ADSORBATE STRUCTURE AND ANGULAR-DEPENDENCE OF DESORPTION DYNAMICS - O2 PHOTODESORBED FROM PD(111)

O2 adsorbed on Pd(111) is photodesorbed and photodissociated when irradiated with 5.0 eV light. Polar and azimuthal angle-resolved time-of-flight spectra of the directly photodesorbed neutral molecules were measured. Both desorption flux and the translational energy were found to depend on the desorption angle. In particular a marked maximum in the translational energy at a polar angle of 60-degrees-with C3v symmetry is found for the superoxo species. This behavior is interpreted to be correlated with the binding geometry of the molecules before desorption.