Measurement of the adsorption energy on single crystal faces by field emission (hydrogen on tungsten)

As a preliminary study has shown¹), the isosteric energy of adsorption on single crystal faces can be measured, if the coverage is kept constant on controlling the field electron currents. This method has been improved (a) by the introduction of the probe hole technique, (b) by special cleaning procedures, and (c) by a more precise measurement of gas pressure and temperature. The method is used to obtain the adsorption energy q of hydrogen on the tungsten faces (100), (111), (112), (013), (122), (123) and (114). Initial q-values vary between 33 kcal/mole on (013) and 40 kcal/mole on (112). q decreases with coverage down to a few kcal/mole. The results indicate a relation between the adsorption states and the structure of each face.