We describe a real-time, equation of motion coupled cluster (RT-EOM-CC) Green’s function approach for calculations of multi-electronic excitations including shake-up effects and orthogonality effects in core level x-ray absorption spectra (XAS) [1]. The method is based on a factorization of the transition amplitude in the time-domain, which leads to a convolution of the core-hole spectral function and an effective one-body x-ray spectrum. The real-time EOM-CC equations yield an exact cumulant representation of the core-hole Green’s function, with a cumulant that builds in non-linear corrections. Peaks in the spectral function correspond to intrinsic inelastic losses or shake-up satellites in x-ray spectra. The RT-EOM-CC equations yield non-perturbative expression for the cumulant in terms of the solution to a set of non-linear, first order differential equations. The one-body x-ray spectrum also includes orthogonality corrections that enhance the XAS at the edge analogous to those in the x-ray edge singularity effect. We also find that the method yields accurate binding energies and satellite spectra compared to experiment [2]. A recent review is given in [3].

Real-time EOM-CC cumulant Green’s function approach for multi-electron excitations in x-ray spectra

ACS Spring 2022

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