{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,31]],"date-time":"2026-03-31T16:23:07Z","timestamp":1774974187321,"version":"3.50.1"},"reference-count":34,"publisher":"AIP Publishing","issue":"14","content-domain":{"domain":["pubs.aip.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2009,10,14]]},"abstract":"<jats:p>The mechanisms of radiationless decay involved in the photodissociation of formaldehyde into H2 and CO have been investigated using complete active space self-consistent field (CASSCF) calculations and direct dynamics variational multiconfiguration Gaussian (DD-vMCG) quantum dynamics in the S1, T1, and S0 states. A commonly accepted scheme involves Fermi Golden Rule internal conversion from S1 followed by dissociation of vibrationally hot H2CO in S0. We recently proposed a novel mechanism [M. Araujo et al., J. Phys. Chem. A\u2008112, 7489 (2008)] whereby internal conversion and dissociation take place in concert through a seam of conical intersection between S1 and S0 after the system has passed through an S1 transition barrier. The relevance of this mechanism depends on the efficiency of tunneling in S1. At lower energy, an alternative scheme to internal conversion involves intersystem crossing via T1 to regenerate the reactant before the S0 barrier to dissociation. We propose here a previously unidentified mechanism leading directly to H2 and CO products via T1. This channel opens at medium energies, near or above the T1 barrier to dissociation and still lower than the S1 barrier, thus making T1 a possible shortcut to molecular dissociation.<\/jats:p>","DOI":"10.1063\/1.3242082","type":"journal-article","created":{"date-parts":[[2009,10,8]],"date-time":"2009-10-08T23:55:00Z","timestamp":1255046100000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":45,"title":["The molecular dissociation of formaldehyde at medium photoexcitation energies: A quantum chemistry and direct quantum dynamics study"],"prefix":"10.1063","volume":"131","author":[{"given":"Marta","family":"Ara\u00fajo","sequence":"first","affiliation":[{"name":"Universidade do Porto 1 REQUIMTE, Faculdade de Ci\u00eancias, , Rua do Campo Alegre, 687, 4169-007 Porto, Portugal"}]},{"given":"Benjamin","family":"Lasorne","sequence":"additional","affiliation":[{"name":"Universit\u00e9 Montpellier 2 2 Institut Charles Gerhardt (UMR 5253), CNRS, , CC 1501, Place Eug\u00e8ne Bataillon, 34095 Montpellier, France"},{"name":"Imperial College London 3 Department of Chemistry, , London SW7 2AZ, United Kingdom"}]},{"given":"Alexandre L.","family":"Magalh\u00e3es","sequence":"additional","affiliation":[{"name":"Universidade do Porto 1 REQUIMTE, Faculdade de Ci\u00eancias, , Rua do Campo Alegre, 687, 4169-007 Porto, Portugal"}]},{"given":"Graham A.","family":"Worth","sequence":"additional","affiliation":[{"name":"University of Birmingham 4 School of Chemistry, , Edgbaston, Birmingham B15 2TT, United Kingdom"}]},{"given":"Michael J.","family":"Bearpark","sequence":"additional","affiliation":[{"name":"Imperial College London 3 Department of Chemistry, , London SW7 2AZ, United Kingdom"}]},{"given":"Michael A.","family":"Robb","sequence":"additional","affiliation":[{"name":"Imperial College London 3 Department of Chemistry, , London SW7 2AZ, United Kingdom"}]}],"member":"317","published-online":{"date-parts":[[2009,10,8]]},"reference":[{"key":"2023062604250261900_c1","doi-asserted-by":"publisher","first-page":"323","DOI":"10.1146\/annurev.pc.28.100177.001543","volume":"28","year":"1977","journal-title":"Annu. 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