Low and high coverage determinations of the rate of carbon monoxide adsorption and desorption from Pt(110)

The adsorption probability of CO on Pt(110) was determined to be 0.7 by modulated beam (MBRS) and thermal desorption over a temperature range of 195 to 625 K. By MBRS the desorption rate constant, kd, was measured to be 6×1014 exp{−35.3 (kcal mol−1)/RT s−1} in the low coverage limit. This high value for the desorption pre-exponential factor was explained utilizing transition state theory. The low coverage value of kd was employed to calculate the thermal desorption spectrum, describing the adsorbed state by a one-dimensional Ising model. The repulsive interaction parameter which yielded the best fit was ω=1.5+2.5ϑ kcal mol−1.