Periodic Perturbation of the BZ-Reaction in a CSTR: Chemical Resonance, Entrainment and Quasi-Periodic Behavior

Abstract

Chemical oscillations may occur in open non-linear kinetic mechanisms far from chemical equilibrium. They may show a variety of interesting phenomena when they are periodically perturbed by an external source. These phenomena include chemical resonance, entrainment, quasi-periodic behavior and even chaotic responses. While a number of theoretical discussions have been given on the subject of periodic perturbations of oscillating isothermal chemical reactions [1–10], there exist only few experimental verifications of some of these phenomena [11–15] in chemical systems. Here we report the results of initial experiments on the periodic perturbation of the Belousov-Zhabotinsky (BZ) reaction in an isothermal continuous flow stirred tank reactor (CSTR). We describe two sets of experiments. In the first set, the BZ reaction is altered to be a damped oscillator (in the presence of in-flowing KBr) and, in the second part, it behaves as a stable limit cycle. Both instances are investigated with the same experimental technique. A periodic perturbation is applied to the reacting system in the form of sinusoidal flow-rate changes as effected by a regulated high-precision syringe pump. We observe a single broad resonance curve for the damped BZ-reaction. For the undamped BZ-reaction, several sharp resonances in various entrainment bands, as well as quasiperiodic behavior are observed. In the transition region between fundamental entrainment and quasi-periodic response, the Fourier spectra slowly change with time.