On the electronic structure of Krogmann salts

It is shown that many of the properties of KCP above any Peierls' transition may be predicted from a non-empirical localized orbital calculation of the electronic structure.     

Ionic structure of solutions of alkali metals and molten salts

Summary Neutron diffraction patterns from K−KCl and Rb−RbBr liquid solutions at various compositions are examined in a ionic-mixture model which neglects screening and aggregation due to the metallic electrons. The main features of the observed diffraction patterns for wave numberk roughly above 1 Å⁻¹ are accounted for by the model. The approach to the metal-rich end of the phase diagram is analysed in detail from different viewpoints in the K−KCl system. Short-range correlations of the potassium ions are described in this region by a metallic radius deduced from properties of the pure liquid metal, but a simple expanded-metal model must be supplemented by the assumption that considerable disorder is introduced in its structure by the halogen ions. Features of short-range ordering in the salt-rich region that are implied by a shoulder on the high-k side of the main peak in the diffraction pattern are also commented upon.

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Riassunto Questo lavoro analizza dati sperimentali di diffrazione neutronica da soluzioni liquide K−KCl e Rb−RbBr a varie composizioni. Mentre la diffusione a piccoli angoli (per numeri d'onda trasferiti inferiori a circa 1 Å⁻¹) è fortemente influenzata da effetti di schermo e di aggregazione associati agli elettroni esterni della componente metallica, l'ordine a corto raggio in questi sistemi è ben riprodotto da un modello che li considera come miscele ioniche. La struttura del sistema K−KCl ad alte concentrazioni della componente metallica è ulteriormente studiata in dettaglio da punti di vista diversi. Si mostra cosí che il sistema in questa regione di composizione può anche essere visto come un metallo espanso di cui gli ioni alogeno riducono fortemente l'ordine a corto raggio. Si discutono infine alcuni aspetti dell'ordine a corto raggio nella regione di alte concentrazioni della componente salina, associati con uno struttura secondaria nella figura di diffrazione.

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Резюме Исследуются результаты дифракции нейтронов на жидких растворах K−KCl и Rb−RbBr при различных составах. Исследование проводится в рамках модели ионной смеси, в которой пренебрегается экранированием и агрегацией, обусловленными металлическими электронами. Эта модель объясняет главные особенности наблюденных картин дифракции для волновых чиселk порядка 1 Å⁻¹. С разных точек зрения анализируется фазовая диаграмма в системе K−KCl. Описываются короткодействующие корреляции для ионов калия в указанной области, используя металлический радиус, выведенный из свойств чистогожидкого металла, но простая металлическая модель должна быть дополнена предположением, что существенный беспорядок вводится в структуру металла ионами галогенов. Интерпретируются особенности короткодействующего упорядочения в области с высоким содержанием соли, которые связаны с выступом у главного пика со стороны большихk на диаграмме дифракции.

     

Spectra of characteristic losses and the electronic structure of sodium nitrite

The complete sets of optical functions for a NaNO₂ crystal are calculated in the energy range of 4 to 24 eV using the integral Kramers-Kronig relations, experimental reflectivity spectra, and theoretical spectra of permittivity. The main distinguishing features and patterns of optical properties are determined as functions of the direction of the light polarization vector. An analysis of the participation of electrons in the formation of optical spectra is presented.     

Spectra and structure of organogermanes: Microwave and Raman spectra of methyltrichlorogermane

The microwave spectrum of methyltrichlorogermane has been investigated in the region 26.5 to 40.0 GHz. The ground state rotational constants, B, were found to be 1602.19, 1601.42, 1601.10, 1600.71, 1600.02, 1537.84, 1537.10, and 1536.36 MHz for the symmetric top molecules CH₃⁷⁰Ge³⁵Cl₃, CH₃⁷²Ge³⁵Cl₃, CH₃⁷³Ge³⁵Cl₃, CH₃⁷⁴Ge³⁵Cl₃, CH₃⁷⁶Ge³⁵Cl₃, CH₃⁷⁰Ge³⁷Cl₃, CH₃⁷²Ge³⁷Cl₃, and CH₃⁷⁴Ge³⁷Cl₃, respectively. For the asymmetric top molecules CH₃⁷²Ge³⁵Cl₂³⁷Cl and CH₃⁷⁴Ge³⁵Cl₂³⁷Cl the ground state rotational constants A, B, and C were found to be 1597.96, 1559.31, 1203 and 1597.17, 1558.59, 1207 MHz, respectively. From the rotational constants the r_s values for the GeCl bond distance of 2.135 ± 0.006 Å and the CGeCl bond angle of 106.0 ± 0.7° were obtained. The centrifugal distortion constant for the CH₃Ge³⁵Cl₃ species was calculated to be 0.35 ± 0.08 kHz. The Raman spectra of methyltrichlorogermane has been recorded in the gas phase and the methyl torsional overtone (Δν = 2) was observed. From the observed frequency shift the barrier to internal rotation has been calculated to be 1.45 kcal/mole.     

Spectra and structure of small ring compounds. Microwave spectrum of cyanocyclobutane

The rotational spectrum of cyanocyclobutane has been investigated in the region 18.0–40.0 GHz. Only A-type transitions were observed. R-branch assignments have been made for the ground state and the first three excited states of the ring puckering mode as well as the first two excited states of the out-of-plane cyano-bending mode. The microwave data are consistent with a bent equilibrium ground state for the ring with the cyano-group in the equatorial position. The dipole moment components were determined to be μ_a = 4.04 ± 0.09 D and μ_c = 0.92 ± 0.03 D with the total dipole moment, μ, having a value of 4.14 ± 0.09 D.     

The antioxidant activity of 4‐hydroxycoumarin derivatives and some sulfured analogs

In this work, the relationship between the structure and the radical scavenging activity of seven hydroxycoumarins and their sulfured analogs was investigated for the first time by density functional theory calculation in the gas phase, benzene, and water. Our investigation includes hydrogen atom transfer, single‐electron transfer–proton transfer, and sequential proton loss electron transfer mechanisms. The results revealed that the bond dissociation enthalpy values of sulfured coumarins were lower than those of hydroxylated analogs. The obtained results were in a good agreement with the experimental results. The hydrogen atom transfer mechanism is dominant in both benzene and vacuum. The sequential proton loss electron transfer mechanism represents the most thermodynamically preferred reaction pathway in water. However, single‐electron transfer–proton transfer mechanism is not the most preferred one in all media. Finally, this work contributes to the understanding of the pharmacological activity of the compounds studied. Copyright © 2015 John Wiley & Sons, Ltd.     

The structure and radiophysical properties of solutions of salts in liquid polar dielectrics

Solutions of metal salts in liquid polar dielectrics are treated as systems of interacting charged particles, that is, cations, anions, and water molecules around cations and anions. The size of solvated ion-clusters is estimated in the approximation of the existence of a self-consistent field in solution volume. The behavior of solutions under the action of external electric field and electromagnetic wave is analyzed. The condition under which a solution of a salt in a liquid polar dielectric reflects electromagnetic waves of a certain frequency is found.     

Electronic structure and superconductivity of κ-(BEDT-TTF)2X salts

We have analyzed the electronic structure and superconducting properties of layered crystals based on BEDT-TTF salts (hereafter denoted as ET), in which intramolecular interaction among electrons is important. For the case of realistic κ-packing of ET-molecules in a plane of ET₂ dimers we have calculated the electron density of states. Using the calculated electronic structure, we have analyzed the symmetry of the anisotropic superconducting pairing. The critical value of the effective attraction between electrons for formation of a bound pair in an empty lattice has been estimated. The relation between the nodes of the d-type order parameter on the anisotropic Fermi surface and superconducting properties of the condensate is discussed in the Bardeen-Cooper-Schrieffer (BCS) model. The results are in agreement with the known band parameters of the normal phase and measurements of the magnetic field penetration depth, heat capacity as a function of temperature in the low-temperature range, and NMR in κ-ET₂X superconducting salts. Zh. éksp. Teor. Fiz. 113, 715–733 (February 1998)     

热释光和光释光发光谱的测量

介绍了自行研制的计算机化热释光和光释光三维光谱测量装置的系统结构及其工作原理.在计算机的控制下,通过精密加热器或激发光源以热激发或光激发的方式使样品发光.从样品发出的光经过光路和光栅分光系统后,形成光谱,被高灵敏度的CCD采集,再将光谱图像模拟信号变为可以直接用计算机进行数据处理的数据信号.波长范围200~800nm,波长分辨率优于2nm,人机界面友好,操作方便.利用热释光和光释光三维光谱测量装置测量了SrSO₄:Eu(0.1%,摩尔分数)和CaSO₄:Eu(0.1%,摩尔分数)的光释光发光谱和热释光发光谱,得到SrSO₄:Eu的光释光发光波长与热释光发光波长均为375nm,而CaSO₄:Eu的光释光发光波长与热释光发光波长均为385nm,说明热释光和光释光具有相同的发光中心,均来自于Eu²⁺的能级跃迁.同时在CaSO₄:Eu的热释光发光谱中还观察到了Eu³⁺的发光.与二维发光曲线相比较,通过对三维热释光和光释光发光谱的研究,可以得到更丰富的信息,这有助于对热释光和光释光发光机制进行更深入的研究.     

Spectra and structure of hexavalent uranium nanoclusters with mixed acido ligands in the coordination sphere

We have obtained and spectroscopically studied mixed acido ligand (Cl, I) uranyl complexes. We used IR absorption spectra to analyze the nature of incorporation of neutral molecules (in particular, dimethylsulfoxide) into the inner coordination sphere of uranium that that do not completely exhaust the coordination capacity of the central uranium atom. We have observed a good correlation between the frequencies of the totally symmetric stretching vibration of the ion in the IR absorption and luminescence. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 76, No. 1, pp. 100–103, January–February, 2009.     

Tb掺杂的硅铝酸盐的拉曼光谱及其荧光光谱研究

采用高温固相法制备不同浓度Tb元素掺杂的硅铝酸盐荧光材料。当烧结温度为1 350 ℃时其荧光强度达到最大值。通过X射线衍射图谱可知体系中基质材料为CaAl₂Si₂O₈,Tb元素以Ca₂Tb₈(SiO₄)₆O₂相存在。通过拉曼光谱分析可知,870 cm-1处振动峰与Ca₂Tb₈(SiO₄)₆O₂中Tb与硅氧四面体的伸缩振动相关;Tb原子与硅氧四面体之间的弯曲振动产生408 cm-1振动峰。随着Tb掺杂量的增加,拉曼振动峰强度,荧光分光光度计测得的荧光光谱以及拉曼光谱仪测得的光致发光光谱的峰强均呈现先增后减的变化规律。该体系中Tb元素与硅氧四面体匹配数量逐渐增加,当Tb掺杂量超过一定极限值时,体系内发生浓度猝灭,导致荧光性能下降。采用325 nm激光作为激发光源,用拉曼光谱仪的光致发光测量模式产生的峰形与传统荧光分光光度计的光谱曲线一致,但其光谱分辨率明显高于传统荧光分光光度计获得的光谱,有助于对细微能级跃迁现象加以区分。     

Spectra and structure of energy levels of Pr3+ in crystals of yttrium and gadolinium oxyorthosilicates

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 62, No. 6, pp. 123–129, November–December, 1995.     

单斜RbInS2、C sInS2的红外光谱及拉曼光谱

我们采用传统的助熔剂合成方法制备单斜ＲｂＩｎＳ２、ＣｓＩｎＳ２晶体并对它们的红外光谱和拉曼光谱进行研究。与ＲｂＩｎＳ２相比,ＣｓＩｎＳ２的红外吸收峰和拉曼吸收峰向长波方向移动。红外光谱和拉曼光谱均表明单斜ＲｂＩｎＳ２、ＣｓＩｎＳ２具有很好的红外透过性能。     

Spectra of alkali metal carbonates in the 4–11-eV region and their electronic structure

Journal of Applied Spectroscopy -