XeCl excimer fluorescence in a microwave discharge

Ultraviolet light sources are becoming increasingly useful to manufacturing applications such as the curing of inks, coatings, and adhesives. Intensive ultraviolet light can provide efficient curing without intense heat. Microwave driven lamps have many advantages including long lifetime, high overall efficiencies and high intensity emission; XeCl is one of many rare-gas halide excimers used in these systems. The experiment described here is used to understand the production mechanisms of XeCl as well as the optimal conditions for ultraviolet emission. A continuous wave discharge produced by 2.45 GHz microwaves is used to produce 308 nm fluorescence (B->X) and 236 nm fluorescence (D->X). Varying ratios of Xe and Cl2 are controlled by mass flow controllers and mixed in a mixing cell before flowing into a quartz tube, which lies along the centerline axis of an Asmussen microwave cavity. The emission of 236 nm tends to be much dimmer than the more prominent 308 nm emission. Emission from Xe atoms are also observed. Pressure ranges from a few torr to over 100 torr are used with microwave powers ranging from 100 W to 300 W. A comparison of the XeCl emission using different ratios of Xe and Cl2, and trends in power and pressure will be presented.