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

In this study, we systematically investigate how the accuracy of collision-induced absorption (CIA) spectra of noble gas atom pairs 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 in this study 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 Ne–He complex, which cannot be described by simple and 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. • We quantified the sensitivity of CIA spectra to the quality of ab initio PES and IDS. • The absorption spectra of noble gas mixtures aren’t sensitive to long-range vdW interactions. • The spectra are more sensitive to IDS than to PES. • This sensitivity of the spectra decreases with incresing temperature. • We find the absorption can be attributed to a narrow range of internuclear distances. • Short range becomes increasingly important at elevated temperatures.