Molecular origins of the remarkable chiral sensitivity of second-order nonlinear optics.

Recent observations of remarkably large chiroptical effects in second-harmonic generation (SHG) and sum-frequency generation (SFG) measurements suggest exciting possibilities for the development of new chiral-specific spectroscopies and novel chiral materials for nonlinear optics. Several fundamental studies designed to elucidate the molecular and macromolecular origins of the chiral responses are reviewed to provide a framework for development of this emerging field. In general, the chiral activity in SHG and SFG has the potential to arise from complex interactions between hosts of different competing effects. Fortunately, relatively simple electric dipole-allowed mechanisms routinely dominate the nonlinear optical chiral activities of most practical systemsexpressions can often be generated to link the. This substantial reduction in complexity allows for the development of simple models connecting the macroscopic nonlinear optical response to intuitive molecular and supramolecular properties.     

Ab initio calculations ofp-Cl2C6H4 molecule and its35Cl NQR parameters

Ab initio calculations ofp-dichlorobenzene molecule were carried out using the Hartree-Fock method in the 6–31 G* valence-split basis set. The molecule was also calculated by the MNDO method in the valence sp-basis set for comparison. The populations of the valent p-orbitals of the C and CI atoms were analyzed. The optimized geometry of the molecule as well as its³⁵Cl NQR frequency and the asymmetry parameter of the electric field gradient at the³⁵CI nuclei calculated using the populations of the less diffuse components of the valent p-orbitals of the Cl atoms are in agreement with the corresponding experimental values for the -modification of 1,4-Cl₂C₆H₄.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 2177–2179, September, 1996.     

Tunable UV generation at 283 nm by frequency doubling and sum frequency mixing of two semiconductor lasers for the detection of Pb

High resolution atomic absorption measurements of lead at 283 nm in a vapor cell were performed by frequency doubling an 850 nm laser diode to obtain 425 nm light, followed by sum frequency generation of the harmonic radiation with a second 850 nm laser diode.     

Raman spectra and structural features of ClOF2 + cation in a solution of anhydrous HF

The Raman spectra of ClOF₂ ⁺ cation in solutions of anhydrous HF were studied. In the ClOF₂ ⁺HF₂ ⁻ and ClOF₂ ⁺BF₄ ⁻−HF systems, this cation exists as a pyramidal structure (C _s symmetry), while in the ClOF₂ ⁺AuF₆ ⁻−HF system, it exists as a planar structure (C _2v symmetry). Based on nonempirical calculations by the Hartree-Fock-Roothaan method, an explanation for the dependence of the structure of the ClOF₂ ⁺ cation on the nature of the anion was proposed. For the Cl−O bond vibrations, the correlation functions of vibrational and rotational relaxations were calculated, and the characteristic times of these processes were determined. The main contribution to the formation of the band contours corresponding to the above-mentioned modes is made by the vibrational dephasing. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 3, pp. 432–437, March, 1998.     

Au(II)化合物[Au(CH2)2PH2]2X2 (X＝F, Cl, Br, I)的量子化学理论研究

采用从头计算HF, MP2方法和密度泛函理论, 对Au(II)系列化合物[Au(CH₂)₂PH₂]₂X₂ (X＝F, Cl, Br, I)的几何结构、电子结构和振动频率进行了研究. 研究表明Au的5d和6s电子参与Au—Au以及Au—X之间的成键. Au—Au, Au—X键强烈的电子相关作用使HF方法不适于该体系的研究, BP86和B3LYP两种泛函给出较大的Au—Au和Au—X键长, 而MP2方法和局域的密度泛函方法则给出了合理的结构参数. 局域密度泛函方法计算得到的Au—Au键和 Au—X键振动频率也与实验数据符合较好. 还运用含时密度泛函理论计算了[Au(CH₂)₂PH₂]₂X₂的电子激发能, 对分子在紫外-可见光谱范围内的电子跃迁进行了分析, 考察了卤素配体对激发能的影响, 并结合分子轨道能级的变化对此给予了解释.     

Optimal monotone hysteretic Markov policies in anM/M/1 queueing model with switching costs and finite time horizon

In anM/M/1 queueing model, a decision maker can choosem pairs of arrival- and service rates. He can change his action at any time epoch, a switch of action costs an amount depending on the size of the switch. Besides that there are continuously incurring costs. Over a finite time horizon, there exists an optimal monotone hysteretic Markov policy. This is shown essentially by the technique of time discretization.The work producing this article was done during a half year stay at the University of Leiden, The Netherlands, with Prof. Arie Hordijk. A technical report (a more detailled version of this article) was written there [6]. The opportunity for this stay was given by the University of Bonn, Germany, where the author, at that time, worked as scientific assistant of Prof. M. Schäl.     

压电石英晶体在电解质水溶液中的振荡性能研究(Ⅱ)——频率、频移特性

根据两面电极浸入液体中的压电晶体等效电路模型和Pierce振荡器振荡方程的解,得到晶体在电解质溶液中的振荡频率(F_1)与溶液电导率(x)的关系式:F_1=(1/2π)(1/C_1+1/C_2)(1/X_e)[(R_e~2+X_e~2)x~2+2R_ex+1]。以自行设计的Pierce晶体振荡器。研究了晶体和主振电路参数、输入电压及检测池外壳屏蔽接地对AT切9MHz石英晶体在KCl、Na_2SO_4水溶液中的频率、相对于纯水频移随溶液电导率变化的影响规律,结果与上式相符。     

New FIR laser lines and frequency measurements in CD3OD

Twenty-four new submillimeter laser lines in fully deuterated methyl alcohol (CD₃OD) in the wavelength range from 52 to 328 m have been obtained in a Fabry-Perot FIR resonator by optically pumping the methanol with a cw CO₂ laser. We have made accurate wavelength measurements and have determined the relative polarization of most of the known CD₃OD laser lines. The frequencies of 13 of the strongest lines were also measured.Contribution of the U.S. Government, not subject to copyright.     

Frequencies and wavelengths from a new, efficient FIR lasing gas: CD2F2

We report for the first time wavelength, relative polarization, and frequency measurements for 47 new cw FIR laser lines in the wavelength region from 120 to 1714 m, all obtained by optically pumping CD₂F₂ with a CO₂ laser. Relative output powers were also measured. For comparison, the 189.8 m line pumped by R_I(34) is nearly five times as efficient as the 118.8 m methyl alcohol line.Contribution of the U.S. Government, not subject to copyright.