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Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: DaveD on March 01, 2007, 08:37:35 PM

Title: Non-statistical dynamics
Post by: DaveD on March 01, 2007, 08:37:35 PM

Hi all -

This is my first post on this site.  I am preparing a literature seminar on current concepts in reaction dynamics from a theoretical and experimental point of view.  I have a question about the concept of non-statistical dynamics.  Could someone help clarify this concept to me?  I've written down my understanding of this, and welcome your thoughts/criticism.  Thanks!

Potential energy surfaces can be calculated and then used in understanding geometries and energies of reacting chemical species.  Reactant molecules can traverse a number of different paths (or trajectories) on their way through transition structures, intermediate structures, and on to products.  The statistical approximation allows for estimation of rate constants without needing to specify which trajectory is selected, by assuming that the rate of intramolecular vibrational energy redistribution is a lot faster than passage through a transition structure.  In other words, although structures in the transition region that may arrive via different trajectories and possess different vibrational energies - these energies statistically randomize rapidly to produce an ensemble of geometries and energies.

I think non-statistical dynamics refers to situations in which transition structures with different energies do not randomize - but instead exit the transition region via different trajectories to form product(s).  Is this correct?

Thanks again .

DaveD