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 reactio ns. Existing techniques cannot be used to measure the absolute stickin g probability at desorption temperatures, where a net sticking probabi lity is obtained instead. We introduce a simple method in which net st icking probabilities are measured versus the impingement rate (z) and then extrapolated to 1/z = 0 to obtain the absolute sticking probabili ty. The method is applicable to both dissociative and non-dissociative adsorption systems and no calibration is needed in the sticking proba bility 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 re sults are discussed in comparison with a previous assessment of the da ta.