CAN THE STRONG COLLISIONALLY INDUCED SPIN-ORBITAL RELAXATION OF HALOGEN ATOMS BE ACCOUNTED FOR BY QUENCHER PARAMAGNETISM

Deactivation rate constants of spin-orbital excited Br atoms in the reactions Br(2P 1 2) + O2 → Br(2P 3 2) + O2 (k1), and Br(2P 1 2) + NO → Br(2P 3 2) + NO (k4) have been measured with a photodissociative IBr laser on the electronic transition 2P 1 2-2P 3 2 in the Br atom (λ = 2.7 μm). The values obtained are (6.4 ± 1.8) × 10-14 cm3 s-1 and (1.9 ± 0.6) × 10-12 cm3 s-1, respectively. Comparison with published data leads to the conclusion that, contrary to a widely accepted point of view, the high rate constants for the quenching of excited halogen atoms are due to resonant energy transfer processes and not to the paramagnetic nature of the quencher. © 1979.