Knowledge Bank

$C2$ Swann band emission $(d3\Pi -a3\Pi \mu 170ns$. lifetime) is observed in a supersonic free jet using a pulsed laser/vaporization source with a graphite target. In helium, Swann band emission is observed at distances of up to 15 nozzle diameters from the orifice and at times as long as 6us after the vaporizing laser pulse. The emission studies are reported as a function of laser intensity, backing pressure, downstream distance, and delay times. Evidence supporting the continuous localized formation of excited $C2$ molecules in the free jet via dissociative processes involving larger neutral and charged carbon clusters is presented, and the bearing of these results on the interpretation of cluster stability data is discussed.