Mass spectrometry and photoemission spectroscopy of a graphite hollow catho
de source identify the parameters of the transition from the C-3-dominated
discharge to the sooting plasma. The transition is a function of the shape
and profile of a special cusp magnetic field B-z(r, theta), the geometry of
the source, the discharge current, and pressure. Characteristic atomic and
molecular emission lines and bands in the C-3 discharge transform into bro
ad bands emitted by the excited soot. We identify four prominent emission b
ands between 300-400 nm to be the hallmark of the sooting plasma.