MEASURING THE ABSOLUTE STICKING PROBABILITY AT DESORPTION TEMPERATURES

Measuring the sticking probability is important both in understanding gas-surface interactions and in interpreting surface catalytic reactions. Existing techniques cannot be used to measure the absolute sticking probability at desorption temperatures, where a net sticking probability is obtained instead. We introduce a simple method in which net sticking probabilities are measured versus the impingement rate (z) and then extrapolated to 1/z = 0 to obtain the absolute sticking probability. The method is applicable to both dissociative and non-dissociative adsorption systems and no calibration is needed in the sticking probability itself. The method is illustrated for CO adsorption on Pt(100)-hex-R0.7 degrees at surface temperatures from 380 to 410 K, and the results are discussed in comparison with a previous assessment of the data.