Large-scale correlated study of excited state absorptions in naphthalene and anthracene

TL;DR

This study uses advanced theoretical methods to analyze excited state absorption spectra in naphthalene and anthracene, revealing new high-intensity features and polarization properties, with results closely matching experimental data.

Contribution

It provides a detailed theoretical analysis of excited state absorption in naphthalene and anthracene using PPP Hamiltonian and FCI, predicting new spectral features and polarization effects.

Findings

Good agreement with experimental spectra

Prediction of high-intensity spectral features

Polarization properties of PA spectrum

Abstract

In this paper, we report theoretical calculations of the photo-induced absorption (PA) spectrum of naphthalene and anthracene, with the aim of understanding those excited states, which are invisible in the linear optical absorption. The excited state absorption spectra are computed from the $1B_{2u}^{+}$ and the $1B_{3u}^{+}$ states, and a detailed analysis of the many-body character of the states contributing to various peaks in the spectra is presented. The calculations are performed using the Pariser-Parr-Pople (PPP) Hamiltonian, along with the full configuration interaction (FCI) technique. The role of Coulomb parameters used in the PPP Hamiltonian is examined by considering standard Ohno parameters, as well as a screened set of parameters. The results of our calculations are extensively compared with the experimental data where available, and very good agreement has been obtained. Moreover, our calculations predict the presence of high intensity features which, to the best of our knowledge have not been explored earlier. We also present concrete predictions on the polarization properties of the PA spectrum, which can be verified in experiments performed on oriented samples.