chromatography, adsorption under static conditions, and IR spectroscopy. The results are compared to those obtained by us previously for a series of samples with dense polyfluoroalkyl monolayers (≥2.0 nm-2). Effects related to the influence of the grafting density and the size of fluorine-containing groups on the adsorption of polar compounds and the hydrophobicity of the surface are discussed.

  12. A new family of four-ring bent-core nematic liquid crystals with highly polar transverse and end groups

    PubMed Central

    Upadhyaya, Kalpana; Gude, Venkatesh; Mohiuddin, Golam

    2013-01-01

    Summary Non-symmetrically substituted four-ring achiral bent-core compounds with polar substituents, i.e.., chloro in the bent or transverse direction in the central core and cyano in the lateral direction at one terminal end of the molecule, are designed and synthesized. These molecules possess an alkoxy chain attached at only one end of the bent-core molecule. The molecular structure characterization is consistent with data from elemental and spectroscopic analysis. The materials thermal behaviour and phase characterization have been investigated by differential scanning calorimetry and polarizing microscopy. All the compounds exhibit a wide-ranging monotropic nematic phase. PMID:23400045

  13. Dynamics of the Serine Chemoreceptor in the Escherichia coli Inner Membrane: A High-Speed Single-Molecule Tracking Study

    PubMed Central

    Oh, Dongmyung; Yu, Yang; Lee, Hochan; Wanner, Barry L.; Ritchie, Ken

    2014-01-01

    We investigated the mobility of the polar localized serine chemoreceptor, Tsr, labeled by the fluorescent protein Venus in the inner membrane of live Escherichia coli cells at observation rates up to 1000 Hz. A fraction (7%) of all Tsr molecules shows free diffusion over the entire cell surface with an average diffusion coefficient of 0.40 ± 0.01 μm2 s−1. The remaining molecules were found to be ultimately confined in compartments of size 290 ± 15 nm and showed restricted diffusion at an inner barrier found at 170 ± 10 nm. At the shortest length-scales (<170 nm), all Tsr molecules diffuse equally. Disruption of the cytoskeleton and rounding of the cells resulted in an increase in the mobile fraction of Tsr molecules and a fragmenting of the previously polar cluster of Tsr consistent with a curvature-based mechanism of Tsr cluster maintenance. PMID:24411246

  14. Effects of atomic hydrogen and deuterium exposure on high polarization GaAs photocathodes

    SciTech Connect

    M. Baylac; P. Adderley; J. Brittian; J. Clark; T. Day; J. Grames; J. Hansknecht; M. Poelker; M. Stutzman; A. T. Wu; A. S. Terekhov

    2005-12-01

    Strained-layer GaAs and strained-superlattice GaAs photocathodes are used at Jefferson Laboratory to create high average current beams of highly spin-polarized electrons. High electron yield, or quantum efficiency (QE), is obtained only when the photocathode surface is atomically clean. For years, exposure to atomic hydrogen or deuterium has been the photocathode cleaning technique employed at Jefferson Laboratory. This work demonstrates that atomic hydrogen cleaning is not necessary when precautions are taken to ensure that clean photocathode material from the vendor is not inadvertently dirtied while samples are prepared for installation inside photoemission guns. Moreover, this work demonstrates that QE and beam polarization can be significantly reduced when clean high-polarization photocathode material is exposed to atomic hydrogen from an rf dissociator-style atomic hydrogen source. Surface analysis provides some insight into the mechanisms that degrade QE and polarization due to atomic hydrogen cleaning.

  15. Tunable, high-power, continuous-wave dual-polarization Yb-fiber oscillator.

    PubMed

    Zeil, Peter; Pasiskevicius, Valdas; Laurell, Fredrik

    2015-06-29

    We demonstrate a high-power, dual-polarization Yb-fiber oscillator, by separately locking the two linear polarization states defined by slow and fast axis of a polarization-maintaining gain fiber with volume Bragg gratings. Dual-line lasing is achieved with a tunable wavelength separation from 0.03 to 2 THz, while exceeding output powers of 78 W over the entire tuning range, maintaining a high beam-quality with M(2)<1.2. With this laser configuration we achieve a peak-to-peak power variation of <1% for the dual-line signal and <3% for the individual signals. PMID:26191754

  16. High-resolution mass spectrometry of small molecules bound to membrane proteins.

    PubMed

    Gault, Joseph; Donlan, Joseph A C; Liko, Idlir; Hopper, Jonathan T S; Gupta, Kallol; Housden, Nicholas G; Struwe, Weston B; Marty, Michael T; Mize, Todd; Bechara, Cherine; Zhu, Ya; Wu, Beili; Kleanthous, Colin; Belov, Mikhail; Damoc, Eugen; Makarov, Alexander; Robinson, Carol V

    2016-04-01

    Small molecules are known to stabilize membrane proteins and to modulate their function and oligomeric state, but such interactions are often hard to precisely define. Here we develop and apply a high-resolution, Orbitrap mass spectrometry-based method for analyzing intact membrane protein-ligand complexes. Using this platform, we resolve the complexity of multiple binding events, quantify small molecule binding and reveal selectivity for endogenous lipids that differ only in acyl chain length. PMID:26901650

  17. Comparison of the polarization properties in the retinas of different rodents using high resolution polarization sensitive OCT

    NASA Astrophysics Data System (ADS)

    Fialová, Stanislava; Augustin, Marco; Plasenzotti, Roberto; Rauscher, Sabine; Gröger, Marion; Pircher, Michael; Hitzenberger, Christoph K.; Baumann, Bernhard

    2015-07-01

    Animal models play an important role for understanding the pathophysiology of glaucoma and age-related macular degeneration. With these models, longitudinal studies can be performed and therefore there is need for non-invasive evaluation of disease progress. For that purpose optical coherence tomography (OCT) can be used. Since tissues with different polarization properties are important in these diseases, polarization sensitive OCT (PS-OCT) could be a valuable tool in preclinical research. In this work a high resolution PS-OCT (HR-PS-OCT) system was used in-vivo for rodent retinal imaging. A super luminescent diode with a bandwidth of 100 nm was used as a light source that yielded an axial resolution of 5.1 μm in air (3.8 μm in tissue). The A-scan rate was 83 kHz, a whole 3D dataset was acquired in a few seconds (1536x1024x200 pixels in 3.5 s) which reduced motion artifacts. Rats (Sprague-Dawley, Long-Evans and Brown Norway) as well as mice (C57BL/6) were imaged. High resolution reflectivity images showed all retinal layers in all animals. From acquired data also phase retardation, fast axis orientation and degree of polarization uniformity (DOPU) images were calculated. On phase retardation images sclera was identified as birefringent and retinal pigment epithelium (RPE) and choroid as depolarizing tissues. Our results demonstrate the suitability of the system for high speed/resolution imaging in follow up studies on rodents.

  18. Longitudinally polarized single-cycle terahertz pulses generated with high electric field strengths

    NASA Astrophysics Data System (ADS)

    Cliffe, M. J.; Graham, D. M.; Jamison, S. P.

    2016-05-01

    We demonstrate the generation of single-cycle longitudinally polarized terahertz pulses with field amplitudes in excess of 11 kV/cm using the interferometric recombination of two linearly polarized terahertz beams. High field strength transversely polarized pulses were generated by optical rectification in a matched pair of magnesium-oxide doped stoichiometric lithium niobate (MgO:SLN) crystals with a reversal in the χ333 ( 2 ) orientation. The discontinuity in χ333 ( 2 ) produces a polarity flip in the transverse field; the longitudinal field produced as a consequence of the transverse field discontinuity was measured in the far-field. Both the spatial and temporal profiles of the measured longitudinally polarized terahertz radiation were consistent with the propagation of the transverse discontinuity.

  19. Dielectric metasurfaces for complete control of phase and polarization with subwavelength spatial resolution and high transmission.

    PubMed

    Arbabi, Amir; Horie, Yu; Bagheri, Mahmood; Faraon, Andrei

    2015-11-01

    Metasurfaces are planar structures that locally modify the polarization, phase and amplitude of light in reflection or transmission, thus enabling lithographically patterned flat optical components with functionalities controlled by design. Transmissive metasurfaces are especially important, as most optical systems used in practice operate in transmission. Several types of transmissive metasurface have been realized, but with either low transmission efficiencies or limited control over polarization and phase. Here, we show a metasurface platform based on high-contrast dielectric elliptical nanoposts that provides complete control of polarization and phase with subwavelength spatial resolution and an experimentally measured efficiency ranging from 72% to 97%, depending on the exact design. Such complete control enables the realization of most free-space transmissive optical elements such as lenses, phase plates, wave plates, polarizers, beamsplitters, as well as polarization-switchable phase holograms and arbitrary vector beam generators using the same metamaterial platform. PMID:26322944

  20. High degree of polarization of the near-band-edge photoluminescence in ZnO nanowires

    PubMed Central

    2011-01-01

    We investigated the polarization dependence of the near-band-edge photoluminescence in ZnO strain-free nanowires grown by vapor phase technique. The emission is polarized perpendicular to the nanowire axis with a large polarization ratio (as high as 0.84 at 4.2 K and 0.63 at 300 K). The observed polarization ratio is explained in terms of selection rules for excitonic transitions derived from the k·p theory for ZnO. The temperature dependence of the polarization ratio evidences a gradual activation of the XC excitonic transition. PACS: 78.55.Cr, 77.22.Ej, 81.07.Gf. PMID:21854578

  1. High Field Dynamic Nuclear Polarization NMR with Surfactant Sheltered Biradicals

    PubMed Central

    2015-01-01

    We illustrate the ability to place a water-insoluble biradical, bTbk, into a glycerol/water matrix with the assistance of a surfactant, sodium octyl sulfate (SOS). This surfactant approach enables a previously water insoluble biradical, bTbk, with favorable electron–electron dipolar coupling to be used for dynamic nuclear polarization (DNP) nuclear magnetic resonance (NMR) experiments in frozen, glassy, aqueous media. Nuclear Overhauser enhancement (NOE) and paramagnetic relaxation enhancement (PRE) experiments are conducted to determine the distribution of urea and several biradicals within the SOS macromolecular assembly. We also demonstrate that SOS assemblies are an effective approach by which mixed biradicals are created through an assembly process. PMID:24506193

  2. Gamma-Ray Polarization of the Synchrotron Self-compton Process from a Highly Relativistic Jet

    NASA Astrophysics Data System (ADS)

    Chang, Zhe; Lin, Hai-Nan

    2014-11-01

    The high polarization observed in the prompt phase of some gamma-ray bursts invites extensive study of the emission mechanism. In this paper, we investigate the polarization properties of the synchrotron self-Compton (SSC) process from a highly relativistic jet. A magnetic-dominated, baryon-loaded jet ejected from the central engine travels with a large Lorentz factor. Shells with slightly different velocities collide with each other and produce shocks. The shocks accelerate electrons to a power-law distribution and, at the same time, magnify the magnetic field. Electrons move in the magnetic field and produce synchrotron photons. Synchrotron photons suffer from the Compton scattering (CS) process and then are detected by an observer located slightly off-axis. We analytically derive the formulae of photon polarization in the SSC process in two magnetic configurations: a magnetic field in the shock plane and perpendicular to the shock plane. We show that photons induced by the SSC process can be highly polarized, with the maximum polarization Π ~ 24% in the energy band [0.5, 5] MeV. The polarization depends on the viewing angles, peaking in the plane perpendicular to the magnetic field. In the energy band [0.05, 0.5] MeV, in which most γ-ray polarimeters are active, the polarization is about twice that in the Thomson limit, reaching Π ~ 20%. This implies that the Klein-Nishina effect, which is often neglected in the literature, should be carefully considered.

  3. Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism

    PubMed Central

    Fan, Tingting; Grychtol, Patrik; Knut, Ronny; Hernández-García, Carlos; Hickstein, Daniel D.; Zusin, Dmitriy; Gentry, Christian; Dollar, Franklin J.; Mancuso, Christopher A.; Hogle, Craig W.; Kfir, Ofer; Legut, Dominik; Carva, Karel; Ellis, Jennifer L.; Dorney, Kevin M.; Chen, Cong; Shpyrko, Oleg G.; Fullerton, Eric E.; Cohen, Oren; Oppeneer, Peter M.; Milošević, Dejan B.; Becker, Andreas; Jaroń-Becker, Agnieszka A.; Popmintchev, Tenio; Murnane, Margaret M.; Kapteyn, Henry C.

    2015-01-01

    We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform. PMID:26534992

  4. Bright circularly polarized soft X-ray high harmonics for X-ray magnetic circular dichroism.

    PubMed

    Fan, Tingting; Grychtol, Patrik; Knut, Ronny; Hernández-García, Carlos; Hickstein, Daniel D; Zusin, Dmitriy; Gentry, Christian; Dollar, Franklin J; Mancuso, Christopher A; Hogle, Craig W; Kfir, Ofer; Legut, Dominik; Carva, Karel; Ellis, Jennifer L; Dorney, Kevin M; Chen, Cong; Shpyrko, Oleg G; Fullerton, Eric E; Cohen, Oren; Oppeneer, Peter M; Milošević, Dejan B; Becker, Andreas; Jaroń-Becker, Agnieszka A; Popmintchev, Tenio; Murnane, Margaret M; Kapteyn, Henry C

    2015-11-17

    We demonstrate, to our knowledge, the first bright circularly polarized high-harmonic beams in the soft X-ray region of the electromagnetic spectrum, and use them to implement X-ray magnetic circular dichroism measurements in a tabletop-scale setup. Using counterrotating circularly polarized laser fields at 1.3 and 0.79 µm, we generate circularly polarized harmonics with photon energies exceeding 160 eV. The harmonic spectra emerge as a sequence of closely spaced pairs of left and right circularly polarized peaks, with energies determined by conservation of energy and spin angular momentum. We explain the single-atom and macroscopic physics by identifying the dominant electron quantum trajectories and optimal phase-matching conditions. The first advanced phase-matched propagation simulations for circularly polarized harmonics reveal the influence of the finite phase-matching temporal window on the spectrum, as well as the unique polarization-shaped attosecond pulse train. Finally, we use, to our knowledge, the first tabletop X-ray magnetic circular dichroism measurements at the N4,5 absorption edges of Gd to validate the high degree of circularity, brightness, and stability of this light source. These results demonstrate the feasibility of manipulating the polarization, spectrum, and temporal shape of high harmonics in the soft X-ray region by manipulating the driving laser waveform. PMID:26534992

  5. Gamma-ray polarization of the synchrotron self-compton process from a highly relativistic jet

    SciTech Connect

    Chang, Zhe; Lin, Hai-Nan

    2014-11-01

    The high polarization observed in the prompt phase of some gamma-ray bursts invites extensive study of the emission mechanism. In this paper, we investigate the polarization properties of the synchrotron self-Compton (SSC) process from a highly relativistic jet. A magnetic-dominated, baryon-loaded jet ejected from the central engine travels with a large Lorentz factor. Shells with slightly different velocities collide with each other and produce shocks. The shocks accelerate electrons to a power-law distribution and, at the same time, magnify the magnetic field. Electrons move in the magnetic field and produce synchrotron photons. Synchrotron photons suffer from the Compton scattering (CS) process and then are detected by an observer located slightly off-axis. We analytically derive the formulae of photon polarization in the SSC process in two magnetic configurations: a magnetic field in the shock plane and perpendicular to the shock plane. We show that photons induced by the SSC process can be highly polarized, with the maximum polarization Π ∼ 24% in the energy band [0.5, 5] MeV. The polarization depends on the viewing angles, peaking in the plane perpendicular to the magnetic field. In the energy band [0.05, 0.5] MeV, in which most γ-ray polarimeters are active, the polarization is about twice that in the Thomson limit, reaching Π ∼ 20%. This implies that the Klein-Nishina effect, which is often neglected in the literature, should be carefully considered.

  6. The Polar Vegetation Photosynthesis and Respiration Model (PolarVPRM): a parsimonious, satellite data-driven model of high-latitude CO2 exchange

    NASA Astrophysics Data System (ADS)

    Luus, K. A.; Lin, J. C.

    2015-02-01

    We introduce the Polar Vegetation Photosynthesis and Respiration Model (PolarVPRM), a remote-sensing based approach for generating accurate, high resolution (≥1 km2, three-hourly) estimates of net ecosystem CO2 exchange (NEE). PolarVPRM simulates NEE using polar-specific vegetation classes, and by representing high-latitude influences on NEE. We present a description, validation, and error analysis (first-order Taylor expansion) of PolarVPRM, followed by an examination of per-pixel trends (2001-2012) in model output for the North American terrestrial region north of 55° N. PolarVPRM was validated against eddy covariance observations from nine North American sites, of which three were used in model calibration. PolarVPRM performed well over all sites. Model intercomparisons indicated that PolarVPRM showed slightly better agreement with eddy covariance observations relative to existing models. Trend analysis (2001-2012) indicated that warming air temperatures and drought stress in forests increased growing season rates of respiration, and decreased rates of net carbon uptake by vegetation when air temperatures exceeded optimal temperatures for photosynthesis. Concurrent increases in growing season length at Arctic tundra sites allowed increases in photosynthetic uptake over time by tundra vegetation. PolarVPRM estimated that the North American high-latitude region changed from a carbon source (2001-2004) to sink (2005-2010) to source (2011-2012) in response to changing environmental conditions.

  7. Neuronal polarity and the kinesin superfamily proteins.

    PubMed

    Nakata, Takao; Hirokawa, Nobutaka

    2007-02-01

    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. PMID:17284724

  8. High Brightness and High Polarization Electron Source for Spin-LEEM

    NASA Astrophysics Data System (ADS)

    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

    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 μm for the 760˜810 nm laser wavelength, and the brightness of ˜2×107 Aṡcm-2ṡsr-1 corresponding to a reduced brightness of ˜1.0×107 Aṡcm-2ṡsr-1ṡV-1 was obtained for an extracted current of 5.3 μA. 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 μA. The second gun system (JPES-2) was already constructed and mounted to a LEEM apparatus operated at OECU.

  9. Strong-field-approximation theory of high-order harmonic generation by polyatomic molecules

    NASA Astrophysics Data System (ADS)

    Odžak, S.; Hasović, E.; Milošević, D. B.

    2016-04-01

    A theory of high-order harmonic generation by arbitrary polyatomic molecules is introduced. A polyatomic molecule is modeled by an (N +1 ) -particle system, which consists of N heavy atomic (ionic) centers and an electron. After the separation of the center-of-mass coordinate, the dynamics of this system is reduced to the relative electronic and nuclear coordinates. Various versions (with or without the dressing of the initial and/or final molecular state) of the molecular strong-field approximation are introduced. For neutral polyatomic molecules the derived expression for the T -matrix element takes a simple form. The interference minima in the harmonic spectrum are explained as a multiple-slit type of interference. This is illustrated by numerical examples for the ozone (O3) and carbon dioxide (CO2) molecules.

  10. Field-free molecular orientation of 1Σ and 2Π molecules at high temperature

    NASA Astrophysics Data System (ADS)

    Tehini, R.; Hoque, Md Z.; Faucher, O.; Sugny, D.

    2012-04-01

    We analyze the control of field-free molecular orientation at high temperature by use of a two-color laser bipulse strategy proposed in Zhang [Phys. Rev. APLRAAN1050-294710.1103/PhysRevA.83.043410 83, 043410 (2011)]. A general study shows that there exist two types of linear molecules for which a different mechanism has to be used. For molecules with a large hyperpolarizability, a monochromatic laser pre-pulse is applied before the two-color laser pulse at a time close to the rotational period Tr, while for molecules with a small hyperpolarizability, the optimal delay is found close to Tr/4 or 3Tr/4. We extend this analysis to the case of a 2Π molecule such as NO where a similar control strategy can be derived. These control processes are robust against temperature effects.

  11. Single-molecule detection at high concentrations with optical aperture nanoantennas.

    PubMed

    Alam, Md Shah; Karim, Farzia; Zhao, Chenglong

    2016-05-14

    Single-molecule detection has become an indispensable technology in life science, and medical research. In order to get meaningful information on many biological processes, single-molecule analysis is required in micro-molar concentrations. At such high concentrations, it is very challenging to isolate a single molecule with conventional diffraction-limited optics. Recently, optical aperture nanoantennas (OANs) have emerged as a powerful tool to enhance the single-molecule detection under a physiological environment. The OANs, which consist of nano-scale apertures on a metallic film, have the following unique properties: (1) nanoscale light confinement; (2) enhanced fluorescence emission; (3) tunable radiation pattern; (4) reduced background noise; and (5) massive parallel detection. This review presents the fundamentals, recent developments and future perspectives in this emerging field. PMID:27120086

  12. Single-molecule detection at high concentrations with optical aperture nanoantennas

    NASA Astrophysics Data System (ADS)

    Alam, Md Shah; Karim, Farzia; Zhao, Chenglong

    2016-05-01

    Single-molecule detection has become an indispensable technology in life science, and medical research. In order to get meaningful information on many biological processes, single-molecule analysis is required in micro-molar concentrations. At such high concentrations, it is very challenging to isolate a single molecule with conventional diffraction-limited optics. Recently, optical aperture nanoantennas (OANs) have emerged as a powerful tool to enhance the single-molecule detection under a physiological environment. The OANs, which consist of nano-scale apertures on a metallic film, have the following unique properties: (1) nanoscale light confinement; (2) enhanced fluorescence emission; (3) tunable radiation pattern; (4) reduced background noise; and (5) massive parallel detection. This review presents the fundamentals, recent developments and future perspectives in this emerging field.

  13. In situ Formation of Highly Conducting Covalent Au-C Contacts for Single-Molecule Junctions

    SciTech Connect

    Cheng, Z.L.; Hybertsen, M.; Skouta, R.; Vazquez, H.; Widawsky, J.R.; Schneebeli, S.; Chen, W.; Breslow, R.; Venkataraman, L.

    2011-06-01

    Charge transport across metal-molecule interfaces has an important role in organic electronics. Typically, chemical link groups such as thiols or amines are used to bind organic molecules to metal electrodes in single-molecule circuits, with these groups controlling both the physical structure and the electronic coupling at the interface. Direct metal-carbon coupling has been shown through C60, benzene and {pi}-stacked benzene but ideally the carbon backbone of the molecule should be covalently bonded to the electrode without intervening link groups. Here, we demonstrate a method to create junctions with such contacts. Trimethyl tin (SnMe{sub 3})-terminated polymethylene chains are used to form single-molecule junctions with a break-junction technique. Gold atoms at the electrode displace the SnMe{sub 3} linkers, leading to the formation of direct Au-C bonded single-molecule junctions with a conductance that is {approx}100 times larger than analogous alkanes with most other terminations. The conductance of these Au-C bonded alkanes decreases exponentially with molecular length, with a decay constant of 0.97 per methylene, consistent with a non-resonant transport mechanism. Control experiments and ab initio calculations show that high conductances are achieved because a covalent Au-C sigma ({sigma}) bond is formed. This offers a new method for making reproducible and highly conducting metal-organic contacts.

  14. High-density single-molecule analysis of cell surface dynamics in C. elegans embryos

    PubMed Central

    Robin, Francois B.; McFadden, William M.; Yao, Baixue; Munro, Edwin M.

    2014-01-01

    We describe a general, versatile and non-invasive method to image single molecules near the cell surface that can be applied to any GFP-tagged protein in C. elegans embryos. We exploit tunable expression via RNAi and a dynamically exchanging monomer pool to achieve fast continuous single-molecule imaging at optimal densities with signal-to-noise ratios adequate for robust single particle tracking (SPT) analysis. We also introduce and validate a new method called smPReSS that infers exchange rates from quantitative analysis of single molecule photobleaching kinetics, without using SPT. Combining SPT and smPReSS allows spatially and temporally resolved measurements of protein mobility and exchange kinetics. We use these methods (a) to resolve distinct mobility states and spatial variation in exchange rates of the polarity protein Par-6 and (b) to measure spatiotemporal modulation of actin filament assembly and disassembly. The introduction of these methods in a powerful model system offers a promising new avenue to investigate dynamic mechanisms that pattern the embryonic cell surface. PMID:24727651

  15. High-Field Dynamic Nuclear Polarization for Solid and Solution Biological NMR

    PubMed Central

    Barnes, A.B.; Paëpe, 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

    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. PMID:19194532

  16. Polarization and Piezoelectric Properties of High Performance Bismuth Sodium Titanate Single Crystals Grown by High-Oxygen-Pressure Flux Method

    NASA Astrophysics Data System (ADS)

    Suzuki, Muneyasu; Morishita, Akifumi; Kitanaka, Yuuki; Noguchi, Yuji; Miyayama, Masaru

    2010-09-01

    (Bi0.5Na0.5)TiO3 (BNT) single crystals were grown by flux method at a high oxygen pressure (PO2 ) of 1 MPa, and their polarization and piezoelectric properties were investigated. BNT single crystals exhibited a saturated polarization hysteresis with remanent polarizations (Pr) of 31 µC/cm2 along [100]c, 44 µC/cm2 along [110]c and 54 µC/cm2 along [111]c. These results show that spontaneous polarization of BNT is approximately 55 µC/cm2 or larger. Strain measurements of rhombohedral BNT crystals suggest that the polarization reversal along [111]c is achieved by non-180° Ps rotation whereas that along [100]c is accomplished by 180° Ps switching.

  17. All-reflective, highly accurate polarization rotator for high-power short-pulse laser systems.

    PubMed

    Keppler, S; Hornung, M; Bödefeld, R; Kahle, M; Hein, J; Kaluza, M C

    2012-08-27

    We present the setup of a polarization rotating device and its adaption for high-power short-pulse laser systems. Compared to conventional halfwave plates, the all-reflective principle using three zero-phase shift mirrors provides a higher accuracy and a higher damage threshold. Since plan-parallel plates, e.g. these halfwave plates, generate postpulses, which could lead to the generation of prepulses during the subsequent laser chain, the presented device avoids parasitic pulses and is therefore the preferable alternative for high-contrast applications. Moreover the device is easily scalable for large beam diameters and its spectral reflectivity can be adjusted by an appropriate mirror coating to be well suited for ultra-short laser pulses. PMID:23037123

  18. Bombardment of gas molecules on single graphene layer at high temperature

    NASA Astrophysics Data System (ADS)

    Murugesan, Ramki; Park, Jae Hyun; Ha, Dong Sung

    2014-12-01

    Graphite is widely used as a material for rocket-nozzle inserts due to its excellent thermo-physical properties as well as low density. During the operation of rockets, the surface of the graphite nozzle is subjected to very high heat fluxes and the undesirable erosion of the surface occurs due to the bombardment of gas molecules with high kinetic energy, which causes a significant reduction of nozzle performance. However, the understanding and quantification of such bombardment is not satisfactory due to its complexity: The bond breaking-forming happens simultaneously for the carbon atoms of graphene, some gas molecules penetrate through the surface, some of them are reflected from the surface, etc. In the present study, we perform extensive molecular dynamics (MD) simulations to examine the bombardment phenomena in high temperature environment (several thousand Kelvin). Advanced from the previous studies that have focused on the bombardment by light molecules (e.g., H2), we will concentrate on the impact by realistic molecules (e.g., CO2 and H2O ). LAMMPS is employed for the MD simulations with NVE ensemble and AIREBO potential for graphene. The molecular understanding of the interaction between graphene and highly energetic gas molecules will enable us to design an efficient thermo-mechanical protection system.

  19. Bombardment of gas molecules on single graphene layer at high temperature

    SciTech Connect

    Murugesan, Ramki; Park, Jae Hyun; Ha, Dong Sung

    2014-12-09

    Graphite is widely used as a material for rocket-nozzle inserts due to its excellent thermo-physical properties as well as low density. During the operation of rockets, the surface of the graphite nozzle is subjected to very high heat fluxes and the undesirable erosion of the surface occurs due to the bombardment of gas molecules with high kinetic energy, which causes a significant reduction of nozzle performance. However, the understanding and quantification of such bombardment is not satisfactory due to its complexity: The bond breaking-forming happens simultaneously for the carbon atoms of graphene, some gas molecules penetrate through the surface, some of them are reflected from the surface, etc. In the present study, we perform extensive molecular dynamics (MD) simulations to examine the bombardment phenomena in high temperature environment (several thousand Kelvin). Advanced from the previous studies that have focused on the bombardment by light molecules (e.g., H{sub 2}), we will concentrate on the impact by realistic molecules (e.g., CO{sub 2} and H{sub 2}O). LAMMPS is employed for the MD simulations with NVE ensemble and AIREBO potential for graphene. The molecular understanding of the interaction between graphene and highly energetic gas molecules will enable us to design an efficient thermo-mechanical protection system.

  20. High repetition rate Q-switched radially polarized laser with a graphene-based output coupler

    NASA Astrophysics Data System (ADS)

    Li, Lifei; Zheng, Xinliang; Jin, Chenjie; Qi, Mei; Chen, Xiaoming; Ren, Zhaoyu; Bai, Jintao; Sun, Zhipei

    2014-12-01

    We demonstrate a Q-switched radially polarized all-solid-state laser by transferring a graphene film directly onto an output coupler. The laser generates Q-switched radially polarized beam (QRPB) with a pulse width of 192 ns and 2.7 W average output power. The corresponding single pulse energy is up to 16.2 μJ with a high repetition rate of 167 kHz. The M2 factor and the polarization purity are ˜2.1 and 96%, respectively. Our QRPB source is a simple and low-cost source for a variety of applications, such as industrial material processing, optical trapping, and microscopy.

  1. Design and performance of a spin-polarized electron energy loss spectrometer with high momentum resolution.

    PubMed

    Vasilyev, D; Kirschner, J

    2016-08-01

    We describe a new "complete" spin-polarized electron energy loss spectrometer comprising a spin-polarized primary electron source, an imaging electron analyzer, and a spin analyzer of the "spin-polarizing mirror" type. Unlike previous instruments, we have a high momentum resolution of less than 0.04 Å(-1), at an energy resolution of 90-130 meV. Unlike all previous studies which reported rather broad featureless data in both energy and angle dependence, we find richly structured spectra depending sensitively on small changes of the primary energy, the kinetic energy after scattering, and of the angle of incidence. The key factor is the momentum resolution. PMID:27587131

  2. Highly Effective Polarized Electron Sources Based on Strained Semiconductor Superlattice with Distributed Bragg Reflector

    SciTech Connect

    Gerchikov, L. G.; Kuz'michev, V. V.; Mamaev, Yu. A.; Vasiliev, D. A.; Yashin, Yu. P.; Aulenbacher, K.; Clendenin, J. E.; Maruyama, T.; Mikhrin, V. S.; Ustinov, V. M.; Vasiliev, A. P.; Zhukov, A. E.; Roberts, J. S.

    2008-02-06

    Resonance enhancement of the quantum efficiency of new polarized electron photocathodes based on a short-period strained superlattice structures is reported. The superlattice is a part of an integrated Fabry-Perot optical cavity. We demonstrate that the Fabry-Perot resonator enhances the quantum efficiency by the order of magnitude in the wavelength region of the main polarization maximum. The high structural quality implied by these results points to the very promising application of these photocathodes for spin-polarized electron sources.

  3. Highly Effective Polarized Electron Sources Based on Strained Semiconductor Superlattice with Distributed Bragg Reflector

    SciTech Connect

    Gerchikov, L.G.; Aulenbacher, K.; Clendenin, J.E.; Kuz'michev, V.V.; Mamaev, Yu.A.; Maruyama, T.; Mikhrin, V.S.; Roberts, J.S.; Utstinov, V.M.; Vasiliev, D.A.; Vasiliev, A.P.; Yashin, Yu.P.; Zhukov, A.E.; /St. Petersburg Polytechnic Inst. /Mainz U., Inst. Kernphys. /SLAC /Ioffe Phys. Tech. Inst. /Sheffield U.

    2007-11-28

    Resonance enhancement of the quantum efficiency of new polarized electron photocathodes based on a short-period strained superlattice structures is reported. The superlattice is a part of an integrated Fabry-Perot optical cavity. We demonstrate that the Fabry-Perot resonator enhances the quantum efficiency by the order of magnitude in the wavelength region of the main polarization maximum. The high structural quality implied by these results points to the very promising application of these photocathodes for spin-polarized electron sources.

  4. Electrode fabrication for high-speed polarization mode converter

    NASA Astrophysics Data System (ADS)

    Meng, X.; Zhang, S.; Chen, C.; Poirier, M.; Shepherd, F. R.; Das, S. R.

    2004-05-01

    As part of the development of a traveling wave polarization converter (TWPC), a technique for producing ``T-electrodes'' adjacent to the ridge sidewalls and air bridges has been developed. To maximize the conversion efficiency, the rf electrodes on the etched floor are required to be very close to the ridge sidewalls. In the fabrication of the electrode, patterned seed layer stripes were first put on the etched floor on both sides of the waveguide by a metal lift-off process. Onto this seed layer, the T-electrode was electroplated through a patterned thick photoresist. After resist removal, the unwanted seed layer was stripped off by chemical etch back. Through this multistep process, the electrodes were constructed successfully with the desired proximity to the ridge waveguide. For easy chip assembly, the bond pads were designed to be on the same side of the device. Two long and wide metal air bridges over the ridge waveguide were made to connect the electrode on one side to the bond pads on the other side of the ridge. It was found that the air bridges were easily damaged in the bonding process prior to lap and polish because of the particular device structure, i.e., air bridges being the highest point of the wafer and only a small number of air bridges on the wafer. To protect the air bridge a patterned photoresist layer was applied before the wafer was bonded to a carrier. .

  5. High precision fabrication of polarization insensitive resonant grating filters

    NASA Astrophysics Data System (ADS)

    Boye, R. R.; Peters, D. W.; Wendt, J. R.; Samora, S.; Stevens, J.; Shul, R. J.; Hunker, J.; Kellogg, R. A.; Kemme, S. A.

    2012-03-01

    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.

  6. Time Resolved Spectroscopy of High Field Polars (FUSE 00)

    NASA Technical Reports Server (NTRS)

    Barrett, Paul

    2004-01-01

    The following work has been accomplished: 1) The emission lines of O VI1 and He II were used to produce Doppler tomograms of the plasma emission. 2) An improved interstellar absorption model is being developed for the CIAO spectral fitting program, Sherpa. Use of the earlier version of this model showed it to be inadequate for its purpose. Once this model is working, we intend to complete our analysis of V884 Her and those of other FUSE programs. In addition to the above work, this grant has helped support the following related work: 1) The publication of the paper "Periodicities in the X-ray intensity variations of TV Columbae: an Intermediate Polar" by Rana, V. R., Singh, K. P., Schlegel, E. M., & Barrett, P. 2004, AJ, 126,489, and 2) FUSE data of a possible nova-like variable Ret 1 has been analyzed and shown to contain a hot (37000 deg) white dwarf (WD 0334-6400). The FUV spectrum shows strong absorption lines of C III.

  7. High Efficacy Green LEDs by Polarization Controlled MOVPE

    SciTech Connect

    Wetzel, Christian

    2013-03-31

    Amazing performance in GaInN/GaN based LEDs has become possible by advanced epitaxial growth on a wide variety of substrates over the last decade. An immediate push towards product development and worldwide competition for market share have effectively reduced production cost and generated substantial primary energy savings on a worldwide scale. At all times of the development, this economic pressure forced very fundamental decisions that would shape huge industrial investment. One of those major aspects is the choice of epitaxial growth substrate. The natural questions are to what extend a decision for a certain substrate will limit the ultimate performance and to what extent, the choice of a currently more expensive substrate such as native GaN could overcome any of the remaining performance limitations. Therefore, this project has set out to explore what performance characteristic could be achieved under the utilization of bulk GaN substrate. Our work was guided by the hypotheses that line defects such as threading dislocations in the active region should be avoided and the huge piezoelectric polarization needs to be attenuated – if not turned off – for higher performing LEDs, particularly in the longer wavelength green and deep green portions of the visible spectrum. At their relatively lower performance level, deep green LEDs are a stronger indicator of relative performance improvements and seem particular sensitive to the challenges at hand.

  8. High-intensity, high-brightness polarized and unpolarized beam production in charge-exchange collisions

    SciTech Connect

    Zelenski, A.; Ritter, J.; Zubets, V.; Steski, D.; Atoian, G.; Davydenko, V.; Ivanov, A.; Kolmogorov, A.

    2011-03-28

    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.

  9. High-contrast coherent population trapping based on crossed polarizers method.

    PubMed

    Yano, Yuichiro; Goka, Shigeyoshi

    2014-12-01

    A method based on crossed polarizers to observe high-contrast coherent population trapping (CPT) resonance has been developed. Because crossed polarizers have a simple optical system, our method is suitable for chip-scale atomic clocks (CSACs). In CPT, the Faraday rotation in a linearly polarized light field (lin||lin) was calculated using two pairs of Λ-system models; the spectrum of the Faraday rotation is also estimated. After measuring the contrast and linewidth with the crossed-polarizer method, a comparison of the theoretical model and experimental data showed they were in good agreement. Moreover, the experimental results showed that a high contrast (88.4%) and narrow linewidth (1.15 kHz) resonance could be observed using a Cs gas cell and D1-line verticalcavity surface-emitting laser (VCSEL). PMID:25474771

  10. ABSOLUTE MEASUREMENT OF THE POLARIZATION OF HIGH ENERGY PROTON BEAMS AT RHIC

    SciTech Connect

    MAKDISI,Y.; BRAVAR, A. BUNCE, G. GILL, R.; HUANG, H.; ET AL.

    2007-06-25

    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.

  11. High-brightness liquid-crystal light-valve projector using a new polarization converter

    NASA Astrophysics Data System (ADS)

    Imai, Masao; Sakamoto, Mikio; Kubota, Keiichi; Kato, Yuji; Nishida, Nobuo

    1990-08-01

    A high-brightness liquid crystal light valve (LCLV) projector, in which three amorphous Si TFT-addressed LCLVs are used, has been developed for laroe screen displays. By using a newly developed polarization converter, about twice the brightness has been realized compared to using a conventional sheet polarizer. The polarization converter principle is to efficiently convert an unpolarized light from a light source into a linearly polarized light, used to illuminate a twisted nematic LCLV. The LCLV has 240 x 756 pixels in the 4.3 inch diagonal area. High-brightness full-color images with 120 ft-L brightness have been obtained, when projected onto a 5.0 gain 80 inch diagonal screen using a 300W Xenon arc lamp.

  12. Relativistic Effects and Polarization in Three High-Energy Pulsar Models

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    We present the influence of the special relativistic effects of aberration and light travel time delay on pulsar high-energy lightcurves 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 Crab pulsar. The relative positions of peaks in gamma-ray and radio lightcurves are discussed in detail for the models. We find that the two-pole caustic model can reproduce qualitatively the optical polarization characteristics of the Crab pulsar - fast swings of the position angle and minima in polarization degree associated with both peaks. The anticorrelation between the observed flux and the polarization degree (observed in the optical band also for B0656+14) naturally results from the caustic nature of the peaks which are produced in the model due to the superposition of radiation from many different altitudes, ie. polarized at different angles. The two-pole caustic model also provides an acceptable interpretation of the main features in the Crab's radio profile. Neither the outer gap model nor the polar cap model are able to reproduce the optical polarization data on the Crab. Although the outer gap model is very successful in reproducing the relative positions of gamma-ray and radio peaks in pulse profiles, it can reproduce the high-energy lightcurves only when photon emission from regions very close to the light cylinder is included.

  13. High-speed polarization-sensitive optical coherence tomography for the investigation of tissue birefringence

    NASA Astrophysics Data System (ADS)

    Gulsen, Gultekin; Nalcioglu, Orhan

    2005-04-01

    Polarization-sensitive optical coherence tomography (PSOCT) is an optical imaging modality that is sensitive to the birefringence properties of tissues. Birefringence is related to various biological components and therefore, polarization can provide novel contrast mechanisms for imaging. In this work, we will describe the design of a high-speed polarization sensitive optical coherence tomography system. A broadband source centered at 1310nm with 35nm bandwidth was utilized as the light source. The output power of the source and the resolution of the system were around 20mW and ~20 micrometers, respectively. To achieve high-speed scan, a rapid scan optical delay line (RSOD) was utilized in the reference arm. It provided depth scanning up to 1000 A-scan/s and controlled the carrier frequency of the interference of fridge pattern. Two galvo-mounted mirrors were used for lateral scanning of the beam. The polarization state of the incident light was altered between horizontal and vertical states by using a fast polarization rotator. The combined light from the reference and the sample arms was split into two orthogonal polarization components by a polarizing beam splitter and coupled into two single-mode optical fibers that are connected to the photodiodes. The roundtrip Jones matrix of the sample arm was measured and used to calibrate the measurements of polarization properties of the sample. The elements of the Jones matrix of the sample were calculated by the using the output Jones vectors for the incident polarization states. The performance of the system was evaluated with standard samples such as a quarter-wave plate. The animal studies are currently undertaken to assess the performance of the system in-vivo.

  14. Internal spin structure of the proton from high energy polarized e-p scattering

    SciTech Connect

    Hughes, V.W.; Baum, G.; Bergstroem, M.R.

    1981-02-01

    A review is given of experimental knowledge of the spin dependent structure functions of the proton, which is based on inclusive high energy scattering of longitudinal polarized electrons by longitudinally polarized protons in both the deep inelastic and resonance regions, and includes preliminary results from our most recent SLAC experiment. Implications for scaling, sum rules, models of proton structure, and the hyperfine structure interval in hydrogen are given. Possible future directions of research are indicated.

  15. High-efficiency ultrasmall polarization converter in InP membrane.

    PubMed

    Pello, Josselin; van der Tol, Jos; Keyvaninia, Shahram; van Veldhoven, René; Ambrosius, Huub; Roelkens, Gunther; Smit, Meint

    2012-09-01

    An ultrasmall (<10  μm length) polarization converter in InP membrane is fabricated and characterized. The device relies on the beating between the two eigenmodes of chemically etched triangular waveguides. Measurements show a very high polarization conversion efficiency of >99% with insertion losses of <-1.2  dB at a wavelength of 1.53 μm. Furthermore, our design is found to be broadband and tolerant to dimension variations. PMID:22940999

  16. High physisorption affinity of water molecules to the hydroxylated aluminum oxide (001) surface.

    PubMed

    Kittaka, Shigeharu; Yamaguchi, Keisuke; Takahara, Shuichi

    2012-02-15

    The adsorption mechanism of water on the hydroxylated (001) plane of α-Al(2)O(3) was studied by measuring adsorption isotherms and GCMC simulations. The experimental adsorption isotherms for three α-Al(2)O(3) samples from different sources are typical type II, in which adsorption starts sharply at low pressures, suggesting a high affinity of water to the Al(2)O(3) surface. Water molecules are adsorbed in two registered forms (bilayer structure). In the first form, water is registered at the center of three surface hydroxyl groups by directing a proton of the water. In the second form, a water molecule is adsorbed by bridging two of the first-layer water molecules through hydrogen bonding, by which a hexagonal ring network is constructed over the hydroxylated surface. The network domains are spread over the surface, and their size decreases as the temperature increases. The simulated adsorption isotherms present a characteristic two-dimensional (2D) phase diagram including a 2D critical point at 365K, which is higher than that on the hydroxylated Cr(2)O(3) surface (319 K). This fact substantiates the high affinity of water molecules to the α-Al(2)O(3) surfaces, which enhances the adsorbability originating from higher heat of adsorption. The higher affinity of water molecules to the α-Al(2)O(3) (001) plane is ascribed to the high compatibility of the crystal plane to form a hexagonal ring network of (001) plane of ice Ih. PMID:22178567

  17. Quantifying and Optimizing Single-Molecule Switching Nanoscopy at High Speeds

    PubMed Central

    Lin, Yu; Long, Jane J.; Huang, Fang; Duim, Whitney C.; Kirschbaum, Stefanie; Zhang, Yongdeng; Schroeder, Lena K.; Rebane, Aleksander A.; Velasco, Mary Grace M.; Virrueta, Alejandro; Moonan, Daniel W.; Jiao, Junyi; Hernandez, Sandy Y.; Zhang, Yongli; Bewersdorf, Joerg

    2015-01-01

    Single-molecule switching nanoscopy overcomes the diffraction limit of light by stochastically switching single fluorescent molecules on and off, and then localizing their positions individually. Recent advances in this technique have greatly accelerated the data acquisition speed and improved the temporal resolution of super-resolution imaging. However, it has not been quantified whether this speed increase comes at the cost of compromised image quality. The spatial and temporal resolution depends on many factors, among which laser intensity and camera speed are the two most critical parameters. Here we quantitatively compare the image quality achieved when imaging Alexa Fluor 647-immunolabeled microtubules over an extended range of laser intensities and camera speeds using three criteria – localization precision, density of localized molecules, and resolution of reconstructed images based on Fourier Ring Correlation. We found that, with optimized parameters, single-molecule switching nanoscopy at high speeds can achieve the same image quality as imaging at conventional speeds in a 5–25 times shorter time period. Furthermore, we measured the photoswitching kinetics of Alexa Fluor 647 from single-molecule experiments, and, based on this kinetic data, we developed algorithms to simulate single-molecule switching nanoscopy images. We used this software tool to demonstrate how laser intensity and camera speed affect the density of active fluorophores and influence the achievable resolution. Our study provides guidelines for choosing appropriate laser intensities for imaging Alexa Fluor 647 at different speeds and a quantification protocol for future evaluations of other probes and imaging parameters. PMID:26011109

  18. Quantifying and optimizing single-molecule switching nanoscopy at high speeds.

    PubMed

    Lin, Yu; Long, Jane J; Huang, Fang; Duim, Whitney C; Kirschbaum, Stefanie; Zhang, Yongdeng; Schroeder, Lena K; Rebane, Aleksander A; Velasco, Mary Grace M; Virrueta, Alejandro; Moonan, Daniel W; Jiao, Junyi; Hernandez, Sandy Y; Zhang, Yongli; Bewersdorf, Joerg

    2015-01-01

    Single-molecule switching nanoscopy overcomes the diffraction limit of light by stochastically switching single fluorescent molecules on and off, and then localizing their positions individually. Recent advances in this technique have greatly accelerated the data acquisition speed and improved the temporal resolution of super-resolution imaging. However, it has not been quantified whether this speed increase comes at the cost of compromised image quality. The spatial and temporal resolution depends on many factors, among which laser intensity and camera speed are the two most critical parameters. Here we quantitatively compare the image quality achieved when imaging Alexa Fluor 647-immunolabeled microtubules over an extended range of laser intensities and camera speeds using three criteria - localization precision, density of localized molecules, and resolution of reconstructed images based on Fourier Ring Correlation. We found that, with optimized parameters, single-molecule switching nanoscopy at high speeds can achieve the same image quality as imaging at conventional speeds in a 5-25 times shorter time period. Furthermore, we measured the photoswitching kinetics of Alexa Fluor 647 from single-molecule experiments, and, based on this kinetic data, we developed algorithms to simulate single-molecule switching nanoscopy images. We used this software tool to demonstrate how laser intensity and camera speed affect the density of active fluorophores and influence the achievable resolution. Our study provides guidelines for choosing appropriate laser intensities for imaging Alexa Fluor 647 at different speeds and a quantification protocol for future evaluations of other probes and imaging parameters. PMID:26011109

  19. High-Throughput Universal DNA Curtain Arrays for Single-Molecule Fluorescence Imaging

    PubMed Central

    Gallardo, Ignacio F.; Pasupathy, Praveenkumar; Brown, Maxwell; Manhart, Carol M.; Neikirk, Dean P.; Alani, Eric; Finkelstein, Ilya J.

    2015-01-01

    Single-molecule studies of protein–DNA interactions have shed critical insights into the molecular mechanisms of nearly every aspect of DNA metabolism. The development of DNA curtains—a method for organizing arrays of DNA molecules on a fluid lipid bilayer—has greatly facilitated these studies by increasing the number of reactions that can be observed in a single experiment. However, the utility of DNA curtains is limited by the challenges associated with depositing nanometer-scale lipid diffusion barriers onto quartz microscope slides. Here, we describe a UV lithography-based method for large-scale fabrication of chromium (Cr) features and organization of DNA molecules at these features for high-throughput single-molecule studies. We demonstrate this approach by assembling 792 independent DNA arrays (containing >900 000 DNA molecules) within a single microfluidic flowcell. As a first proof of principle, we track the diffusion of Mlh1-Mlh3—a heterodimeric complex that participates in DNA mismatch repair and meiotic recombination. To further highlight the utility of this approach, we demonstrate a two-lane flowcell that facilitates concurrent experiments on different DNA substrates. Our technique greatly reduces the challenges associated with assembling DNA curtains and paves the way for the rapid acquisition of large statistical data sets from individual single-molecule experiments. PMID:26325477

  20. Invited Article: Polarization diversity and modulation for high-speed optical communications: architectures and capacity

    NASA Astrophysics Data System (ADS)

    Shieh, William; Khodakarami, Hamid; Che, Di

    2016-07-01

    Polarization is one of the fundamental properties of optical waves. To cope with the exponential growth of the Internet traffic, optical communications has advanced by leaps and bounds within the last decade. For the first time, the polarization domain has been extensively explored for high-speed optical communications. In this paper, we discuss the general principle of polarization modulation in both Jones and Stokes spaces. We show that there is no linear optical device capable of transforming an arbitrary input polarization into one that is orthogonal to itself. This excludes the receiver self-polarization diversity architecture by splitting the signal into two branches, and then transferring one of the branches into orthogonal polarization. We next propose a novel Stokes vector (SV) detection architecture using four single-ended photodiodes (PD) that can recover a full set of SV. We then derive a closed-form expression for the information capacity of different SV detection architectures and compare the capacity of our proposed architectures with that of intensity-modulated directly-detected (IM/DD) method. We next study the 3-PD SV detection architecture where a subset of SV is detected, and devise a novel modulation algorithm that can achieve 2-dimensional modulation with the 3-PD detection. By using cost-effective SV receivers, polarization modulation and multiplexing offers a powerful solution for short-reach optical networks where the wavelength domain is quickly exhausted.

  1. Salmonella enterica Invasion of Polarized Epithelial Cells Is a Highly Cooperative Effort

    PubMed Central

    Lorkowski, Martin; Felipe-López, Alfonso; Danzer, Claudia A.; Hansmeier, Nicole

    2014-01-01

    The invasion of polarized epithelial cells by Salmonella enterica requires the cooperative activity of the Salmonella pathogenicity island 1 (SPI1)-encoded type III secretion system (T3SS) and the SPI4-encoded adhesin SiiE. The invasion of polarized cells is more efficient than that of nonpolarized cells, and we observed the formation of clusters of bacteria on infected cells. Here we demonstrate that the invasion of polarized cells is a highly cooperative activity. Using a novel live-cell imaging approach, we visualized the cooperative entry of multiple bacteria into ruffles induced on the apical surfaces of polarized cells. The induction of membrane ruffles by activity of Salmonella enables otherwise noninvasive mutant strains to enter polarized host cells. Bacterial motility and chemotaxis were of lower importance for cooperativity in polarized-cell invasion. We propose that cooperative invasion is a key factor for the very efficient entry into polarized cells and a factor contributing to epithelial damage and intestinal inflammation. PMID:24711567

  2. High spin polarization and the origin of unique ferromagnetic ground state in CuFeSb

    NASA Astrophysics Data System (ADS)

    Sirohi, Anshu; Singh, Chandan K.; Thakur, Gohil S.; Saha, Preetha; Gayen, Sirshendu; Gaurav, Abhishek; Jyotsna, Shubhra; Haque, Zeba; Gupta, L. C.; Kabir, Mukul; Ganguli, Ashok K.; Sheet, Goutam

    2016-06-01

    CuFeSb is isostructural to the ferro-pnictide and chalcogenide superconductors and it is one of the few materials in the family that are known to stabilize in a ferromagnetic ground state. Majority of the members of this family are either superconductors or antiferromagnets. Therefore, CuFeSb may be used as an ideal source of spin polarized current in spin-transport devices involving pnictide and the chalcogenide superconductors. However, for that the Fermi surface of CuFeSb needs to be sufficiently spin polarized. In this paper we report direct measurement of transport spin polarization in CuFeSb by spin-resolved Andreev reflection spectroscopy. From a number of measurements using multiple superconducting tips we found that the intrinsic transport spin polarization in CuFeSb is high (˜47%). In order to understand the unique ground state of CuFeSb and the origin of large spin polarization at the Fermi level, we have evaluated the spin-polarized band structure of CuFeSb through first principles calculations. Apart from supporting the observed 47% transport spin polarization, such calculations also indicate that the Sb-Fe-Sb angles and the height of Sb from the Fe plane are strikingly different for CuFeSb than the equivalent parameters in other members of the same family thereby explaining the origin of the unique ground state of CuFeSb.

  3. High resolution measures of polarization and color of selected lunar areas

    NASA Technical Reports Server (NTRS)

    Riley, L. A.; Hall, J. S.

    1972-01-01

    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 sites and prominent craters. Two dimensional raster scans of colors were obtained for Alphonsus, Aristarchus, and Herodotus. The degree of polarization for any given phase angle appears to be roughly indicative of age. The darker younger mare surface are more highly polarized than the lighter and older mare surfaces, which appear to be more contaminated by lighter material from the highlands or by ray material thrown out from fresh craters. All mare surfaces are more highly polarized than the still older and lighter terra regions surrounding the maria. The very oldest craters are either dark-floored and show polarization characteristics similar to those of the mare surfaces, or if located in the highlands, they are less and less distinguishable from the highland background with greater age, and show the general highland polarization characteristics.

  4. Alkali-metal-atom polarization imaging in high-pressure optical-pumping cells

    NASA Astrophysics Data System (ADS)

    Baranga, A. Ben-Amar; Appelt, S.; Erickson, C. J.; Young, A. R.; Happer, W.

    1998-09-01

    We present a detailed experimental analysis of Rb-polarization imaging in high-pressure gas cells. The Rb vapor in these cells is optically pumped by high-power diode-laser arrays. We present images for high (35 G) and low (4 G) magnetic fields and for different He and Xe buffer-gas mixtures. We demonstrate that high-field imaging provides an absolute measurement of the Rb-polarization distribution in the cell, based on the fact that a spin-temperature distribution of the hyperfine magnetic sublevels is established in high-pressure buffer gases. A survey of various mechanisms that broaden the Rb magnetic-resonance lines is presented. These broadening mechanisms determine the limits of the spatial resolution achievable for images of the Rb-polarization distribution.

  5. Burn depth determination using high-speed polarization-sensitive Mueller optical coherence tomography with continuous polarization modulation

    NASA Astrophysics Data System (ADS)

    Todorović, Miloš; Ai, Jun; Pereda Cubian, David; Stoica, George; Wang, Lihong

    2006-02-01

    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 μm 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.

  6. Theoretical study on the ground state of the polar alkali-metal-barium molecules: potential energy curve and permanent dipole moment.

    PubMed

    Gou, Dezhi; Kuang, Xiaoyu; Gao, Yufeng; Huo, Dongming

    2015-01-21

    In this paper, we systematically investigate the electronic structure for the (2)Σ(+) ground state of the polar alkali-metal-alkaline-earth-metal molecules BaAlk (Alk = Li, Na, K, Rb, and Cs). Potential energy curves and permanent dipole moments (PDMs) are determined using power quantum chemistry complete active space self-consistent field and multi-reference configuration interaction methods. Basic spectroscopic constants are derived from ro-vibrational bound state calculation. From the calculations, it is shown that BaK, BaRb, and BaCs molecules have moderate values of PDM at the equilibrium bond distance (BaK:1.62 D, BaRb:3.32 D, and BaCs:4.02 D). Besides, the equilibrium bond length (4.93 Å and 5.19 Å) and dissociation energy (0.1825 eV and 0.1817 eV) for the BaRb and BaCs are also obtained. PMID:25612710

  7. Theoretical study on the ground state of the polar alkali-metal-barium molecules: Potential energy curve and permanent dipole moment

    SciTech Connect

    Gou, Dezhi; Kuang, Xiaoyu Gao, Yufeng; Huo, Dongming

    2015-01-21

    In this paper, we systematically investigate the electronic structure for the {sup 2}Σ{sup +} ground state of the polar alkali-metal-alkaline-earth-metal molecules BaAlk (Alk = Li, Na, K, Rb, and Cs). Potential energy curves and permanent dipole moments (PDMs) are determined using power quantum chemistry complete active space self-consistent field and multi-reference configuration interaction methods. Basic spectroscopic constants are derived from ro-vibrational bound state calculation. From the calculations, it is shown that BaK, BaRb, and BaCs molecules have moderate values of PDM at the equilibrium bond distance (BaK:1.62 D, BaRb:3.32 D, and BaCs:4.02 D). Besides, the equilibrium bond length (4.93 Å and 5.19 Å) and dissociation energy (0.1825 eV and 0.1817 eV) for the BaRb and BaCs are also obtained.

  8. Theoretical study on the ground state of the polar alkali-metal-barium molecules: Potential energy curve and permanent dipole moment

    NASA Astrophysics Data System (ADS)

    Gou, Dezhi; Kuang, Xiaoyu; Gao, Yufeng; Huo, Dongming

    2015-01-01

    In this paper, we systematically investigate the electronic structure for the 2Σ+ ground state of the polar alkali-metal-alkaline-earth-metal molecules BaAlk (Alk = Li, Na, K, Rb, and Cs). Potential energy curves and permanent dipole moments (PDMs) are determined using power quantum chemistry complete active space self-consistent field and multi-reference configuration interaction methods. Basic spectroscopic constants are derived from ro-vibrational bound state calculation. From the calculations, it is shown that BaK, BaRb, and BaCs molecules have moderate values of PDM at the equilibrium bond distance (BaK:1.62 D, BaRb:3.32 D, and BaCs:4.02 D). Besides, the equilibrium bond length (4.93 Å and 5.19 Å) and dissociation energy (0.1825 eV and 0.1817 eV) for the BaRb and BaCs are also obtained.

  9. Development of a high average current polarized electron source with long cathode operational lifetime

    SciTech Connect

    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

    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.

  10. Signatures of symmetry and electronic structure in high-order harmonic generation in polyatomic molecules

    SciTech Connect

    Wong, M. C. H.; Brichta, J.-P.; Bhardwaj, V. R.

    2010-06-15

    We report detailed measurements of high-order harmonic generation in chloromethane molecules (CCl{sub 4}, CHCl{sub 3}, and CH{sub 2}Cl{sub 2}) to show that fingerprints of symmetry and electronic structure can be decoded from high-order harmonic generation even in complex randomly oriented molecules. In our measurements, orbital symmetries of these molecules are manifested as both extended harmonic cutoffs and a local minimum in the ellipticity dependence of the cut-off harmonics, suggesting the occurrence of quantum interferences during ionization. The harmonic spectra exhibit distinct interference minima at {approx}42 and {approx}60 eV. We attribute the former to the Cooper minimum in the photoionization cross section and the latter to intramolecular interference during the recombination process.

  11. Permeation of protons, potassium ions, and small polar molecules through phospholipid bilayers as a function of membrane thickness.

    PubMed Central

    Paula, S; Volkov, A G; Van Hoek, A N; Haines, T H; Deamer, D W

    1996-01-01

    Two mechanisms have been proposed to account for solute permeation of lipid bilayers. Partitioning into the hydrophobic phase of the bilayer, followed by diffusion, is accepted by many for the permeation of water and other small neutral solutes, but transient pores have also been proposed to account for both water and ionic solute permeation. These two mechanisms make distinctively different predictions about the permeability coefficient as a function of bilayer thickness. Whereas the solubility-diffusion mechanism predicts only a modest variation related to bilayer thickness, the pore model predicts an exponential relationship. To test these models, we measured the permeability of phospholipid bilayers to protons, potassium ions, water, urea, and glycerol. Bilayers were prepared as liposomes, and thickness was varied systematically by using unsaturated lipids with chain lengths ranging from 14 to 24 carbon atoms. The permeability coefficient of water and neutral polar solutes displayed a modest dependence on bilayer thickness, with an approximately linear fivefold decrease as the carbon number varied from 14 to 24 atoms. In contrast, the permeability to protons and potassium ions decreased sharply by two orders of magnitude between 14 and 18 carbon atoms, and leveled off, when the chain length was further extended to 24 carbon atoms. The results for water and the neutral permeating solutes are best explained by the solubility-diffusion mechanism. The results for protons and potassium ions in shorter-chain lipids are consistent with the transient pore model, but better fit the theoretical line predicted by the solubility-diffusion model at longer chain lengths. PMID:8770210

  12. Permeation of protons, potassium ions, and small polar molecules through phospholipid bilayers as a function of membrane thickness

    NASA Technical Reports Server (NTRS)

    Paula, S.; Volkov, A. G.; Van Hoek, A. N.; Haines, T. H.; Deamer, D. W.

    1996-01-01

    Two mechanisms have been proposed to account for solute permeation of lipid bilayers. Partitioning into the hydrophobic phase of the bilayer, followed by diffusion, is accepted by many for the permeation of water and other small neutral solutes, but transient pores have also been proposed to account for both water and ionic solute permeation. These two mechanisms make distinctively different predictions about the permeability coefficient as a function of bilayer thickness. Whereas the solubility-diffusion mechanism predicts only a modest variation related to bilayer thickness, the pore model predicts an exponential relationship. To test these models, we measured the permeability of phospholipid bilayers to protons, potassium ions, water, urea, and glycerol. Bilayers were prepared as liposomes, and thickness was varied systematically by using unsaturated lipids with chain lengths ranging from 14 to 24 carbon atoms. The permeability coefficient of water and neutral polar solutes displayed a modest dependence on bilayer thickness, with an approximately linear fivefold decrease as the carbon number varied from 14 to 24 atoms. In contrast, the permeability to protons and potassium ions decreased sharply by two orders of magnitude between 14 and 18 carbon atoms, and leveled off, when the chain length was further extended to 24 carbon atoms. The results for water and the neutral permeating solutes are best explained by the solubility-diffusion mechanism. The results for protons and potassium ions in shorter-chain lipids are consistent with the transient pore model, but better fit the theoretical line predicted by the solubility-diffusion model at longer chain lengths.

  13. Quantum interference during high-order harmonic generation from aligned molecules

    NASA Astrophysics Data System (ADS)

    Kanai, Tsuneto; Minemoto, Shinichirou; Sakai, Hirofumi

    2005-05-01

    High-order harmonic generation (HHG) from atoms and molecules offers potential application as a coherent ultrashort radiation source in the extreme ultraviolet and soft X-ray regions. In the three-step model of HHG, an electron tunnels out from the atom and may recombine with the parent ion (emitting a high-energy photon) after undergoing laser-driven motion in the continuum. Aligned molecules can be used to study quantum phenomena in HHG associated with molecular symmetries; in particular, simultaneous observations of both ion yields and harmonic signals under the same conditions serve to disentangle the contributions from the ionization and recombination processes. Here we report evidence for quantum interference of electron de Broglie waves in the recombination process of HHG from aligned CO2 molecules. The interference takes place within a single molecule and within one optical cycle. Characteristic modulation patterns of the harmonic signals measured as a function of the pump-probe delay are explained with simple formulae determined by the valence orbital of the molecules. We propose that simultaneous observations of both ion yields and harmonic signals can serve as a new route to probe the instantaneous structure of molecular systems.

  14. Quantum interference during high-order harmonic generation from aligned molecules.

    PubMed

    Kanai, Tsuneto; Minemoto, Shinichirou; Sakai, Hirofumi

    2005-05-26

    High-order harmonic generation (HHG) from atoms and molecules offers potential application as a coherent ultrashort radiation source in the extreme ultraviolet and soft X-ray regions. In the three-step model of HHG, an electron tunnels out from the atom and may recombine with the parent ion (emitting a high-energy photon) after undergoing laser-driven motion in the continuum. Aligned molecules can be used to study quantum phenomena in HHG associated with molecular symmetries; in particular, simultaneous observations of both ion yields and harmonic signals under the same conditions serve to disentangle the contributions from the ionization and recombination processes. Here we report evidence for quantum interference of electron de Broglie waves in the recombination process of HHG from aligned CO2 molecules. The interference takes place within a single molecule and within one optical cycle. Characteristic modulation patterns of the harmonic signals measured as a function of the pump-probe delay are explained with simple formulae determined by the valence orbital of the molecules. We propose that simultaneous observations of both ion yields and harmonic signals can serve as a new route to probe the instantaneous structure of molecular systems. PMID:15917803

  15. Tackling the bottleneck in bacterial signal transduction research: high-throughput identification of signal molecules.

    PubMed

    Krell, Tino

    2015-05-01

    Signal transduction processes are typically initiated by the interaction of signal molecules with sensor domains. The current lack of information on the signal molecules that feed into regulatory circuits forms a major bottleneck that hampers the understanding of regulatory processes. McKellar et al. report a high-throughput approach for the identification of signal molecules, which is based on thermal shift assays of recombinant sensor domains in the absence and presence of compounds from commercially available ligand collections. Initial binding studies with the sensor domain of the PctA chemoreceptor of Pseudomonas aeruginosa showed a close match between thermal shift assay results and microcalorimetric studies reported previously. Using thermal shift assays the authors then identify signals that bind to three chemoreceptors of the kiwifruit pathogen P. syringae pv. Actinidiae NZ-V13. Microcalorimetric binding studies and chemotaxis assays have validated the relevance of these ligands. The power of this technique lies in the combination of a high-throughput analytical tool with commercially available compound collections. The approach reported is universal since it can be employed to identify signal molecules to any type of sensor domain. There is no doubt that this technique will facilitate the identification of many signal molecules in future years. PMID:25708679

  16. Axion-like particle effects on the polarization of cosmic high-energy gamma sources

    SciTech Connect

    Bassan, Nicola; Mirizzi, Alessandro; Roncadelli, Marco E-mail: alessandro.mirizzi@desy.de

    2010-05-01

    Various satellite-borne missions are being planned to measure the polarization of a large number of gamma-ray bursts (GRBs). We show that the polarization pattern resulting from the current models of GRB emission can be drastically modified by the existence of very light axion-like particles (ALPs), which are predicted by many extensions of the Standard Model of particle physics. Basically, the propagation of photons emitted by a GRB through cosmic magnetic fields with a domain-like structure induces photon-ALP mixing, which is expected to produce a strong modification of the initial photon polarization. Because of the random orientation of the magnetic field in each domain, this effect strongly depends on the orientation of the line of sight. As a consequence, photon-ALP conversion considerably broadens the initial polarization distribution. Searching for such a peculiar feature through future high-statistics polarimetric measurements therefore offers a new opportunity to discover very light ALPs.

  17. Transport of Mars atmospheric water into high northern latitudes during a polar warming

    NASA Technical Reports Server (NTRS)

    Barnes, J. R.; Hollingsworth, J. L.

    1988-01-01

    Several numerical experiments were conducted with a simplified tracer transport model in order to attempt to examine the poleward transport of Mars atmospheric water during a polar warming like that which occurred during the winter solstice dust storm of 1977. The flow for the transport experiments was taken from numerical simulations with a nonlinear beta-plane dynamical model. Previous studies with this model have demonstrated that a polar warming having essential characteristics like those observed during the 1977 dust storm can be produced by a planetary wave mechanism analogous to that responsible for terrestrial sudden stratospheric warmings. Several numerical experiments intended to simulate water transport in the absence of any condensation were carried out. These experiments indicate that the flow during a polar warming can transport very substantial amounts of water to high northern latitudes, given that the water does not condense and fall out before reaching the polar region.

  18. Design of a polarization-insensitive superconducting nanowire single photon detector with high detection efficiency.

    PubMed

    Zheng, Fan; Xu, Ruiying; Zhu, Guanghao; Jin, Biaobing; Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng

    2016-01-01

    Superconducting nanowire single photon detectors (SNSPDs) deliver superior performance over their competitors in the near-infrared regime. However, these detectors have an intrinsic polarization dependence on the incident wave because of their one-dimensional meander structure. In this paper, we propose an approach to eliminate the polarization sensitivity of SNSPDs by using near-field optics to increase the absorption of SNSPDs under transverse magnetic (TM) illumination. In addition, an optical cavity is added to our SNSPD to obtain nearly perfect absorption of the incident wave. Numerical simulations show that the maximum absorption of a designed SNSPD can reach 96% at 1550 nm, and indicate that the absorption difference between transverse electric (TE) and TM polarization is less than 0.5% across a wavelength window of 300 nm. Our work provides the first demonstration of the possibility of designing a polarization-insensitive and highly efficient SNSPD without performing device symmetry improvements. PMID:26948672

  19. Design of a polarization-insensitive superconducting nanowire single photon detector with high detection efficiency

    PubMed Central

    Zheng, Fan; Xu, Ruiying; Zhu, Guanghao; Jin, Biaobing; Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng

    2016-01-01

    Superconducting nanowire single photon detectors (SNSPDs) deliver superior performance over their competitors in the near-infrared regime. However, these detectors have an intrinsic polarization dependence on the incident wave because of their one-dimensional meander structure. In this paper, we propose an approach to eliminate the polarization sensitivity of SNSPDs by using near-field optics to increase the absorption of SNSPDs under transverse magnetic (TM) illumination. In addition, an optical cavity is added to our SNSPD to obtain nearly perfect absorption of the incident wave. Numerical simulations show that the maximum absorption of a designed SNSPD can reach 96% at 1550 nm, and indicate that the absorption difference between transverse electric (TE) and TM polarization is less than 0.5% across a wavelength window of 300 nm. Our work provides the first demonstration of the possibility of designing a polarization-insensitive and highly efficient SNSPD without performing device symmetry improvements. PMID:26948672

  20. Generation of circularly polarized high harmonic radiation using a transmission multilayer quarter waveplate.

    PubMed

    Schmidt, Jürgen; Guggenmos, Alexander; Hofstetter, Michael; Chew, Soo Hoon; Kleineberg, Ulf

    2015-12-28

    High harmonic radiation is meanwhile nearly extensively used for the spectroscopic investigation of electron dynamics with ultimate time resolution. The majority of high harmonic beamlines provide linearly polarized radiation created in a gas target. However, circular polarization greatly extends the spectroscopic possibilities for high harmonics, especially in the analysis of samples with chirality or prominent spin polarization. We produced a free-standing multilayer foil as a transmission EUV quarter waveplate and applied it for the first time to high harmonic radiation. We measured a broadband (4.6 eV FWHM) ellipticity of 75% at 66 eV photon energy with a transmission efficiency of 5%. The helicity is switchable and the ellipticity can be adjusted to lower values by angle tuning. As a single element it can be easily integrated in any existing harmonic beamline without major changes. PMID:26832020

  1. High Latitude Meridional Flow on the Sun May Explain North-South Polar Field Asymmetry

    NASA Technical Reports Server (NTRS)

    Kosak, Katie; Upton, Lisa; Hathaway, David

    2012-01-01

    We measured the flows of magnetic elements on the Sun at very high latitudes by analyzing magnetic images from the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. Magnetic maps constructed using a fixed, and north-south symmetric, meridional flow profile give weaker than observed polar fields in the North and stronger than observed polar fields in the South during the decline of Cycle 23 and rise of Cycle 24. Our measurements of the meridional flow at high latitudes indicate systematic north-south differences. In the fall of 2010 (when the North Pole was most visible), there was a strong flow in the North while in the spring of 2011 (when the South Pole was most visible) the flow there was weaker. With these results, we have a possible solution to this polar field asymmetry. The weaker flow in the South should keep the polar fields from becoming too strong while the stronger flow in the North should strengthen the field there. In order to gain a better understanding of the Solar Cycle and magnetic flux transport on the Sun, we need further observations and analyses of the Sun s polar regions in general and the polar meridional flow in particular.

  2. High Latitude Meridional Flow on the Sun May Explain North-South Polar Field Asymmetry

    NASA Technical Reports Server (NTRS)

    Kosak, Katie; Upton, Lisa; Hathaway, David

    2012-01-01

    We measured the flows of magnetic elements on the Sun at very high latitudes by analyzing magnetic images from the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. Magnetic maps constructed using a fixed, and north-south symmetric, meridional flow profile give weaker than observed polar fields in the North and stronger than observed polar fields in the South during the decline of Cycle 23 and rise of Cycle 24. Our measurements of the meridional flow at high latitudes indicate systematic north-south differences. There was a strong flow in the North while the flow in the South was weaker. With these results, we have a possible solution to the polar field asymmetry. The weaker flow in the South should keep the polar fields from becoming too strong while the stronger flow in the North should strengthen the field there. In order to gain a better understanding of the Solar Cycle and magnetic flux transport on the Sun, we need further observations and analyses of the Sun's polar regions in general and the polar meridonal flow in particular.

  3. High Latitude Meridional Flow on the Sun May Explain North-South Polar Field Asymmetry

    NASA Technical Reports Server (NTRS)

    Kosak, Katie; Upton, Lisa; Hathaway, David

    2012-01-01

    We measured the flows of magnetic elements on the Sun at very high latitudes by analyzing magnetic images from the Helioseismic and Magnetic Imager (HMI) on the NASA Solar Dynamics Observatory (SDO) Mission. Magnetic maps constructed using a fixed, and north ]south symmetric, meridional flow profile give weaker than observed polar fields in the North and stronger than observed polar fields in the South during the decline of Cycle 23 and rise of Cycle 24. Our measurements of the meridional flow at high latitudes indicate systematic north ]south differences. There was a strong flow in the North while the flow in the South was weaker. With these results, we have a possible solution to the polar field asymmetry. The weaker flow in the South should keep the polar fields from becoming too strong while the stronger flow in the North should strengthen the field there. In order to gain a better understanding of the Solar Cycle and magnetic flux transport on the Sun, we need further observations and analyses of the Sun fs polar regions in general and the polar meridional flow in particular

  4. High resolution non-hydrostatic GCM simulations of Venus polar vortices

    NASA Astrophysics Data System (ADS)

    Rodin, Alexander V.; Orlov, Konstantin; Mingalev, Igor

    Non-hydrostatic general circulation model of the Venus atmosphere is capable of reproducing both superrotatoin and subsolar-antisolar circulation, providing proper parameterization of the peculiar heat balance. Using high resolution (0.7 (o) in longitude and latitude, 250 m in height) simulations from the bottom to 120 km, we explore the response of the circulation system to perturbation of heating and cooling rates in the polar regions. It is shown that diurnal tide results in off-axis displacement of the polar vortex external part at the upper cloud level, consistent with the patterns retrieved from cloud tracking observations. On the other hand, minor (3 (o) -7 (o) ) displacement of the polar vortex central part constrains the diurnal variations of the heating/cooling rates within main cloud deck. Based on the recently developed radiative transfer code, we simulate heat balance in the polar Venus atmosphere, that results in realistic circulation pattern. It is shown that Hadley cell circulation provides extra heating above the clouds, resulting in the effective damping of superrotation and development of subsolar-antisolar circulation at higher altitudes. In turin high slant opacity of the polar atmosphere within the clouds provides the effective cooling near the pole, that causes non-hydrostatic downwelling flow, manifested as a core of the observed polar vortex. The work has been supported by the Ministry of Education and Science of Russian Federation grant #11.G34.31.0074

  5. Polarization-insensitive optical gain characteristics of highly stacked InAs/GaAs quantum dots

    SciTech Connect

    Kita, Takashi; Suwa, Masaya; Kaizu, Toshiyuki; Harada, Yukihiro

    2014-06-21

    The polarized optical gain characteristics of highly stacked InAs/GaAs quantum dots (QDs) with a thin spacer layer fabricated on an n{sup +}-GaAs (001) substrate were studied in the sub-threshold gain region. Using a 4.0-nm-thick spacer layer, we realized an electronically coupled QD superlattice structure along the stacking direction, which enabled the enhancement of the optical gain of the [001] transverse-magnetic (TM) polarization component. We systematically studied the polarized electroluminescence properties of laser devices containing 30 and 40 stacked InAs/GaAs QDs. The net modal gain was analyzed using the Hakki-Paoli method. Owing to the in-plane shape anisotropy of QDs, the polarization sensitivity of the gain depends on the waveguide direction. The gain showing polarization isotropy between the TM and transverse-electric polarization components is high for the [110] waveguide structure, which occurs for higher amounts of stacked QDs. Conversely, the isotropy of the [−110] waveguide is easily achieved even if the stacking is relatively low, although the gain is small.

  6. Update on High-Resolution Geodetically Controlled LROC Polar Mosaics

    NASA Astrophysics Data System (ADS)

    Archinal, B.; Lee, E.; Weller, L.; Richie, J.; Edmundson, K.; Laura, J.; Robinson, M.; Speyerer, E.; Boyd, A.; Bowman-Cisneros, E.; Wagner, R.; Nefian, A.

    2015-10-01

    We describe progress on high-resolution (1 m/pixel) geodetically controlled LROC mosaics of the lunar poles, which can be used for locating illumination resources (for solar power or cold traps) or landing site and surface operations planning.

  7. Complete calculation of electroweak corrections for polarized Møller scattering at high energies

    NASA Astrophysics Data System (ADS)

    Zykunov, V. A.

    2009-09-01

    A complete calculation of electroweak radiative corrections to observables of polarized Møller scattering at high energies was performed. This calculation took explicitly into account contributions caused by hard bremsstrahlung. A FORTRAN code that permitted including radiative corrections to high-energy Møller scattering under arbitrary electron-detection conditions was written. It was shown that the electroweak corrections caused by hard bremsstrahlung were rather strongly dependent on the choice of experimental cuts and changed substantially the polarization asymmetry in the region of high energies and over a broad interval of scattering angles.

  8. High-power radially polarized Yb:YAG thin-disk laser with high efficiency.

    PubMed

    Ahmed, Marwan Abdou; Haefner, Matthias; Vogel, Moritz; Pruss, Christof; Voss, Andreas; Osten, Wolfgang; Graf, Thomas

    2011-03-14

    Radially polarized beams with an output power of 275 W, M2=2.3 and an efficiency of about 52.5% were generated from an Yb:YAG thin-disk laser. An intra-cavity circular resonant waveguide grating was used as a polarization selective mirror inside the laser cavity. We report on the design and the fabrication using a scanning beam interference lithography system and discuss the calculated and measured performances of the presented polarizing grating mirrors. PMID:21445144

  9. Rigid DNA beams for high-resolution single-molecule mechanics.

    PubMed

    Pfitzner, Emanuel; Wachauf, Christian; Kilchherr, Fabian; Pelz, Benjamin; Shih, William M; Rief, Matthias; Dietz, Hendrik

    2013-07-22

    Bridging the gap: Rigid DNA linkers (blue, see picture) between microspheres (green) for high-resolution single-molecule mechanical experiments were constructed using DNA origami. The resulting DNA helical bundles greatly reduce the noise generated in studies of conformation changes using optical tweezers and were applied to study small DNA secondary structures. PMID:23794413

  10. High-resolution electrohydrodynamic jet printing of small-molecule organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Kim, Kukjoo; Kim, Gyeomuk; Lee, Bo Ram; Ji, Sangyoon; Kim, So-Yun; An, Byeong Wan; Song, Myoung Hoon; Park, Jang-Ung

    2015-08-01

    The development of alternative organic light-emitting diode (OLED) fabrication technologies for high-definition and low-cost displays is an important research topic as conventional fine metal mask-assisted vacuum evaporation has reached its limit to reduce pixel sizes and manufacturing costs. Here, we report an electrohydrodynamic jet (e-jet) printing method to fabricate small-molecule OLED pixels with high resolution (pixel width of 5 μm), which significantly exceeds the resolutions of conventional inkjet or commercial OLED display pixels. In addition, we print small-molecule emitting materials which provide a significant advantage in terms of device efficiency and lifetime compared to those with polymers.The development of alternative organic light-emitting diode (OLED) fabrication technologies for high-definition and low-cost displays is an important research topic as conventional fine metal mask-assisted vacuum evaporation has reached its limit to reduce pixel sizes and manufacturing costs. Here, we report an electrohydrodynamic jet (e-jet) printing method to fabricate small-molecule OLED pixels with high resolution (pixel width of 5 μm), which significantly exceeds the resolutions of conventional inkjet or commercial OLED display pixels. In addition, we print small-molecule emitting materials which provide a significant advantage in terms of device efficiency and lifetime compared to those with polymers. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr03034j

  11. Single molecule tracking fluorescence microscopy in mitochondria reveals highly dynamic but confined movement of Tom40

    NASA Astrophysics Data System (ADS)

    Kuzmenko, Anton; Tankov, Stoyan; English, Brian P.; Tarassov, Ivan; Tenson, Tanel; Kamenski, Piotr; Elf, Johan; Hauryliuk, Vasili

    2011-12-01

    Tom40 is an integral protein of the mitochondrial outer membrane, which as the central component of the Translocase of the Outer Membrane (TOM) complex forms a channel for protein import. We characterize the diffusion properties of individual Tom40 molecules fused to the photoconvertable fluorescent protein Dendra2 with millisecond temporal resolution. By imaging individual Tom40 molecules in intact isolated yeast mitochondria using photoactivated localization microscopy with sub-diffraction limited spatial precision, we demonstrate that Tom40 movement in the outer mitochondrial membrane is highly dynamic but confined in nature, suggesting anchoring of the TOM complex as a whole.

  12. Single molecule tracking fluorescence microscopy in mitochondria reveals highly dynamic but confined movement of Tom40

    PubMed Central

    Kuzmenko, Anton; Tankov, Stoyan; English, Brian P.; Tarassov, Ivan; Tenson, Tanel; Kamenski, Piotr; Elf, Johan; Hauryliuk, Vasili

    2011-01-01

    Tom40 is an integral protein of the mitochondrial outer membrane, which as the central component of the Translocase of the Outer Membrane (TOM) complex forms a channel for protein import. We characterize the diffusion properties of individual Tom40 molecules fused to the photoconvertable fluorescent protein Dendra2 with millisecond temporal resolution. By imaging individual Tom40 molecules in intact isolated yeast mitochondria using photoactivated localization microscopy with sub-diffraction limited spatial precision, we demonstrate that Tom40 movement in the outer mitochondrial membrane is highly dynamic but confined in nature, suggesting anchoring of the TOM complex as a whole. PMID:22355710

  13. Small-Molecule High-Throughput Screening Utilizing Xenopus Egg Extract

    PubMed Central

    Broadus, Matthew R.; Yew, P. Renee; Hann, Stephen R.; Lee, Ethan

    2015-01-01

    Screens for small-molecule modulators of biological pathways typically utilize cultured cell lines, purified proteins, or, recently, model organisms (e.g., zebrafish, Drosophila, C. elegans). Herein, we describe a method for using Xenopus laevis egg extract, a biologically active and highly tractable cell-free system that recapitulates a legion of complex chemical reactions found in intact cells. Specifically, we focus on the use of a luciferase-based fusion system to identify small-molecule modulators that affect protein turnover. PMID:25618336

  14. High-precision spectroscopy of ultracold molecules in an optical lattice

    NASA Astrophysics Data System (ADS)

    McGuyer, B. H.; McDonald, M.; Iwata, G. Z.; Tarallo, M. G.; Grier, A. T.; Apfelbeck, F.; Zelevinsky, T.

    2015-05-01

    The study of ultracold molecules tightly trapped in an optical lattice can expand the frontier of precision measurement and spectroscopy, and provide a deeper insight into molecular and fundamental physics. Here we create, probe, and image microkelvin 88Sr2 molecules in a lattice, and demonstrate precise measurements of molecular parameters as well as coherent control of molecular quantum states using optical fields. We discuss the sensitivity of the system to dimensional effects, a new bound-to-continuum spectroscopy technique for highly accurate binding energy measurements, and prospects for new physics with this rich experimental system.

  15. Generating Polarized High-Brightness Muon Beams With High-Energy Gammas

    SciTech Connect

    Yakimenko, Vitaly

    2009-01-22

    Hadron colliders are impractical at very high energies as effective interaction energy is a fraction of the energies of the beams and luminosity must rise as energy squared. Further, the prevailing gluon-gluon background radiation makes it difficult to sort out events. e{sup +}e{sup -} colliders, on other hand, are constrained at TeV energies by beamstrahlung radiation and also by cost as long linacs are required to avoid synchrotron radiation in the rings. A muon collider will have the same advantages in energy reach as an e{sup +}e{sup -} collider, but without prohibitive beamstrahlung- and synchrotron- radiation. Generation of the high-brightness polarized muon ({mu}{sup -}{mu}{sup +}) beams through gamma conversion into pairs in the nuclei field is considered in this paper. The dominant effect in the interaction of the high-energy photons with the solid target will be the production of electron-positron pairs. The low-phase space of the resulting muon beams adequately compensates for the small probability of generating a {mu}{sup -}{mu}{sup +} pair.

  16. Selective Metal-Free Hydrosilylation of CO2 Catalyzed by Triphenylborane in Highly Polar, Aprotic Solvents.

    PubMed

    Mukherjee, Debabrata; Sauer, Daniel F; Zanardi, Alessandro; Okuda, Jun

    2016-06-01

    Triphenylborane (BPh3 ) in highly polar, aprotic solvents catalyzes hydrosilylation of CO2 effectively under mild conditions to provide silyl formates with high chemoselectivity (>95 %) and without over-reduction. This system also promotes reductive hydrosilylation of tertiary amides as well as dehydrogenative coupling of silane with alcohols. PMID:27028161

  17. Nonsequential double ionization of molecules

    SciTech Connect

    Prauzner-Bechcicki, Jakub S.; Sacha, Krzysztof; Zakrzewski, Jakub; Eckhardt, Bruno

    2005-03-01

    Double ionization of diatomic molecules by short linearly polarized laser pulses is analyzed. We consider the final stage of the ionization process, that is the decay of a highly excited two electron molecule, which is formed after rescattering. The saddles of the effective adiabatic potential energy close to which simultaneous escape of electrons takes place are identified. Numerical simulations of the ionization of molecules show that the process can be dominated by either sequential or nonsequential events. In order to increase the ratio of nonsequential to sequential ionizations very short laser pulses should be applied.

  18. High-throughput single-molecule fluorescence spectroscopy using parallel detection

    PubMed Central

    Michalet, X.; Colyer, R. A.; Scalia, G.; Kim, T.; Levi, Moran; Aharoni, Daniel; Cheng, Adrian; Guerrieri, F.; Arisaka, Katsushi; Millaud, Jacques; Rech, I.; Resnati, D.; Marangoni, S.; Gulinatti, A.; Ghioni, M.; Tisa, S.; Zappa, F.; Cova, S.; Weiss, S.

    2011-01-01

    Solution-based single-molecule fluorescence spectroscopy is a powerful new experimental approach with applications in all fields of natural sciences. The basic concept of this technique is to excite and collect light from a very small volume (typically femtoliter) and work in a concentration regime resulting in rare burst-like events corresponding to the transit of a single-molecule. Those events are accumulated over time to achieve proper statistical accuracy. Therefore the advantage of extreme sensitivity is somewhat counterbalanced by a very long acquisition time. One way to speed up data acquisition is parallelization. Here we will discuss a general approach to address this issue, using a multispot excitation and detection geometry that can accommodate different types of novel highly-parallel detector arrays. We will illustrate the potential of this approach with fluorescence correlation spectroscopy (FCS) and single-molecule fluorescence measurements obtained with different novel multipixel single-photon counting detectors. PMID:21625288

  19. Speckle noise reduction in high speed polarization sensitive spectral domain optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Götzinger, Erich; Pircher, Michael; Baumann, Bernhard; Schmoll, Tilman; Sattmann, Harald; Leitgeb, Rainer A.; Hitzenberger, Christoph K.

    2011-07-01

    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.

  20. Plasma density enhancements in the high-altitude polar cap region observed on Akebono

    NASA Astrophysics Data System (ADS)

    Ichikawa, Yoh-ichi; Abe, Takumi; Yau, Andrew W.

    2002-05-01

    The plasma density in the polar cap ionosphere is generally low (<103 cm-3 above 3000 km), mainly because of plasma escape from the ionosphere along open magnetic-field lines. The Akebono satellite occasionally encounters regions of unusually high plasma density (>=103 cm-3) above 4000 km altitude, in which the thermal plasma exhibits a distinctively low electron temperature (<3000 K) and low parallel ion drift velocity (<=1 km/s). Such events are almost always observed on the dusk side. The occurrence of low electron temperature and ion drift velocity appears to suggest the antisunward convection of high-density plasma into the polar cap, and the decrease in electron temperature due to the disruption of field-aligned heat flux in the high-altitude polar cap.

  1. Conductivity Variation Observed by Polarization and Depolarization Current Measurements of High-Voltage Equipment Insulation System

    NASA Astrophysics Data System (ADS)

    Jamail, Nor Akmal Mohd; Piah, Mohamed Afendi Mohamed; Muhamad, Nor Asiah

    2012-09-01

    Nondestructive and time domain dielectric measurement techniques such as polarization and depolarization current (PDC) measurements have recently been widely used as a potential tool for determining high-voltage insulation conditions by analyzing the insulation conductivity. The variation in the conductivity of an insulator was found to depend on several parameters: the difference between the polarization and depolarization currents, geometric capacitance, and the relative permittivity of the insulation material. In this paper the conductivities of different types of oil-paper insulation material are presented. The insulation conductivities of several types of electrical apparatus were simulated using MATLAB. Conductivity insulation was found to be high at high polarizations and at the lowest depolarization current. It was also found to increase with increasing relative permittivity as well as with decreasing geometric capacitance of the insulating material.

  2. Ultrafast ionization and fragmentation dynamics of molecules at high x-ray intensity

    NASA Astrophysics Data System (ADS)

    Son, Sang-Kil

    2016-05-01

    X-ray free-electron lasers (XFEL) open a new era in science and technology, offering many unique opportunities that have not been conceivable with conventional light sources. Because of their very high x-ray photon fluence within very short pulse duration, materials interacting with XFEL undergo significant radiation damage -- they possibly become highly ionized and then explode. To comprehend underlying physics, it is crucial to understand detailed ionization and fragmentation dynamics of atoms and molecules during intense XFEL pulses. We have developed the XMOLECULE toolkit to describe molecular x-ray-induced processes and to simulate radiation damage dynamics of molecules. In this talk, I will present a theoretical framework of XFEL-matter interaction, namely x-ray multiphoton absorption. Then I will discuss recent results of ultrafast x-ray-induced explosion of methyl iodide (CH3 I) molecules. Charge state distribution and kinetic energy releases of fragments are calculated to probe ionization and fragmentation dynamics, and compared with recent experimental results. It will be demonstrated that ionization of heavy-atom-containing molecules at high x-ray intensity is much enhanced in comparison with the isolated atomic case, due to ultrafast charge rearrangement during x-ray multiphoton absorption.

  3. New Method for Production of High-Energy Neutral Molecules of Reactive Gases

    NASA Astrophysics Data System (ADS)

    Metel, Alexander; Bolbukov, Vasily; Volosova, Marina; Grigoriev, Sergei; Melnik, Yury

    2015-09-01

    For the surface modification of dielectric substrates by reactive gas molecules with energy of 100 keV they are usually produced due to charge exchange collisions of ions extracted from a plasma emitter and accelerated by high-voltage pulses. As generation of the ion plasma emitter at a 100-kV potential is quite difficult, it was proposed to extract the ions from a ground potential emitter, accelerate them by high voltage between the emitter and a negatively biased high-transparency grid and transform them into fast neutral molecules in the positive space charge sheaths of the grid. As the energy of fast molecules is defined by potentials of charge exchange collision points inside the sheath their spectrum ranges from zero to a value corresponding to the pulse amplitude. A reverse beam is always generated due to acceleration of ions from the plasma on the other side of the grid. The lower the latter density, the higher the ratio of the primary to the reverse beam currents. When the grid is composed of parallel flat plates, the charge exchange due to reflections from the plates substantially contributes at low gas pressure to production of molecules with the energy corresponding to the pulse amplitude. The work was supported by the Grant No. 14-29-00297 of the Russian Science Foundation.

  4. PolarBase: A Database of High-Resolution Spectropolarimetric Stellar Observations

    NASA Astrophysics Data System (ADS)

    Petit, P.; Louge, T.; Théado, S.; Paletou, F.; Manset, N.; Morin, J.; Marsden, S. C.; Jeffers, S. V.

    2014-05-01

    PolarBase is an evolving database that contains all stellar data collected with the ESPaDOnS and NARVAL high-resolution spectropolarimeters, in their reduced form, as soon as they become public. As of early 2014, observations of 2000 stellar objects throughout the Hertzsprung-Russell diagram are available. Intensity spectra are available for all targets, and the majority of the observations also include simultaneous spectra in circular or linear polarization, with the majority of the polarimetric measurements being performed only in circularly polarized light (Stokes V). Observations are associated with a cross-correlation pseudoline profile in all available Stokes parameters, greatly increasing the detectability of weak polarized signatures. Stokes V signatures are detected for more than 300 stars of all masses and evolutionary stages, and linear polarization is detected in 35 targets. The detection rate in Stokes V is found to be anticorrelated with the stellar effective temperature. This unique set of Zeeman detections offers the first opportunity to run homogeneous magnetometry studies throughout the H-R diagram. The Web interface of PolarBase is available at http://polarbase.irap.omp.eu.

  5. Imaging polarimetry of the fogbow: polarization characteristics of white rainbows measured in the high Arctic.

    PubMed

    Horváth, Gábor; Hegedüs, Ramón; Barta, András; Farkas, Alexandra; Åkesson, Susanne

    2011-10-01

    The knowledge on the optics of fogbows is scarce, and their polarization characteristics have never been measured to our knowledge. To fill this gap we measured the polarization features of 16 fogbows during the Beringia 2005 Arctic polar research expedition by imaging polarimetry in the red, green and blue spectral ranges. We present here the first polarization patterns of the fogbow. In the patterns of the degree of linear polarization p, fogbows and their supernumerary bows are best visible in the red spectral range due to the least dilution of fogbow light by light scattered in air. In the patterns of the angle of polarization α fogbows are practically not discernible because their α-pattern is the same as that of the sky: the direction of polarization is perpendicular to the plane of scattering and is parallel to the arc of the bow, independently of the wavelength. Fogbows and their supernumeraries were best seen in the patterns of the polarized radiance. In these patterns the angular distance δ between the peaks of the primary and the first supernumerary and the angular width σ of the primary bow were determined along different radii from the center of the bow. δ ranged between 6.08° and 13.41°, while σ changed from 5.25° to 19.47°. Certain fogbows were relatively homogeneous, meaning small variations of δ and σ along their bows. Other fogbows were heterogeneous, possessing quite variable δ- and σ-values along their bows. This variability could be a consequence of the characteristics of the high Arctic with open waters within the ice shield resulting in the spatiotemporal change of the droplet size within the fog. PMID:22016248

  6. Advantages of Single-Molecule Real-Time Sequencing in High-GC Content Genomes

    PubMed Central

    Shin, Seung Chul; Ahn, Do Hwan; Kim, Su Jin; Lee, Hyoungseok; Oh, Tae-Jin; Lee, Jong Eun; Park, Hyun

    2013-01-01

    Next-generation sequencing has become the most widely used sequencing technology in genomics research, but it has inherent drawbacks when dealing with high-GC content genomes. Recently, single-molecule real-time sequencing technology (SMRT) was introduced as a third-generation sequencing strategy to compensate for this drawback. Here, we report that the unbiased and longer read length of SMRT sequencing markedly improved genome assembly with high GC content via gap filling and repeat resolution. PMID:23894349

  7. Generation of bright phase-matched circularly-polarized extreme ultraviolet high harmonics

    NASA Astrophysics Data System (ADS)

    Kfir, Ofer; Grychtol, Patrik; Turgut, Emrah; Knut, Ronny; Zusin, Dmitriy; Popmintchev, Dimitar; Popmintchev, Tenio; Nembach, Hans; Shaw, Justin M.; Fleischer, Avner; Kapteyn, Henry; Murnane, Margaret; Cohen, Oren

    2015-02-01

    Circularly-polarized extreme ultraviolet and X-ray radiation is useful for analysing the structural, electronic and magnetic properties of materials. To date, such radiation has only been available at large-scale X-ray facilities such as synchrotrons. Here, we demonstrate the first bright, phase-matched, extreme ultraviolet circularly-polarized high harmonics source. The harmonics are emitted when bi-chromatic counter-rotating circularly-polarized laser pulses field-ionize a gas in a hollow-core waveguide. We use this new light source for magnetic circular dichroism measurements at the M-shell absorption edges of Co. We show that phase-matching of circularly-polarized harmonics is unique and robust, producing a photon flux comparable to linearly polarized high harmonic sources. This work represents a critical advance towards the development of table-top systems for element-specific imaging and spectroscopy of multiple elements simultaneously in magnetic and other chiral media with very high spatial and temporal resolution.

  8. Colloidal lenses allow high-temperature single-molecule imaging and improve fluorophore photostability

    PubMed Central

    Schwartz, Jerrod J.; Stavrakis, Stavros; Quake, Stephen R.

    2014-01-01

    Although single-molecule fluorescence spectroscopy was first demonstrated at near-absolute zero temperatures (1.8 K)1, the field has since advanced to include room-temperature observations2, 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 level both in vitro3–4 and in vivo5–6. However, it is difficult to study systems and phenomena at temperatures above 37 °C, because the index-matching fluids used with high-numerical-aperture objective lenses can conduct heat from the sample to the lens, and sustained exposure to high temperatures can cause the lens to fail. Here, we report that TiO2 colloids with diameters of 2 μm and a high refractive index can act as lenses that are capable of single-molecule imaging at 70 °C when placed in immediate proximity to an emitting molecule. The optical system is completed by a low-numerical-aperture optic that can have a long working distance and an air interface, which allows the sample to be independently heated. Colloidal lenses were used for parallel imaging of surface-immobilized single fluorophores and for real-time single-molecule measurements of mesophilic and thermophilic enzymes at 70 °C. Fluorophores in close proximity to TiO2 also showed a 40% increase in photostability due to a reduction of the excited-state lifetime. PMID:20023643

  9. Slowing and cooling of heavy or light (even with a tiny electric dipole moment) polar molecules using a novel, versatile electrostatic Stark decelerator.

    PubMed

    Wang, Qin; Hou, Shunyong; Xu, Liang; Yin, Jianping

    2016-02-21

    To meet some demands for realizing precise measurements of an electric dipole moment of electron (eEDM) and examining cold collisions or cold chemical physics, we have proposed a novel, versatile electrostatic Stark decelerator with an array of true 3D electric potential wells, which are created by a series of horizontally-oriented, U-shaped electrodes with time-sequence controlling high voltages (± HV) and two guiding electrodes with a constant voltage. We have calculated the 2D electric field distribution, the Stark shifts of the four lowest rotational sub-levels of PbF molecules in the X1(2)Π1/2(v = 0) electronic and vibrational ground states as well as the population in the different rotational levels. We have discussed the 2D longitudinal and transverse phase-space acceptances of PbF molecules in our decelerator. Subsequently, we have simulated the dynamic processes of the decelerated PbF molecules using the 3D Monte-Carlo method, and have found that a supersonic PbF beam with a velocity of 300 m s(-1) can be efficiently slowed to about 5 m s(-1), which will greatly enhance the sensitivities to research a parity violation and measure an eEDM. In addition, we have investigated the dependences of the longitudinal velocity spread, longitudinal temperature and bunching efficiency on both the number of guiding stages and high voltages, and found that after bunching, a cold packet of PbF molecules in the J = 7/2, MΩ = -7/4 state with a longitudinal velocity spread of 0.69 m s(-1) (corresponding to a longitudinal temperature of 2.35 mK) will be produced by our high-efficient decelerator, which will generate a high energy-resolution molecular beam for studying cold collision physics. Finally, our novel decelerator can also be used to efficiently slow NO molecules with a tiny electric dipole moment (EDM) of 0.16 D from 315 m s(-1) to 28 m s(-1). It is clear that our proposed new decelerator has a good slowing performance and experimental feasibility as well as wide

  10. Unitary Superfluidity Of Polarized Fermionic Gases In Highly Elongated Traps

    NASA Astrophysics Data System (ADS)

    Baksmaty, L.; Lu, H.; Bolech, C.; Pu, H.

    2010-03-01

    Recent groundbreaking experiments on resonantly interacting fermionic superfluids encountered qualitative and quantitative discrepancies which seem to be a function of the confining geometry. Despite long familiarity with BCS (Bardeen-Cooper-Schrieffer) superfluids in a wide range of physical systems such as nuclear matter, QCD, Astrophysics and Condensed Matter, these observations have defied theoretical explanation. Mindful of quantum rigidity and motivated by this impasse, we study the solution space for 3-dimensional fully self-consistent mean field formulation. Relying on numerical algorithms specifically developed for this purpose, we study realistic systems with up to 10^5 atoms. We find that for a large enough sample in a cigar-shaped trap, there are typically three types of solutions which are almost degenerate and have the ff. properties: (i) There is a solution very similar to the local density approximation (LDA) which is consistently the lowest in energy. (ii) However one of the other two solutions, connected by a smooth transition, and which are more consistent with experiment at high aspect ratio, supports a state very similar to the long sought FFLO (Fulde Ferrel Larkin Ovchinnikov) state. We submit that these solutions are relevant false vacua because, given high energy barriers and near degeneracy of the obtained solutions, the actual states observed in an experiment could be a strong function of the experimental procedure. Darpa OLE grant, ARO Grant no. W911NF-07-1-0464, Welch foundation (C-1669, C-1681) and NSF.

  11. Experimental setup for laser spectroscopy of molecules in a high magnetic field

    NASA Astrophysics Data System (ADS)

    Takazawa, Yasuyuki Kimura; Ken

    2011-01-01

    An experimental setup to measure the effects of a high magnetic field on the structure and decay dynamics of molecules is designed and constructed. A vacuum chamber is mounted in the bore of a superconducting magnet. A molecular beam passes in the chamber. Pulsed laser light excites the molecules in the field. The parent or fragment ions are extracted by an electric field parallel to the magnetic field. They are detected by a microchannel plate. Their mass and charge are determined by the time-of-flight method. The performance of the setup was examined using resonance-enhanced two-photon ionization through the X2 Pi- A2Σ + transition of nitric oxide (NO) molecules. The ions were detected with sufficient mass resolution to discriminate the species in a field of up to 10 T. This is the first experiment to succeed in the mass-selective detection of ions by the time-of-flight method in a high magnetic field. By measuring NO+ ion current as a function of the laser frequency, the X2Pi- A2 Σ + rotational transition lines, separated clearly from the background noise, were observed in fields of up to 10 T. From the relative strengths of the transition lines, the ion detection efficiency was determined as a function of the magnetic field strength. This setup was shown to be applicable in a field higher than 10 T. The Landau levels of molecules were successfully observed to demonstrate the setup.

  12. Bismuth Interfacial Doping of Organic Small Molecules for High Performance n-type Thermoelectric Materials.

    PubMed

    Huang, Dazhen; Wang, Chao; Zou, Ye; Shen, Xingxing; Zang, Yaping; Shen, Hongguang; Gao, Xike; Yi, Yuanping; Xu, Wei; Di, Chong-An; Zhu, Daoben

    2016-08-26

    Development of chemically doped high performance n-type organic thermoelectric (TE) materials is of vital importance for flexible power generating applications. For the first time, bismuth (Bi) n-type chemical doping of organic semiconductors is described, enabling high performance TE materials. The Bi interfacial doping of thiophene-diketopyrrolopyrrole-based quinoidal (TDPPQ) molecules endows the film with a balanced electrical conductivity of 3.3 S cm(-1) and a Seebeck coefficient of 585 μV K(-1) . The newly developed TE material possesses a maximum power factor of 113 μW m(-1)  K(-2) , which is at the forefront for organic small molecule-based n-type TE materials. These studies reveal that fine-tuning of the heavy metal doping of organic semiconductors opens up a new strategy for exploring high performance organic TE materials. PMID:27496293

  13. Fast, high-fidelity, all-optical and dynamically-controlled polarization gate using room-temperature atomic vapor

    SciTech Connect

    Li, Runbing; Zhu, Chengjie; Deng, L.; Hagley, E. W.

    2014-10-20

    We demonstrate a fast, all-optical polarization gate in a room-temperature atomic medium. Using a Polarization-Selective-Kerr-Phase-Shift (PSKPS) technique, we selectively write a π phase shift to one circularly-polarized component of a linearly-polarized input signal field. The output signal field maintains its original strength but acquires a 90° linear polarization rotation, demonstrating fast, high-fidelity, dynamically-controlled polarization gate operation. The intensity of the polarization-switching field used in this PKSPK-based polarization gate operation is only 2 mW/cm{sup 2}, which would be equivalent to 0.5 nW of light power (λ = 800 nm) confined in a typical commercial photonic hollow-core fiber. This development opens a realm of possibilities for potential future extremely low light level telecommunication and information processing systems.

  14. High Resolution Continuous Flow Analysis System for Polar Ice Cores

    NASA Astrophysics Data System (ADS)

    Dallmayr, Remi; Azuma, Kumiko; Yamada, Hironobu; Kjær, Helle Astrid; Vallelonga, Paul; Azuma, Nobuhiko; Takata, Morimasa

    2014-05-01

    In the last decades, Continuous Flow Analysis (CFA) technology for ice core analyses has been developed to reconstruct the past changes of the climate system 1), 2). Compared with traditional analyses of discrete samples, a CFA system offers much faster and higher depth resolution analyses. It also generates a decontaminated sample stream without time-consuming sample processing procedure by using the inner area of an ice-core sample.. The CFA system that we have been developing is currently able to continuously measure stable water isotopes 3) and electrolytic conductivity, as well as to collect discrete samples for the both inner and outer areas with variable depth resolutions. Chemistry analyses4) and methane-gas analysis 5) are planned to be added using the continuous water stream system 5). In order to optimize the resolution of the current system with minimal sample volumes necessary for different analyses, our CFA system typically melts an ice core at 1.6 cm/min. Instead of using a wire position encoder with typical 1mm positioning resolution 6), we decided to use a high-accuracy CCD Laser displacement sensor (LKG-G505, Keyence). At the 1.6 cm/min melt rate, the positioning resolution was increased to 0.27mm. Also, the mixing volume that occurs in our open split debubbler is regulated using its weight. The overflow pumping rate is smoothly PID controlled to maintain the weight as low as possible, while keeping a safety buffer of water to avoid air bubbles downstream. To evaluate the system's depth-resolution, we will present the preliminary data of electrolytic conductivity obtained by melting 12 bags of the North Greenland Eemian Ice Drilling (NEEM) ice core. The samples correspond to different climate intervals (Greenland Stadial 21, 22, Greenland Stadial 5, Greenland Interstadial 5, Greenland Interstadial 7, Greenland Stadial 8). We will present results for the Greenland Stadial -8, whose depths and ages are between 1723.7 and 1724.8 meters, and 35.520 to

  15. A High Throughput Screening Assay System for the Identification of Small Molecule Inhibitors of gsp

    PubMed Central

    Bhattacharyya, Nisan; Hu, Xin; Chen, Catherine Z.; Mathews Griner, Lesley A.; Zheng, Wei; Inglese, James; Austin, Christopher P.; Marugan, Juan J.; Southall, Noel; Neumann, Susanne; Northup, John K.; Ferrer, Marc; Collins, Michael T.

    2014-01-01

    Mis-sense mutations in the α-subunit of the G-protein, Gsα, cause fibrous dysplasia of bone/McCune-Albright syndrome. The biochemical outcome of these mutations is constitutively active Gsα and increased levels of cAMP. The aim of this study was to develop an assay system that would allow the identification of small molecule inhibitors specific for the mutant Gsα protein, the so-called gsp oncogene. Commercially available Chinese hamster ovary cells were stably transfected with either wild-type (WT) or mutant Gsα proteins (R201C and R201H). Stable cell lines with equivalent transfected Gsα protein expression that had relatively lower (WT) or higher (R201C and R201H) cAMP levels were generated. These cell lines were used to develop a fluorescence resonance energy transfer (FRET)–based cAMP assay in 1536-well microplate format for high throughput screening of small molecule libraries. A small molecule library of 343,768 compounds was screened to identify modulators of gsp activity. A total of 1,356 compounds with inhibitory activity were initially identified and reconfirmed when tested in concentration dose responses. Six hundred eighty-six molecules were selected for further analysis after removing cytotoxic compounds and those that were active in forskolin-induced WT cells. These molecules were grouped by potency, efficacy, and structural similarities to yield 22 clusters with more than 5 of structurally similar members and 144 singleton molecules. Seven chemotypes of the major clusters were identified for further testing and analyses. PMID:24667240

  16. Polarization beam combination technique for gain saturation effect compensation in high-energy systems

    NASA Astrophysics Data System (ADS)

    Chen, Junchi; Peng, Yujie; Su, Hongpeng; Leng, Yuxin

    2016-06-01

    To compensate for the gain saturation effect in the high-energy laser amplifier, a modified polarization beam combination (PBC) method is introduced to reshape temporal waveform of the injected laser pulse to obtain a controlled high-energy laser pulse shape after amplification. One linearly polarized beam is divided into two orthogonal polarized beams, which spatially recombine together collinearly after propagating different optical paths with relative time delay in PBC structure. The obtained beam with polarization direction being rotated by the following half wave plate is divided and combined again to reform a new beam in another modified polarization beam structure. The reformed beam is injected into three cascaded laser amplifiers. The amplified pulse shape can be controlled by the incident pulse shape and amplifier gain, which is agreeable to the simulation by the Frank-Nodvik equations. Based on the simple method, the various temporal waveform of output pulse with tunable 7 to 20 ns pulse duration can be obtained without interferometric fringes.

  17. Physiological Ecology of Mesozoic Polar Forests in a High CO2 Environment

    PubMed Central

    BEERLING, D. J.; OSBORNE, C. P.

    2002-01-01

    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 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 palaeo‐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

  18. Components of the Bond Energy in Polar Diatomic Molecules, Radicals, and Ions Formed by Group-1 and Group-2 Metal Atoms.

    PubMed

    Yu, Haoyu; Truhlar, Donald G

    2015-07-14

    Although many transition metal complexes are known to have high multireference character, the multireference character of main-group closed-shell singlet diatomic molecules like BeF, CaO, and MgO has been less studied. However, many group-1 and group-2 diatomic molecules do have multireference character, and they provide informative systems for studying multireference character because they are simpler than transition metal compounds. The goal of the present work is to understand these multireference systems better so that, ultimately, we can apply what we learn to more complicated multireference systems and to the design of new exchange-correlation functionals for treating multireference systems more adequately. Fourteen main-group diatomic molecules and one triatomic molecule (including radicals, cations, and anions, as well as neutral closed-shell species) have been studied for this article. Eight of these molecules contain a group-1 element, and six contain a group-2 element. Seven of these molecules are multireference systems, and eight of them are single-reference systems. Fifty-three exchange-correlation functionals of 11 types [local spin-density approximation (LSDA), generalized gradient approximation (GGA), nonseparable gradient approximation (NGA), global-hybrid GGA, meta-GGA, meta-NGA, global-hybrid meta GGA, range-separated hybrid GGA, range-separated hybrid meta-GGA, range-separated hybrid meta-NGA, and DFT augmented with molecular mechanics damped dispersion (DFT-D)] and the Hartree-Fock method have been applied to calculate the bond distance, bond dissociation energy (BDE), and dipole moment of these molecules. All of the calculations are converged to a stable solution by allowing the symmetry of the Slater determinant to be broken. A reliable functional should not only predict an accurate BDE but also predict accurate components of the BDE, so each bond dissociation energy has been decomposed into ionization potential (IP) of the electropositive

  19. High-Contrast NIR Polarization Imaging of MWC480

    NASA Technical Reports Server (NTRS)

    McElwain, M. W.; Kusakabe, N.; Hashimoto, J.; Kudo, T.; Kandori, R.; Miyama, S.; Morino, J.-I.; Suto, H.; Suzuki, R.; Tamura, M.; Grady, C. A.; Sitko, M. L.; Werren, C.; Day, A. N.; Beerman, C.; Iye, M.; Lynch, D. K.; Russell, R. W.; Brafford, S. M.

    2012-01-01

    One of the key predictions of modeling from the IR excess of Herbig Ae stars is that for protoplanetary disks, where significant grain growth and settling has occurred, the dust disk has flattened to the point that it can be partially or largely shadowed by the innermost material at or near the dust sublimation radius. When the self-shadowing has already started, the outer disk is expected to be detected in scattered light only in the exceptional cases that the scale height of the dust disk at the sublimation radius is smaller than usual. High-contrast imaging combined with the IR spectral energy distribution allow us to measure the degree of flattening of the disk, as well as to determine the properties of the outer disk. We present polarimetric differential imaging in H band obtained with Subaru/HiCIAO of one such system, MWC 480. The HiCIAO data were obtained at a historic minimum of the NIR excess. The disk is detected in scattered light from 0".2-1"0 (27.4-137 AU). Together with the marginal detection of the disk from 1998 February 24 by HST / NICMOS, our data constrain the opening half angle for the disk to lie between 1.3 <= Theta <=2.2 deg. When compared with similar measures in CO for the gas disk from the literature, the dust disk subtends only approx 30% of the gas disk scale height (H/R approx 0. 03). Such a dust disk is a factor of 5-7 flatter than transitional disks, which have structural signatures that giant planets have formed.

  20. A high-power microwave circular polarizer and its application on phase shifter

    NASA Astrophysics Data System (ADS)

    Shao, Hao; Hu, Yongmei; Chang, Chao; Guo, Letian

    2016-04-01

    A high-power waveguide dual circular polarizer was theoretically designed and proof-of-principle was experimentally tested. It consists of two incident rectangular waveguides with a perpendicular H-plane junction, one circular waveguide with a pair of trapezoidal grooves coupled in E-plane at the top, a spherical crown located at the bottom, and an iris at the perpendicular junction of two rectangular waveguides. When wave incidents at one of the two separated rectangular waveguides, it, respectively, generates a left-hand circular polarized wave or a right-hand circular polarized wave in the circular waveguide. By adding a dumbbell-like metal plug driven with a high speed servomotor, a movable short circuit is formed along the circular waveguide to adjust the output RF phase of the rectangular port, realizing a high-speed high-power phase shifter. The C-band high power microwave (HPM) experiments were carried out, and the power capacity of the HPM polarizer and phase shifter was demonstrated to reach gigawatt level.

  1. Non perturbative approach for a polar and polarizable linear molecule in an inhomogeneous electric field: Application to molecular beam deviation experiments

    NASA Astrophysics Data System (ADS)

    Benichou, E.; Allouche, A. R.; Antoine, R.; Aubert-Frecon, M.; Bourgoin, M.; Broyer, M.; Dugourd, Ph.; Hadinger, G.; Rayane, D.

    A non perturbative approach is used to solve the problem of a rigid linear molecule with both a permanent dipole moment and a static dipole polarizability, in a static electric field. Eigenenergies are obtained and compared to perturbative low field and high field approximations. Analytical expressions for the orientation parameters and for the gradient of the energy are given. This non perturbative approach is applied to the simulation of beam deviation experiments in strong electric field. Results of simulations are given for inhomogeneous alkali dimers. For LiNa, the simulations are compared to experimental data. For LiK, deviation profiles have been simulated in order to prepare future experiments on this molecule.

  2. Polarized light imaging of birefringence and diattenuation at high resolution and high sensitivity

    PubMed Central

    Mehta, Shalin B.; Shribak, Michael; Oldenbourg, Rudolf

    2013-01-01

    Polarized light microscopy provides unique opportunities for analyzing the molecular order in man-made and natural materials, including biological structures inside living cells, tissues, and whole organisms. 20 years ago, the LC-PolScope was introduced as a modern version of the traditional polarizing microscope enhanced by liquid crystal devices for the control of polarization, and by electronic imaging and digital image processing for fast and comprehensive image acquisition and analysis. The LCPolScope is commonly used for birefringence imaging, analyzing the spatial and temporal variations of the differential phase delay in ordered and transparent materials. Here we describe an alternative use of the LC-PolScope for imaging the polarization dependent transmittance of dichroic materials. We explain the minor changes needed to convert the instrument between the two imaging modes, discuss the relationship between the quantities measured with either instrument, and touch on the physical connection between refractive index, birefringence, transmittance, diattenuation, and dichroism. PMID:24273640

  3. Collisional properties of cold spin-polarized nitrogen gas: Theory, experiment, and prospects as a sympathetic coolant for trapped atoms and molecules

    SciTech Connect

    Tscherbul, T. V.; Dalgarno, A.; Klos, J.; Zygelman, B.; Pavlovic, Z.; Hummon, M. T.; Lu, H.-I.; Tsikata, E.; Doyle, J. M.

    2010-10-15

    We report a combined experimental and theoretical study of collision-induced dipolar relaxation in a cold spin-polarized gas of atomic nitrogen (N). We use buffer gas cooling to create trapped samples of {sup 14}N and {sup 15}N atoms with densities (5{+-}2)x10{sup 12} cm{sup -3} and measure their magnetic relaxation rates at milli-Kelvin temperatures. These measurements, together with rigorous quantum scattering calculations based on accurate ab initio interaction potentials for the {sup 7}{Sigma}{sub u}{sup +} electronic state of N{sub 2} demonstrate that dipolar relaxation in N+N collisions occurs at a slow rate of {approx}10{sup -13} cm{sup 3}/s over a wide range of temperatures (1 mK to 1 K) and magnetic fields (10 mT to 2 T). The calculated dipolar relaxation rates are insensitive to small variations of the interaction potential and to the magnitude of the spin-exchange interaction, enabling the accurate calibration of the measured N atom density. We find consistency between the calculated and experimentally determined rates. Our results suggest that N atoms are promising candidates for future experiments on sympathetic cooling of molecules.

  4. Dipole polarizability of alkali-metal (Na, K, Rb)–alkaline-earth-metal (Ca, Sr) polar molecules: Prospects for alignment

    SciTech Connect

    Gopakumar, Geetha Abe, Minori; Hada, Masahiko; Kajita, Masatoshi

    2014-06-14

    Electronic open-shell ground-state properties of selected alkali-metal–alkaline-earth-metal polar molecules are investigated. We determine potential energy curves of the {sup 2}Σ{sup +} ground state at the coupled-cluster singles and doubles with partial triples (CCSD(T)) level of electron correlation. Calculated spectroscopic constants for the isotopes ({sup 23}Na, {sup 39}K, {sup 85}Rb)–({sup 40}Ca, {sup 88}Sr) are compared with available theoretical and experimental results. The variation of the permanent dipole moment (PDM), average dipole polarizability, and polarizability anisotropy with internuclear distance is determined using finite-field perturbation theory at the CCSD(T) level. Owing to moderate PDM (KCa: 1.67 D, RbCa: 1.75 D, KSr: 1.27 D, RbSr: 1.41 D) and large polarizability anisotropy (KCa: 566 a.u., RbCa: 604 a.u., KSr: 574 a.u., RbSr: 615 a.u.), KCa, RbCa, KSr, and RbSr are potential candidates for alignment and orientation in combined intense laser and external static electric fields.

  5. CN Zeeman and dust polarization in a high-mass cold clump

    NASA Astrophysics Data System (ADS)

    Pillai, T.; Kauffmann, J.; Wiesemeyer, H.; Menten, K. M.

    2016-06-01

    We report on the young massive clump (G35.20w) in W48 that previous molecular line and dust observations have revealed to be in the very early stages of star formation. Based on virial analysis, we find that a strong field of 1640 μG is required to keep the clump in pressure equilibrium. We performed a deep Zeeman effect measurement of the 113 GHz CN (1-0) line towards this clump with the IRAM 30 m telescope. We combine simultaneous fitting of all CN hyperfines with Monte Carlo simulations for a large range in realization of the magnetic field to obtain a constraint on the line-of-sight field strength of -687 ± 420 μG. We also analyze archival dust polarization observations towards G35.20w. A strong magnetic field is implied by the remarkably ordered field orientation that is perpendicular to the longest axis of the clump. Based on this, we also estimate the plane-of-sky component of the magnetic field to be ~740 μG. This allows for a unique comparison of the two orthogonal measurements of magnetic field strength of the same region and at similar spatial scales. The expected total field strength shows no significant conflict between the observed field and that required for pressure equilibrium. By producing a probability distribution for a large range in field geometries, we show that plane-of-sky projections are much closer to the true field strengths than line-of-sight projections. This can present a significant challenge for Zeeman measurements of magnetized structures, even with ALMA. We also show that CN molecule does not suffer from depletion on the observed scales in the predominantly cold and highly deuterated core in an early stage of high-mass star formation and is thus a good tracer of the dense gas. Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain).

  6. Development of high-performance alkali-hybrid polarized 3He targets for electron scattering

    NASA Astrophysics Data System (ADS)

    Singh, Jaideep T.; Dolph, P. A. M.; Tobias, W. A.; Averett, T. D.; Kelleher, A.; Mooney, K. E.; Nelyubin, V. V.; Wang, Yunxiao; Zheng, Yuan; Cates, G. D.

    2015-05-01

    Background: Polarized 3He targets have been used as effective polarized neutron targets for electron scattering experiments for over twenty years. Over the last ten years, the effective luminosity of polarized 3He targets based on spin-exchange optical pumping has increased by over an order of magnitude. This has come about because of improvements in commercially-available lasers and an improved understanding of the physics behind the polarization process. Purpose: We present the development of high-performance polarized 3He targets for use in electron scattering experiments. Improvements in the performance of polarized 3He targets, target properties, and operating parameters are documented. Methods: We utilize the technique of alkali-hybrid spin-exchange optical pumping to polarize the 3He targets. Spectrally narrowed diode lasers used for the optical pumping greatly improved the performance. A simulation of the alkali-hybrid spin-exchange optical pumping process was developed to provide guidance in the design of the targets. Data was collected during the characterization of 24 separate glass target cells, each of which was constructed while preparing for one of four experiments at Jefferson Laboratory in Newport News, Virginia. Results: From the data obtained we made determinations of the so-called X -factors that quantify a temperature-dependent and as-yet poorly understood spin-relaxation mechanism that limits the maximum achievable 3He polarization to well under 100%. The presence of the X -factor spin-relaxation mechanism was clearly evident in our data. Good agreement between the simulation and the actual target performance was obtained by including details such as off-resonant optical pumping. Included in our results is a measurement of the K -3He spin-exchange rate coefficient kseK=(7.46 ±0.62 ) ×10-20cm3/s over the temperature range 503 K to 563 K. Conclusions: In order to achieve high performance under the operating conditions described in this paper

  7. A microporous metal-organic framework with polarized trifluoromethyl groups for high methane storage.

    PubMed

    Chang, Ganggang; Li, Bin; Wang, Hailong; Bao, Zongbi; Yildirim, Taner; Yao, Zizhu; Xiang, Shengchang; Zhou, Wei; Chen, Banglin

    2015-10-11

    A novel NbO-type metal-organic framework UTSA-88a with polarized trifluoromethyl groups exhibits a notably high methane storage capacity of 248 cm(3) (STP) cm(-3) (at room temperature and 65 bar) and a working capacity of 185 cm(3) (STP) cm(-3). PMID:26300179

  8. Solvatochromic pyrene analogues of Prodan exhibiting extremely high fluorescence quantum yields in apolar and polar solvents.

    PubMed

    Niko, Yosuke; Kawauchi, Susumu; Konishi, Gen-ichi

    2013-07-22

    True colors: Novel pyrene analogues of Prodan exhibit outstanding photophysical properties with remarkably high fluorescence quantum yield (QY) in solvents ranging from apolar hexane to polar methanol (see figure). This is accompanied by strong solvatochromism and large Stokes shifts. These properties have not been previously achieved in enormous solvatochromic dyes, but are quite useful for emitting materials and imaging tools. PMID:23744761

  9. Massively parallel haplotyping on microscopic beads for the high-throughput phase analysis of single molecules.

    PubMed

    Boulanger, Jérôme; Muresan, Leila; Tiemann-Boege, Irene

    2012-01-01

    In spite of the many advances in haplotyping methods, it is still very difficult to characterize rare haplotypes in tissues and different environmental samples or to accurately assess the haplotype diversity in large mixtures. This would require a haplotyping method capable of analyzing the phase of single molecules with an unprecedented throughput. Here we describe such a haplotyping method capable of analyzing in parallel hundreds of thousands single molecules in one experiment. In this method, multiple PCR reactions amplify different polymorphic regions of a single DNA molecule on a magnetic bead compartmentalized in an emulsion drop. The allelic states of the amplified polymorphisms are identified with fluorescently labeled probes that are then decoded from images taken of the arrayed beads by a microscope. This method can evaluate the phase of up to 3 polymorphisms separated by up to 5 kilobases in hundreds of thousands single molecules. We tested the sensitivity of the method by measuring the number of mutant haplotypes synthesized by four different commercially available enzymes: Phusion, Platinum Taq, Titanium Taq, and Phire. The digital nature of the method makes it highly sensitive to detecting haplotype ratios of less than 1:10,000. We also accurately quantified chimera formation during the exponential phase of PCR by different DNA polymerases. PMID:22558329

  10. Highly Ordered Surface Self-Assembly of Fe₄ Single Molecule Magnets.

    PubMed

    Erler, Philipp; Schmitt, Peter; Barth, Nicole; Irmler, Andreas; Bouvron, Samuel; Huhn, Thomas; Groth, Ulrich; Pauly, Fabian; Gragnaniello, Luca; Fonin, Mikhail

    2015-07-01

    Single molecule magnets (SMMs) have attracted considerable attention due to low-temperature magnetic hysteresis and fascinating quantum effects. The investigation of these properties requires the possibility to deposit well-defined monolayers or spatially isolated molecules within a well-controlled adsorption geometry. Here we present a successful fabrication of self-organized arrays of Fe4 SMMs on hexagonal boron nitride (h-BN) on Rh(111) as template. Using a rational design of the ligand shell optimized for surface assembly and electrospray as a gentle deposition method, we demonstrate how to obtain ordered arrays of molecules forming perfect hexagonal superlattices of tunable size, from small islands to an almost perfect monolayer. High-resolution low temperature scanning tunneling microscopy (STM) reveals that the Fe4 molecule adsorbs on the substrate in a flat geometry, meaning that its magnetic easy axis is perpendicular to the surface. By scanning tunneling spectroscopy (STS) and density functional theory (DFT) calculations, we infer that the majority- and minority-spin components of the spin-split lowest unoccupied molecular orbital (LUMO) can be addressed separately on a submolecular level. PMID:26086677

  11. High-resolution electrohydrodynamic jet printing of small-molecule organic light-emitting diodes.

    PubMed

    Kim, Kukjoo; Kim, Gyeomuk; Lee, Bo Ram; Ji, Sangyoon; Kim, So-Yun; An, Byeong Wan; Song, Myoung Hoon; Park, Jang-Ung

    2015-08-28

    The development of alternative organic light-emitting diode (OLED) fabrication technologies for high-definition and low-cost displays is an important research topic as conventional fine metal mask-assisted vacuum evaporation has reached its limit to reduce pixel sizes and manufacturing costs. Here, we report an electrohydrodynamic jet (e-jet) printing method to fabricate small-molecule OLED pixels with high resolution (pixel width of 5 μm), which significantly exceeds the resolutions of conventional inkjet or commercial OLED display pixels. In addition, we print small-molecule emitting materials which provide a significant advantage in terms of device efficiency and lifetime compared to those with polymers. PMID:26214140

  12. Collisional energy transfer in highly vibrationally excited molecules. Summary report, June 1980-May 1981

    SciTech Connect

    Crim, F.F.

    1981-03-01

    Combining the techniques of direct excitation of overtone vibrations and time resolved spectroscopic detection permits detailed measurements of the vibrational and rotational relaxation of highly vibrationally excited molecules. Using this technique, we have measured vibrational and rotational relaxation in HF(v = 3, 4, 5). By observing near-infrared fluorescence, we determine the self-relaxation probabilities for HF(v = 3, 4, 5) to be 0.19, 0.47, and 0.97, respectively, and find that the rates decrease more rapidly with temperature in these high levels than for v = 1. Using laser double resonance to probe individual rotational states, we find phenomenological rotational relaxation rate constants which decrease montonically with rotational energy change in the vibrationally excited molecule.

  13. Two-center interference in high-order harmonic generation from heteronuclear diatomic molecules.

    PubMed

    Zhu, Xiaosong; Zhang, Qingbin; Hong, Weiyi; Lan, Pengfei; Lu, Peixiang

    2011-01-17

    Two-center interference for heteronuclear diatomic molecules (HeDM) is investigated. The minimum in the high-order harmonic spectrum, as a consequence of the destructive interference, is shifted to lower harmonic orders compared with that in a homonuclear case. This phenomenon is explained by performing phase analysis. It is found that, for an HeDM, the high harmonic spectrum contains information not only on the internuclear separation but also on the properties of the two separate centers, which implies the potential application of estimating the asymmetry of molecules and judging the linear combination of atomic orbitals (LCAO) for the highest occupied molecular orbital (HOMO). Moreover, the possibility to monitor the evolution of HOMO itself in molecular dynamics is also promised. PMID:21263583

  14. Recoil polarization measurements of the proton electromagnetic form factor ratio at high momentum transfer

    SciTech Connect

    Andrew Puckett

    2009-12-01

    Electromagnetic form factors are fundamental properties of the nucleon that describe the effect of its internal quark structure on the cross section and spin observables in elastic lepton-nucleon scattering. Double-polarization experiments have become the preferred technique to measure the proton and neutron electric form factors at high momentum transfers. The recently completed GEp-III experiment at the Thomas Jefferson National Accelerator Facility used the recoil polarization method to extend the knowledge of the proton electromagnetic form factor ratio GpE/GpM to Q2 = 8.5 GeV2. In this paper we present the preliminary results of the experiment.

  15. Possibilities of polarized protons in Sp anti p S and other high energy hadron colliders

    SciTech Connect

    Courant, E.D.

    1984-01-01

    The requirements for collisions with polarized protons in hadron colliders above 200 GeV are listed and briefly discussed. Particular attention is given to the use of the ''Siberan snake'' to eliminate depolarizing resonances, which occur when the spin precession frequency equals a frequency contained in the spectrum of the field seen by the beam. The Siberian snake is a device which makes the spin precession frequency essentially constant by using spin rotators, which precess the spin by 180/sup 0/ about either the longitudinal or transverse horizontal axis. It is concluded that operation with polarized protons should be possible at all the high energy hadron colliders. (LEW)

  16. High intensity induced photocurrent polarity switching in lead sulfide nanowire field effect transistors.

    PubMed

    Yang, Yiming; Peng, Xingyue; Yu, Dong

    2014-05-16

    We report an optoelectronic investigation of lead sulfide nanowires (NWs) by scanning photocurrent microscopy. The photocurrent in p-type lead sulfide NW field effect transistors has demonstrated unusually nonlinear dependence on the intensity of local excitation. Surprisingly, the photocurrent polarity can be reversed under high illumination intensity on the order of 100 W cm(-2). The origin of this photocurrent polarity switching is that the photo-injected carriers flip the direction of the electric field near the contact. These observations shed light on the nonlinear optoelectronic characteristics in semiconductor nanostructures and may provide an innovative method for optically tailoring local band structures. PMID:24763392

  17. Enhancing High-Order Harmonic Generation in Light Molecules by Using Chirped Pulses.

    PubMed

    Lara-Astiaso, M; Silva, R E F; Gubaydullin, A; Rivière, P; Meier, C; Martín, F

    2016-08-26

    One of the current challenges in high-harmonic generation is to extend the harmonic cutoff to increasingly high energies while maintaining or even increasing the efficiency of the high-harmonic emission. Here we show that the combined effect of down-chirped pulses and nuclear dynamics in light molecules allows one to achieve this goal, provided that long enough IR pulses are used to allow the nuclei to move well outside the Franck-Condon region. We also show that, by varying the duration of the chirped pulse or by performing isotopic substitution while keeping the pulse duration constant, one can control the extension of the harmonic plateau. PMID:27610851

  18. High-order-harmonic generation in benzene with linearly and circularly polarized laser pulses

    NASA Astrophysics Data System (ADS)

    Wardlow, Abigail; Dundas, Daniel

    2016-02-01

    High-order-harmonic generation in benzene is studied using a mixed quantum-classical approach in which the electrons are described using time-dependent density-functional theory while the ions move classically. The interaction with both linearly and circularly polarized infrared (λ =800 nm) laser pulses of duration of ten cycles (26.7 fs) is considered. The effect of allowing the ions to move is investigated as is the effect of including self-interaction corrections to the exchange-correlation functional. Our results for circularly polarized pulses are compared with previous calculations in which the ions were kept fixed and self-interaction corrections were not included, while our results for linearly polarized pulses are compared with both previous calculations and experiment. We find that even for the short-duration pulses considered here, the ionic motion greatly influences the harmonic spectra. While ionization and ionic displacements are greatest when linearly polarized pulses are used, the response to circularly polarized pulses is almost comparable, in agreement with previous experimental results.

  19. Characterization of highly scattering media by measurement of diffusely backscattered polarized light

    DOEpatents

    Hielscher, Andreas H.; Mourant, Judith R.; Bigio, Irving J.

    2000-01-01

    An apparatus and method for recording spatially dependent intensity patterns of polarized light that is diffusely backscattered from highly scattering media are described. These intensity patterns can be used to differentiate different turbid media, such as polystyrene-sphere and biological-cell suspensions. Polarized light from a He-Ne laser (.lambda.=543 nm) is focused onto the surface of the scattering medium, and a surface area of approximately 4.times.4 cm centered on the light input point is imaged through polarization analysis optics onto a CCD camera. A variety of intensity patterns may be observed by varying the polarization state of the incident laser light and changing the analyzer configuration to detect different polarization components of the backscattered light. Experimental results for polystyrene-sphere and Intralipid suspensions demonstrate that the radial and azimuthal variations of the observed pattern depend on the concentration, size, and anisotropy factor, g, of the particles constituting the scattering medium. Measurements performed on biological cell suspensions show that intensity patterns can be used to differentiate between suspensions of cancerous and non-cancerous cells. Introduction of the Mueller-matrix for diffusely backscattered light, permits the selection of a subset of measurements which comprehensively describes the optical properties of backscattering media.

  20. Ultra-broadband and high-efficiency polarization conversion metasurface with multiple plasmon resonance modes

    NASA Astrophysics Data System (ADS)

    Dong, Guo-Xiang; Shi, Hong-Yu; Xia, Song; Li, Wei; Zhang, An-Xue; Xu, Zhuo; Wei, Xiao-Yong

    2016-08-01

    In this paper, we present a novel metasurface design that achieves a high-efficiency ultra-broadband cross polarization conversion. The metasurface is composed of an array of unit resonators, each of which combines an H-shaped structure and two rectangular metallic patches. Different plasmon resonance modes are excited in unit resonators and allow the polarization states to be manipulated. The bandwidth of the cross polarization converter is 82% of the central frequency, covering the range from 15.7 GHz to 37.5 GHz. The conversion efficiency of the innovative new design is higher than 90%. At 14.43 GHz and 40.95 GHz, the linearly polarized incident wave is converted into a circularly polarized wave. Project supported by the National Natural Science Foundation of China (Grant Nos. 61471292, 61331005, 61471388, 51277012, 41404095, and 61501365), the 111 Project, China (Grant No. B14040), the National Basic Research Program of China (Grant No. 2015CB654602), and the China Postdoctoral Science Foundation ( Grant No. 2015M580849).