Correlation Study of the Spin-Orbit State-Resolved Scattering of Al(²P) in Oxidation Reaction and Nonreactive...

Spin-orbit coupling plays an important role in chemical reactivity, especially in reactions that require the change of electron spin states. However, it is difficult to measure and analyze the reaction dynamics between spin-orbit splitting states, particularly for splitting states with a small energy difference. In this study, we find that nonreactive scattering of spin-orbit splitting states can provide complementary information that is overlooked in chemical reaction studies. Here, the oxidation reactivities of spin-orbit Al(²P_1/2,3/2) states with small energy difference of 112 cm^-1 are clearly distinguished in the high rotational AlO(v = 0 and 1, N) products at low collision energy of 507 cm^-1 using a laser ablation crossed-beam and time-sliced ion velocity mapping technique, in conjunction with state-selected nonreactive scattering studies. For both the AlO(v = 0 and 1) channels, the spin-orbit relative reactivity σ_3/2/σ_1/2 increases with the increase of rotational level N of AlO products. However, for AlO(v = 0), the reactivity of the Al(²P_3/2) excited state is consistently lower than that of the Al(²P_1/2) ground state, whereas for AlO(v = 1), the reactivity of Al(²P_3/2) is higher than that of Al(²P_1/2) at a higher rotational state. The relative reactivity of spin-orbit split Al(²P) states at different scattering angles shows a more pronounced enhancement of forward scattering relative to side and backward scattering for Al(²P_3/2) when a higher rotationally excited AlO is produced. Nonreactive scattering studies of Al(²P) suggest that the Al(²P_3/2) state is deexcited to the ground Al(²P_1/2) state at the sideways and backward scattering directions, and the deexcitation is supposed to reduce the reactivity of the excited Al(²P_3/2) at the corresponding direction.