In a detailed study of thermal desorption of monolayers of both ${}^{\mathrm{4}}\mathrm{H}\mathrm{e}$ and ${}^{\mathrm{3}}\mathrm{H}\mathrm{e}$ adsorbed on Pt(111) (binding energy about 9 meV), we have observed photodesorption induced by the blackbody radiation from a room temperature environment. This process proceeds independently of the thermal desorption. Theoretical treatments of both thermal and photodesorption are given and agree very well with the data in all important aspects. We conclude that the photodesorption is due to direct coupling of photons to the adsorbate.

• Received 17 May 2002

DOI:https://doi.org/10.1103/PhysRevLett.89.126101