Decay of Intensity of Certain Hg Lines in an Hg–Ar Discharge*

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Abstract
The afterglow of four mercury spectral lines was examined in a mercury–argon electric discharge. The 2537-Å line decays in a complex fashion with three definite modes of decay. The 4077-, 4358-, and 5461-Å lines exhibited an even more complicated decay. These lines exhibited an initial rapid decay followed by an increase in intensity. Finally the intensity of these lines went through two maxima before they decayed in intensity at a slow constant rate. The actual intensity behavior of the 2537-Å line was masked by the imprisonment of resonance radiation. It is postulated that the main processes governing the initial decay were spontaneous radiative decay coupled with electron and ion repopulation of the excited mercury states. The negative decay constant occurring around 100 μsec was probably controlled by the group action of the following processes: ionization of mercury by argon and the resultant recombination, thermalization of discharge electrons and their resultant recombination, and production of electrons by the interaction of mercury metastable atoms and their recombination. The final slow rate of decay was probably controlled by mercury molecular dissociative recombination.