Complete insensitivity to ab initio data -- A new perspective on modeling collision-induced absorption of noble gas atoms

TL;DR

This paper demonstrates that collision-induced absorption spectra are remarkably insensitive to the quality of ab initio data, revealing new spectral features and emphasizing the importance of short-range interactions in modeling.

Contribution

It shows that even low-level ab initio calculations yield accurate CIA spectra and uncovers a new double-peak structure for He-Ne complexes, challenging existing models.

Findings

CIA spectra are accurate within 10% even with low-level calculations.

A new double-peak structure for He-Ne complex is reported.

Short-range interactions dominate at high temperatures.

Abstract

In this study, we systematically investigate how the accuracy of CIA spectra depends on the quality of the ab initio data used. We evaluate quantitatively the impact of different quantum chemical methods and basis sets on spectral features, finding that even the lowest-level calculations are accurate to approximately 10 % at room temperature, and better at higher temperatures. This study also reveals a previously unreported double-peak structure for the He-Ne complex, which cannot be described by simple but commonly used single-exponential models for the short-range dipole. Our analysis shows that the range of internuclear distances relevant for CIA spectra varies with temperature, with short-range interactions becoming increasingly important at high temperatures. The long-range van der Waals induced dipoles never contribute. These findings provide new insights into the temperature-dependent behavior of CIA spectra and emphasize the importance of accurate modeling of short-range interactions for reliable astronomical modeling.