Mechanisms of hydroxyl energy transfer in upper atmospheric nightglow

The National Science Foundation Division of Atmospheric and Geospace Sciences awarded Sri International $540,000 on April 1, 2026, under the Geosciences program (CFDA 47.050) to investigate mechanisms of hydroxyl energy transfer in Earth's upper atmospheric nightglow.

Sri International will conduct laboratory studies to determine state-specific rate coefficients for the interaction of highly vibrationally excited hydroxyl, OH(V), with ground state oxygen atoms, O(3P), focusing on vibrational-to-electronic energy transfer pathways relevant to the OH Meinel band emission near 88 kilometers altitude. This research aims to improve interpretation of remote-sensing observations that support satellite operations, navigation systems, and space weather awareness, while strengthening atmospheric models for Earth and other planets. The project includes training of postdoctoral researchers and undergraduate students.

Performance occurs at Sri International's Menlo Park, California facility through March 31, 2029. The award is classified as a Project Grant, with $540,000 obligated.

Abstract

Earth?s upper atmosphere emanates a faint luminescence known as airglow. This non-thermal radiation occurs at altitudes from about 50 to 300 KM and is initiated by solar radiation absorbed by atmospheric constituents. Light emission observed during the day is called dayglow. A plethora of photochemical processes and excitation pathways persist through the night and collectively result in emission called nightglow. The OH meinel band emission, named after american astronomer aden b. Meinel, is a prominent spectral feature of the nightglow near 88 KM. IT originates from vibrationally excited hydroxyl species produced from the reaction of hydrogen atoms with ozone. This emission has been a frequent target of ground- and space-based remote-sensing observations to study atmospheric phenomena. Despite numerous studies, there exist significant knowledge gaps regarding the mechanisms that regulate this emission. This project aims to advance fundamental understanding of these mechanisms, improving the interpretation of remote-sensing observations that support satellite operations, navigation systems, and space weather awareness, while strengthening models of earth?s atmosphere and those of other planets, and contributing to the training of postdoctoral researchers and undergraduate students. The project team will perform laboratory studies to investigate recently discovered relevant vibrational-to-electronic energy transfer pathways and determine state-specific rate coefficients for the interaction of highly vibrationally excited hydroxyl, OH(v), with ground state oxygen atoms, o(3P). This knowledge is essential for a reliable analysis and interpretation of the mesospheric OH(v) meinel band and other important nightglow emissions. This research will advance our knowledge of the processes responsible for molecular energy transfer on a fundamental level and may also be relevant for combustion, astrophysical environments, and the operation of high-power chemical lasers. A detailed knowledge of airglow processes is also critical for space weather monitoring, situational space awareness, as well as defense and dual-use technologies. Airglow emissions, especially in the infrared region of the electromagnetic spectrum, for which emission from the ground is absorbed by the atmosphere, lend themselves favorably for surveillance above the atmosphere by high-altitude reconnaissance satellites. The results of this research will contribute to improved subtraction of spatial clutter from atmospheric background emissions in applications such as observation and tracking of midcourse objects by reconnaissance satellites. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the foundation's intellectual merit and broader impacts review criteria.- subawards are not planned for this award.