Computer Algebra Systems in Physical Chemistry

It is argued that a computer algebra system should replace the FORTRAN-like languages in the undergraduate and graduate programs in chemistry. To support the argument example applications from physical chemistry are used to display the symbolic, numerical, and graphical capabilities of one such system. The code for the more complex applications is given in an appendix.     

Products of locally compact groups with zero and their actions

In this paper we briefly describe the structure of a product of locally compact groups with zero, and then investigate actions of such semigroups on Hausdorff spaces. Communicated by A. D. Wallace     

The effect of the crystal structure of the field emitter on field ion energy distributions

The field ionization probability of an atom as a function of distance from the field emitter is discussed in terms of the atomic arrangement and the electron scattering properties of the ion cores of the emitter in the immediate neighborhood of the atom to be ionized, and the electron transmission properties of the potential barrier between the emitter and that atom. This approach to field ionization calculations is somewhat similar to field ionization calculations based on low energy electron diffraction (LEED) procedure in that it takes into account electron scattering from the first few atomic layers of the emitter. It differs from LEED type calculations, because it considers the highly localized nature of the ionization near a surface atom. This localization makes the ionization probability relatively insensitive to the two-dimensional periodicity of the emitter surface. A one-dimensional calculation, in which only the potential barrier and three ion core scatterers in line with the field are considered, shows secondary structure in the predicted field ion energy distributions near the critical energy deficit, as well as the well known, primary field induced resonance peaks. The surface orientation dependence of these distributions arises naturally from this model because the secondary structure depends strongly upon the crystal parameter along a line parallel to the field. This one-dimensional calculation can be no more than an approximation to a complete calculation. It is interesting, however, that such a simple physical model, in which scattering from the image potential and only two or three ion cores is considered, rather than scattering from a complete crystal, can give prodicted field ion onergy distributions which are similar to those experimentally observed.     

Shock tube measurements of branched alkane ignition times and OH concentration time histories

Ignition times and hydroxyl (OH) radical concentration time histories were measured behind reflected shock waves during the oxidation of three branched alkanes: iso‐butane (2‐methylpropane), iso‐pentane (2‐methylbutane), and iso‐octane (2,2,4‐trimethylpentane). Initial reflected shock conditions ranged from 1177 to 2009 K and 1.10 to 12.58 atm with dilute fuel/O₂/Ar mixtures varying in fuel concentration from 100 ppm to 1.25% and in equivalence ratio from 0.25 to 2. Ignition times were measured using endwall CH emission and OH concentrations were measured using narrow‐linewidth ring‐dye laser absorption of the R₁(5) line of the OH A‐X (0,0) band at 306.7 nm. The ignition times and OH concentration time histories were compared to modeled predictions of seven branched alkane oxidation mechanisms currently available in the literature and the implications of these comparisons are discussed. These data provide a unique database for the validation of detailed hydrocarbon oxidation mechanisms of propulsion related fuels. © 2003 Wiley Periodicals, Inc. Int J Chem Kinet 36: 67–78 2004     

Packed column supercritical fluid chromatography with FID: Investigation of products from copper-catalyzed conjugate additions of trimethylaluminium to α, β-unsaturated aldehydes

Summary A method for the process control of conjugate addition reactions by packed column SFC has been developed. The lack of chromophores in some product components makes the use of FID obligatory. Polar compounds were eluted with FID-compatible, aqueous formic acid as mobile phase modifier at 100°C.     

Reaction kinetics of NH in the shock tube pyrolysis of HNCO

The high temperature kinetics of NH in the pyrolysis of isocyanic acid (HNCO) have been studied in reflected shock wave experiments. Time histories of the NH(X³Σ^?) radical were measured using a cw, narrow-linewidth laser absorption diagnostic at 336 nm. The second-order rate coefficients of the reactions: (1) were determined to be: cm³?mol^?1?s^?1, where f and F define the lower and upper uncertainty limits, respectively. The data for k_1a are somewhat better fit by:      

Computing an interior point for inequalities using linear optimization

The problem of finding the middle of a feasible region defined by solutions to a set of linear inequalities is considered. The solution of this problem is formulated as a primal-dual pair of linear optimization problems whose solutions can be obtained using linear programming computations.