Enhancement factor in the emission intensities excited by radiofrequency-powered glow discharge plasma associated with bias-current introduction

The introduction of a d.c. bias current to an r.f. glow discharge plasma led to enhancement in the intensities of particular emission lines. Atomic emission lines having the excitation energy of 3-4 eV were commonly enhanced 10-20 times by conducting the bias current of 20-30 mA. The enhancement factor strongly depended upon both the pressure of the plasma gas and the r.f. applied power. The intensities of atomic emission lines having the excitation energy of c.a. 5.7 eV were much more elevated and their enhancement factors exceeded 50. However, little increases for emission lines having the excitation energy more than 7 eV were observed regardless of the plasma conditions.