A Mountaineering Strategy to Excited States: Highly-Accurate Oscillator Strengths and Dipole Moments of Small Molecules

TL;DR

This paper presents highly accurate excited-state properties, including oscillator strengths and dipole moments, for small molecules using advanced coupled-cluster calculations and extensive comparisons with experimental data.

Contribution

It provides the first comprehensive high-accuracy calculations of excited-state oscillator strengths and dipole moments for thirteen small molecules, including corrections up to CCSDTQP and basis set extrapolations.

Findings

Theory agrees with experimental data within error bars when available.

Provides benchmark-quality excited-state properties for future theoretical studies.

Includes corrections up to quintuple excitations for high accuracy.

Abstract

This work presents a series of highly-accurate excited-state properties obtained using high-order coupled-cluster (CC) calculations performed with a series of diffuse containing basis sets, as well as extensive comparisons with experimental values. Indeed, we have computed both the main ground-to-excited transition property, the oscillator strength, as well as the ground- and excited-state dipole moments, considering {thirteen} small molecules (hydridoboron, hydrogen chloride, water, hydrogen sulfide, boron fluoride, carbon monoxide, dinitrogen, ethylene, formaldehyde, thioformaldehyde, nitroxyl, {fluorocarbene}, and silylidene). We systematically include corrections up to the quintuple (CCSDTQP) in the CC expansion and extrapolate to the complete basis set limit. When comparisons with experimental measurements are possible, that is, when a number of consistent experimental data can be found, theory typically provides values falling within the experimental error bar for the excited-state properties. Besides completing our previous studies focussed on transition energies (\textit{J.~Chem.~Theory Comput.} \textbf{14} (2018) 4360--4379, \textit{ibid.}~\textbf{15} (2019) 1939--1956, \textit{ibid.}~\textbf{16} (2020) 1711--1741, and \textit{ibid.}~\textbf{16} (2020) 3720--3736), this work also provides ultra-accurate dipoles and oscillator strengths that could be employed for future theoretical benchmarks.