DETECTION OF 2 ELECTRONS IN LOW-LYING CONTINUUM STATES OF A SINGLE PROJECTILE ION RESULTING FROM THE COLLISION OF A 10.7-MEV AG(4+) ION WITH AN AR GAS ATOM

Two electrons, excited just above the double-ionization threshold of a n Ag(q+) (q = 5,6) core in a single collision of a 0.1-MeV/u Ag4+ proj ectile ion with an Ar atom, are detected. The electron detector consis ts of electrically isolated anode segments located behind a microchann el-plate electron multiplier. A large electrostatic 30-degrees paralle l-plate analyzer is used to deflect the two free electrons, which move with approximately the projectile velocity, into the detector. The cr oss sections for producing final states consisting of a positively cha rged ionic core and two electrons just above the threshold for double ionization in ion-atom collisions have been measured. The cross sectio ns for producing states with one electron moving with a kinetic energy less than 0.13 eV in the projectile frame and the other moving with s omewhat higher kinetic energy are presented.