Dissociative Double Ionization of O2 Below the Adiabatic Double
Ionization Potential

P. Bolognesi #, D.B. Thompson #^2, L. Avaldi ^n, M.C.A. Lopes #", M.A.
MacDonald*, D.R. Cooper # and G.C. King #

#  Schuster Laboratory, Physics Department, The University of
#  Manchester, Manchester M13 9PL, UK
^n IMAI del CNR, Area della Ricerca di Roma, CP10-00016 Monterotondo,
Italy * Daresbury Laboratory, Daresbury, Warrington, WA4 4AD, UK

Mechanisms for O2 fragmentation leading to the formation of the O+- O+
 ion pairs, in the photon energy region 32-41 eV, have been
investigated using a threshold-photoelectron-photoelectron coincidence
(TPEPECO) technique. The measurements show that fast dissociation of a
singly-charged ion, followed by atomic autoionization, is the dominant
decay route in this energy region.