The partial ionization cross section for the formation of SF3+ fragment ions following electron impact on SF6 is known to have a pronounced structure in the cross section curve slightly above 40 eV. We used the mass-analyzed ion kinetic energy (MIKE) scan technique to demonstrate the presence of a channel contributing to the SF3+ partial ionization cross section that we attribute to the Coulomb explosion of doubly charged metastable SF42+ ions into two singly charged ions SF3+ and F+, with a threshold energy of about 45.5 eV. Thus the observed unusual shape of the SF3+ partial ionization cross section is the result of two contributions, (i) the direct formation of SF3+ fragment ions via dissociative ionization of SF6 with a threshold energy of 22 eV and (ii) the Coulomb explosion of metastable SF42+ ions with a threshold energy of about 45.5 eV. A detailed analysis of the MIKE spectrum reveals an average kinetic energy release of about 5 eV in the Coulomb explosion of the SF42+ ions with evidence of a second channel corresponding to an average kinetic energy release of about 1.1 eV. (C) 2004 American Institute of Physics.