Slow variable regime motion

As a result, the traditional picture of liquid phase reaction dynamics —solute motion in the potential of mean force damped by friction— holds only for slow variable regime reactions. For fast variable regime reactions the nonclassical picture of Eq. (3.36) and Figure 3.5 applies. 

We next point out that the near equilibrium physics of the slow variable regime gives rise to a very simple picture of particle motion and underlies the traditional concept of frictional damping. 

Thus, in the slow variable regime the following picture of particle motion applies ... 

We have also found that very different pictures of the motion and very different concepts of dissipation emerge in the two limiting regimes. These are summarized in Eqs. (3.29) and (3.30) and Eqs. (3.36) and (3.37). In particular, the potential energy function that drives the process xf S) Xf=o S) is different in the two regimes namely, it is the potential of mean force W S x) in the slow variable regime, and the instantaneous potential V S x) in the short time regime. 

The plan of this chapter is as follows. In Section II and the Appendix we review some basic topics in statistical mechanics that underlie questions concerning the regimes of validity of slow and fast variable descriptions of irreversible motion. 

This concludes our comparison of particle motion in the slow and fast variable timescale regimes. 

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