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.




State to State Collision Induced Dissociation and Gas/Surface Interactions


Book Description

The main thrust of our contract was directed towards the study of gas surface interactions and the complementary collisionless photodissociation processes. Our initial experiments were concerned with NO scattering from an insulating MgO(100) single crystal surfaces, and the preliminary results have been published in Chem. Phys. Lett. We are now conducting experiments in which molecules with high kinetic energy are dissociated and/or ionized upon impact on surfaces. Our preliminary results, which are first of their kind since they involve state-resolved detection of the dissociation products, have been accepted as a Communication in the Journal of Chemical Physics. In parallel with these new experiments, we have continued our studies of the photophysics and photodissociation dynamics of molecules which are suitable candidates for the beam/surface and beam/beam experiments. These include detailed studies of the photodissociation dynamics of such molecules as nitrosyl cyanide, nitrosyl chloride, t-BuNO and n- and iso-nitrosopropane. Gas surface collisions, Scattering, Nitrogen oxide, Photodissociation dynamics, Dissociative scattering. (mjm).







Atom - Molecule Collision Theory


Book Description

The broad field of molecular collisions is one of considerable current interest, one in which there is a great deal of research activity, both experi mental and theoretical. This is probably because elastic, inelastic, and reactive intermolecular collisions are of central importance in many of the fundamental processes of chemistry and physics. One small area of this field, namely atom-molecule collisions, is now beginning to be "understood" from first principles. Although the more general subject of the collisions of polyatomic molecules is of great im portance and intrinsic interest, it is still too complex from the viewpoint of theoretical understanding. However, for atoms and simple molecules the essential theory is well developed, and computational methods are sufficiently advanced that calculations can now be favorably compared with experimental results. This "coming together" of the subject (and, incidentally, of physicists and chemists !), though still in an early stage, signals that the time is ripe for an appraisal and review of the theoretical basis of atom-molecule collisions. It is especially important for the experimentalist in the field to have a working knowledge of the theory and computational methods required to describe the experimentally observable behavior of the system. By now many of the alternative theoretical approaches and computational procedures have been tested and intercompared. More-or-Iess optimal methods for dealing with each aspect are emerging. In many cases working equations, even schematic algorithms, have been developed, with assumptions and caveats delineated.