Aktivierungsanalytische Bestimmung von Spurenelementen in Tomaten

Die Autoren machen mit aktivierungsanalytischen Untersuchungen am Reaktor der Technischen Universität Budapest bekannt. Der thermische Neutronenfluβ war 2·10¹¹ ncm^?28^?1, und es wurde ein Ge(Li)-Detektor mit 25 cm³ Volumen und einer Energieauflösung von 2 keV angewendet. Die untersuchten Tomatenproben enthielten durchschnittlich 85% Trockensubstanz. Es wurden folgende Konzentrationen an Spurenelementen ermittelt (in mg/kg): Br: 50,1; Mn: 10,2; Zn: 9,3; Cu: 6,6; As: 0,051; Sb:0,030; Au: 0,005.     

Optical study of RE 1 + x Ba 2 - x Cu 3 O 6 (RE = Nd, Sm) aaand YBa 2 Cu 3 O 6 in the mid infrared range

Infrared reflectance, and transmission measurements as well as Raman scattering have been used to study the RE_1+xBa_2-xCu₃O₆ (RE = Nd, Sm) and YBa₂Cu₃O₆ absorption bands in the 1100-1500 cm^-1 infrared range as a function of temperature and beam polarization. In addition to two-phonon absorption between 1100 and 1170 cm^-1, we observe excitations around 1400 cm^-1, occurring in oxygen rich enclosures within the samples, and assign them to an excitation involving two-phonons plus the 270 cm^-1 local mode related to Cu-O broken chains. Thus, the previously reported possible magnetic origin of the 1436 cm^-1 sharp absorption band in YBa₂Cu₃O₆ is contested. Received 14 February 2001 and Received in final form 12 April 2001     

非金属二元氢化物pka与量子化学参数的关系

在HF／3－21G水平下，对13种非金属二元氢化物分子（HF，HCl,HBr,HI,H2O,H2S,H2Se,H2Te,NH3,PH3,AsH3,CH4和SiH4)进行了几何构型全优化和电子结构计算，将获得的电子结构数据与这些分子的pka值相关联，进行逐步回归分析，结果显示，pka与非氢原子的键价，分子的最低空轨道能间存在显的二元线性相关性，相关系数R＝0．994。pka计算值与实验值符合得较好，表明非金属二元氢化物中非氢原子的键价，分子的最低空轨道能在决定其酸性上起重要作用。     

Plasma dynamics in GaAs under strong picosecond surface excitation

We have investigated the time-resolved luminescence of GaAs in air at room temperature, under strong picosecond surface excitation. The energy density was in the range 4–40 $\text{mJ}\text{cm}{}^2$ and the excitation wavelength λ_ex ? 0.53 μ. The peak temperature reached by the generated electron-hole plasma at the end of the excitation pulse amounts to T_M ? 720 K at an energy density of about 10 $\text{mJ}\text{cm}{}^2$. Further increase of the power induces surface damage on the sample. The plasma relaxes its kinetic energy at a slow rate of the order of 10¹⁰$\text{eV}\text{s}$, supporting our previous calculations which concluded that electron-phonon interactions are strongly screened by intravalley free-carrier collisions at high plasma density, so that the plasma cooling slows down.     

非金属元素的微波诱导等离子体原子发射光谱法测定

本文系统地综述了微波诱导等离子体原子发射光谱法(MIP-AES)在测定痕量非金属元素C、N、H、O、S、P和卤素等方面的应用。     

Inductively Coupled Plasma Optical Emission Spectrometry in the Vacuum Ultraviolet Region

Abstract

Inductively coupled plasma optical emission spectrometry has been applied for trace metal determination in a myriad of sample types. However, the detection of nonmetals is a challenge. For example, the high excitation energies associated with most nonmetals is a barrier for populating the excited state of these elements. Even in the presence of sufficient excitation energy, the principal resonance lines for nonmetals usually lie in the vacuum ultraviolet region, where atmospheric species like oxygen and water vapor absorb the radiation. Several nonmetals (nitrogen, oxygen, and carbon) are also present in the atmosphere, so contamination or background emission signals can hinder quantification. A common approach to solving these problems is to increase throughput by purging the optical path with an inert gas. In addition, unnecessary mirrors or lenses are eliminated when possible. This review provides a survey of the applications of inductively coupled plasma optical emission spectrometry in the vacuum ultraviolet region, with particular emphasis on the detection of sulfur, phosphorus, iodine, and carbon. The alternative of employing nonresonance lines for these elements in the near-infrared region is discussed briefly as well.     

非金属二元氢化物分子振动固有频率与pKa常数的定量关系

提出了非金属二元氢化物分子振动固有频率的计算原理与方法.将基频和总频作为结构信息指数用于非金属二元氢化物的分子结构与pK_a常数的定量关系研究,结果表明,其相关系数大于0.995,得到的回归方程用于pK_a的计算,计算值与实验值比较,平均绝对误差小于1.82.