Molecular and atomic deuterium chemisorption on thin gold films at 78 K: an isotope effect

The adsorption of molecular and atomic deuterium on gold films was investigated by thermal desorption mass spectrometry (TDMS). It has been found that a small amount of deuterium molecules in the ground state, possessing low kinetic energy, chemisorb at 78 K on a clean surface of thin, unsintered gold films deposited at the same temperature. Single desorption spectra with maxima at 120–125 K are observed. On the other hand, at low coverage (θ < 0.01) and 78 K the adsorption process of atomic deuterium on sintered Au films is characterized by a single, symmetrical thermal desorption (TD) spectrum with a maximum at 182 K and a calculated activation energy for desorption of 60 kJ/mol D2. The thermal desorption spectra for deuterium are compared with those previously obtained for the hydrogen-gold system. An isotope effect is thereby shown to occur for the desorption event.