Electron capture by ions in a Rydberg atom target

Electron capture by a singly charged ion in a state-selected target of highly excited Rydberg atoms populates a wide but definite range of Rydberg states on the projectile. Crossed-beam experiments with ions at energies around 1 keV and laser-excited Na Rydberg states n=24 to 34 have investigated the electron-capture reaction with comparable projectile and electronic velocities. The variations of final-state n distributions with respect to initial n and projectile velocity exhibit consistent patterns and challenge theorists to address the Rydberg electron-capture problem at intermediate velocity in new ways. The importance of collisional l mixing in state-selected Rydberg targets and the complexities of field ionization are particularly stressed as limitations on fully resolved state-to-state experiments