Published online by Cambridge University Press: 14 August 2015
An experiment has been performed to determine the thermal accommodation coefficients for the gases hydrogen, oxygen, methane, and carbon dioxide on graphite, in the temperature range 273–77 K. The experimental results are compared to those indirectly predicted in a theoretical paper by Hollenbach and Salpeter, and agreement is found to be satisfactory. A sticking coefficient for atomic hydrogen on a graphite grain is derived which would support the conclusion that recombination of hydrogen on grain surfaces could be a significant process. The very high measured thermal accommodation coefficients for the heavier gases supports the popular assumption that retention of such gases on grain surfaces should be considered extremely likely.