A detailed consideration of resonance radiation trapping in the argon inductively coupled plasma

The extent and duration of trapping of argon resonance radiation (106.7 and 104.8 nm) in the ICP was calculated using a model incorporating line shape contributions from both Doppler and pressure broadening. The trap was found to be at the pressure-broadened limit, giving an escape factor of 7.9 × 10^?4 when excitation of the 4s states in the plasma annulus is assumed. Theoretical apparent radiative lifetimes τ_app for argon ³P₁ and ¹P₁ resonance states are calculated to be 8 and 1.9μs respectively. The quartet of 4s states, rapidly mixed by electron collisions, are presumed to share an overall apparent radiative lifetime τ_app = 1.6μs for the purpose of plasma modeling. Effects of this radiation trapping on the argon 4s atom density and on electron-ion recombination are discussed.