Harvesting thermal fluctuations: Activation process induced by a nonlinearchain in thermal equilibrium

We present a model in which the immediate environment of a bistable system is a molecular chain which in turn is connected to a thermal environment of the Langevin form. The molecular chain consists of masses connected by har monic or by anharmonic springs. The distribution, intensity, and mobility o f thermal fluctuations in these chains is strongly dependent on the nature of the springs and leads to different transition dynamics for the activated process. Thus, all else (temperature, damping, coupling parameters between the chain and the bistable system) being the same, the hard chain may prov ide an environment described as diffusion-limited and more effective in the activation process, while the soft chain may provide an environment descri bed as energy-limited and less effective. The importance of a detailed unde rstanding of the thermal environment toward the understanding of the activa tion process itself is thus highlighted. (C) 2000 American Institute of Phy sics. [S0021-9606(00)00723-6].