Radiative Double-Electron Capture by Bare and One-Electron Ions on Gas Targets.

Radiative double-electron capture (RDEC) involves the transfer of two electrons with the simultaneous emission of a single photon. This process, which can be viewed as the inverse of double photoionzation, has been studied for 2.11 MeV/u F9+ and F8+ ions striking gas targets of N-2 and Ne. The existence of RDEC is conclusively shown for both targets and the results are compared with earlier O8+ and F9+ findings for thin-foil carbon and with theory. The data for the carbon target showed some evidence for the existence of RDEC, but the interpretation was clouded by high-probability, unavoidable multiple collisions causing the exiting charge state to be increased.