Knowledge Gaps in the Cometary Spectra of Oxygen-Bearing Molecular Cations

TL;DR

This paper reviews the spectral data gaps for oxygen-bearing molecular cations in cometary atmospheres, emphasizing the need for comprehensive data to improve models of cometary spectra and understand comet evolution.

Contribution

It compiles existing spectral data for key oxygen-containing molecular cations and identifies critical gaps for future research to enhance spectral modeling accuracy.

Findings

Spectral data are incomplete for several key molecular cations.

Data gaps hinder accurate modeling of cometary spectra.

Addressing these gaps will improve understanding of cometary processes.

Abstract

Molecular cations are present in various astronomical environments, most notably in cometary atmospheres and tails where sunlight produces exceptionally bright near-UV to visible transitions. Such cations typically have longer-wavelength and brighter electronic emission than their corresponding neutrals. A robust understanding of their near-UV to visible properties would allow these cations to be used as tools for probing the local plasma environments or as tracers of neutral gas in cometary environments. However, full spectral models are not possible for characterization of small, oxygen containing molecular cations given the body of molecular data currently available. The five simplest such species (H2O+, CO+2 , CO+, OH+, and O+2 ) are well characterized in some spectral regions but are lacking robust reference data in others. Such knowledge gaps hinder fully quantitative models of cometary spectra, specifically, hindering accurate estimates of physical-chemical processes originating with the most common molecules in comets. Herein the existing spectral data are collected for these molecules and highlight the places where future work is needed, specifically where the lack of such data would greatly enhance the understanding of cometary evolution.