On a simple reaction mechanism for the collision-induced dissociation He + Li2(B1Πu) → He + Li(2 2S) + Li(2 2P)

A simple reaction mechanism is suggested for the dissociation of electronically excited Li₂(B¹Π_u) in collision with rare-gas atoms. Experimental rate constants for dissociation of Li₂ in specific vibrational—rotational levels (ν1J) show an unexpected behaviour as a function of the initial molecular energy and angular momentum. We propose that raction proceeds by a transition to the ¹Π_g state of Li₂. This may dissociate more readily since it is more weakly bound and has a larger equilibrium distance than the ¹Π_u state.     

Ion bombardment induced amorphous layers on single crystal stainless steel-a combined rutherford backscattering and transmission electron microscopy study

Abstract

Decomposition reactions of NaClO₃, KClO₃, and KIO₄ induced by 3 keV Ar⁺ ions and 1254 eV X-rays are investigated by X-ray photoelectron spectroscopy (XPS). The reactions lead to the formation of binary halides with preferential losses of oxygen. The decomposition pattern, monitored at the various stages of reaction, indicates almost direct changeover to the final products with only a few intermediate species formed. Product abundancies are compared for the ion, X-ray, and electron induced reactions and discussed in relation to the various radiation induced reaction mechanisms.     

Wronskian analysis of resonance tunnelling reactions

A Wronskian formalism is developed for resonance tunnelling reactions. It is shown how the S matrix can be written in terms of Wronskians between solutions of the Schrödinger equation representing incoming and outgoing waves. The method is an adaptation of the Jost function approach to elastic two-body scattering. Formal expressions are derived for the imaginary parts of the energy eigenvalues that arise from the application of complex boundary conditions used in a previous semiclassical analysis. When the imaginary parts are small, so that the resonance is sharp, the S matrix can be written in a Breit-Wigner resonance form. The theory unifies and extends the semiclassical analysis of resonance tunnelling reactions given previously.     

用蒙特卡罗方法计算光通过薄层随机分布粒子的散射

本文利用蒙特卡罗方法计算准直光束通过薄层随机分布粒子散射的透射和反射光强,并和输运理论的扩散近似结果做了比较。当散射接近各向同性时两者符合良好。当散射明显地成为各向异性时,蒙特卡罗方法的结果是合理的,而输运理论的扩散近似失效。     

Functional aqueous assemblies of linear-dendron hybrids

Linear-dendron (LD) hybrids are macromolecules comprising a linear polymer or oligomer conjugated at one or both termini with branched macromolecules called dendrons. Since their introduction approximately 2 decades ago, tremendous progress has been made in their synthesis, the study of their self-assembly, and toward their application in a variety of fields. This highlight is focused on aqueous assemblies of LD hybrids where function is imparted by the dendron, linear component, or both. These functions include the encapsulation and release of drug molecules, enhancement of cell uptake and targeting of specific tissues, and the stabilization of enzymes for catalysis. In addition, many stimuli-responsive LD hybrids that undergo changes in response to light, enzymes, pH, temperature, redox potential, or even multiple stimuli have been developed. LD hybrids can also be used to form networks via cross-linking reactions. Described here are the structure–property relationships underlying the functions of these materials, along with their potential applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 148–172     

Palladium-catalyzed carbonylation of arylmethyl halides: efficient synthesis of arylacetic acid and esters

Organopalladium complexes derived from 2-(bromomethyl)benzenemethanol, 2- bromo- and iodobenzenemethanols and 2-iodobenzeneethanol are efficient catalysts for the reaction of carbon monoxide and arylmethyl halides leading to arylacetic acids and esters.     

Spectroscopic diagnosis of the temperature profile of an Al:MgZ-pinch

We consider the question of how the temperature profile of a Z-pinch plasma can be determined and/or constrained by the requirement that its observed K-shell spectrum be replicated. As a case study we employ spatially integrated, time-resolved K-shell data obtained from the implosion of 30-wire Al:Mg alloy arrays on the Saturn driver at Sandia National Laboratories. Given the measured pinch size, its K-shell power and line intensities are compared with the predictions of a collisional-radiative-equilibrium plasma model whose temperature profile is varied in seeking agreement with the data. The Al data rules out a large range of possible temperature profiles, but two quite different temperature distributions can both match the measurements. These are: a uniform temperature, or, one with a sharply dropping temperature near the pinch outer edge. However, the measured ratio of the Mg α resonance lines to those of Al, even though time-integrated, excludes the possibility of a uniform temperature distribution     

Arborescent polypeptides from γ‐benzyl l‐glutamic acid

The synthesis of arborescent polymers with poly(γ‐benzyl L‐glutamate) (PBG) side chains was achieved through successive grafting reactions. The linear PBG building blocks were produced by the ring‐opening polymerization of γ‐benzyl L‐glutamic acid N‐carboxyanhydride initiated with n‐hexylamine. The polymerization conditions were optimized to minimize the loss of amino chain termini in the reaction. Acidolysis of a fraction of the benzyl groups on a linear PBG substrate and coupling with linear PBG using a carbodiimide/hydroxybenzotriazole promoter system yielded a comb‐branched or generation zero (G0) arborescent PBG. Further partial deprotection and grafting cycles led to arborescent PBG of generations G1 to G3. The solvent used in the coupling reaction had a dramatic influence on the yield of graft polymers of generations G1 and above, dimethylsulfoxide being preferable to N,N‐dimethylformamide. This grafting onto scheme yielded well‐defined (M_w/M_n ≤ 1.06), high molecular weight arborescent PBG in a few reaction cycles, with number‐average molecular weights and branching functionalities reaching over 10⁶ and 290, respectively, for the G3 polymer. α‐Helix to coiled conformation transitions were observed from N,N‐dimethylformamide to dimethyl sulfoxide solutions, even for the highly branched polymers. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013 , 51, 5270–5279