Muonium chemistry: kinetics of the gas phase reaction Mu + F2 → MuF + F from 300 to 400 K

The MSR (muonium spin rotation) technique was used to measure the chemical reaction rate for Mu + F₂ → MuF + F in N₂ moderator at ≈ 1 atm from 295 to 383 K giving the Arrhenius expression: log₁₀k (?/mole s) = (10.83 ± 0.20) - (200 ± 50)/T, with k = (1.46 ± 0.11) × 10¹⁰ ?/mole s at 300 K. This is at least 6.8 times the room temperature rate constant for the analogous H atom reaction. The measured activation energy and enhancement over the H reaction rate are indicative of significant tunnelling in the Mu reaction, in agreement with the recent collinear quantum mechanical calculations of Connor et al.