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首页> 外文期刊>The Journal of Chemical Physics >QUANTUM MECHANICAL STUDIES OF PHOTODESORPTION OF AMMONIA FROM A METAL SURFACE - ISOTOPE EFFECTS, FINAL STATE DISTRIBUTIONS, AND DESORPTION MECHANISMS
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QUANTUM MECHANICAL STUDIES OF PHOTODESORPTION OF AMMONIA FROM A METAL SURFACE - ISOTOPE EFFECTS, FINAL STATE DISTRIBUTIONS, AND DESORPTION MECHANISMS

机译:金属表面光解氨的量子力学研究-同位素效应,最终态分布和脱附机理

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The photodesorption dynamics of ammonia from a copper surface is studied quantum mechanically using empirical potential energy surfaces. The desorption is facilitated by substrate-mediated electronic excitation and subsequent de-excitation of the adsorbate, which are simulated in our model as Franck-Condon pump and dump between two electronic states. The delayed de-excitation populates metastable predesorption states which lay above the desorption limit. The slow decay of these resonances via energy transfer from an internal mode to the desorption mode results in incomplete and rather slow desorption. The desorbed molecules have significant vibrational excitation and their translational energy distributions are highly structured, due to the dominance of the predesorption mechanism. The desorption yield depends sensitively on the time delay between the excitation and de-excitation. Strong isotope effects are observed, consistent with experimental findings. The anomalously large NH, yield relative to ND3 is attributed to its faster motion along the inversion coordinate on the excited state. (C) 1995 American Institute of Physics. [References: 76]
机译:使用经验势能表面对量子态中的氨从铜表面的光解吸动力学进行了量子力学研究。底物介导的电子激发和随后的被吸附物去激磁促进了解吸,这在我们的模型中被模拟为弗兰克-康登泵和两个电子态之间的倾卸。延迟的去激励产生高于解吸极限的亚稳态预解吸状态。通过从内部模式到解吸模式的能量转移,这些共振的缓慢衰减导致解吸不完全且相当缓慢。由于预解吸机理的优势,解吸的分子具有明显的振动激发,并且其平移能量分布具有高度结构化。解吸产率敏感地取决于激发和激发之间的时间延迟。观察到强同位素效应,与实验结果一致。相对于ND3异常大的NH收率归因于其在激发态上沿反演坐标的更快运动。 (C)1995年美国物理研究所。 [参考:76]

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