PERIODIC AND RANDOM PERTURBATION OF A SYSTEM EXHIBITING DAMPED KINETIC OSCILLATIONS PT(100)/NO+CO

The NO + CO reaction, which has been shown to exhibit damped kinetic oscillations on a Pt(100) surface after initial excitation, has been subjected to periodic and random forcing of the temperature and of the CO partial pressure. The experiments were conducted in the 10(-7) mbar range and measurements of the CO2 production rate and of the work function were used to follow the response of the system. The response behavior is characterized by strong resonance effects and by the absence of quasiperiodic oscillations. The system is highly sensitive to temperature modulation, but rather insensitive to modulation of p(CO) with the latter requiring an amplitude of more than 5% of p(CO) for producing sustained oscillations. Random forcing experiments demonstrate that the response of the system can be described as a bandpass filter since only frequencies close to the natural frequency of the system are amplified. The results of the experiments led to the conclusion that the damping effect is due to the absence of an efficient synchronization mode under isothermal conditions at low pressures.