The quantum yield of O(¹S) in CO₂ photolysis retrieved from the Martian atmosphere

The quantum yield of O(¹S) in CO₂ photolysis

¹ Ludwig Maximilian University, Faculty of Physics, University Observatory, Scheinerstrasse 1, Munich 81679, Germany
Corresponding author; [email protected]
² ARTORG Center for Biomedical Engineering Research, University of Bern, Murtenstrasse 50, 3008 Bern, Switzerland
³ University College London, Department of Physics & Astronomy, Gower St, London WC1E 6BT, UK
⁴ University of Warwick, Department of Physics, Astronomy & Astrophysics Group, Coventry CV4 7AL, UK

Received: 2 May 2024
Accepted: 5 September 2024

Abstract

Photochemistry studies the interactions between light and molecules. Ultraviolet radiation interacts with the atmosphere, and due to its energy, it can dissociate, excite, or ionize its constituents, which initiate other processes. A good knowledge of the interaction between photons of different energies with molecules and atoms is crucial for accurately modeling the atmospheric physics and for climate predictions. Despite its importance, photo-fragment dynamics lacks data because the experimental setup is difficult. We used the upper Martian atmosphere as a natural laboratory to measure the quantum yield O(¹S) from CO₂ + hv as a function of wavelength. We analyzed 4 years of continuous remote-sensing observations from the NASA MAVEN/IUVS spectrograph within a Bayesian framework analysis tool. We retrieved the quantum yield for the first time through its entire production spectral range, ≈80–126 nm, and achieved uncertainty from 10% to 20% on average. While at Lyman-α (121.6 nm), we achieved a precision of 2% by taking advantage of the properties of the upper Martian atmosphere.