Free-ion yield in liquid argon at low-LET

A re-encounter model is proposed for electron—ion recombination on low-LET tracks in liquid argon. Consistency with measured escape probability for fields > 1 kV cm−1 requires an encounter recombination probability ≈ 0.01. The initial e—ion separation (≈ 1500–1800 nm) is reconciled with thermalization by elastic collisions. Due to homogeneous recombination the experimental values fall below the calculated ones for fields less than ≈ 1 kV cm−1.