PHOTOCHEMICAL HYDROGEN DESORPTION FROM H-TERMINATED SILICON(111) BY VUV PHOTONS

The 7.9 eV photons of a F-2 laser induced photochemical desorption of molecular hydrogen from Si(111)-(1 x 1):H surfaces with a cross sectio n of (1.2 +/- 0.8) x 10(-20) cm(2). The time-of-flight detection of de sorbing species and numerical calculations of surface heating clearly allowed photochemical Fz-laser (7.9 eV) desorption and photothermal Xe Cl-laser (4.0 eV) desorption to be distinguished. Molecular dynamics s imulations indicate the appearance of atomic and molecular hydrogen. T he efficiency of photodissociation and desorption is higher than for t he electron-stimulated process.