Yao Yunxi, Giapis Konstantinos P
Division of Chemistry and Chemical Engineering , California Institute of Technology , Pasadena , California 91125 , USA . Email:
Chem Sci. 2017 Apr 1;8(4):2852-2858. doi: 10.1039/c6sc05065d. Epub 2017 Jan 18.
We report the direct formation of H and O pair ions through single collisions of water ions with metal surfaces at hyperthermal energies. This unusual intramolecular reaction proceeds also for heavy and semi-heavy water, producing molecular D and HD ions. The selectivity of this water splitting channel is estimated at being between 9 and 13% complete dissociation. The collision kinematics support the hypothesis of a water molecule colliding with a single surface atom, thereby forming an excited precursor (Rydberg?) state, which dissociates subsequently to form the molecular hydrogen ion with high kinetic energy. Inelastic energy loss considerations yield an estimate for the energy of the excited precursor state of ∼7 eV and ∼11 eV at low and high incidence energies. These energies are close to the à state (B, 7.5 eV) and B state (A, 9.7 eV) of excited water (Rydberg states).
我们报道了在超热能下，水离子与金属表面单次碰撞直接形成H和O对离子的过程。这种不寻常的分子内反应对重水和半重水也同样适用，会产生分子D和HD离子。该水分解通道的选择性估计在完全解离的9%至13%之间。碰撞运动学支持水分子与单个表面原子碰撞的假设，从而形成一个激发的前驱体（里德堡？）态，随后该态解离形成具有高动能的分子氢离子。非弹性能量损失的考虑得出了在低入射能和高入射能下激发前驱体态能量的估计值，分别约为7 eV和11 eV。这些能量接近激发态水（里德堡态）的Ã态（B，7.5 eV）和B态（A，9.7 eV）。
