位相共轭镜耦合到染料激光器中的频移现象

本文建议了一个测量位相共轭镜耦合到染料激光器后,当波长自扫描时,BaTiO_3晶体内的运动光栅的多普勒频移的方法,实验结果表明,多普勒频移Δf<0.2Hz.进一步的分析显示,多普勒频移不能解释朝长波方向扫描的波长自扫描现象.     

Resonance Raman investigation of the short-time dynamics of the ultraviolet photodissociation of bromoform

We report ultraviolet resonance Raman spectra of bromoform (CHBr₃) in cyclohexane solution. The resonance Raman spectra show significant intensity in the overtones of the nominal Br-C-Br symmetric bend (v ₆), the nominal H-C-Br asymmetric bend (v3), the nominal Br-C-Br symmetric stretch (v ₂) and the nominal Br-C-Br asymmetric stretch (v ₅) vibrational modes suggesting that the short-time photodissociation dynamics have noticeable multidimensional character. The lack of strong combination bands between several of the Franck-Condon active modes suggests that more than one electronic transition contribute to the resonance Raman spectra. We briefly discuss the ultraviolet short-time photodissociation dynamics of bromoform and the potential implications for the secondary photodissociation reactions of the initially formed CHBr₂ radical.     

The direct product structure of atomic orbital manifolds: extension to non-Euclidean permutation groups

Atomic orbital manifolds are described as Γ × Γ direct products of degenerate irreducible representations (irreps) of odd dimension in suitable groups, which may be either the polyhedral symmetry point groups (T, O, I) or larger simple non-Euclidean permutation groups containing the polyhedral symmetry point groups as subgroups. Such larger non-Euclidean groups include the simple pollakispolyhedral groups ⁷ O [≈L ₂(7)] and ¹¹ I [≈L ₂(11)] of orders 168 and 660, respectively, and the simple alternating groups A ₆ and A ₇ of orders 360 and 2520, respectively. Thus the 9-dimensional (9D) direct product T × T of a 3D irrep of the polyhedral or larger point groups leads to the nine-orbital sp³d⁵ manifold. In icosahedral symmetry I this 9D direct product splits into separate irreps for the s, p and d orbitals, whereas in the larger non-Euclidean ⁷ O group this direct product splits only into a 6D irrep for the gerade orbitals (s + d) and a 3D irrep for the ungerade p orbitals. A similar method can be used to study the 25-orbital sp³d⁵f⁷g⁹ manifold as H × H direct products in the icosahedral group I and the two larger simple non-Euclidean groups A ₆ and ¹¹ I, in which I is a subgroup of index 6 and 11, respectively. The mathematics implicit in these direct products appears to have some connections with a few areas of chemical physics including icosahedral quasicrystals and unusual degeneracies in the Coulomb energies of terms in transition metal atomic spectra.     

第五、六族元素的有机化合物在有机合成中应用的研究——Ⅸ.氰代亚甲基三苯基胂与酮的反应

Trippett^[1]曾报道氰代亚甲基三苯基膦不能与酮反应.作者之一及其同工作者曾报道甲氧羰基亚甲基三苯基胂与多种醛、酮反应,其反应性能比相应的膦试剂活泼.本文报道氰代亚甲基三苯基胂(2)的制备,以及它与一系列酮包括α,β-不饱和酮的反应(产物和产率列于表1),表明2的反应性能也较相应的膦试剂活泼.     

Asymptotic analysis of the growth of cake layers in filters

The problem of fluid flow in a two-dimensional pleated filteris considered. Of particular interest is the change in the flowdue to cake build-up on the surface of the filter material.The flow is taken to be Darcy flow in the cake and the filtermaterial, with Stokes' flow outside the cake. The particlesin the flow are taken to be transported with the flow and tostick to the cake without slippage or resuspension, and thecake is taken to be incompressible. The flow is considered invarious geometries, particularly long thin filters and corners.The main parameter in the problem is the ratio of the filter-materialresistance to the cake resistance, and limiting cases are considered.Travelling waves of cake build-up are found for arbitrary time-dependentvariations in the inflow conditions. The time taken for thefilter to become clogged by the cake is also considered.     

A reaction-diffusion model for autocatalytic polymerization: II. The initial value problem

An initial-boundary value problem arising from a simple modelfor radical chain polymerization is discussed in detail. Generalproperties of the solution are derived first and it is shownthat a moving interface develops. This separates a region wherethe polymer is sufficiently concentrated for it to be immobilefrom one where it is still free to diffuse. An asymptotic analysisis performed in this latter region, where it is shown that apermanent-form travelling wave (treated in Part I) developsin the long time structure and that this wave travels with itsminimum possible speed. Numerical results for the full initial-boundaryvalue problem are presented which confirm the asymptotic theoryand give results in regions not accessible to this analysis.