Vibrational relaxation of KrF* and XeCl* by rare gases

A steady-state, chemiluminescence technique has been used to measure effective rate constants for vibrational relaxation as a function of vibrational level for KrF^* in collisions with He, Ne, and Ar and XeCl^* with Ar. The effective rate constants reported include contributions to relaxation due to intersystem crossing between theB andC states, in addition to direct relaxation within theB state. The relevance of these results to the understanding of previous measurements in KrF and XeCl lasers is discussed.     

Novel glass-forming liquid crystals. II. Systems containing 1-phenyl-2-(6-cyanonaphth-2-yl)ethyne as a high optical birefringence moiety

A new series of glass-forming molecular materials have been synthesized that incorporate 1-phenyl-2-(6-cyanonaphth-2-yl)ethyne as the high optical birefringence nematogenic moiety and a diphenylacetylenic group as part of the chiral moiety containing (S)-(-)-1-phenylethanol. To facilitate the preparation of chiral nematic systems, the key intermediate, i.e. 1,3,5-cyclohex-anetricarboxylic anhydride chloride, was synthesized and characterized. The thermotropic and optical properties of all products and the blends prepared therefrom were characterized by polarizing optical microscopy, differential scanning calorimetry, and UV-VIS-NIR spectrophotometry. It was found that all the resultant molecular materials readily form glasses with a T_g of around 60°C while showing no residual crystallinity below T_g or tendency toward crystallization by heating above T_g. Furthermore, binary blends showed a decreasing degree of miscibility at an increasing extent of structural dissimilarity with the all-chiral/all-nematic systems exhibiting significant phase separation at a chiral mole fraction of 0.16.     

A comparative thermodynamic analysis of InP and GaAs deposition

A PCl₃ transport system for epitaxial InP deposition has been considered from an equilibrium point of view and compared with a similar arsenic trichloride process for GaAs deposition. Thermochemical values for all species pertinent to these two systems were compiled and employed in conjunction with an iterative Gibbs energy minimization program to compute the gas phase equilibrium concentrations and the maximum extent of deposition. The results are presented as functions of three independent variables: the source and deposition temperatures and the initial concentration of Group III trichloride. The degree of gas phase supersaturation is presented as a function of the temperature differential between the source and deposition regions.     

On determining the dimension of chaotic flows

We describe a method for determining the approximate fractal dimension of an attractor. Our technique fits linear subspaces of appropriate dimension to sets of points on the attractor. The deviation between points on the attractor and this local linear subspace is analyzed through standard multilinear regression techniques. We show how the local dimension of attractors underlying physical phenomena can be measured even when only a single time-varying quantity is available for analysis. These methods are applied to several dissipative dynamical systems.     

Fused s-Triazino heterocycles. VI. 1,9,9b-Triazaphenalenes

Derivatives of 1,9,b-triazaphenalene have been prepared by reacting alkyl-N-cyanoimidates with 2,6-bis(cyanomethyl)pyridine.     

Conformational polymorphism in a chiral spiro-cis-ansa-bridged cyclo­triphosphazene derivative

The reaction of spermidine with 2,2,4,4-tetra­chloro-6,6-di­phenyl­cyclo­triphosphazene produces a mixture of products of which one of the fractions is a spiro-cis-ansa deriv­ative, namely 12-chloro-14,14-di­phenyl-2,6,11,13,15,16-hexa­aza-1,12-di­phosphatri­cyclo­[10.3.1.0^1,6]­hexadeca-12,14-diene, C₁₉H₂₆Cl­N₆P₃. Recrystallization of this fraction from different solvents results in the formation of two different crystalline forms. The rod morphology formed in di­chloro­methane–n-hexane (1:1) produces a triclinic structure with three mol­ecules in the asymmetric unit. These three mol­ecules adopt different conformations as a result of two NH groups flipping in an ansa-bridged ring system. The plate morphology crystals, grown in di­chloro­methane–n-hexane–ethyl acetate (1:1:1), produce a C-centred monoclinic structure that adopts a conformation that is essentially the same as one of the forms in the triclinic structure.