磁场中简并四波混频的偏振旋转效应

本文讨论了磁场中简并四波混频的偏振旋转效应。计算了J_g=0→J_e=1跃迁的三阶非线性极化率X_yxx⁽³⁾。它包括两个部分:一部分是由于布居差的饱和效应产生的;另一部分是由于原子与光场的相互作用中,感生出来的塞曼相干所造成的。 关键词：     

A LEED determination of the structures of Ru(001) and of CORu(001)−√3 × √3 R30°

The structures of Ru(001) and of the √3 × √3 R30° overlayer of CO on Ru(001) have been determined by LEED I–V measurements and comparison to calculations. Special attention was paid to accurate angular alignment, selection of a well-ordered portion of the surface, and avoidance of beam-induced changes of the CO layer. Five orders of reflexes over a range of 300 eV each were used for the clean surface and 7 orders over 200 eV each for the CO superstructure. For the clean surface, a slight contraction of the first layer spacing (by 2%) was found which gave r-factors of 0.04 (Zanazzi-Jona) and 0.16 (Pendry) for 5 non-degenerate beams. For the CO structure the most probable geometry is the on-top site with spacings $\text{d(}\text{RuC}\text{) = 2.0 ± 0.1}\text{A}\text{?}\text{and}\text{d(}\text{CO}\text{) = 1.10 ± 0.1}\text{A}\text{?}\text{(r}{}_{\mathrm{<mtext>ZJ</mtext>}}\text{= 0.21; r}{}_{\mathrm{<mtext>P</mtext>}}\text{= 0.51)}$. The two threefold hollow and the bridge sites can be clearly excluded.     

Electron stimulated desorption of O+ ions: Energy dependence of the desorption efficiency from adsorbed oxygen on metal surfaces and its bearing on the mechanism

Measurements of the structure in the curve of desorption yield versus electron energy for ESD of O⁺ from β₁-oxygen on polycrystalline W and W(100), and from oxidized V are reported. They show definite structure around the core ionization thresholds of the metal atoms. This may be taken as evidence for the existence of Auger mechanisms of ESD, e.g. that proposed recently by Knotek and Feibelman for oxidic oxygen.     

Tuning the surface hydrophobicity of polymer/nanoparticle composite films in the Wenzel regime by composition

Surface hydrophobicity of composite films containing polymer and nanoparticles has been studied as a function of composition. We show that the hydrophobicity can be tuned by adjusting the amount of particles in the two-component system. A sharp transition from a polymer-rich surface to a nanoparticles-rich surface was observed with increasing mass fraction of particles in spin-coated thin films. Water drops on the films did not slide down even at tilt angles of 90 degrees . Contact angle hysteresis increased with the mass fraction of particles indicating that the surface roughness increased as the surfaces remained in the Wenzel regime. Contact angle hysteresis data were quantitatively consistent with predictions of a recent theory.     

High-throughput biomarker discovery and identification by mass spectrometry

Native peptides and proteins are of increasing interest in biomedical research because they hold promise to represent a large number of useful diagnostic and therapeutic biomarkers. Discovery attempts from patient samples have to deal with the complexity of biology from a disease perspective as well as with a high individual variability. High throughput screening of samples is therefore the strategy of choice to detect relevant peptidic biomarkers, and requires a high order of automation particularly in the detection process. In this contribution, a novel technical approach employing a fully automated MALDI-TOF/TOF mass spectrometer is described. This approach combines high throughput biomarker discovery with the identification of corresponding endogenous peptides in one instrument and from the same set of samples. The degree of automation allows the analysis of thousands of chromatographic fractions corresponding to up to one hundred patient samples per day. The applied relative quantification via Differential Peptide Display((R)) is performed in a label-free way and shows a dynamic range of up to four orders of magnitude in the accessible peptide concentrations. The typical limit of detection is in the mid- to low-picomolar range for body fluids such as blood plasma, urine and cerebrospinal fluid. Sequence assignment via MALDI-TOF/TOF mass spectrometry is carried out either in an overview approach, characterizing rapidly the peptide composition e.g. of a novel sample, or in a directed approach, analyzing a list of biomarker candidates deduced from statistically significant abundance differences from the biomarker discovery process.     

Lichtmikroskopie mit mechanischer Vorvergrößerung

By mechanically stretching a rubber replica prior to examination, the limits of resolution of the light microscope (according to Abbe) may be surpassed without the expenditure of any surplus energy. Replica and stretching can be described by a relief transfer function similar to that used in the optical transfer theory. This function was attained from the transfer of a step of mica. It is possible to describe the process as a linear transfer channel within the limits given.     

简并四波混频中的能级交叉效应

我们用微扰方法计算了近简并准二能级系统的三阶非线性极化率x⁽³⁾(-ω;ω,ω,-ω)。研究了简并四波混频的能级交叉效应,并与共振荧光的能级交叉效应比较。指出简并四波混频的能级交叉效应可用来测量上能级及下能级的弛豫速率。 关键词：     

Optische Konstanten von massivem Nickel und Eisen

The optical constants were measured by elliptical analysis of the reflected light in the visible region. The surface of the bulk specimen were untouched by any physical or chemical treatment. In this way the results seem to give the real optical constants.     

Electron stimulated desorption: Principles and recent developments

A survey is given of the basic experimental findings in electron stimulated desorption and of the accepted theoretical model for their explanation. As an example for the test of the theory, the isotope effect in ESD of hydrogen on tungsten surfaces is described, which shows excellent agreement with the predictions of the model. The use of ESD as a surface probe is exemplified with recent work on hydrogen adsorption states on tungsten; the need for generalization of the one-dimensional model to three dimensions becomes clear in this case. Recent developments in theory (a quantum-mechanical treatment of the process) and experiment (promising measurements of the angular distribution of ionic ESD) are shortly discussed.