Using photoelectron emission microscopy with hard-X-rays

We present several successful test cases of using photoelectron emission microscopy (PEEM) for photon energy up to 25 keV. First, the full extended X-ray absorption fine structure analysis was implemented in areas as small as 100 μm² for transition-metal K edge absorption spectra and, therefore, demonstrated the feasibility of combining structural and chemical analysis with hard-X-ray absorption spectroscopy with high lateral resolution. We also show that PEEM can be used in a transmission (radiography) mode as an imaging detector for hard-X-ray. This approach again leads to the unprecedented 0.3 μm lateral resolution, particularly critical for the use of coherence-based phase contrast techniques in real time X-ray radiology.     

Coadsorption of water and CO molecules on Ru(0 0 1) at high CO coverages: comparisons with a Ru(0 0 1) electrode surface

The coadsorption of carbon monoxide (CO) and water molecules on a Ru(0 0 1) surface has been studied by infrared spectroscopy, LEED and STM. At high CO coverage phases, a 2×2-(2CO+D₂O) structure was observed on both UHV and electrode surfaces. Electrode potential dependent structures from CO and water adlayers on an electrode surface were reproduced on a UHV surface by controlling molecular orientations of the first layer and second over-layer water molecules. At lower CO coverages, a CO band center showed coverage dependent shift down to 1444 cm⁻¹ due to an electron transfer from a lone pair of a water molecule to CO 2π^*.     

A pulse-train laser driven XUV source for picosecond pump–probe experiments in the water window

We describe the development of a table top soft X-ray source based on a laser produced plasma. The plasma is produced by a Nd:YLF pulse-train laser which delivers pulse trains of up to 400 pulses each of about 25 ps duration. Number and energy of the micropulses are fully computer controlled adjustable for an optimum interaction with a rotating solid target. Spectral, spatial and temporal characteristics of the X-ray emission from Mylar and copper targets have been studied. A calibrated back-illuminated CCD camera together with a slit grating spectrograph were utilized for the measurement of the absolute soft X-ray photon fluxes. The temporal measurements were performed using a streak camera while the plasma size was measured with a zone plate. An application of the system in a X-ray absorption experiment is shown. The advantages of the system in view of possible optical pump and soft X-ray probe experiments will be discussed.     

Modeling of IR Spectra of Selectively Substituted Glucopyranoside Nitrates

The frequencies of the normal vibrations of the molecules of 2,6- and 3,6-di-O-nitro-methyl--D-glucopyranosides and 2,3,6-tri-O-nitro-methyl--D-glucopyranoside have been calculated within the valence-force-field approximation in combination with calculation of the absolute intensities of the IR absorption bands of these molecules by the CNDO/2 method. The regularities in the structure of the complex IR absorption bands characteristic for nitro groups formed as a result of selective nitrosubstitution have been explained.     

Experimental and theoretical lifetimes in Yb III

Lifetimes of three levels belonging to the configuration 4f ¹³5d with J = 1 in Yb III have been measured for the first time using the time-resolved laser-induced fluorescence method. Experimental transition probabilities have been deduced for the transitions between the levels studied and the ground state. The comparison of the experimental lifetimes with theoretical data, deduced within the relativistic Hartree-Fock (HFR) approach, underlines the dramatic importance of an adequate consideration of core-polarization effects in the theoretical model and the sensitivity of one of the lifetime values to small correlation effects. Received 2 April 2001     

Magnetic Resonance of Chromium (V) with 2–Hydroxy–2–Ethylbutyrates

A complex of Cr (V) with 2–hydroxy–2–ethylbutyric acid (EHBA) has been studied experimentally by the method of electron spin resonance (ESR). The tensor components of the g–factor, the dependences of the ESR line widths on the concentration of paramagnetic centers, and the SHF power of saturation are determined. It is shown that the main mechanism of dynamic polarization of nuclei in the EHBACr^V complex in a propanediol solution is the mechanism of dynamic cooling with a burnt hole. It has been established that the ESR spectra of the EHBACr^V solutions in deuterated and ordinary propanediol display practically the same behavior, which is indicative of the good solubility of the complex in deuterated alcohols.     

Overlapping B3Π0u ← X1Σ g/+ and 1Π1u ← X1Σ g/+ non-radiative characteristic of Br2 vapour in the wavelength region 505–541 nm

The vibronic vapour phase photoacoustic spectrum of Br₂ in the wavelength region 505–541 nm (19796–18480 cm⁻¹) has been recorded using microphone as well as pump-probe method. Discrete vibronic bands superimposed on a monotonically increasing continuum background towards the dissociation limit results from the overlapping B ³Π _0u ^/+ ← X ¹Σ _g ^/+ and ¹Π_1u ← X ¹Σ _g ^/+ electronic transitions. Vibronic bands originating from υ″=0 have been used to estimate the relative rate of non-radiative relaxation as a function of the excited state B ³Π_0u vibrational quantum number υ′. A comparison with the optical absorption spectroscopy of Br₂ leads to the identification of three broad spectral regions between 505 and 541 nm (19796 and 18480 cm⁻¹) on the basis of different non-radiative relaxation processes.     

利用可见近红外光谱多指标综合预测生鲜牛肉储存期

建立了牛肉基于TVB-N、菌落总数、pH值和肉色参数L*多个指标的储存期预测模型,利用可见近红外光谱(Vis/NIR)技术结合区间偏最小二乘(iPLS)和遗传算法(GA)建立了各个指标的PLS预测模型,实现了多指标综合无损快速预测4 ℃下牛肉的储存期。用iPLS和iPLS-GA提取有效波长变量建立PLS预测模型,以预测相关系数和预测标准差作为模型评价标准,结果表明用iPLS-GA选择变量建立的各个指标的PLS预测模型均优于全波段和iPLS组合的PLS模型。由多个指标的预测值和储存期的预测模型,对校正集和预测集样品储存期进行预测,其预测相关系数和标准差分别是0.903, 0.897和1.88, 2.24。说明利用光谱技术结合得出的储存期预测模型可以实现多指标综合预测牛肉储存期,为无损快速检测牛肉储存期或货架期提供了一种新方法。      

苯海拉明的拉曼光谱和红外光谱研究

测量并分析了盐酸苯海拉明的红外光谱和拉曼光谱。在Raman光谱中, 1001 cm-1出现一个极强峰, 在1030 cm-1和618 cm-1各有一个中等峰,此外,在红外光谱中, 714 cm-1和757 cm-1附近出现极强的吸收峰,认定这个化合物中存在单取代苯。C-N的对称伸缩振动出现在837 cm-1, 1433 cm-1和1470 cm-1分别为CH2和CH3的变形振动, 在红外光谱中, 1020 cm-1处明显的吸收峰属于C-O-C反对称伸缩振动。此外, 测量得到含量为25 mg苯海拉明药片的拉曼光谱与纯苯海拉明的拉曼峰比较一致, 可作为无损快速检测该药物的手段。     

ZrV2-xPxO7固溶体的相变与热膨胀性质的研究

本文采用固相烧结法制备了ZrV2-xPxO7@=0,0．2,0．4,0．6,0．8,1）系列材料．粉末X射线衍射（XRD）分析表明,所制备材料的结构为单一立方相．应用变温拉曼光谱研究该材料相变,变温拉曼光谱研究结果表明,材料起始相变温度随着P5＋替代V5＋量的增加逐渐降低,x=0,0．4,0．8,1对应的相变温度分别为383K,363K,273K,213K．热膨胀测试结果表明：随着P替代量的增加正一负膨胀转变温度先降低后增加,x=0,0．2,0．4,0．6,0．8,1对应的正一负膨胀转变温度分别为429K,403K,372K,390K,398K和435K．本文指出了该系列材料存在两个相变过程,为设计和制备ZrV2O7基室温附近的负热膨胀材料奠定了良好的基础．