Effect of spin—orbit excitation on chemical reactivity: Laser transient absorption spectroscopy of Br(2P12, 2P32 + IBr reactive dynamics

A laser pulse-and-probe technique incorporating a tunable infrared color center laser is used to study the reactions and quenching of Br(2P12, 2P32) with IBr. A highly selective spin—orbit effect on chemical reactivity is observed. The ground-state reaction, Br(2P32)+IBr → Br2 + 1, k = (4.6 ± 0.6)×10−11 cm3 molecule−1 s−1 proceeds at a rate ≥ 40 times faster than the rate of total Br- quenching and reaction with IBr.