An experimental and theoretical investigation of the valence double photoionisation of the iodine molecule

The double photoionisation spectrum of molecular iodine has been measured at three wavelengths by the TOF-PEPECO technique and is interpreted using relativistic molecular structure COSCI calculations of potential curves for a large number of electronic states connected to the three lowest groups of dissociation limits. The lowest double ionisation energy is 24.85 +/- 0.02 eV (adiabatic) or 24.95 +/- 0.02 eV (vertical). It is associated with the (3)Sigma(-)(g,0) electronic state I-2(2+). The double ionisation process is mainly direct, and positions and widths of the bands are well reproduced by the calculations. (c) 2005 Elsevier B.V. All rights reserved.