**************** The 12th., Lab Seminar *****************

Date: Mon, September 12, 2005  PM 1:30-

Place: No.616 Seminar room
　　　　　　 Graduate School of Information Science

Speaker: Yoshiyuki Koyano

Title: External noise imposed on the reaction-diffusion system 
CO + O2→CO_2 on Ir(111) surfaces: Experiment and theory
Yumino Hayase, Stefan Wehner, Jurgen Kuppers and Helmut R. Brand.
Phys. Rev. E 69 (2004), 021609.

Abstract:
 We study experimentally and theoretically the influence of noise on 
the fractions of CO and oxygen in the constant gas flow directed at 
an Ir(111) surface during CO oxidation. Depending on the noise strength 
and the fraction Y of CO we observe in the deterministically bistable 
region a large variety of different types of behavior. These include 
bistable behavior for small noise intensities, transitions from the 
upper to the lower branch of the bistable loop and vice versa, island 
nucleation and growth and noise-induced switching. Near the boundary 
of the bistable region and in the presence of noise the transition 
between the two branches takes place via very slow domain wall motion 
with time scales of the order of 10^4-10^5 s. The experiments were 
carried out in an UHV system for which the mass flow could be controlled 
very precisely. The modeling was using the reaction-diffusion system 
underlying the reaction studied for which all the kinetic coefficients 
are known rather precisely. Our numerical analysis was performed for 
one and two spatial dimensions showing qualitatively similar behavior. 
The comparison between the experimental results and the modeling shows 
semiquantitative to quantitative agreement. 

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