{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,11]],"date-time":"2026-06-11T18:18:13Z","timestamp":1781201893352,"version":"3.54.1"},"reference-count":39,"publisher":"AIP Publishing","issue":"12","content-domain":{"domain":["pubs.aip.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[2013,9,28]]},"abstract":"<jats:p>A widely acclaimed model for the excited state relaxation dynamics of auramine-O involves orientational relaxation of dimethylanilino moieties along the barrierless excited state potential energy surface (PES). Such a model would necessitate similar excited state dynamics in media offering similar viscous drag. However, we have noticed an interesting experimental observation showing auramine-O to have \u223c8 times larger fluorescence quantum yield in chloroform than in methanol, though both the solvents have the same viscosity. The femtosecond fluorescence transients of auramine-O in chloroform surprisingly depict a rise in fluorescence transients, which has not been observed before. This, along with the simultaneous observation of unexpectedly large fluorescence lifetime and multi-exponential transients (in chloroform) questions the thoroughly accepted barrierless model of auramine-O relaxation dynamics, as the barrierless model would demand a short lifetime and single-exponential decay. Temperature dependent quantum yield measurements along with solvent dependent excited state multi-coordinate time-dependent density functional theory calculations further unveil the exact nature of PES. All these results concomitantly conclude that, at-least in chloroform, upon photo-excitation auramine-O must pass over an activation barrier before damping the excited state population into ground state via a sink function through adiabatic coupling of the electronic states.<\/jats:p>","DOI":"10.1063\/1.4821456","type":"journal-article","created":{"date-parts":[[2013,9,24]],"date-time":"2013-09-24T03:46:25Z","timestamp":1379994385000},"update-policy":"https:\/\/doi.org\/10.1063\/aip-crossmark-policy-page","source":"Crossref","is-referenced-by-count":12,"title":["Spectroscopic evidence of the presence of an activation barrier in the otherwise barrierless excited state potential energy surface of auramine-O: A femtosecond fluorescence up-conversion study"],"prefix":"10.1063","volume":"139","author":[{"given":"Shahnawaz R.","family":"Rather","sequence":"first","affiliation":[{"name":"Indian Institute of Technology Kanpur Department of Chemistry, , Kanpur 208016, UP, India"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Pratik","family":"Sen","sequence":"additional","affiliation":[{"name":"Indian Institute of Technology Kanpur Department of Chemistry, , Kanpur 208016, UP, India"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"317","published-online":{"date-parts":[[2013,9,23]]},"reference":[{"key":"2024022020561690100_c1","doi-asserted-by":"publisher","first-page":"1073","DOI":"10.1126\/science.1160902","volume":"322","year":"2008","journal-title":"Science"},{"key":"2024022020561690100_c2","doi-asserted-by":"publisher","first-page":"084308","DOI":"10.1063\/1.4792933","volume":"138","year":"2013","journal-title":"J. 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Lett."},{"key":"2024022020561690100_c39","unstructured":"See supplementary material at http:\/\/dx.doi.org\/10.1063\/1.4821456E-JCPSA6-139-073336 for comparison of femtosecond fluorescence transients of auramine-O in methanol, chloroform, and dimethylsulfoxide measured at three emission wavelengths; plot showing variation of ln\u2009(\u03b7)\u2009vs\u20091\/T(K) giving activation energy for the viscous flow in methanol and in chloroform; structure of HOMO and LUMO of auramine-O; the contour plots of the ground and excited electronic states of auramine-O in methanol and in chloroform along the torsional coordinates of theta and phi dihedral angles."}],"container-title":["The Journal of Chemical Physics"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/pubs.aip.org\/aip\/jcp\/article-pdf\/doi\/10.1063\/1.4821456\/19685567\/124302_1_1.4821456.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/pubs.aip.org\/aip\/jcp\/article-pdf\/doi\/10.1063\/1.4821456\/19685567\/124302_1_1.4821456.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2024,2,20]],"date-time":"2024-02-20T20:56:26Z","timestamp":1708462586000},"score":1,"resource":{"primary":{"URL":"https:\/\/pubs.aip.org\/jcp\/article\/139\/12\/124302\/75112\/Spectroscopic-evidence-of-the-presence-of-an"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2013,9,23]]},"references-count":39,"journal-issue":{"issue":"12","published-print":{"date-parts":[[2013,9,28]]}},"URL":"https:\/\/doi.org\/10.1063\/1.4821456","relation":{},"ISSN":["0021-9606","1089-7690"],"issn-type":[{"value":"0021-9606","type":"print"},{"value":"1089-7690","type":"electronic"}],"subject":[],"published-other":{"date-parts":[[2013,9,28]]},"published":{"date-parts":[[2013,9,23]]},"article-number":"124302"}}