Molecular Reaction Dynamics: Frontmatter

Solvent Density Inhomogeneities in Supercritical Fluids.

Many aspects of the collision dynamics of vibrational energy transfer are presented. Special emphasis is placed on three broad areas within this field:  (1) vibrational energy transfer in large molecules (>10 modes) at low excitation, (2) vibrational energy transfer in large molecules at high vibrational excitation, and (3) vibrational energy transfer of highly excited small molecules. Advances in laser methods have revolutionized experimental investigations of all of these areas. Recent results are presented, and directions for the future are discussed.

Vibrational energy transfer

The use of energy transfer data and models in describing nonequilibrium polyatomic reaction systems is discussed with particular emphasis on the information needed for modeling vibrational energy transfer. In the discussion, it is pointed out that key areas of energy transfer knowledge are still lacking and the available experimental data are limited in scope and are of uneven quality. Despite these limitations, it is still possible to carry out meaningful simulations of chemical systems in which vibrational energy transfer is important. The vibrational energy master equation, which is the basis for modeling, and various experiments and calculations that provide the basis for practical energy transfer models and parametrizations are described. Two examples of gas phase reaction systems are presented in which vibrational energy transfer is important. The decomposition of norbornene shows how energy transfer parameters can be obtained from measurements of shock-induced chemical reactions, but even the best ...

Vibrational Energy Transfer Modeling of Nonequilibrium Polyatomic Reaction Systems

Recent experimental and theoretical advances in the understanding of high-pressure, high-temperature chemical kinetics are used to extend the nonequilibrium Zeldovich−von Neumann−Doring (NEZND) theory of self-sustaining detonation in liquid and solid explosives. The attainment of vibrational equilibrium behind the leading shock front by multiphonon up-pumping and internal vibrational energy redistribution establishes a high-temperature, high-density transition state or series of transition states through which the chemical decomposition proceeds. The reaction rate constants for the initial unimolecular decomposition steps are accurately calculated using high-temperature, high-density transition-state theory. These early reactions are endothermic or weakly exothermic, but they channel most of the available energy into excited vibrational states of intermediate product species. The intermediate products transfer some of their vibrational energy back into the transition states, accelerating the overall react...

Multiple Roles of Highly Vibrationally Excited Molecules in the Reaction Zones of Detonation Waves

The simplest model for chemical reactions that proceed by unimolecular decomposition in the gas phase is the Lindemann mechanism, in which a substrate S is excited by collisions to a level S* with energy sufficient to cause bond breaking or molecular rearrangement ( 1-3). For large molecules, the time scale for decomposition of S* is sufficiently long that further collisions with the bath molecules can cause deactivation of the excited substrate, thus quenching the reaction process. The overall mech­ anism can be summarized by the following equations:

R. E. Weston

Papers

Relaxation of Molecules with Chemically Significant Amounts of Vibrational Energy: The Dawn of the Quantum State Resolved Era