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51.
52.
We show that when water droplets gently impact on a hydrophobic surface, the droplet shoots out a violent jet, the velocity of which can be up to 40 times the drop impact speed. As a function of the impact velocity, two different hydrodynamic singularities are found that correspond to the collapse of the air cavity formed by the deformation of the drop at impact. It is the collapse that subsequently leads to the jet formation. We show that the divergence of the jet velocity can be understood using simple scaling arguments. In addition, we find that very large air bubbles can remain trapped in the drops. The surprising occurrence of the bubbles for low-speed impact is connected with the nature of the singularities, and can have important consequences for drop deposition, e.g., in ink-jet printing. 相似文献
53.
Hendry E Koeberg M Wang F Zhang H de Mello Donegá C Vanmaekelbergh D Bonn M 《Physical review letters》2006,96(5):057408
We independently determine the subpicosecond cooling rates for holes and electrons in CdSe quantum dots. Time-resolved luminescence and terahertz spectroscopy reveal that the rate of hole cooling, following photoexcitation of the quantum dots, depends critically on the electron excess energy. This constitutes the first direct, quantitative measurement of electron-to-hole energy transfer, the hypothesis behind the Auger cooling mechanism proposed in quantum dots, which is found to occur on a 1 +/- 0.15 ps time scale. 相似文献
54.
In the present work, poly(glycidyl methacrylate-co-divinylbenzene) monoliths were synthesized and further derivatized to obtain strong anion exchange supports. Capillary monoliths (65 x 0.2 mm id) were prepared in situ by copolymerization of glycidyl methacrylate and divinylbenzene, employing 1-decanol and tetrahydrofuran as porogens. The free epoxy groups were derivatized in a two step synthesis to obtain quaternary ammonium functionalities. On testing the pressure stability of the synthesized monolith, a highly linear dependence between flow rate and pressure drop was obtained, indicating the high stability of the material even at high flow rates. The morphology of the copolymer was investigated by scanning electron microscopy. Mercury intrusion porosimetry showed a narrow pore size distribution, having a maximum at 439 nm. On recording a van Deemter plot the number of theoretical plates per meter was found to be 59324. The produced strong anion exchange monoliths turned out to be highly suitable for the separation of nucleotides and oligonucleotides. 相似文献
55.
We investigate the thermal fluctuations of the colloidal gas-liquid interface subjected to a shear flow parallel to the interface. Strikingly, we find that the shear strongly suppresses capillary waves, making the interface smoother. This phenomenon can be described by introducing an effective interfacial tension that increases with the shear rate. The increase of sigma(eff) is a direct consequence of the loss of interfacial entropy caused by the flow, which affects especially the slow fluctuations. This demonstrates that the interfacial tension of fluids results from an intrinsic as well as a fluctuation contribution. 相似文献
56.
Jene D. Cyran Ellen H. G. Backus Marc‐Jan vanZadel Mischa Bonn 《Angewandte Chemie (International ed. in English)》2019,58(11):3620-3624
Small organic molecules on ice and water surfaces are ubiquitous in nature and play a crucial role in many environmentally relevant processes. Herein, we combine surface‐specific vibrational spectroscopy and a controllable flow cell apparatus to investigate the molecular adsorption of acetone onto the basal plane of single‐crystalline hexagonal ice with a large surface area. By comparing the adsorption of acetone on the ice/air and the water/air interface, we observed two different types of acetone adsorption, as apparent from the different responses of both the free O?H and the hydrogen‐bonded network vibrations for ice and liquid water. Adsorption on ice occurs preferentially through interactions with the free OH group, while the interaction of acetone with the surface of liquid water appears less specific. 相似文献
57.
Sudipta Das Mischa Bonn Ellen H. G. Backus 《Angewandte Chemie (International ed. in English)》2019,58(44):15636-15639
The behavior of hydroxide and hydrated protons, the auto‐ionization products of water, at surfaces is important for a wide range of applications and disciplines. However, it is unknown at which bulk concentration these ions start to become surface active at the water–air interface. Here, we report changes in the D2O–air interface in the presence of excess D+hyd/OD?hyd determined using surface‐sensitive vibrational sum‐frequency generation (SFG) spectroscopy. The onset of the perturbation of the D2O surface occurs at a bulk concentration as low as 2.7±0.2 mm D+hyd. In contrast, a concentration of several hundred mm OD?hyd is required to change the D2O surface. The hydrated proton is thus orders of magnitude more surface‐active than hydroxide at the water–air interface. 相似文献
58.
Jaudet C Vignolles D Audouard A Levallois J LeBoeuf D Doiron-Leyraud N Vignolle B Nardone M Zitouni A Liang R Bonn DA Hardy WN Taillefer L Proust C 《Physical review letters》2008,100(18):187005
The de Haas-van Alphen effect was observed in the underdoped cuprate YBa2Cu3O6.5 via a torque technique in pulsed magnetic fields up to 59 T. Above a field of approximately 30 T the magnetization exhibits clear quantum oscillations with a single frequency of 540 T and a cyclotron mass of 1.76 times the free electron mass, in excellent agreement with previously observed Shubnikov-de Haas oscillations. The oscillations obey the standard Lifshitz-Kosevich formula of Fermi-liquid theory. This thermodynamic observation of quantum oscillations confirms the existence of a well-defined, closed, and coherent, Fermi surface in the pseudogap phase of cuprates. 相似文献
59.
Xia J Schemm E Deutscher G Kivelson SA Bonn DA Hardy WN Liang R Siemons W Koster G Fejer MM Kapitulnik A 《Physical review letters》2008,100(12):127002
The polar Kerr effect in the high-T_(c) superconductor YBa2Cu3O6+x was measured at zero magnetic field with high precision using a cyogenic Sagnac fiber interferometer. We observed nonzero Kerr rotations of order approximately 1 microrad appearing near the pseudogap temperature T(*) and marking what appears to be a true phase transition. Anomalous magnetic behavior in magnetic-field training of the effect suggests that time reversal symmetry is already broken above room temperature. 相似文献
60.
Dr. J. Rodriguez J. Bonn Dipl.-Phys. Dr. G. Huber Dr. H. -J. Kluge Prof. Dr. E. W. Otten 《Zeitschrift für Physik A Hadrons and Nuclei》1975,272(4):369-374
Neutron rich205Hg (T 1/2=5.2 min) was produced and on-line mass separated at the ISOLDE facility at CERN. The polarization achieved by optical pumping via the atomic line (6s 21 S 0?6s6p 3 P 1,λ=2 537Å) was monitored by theβ decay asymmetry. Hyperfine structure and isotopic shift of the205Hg absorption line was determined by Zeeman scanning. In addition a magnetic resonance was performed on the polarized205Hg nuclei in the atomic ground state. The results are: \(I(^{205} Hg) = \tfrac{1}{2}\) (confirmed);μ I (205Hg)=0.5915 (1)μ N (uncorrected for diamagnetism); isotopic shiftδv204/205=v(205Hg)-v(204Hg)=?1.8 (1) GHz.μ I and IS are discussed briefly in the frame of current literature. 相似文献