Cm. Friedrich et al., COMPETING PHOTODISSOCIATION PATHWAYS FOR PHYSISORBED O-2 GRAPHITE INVESTIGATED USING AR SPACER LAYERS/, Chemical physics letters, 247(4-6), 1995, pp. 348-354
We have studied photon stimulated ion desorption from O-2 physisorbed
on graphite, using synchrotron radiation in the energy range 16-40 eV,
Ar spacer layers were employed in order to distinguish between direct
and indirect (photoelectron driven) dissociation channels, specifical
ly, (i) direct dipolar dissociation, (ii) direct dissociative ionizati
on, (iii) photoelectron driven dissociative attachment and (iv) photoe
lectron driven dipolar dissociation. We find that the O- yield is main
ly due to direct dipolar dissociation, while for O+ direct dipolar dis
sociation and both direct and indirect dissociative ionization are ide
ntified. The Ar layer reduces the image potential arising from the gra
phite substrate. Some dissociation pathways in the energy region 24-27
eV are enhanced for O-2/graphite compared with the gas phase.