ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
If a Pt(100) sample is kept at steady-state conditions of O2 and CO partial pressures and temperature which are similar to those for the occurrence of autonomous temporal oscillations in the rate of CO2 formation, then the surface will be largely covered by adsorbed CO which inhibits oxygen adsorption and keeps the catalytic rate low. Irradiation of a small spot with a high power laser pulse causes momentarily local thermal desorption of CO and creation of a reaction front which propagates as a chemical wave across the surface area, as was monitored by the excursion of the integral reaction rate and locally by means of a work function (=oxygen coverage) probe placed at several mm distance from the spot of irradiation. The velocity for wave propagation rises from about 2 mm/min at 480 K to 4 mm/min at 507 K and is not noticeably dependent on the partial pressures. The mechanism is closely related to that for self-sustained kinetic oscillations of this system and exhibits the typical features of trigger waves: Coupling between autocatalytic reaction and diffusion, as well as the occurrence of a refractory period during which the system is "dead,'' and of a threshold for the intensity of the excitation.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.456740
