共查询到20条相似文献,搜索用时 46 毫秒
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Elisabeth Siebert Marius Horch Yvonne Rippers Dr. Johannes Fritsch Dr. Stefan Frielingsdorf Prof. Dr. Oliver Lenz Francisco Velazquez Escobar Prof. Dr. Friedrich Siebert Lars Paasche Dr. Uwe Kuhlmann Dr. Friedhelm Lendzian Prof. Dr. Maria‐Andrea Mroginski Dr. Ingo Zebger Prof. Dr. Peter Hildebrandt 《Angewandte Chemie (International ed. in English)》2013,52(19):5186-5186
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O. B. Tomilin A. N. Shchegolikhin E. P. Sanaeva A. N. Klyakin L. B. Ryabkina E. P. Konovalova 《Chemistry of Heterocyclic Compounds》2000,36(9):1097-1102
The temperature dependence of the ESR spectra of the radical-cations of the N-derivatives of phenothiazine were studied in the range of 200-393 K (o-xylene). It was established that at temperatures of 323-333 K the nature of the HFS varies from doublet to quartet with approximate intensity ratios of 1:2:2:1, and this transformation is irreversible. A hypothesis explaining the results is proposed. IR spectroscopy was used to confirm the proposed mechanism of localization of the unpaired electron. 相似文献
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This article reviews experimental efforts to control multiphoton transitions using shaped femtosecond laser pulses, and it lays out the systematic study being followed by us for elucidating the effect of phase on nonlinear optical laser-molecule interactions. Starting with a brief review of nonlinear optics and how nonlinear optical processes depend on the electric field inducing them, a number of conclusions can be drawn directly from analytical solutions of the equations. From a Taylor expansion of the phase in the frequency domain, we learn that nonlinear optical processes are affected only by the second- and higher-order terms. This simple result has significant implications on how pulse-shaping experiments are to be designed. If the phase is allowed to vary arbitrarily as a continuous function, then an infinite redundancy that arises from the addition of a linear phase function across the spectrum with arbitrary offset and slope could prevent us from carrying out a closed-loop optimization experiment. The early results illustrate how the outcome of a nonlinear optical transition depends on the cooperative action of all frequencies in the bandwidth of a laser pulse. Maximum constructive or destructive interference can be achieved by programming the phase using only two phase values, 0 and pi. This assertion has been confirmed experimentally, where binary phase shaping (BPS) was shown to outperform other alternative functions, sometimes by at least on order of magnitude, in controlling multiphoton processes. Here we discuss the solution of a number of nonlinear problems that range from narrowing the second harmonic spectrum of a laser pulse to optimizing the competition between two- and three-photon transitions. This Review explores some present and future applications of pulse shaping and coherent control. 相似文献
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In addition to the static parameters of the chemical shifts and coupling constants, which serve as a source of knowledge for molecular structure and stereochemistry, an NMR spectrum can frequently furnish dynamic quantities characterizing relaxation and exchange phenomena. The information about nuclear switching processes has proved to be particularly useful in practice for the detection of internal molecular motions and for the estimation or determination of the corresponding energy barriers. A plethora of studies of this nature has in the past been performed on simple proton spectra. Methodological developments of recent years have led to a significant reduction of the effort required for the quantitative dynamic evaluation of NMR spectra arising from complex spin systems or involving other nuclei. In many cases it has, moreover, become possible to extract detailed mechanistic information inaccessible by other means. The practical execution of such analyses will be explained and illustrated by a selected number of applications. 相似文献
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Multidimensional spectroscopic experiments offer fascinating insights into molecular structure and dynamics in the field of NMR spectroscopy. With the introduction of ultrafast two-dimensional infrared spectroscopy (2D-IR), multidimensional concepts have entered the optical domain, measuring couplings and correlations between molecular vibrations with femtosecond time resolution. In the transient 2D-IR (T2D-IR) experiments described in this minireview we exploit the high time resolution of 2D-IR to study transient species during fast nonequilibrium processes in real time. Information on molecular structure and dynamics is obtained that is not available from one-dimensional spectroscopy. We discuss examples from chemistry, physics and biophysics. 相似文献
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J?rg Enderlein Ingo Gregor Digambara Patra Thomas Dertinger U Benjamin Kaupp 《Chemphyschem》2005,6(11):2324-2336
Fluorescence correlation spectroscopy (FCS) has become an important tool for measuring diffusion, concentration, and molecular interactions of cellular components. The interpretation of FCS data critically depends on the measurement set-up. Here, we present a rigorous theory of FCS based on exact wave-optical calculations. Six of the most important optical and photophysical factors that influence FCS are studied: fluorescence anisotropy, cover-slide thickness, refractive index of the sample, laser-beam geometry, optical saturation, and pinhole adjustment. Our theoretical framework represents a general attempt to link all relevant parameters of the experimental set-up with the measured correlation function. 相似文献
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Inside Back Cover: Self‐Assembly of Measles Virus Nucleocapsid‐like Particles: Kinetics and RNA Sequence Dependence (Angew. Chem. Int. Ed. 32/2016) 下载免费PDF全文
Dr. Sigrid Milles Dr. Malene Ringkjøbing Jensen Dr. Guillaume Communie Damien Maurin Dr. Guy Schoehn Prof. Rob W. H. Ruigrok Dr. Martin Blackledge 《Angewandte Chemie (International ed. in English)》2016,55(32):9441-9441
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Inside Back Cover: Accelerating Diffusion‐Ordered NMR Spectroscopy by Joint Sparse Sampling of Diffusion and Time Dimensions (Angew. Chem. Int. Ed. 25/2014) 下载免费PDF全文
Mateusz Urbańczyk Prof. Dr. Wiktor Koźmiński Dr. Krzysztof Kazimierczuk 《Angewandte Chemie (International ed. in English)》2014,53(25):6569-6569
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Maria Fittipaldi Gertrud C M Warmerdam Ellen C de Waal Gerard W Canters Davide Cavazzini Gian Luigi Rossi Martina Huber Edgar J J Groenen 《Chemphyschem》2006,7(6):1286-1293
A 95 GHz pulsed deuterium ENDOR study has been performed on single crystals of azurin from Pseudomonas aeruginosa selectively deuterated at the C(beta) position of the copper-coordinating cysteine 112. Complete hyperfine tensors of the two deuterium atoms have been obtained, which reveal identical isotropic parts. Analysis of the hyperfine tensors provides insight into the spin-density delocalization over the cysteine ligand. Approximately 45 % of the spin density in the paramagnetic site can be attributed to copper and 30 % to sulfur. 相似文献
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Inside Cover: Molecular Recognition by a Short Partial Peptide of the Adrenergic Receptor: A Bottom‐Up Approach (Angew. Chem. Int. Ed. 20/2018) 下载免费PDF全文
Tsubasa Sekiguchi Masato Tamura Hikari Oba Dr. Pierre Çarçarbal Dr. Rolando Rafael Lozada‐Garcia Prof. Dr. Anne Zehnacker‐Rentien Dr. Gilles Grégoire Prof. Dr. Shun‐ichi Ishiuchi Prof.Dr. Masaaki Fujii 《Angewandte Chemie (International ed. in English)》2018,57(20):5558-5558
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Cover Picture: Dipolar Rotors Orderly Aligned in Mesoporous Fluorinated Organosilica Architectures (Angew. Chem. Int. Ed. 16/2015) 下载免费PDF全文
Dr. Silvia Bracco Dr. Mario Beretta Dr. Alice Cattaneo Prof. Angiolina Comotti Prof. Andrea Falqui Dr. Ke Zhao Prof. Charles Rogers Prof. Piero Sozzani 《Angewandte Chemie (International ed. in English)》2015,54(16):4681-4681
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J. Eric D. Davies Vivienne A. Tabner 《Journal of inclusion phenomena and macrocyclic chemistry》1997,27(2):179-190
Infrared, Raman and solid state 13C-NMR spectra have been recorded for a range of clathrates of Dianin's compound containing straight chain aliphatic carboxylic acids (formic - octanoic) as guests. The IR, Raman and NMR spectra can be satisfactorily interpreted in terms of dimer (formic and acetic) and monomer (propionic - octanoic) occupation of the cavities. The clathrates containing straight chain alcohol guests (methanol - octanol) have also been prepared to aid in the interpretation of the NMR data. 相似文献
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Gregor Hagelueken Dr. W. John Ingledew Dr. Hexian Huang Biljana Petrovic‐Stojanovska Chris Whitfield Prof. Hassane ElMkami Dr. Olav Schiemann Dr. James H. Naismith Prof. 《Angewandte Chemie (International ed. in English)》2009,48(16):2904-2906
Distance fingerprinting : Pulsed electron–electron double resonance spectroscopy (PELDOR) is applied to the octameric membrane protein complex Wza of E. coli. The data yielded a detailed distance fingerprint of its periplasmic region that compares favorably to the crystal structure. These results provide the foundation to study conformation changes from interaction with partner proteins.
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Xavier Carrier Povilas Lukinskas Stefan Kuba Lorenzo Stievano Friedrich E Wagner Michel Che Helmut Kn?zinger 《Chemphyschem》2004,5(8):1191-1199
The activity and selectivity of tungstated zirconia (WZ) for the conversion of n- into isopentane are dramatically enhanced when the catalyst is modified with Pt and Fe. The state of iron in these catalysts was hitherto only poorly characterized. Therefore, in the present work we investigated the structural and electronic properties of iron in WZ catalysts containing 1 wt% Pt and 1 wt% Fe2O3, by a combination of spectroscopic techniques, namely X-ray absorption spectroscopy (XAS), in situ electron paramagnetic resonance (EPR), and M?ssbauer spectroscopy. In the oxidized catalyst, iron is present as Fe(III) and predominantly forms a surface solid solution in which the isolated Fe(III) ions are located in a distorted octahedral environment. A small amount of the total iron (around 10%) is present in the form of small iron oxide particles. Both iron species can be reduced in H2 and then easily reoxidized on exposure to air at room temperature. We infer that the promoter action of iron in these catalysts is intimately related to its redox properties and specifically affects the dehydrogenation activity of the materials. 相似文献
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Theodor W. Hänsch Prof. 《Chemphyschem》2006,7(6):1170-1187
Optical frequency combs from mode-locked femtosecond lasers have revolutionized the art of counting the frequency of light. They can link optical and microwave frequencies in a single step, and they provide the long missing clockwork for optical atomic clocks. By extending the limits of time and frequency metrology, they enable new tests of fundamental physics laws. Precise comparisons of optical resonance frequencies of atomic hydrogen and other atoms with the microwave frequency of a cesium atomic clock are establishing sensitive limits for possible slow variations of fundamental constants. Optical high harmonic generation is extending frequency comb techniques into the extreme ultraviolet, opening a new spectral territory to precision laser spectroscopy. Frequency comb techniques are also providing a key to attosecond science by offering control of the electric field of ultrafast laser pulses. In our laboratories at Stanford and Garching, the development of new instruments and techniques for precision laser spectroscopy has long been motivated by the goal of ever higher resolution and measurement accuracy in optical spectroscopy of the simple hydrogen atom which permits unique confrontations between experiment and fundamental theory. This lecture recounts these adventures and the evolution of laser frequency comb techniques from my personal perspective. 相似文献
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Two-dimensional infrared (2D IR) spectroscopy is used to study atactic polystyrene. 2D IR is a technique based on time-resolved detection of IR signals in response to an external perturbation, such as mechanical strain. Since different chemical functional groups respond to the applied perturbation at unique and often different rates, characteristic time-dependent variations of the IR-band intensities are observed. Correlation analysis of the dynamic variation of the IR signals yields a new spectrum defined by two independent wave numbers. Peaks located on a 2D IR spectral plane imply interactions and connectivities among chemical functional groups. By spreading convoluted IR bands over two dimensions, the spectral resolution is also greatly enhanced. 相似文献