Simulating weak-field attosecond processes with a Lanczos reduced basis approach to time-dependent equation of motion coupled cluster theory

TL;DR

This paper introduces a computationally efficient TD-EOM-CCSD method using a Lanczos reduced basis to simulate weak-field attosecond processes, accurately reproducing spectra with lower computational cost.

Contribution

The paper presents a novel implementation of TD-EOM-CCSD with a Lanczos-based reduced basis, enabling faster simulations of ultrafast molecular processes.

Findings

Spectral features are accurately reproduced for several molecules.

The method significantly reduces computational time compared to traditional approaches.

Transient absorption of attosecond X-ray pulses in glycine is successfully modeled.

Abstract

A time-dependent equation of motion coupled cluster singles and doubles (TD-EOM-CCSD) method is implemented, which uses a reduced basis calculated with the asymmetric band Lanczos algorithm. The approach is used to study weak-field processes in small molecules induced by ultrashort valence pump and core probe pulses. We assess the reliability of the procedure by comparing TD-EOM-CCSD absorption spectra to spectra obtained from the time-dependent coupled-cluster singles and doubles (TDCCSD) method and observe that spectral features can be reproduced for several molecules, at much lower computational times. We discuss how multiphoton absorption and symmetry can be handled in the method and general features of the core-valence separation (CVS) projection technique. We also model the transient absorption of an attosecond X-ray probe pulse by the glycine molecule.