Dynamics of Collisional Dissociation: I2 in Ar and Xe


Book Description

The dynamics of collision induced dissociation of I2 in Xe and Ar was investigated between 300 and 3500 K by means of 3-D classical trajectory technique. For this purpose stratified and importance sampling techniques were adopted to trajectory studies of dissociation. The dissociation cross-sections for I2-Ar reaction were computed between 1000 and 3500 K as a function of impact parameter and I2 internal energy. It was found that for this reaction the overwhelming contribution to the overall rate coefficient comes from trajectories which involve I2 molecules with initial internal energy + or - 1 kT within the dissociation limit. For I2-Xe reaction at 300 K the 'collisional release' mechanism contributes to dissociation and the 'reactive' I2 have a broader energy range between -4 kT to + 1 kT within the dissociation limit. Highly excited metastable I2 dissociate predominantly by de-excitation collisions in which the total as well as the rotational energy of the reactant molecule is decreased.










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Book Description







Dynamics of Polyatomic Van der Waals Complexes


Book Description

This publication is the Proceedings of the NATO Advanced Research Workshop (ARW) on the Dynamics of Polyatomic Van der Waals Molecules held at the Chateau de Bonas, Castera-Verduzan, France, from August 21 through August 26, 1989. Van der Waals complexes provide important model problems for understanding energy transfer and dissipation. These processes can be described in great detail for Van der Waals complexes, and the insight gained from such studies can be applied to more complicated chemical problems that are not amenable to detailed study. The workshop concentrated on the current questions and future prospects for extend ing our highly detailed knowledge of triatomic Van der Waals molecule dynamics to polyatomic molecules and clusters (one molecule surrounded by several, or up to sev eral tens of, atoms). Both experimental and theoretical studies were discussed, with particular emphasis on the dynamical behavior of dissociation as observed in the dis tributions of quantum states of the dissociation product molecules. The discussion of theoretical approaches covered the range from complete ab initio studies with a rig orous quantum mechanical treatment of the dynamics to the empirical determination of potential energy surfaces and a classical mechanical treatment of the dynamics. Time independent, time dependent and statistical approaches were considered. The workshop brought together experts from different fields which, we hope, benefited from their mutual interaction around the central theme of the Dynamics of Van der Waals complexes.













Physics and Chemistry of Small Clusters


Book Description

Recent advances in experimental techniques now enable researchers to produce in a laboratory clusters of atoms of desired composition from any of the elements of the periodic table. This has created a new area of research into novel materials since clusters cannot be regarded either as a "large" molecule or as a fragment of the bulk. Both experimental and theoretical studies are revealing unusual properties that are not ob served in solid state environments. The structures of micro-clusters are found to be significantly distorted from the most symmetric arrangement, some even exhibiting pentagonal symmetry commonly found in icosahedric structures. The unusual stability of certain clusters, now described as "magic number species", shows striking similarities with the nuclear shell structure. The relative stabilities of clusters depend not only on the composition of the clusters but also on their charged states. The studies on spontaneous fragmentation of mUltiply charged clusters, commonly referred to as Coulomb explosion, illustrate the role of electronic bonding mechanisms on stability of clusters. The effect of foreign atoms on geometry and stability of clusters and the interaction of gas atoms with clusters are showing promise for an indepth understanding of chemisorption and catalysis. The magnetic and optical properties are dependent not only on cluster size but also on its geometry. These findings have the potential for aiding industry in the area of micro-electronics and catalysis.