PROMOTED FIELD DESORPTION

A study has been made of the promoted field desorption of the adsorbates H2, CH4 and Xe by He and of H2 and CH4 by Ar. In each case, the presence of the gas significantly lowers the desorption evaporation field of the adsorbate; in the presence of He, the fields for onset of field desorption of H2, CH4 and Xe converge to 3.0 V A ̊. Promoted field desorption is discussed in terms of energy transfer to the adsorbate by gas atom impact and by electronic excitation which is thought to be the dominant mechanism. A third mechanism involving formation of heteronuclear complexes of the type HeXe+ is not ruled out. © 1969.