Monte Carlo Simulation of Radiation Trapping in Hg–Ar Fluorescent Discharge Lamps

The line spectra of emitted resonance radiation from mercury and the effective decay rates of the Hg 6³P₁ and 6¹P₁ levels in mercury–argon discharges are simulated by a Monte Carlo method. The hyperfine splitting, the natural isotopic composition, collisional transfer of excitation, foreign gas collisions and quenching are considered to describe in detail the 253.7 nm and 184.9 nm lines. The calculations are performed for Hg vapor densities corresponding to coldest spot temperatures of 5–100°C, and discharge parameters typical for fluorescent lamp operation. The densities of the Hg 6³P₁ and 6¹P₁ levels are consistently estimated by means of a set of balance equations for the Hg 6³P₀, 6³P₁, 6³P₂, and 6¹P₁ excited states. The resulting uv radiation output of the discharge is then estimated for a tube radius of 18 mm, argon pressure of 400 Pa, discharge current 0.4 A, and wall temperatures of 20–80°C. The results obtained show a good agreement as compared with published experimental data.