A new technique for the study of charge transfer in multiply charged ion-ion collisions

While large cross sections (>10-16 cm2) have been predicted for resonant charge transfer in ion-ion collisions, no experimental data exist for multiply charged systems. A novel technique has been developed at the ORNL ECR facility to allow study of symmetric charge exchange in multiply charged ion-ion collisions using a single ion source. The approach utilizes the total (i.e., unanalyzed) beam extracted from the ECR source. Specific intra-beam charge transfer collisions occurring in a well-defined interaction region labeled by negative high voltage are identified and analyzed by electrostatic analysis in combination with ion time-of-flight coincidence detection of the collision products. Center-of-mass collision energies from 400 to 1000 eV are obtained by varying source and labeling-cell voltages. In addition, by the introduction of a target gas into the high-voltage cell, this labeling-voltage method allows measurement of electron-capture and -loss cross sections for ion-atom collisions. Consequently, higher collision energies can be investigated without the requirement of placing the ECR source on a high-voltage platform