Angular distribution parameter as a function of photon energy for some mono- and diazabenzenes and its use for orbital assignment
Angular distribution parameter as a function of photon energy for some mono- and diazabenzenes and its use for orbital assignment
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DOI：
10.1021/ja00351a019
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发表时间：
1983-06
影响因子：
15
通讯作者：
M. Piancastelli;P. R. Keller;James W. Taylor;F. A. Grimm;T. A. Carlson
中科院分区：
文献类型：
--
作者：
M. Piancastelli;P. R. Keller;James W. Taylor;F. A. Grimm;T. A. Carlson
用同步辐射作为电离源，获得了一系列含氮芳香族体系的角分辨光电子能谱。在12-27 eV的光子能量范围内，测量了2-氟吡啶、五氟吡啶和吡啶的前三个轨道以及嘧啶和吡嗪的前四个轨道的角分布参数。角分布参数作为光子能量的函数在光电子能谱中具有指认价值，并已应用于吡啶的光电子能谱。含氟取代的吡啶类化合物提供了关于..β的趋势的信息。具有主要氮孤对特征的非键轨道的值。二氮类药物证明了..贝塔..即使在部分频带重叠的情况下，作为光子能量函数的值也可以用于轨道分配。对于吡啶，前两个离子能级的重叠，由一个..pi组成。和一个非键轨道，是如此严重，以至于明确的分配一直是困难的，但现在是可能的。实验证据表明，在较低的电离能下，这些能级的顺序是非键(N)轨道，紧随其后的是…pi。轨道。系统地研究了同系物分子的角度分辨光电子能谱与光子能量的关系。
Angle-resolved photoelectron spectra were obtained on a series of nitrogen-containing aromatic systems using synchrotron radiation as the ionizing source. The angular distribution parameter, ..beta.., was measured in the photon energy range 12-27eV for the first three orbitals of 2-fluoropyridine, pentafluoropyridine, and pyridine, and for the first four orbitals of pyrimidine and pyrazine. The angular distribution parameter as a function of photon energy is shown to be of value in the assignment of bands in photoelectron spectra and has been applied to the photoelectron spectra of pyridine. The fluoro-substituted pyridines provided information on the trend of the ..beta.. values for nonbonding orbitals with predominant nitrogen lone-pair character. The diazines demonstrated that ..beta.. values as a function of photon energy could be used for orbital assignments even in the case of partial band overlap. For pyridine the overlap of the first two ionic levels, consisting of a ..pi.. and a nonbonding orbital, is so severe that unambiguous assignment has been difficult but is now possible. Experimental evidence is presented for the sequence of these levels to be the nonbonding (n) orbital at lower ionization energy followed by the ..pi.. orbital. The relevance of systematic investigations of the angle-resolved photoelectron spectroscopy of amore » homologous series of molecules as a function of photon energy is discussed.« less