Isotope Effects and the Atmosphere

Abstract

Chemical physics plays a large role in determining the isotopic compositions of gases in Earth's atmosphere, which in turn provide fundamental insights into the sources, sinks, and transformations of atmospheric gases and particulates and their influence on climate. This review focuses on the kinetic and photolysis isotope effects relevant to understanding the isotope compositions of atmospheric ozone, carbon dioxide, methane, nitrous oxide, and other gases and their historical context. The discussion includes non-mass-dependent isotope compositions of oxygen-containing species and a brief overview of the recent growth of clumped isotope measurements at natural isotopic abundances, that is, of molecules containing more than one rare isotope. The intention is to introduce chemistry researchers to the field of using isotope compositions as tracers of atmospheric chemistry and climate both today and back in time through ice and rock records and to highlight the outstanding research questions to which experimental and theoretical physical chemists can contribute. Expected final online publication date for the Annual Review of Physical Chemistry, Volume 74 is April 2023. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Lifetimes and decay mechanisms of isotopically substituted ozone above the dissociation threshold: matching quantum and classical dynamics

“…As an example, such studies can provide an insight into the climate in the past, measuring isotope composition of compounds preserved in ancient terrestrial materials, ice and sediment cores. [1][2][3][4][5][6] Oxygen is one of the most abundant elements on the Earth that has three stable isotopes: 16 O, 17 O and 18 O. The origin and abundance of these isotopes could provide information on nuclear processes in nova and supernova stars: [7][8][9][10][11][12] ejected traces of stars were found in unusual isotopic abundance in several-billion-year-old meteorites.…”

“…The origin and abundance of these isotopes could provide information on nuclear processes in nova and supernova stars: [7][8][9][10][11][12] ejected traces of stars were found in unusual isotopic abundance in several-billion-year-old meteorites. 6,13 Different isotopes can react at different rates. Usually, isotope effects scale proportionally to relative mass differences, and the corresponding mass fractionation laws for the same process but involving different isotopologues are called mass-dependent 14 fractionation (MDF).…”

“…Experiments reported by the Mauersberger group 26,27,35,36 and by Janssen and coworkers 29,37,38 have provided recombination rate coefficients for various types of isotopic combinations. It is most often assumed 6,30 that isotopic anomalies occur at the first step of formation of the metastable complex in the Lindemann energy transfer mechanism,…”

“…This particularly concerns the symmetry driving effects, for which additional research is needed. 82 It is now well established [4][5][6] that the ozone MIF is not a minor and exotic phenomenon of a limited impact: its effect is photochemically transferred to many oxygen-bearing species including atmospheric CO 2 , O 2 , and water in the early solar system. 6,91,92 There is a wide area of interdisciplinary scientific fields, including atmospheric physics, geo-and cosmochemistry or climate research, 5,[93][94][95][96][97] where the ozone isotope composition, or molecular effects of isotope fractionation, plays a major role.…”

“…82 It is now well established [4][5][6] that the ozone MIF is not a minor and exotic phenomenon of a limited impact: its effect is photochemically transferred to many oxygen-bearing species including atmospheric CO 2 , O 2 , and water in the early solar system. 6,91,92 There is a wide area of interdisciplinary scientific fields, including atmospheric physics, geo-and cosmochemistry or climate research, 5,[93][94][95][96][97] where the ozone isotope composition, or molecular effects of isotope fractionation, plays a major role. [98][99][100] The state-of-the art of the MIF studies and possible impacts across various branches of science have been described in recent exhaustive reviews by Thiemens and Lin, 5 Thiemens et al, 20 Dauphas and Schauble, 4 and Carlstad and Boering, 6 who have concluded that ''The origin in chemical physics of the large, robustly measured mass-independent enrichments in ozone resulting from the three-body ozone formation reaction remains elusive and represents an intriguing chemical physics puzzle that deserves further study''.…”