Exploring the spin-orbit reactivity in the simplest chlorine atom reaction

The reaction of Cl(P-2)+H-2--> HCl+H serves as a benchmark for understanding the abstraction mechanism and has been the subject of numerous experimental and theoretical studies. Despite such intensive investigations, the reactivity of the low-lying spin-orbit excited Cl*(P-2(1/2)) is unknown and has always been assumed to be negligibly small. By exploiting two different sources for generating the Cl(P-2) beam, it is now found that the excited Cl*(P-2(1/2)) atom is surprisingly more reactive to H-2 than the ground state Cl(P-2(3/2)) reagent, overturning conventional wisdom. By using a technique called Doppler-selected time of flight to directly map out the doubly differential cross sections (angle and speed), the detailed dynamical attributes for both spin-orbit states are also elucidated and contrasted for the first time for any bimolecular reaction. (C) 1999 American Institute of Physics. [S0021-9606(99)02538-6].