Mössbauer study of the vibrational anisotropy and of the light-induced population of metastable states in single-crystalline guanidinium nitroprusside

M?ssbauer studies were performed on single crystals of guanidinium nitroprusside with different orientations of their principal crystallographic axes (a, b, c) with respect to the incident radiation. The markedly anisotropic Lamb-M?ssbauer factor f _LM , i.e. f _LM ^(a) = 0.118(8), f _LM ^(b) = 0.174(8), f _LM ^(c) = 0.202(8) is in contrast to that of nitroprussides with inorganic anions. The observed anisotropy is ascribed to the anisotropic vibrational mean-square displacement of the nitroprusside anions as a whole which is due to the specific packing of both, anions and cations, as well as the very weak chemical bonding between the ions, typical only for guanidinium nitroprusside. The vibrational anisotropy of iron atoms in barium nitroprusside that has been observed by X-ray structural investigations has a different origin and therefore does not result in an anisotropic Lamb-M?ssbauer factor. We have also investigated metastable states in guanidinium nitroprusside that have been populated by means of incoherent irradiation from light-emitting diodes. With a specific orientation of the guanidinium nitroprusside single crystal a population of the metastable states up to 26% could be achieved. Populations of comparable size on lithium, sodium and potassium nitroprussides have only been reached using coherent laser irradiation. Received 15 December 1998 and Received in final form 3 March 1999     

Far-Infrared Laser Stark Spectroscopy of CH3OD

The high resolution Stark spectra of the singly deuterated methanol isotope, CH₃OD, have been studied using the HCN laser with Stark fields up to approximately 60 000 V/cm. Numerous families of absorption lines have been observed in both parallel and perpendicular polarizations, resulting in the following assignments: with the 311 m line – J _K = 18₁ 18₀ E ₂, _t = 1; and with the 337 m line – J _k = 6₄ 5₃ E ₂, _t = 0 and J _K = 14₆ 13₅ A, _t = 1. Zero-field frequencies for the assigned transitions are in agreement with Fourier transform measurements and those calculated from the available molecular constants.     

Direct Fabrication Methods of Surface Relief Electro-Optic Gratings in Azo-Polymer Films

Two fabrication methods of surface relief electro-optic (EO) gratings in azo-polymer films are described: surface deformation by a continuous wave laser and laser ablation by a pulse laser. In the fabrication process, the periodic intensity modulation of laser beams is formed by an interference fringe or a phase mask. The surface relief EO grating is fabricated by poling the surface relief grating (SRG) after the SRG fabrication process. The linear dependence of an applied voltage in the modulation efficiency of the first-order diffraction beam is observed. The proposed methods are effective for highly-efficient surface relief EO grating fabrication.     

红外光谱中溶剂效应机理初探——配位机制的提出

本文就红外光谱中溶剂效应机理提出了溶质和溶剂分子间的瞬时配位作用机制，认为同－溶质在不同溶剂中的振动波数不同，是由于这种瞬时配位作用改变了溶质价电子运动状态所致。据此提出了溶剂效砂的定量关系式，测定了七种溶剂配位效应常数。用这一套经验参数处理了几种取代苯甲酸的羰基伸缩振动的溶剂效应，得较好的线性关系。还发现羰基的振动波数与取代基的Ｈａｍｍｅｔｔ常数σ之间，羰基伸缩振动对溶剂效应的敏感度与σ之间，Ｈ     

多孔硅发光与量子尺寸效应的实验研究

利用电化学阳极腐蚀的方法制备了多孔硅膜,实验发现多孔硅膜为多层结构,表面层为纳米结构,其余为微米结构,多孔硅的物理及化学结构的研究表明多孔硅是一种表面上含硅、氧、氢、氟元素组成的化合物包覆着的纳米晶硅粒和微米硅丝.多孔硅的发光主要来自表面纳米结构层,亚微米结构层并未见发光,从实验上证实了多孔硅的发光与量子尺寸效应紧密关联.     

用反向调制照明法分析光栅成像效应

提出了用反向调制照法明分析光栅成像效应的观点，研究了光栅系统的反向衍射干涉效应，成功地揭示了泰伯效应与劳效应的内在联系，并在白光双光栅衍射干涉的“消色效应”的基础上获得了白光扩展光源照明下白光光栅成像效应和具有实用意义的四光栅干涉系统。     

双稀土氧化物LnEuO3的Mossbauer效应研究

 本文首次利用高温高压方法合成了双稀土氧化物LaEuO₃、PrEuO₃、NdEuO₃和SmEuO₃。此外，还合成了CeEuO_3.5。X射线衍射分析表明LaEuO₃属A型（六方）结构，PrEuO₃、NdEuO₃和SmEuO₃属B型（单斜）结构，CeEuO_3.5属F型（萤石）结构。室温下用¹⁵¹Eu的21.6 eV γ射线测量了它们的Mossbauer谱，观察到了¹⁵¹Eu同质异能移位和四极劈裂强烈地依赖于Eu离子配位体体积而呈线性关系。超精细相互作用的这种体积效应，主要原因是由于Eu离子5s壳层的重叠畸变所引起。     

非均匀晶化Bi和Ba代替DyIG膜的法拉第效应研究

报道了快速循环晶化Ｂｉ和Ｂａ代替ＤｙＩＧ磁光膜的实验结果，发现在累加退火时间小于３分钟时（温度６５０～６８０℃）膜内部存在非晶区域和沿厚度晶化不均匀现象。导出晶相与非晶相界面法拉第角计算公式。计算结果表明，界面效应导致膜整体法拉第效应减弱。     

微通道板X射线探测器

在激光等离子体实验研究中,为了更好地了解激光与等离子体相互作用过程中所发生的物理过程,要求能够高时间分辨地观测等离子体所辐射的X射线的特征。测量的关键在于X射线探测元件,既要有快的时间响应,又要能够输出足够大的光电流,以便直接驱动高速示波器,进行显示和照像。普通的闪烁体/光电倍增管X射线探测器,由于闪烁体荧光有着固有的衰减时间,以及普通的光电倍增管中的电子飞行时间离散严重,时间分辨力难以提高。     

A branch-and-bound algorithm to minimize the line length of a two-sided assembly line

A new branch-and-bound algorithm is presented to solve the two-sided assembly line balancing problem of type 1 (TALB-1). First, a pair of two directly facing station is defined as a position, and then the two-sided assembly line (TAL) is relaxed to a one-sided assembly line (OAL). Some new lower bound on positions are computed, and dominance rules and reduction rules for the one-sided assembly line balancing problem of type 1 (OALB-1) are extended and incorporated into a station-oriented assignment procedure for the TALB-1 problem. Finally, the tests are carried out on a well-known benchmark set of problem instances, and experimental results demonstrate that the proposed procedure is efficient.