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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Stable Stoichiometry of Gas-Phase Manganese Oxide Cluster Ions Revealed by Temperature-Programmed Desorption
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Stable Stoichiometry of Gas-Phase Manganese Oxide Cluster Ions Revealed by Temperature-Programmed Desorption

机译：程序升温解吸揭示气相锰氧化物簇离子的稳定化学计量

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摘要

Temperature-programmed desorption (TPD) experiments were performed on gas-phase manganese oxide cluster ions, namely, MnnOm+ (n = 3-20) and MnnOm- (n = 3-18). These cluster ions were prepared by laser ablation of a manganese rod in the presence of oxygen gas, and their composition was investigated using mass spectrometry. The composition of MnnOm +/- distribution lies above the m = (4/3)(n) line. When the cluster ions were heated to 1000 K, Mn(n)Om(+) (m = (4/3)n + delta, with d = -1, 0) and Mn(n)Om (m = (4/3)n + delta, with d = 0, 1) was found to be the predominant species, formed by thermal dissociation. These experimental findings indicate that the nascent manganese oxide clusters comprise robust MnnOm +/- (m approximate to 4/3) and weakly bound excess oxygen atoms. On the basis of the TPD experiments, the oxygen-molecule release was identified as the main dissociation channel. The temperature dependence of O-2 desorption was found to be similar among the clusters with the same oxygen excess or deficiency regardless of the number of Mn atoms. The threshold energy of O-2 desorption was estimated for Mn4Om+ (m = 6-11) and compared with bond dissociation energies calculated by density functional theory.
机译：对气相氧化锰簇离子MnnOm +（n = 3-20）和MnnOm-（n = 3-18）进行了程序升温脱附（TPD）实验。这些簇离子是在氧气存在下通过激光烧蚀锰棒制备的，其组成采用质谱法进行了研究。 MnnOm +/-分布的组成位于m =（4/3）（n）线上方。当簇离子加热到1000 K时，Mn（n）Om（+）（m =（4/3）n +δ，d = -1，0）和Mn（n）Om（m =（4 /发现3）n +δ，其中d = 0，1）是通过热分解形成的主要物种。这些实验结果表明，新生的氧化锰簇包含健壮的MnnOm +/-（m / n约为4/3）和弱结合的过量氧原子。在TPD实验的基础上，氧分子的释放被确定为主要的离解通道。发现在氧过量或缺乏的相同簇之间，O-2解吸的温度依赖性相似，而与Mn原子数无关。估计了Mn4Om +（m = 6-11）的O-2解吸阈值能量，并将其与通过密度泛函理论计算的键解离能进行了比较。

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