Use of the isomeric nucleus ²³⁵U^m as a probe for surface adsorption and desorption studies

When ²³⁵U^m nuclei are deposited on a metallic surface, they exhibit two distinct nuclear decay constants, corresponding most probably to chemisorbed atoms and to physisorbed oxide molecules, respectively. In addition, when the ²³⁵U^m source is placed under vacuum, the analysis of the decay rate of the surface activity can yield the mean sticking time and the heat of adsorption of the physisorbed molecules; it also gives information on the conversion electron spectrum of the desorbing ²³⁵U^m nuclei. Results obtained with ²³⁵U^m adsorbed on Pt, Cu and Ti are presented.