Controlling surface reactions of hydrogen atoms by the electron spin.

Gas molecules possess various internal degrees of freedom. Whereas recent advances in surface dynamics have clarified the roles of translational, vibrational and rotational motion in gas-surface reactions, the effect of its electron spin on surface reactions remains poorly understood. Here, we demonstrate the spin dependence of H adsorption and abstraction reactions on a Ni surface using a spin-polarized atomic-hydrogen beam. The results indicate that H adsorption is suppressed when the H electron spin is oriented perpendicular to the magnetization direction of the Ni(111) surface. Furthermore, the same spin preference is observed for the H abstraction reaction on a D-covered surface. These findings suggest that controlling the spin orientation of molecules and surfaces by applying an external magnetic field provides a viable means to modulate surface reaction rates.