Photodissociation of HBr adsorbed on the surface and embedded in large Ar_n clusters 机翻标题: 暂无翻译,请尝试点击翻译按钮。

journal of chemical physics
2000 / V.113 / N.1
Max-Planck-Institut fur Stromungsforschung; Bunsenstra#beta#e 10; D-37073 Gottingen; Germang;
Reinhard Baufalk;
Ultraviolet (UV) photodissociation experiments are carried out for Ar~(HBr) clusters in which the HBr is adsorbed on the surface of the Arm, and also on isomers of these systems in which HBr is embedded within the rare-gas cluster. The mean size of the cluster distribution in the experiments is around ~= 130. The kinetic energy distribution (RED) of the hydrogen atoms that left the clusters is measured. Molecular dynamics (MD) simulations of the photodissociation of the--chemically similar clusters Ar~(HCl) are used to provide a qualitative interpretatton of the experimental results. The clusters with embedded HBr give a very cold H-atom KEU. The clusters with the surface-adsorbe4 HBr give’a RED with two peaks,one corresponding to very low energy H atoms and the other pertaining to high -energies, of the order of 1.35 eV. The theoretical simulations show that already for n = 54, there is a strong cage effect for the ‘embedded” molecule case, resulting in slow H atoms. The surface-adsorbed case is interpreted as due to two types of possible adsorption sites of HX on Ar~: for a locally smooth adsorption site, the cage effect is #elatively weak, and hot H atoms emerge. Sitea wbere’the H& is adswt~sd at a vacancy of Ar~ lead to ‘~encapsulation” of the H ~m prq~h~kd, with x s&oiig cage7effoeL A weak tail of H atoms with energies well above the H& m.inm~a~ excess enew~y is observed fo~ the embedded case. Simulations support that this is da~ to a s6c6nd photon absorption by recombined, but still vibrationally hot, HEr. The results throw light on the differences between the cage effect inside bulk structure and at surfaces,
Reinhard Baufalk; Max-Planck-Institut fur Stromungsforschung, Bunsenstra#beta#e 10, D-37073 Gottingen, Germang; journal of chemical physics; V.113 N.1 2000; 329-338