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First detection of the atomic O18 isotope in the mesosphere and lower thermosphere of Earth

Hübers, Heinz-Wilhelm and Richter, Heiko and Wiesemeyer, Helmut and Güsten, Rolf and Aladro, Rebeca and Klein, Bernd and Graf, Urs U. and Justen, Matthias and Okada, Yoko and Stutzki, Jürgen (2023) First detection of the atomic O18 isotope in the mesosphere and lower thermosphere of Earth. Physical Review Research, pp. 1-19. American Physical Society. doi: 10.1103/PhysRevResearch.5.013072. ISSN 2643-1564.

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In the lower atmosphere of Earth, oxygen contains a higher fraction of the heavy O18 isotope than ocean water does (Dole effect). This isotopic enrichment is a signature of biological activity, set by the equilibrium between oxygenic photosynthesis and respiratory metabolisms in terrestrial and oceanic ecosystems. While the mixing between stratospheric and tropospheric oxygen leads to a slow isotopic homogenization, little is known about the isotopic oxygen enrichment in the mesosphere and thermosphere of Earth. In situ measurements from rocket-borne air samplers are limited to altitudes below the mesopause, while higher layers have only been accessible through the analysis of the oxidation of ancient cosmic spherules. Here we report the detection of the far-infrared fine-structure lines (3P1<-3P2 and 3P0<-3P1) of O18 in absorption against the Moon, and determine the O16/O18 ratio in atomic oxygen from the mesosphere and lower thermosphere in absorption. After correcting for isotopic exchange between atomic and molecular oxygen, our values for the bulk O16/O18 ratio of 468 and 382 in February and November 2021, respectively, fall significantly below that found in solar wind samples (530±2), and encompass, within uncertainties, the corresponding ratios pertaining to the Dole effect in the troposphere (487), and those found in stratospheric ozone (429 to 466). We show that with existing technology, future, more sensitive measurements will allow us to monitor deviations from isotopic homogeneity in the mesosphere and lower thermosphere of Earth by remote sensing. We demonstrate that the collisional excitation of the fine-structure levels of the P3 ground-state triplet of O18 may compete with isotopic exchange reactions, implying a deviation from the Boltzmann distribution that would be established under local thermodynamic equilibrium.

Item URL in elib:https://elib.dlr.de/198441/
Document Type:Article
Title:First detection of the atomic O18 isotope in the mesosphere and lower thermosphere of Earth
AuthorsInstitution or Email of AuthorsAuthor's ORCID iDORCID Put Code
Hübers, Heinz-WilhelmGerman Aerospace Center (DLR)UNSPECIFIEDUNSPECIFIED
Richter, HeikoGerman Aerospace Center (DLR)UNSPECIFIEDUNSPECIFIED
Wiesemeyer, HelmutMax-Planck-Institut für RadiostromaticUNSPECIFIEDUNSPECIFIED
Güsten, RolfMax-Planck-Institut für RadiostromaticUNSPECIFIEDUNSPECIFIED
Aladro, RebecaMax-Planck-Institut für RadiostromaticUNSPECIFIEDUNSPECIFIED
Klein, BerndMax-Planck-Institut für RadiostromaticUNSPECIFIEDUNSPECIFIED
Graf, Urs U.I. Physikalisches Institut, Universität zu KölnUNSPECIFIEDUNSPECIFIED
Justen, MatthiasI. Physikalisches Institut, Universität zu KölnUNSPECIFIEDUNSPECIFIED
Okada, YokoI. Physikalisches Institut, Universität zu KölnUNSPECIFIEDUNSPECIFIED
Stutzki, JürgenI. Physikalisches Institut, Universität zu KölnUNSPECIFIEDUNSPECIFIED
Date:1 February 2023
Journal or Publication Title:Physical Review Research
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In ISI Web of Science:Yes
Page Range:pp. 1-19
Publisher:American Physical Society
Keywords:Terahertz, Sauerstoff, Atmosphäre, SOFIA, Isotop, oxygen, atmosphere, isotope
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Earth Observation
DLR - Research theme (Project):R - Terahertz spectrometer for atomic oxygen in the mesosphere/thermosphere
Location: Berlin-Adlershof
Institutes and Institutions:Institute of Optical Sensor Systems > Terahertz and Laser Spectroscopy
Deposited By: Frohmann, Sven
Deposited On:24 Oct 2023 08:52
Last Modified:04 Apr 2024 15:07

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