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Somogyi W, Yurchenko SN, Yachmenev A. Calculation of electric quadrupole linestrengths for diatomic molecules: Application to the H 2, CO, HF, and O 2 molecules. J Chem Phys 2021; 155:214303. [PMID: 34879671 DOI: 10.1063/5.0063256] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
We present a unified variational treatment of the electric quadrupole (E2) matrix elements, Einstein coefficients, and linestrengths for general open-shell diatomic molecules in the general purpose diatomic code Duo. Transformation relations between the Cartesian representation (typically used in electronic structure calculations) to the tensorial representation (required for spectroscopic applications) of the electric quadrupole moment components are derived. The implementation has been validated against accurate theoretical calculations and experimental measurements of quadrupole intensities of 1H2 available in the literature. We also present accurate electronic structure calculations of the electric quadrupole moment functions for the X1Σ+ electronic states of CO and HF, as well as for the a1Δg-b1Σg + quadrupole transition moment of O2 with the MRCI level of theory. Accurate infrared E2 line lists for 12C16O and 1H19F are provided. A demonstration of spectroscopic applications is presented by simulating E2 spectra for 12C16O, H19F, and 16O2 (Noxon a1Δg-b1Σg + band).
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Affiliation(s)
- W Somogyi
- Department of Physics and Astronomy, University College London, Gower Street, WC1E 6BT London, United Kingdom
| | - S N Yurchenko
- Department of Physics and Astronomy, University College London, Gower Street, WC1E 6BT London, United Kingdom
| | - A Yachmenev
- Center for Free-Electron Laser Science CFEL, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, 22607 Hamburg, Germany and Center for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, 22761 Hamburg, Germany
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Gebauer S, Grenfell JL, Lammer H, de Vera JPP, Sproß L, Airapetian VS, Sinnhuber M, Rauer H. Atmospheric Nitrogen When Life Evolved on Earth. ASTROBIOLOGY 2020; 20:1413-1426. [PMID: 33121251 DOI: 10.1089/ast.2019.2212] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The amount of nitrogen (N2) present in the atmosphere when life evolved on our planet is central for understanding the production of prebiotic molecules and, hence, is a fundamental quantity to constrain. Estimates of atmospheric molecular nitrogen partial surface pressures during the Archean, however, widely vary in the literature. In this study, we apply a model that combines newly gained insights into atmospheric escape, magma ocean duration, and outgassing evolution. Results suggest <420 mbar surface molecular nitrogen at the time when life originated, which is much lower compared with estimates in previous works and hence could impact our understanding of the production rate of prebiotic molecules such as hydrogen cyanide. Our revised values provide new input for atmospheric chamber experiments that simulate prebiotic chemistry on the early Earth. Our results that assume negligible nitrogen escape rates are in agreement with research based on solidified gas bubbles and the oxidation of iron in micrometeorites at 2.7 Gyr ago, which suggest that the atmospheric pressure was probably less than half the present-day value. Our results contradict previous studies that assume N2 partial surface pressures during the Archean were higher than those observed today and suggest that, if the N2 partial pressure were low in the Archean, it would likely be low in the Hadean as well. Furthermore, our results imply a biogenic nitrogen fixation rate from 9 to 14 Teragram N2 per year (Tg N2/year), which is consistent with modern marine biofixation rates and, hence, indicate an oceanic origin of this fixation process.
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Affiliation(s)
- Stefanie Gebauer
- Institute for Planetary Research (PF), German Aerospace Centre (DLR), Berlin, Germany
| | - John Lee Grenfell
- Institute for Planetary Research (PF), German Aerospace Centre (DLR), Berlin, Germany
| | - Helmut Lammer
- Space Research Institute, Austrian Academy of Sciences, Graz, Austria
| | | | - Laurenz Sproß
- Space Research Institute, Austrian Academy of Sciences, Graz, Austria
- Institute for Physics, University of Graz, Graz, Austria
| | - Vladimir S Airapetian
- NASA Goddard Space Flight Center (GSFC), Greenbelt, Maryland, USA
- American University, NW Washington, District of Columbia, USA
| | - Miriam Sinnhuber
- Institute for Meteorology and Climate Research, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
| | - Heike Rauer
- Institute for Planetary Research (PF), German Aerospace Centre (DLR), Berlin, Germany
- Institute for Geological Sciences, Planetology and Remote Sensing, Freie Universität Berlin (FUB), Berlin, Germany
- Centre for Astronomy and Astrophysics, Technische Universität Berlin (TUB), Berlin, Germany
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Haqq-Misra J, Kopparapu RK, Schwieterman E. Observational Constraints on the Great Filter. ASTROBIOLOGY 2020; 20:572-579. [PMID: 32364797 DOI: 10.1089/ast.2019.2154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The search for spectroscopic biosignatures with the next generation of space telescopes could provide observational constraints on the abundance of exoplanets with signs of life. An extension of this spectroscopic characterization of exoplanets is the search for observational evidence of technology, known as technosignatures. Current mission concepts that would observe biosignatures from ultraviolet to near-infrared wavelengths could place upper limits on the fraction of planets in the Galaxy that host life, although such missions tend to have relatively limited capabilities of constraining the prevalence of technosignatures at mid-infrared wavelengths. Yet searching for technosignatures alongside biosignatures would provide important knowledge about the future of our civilization. If planets with technosignatures are abundant, then we can increase our confidence that the hardest step in planetary evolution-the Great Filter-is probably in our past. But if we find that life is commonplace while technosignatures are absent, then this would increase the likelihood that the Great Filter awaits to challenge us in the future.
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Affiliation(s)
| | | | - Edward Schwieterman
- Blue Marble Space Institute of Science, Seattle, Washington
- University of California at Riverside, Riverside, California
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