Theoretical Studies on Many-Body Effects in Core Spectroscopies by Nonequilibrium Green 's Functions

X射线光电子衍射(XPD)谱的多体理论是在Caroli等人基本应用的Keldysh非平衡格林函数的基础上发展起来的。我们根据修饰的单电子格林函数G和屏蔽库仑相互作用W进行了骨架图展开。在光学势的影响下，衰减光电子波函数在目前的XPD理论中起着中心作用。基于目前的理论框架，我们详细讨论了有限温度下XPD谱中的德拜-沃勒因子和弗兰克-康登因子、共振效应，特别是多原子共振光电发射(MARPE)效应，以及损耗效应。XPD谱可用Franck-Condon因子和包括德拜-Waller因子的XPD强度的乘积来简单描述。这一结果与XAFS相反，在XAFS中，Franck-Condon因子被卷积抹去。我们讨论了产生显著Marpe谱的条件。尤其是对称性降低对产生显著的Marpe谱起着重要作用。角度依赖关系为我们提供了关于近邻原子排列的有用信息。一些模型计算阐明了Marpe谱的基本物理过程。为了讨论损耗谱，我们强调了本征和外在损耗之间的干扰效应的重要性。在本文的理论框架中，新导出了既包括非弹性散射又包括弹性散射的显式公式。这些公式使我们能够计算与损失相关的XPD模式。我们还发现了辐射场屏蔽对于描述共振效应的重要性，特别是Marpe。随着我们认识到量子电动力学(QED)理论，我们计划在XPS和X射线吸收光谱中包含光场效应。

Many-body theory of X-ray photoelectron diffraction(XPD) spectra is developed by using Keldysh's nonequilibrium Green's functions, which was basically applied by Caroli et al. We have applied skeleton diagram expansion in terms of dressed one-electron Green's function G and the screened Coulomb interaction W. The damping photoelectron wave functions under the influence of the optical potential play a central role of the present XPD theory. Based on the present theoretical framework, we give detailed discussion on Debye-Waller and Franck-Condon factors in XPD spectra at finite temperature, resonance effects in particular multi atom resonant photoemission(MARPE) effects, and also on the loss effects. The XPD spectra is simply described by a product of the Franck-Condon factor and the XPD intensity including the Debye-Waller factor. This result is contrast to the XAFS where the Franck-Condon factor is smeared out by a convolution product. We have discussed the conditions which give rise to prominent MARPE spectra. In particular symmetry lowering plays an important role to give rise to prominent MARPE spectra. The angular dependence provides us useful information on near neighbor atomic arrangement. Some model calculations clarify the basic physical processes of MARPE spectra. To discuss the loss spectra, we stress the importance of the interference effects between the intrinsic and extrinsic losses. The explicit formulas which include both inelastic and elastic scatterings are newly derived in the present theoretical framework. These formulas enable us to calculate XPD pattern associated with losses. We also have found the importance of the radiation field screening to describe the resonance effects in particular MARPE. As we realized the quantum electrodynamic(QED) theory, the project to include optical field effects in XPS and X-ray absorption spectra.