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Using 266 nm pump and 200 nm probe pulses with an overall instrument response function of 160 fs, the experiment directly resolves the complete early-time evolution following photoexcitation. Following rapid internal conversion (SP\u2013S2 \u2192 SP\u2013S1), the excited-state population bifurcates into two competing pathways with a branching ratio close to 70\/30: one channel leads to merocyanine formation via a multi-configurational excited state, and the other channel involving intersystem crossing (ISC) to a long-lived triplet-state (T2) manifold. Calculations at the MS-CASPT2\/6-31G* level support the spectral assignments and the identification of the key transient intermediates. Our results provide a comprehensive picture of isolated spiropyran photoisomerization dynamics and clarify the elementary branching dynamics that control the competition between productive ring opening and nonreactive relaxation.<\/jats:p>","DOI":"10.1021\/acs.jpca.6c04049","type":"journal-article","created":{"date-parts":[[2026,9,10]],"date-time":"2026-09-10T20:01:26Z","timestamp":1789070486000},"page":"7593-7601","source":"Crossref","is-referenced-by-count":0,"title":["Mapping the Excited\nState Dynamics of Gas-Phase Spiropyran\nwith Time-Resolved Photoelectron Spectroscopy"],"prefix":"10.1021","volume":"130","author":[{"given":"Xuegang","family":"Liu","sequence":"first","affiliation":[{"name":"Tsinghua University , , ,","place":["Beijing, China, 100084"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shijie","family":"Zheng","sequence":"additional","affiliation":[{"name":"Tsinghua University , , ,","place":["Beijing, China, 100084"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chuyuan","family":"Zhai","sequence":"additional","affiliation":[{"name":"Tsinghua University , , ,","place":["Beijing, China, 100084"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-5115-2413","authenticated-orcid":true,"given":"Jie","family":"Yang","sequence":"additional","affiliation":[{"name":"Tsinghua University , , ,","place":["Beijing, China, 100084"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"316","published-online":{"date-parts":[[2026,9,10]]},"reference":[{"issue":"44","key":"2026092408075128600_cit1","doi-asserted-by":"publisher","first-page":"11675","DOI":"10.1039\/C5TC02100F","article-title":"Design of rewritable and read-only non-volatile optical\nmemory elements using photochromic spiropyran-based salts as light-sensitive\nmaterials","volume":"3","author":"Frolova","year":"2015","journal-title":"J. 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B"}],"container-title":["The Journal of Physical\nChemistry A"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.acs.org\/doi\/pdf\/10.1021\/acs.jpca.6c04049","content-type":"application\/pdf","content-version":"vor","intended-application":"unspecified"},{"URL":"https:\/\/pubs.acs.org\/jpcafh\/article-pdf\/130\/38\/7593\/68477448\/acs.jpca.6c04049.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.acs.org\/jpcafh\/article-pdf\/130\/38\/7593\/68477448\/acs.jpca.6c04049.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,9,24]],"date-time":"2026-09-24T12:18:18Z","timestamp":1790252298000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.acs.org\/jpcafh\/article\/130\/38\/7593\/5427984\/Mapping-the-Excited-State-Dynamics-of-Gas-Phase"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,9,10]]},"references-count":32,"journal-issue":{"issue":"38","published-online":{"date-parts":[[2026,9,10]]},"published-print":{"date-parts":[[2026,9,24]]}},"URL":"https:\/\/doi.org\/10.1021\/acs.jpca.6c04049","relation":{},"ISSN":["1089-5639","1520-5215"],"issn-type":[{"value":"1089-5639","type":"print"},{"value":"1520-5215","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,9,10]]}}}