Laboratory Studies Relevant to the Coupled OH Meinel and O2 Atmospheric Band Emissions

The hydroxyl radical plays an important role in the photochemistry of the Earth's mesosphere. The OH Meinel band emission dominates the visible and near-infrared portion of the nightglow spectrum. A detailed knowledge of the rate constants and relevant pathways for OH(high v) vibrational relaxation by atomic and molecular oxygen is essential for understanding mesospheric OH emissions and extracting reliable chemical heating rates from atmospheric observations. We have developed laser-based experimental methodologies to study the complex collisional energy transfer processes involving the OH radical and other relevant atmospheric species. Our previous studies have indicated that the total removal rate constant for OH(v = 9) by atomic oxygen at room temperature is more than one order of magnitude larger than that for removal by molecular oxygen. Thus, O atoms are expected to significantly influence the intensity and vibrational distribution extracted from the mesospheric OH(v) Meinel band emissions. This is a progress report on our experimental studies investigating OH(v ≥ 5) + O vibrational relaxation and the implications for mesospheric nightglow.

This work is supported by the NASA Heliophysics Program under Grant 80NSSC23K0694 and the National Science Foundation (NSF) under Grants AGS-2009960 and AGS-2113888.