Light Emission from Mercury Gas Discharge

Recombination of fhe ionized elecfron wifh the argon cation produces an electronically excited argon atom, which can energize and subsequently ionize a mercury atom  

The electronically excited mercury atom generated by the recombination of the mercury cation with an electron loses its energy radiatively. The above are only a few of fhe processes fhaf fake place in the lamp, but the combined effect is the emission of light in the UV and visible regions and the generation of heat The heat vaporizes some of fhe mercury mefal. The mercury cations are conducting and the current passing across the electrodes rises until a steady state is reached. 

2 Light Emission from a Microwave-Excited Discharge 

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Mercury or xenon arc lamps are used. A schematic of a xenon arc lamp is given in Fig. 5.42. The quartz envelope is filled with xenon gas, and an electrical discharge through the gas causes excitation and emission of light. This lamp emits a continuum from 200 nm into the IR. The emission spectrum of a xenon arc lamp is shown in Fig. 5.43. Mercury lamps under high pressure can be used to provide a continuum, but low-pressure Hg lamps, which emit a line spectrum, are often used with filter fluorometers. The spectrum of a low-pressure Hg lamp is presented in Fig. 5.44. 

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