{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,10]],"date-time":"2026-06-10T16:14:34Z","timestamp":1781108074104,"version":"3.54.1"},"reference-count":49,"publisher":"National Academy of Sciences","issue":"29","license":[{"start":{"date-parts":[[2025,7,16]],"date-time":"2025-07-16T00:00:00Z","timestamp":1752624000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"funder":[{"name":"BSF-NSF","award":["2019722"],"award-info":[{"award-number":["2019722"]}]},{"name":"FNRS | Fonds pour la Formation \u00e0 la Recherche","award":["T0205.20"],"award-info":[{"award-number":["T0205.20"]}]},{"DOI":"10.13039\/100006132","name":"DOE office of Science","doi-asserted-by":"crossref","award":["DE-AC02-05CH11231"],"award-info":[{"award-number":["DE-AC02-05CH11231"]}],"id":[{"id":"10.13039\/100006132","id-type":"DOI","asserted-by":"crossref"}]},{"name":"NSF-BSF","award":["2009959"],"award-info":[{"award-number":["2009959"]}]}],"content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[2025,7,22]]},"abstract":"<jats:p>\n                    Stable isotope ratio measurements provide valuable insights into a broad range of natural processes, from planetary atmospheres and climate to interstellar chemistry. Nitrogen, which has two stable isotopes, exhibits varying isotope ratios across the solar system. To model these observations, the isotope fraction as a function of energy is essential. At the Advanced Light Source (ALS), we measured the photodissociation of molecular nitrogen (N\n                    <jats:sub>2<\/jats:sub>\n                    ) with vacuum UV photons where a single photon is sufficiently energetic to dissociate the strong bond. The nitrogen atoms produced are scavenged with H\n                    <jats:sub>2<\/jats:sub>\n                    to form ammonia, whose isotopic makeup is determined. Blending the experiments with dynamical computations that include the shielding of light, we examine the isotopic composition and electronic atomic states produced. The measured photodissociation of N\n                    <jats:sub>2<\/jats:sub>\n                    at a natural isotopic composition with a frequency broad light beam exceptionally strongly favors the formation of the heavier nitrogen isotope,\n                    <jats:sup>15<\/jats:sup>\n                    N. Computations concur and suggest that the maximum in the quantum yield reflects significant variations in the specific electronic quantum states of the product N atoms that have quite different reactivities. Our quantum computations show that at similar energies, photodissociation of\n                    <jats:sup>14<\/jats:sup>\n                    N\n                    <jats:sup>14<\/jats:sup>\n                    N and\n                    <jats:sup>15<\/jats:sup>\n                    N\n                    <jats:sup>14<\/jats:sup>\n                    N can lead to different product channels. The computed dynamics include extensive state-selective spin\u2013orbit and nonadiabatic couplings affecting the light absorption and dissociation pathways that proceed via the triplet manifold of states. Our results are relevant for future exploration missions, both in situ and sample-return and for other molecules such as O\n                    <jats:sub>2<\/jats:sub>\n                    and CO.\n                  <\/jats:p>","DOI":"10.1073\/pnas.2511172122","type":"journal-article","created":{"date-parts":[[2025,7,16]],"date-time":"2025-07-16T17:41:47Z","timestamp":1752687707000},"update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":0,"title":["Photoselective isotope fractionation dynamics of N\n                    <sub>2<\/sub>\n                    with cosmo and atmospheric chemistry perspectives"],"prefix":"10.1073","volume":"122","author":[{"given":"Ksenia","family":"Komarova","sequence":"first","affiliation":[{"name":"The Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem","place":["Jerusalem, Israel"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Natalia A.","family":"Gelfand","sequence":"additional","affiliation":[{"name":"The Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem","place":["Jerusalem, Israel"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Francoise","family":"Remacle","sequence":"additional","affiliation":[{"name":"The Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem","place":["Jerusalem, Israel"]},{"name":"Theoretical Physical Chemistry, Research Unit Molecular Systems B6c, University of Li\u00e8ge","place":["Li\u00e8ge, Belgium"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1973-8449","authenticated-orcid":false,"given":"Raphael D.","family":"Levine","sequence":"additional","affiliation":[{"name":"The Fritz Haber Center for Molecular Dynamics, Institute of Chemistry, The Hebrew University of Jerusalem","place":["Jerusalem, Israel"]},{"name":"Department of Molecular and Medical Pharmacology, David Geffen School of Medicine, University of California","place":["Los Angeles"]},{"name":"Department of Chemistry and Biochemistry, University of California","place":["Los Angeles"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Subrata","family":"Chakraborty","sequence":"additional","affiliation":[{"name":"Department of Chemistry and Biochemistry, University of California","place":["La Jolla"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Teresa L.","family":"Jackson","sequence":"additional","affiliation":[{"name":"Department of Chemistry and Biochemistry, University of California","place":["La Jolla"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Oleg","family":"Kostko","sequence":"additional","affiliation":[{"name":"Chemical Sciences Division, Lawrence Berkeley National Laboratory","place":["Berkeley"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-1822-6070","authenticated-orcid":false,"given":"Mark H.","family":"Thiemens","sequence":"additional","affiliation":[{"name":"Department of Chemistry and Biochemistry, University of California","place":["La Jolla"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[2025,7,16]]},"reference":[{"key":"e_1_3_4_1_2","doi-asserted-by":"publisher","DOI":"10.1002\/anie.201812322"},{"key":"e_1_3_4_2_2","first-page":"35","volume-title":"Triple Oxygen Isotope Geochemistry","author":"Thiemens M. 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