Absolute ionisation functions for electron impact with barium

Absolute ionisation functions sigma n+ (E)(n=1,2,3,4) and the total ionisation function sigma tot (E) for electron impact with barium have been determined for energies up to 600 eV. Modified crossed-beam techniques were applied using the excitation function of the light from the resonance transition as a reference standard for the cross sections. A time-of-flight device was used to separate ions with different charges.