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991.
Strongly correlated systems far from equilibrium can exhibit scaling solutions with a dynamically generated weak coupling. We show this by investigating isolated systems described by relativistic quantum field theories for initial conditions leading to nonequilibrium instabilities, such as parametric resonance or spinodal decomposition. The nonthermal fixed points prevent fast thermalization if classical-statistical fluctuations dominate over quantum fluctuations. We comment on the possible significance of these results for the heating of the early Universe after inflation and the question of fast thermalization in heavy-ion collision experiments. 相似文献
992.
Lestinsky M Lindroth E Orlov DA Schmidt EW Schippers S Böhm S Brandau C Sprenger F Terekhov AS Müller A Wolf A 《Physical review letters》2008,100(3):033001
Term energies for dielectronic-recombination Rydberg resonances below 0.07 eV are determined for Sc18+ with absolute accuracies below 0.0002 eV by electron collision spectroscopy in an ion storage ring, using the twin-electron-beam technique and a cryogenic photocathode. The lithiumlike 2s_{1/2}-2p_{3/2} transition energy for Z=21 is determined to 4.6 ppm, less than 1% of the few-body effects on radiative corrections. Features from the hyperfine structure of the 2s state could be resolved in the dielectronic-recombination spectrum. 相似文献
993.
D. A. Shapiro H. N. Chapman D. DePonte R. B. Doak P. Fromme G. Hembree M. Hunter S. Marchesini K. Schmidt J. Spence D. Starodub U. Weierstall 《Journal of synchrotron radiation》2008,15(6):593-599
Atomic‐resolution structures from small proteins have recently been determined from high‐quality powder diffraction patterns using a combination of stereochemical restraints and Rietveld refinement [Von Dreele (2007), J. Appl. Cryst. 40 , 133–143; Margiolaki et al. (2007), J. Am. Chem. Soc. 129 , 11865–11871]. While powder diffraction data have been obtained from batch samples of small crystal‐suspensions, which are exposed to X‐rays for long periods of time and undergo significant radiation damage, the proof‐of‐concept that protein powder diffraction data from nanocrystals of a membrane protein can be obtained using a continuous microjet is shown. This flow‐focusing aerojet has been developed to deliver a solution of hydrated protein nanocrystals to an X‐ray beam for diffraction analysis. This method requires neither the crushing of larger polycrystalline samples nor any techniques to avoid radiation damage such as cryocooling. Apparatus to record protein powder diffraction in this manner has been commissioned, and in this paper the first powder diffraction patterns from a membrane protein, photosystem I, with crystallite sizes of less than 500 nm are presented. These preliminary patterns show the lowest‐order reflections, which agree quantitatively with theoretical calculations of the powder profile. The results also serve to test our aerojet injector system, with future application to femtosecond diffraction in free‐electron X‐ray laser schemes, and for serial crystallography using a single‐file beam of aligned hydrated molecules. 相似文献
994.
T. Eidam F. Röser O. Schmidt J. Limpert A. Tünnermann 《Applied physics. B, Lasers and optics》2008,92(1):9-12
We report on the generation of 27 fs pulses with an average output power of 57 W and a repetition rate of 78 MHz. The pulses
are generated by combining a high average power fiber chirped pulse amplification (FCPA) system with a microstructured large-mode-area
fiber for nonlinear compression. The FCPA system delivers 270 fs pulses in a linearly polarized beam with diffraction-limited
quality. Nonlinear compression is achieved by launching the pulses into a short (few cm) piece of microstructured fiber and
subsequent compression by a pair of chirped mirrors.
PACS 42.55.Wd; 42.55.Xi, 42.65.Re 相似文献
995.
Roland Schmidt Erik McNellis Wolfgang Freyer Daniel Brete Tanja Gießel Cornelius Gahl Karsten Reuter Martin Weinelt 《Applied Physics A: Materials Science & Processing》2008,93(2):267-275
Self-assembled monolayers (SAMs) of 4-trifluoromethyl-azobenzene-4′-methyleneoxy-alkanethiols (CF3– C6H4–N=N–C6H4–O–(CH2)
n
–SH on (111)-oriented poly-crystalline gold films on mica were examined by X-ray photoelectron spectroscopy (XPS) and X-ray
absorption spectroscopy (XAS). The spectra are analyzed with the help of density-functional-theory calculations of the isolated
molecule. Only one doublet is detected in the sulphur 2p spectra of the investigated SAMs, consistent with a thiolate bond of the molecule to the gold surface. The C 1s XP spectra and the corresponding XAS π
* resonance exhibit a rich structure which is assigned to the carbon atoms in the different chemical surroundings. Comparing
XPS binding energies of the azobenzene moiety and calculated initial-state shifts reveals comparable screening of all C 1s core holes. While the carbon 1s XPS binding energy lies below the π
*-resonance excitation-energy, the reversed order is found comparing core ionization and neutral core excitation of the nitrogen 1s core-hole of the azo group. This surprising difference in core-hole binding energies is interpreted as site-dependent polarization
screening and charge transfer among the densely packed aromatic moieties. We propose that a quenching of the optical excitation
within the molecular layer is thus one major reason for the low trans to cis photo-isomerization rate of azobenzene in aromatic-aliphatic
SAMs. 相似文献
996.
P. Dietrich F. Michalik R. Schmidt C. Gahl G. Mao M. Breusing M. B. Raschke B. Priewisch T. Elsässer R. Mendelsohn M. Weinelt K. Rück-Braun 《Applied Physics A: Materials Science & Processing》2008,93(2):285-292
A mild and efficient procedure has been developed to obtain covalently attached self-assembled monolayers (SAMs) on Si(111)
with photochromic azobenzene head-groups. Starting from neat or diluted carboxylic acid functionalized monolayers on-chip
coupling reactions were applied to attach hydroxyl-functionalized azobenzene units to the SAMs by ester bond formation. The
modified surfaces were characterized by high-resolution X-ray photoelectron spectroscopy (XPS), transmission Fourier transform
infrared spectroscopy (FT-IR), and contact angle measurements. Reversible cis
↔
trans isomerizations of photoswitchable SAMs were monitored by wettability measurements.
Electronic Supplementary Material The online version of this article () contains supplementary material, which is available to authorized users.
Dedicated with respect and compliments to Professor Helmut Schwarz on the occasion of his 65th birthday. 相似文献
997.
Analysis of dye degradation products and assessment of the dye purity in dye‐sensitized solar cells
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998.
999.
1000.
Mathias Mallmann Sebastian Wendl Dr. Philipp Strobel Dr. Peter J. Schmidt Prof. Dr. Wolfgang Schnick 《Chemistry (Weinheim an der Bergstrasse, Germany)》2020,26(28):6257-6263
Nitridophosphates exhibit an intriguing structural diversity with different structural motifs, for example, chains, layers or frameworks. In this contribution the novel nitridophosphate Sr3P3N7 with unprecedented dreier double chains is presented. Crystalline powders were synthesized using the ammonothermal method, while single crystals were obtained by a high-pressure multianvil technique. The crystal structure of Sr3P3N7 was solved and refined from single-crystal X-ray diffraction and confirmed by powder X-ray methods. Sr3P3N7 crystallizes in monoclinic space group P2/c. Energy-dispersive X-ray and Fourier-transformed infrared spectroscopy were conducted to confirm the chemical composition, as well as the absence of NHx functionality. The optical band gap was estimated to be 4.4 eV using diffuse reflectance UV/Vis spectroscopy. Upon doping with Eu2+, Sr3P3N7 shows a broad deep-red to infrared emission (λem=681 nm, fwhm≈3402 cm−1) with an internal quantum efficiency of 42 %. 相似文献