Studies of chemical reactivity in the condensed phase. I. The dynamics of iodine photodissociation and recombination on a picosecond time scale and comparison to theories for chemical reactions in solution

1986 ◽  
Vol 84 (2) ◽  
pp. 788-806 ◽  
Author(s):  
A. L. Harris ◽  
M. Berg ◽  
C. B. Harris
Keyword(s):  
Phase I ◽  
Chemical Reactions ◽  
Condensed Phase ◽  
Time Scale ◽  
Chemical Reactivity ◽  
Picosecond Time Scale

Epitaxy and Chemical Reactions During Thin Film Formation from Low Energy Ions New Kinetic Pathways, New Phases and New Properties

1991 ◽  
Vol 236 ◽  
Author(s):  
Nicole Herbots ◽  
O.C. Hellman ◽  
O. Vancauwenberghe
Keyword(s):  
Thin Film ◽  
Chemical Reactions ◽  
Degrees Of Freedom ◽  
Film Growth ◽  
Film Formation ◽  
Chemical Reactivity ◽  
Ion Beam ◽  
Low Energy ◽  
Low Energy Ions ◽  
Beam Deposition

AbstractThree important effects of low energy direct Ion Beam Deposition (IBD) are the athermal incorporation of material into a substrate, the enhancement of atomic mobility in the subsurface, and the modification of growth kinetics it creates. All lead to a significant lowering of the temperature necessary to induce epitaxial growth and chemical reactions. The fundamental understanding and new applications of low temperature kinetics induced by low energy ions in thin film growth and surface processing of semiconductors are reviewed. It is shown that the mechanism of IBD growth can be understood and computed quantitatively using a simple model including ion induced defect generation and sputtering, elastic recombination, thermal diffusion, chemical reactivity, and desorption The energy, temperature and dose dependence of growth rate, epitaxy, and chemical reaction during IBD is found to be controlled by the net recombination rate of interstitials at the surface in the case of epitaxy and unreacted films, and by the balance between ion beam decomposition and phase formation induced by ion beam generated defects in the case of compound thin films. Recent systematic experiments on the formation of oxides and nitrides on Si, Ge/Si(100), heteroepitaxial SixGe1−x/Si(100) and GaAs(100) illustrate applications of this mechanism using IBD in the form of Ion Beam Nitridation (IBN), Ion Beam Oxidation (IBO) and Combined Ion and Molecular beam Deposition (CIMD). It is shown that these techniques enable (1) the formation of conventional phases in conditions never used before, (2) the control and creation of properties via new degrees of freedom such as ion energy and lowered substrate temperatures, and (3) the formation of new metastable heterostructures that cannot be grown by pure thermal means.

Correlation of hot-phonon and hot-carrier kinetics in Ge on a picosecond time scale

1991 ◽  
Vol 43 (8) ◽  
pp. 6682-6690 ◽  
Author(s):  
Andreas Othonos ◽  
H. M. van Driel ◽  
Jeff F. Young ◽  
Paul J. Kelly
Keyword(s):  
Time Scale ◽  
Hot Carrier ◽  
Picosecond Time Scale

scholarly journals A local view of the laser induced magnetic domain dynamics in CoPd stripe domains at the picosecond time scale

2020 ◽  
Vol 32 (46) ◽  
pp. 465801
Author(s):  
V López-Flores ◽  
M-A Mawass ◽  
J Herrero-Albillos ◽  
A A Uenal ◽  
S Valencia ◽  
...  
Keyword(s):  
Time Scale ◽  
Magnetic Domain ◽  
Local View ◽  
Picosecond Time Scale ◽  
Domain Dynamics

Chemical Reactions In Condensed Phases

2006 ◽  
Author(s):  
Abraham Nitzan
Keyword(s):  
Chemical Reactions ◽  
Condensed Phase ◽  
Chemical Change ◽  
Classical Mechanics ◽  
Chemical System ◽  
Condensed Phases ◽  
Molecular Configuration ◽  
Middle Stage ◽  
Condensed Phase Reactions ◽  
Energy Surfaces

Understanding chemical reactions in condensed phases is essentially the understanding of solvent effects on chemical processes. Such effects appear in many ways. Some stem from equilibrium properties, for example, solvation energies and free energy surfaces. Others result from dynamical phenomena: solvent effect on diffusion of reactants toward each other, dynamical cage effects, solvent-induced energy accumulation and relaxation, and suppression of dynamical change in molecular configuration by solvent induced friction. In attempting to sort out these different effects it is useful to note that a chemical reaction proceeds by two principal dynamical processes that appear in three stages. In the first and last stages the reactants are brought together and products are separated from each other. In the middle stage the assembled chemical system undergoes the structural/chemical change. In a condensed phase the first and last stages involve diffusion, sometimes (e.g. when the species involved are charged) in a force field. The middle stage often involves the crossing of a potential barrier. When the barrier is high the latter process is rate-determining. In unimolecular reactions the species that undergoes the chemical change is already assembled and only the barrier crossing process is relevant. On the other hand, in bi-molecular reactions with low barrier (of order kBT or less), the rate may be dominated by the diffusion process that brings the reactants together. It is therefore meaningful to discuss these two ingredients of chemical rate processes separately. Most of the discussion in this chapter is based on a classical mechanics description of chemical reactions. Such classical pictures are relevant to many condensed phase reactions at and above room temperature and, as we shall see, can be generalized when needed to take into account the discrete nature of molecular states. In some situations quantum effects dominate and need to be treated explicitly. This is the case, for example, when tunneling is a rate determining process. Another important class is nonadiabatic reactions, where the rate determining process is hopping (curve crossing) between two electronic states. Such reactions are discussed in Chapter 16.

Achieving tunable chemical reactivity through photo-initiation of energetic materials at metal oxide surfaces

2020 ◽  
Vol 22 (43) ◽  
pp. 25284-25296
Author(s):  
Maija M. Kuklja ◽  
Roman Tsyshevsky ◽  
Anton S. Zverev ◽  
Anatoly Mitrofanov ◽  
Natalya Ilyakova ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Chemical Reactions ◽  
Energetic Materials ◽  
Chemical Reactivity ◽  
Energetic Material ◽  
Oxide Surfaces ◽  
Oxide Interfaces ◽  
Metal Oxide Surfaces

Photo-stimulated chemical reactions in energetic materials can be highly controlled by selectively designing energetic material – metal oxide interfaces with tailored properties.

Modelling of chemical reactions in hypersonic rarefied flow with the direct simulation Monte Carlo method

1996 ◽  
Vol 312 ◽  
pp. 149-172 ◽  
Author(s):  
Michael A. Gallis ◽  
John K. Harvey
Keyword(s):  
Monte Carlo ◽  
Chemical Reactions ◽  
Energy Exchange ◽  
Chemical Reactivity ◽  
Direct Simulation Monte Carlo ◽  
Direct Simulation ◽  
Rarefied Flow ◽  
Rarefied Flows ◽  
Exchange Processes ◽  
Simulation Monte Carlo

In this paper the phenomenon of chemical reactivity in hypersonic rarefied flows is examined. A new model is developed to describe the reactions and post-collision energy exchange processes that take place under conditions of molecular non-equilibrium. The new scheme, which is applied within the framework of the direct simulation Monte Carlo (DSMC) method, draws its inspiration from the principles of maximum entropy which were developed by Levine & Bernstein. Sample hypersonic flow fields, typical of spacecraft re-entry conditions in which reactions play an important role, are presented and compared with results from experiments and other DSMC calculations. The latter use traditional methods for the modelling of chemical reactions and energy exchange. The differences are discussed and evaluated.

Mechanism of formation of nonsteady-state absorption spectra from excited states of phenazines on the picosecond time scale

1991 ◽  
Vol 55 (1) ◽  
pp. 692-696 ◽  
Author(s):  
S. F. Dobrinevskii ◽  
A. V. Karypov ◽  
G. V. Maier ◽  
S. A. Tikhomirov ◽  
G. B. Tolstorozhev
Keyword(s):  
Absorption Spectra ◽  
Excited States ◽  
Time Scale ◽  
Mechanism Of Formation ◽  
Picosecond Time Scale ◽  
Nonsteady State
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