Radiation trapping of the Hg 185 nm resonance line

Summary form only given. The trapped decay rate of the 6/sup 1/P/sub 1/ level at 185 nm was measured as a function of cold spot temperature (Hg density) and buffer gas pressure in cylindrical sealed fused silica cells. The decay rates were obtained using time-resolved, laser induced fluorescence after multi step laser excitation at 253.7 nm and 312.6 nm. Cold spot temperatures from 25/spl deg/C to 100/spl deg/C were studied. The Hg densities for this temperature range with no buffer gas yield the lowest possible trapped decay rates due to partial frequency redistribution. Argon buffer gas pressures of 3 and 30 Torr were also studied. The results are in agreement with the afterglow data of Post (1986) for zero buffer gas pressure. Monte Carlo simulations of radiation transport in the cell, including the effects of hyperfine and isotope structure and the effects of foreign gas broadening, agree well with the experimental data.