DISSOCIATIVE PHOTOIONIZATION STUDY OF O-2

Dissociative photoionization of O-2 is Studied by an energy-mass analy zing system and synchrotron radiation. The kinetic energy distribution spectra of the O+ ion fragments and the dissociative photoionization efficiency curves for the O+ fragments with zero and 0.8 eV kinetic en ergies are observed at photon energies from 18.5 to 24.7 eV. Two vibra tional progressions are observed in the zero kinetic energy O+ spectru m and identified as Rydberg series ns sigma(g) (n = 4 and 5) convergin g to the 3(2)Pi(u), ionic state of O-2 The spectroscopic constants for these Rydberg states are obtained. Post dissociative autoionizations are observed for the O(P-2)nd ''(n = 3 similar to 5) atomic states in the zero kinetic energy O+ spectrum. A shape resonance structure for the B(2)Sigma(g)(-), ionic state is observed in the 0.8 eV kinetic ene rgy O+ spectrum. The related dissociation mechanisms are discussed. (C ) 1998 Elsevier Science B.V. All rights reserved.