{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T17:08:09Z","timestamp":1790096889234,"version":"4.0.1"},"reference-count":47,"publisher":"National Academy of Sciences","issue":"39","license":[{"start":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T00:00:00Z","timestamp":1790035200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by-nc-nd\/4.0\/"}],"funder":[{"DOI":"10.13039\/100020595","name":"National Science and Technology Council","doi-asserted-by":"publisher","award":["113-2628-M-001-006-MY3; 114-2923-M-001-001-MY4; 114-2927-I-001-524; 114-2639-M-A49-002-ASP"],"award-info":[{"award-number":["113-2628-M-001-006-MY3; 114-2923-M-001-001-MY4; 114-2927-I-001-524; 114-2639-M-A49-002-ASP"]}],"id":[{"id":"10.13039\/100020595","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100001869","name":"Academia Sinica","doi-asserted-by":"publisher","award":["AS-CDA-114-M05"],"award-info":[{"award-number":["AS-CDA-114-M05"]}],"id":[{"id":"10.13039\/501100001869","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/100016270","name":"Global Challenges Research Fund","doi-asserted-by":"publisher","award":["NERC SANH project (NE\/S009019\/1) and NERC HECTER project (NE\/X0102036\/1)"],"award-info":[{"award-number":["NERC SANH project (NE\/S009019\/1) and NERC HECTER project (NE\/X0102036\/1)"]}],"id":[{"id":"10.13039\/100016270","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":["www.pnas.org"],"crossmark-restriction":true},"short-container-title":["Proc. Natl. Acad. Sci. U.S.A."],"published-print":{"date-parts":[[2026,9,29]]},"abstract":"<jats:p>\n                    The hydroperoxy radical (HO\n                    <jats:sub>2<\/jats:sub>\n                    ) self-reaction is an important radical termination pathway under low-NO tropospheric conditions and a major gas-phase source of hydrogen peroxide (H\n                    <jats:sub>2<\/jats:sub>\n                    O\n                    <jats:sub>2<\/jats:sub>\n                    ), a key oxidant reservoir. Here we determine HO\n                    <jats:sub>2<\/jats:sub>\n                    self-reaction kinetics across atmospherically relevant temperatures and pressures and over a range of water vapor and methanol concentrations, using a collinear photolysis\u2013probe geometry with cross-validated ultraviolet and mid-infrared absorption. The resulting rate coefficients are consistently higher than current NASA\/JPL recommendations, by ~50% under humid boundary-layer conditions and by up to a factor of two under upper-tropospheric conditions, owing primarily to revised pressure-dependent and water-enhanced contributions. Relative to NASA\/JPL, implementation of the updated HO\n                    <jats:sub>2<\/jats:sub>\n                    self-reaction kinetics in the global chemistry\u2013transport model STOCHEM-CRI decreases modeled near-surface HO\n                    <jats:sub>2<\/jats:sub>\n                    by up to 12% (1.5 ppt) and increases H\n                    <jats:sub>2<\/jats:sub>\n                    O\n                    <jats:sub>2<\/jats:sub>\n                    by up to 28% (900 ppt). The largest OH response occurs in the upper troposphere, where OH increases by up to 8%. This work provides a comprehensive experimental basis for parameterizing HO\n                    <jats:sub>2<\/jats:sub>\n                    self-reaction kinetics in modeling tropospheric HO\n                    <jats:italic toggle=\"yes\">\n                      <jats:sub>x<\/jats:sub>\n                    <\/jats:italic>\n                    and H\n                    <jats:sub>2<\/jats:sub>\n                    O\n                    <jats:sub>2<\/jats:sub>\n                    , while also supporting further studies of HO\n                    <jats:sub>2<\/jats:sub>\n                    -driven radical chemistry.\n                  <\/jats:p>","DOI":"10.1073\/pnas.2606852123","type":"journal-article","created":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T16:12:31Z","timestamp":1790093551000},"update-policy":"https:\/\/doi.org\/10.1073\/pnas.cm10313","source":"Crossref","is-referenced-by-count":0,"title":["Collinear UV\u2013mid-IR cross-validation updates HO\n                    <sub>2<\/sub>\n                    self-reaction kinetics and implications for tropospheric HO\n                    <i>\n                      <sub>x<\/sub>\n                    <\/i>\n                    and H\n                    <sub>2<\/sub>\n                    O\n                    <sub>2<\/sub>"],"prefix":"10.1073","volume":"123","author":[{"given":"I.-Yun","family":"Chen","sequence":"first","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03haqsp75","id-type":"ROR","asserted-by":"publisher"}],"name":"Institute of Atomic and Molecular Sciences, Academia Sinica","place":["Taipei, Taiwan"]},{"id":[{"id":"https:\/\/ror.org\/05bqach95","id-type":"ROR","asserted-by":"publisher"}],"name":"Department of Chemistry, National Taiwan University","place":["Taipei, Taiwan"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7836-3344","authenticated-orcid":false,"given":"M. Anwar H.","family":"Khan","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0524sp257","id-type":"ROR","asserted-by":"publisher"}],"name":"School of Chemistry, University of Bristol, Cantock\u2019s Close","place":["Bristol, United Kingdom"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7614-9221","authenticated-orcid":false,"given":"Dudley E.","family":"Shallcross","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/0524sp257","id-type":"ROR","asserted-by":"publisher"}],"name":"School of Chemistry, University of Bristol, Cantock\u2019s Close","place":["Bristol, United Kingdom"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Christa","family":"Fittschen","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03k9wer31","id-type":"ROR","asserted-by":"publisher"}],"name":"University Lille, CNRS, UMR 8522, Physicochimie des Processus de Combustion et de l\u2019Atmosph\u00e8re","place":["Lille, France"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5914-5234","authenticated-orcid":false,"given":"Pei-Ling","family":"Luo","sequence":"additional","affiliation":[{"id":[{"id":"https:\/\/ror.org\/03haqsp75","id-type":"ROR","asserted-by":"publisher"}],"name":"Institute of Atomic and Molecular Sciences, Academia Sinica","place":["Taipei, Taiwan"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"341","published-online":{"date-parts":[[2026,9,22]]},"reference":[{"key":"e_1_3_4_1_2","doi-asserted-by":"publisher","DOI":"10.1039\/c2cs35140d"},{"key":"e_1_3_4_2_2","doi-asserted-by":"publisher","DOI":"10.1021\/cr020522s"},{"key":"e_1_3_4_3_2","doi-asserted-by":"publisher","DOI":"10.1029\/2021JD035368"},{"key":"e_1_3_4_4_2","doi-asserted-by":"publisher","DOI":"10.5194\/acp-18-2547-2018"},{"key":"e_1_3_4_5_2","doi-asserted-by":"publisher","DOI":"10.5194\/acp-21-2125-2021"},{"key":"e_1_3_4_6_2","series-title":"Schriften des Forschungszentrums J\u00fclich, Reihe Energie & Umwelt\/Energy & Environment","volume-title":"Measurements of Atmospheric OH and HO Radicals by Laser-Induced Fluorescence on the HALO Aircraft during the OMO-ASIA 2015 Campaign","author":"K\u00fcnstler C.","year":"2020","unstructured":"C. K\u00fcnstler, Measurements of Atmospheric OH and HO Radicals by Laser-Induced Fluorescence on the HALO Aircraft during the OMO-ASIA 2015 Campaign (Schriften des Forschungszentrums J\u00fclich, Reihe Energie & Umwelt\/Energy & Environment, Forschungszentrum J\u00fclich, J\u00fclich, 2020), vol. 495."},{"key":"e_1_3_4_7_2","doi-asserted-by":"publisher","DOI":"10.5194\/amt-5-2025-2012"},{"key":"e_1_3_4_8_2","doi-asserted-by":"publisher","DOI":"10.5194\/acp-12-6799-2012"},{"key":"e_1_3_4_9_2","doi-asserted-by":"publisher","DOI":"10.1029\/2021JD035702"},{"key":"e_1_3_4_10_2","doi-asserted-by":"publisher","DOI":"10.5194\/acp-23-5929-2023"},{"key":"e_1_3_4_11_2","doi-asserted-by":"publisher","DOI":"10.5194\/acp-23-5679-2023"},{"key":"e_1_3_4_12_2","doi-asserted-by":"publisher","DOI":"10.1021\/acsestair.5c00153"},{"key":"e_1_3_4_13_2","doi-asserted-by":"publisher","DOI":"10.5194\/acp-10-5823-2010"},{"key":"e_1_3_4_14_2","doi-asserted-by":"publisher","DOI":"10.1029\/94JD03107"},{"key":"e_1_3_4_15_2","doi-asserted-by":"publisher","DOI":"10.1021\/j100483a002"},{"key":"e_1_3_4_16_2","doi-asserted-by":"publisher","DOI":"10.1021\/j150619a027"},{"key":"e_1_3_4_17_2","doi-asserted-by":"publisher","DOI":"10.1021\/j150654a029"},{"key":"e_1_3_4_18_2","doi-asserted-by":"publisher","DOI":"10.1021\/j100059a016"},{"key":"e_1_3_4_19_2","doi-asserted-by":"publisher","DOI":"10.1029\/2001GL014525"},{"key":"e_1_3_4_20_2","doi-asserted-by":"publisher","DOI":"10.1039\/b502673c"},{"key":"e_1_3_4_21_2","doi-asserted-by":"publisher","DOI":"10.1021\/jp905279b"},{"key":"e_1_3_4_22_2","doi-asserted-by":"publisher","DOI":"10.1021\/acs.jpca.3c03660"},{"key":"e_1_3_4_23_2","volume-title":"Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation No. 19","author":"Burkholder J. B.","year":"2020","unstructured":"J. B. Burkholder , Chemical Kinetics and Photochemical Data for Use in Atmospheric Studies, Evaluation No. 19 (Jet Propulsion Laboratory, Pasadena, CA, 2020), JPL Publication 19-5, https:\/\/jpldataeval.jpl.nasa.gov\/."},{"key":"e_1_3_4_24_2","unstructured":"IUPAC Task Group on Atmospheric Chemical Kinetic Data Evaluation Data sheets for gas-phase reactions of HOx species. https:\/\/iupac.aeris-data.fr\/. Accessed 9 February 2026."},{"key":"e_1_3_4_25_2","doi-asserted-by":"publisher","DOI":"10.1063\/5.0244391"},{"key":"e_1_3_4_26_2","doi-asserted-by":"publisher","DOI":"10.1039\/D5CP01784J"},{"key":"e_1_3_4_27_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.comptc.2020.113010"},{"key":"e_1_3_4_28_2","doi-asserted-by":"publisher","DOI":"10.1039\/C9CP03530C"},{"key":"e_1_3_4_29_2","doi-asserted-by":"publisher","DOI":"10.1023\/A:1005836531979"},{"key":"e_1_3_4_30_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.atmosenv.2008.06.037"},{"key":"e_1_3_4_31_2","unstructured":"National Oceanic and Atmospheric Administration National Aeronautics and Space Administration United States Air Force U.S. Standard Atmosphere 1976. NOAA-S\/T 76-1562 (U.S. Government Printing Office Washington DC 1976)."},{"key":"e_1_3_4_32_2","doi-asserted-by":"publisher","DOI":"10.5194\/acp-10-5191-2010"},{"key":"e_1_3_4_33_2","doi-asserted-by":"publisher","DOI":"10.1029\/2002JD002172"},{"key":"e_1_3_4_34_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.jqsrt.2017.02.013"},{"key":"e_1_3_4_35_2","doi-asserted-by":"publisher","DOI":"10.1364\/OL.413754"},{"key":"e_1_3_4_36_2","doi-asserted-by":"publisher","DOI":"10.1021\/acs.analchem.1c04583"},{"key":"e_1_3_4_37_2","doi-asserted-by":"publisher","DOI":"10.1021\/acs.jpclett.4c00494"},{"key":"e_1_3_4_38_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.atmosenv.2010.01.044"},{"key":"e_1_3_4_39_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.atmosenv.2008.07.028"},{"key":"e_1_3_4_40_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.atmosenv.2008.07.034"},{"key":"e_1_3_4_41_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.atmosenv.2009.01.008"},{"key":"e_1_3_4_42_2","doi-asserted-by":"publisher","DOI":"10.1002\/2016JD026415"},{"key":"e_1_3_4_43_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.atmosenv.2020.117914"},{"key":"e_1_3_4_44_2","unstructured":"J. G. J. Olivier \u201cA set of global emission inventories of greenhouse gases and ozone-depleting substances for all anthropogenic and most natural sources on a per country basis and on 1\u00b0 \u00d7 1\u00b0 grid\u201d (Tech. Rep. RIVM-771060002 Netherlands Environmental Assessment Agency Bilthoven Netherlands 1996)."},{"key":"e_1_3_4_45_2","doi-asserted-by":"publisher","DOI":"10.1016\/j.atmosenv.2014.09.056"},{"key":"e_1_3_4_46_2","first-page":"4729","article-title":"A model for studies of tropospheric ozone and nonmethane hydrocarbons: Model evaluation of ozone-related species","volume":"108","author":"von Kuhlmann R.","year":"2003","unstructured":"R. von Kuhlmann, M. G. Lawrence, P. J. Crutzen, P. J. Rasch, A model for studies of tropospheric ozone and nonmethane hydrocarbons: Model evaluation of ozone-related species. J. Geophys. Res. Atmos. 108, 4729 (2003).","journal-title":"J. Geophys. Res. Atmos."},{"key":"e_1_3_4_47_2","doi-asserted-by":"publisher","DOI":"10.1007\/978-1-4615-2524-0_13"}],"container-title":["Proceedings of the National Academy of Sciences"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pnas.org\/doi\/pdf\/10.1073\/pnas.2606852123","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,22]],"date-time":"2026-09-22T16:12:54Z","timestamp":1790093574000},"score":1,"resource":{"primary":{"URL":"https:\/\/pnas.org\/doi\/10.1073\/pnas.2606852123"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,22]]},"references-count":47,"journal-issue":{"issue":"39","published-print":{"date-parts":[[2026,9,29]]}},"alternative-id":["10.1073\/pnas.2606852123"],"URL":"https:\/\/doi.org\/10.1073\/pnas.2606852123","relation":{},"ISSN":["0027-8424","1091-6490"],"issn-type":[{"value":"0027-8424","type":"print"},{"value":"1091-6490","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,22]]},"assertion":[{"value":"2026-02-25","order":0,"name":"received","label":"Received","group":{"name":"publication_history","label":"Publication History"}},{"value":"2026-08-11","order":2,"name":"accepted","label":"Accepted","group":{"name":"publication_history","label":"Publication History"}},{"value":"2026-09-22","order":3,"name":"published","label":"Published","group":{"name":"publication_history","label":"Publication History"}}],"article-number":"e2606852123"}}