Time-dependent coupled cluster theory for ultrafast transient absorption spectroscopy

TL;DR

This paper develops a spin-adapted time-dependent coupled cluster method to simulate ultrafast transient absorption spectra, capturing electronic dynamics induced by laser pulses with a focus on balancing accuracy and computational efficiency.

Contribution

It introduces a novel spin-adapted time-dependent coupled cluster model for ultrafast spectroscopy, enabling detailed simulations of electronic responses to laser pulse sequences.

Findings

Transient absorption oscillates with pump-probe delay.

Interference of states causes oscillations in the spectrum.

Method achieves a balance between computational cost and accuracy.

Abstract

We present a spin-adapted time-dependent coupled cluster singles and doubles model for the molecular response to a sequence of ultrashort laser pulses. The implementation is used to calculate the electronic response to a valence-exciting pump pulse, and a subsequent core-exciting probe pulse. We assess the accuracy of the integration procedures used in solving the dynamic coupled cluster equations, in order to find a compromise between computational cost and accuracy. The transient absorption spectrum of lithium fluoride is calculated for various delays of the probe pulse with respect to the pump pulse. We observe that the transient probe absorption oscillates with the pump-probe delay, an effect that is attributed to the interference of states in the pump-induced superposition.