Competition between different excitation processes of the Cd(II) 5s22D5/2state at low discharge currents in the positive column He-Cd+laser discharge

The population densities of He and Cd states and electron density were measured at low discharge currents (2 to 30 mA) in the positive column He-Cd + laser discharge. It is shown that the Penning excitation rate to the upper state of the Cd(II) 441.6 nm laser line becomes saturated for currents well below 10 mA, and that although the Penning excitation process is dominant in the region of a few mA, the stepwise excitation process from Cd(II) ground state must become the dominant one under lasing conditions.