Langevin equation thermal agitation

The Langevin equation, Eq. (11.5), that was used in Kramers calculation of the dynamical effects on the rate constant, is only valid in the limit of long times, where an equilibrium situation may be established. The reaction coordinate undergoes many collisions with the atoms in the solvent due to thermal agitation. From the Langevin equation of motion and Eq. (11.9), we obtained an expression for the autocorrelation function of the velocity ... 

In order to discuss the Langevin equation for a single domain ferrofluid particle we first consider Gilbert s equation for the dynamic behavior of the particle s magnetization vector M in the presence of thermal agitation, which is Eq. (1.12),... 

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