Rotationally resolved photoelectron angular distributions for H+2(ν′ = 0) at λ = 584 and 736 Å

The photoelectron asymmetry parameter for H⁺₂(ν′ = 0) was measured for the S rotational branch at λ = 584 and 736 Å using supersonic beam of n-H₂. Comparison with the theoretical β values of Itikawa demonstrates the importance of coupling between the p and f photoelectron waves at higher photon energy.     

Vibrational properties of glasses: Intermediate range order

This paper discusses a break-through in the calculation of the vibrational properties of disordered solids. Our approach is a refinement of the Bethe Lattice method incorporating aspects of intermediate range order.     

Conversion-electron and transmission mössbauer study of natural microcrystalline goethite

Mössbauer spectra of naturally occurring goethite were measured at various temperatures using both conversion-electron and transmission⁵⁷Fe Mössbauer spectroscopy. Thin slices of rock and powdered samples were examined. Large differences apparent in the spectra are interpreted in terms of distributions of fine crystallites and different methods of sample preparation. It is shown that sometimes the usual powder preparation technique causes a loss of information which could lead to an oversimplified geological classification.     

Transport in ionic liquids under pressure. II. Concentrated calcium nitrate-water and magnesium chloride-water solutions

The interpretations of transport properties of concentrated aqueous solutions by the physics of glass-forming liquids approach recently applied to normal pressure measurements is extended by analysis of the pressure dependence of the electrical conductance of Ca(NO₃)₂ and MgCl₂ solutions. The conductance of these solutions has been determined to 3 kbar over the temperature range 20–100°C for compositions 9–20 mole% Ca(NO₃)₂ (5.6–13.9 m) and 80–200°C for MgCl₂ solutions of composition 12.4 and 14.2% MgCl₂. Using high-pressure-data determination of the glass-transition temperature to eliminate one adjustable parameter, it is found that the pressure dependence of the conductance of these solutions can be adequately described by ascribing all the pressure dependences to a single parameter, the ideal glass temperature T_o(P) of the Vogel-Tammann-Fulcher (VTF) equation known to describe temperature dependences of transport in viscous liquids. The results are discussed in terms of the Adam-Gibbs entropy theory and the Angell-Rao bond lattice model. The latter relates the pressure dependence of conductance to the volume change involved in configurational excitations of the liquid quasi-lattice, for which a mean volume increment of 1.6 cm³/mole is obtained.     

ATP-stimulated transmitter release and cyclic AMP synthesis in isolated chromaffin granules.

ATP stimulates chromaffin granules from the bovine adrenal medulla to release epinephrine and specific soluble proteins. ATP analogs substituted in the beta-gamma position with either nitrogen or carbon were also found to be effective at inducing release from isolated chromaffin granules. However, an ATP analog substituted at the alpha-beta position with carbon was strongly inhibitory. Cyclic AMP was also found to be synthesized by isolated chromaffin granules under release conditions. ATP analogs were effective as substrates for adenylate cyclase in the same order as their efficiency for inducing release from vesicles. Hydrolysis at the beta-gamma linkage of ATP therefore is probably not necessary for release; however, hydrolysis at the alpha-beta position may be important in the release process. Cyclic AMP may be produced and play a regulatory role in this event.     

Pulsed lasers in electronic speckle pattern interferometry

This paper describes the incorporation of a pulsed ruby laser into an electronic speckle pattern interferometer. A technique is described for observing vibrational and transient events with a double pulsed laser and some typical results are given. Results of the application of the interferometer to non-destructive testing are included.     

Determination of stability constants of a copper/citric acid complex by ion-exchange chromatography and atomic absorption spectrometry

The method is based on separation of free copper ion from the complex by ion-exchange chromatography and determination of the free copper ions by atomic absorption spectrometry. Parameters that influence the separation and determination of the free metal are evaluated. Calculation of the conditional stability constant and the number of binding sites per citric acid (L) molecule was based on a Scatchard plot. The conditional stability constants found for the CuL^2? complex were pK = 5.04 at pH 7.0 and pK = 4.76 at pH 6.2 and ionic strength 0.10 M. The number of binding sites per molecule was unity.     

A kinetic model for pyrolysis of CF2HCl

Thermal decomposition of CF₂HCl has been modeled using 2,269 thermally activated reactions and 63 chemically activated processes. Thermochemical properties for the species involved are calculated using statistical mechanics and group contribution theory, and reaction rate constants are determined using transition state theory. The theoretical predictions, obtained without fitting any parameter values, afree closely with available experimental data. Also, the reactions that control the distribution of reaction products are identified, and this, in turn, permits simplification of the reaction set. Sensitivity studies show that uncertainties in the calculations do not alter the predicted trends in behavior or the main reaction pathways. © 1995 John Wiley & Sons, Inc.     

An evaluation of the spectral noise distribution in analytical flames

The spectral distribution of noises (total, shot and flicker) in a variety of flames has been measured using a computer-controlled spectrometer system. Emission spectra and fluorescence spectra (excited by an Eimac xenon arc lamp) are presented for air/acetylene, nitrous oxide/acetylene, nitrous oxide/propane, air/hydrogen, and an iso-octane liquid fuel flame. Conclusions concerning the predominant type of noise and its cause in each flame are discussed as well as the implications for the analytical flame spectroscopist.