  Monte Carlo simulation is used to study the dynamical crossover from single
file diffusion to normal diffusion in fluids confined to narrow channels. We
show that the long time diffusion coefficients for a series of systems
involving hard and soft interaction potentials can be described in terms of a
hopping time that measures the time it takes for a particle to escape the cage
formed by its neighbors in the pore. Free energy barriers for the particle
hopping process are calculated and used to show that transition state theory
effectively describes the hopping time for all the systems studied, over a
range of pore diameters. Our work suggests that the combination of hopping
times and transition state theory offers a useful and general framework to
describe the dynamics of these highly confined fluids.
