Perturbative-polarization-propagator study of the photoionization cross section of the water molecule.
Perturbative-polarization-propagator study of the photoionization cross section of the water molecule.
复制标题
水分子光电离截面的微扰偏振传播器研究。
DOI：
10.1103/physreva.40.696
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Diercksen
中科院分区：
文献类型：
--
作者：
Müller;Diercksen
采用大高斯基组的不同阶数的微扰偏振传播算子方法被用来计算水分子振子强度分布的离散赝态表示，然后由矩理论方法确定连续的总和部分光电离截面。在一阶和二阶极化传播近似下得到的截面与最近的光电离测量结果非常吻合。特别是，目前的结果同意更好地与实验比以前的计算，使用静态交换近似。其主要原因是一阶和高阶极化传播近似服从振子强度分布的某些求和规则，而静态交换近似则不服从。这使得传播子方法特别适合与矩理论结合使用。以前报道的水分子截面与实验不一致，如高估了1${B}_{2}$部分截面，部分归因于在这些计算中忽略了通道耦合。因此，在本工作中，分离通道近似是避免和所有可能的耦合电离之间的所有价壳层分子轨道。
Perturbative-polarization-propagator methods of different orders employing large Gaussian basis sets are used to calculate discrete pseudostate representations of the oscillator strength distribution of the water molecule, from which continuous total and partial photoionization cross sections are then determined by moment-theoretical methods. The cross sections obtained in the first-order and second-order polarization-propagator approximation are in very good agreement with recent photoionization measurements. In particular, the present results agree much better with experiment than previous calculations that use the static-exchange approximation. The main reason for this is that first- and higher-order polarization-propagator approximations obey certain sum rules for the oscillator strength distribution, whereas the static-exchange approximation does not. This makes propagator methods particularly well suited for use in connection with moment theory. Disagreement of previously reported cross sections of the water molecule with experiment, such as the overestimation of the 1${b}_{2}$ partial cross section, have been partially attributed to the neglect of channel coupling in these calculations. Therefore, in the present work, the separated-channel approximation is avoided and all possible couplings between ionizations from all valence-shell molecular orbitals are allowed for.