An ab initio variationally computed room-temperature line list for SO3

TL;DR

This paper presents a comprehensive, ab initio computed line list for SO3 at room temperature, enabling accurate spectral modeling and aiding atmospheric and planetary spectroscopy.

Contribution

It provides the first extensive variationally computed line list for SO3, including over 349 million transitions, with validation against experimental spectra.

Findings

Good agreement with observed infrared spectra

Line list suitable for atmospheric modeling

Provides absolute intensities for experimental transitions

Abstract

{\it Ab initio} potential energy and dipole moment surfaces are computed for sulfur trioxide (SO$_3$) at the CCSD(T)-F12b level of theory and appropriate triple-zeta basis sets. These surfaces are fitted and used, with a slight correction for the equilibrium S--O distance, to compute pure rotational and rotation-vibraton spectra of \sothree\ using the variational nuclear motion program TROVE. The calculations considered transitions in the region 0--4000 \cm\ with rotational states up to J=85. The resulting line list of 349~348~513 transitions is appropriate for modelling room temperature SO3 spectra. Good agreement is found with the observed infrared absorption spectra and the calculations are used to place the measured relative intensities on an absolute scale. A list of 10~878 experimental transitions is provided in a form suitable for inclusion in standard atmospheric and planetary spectroscopic databases.