Resonances of triatomic van der Waals molecules by the complex discrete variable representation

Summary The results of Light and co-workers [J. Chem. Phys. 85:4594 (1986); 86:3065 (1987); 92:2129 (1990)] for the Hamiltonian matrix of a triatomic van der Waals molecule in the discrete variable representation, DVR, is extended to complex-scaled Hamiltonians. As an illustrative numerical example theJ=1 resonances positions and widths of a van der Waals model system were obtained by the calculation of the complex-scaled Hamiltonian matrix in the DVR formalism.Supported in part by the Albert Einstein Research Fund, and the Fund for the Promotion of Research at the Technion     

Theoretical study of the6Σ+,6Π, and4Σ+ van der Waals states of NO

Summary Potential energy curves for the weakly bound⁶⁺,⁶, and⁴⁺ states of NO are presented at various levels of correlation treatment. The binding energies for the van der Waals minima vary from about 30 cm^–1 for the⁶⁺ state to about 20 cm^–1 for the⁴⁺ and⁶ states. We investigate the importance of constraining the wave function to dissociate to a spherically symmetric O atom where the oxygen 2p orbitals are equivalent. For high levels of correlation treatment, we find that these restrictions have little effect on the potential, while greatly increasing the length of the CI expansion.     

Correlation of retention indices with van der Waals’ volumes and surface areas: Alkanes and azo compounds

Summary Van der Waals’ volumes (V _W) and surface areas (S _W) of alkanes, (E)-azoalkanes and structurally similar alkenes (R₁-X=X-R₂, X=N, CH) were calculated by a semiempirical quantum-chemical method (AM1). The calculated data are in reasonable agreement with the experimental values of Bondi and good correlations were found between the calculated data and Kovats’ retention indices (I _R). While theV _Ws of alkanes with the same carbon number are very close to one another, theS _Ws follow the scatter of theI _R values for branched alkanes. The difference in theI _R of (E)-azo compounds and the structurally similar alkenes can be explained by the difference inV _Ws.     

Overview of reduced dimensionality quantum approaches to reactive scattering

 In this overview I discuss recent advances as well as outstanding issues in reduced dimensionality quantum approaches to reactive scattering. “Reduced dimensionality” in the present context signifies treating a subset of all degrees of freedom (the most strongly coupled ones) by rigorous quantum methods and treating the remaining (weakly coupled) degrees of freedom by a variety of approximate methods, ranging from simple, so-called energy shifts to more elaborate adiabatic treatments. The most widely used example of this approach is termed “J-shifting”, and this overview will concentrate on this method and discuss its application and generalization to both “direct” and “complex” reactions, exemplified by O(³P) + HCl and O(¹D) + HCl, respectively. In addition, for O(³P) + HCl, resonances in the tunneling region, due to van der Waals wells, are discussed and their challenge to reduced dimensionality methods is stressed. Another new aspect of the reduced dimensionality treatment of polyatomic reactions is the need to describe anharmonicity in a consistent fashion. This is exemplified by the H + CH₄ reaction. Received: 3 February 2002 / Accepted: 8 April 2002 / Published online: 19 August 2002     

Determination of van der Waals forces in monolayer films of lipids & biopolymers. Equation of state for two-dimensional films

Amphiphile molecules are characterized by the dual property arising from the interactions between the apolar [alkyl] and the polar part and the surrounding solvent, i.e., water. In assemblies which amphiphiles form in diverse systems, e.g., micelles, soap bubbles, monolayers or bilayers at interfaces, the attractive forces are attributed to the van der Waals forces. It is not easy to estimate the magnitude of van der Waals forces in some of these systems by any direct method.The magnitude of van der Waals forces in spread monolayers of lipids and biopolymers has been reported to be estimated from experimental data. The magnitude of these forces has been estimated by using an equation of state of a very general form, as delineated herein. In the current literature no such attempt has been reported in the analyses of these monolayers spread on aqueous surfaces. These analyses suggest that the predominant surface forces arise from van der Waals interactions, if the magnitude of electrostatic charge repulsions is weak. The equation-of-state as derived indicates that it is useful in providing information about the molecular interaction in monolayers, for both lipids and biopolymers.