EXCITATION OF AR LINES IN THE CATHODE REGION OF A DC DISCHARGE

Measurements of the spatial distribution of different Ar lines are rep orted for a Bat cold cathode discharge in the j/P-2 range of 10(-4) to 10(-2) A cm(-2) mbar(-2), where j is the current density and P is the pressure. In this range, excitation by heavy particles and by electro ns can be studied since they produce a cathode glow and a negative glo w that are well separated. With increasing j/P-2 the heavy-particle ex citation and the cathode glow increase, while the negative glow extend s to a larger distance. The voltage, the pressure (P) times the length s of the cathode glow and the cathode sheath, and the fraction of the input energy that goes into the negative glow and the cathode glow hav e a dependence on j/P-2 that is independent of pressure. We also repor t data on the decay of the negative glow beyond its peak, but this dec ay length times pressure has a dependence on j/P-2 that changes with p ressure. The measured voltage and lengths are compared to previous dat a and to a recent calculation.