Hg 61P1 excited-state densities and 185.0 nm UV surface irradiances in a low-pressure mercury vapour discharge column

Abstract

A spectral line absorption method was used to determine the Hg 61P1 excited-state densities in low-pressure mercury vapour (of the order of 10-1 Pa) discharge columns with various diameters. Two spectral lines, 576.96 nm (the transition between 63D2 and 61P1) and 579.07 nm (the transition between 61D2 and 61P1), were separately chosen for the measurements and both results were in good agreement. The data obtained about the 61P1 state density were used to calculate the 185.0 nm surface irradiances of various diameter discharge columns by resonance radiation imprisonment theory. It was found that the 185.0 nm irradiance of a 10 mm diameter column, corresponding to newly developed compact fluorescent lamps, was one order larger than that of a 36 mm or 28 mm diameter column, corresponding to conventional fluorescent lamps, which seems to support the speculation that the rapid decay of the lumen output of the compact fluorescent lamps with conventional halophosphates is due to the intense 185.0 nm radiation.