6 results on '"Gefen Corem"'
Search Results
2. Ice Nucleation on a Corrugated Surface
- Author
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Chenfang, Lin, Gefen, Corem, Oded, Godsi, Gil, Alexandrowicz, George R, Darling, and Andrew, Hodgson
- Subjects
Article - Abstract
Heterogeneous ice nucleation is a key process in many environmental and technical fields and is of particular importance in modeling atmospheric behavior and the Earth’s climate. Despite an improved understanding of how water binds at solid surfaces, no clear picture has emerged to describe how 3D ice grows from the first water layer, nor what makes a particular surface efficient at nucleating bulk ice. This study reports how water at a corrugated, hydrophilic/hydrophobic surface restructures from a complex 2D network, optimized to match the solid surface, to grow into a continuous ice film. Unlike the water networks formed on plane surfaces, the corrugated Cu(511) surface stabilizes a buckled hexagonal wetting layer containing both hydrogen acceptor and donor sites. First layer water is able to relax into an “icelike” arrangement as further water is deposited, creating an array of donor and acceptor sites with the correct spacing and corrugation to stabilize second layer ice and allow continued commensurate multilayer ice growth. Comparison to previous studies of flat surfaces indicates nanoscale corrugation strongly favors ice nucleation, implying surface corrugation will be an important aspect of the surface morphology on other natural or engineered surfaces.
- Published
- 2018
3. How Atomic Steps Modify Diffusion and Inter-adsorbate Forces: Empirical Evidence from Hopping Dynamics in Na/Cu(115)
- Author
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Karina Morgenstern, Holly Hedgeland, Andrew Jardine, Gil Alexandrowicz, Oded Godsi, T. Kravchuk, William Allison, Gefen Corem, John Ellis, C. Bertram, and Apollo - University of Cambridge Repository
- Subjects
0306 Physical Chemistry (incl. Structural) ,Condensed Matter::Quantum Gases ,Condensed Matter - Materials Science ,Materials Science (cond-mat.mtrl-sci) ,FOS: Physical sciences ,chemistry.chemical_element ,Nanotechnology ,Molecular physics ,Molecular dynamics ,Adsorption ,chemistry ,Physics::Atomic and Molecular Clusters ,Spin echo ,General Materials Science ,Physics::Atomic Physics ,Physical and Theoretical Chemistry ,Diffusion (business) ,Spectroscopy ,Anisotropy ,Helium ,Vicinal - Abstract
We followed the collective atomic-scale motion of Na atoms on a vicinal Cu(115) surface within a time scale of pico to nano-seconds using helium spin echo spectroscopy. The well defined stepped structure of Cu(115) allows us to study the effect that atomic steps have on the adsorption properties, the rate for motion parallel and perpendicular to the step edge and the interaction between the Na atoms. With the support of a molecular dynamics simulation we show that the Na atoms perform strongly anisotropic one dimensional hopping motion parallel to the step edges. Furthermore, we observe that the spatial and temporal correlations between the Na atoms which lead to collective motion are also anisotropic, suggesting the steps efficiently screen the lateral interaction between Na atoms residing on different terraces., 3 figures
- Published
- 2015
4. Two-Dimensional Wetting of a Stepped Copper Surface
- Author
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Gefen Corem, Chenfang Lin, Gil Alexandrowicz, Nadav Avidor, Andrew Hodgson, Oded Godsi, George R. Darling, Avidor, Nadav [0000-0002-3928-2493], and Apollo - University of Cambridge Repository
- Subjects
0306 Physical Chemistry (incl. Structural) ,Surface (mathematics) ,Materials science ,Pentamer ,Hydrogen bond ,General Physics and Astronomy ,chemistry.chemical_element ,02 engineering and technology ,Random hexamer ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Copper ,0104 chemical sciences ,Crystallography ,Dipole ,chemistry ,Molecule ,Wetting ,0210 nano-technology - Abstract
Highly corrugated, stepped surfaces present regular 1D arrays of binding sites, creating a complex, heterogeneous environment to water. Rather than decorating the hydrophilic step sites to form 1D chains, water on stepped Cu(511) forms an extended 2D network that binds strongly to the steps but bridges across the intervening hydrophobic Cu(100) terraces. The hydrogen-bonded network contains pentamer, hexamer, and octomer water rings that leave a third of the stable Cu step sites unoccupied in order to bind water H down close to the step dipole and complete three hydrogen bonds per molecule.
- Published
- 2017
5. A general method for controlling and resolving rotational orientation of molecules in molecule-surface collisions
- Author
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Jörg Meyer, Tsofar Maniv, Gil Alexandrowicz, Oded Godsi, Roman V. Krems, Gefen Corem, Geert-Jan Kroes, Joshua T. Cantin, M. F. Somers, and Yosef Alkoby
- Subjects
Surface (mathematics) ,Physics ,Multidisciplinary ,Magnetic moment ,Scattering ,Science ,General Physics and Astronomy ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Molecular physics ,General Biochemistry, Genetics and Molecular Biology ,Article ,Interferometry ,Classical mechanics ,Quantum state ,Orientation (geometry) ,0103 physical sciences ,Molecule ,010306 general physics ,0210 nano-technology ,Event (particle physics) - Abstract
The outcome of molecule–surface collisions can be modified by pre-aligning the molecule; however, experiments accomplishing this are rare because of the difficulty of preparing molecules in aligned quantum states. Here we present a general solution to this problem based on magnetic manipulation of the rotational magnetic moment of the incident molecule. We apply the technique to the scattering of H2 from flat and stepped copper surfaces. We demonstrate control of the molecule's initial quantum state, allowing a direct comparison of differences in the stereodynamic scattering from the two surfaces. Our results show that a stepped surface exhibits a much larger dependence of the corrugation of the interaction on the alignment of the molecule than the low-index surface. We also demonstrate an extension of the technique that transforms the set-up into an interferometer, which is sensitive to molecular quantum states both before and after the scattering event., The rotational orientation of a molecule plays a fundamental role in molecule-surface collisions, yet is difficult to study. Here, the authors present a general approach for controlling and resolving molecular rotational orientation and apply it to study H2 scattering from flat and stepped copper surfaces.
- Published
- 2017
6. Ordered H2O Structures on a Weakly Interacting Surface, A Helium Diffraction Study of H2O/Au(111)
- Author
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T. Kravchuk, J. R. Manson, Pepijn R. Kole, Gil Alexandrowicz, Gefen Corem, and Jianding Zhu
- Subjects
Diffraction ,Surface (mathematics) ,Materials science ,chemistry.chemical_element ,FOS: Physical sciences ,010402 general chemistry ,01 natural sciences ,0103 physical sciences ,Mesoscale and Nanoscale Physics (cond-mat.mes-hall) ,Physical and Theoretical Chemistry ,010306 general physics ,Helium atom scattering ,Helium ,Wetting layer ,Condensed Matter - Materials Science ,Condensed Matter - Mesoscale and Nanoscale Physics ,Ice crystals ,Materials Science (cond-mat.mtrl-sci) ,0104 chemical sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Amorphous solid ,General Energy ,chemistry ,Chemical physics ,Layer (electronics) - Abstract
In this manuscript we report helium atom scattering (HAS) measurements of the structure of the first H2O layer on Au(111). The interaction between H2O and Au(111) is believed to be particularly weak and conflicting evidence from several indirect studies has suggested that water either grows as 3D ice crystals or as an amorphous wetting layer. In contrast, our measurements show that between 110K and 130K, H2O grows as highly commensurate well ordered islands which only partially wet the gold surface. The islands produce a clear (sqrt3Xsqrt3)R30 diffraction pattern and are characterized by a well defined height of ~ 5 Angstrom with respect to the surface gold atoms. These findings provide support for a unique double bilayer model which has recently been suggested for this surface.
- Published
- 2015
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