1,410 research outputs found
Slingshot non-sequential double ionization as a gate to anti-correlated two electron escape
At intensities below-the-recollision threshold, we show that
re-collision-induced excitation with one electron escaping fast after
re-collision and the other electron escaping with a time delay via a Coulomb
slingshot motion is one of the most important mechanisms of non-sequential
double ionization, for strongly-driven He at 400 nm. Slingshot-NSDI is a
general mechanism present for a wide range of low intensities and pulse
durations. Anti-correlated two-electron escape is its striking hallmark. This
mechanism offers an alternative explanation of anti-correlated two-electron
escape obtained in previous studies.Comment: 6 pages, 3 figure
Reduction of antimicrobial resistance as induced by Flavomycin
The demand for pork and poultry products is strongly influenced by the consumers concern for healthy and safe food The topic of food safety mainly concentrates on Salmonella contamination and is recently joined by the topic of antimicrobial resistance due to the use of antimicrobial growth promoters (AGP) in animal feed
Reducing effect of Flavomycin on Salmonella shedding and antibiotic resistance in pigs
The demand for food from pork origin is strongly influenced by consumers\u27 concern for healthy and safe food. The topic of food safety mainly concentrates on Salmonella contamination and is recently joined by the topic of antimicrobial resistance due to the use of antimicrobial growth promoters (AGMPs) in animal feed
Carrier-envelope phase control over pathway interference in strong-field dissociation of H
The dissociation of an H molecular-ion beam by linearly polarized,
carrier-envelope-phase-tagged 5 fs pulses at 4W/cm with a
central wavelength of 730 nm was studied using a coincidence 3D momentum
imaging technique. Carrier-envelope-phase-dependent asymmetries in the emission
direction of H fragments relative to the laser polarization were observed.
These asymmetries are caused by interference of odd and even photon number
pathways, where net-zero photon and 1-photon interference predominantly
contributes at H+H kinetic energy releases of 0.2 -- 0.45 eV, and
net-2-photon and 1-photon interference contributes at 1.65 -- 1.9 eV. These
measurements of the benchmark H molecule offer the distinct advantage
that they can be quantitatively compared with \textit{ab initio} theory to
confirm our understanding of strong-field coherent control via the
carrier-envelope phase
Steering proton migration in hydrocarbons using intense few-cycle laser fields
Proton migration is a ubiquitous process in chemical reactions related to
biology, combustion, and catalysis. Thus, the ability to control the movement
of nuclei with tailored light, within a hydrocarbon molecule holds promise for
far-reaching applications. Here, we demonstrate the steering of hydrogen
migration in simple hydrocarbons, namely acetylene and allene, using
waveform-controlled, few-cycle laser pulses. The rearrangement dynamics are
monitored using coincident 3D momentum imaging spectroscopy, and described with
a quantum-dynamical model. Our observations reveal that the underlying control
mechanism is due to the manipulation of the phases in a vibrational wavepacket
by the intense off-resonant laser field.Comment: 5 pages, 4 figure
Phase- and intensity-resolved measurements of above threshold ionization by few-cycle pulses
We investigate the carrier-envelope phase and intensity dependence of the
longitudinal momentum distribution of photoelectrons resulting from
above-threshold ionization of argon by few-cycle laser pulses. The intensity of
the pulses with a center wavelength of 750\,nm is varied in a range between
and \unit[5.5 \times 10^{14}]{W/cm^2}. Our measurements
reveal a prominent maximum in the carrier-envelope phase-dependent asymmetry at
photoelectron energies of 2\, ( being the
ponderomotive potential), that is persistent over the entire intensity range.
Further local maxima are observed at 0.3 and 0.8\,. The
experimental results are in good agreement with theoretical results obtained by
solving the three-dimensional time-dependent Schr\"{o}dinger equation (3D
TDSE). We show that for few-cycle pulses, the carrier-envelope phase-dependent
asymmetry amplitude provides a reliable measure for the peak intensity on
target. Moreover, the measured asymmetry amplitude exhibits an
intensity-dependent interference structure at low photoelectron energy, which
could be used to benchmark model potentials for complex atoms
Complete characterization of single-cycle double ionization of argon from the nonsequential to the sequential ionization regime
Citation: Kubel, M., Burger, C., Kling, N. G., Pischke, T., Beaufore, L., Ben-Itzhak, I., . . . Bergues, B. (2016). Complete characterization of single-cycle double ionization of argon from the nonsequential to the sequential ionization regime. Physical Review A, 93(5), 9. doi:10.1103/PhysRevA.93.053422Selected features of nonsequential double ionization have been qualitatively reproduced by a multitude of different (quantum and classical) approaches. In general, however, the typical uncertainty of laser pulse parameters and the restricted number of observables measured in individual experiments leave room for adjusting theoretical results to match the experimental data. While this has been hampering the assessment of different theoretical approaches leading to conflicting interpretations, comprehensive experimental data that would allow such an ultimate and quantitative assessment have been missing so far. To remedy this situation we have performed a kinematically complete measurement of single-cycle multiple ionization of argon over a one order of magnitude range of intensity. The momenta of electrons and ions resulting from the ionization of the target gas are measured in coincidence, while each ionization event is tagged with the carrier-envelope phase and intensity of the 4-fs laser pulse driving the process. The acquired highly differential experimental data provide a benchmark for a rigorous test of the many competing theoretical models used to describe nonsequential double ionization
Cafetería de la Monsanto Company, San Luis, Mo. (U.S.A.)
This cafeteria has been designed to serve the staff of the buildings housing the central offices of the firm. It is adapted to a sloping gradient of the ground, and this provides a contrast to the formal symmetry of the main buildings.
The structure of the cafeteria is unfaced concrete, locally cast, and at certain points, it also serves as a sculptural and architectural motif.
Much care has also been taken so that natural lighting can be enjoyed at all levels of the cafeteria, whilst the immediate surroundings have been cleverly gardened to provide a pleasant environment.El volumen definido por la cafetería, que fue concebida para dar servicio a los empleados del grupo de edificios que albergan las oficinas centrales de la empresa, aparece claramente señalado por el perfil escalonado que presenta el terreno, lo que añade una geometría complementaria a la de la simetría formal de dichos edificios.
Su estructura realizada a base de hormigón «visto» moldeado in situ, en ciertos puntos, sirve al mismo tiempo como elemento escultórico y arquitectónico.
La iluminación ha sido asimismo cuidadosamente estudiada para que se disfrute en todos los niveles de la cafetería de iluminación natural; y el entorno, de patios, etc., tratado paisajísticamente, para ofrecer unas vistas agradables al usuario
Waveform control of orientation-dependent ionization of DCl in few-cycle laser fields
Strong few-cycle light fields with stable electric field waveforms allow controlling electrons on time scales down to the attosecond domain. We have studied the dissociative ionization of randomly oriented DCl in 5 fs light fields at 720 nm in the tunneling regime. Momentum distributions of D+ and Cl+ fragments were recorded via velocity-map imaging. A waveformdependent anti-correlated directional emission of D+ and Cl+ fragments is observed. Comparison of our results with calculations indicates that tailoring of the light field via the carrier envelope phase permits the control over the orientation of DCl+ and in turn the directional emission of charged fragments upon the breakup of the molecular ion
Double- and multi-femtosecond pulses produced by birefringent crystals for the generation of 2D laser-induced structures on a stainless steel surface
Laser-induced textures have been proven to be excellent solutions for modifying wetting, friction, biocompatibility, and optical properties of solids. The possibility to generate 2D-submicron morphologies by laser processing has been demonstrated recently. Employing double-pulse irradiation, it is possible to control the induced structures and to fabricate novel and more complex 2D-textures. Nevertheless, double-pulse irradiation often implies the use of sophisticated setups for modifying the pulse polarization and temporal profile. Here, we show the generation of homogeneous 2D-LIPSS (laser-induced periodic surface structures) over large areas utilizing a simple array of birefringent crystals. Linearly and circularly polarized pulses were applied, and the optimum process window was defined for both. The results are compared to previous studies, which include a delay line, and the reproducibility between the two techniques is validated. As a result of a systematic study of the process parameters, the obtained morphology was found to depend both on the interplay between fluence and inter-pulse delay, as well as on the number of incident pulses. The obtained structures were characterized via SEM (scanning electron microscopy) and atomic force microscopy. We believe that our results represent a novel approach to surface structuring, primed for introduction in an industrial environment
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