# Two-dimensional Fano lineshapes: Excited-state absorption contributions

## TL;DR

This paper investigates how excited-state absorption influences two-dimensional Fano lineshapes in nanostructures, revealing complex lineshape distortions and clarifying the role of many-body interactions in spectroscopic signatures.

## Contribution

It provides a detailed calculation of excited-state absorption contributions in 2D spectroscopy, highlighting the effects of higher-lying excited states and clarifying the nature of Fano lineshapes.

## Key findings

- Asymmetry in 1D spectroscopies is recovered from many-body effects.
- Higher-lying excited states cause distorted lineshapes not predicted by simple models.
- SE contributions cannot originate from a flat continuum of states.

## Abstract

Fano interferences in nanostructures are influenced by dissipation effects as well as many-body interactions. Two dimensional coherent spectroscopies have just begun to be applied to these systems where the spectroscopic signatures of a discrete-continuum structure are not known. In this article we calculate the excited-state absorption contribution for different models of higher-lying excited states. We find that the characteristic asymmetry of one-dimensional spectroscopies is recovered from the many-body contributions, and that the higher-lying excited manifolds have distorted lineshapes that are not anticipated from discrete-level Hamiltonians. We show that the SE cannot have contributions from a flat continuum of states. This work completes the Ground-State Bleach and Stimulated Emission signals that were calculated previously (Phys. Rev. B. 2016, 94, 205137). The model reproduces the observations reported for molecules on surfaces probed by 2DIR.