Time-resolved photoelectron spectroscopy was used to obtain new information about the dynamics of electronic relaxation in gas-phase indole and 5-hydroxyindole following UV excitation with femtosecond laser pulses centred at 249 nm and 273 nm. Our analysis of the data was supported by ab initio calculations at the coupled cluster and complete-active-space self-consistent-field levels. The optically bright 1 L a and 1 L b electronic states of 1 ππ* character and spectroscopically dark and dissociative 1 πσ* states were all found to play a role in the overall relaxation process. In both molecules we conclude that the initially excited 1 L a state decays non-adiabatically on a sub 100 fs timescale via two competing pathways, populating either the subsequently long-lived 1 L b state or the 1 πσ* state localised along the N-H coordinate, which exhibits a lifetime on the order of 1 ps. In the case of 5-hydroxyindole, we conclude that the 1 πσ* state localised along the O-H coordinate plays little or no role in the relaxation dynamics at the two excitation wavelengths studied.

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. For the publisher's version, please access the DOI link below./ Pour consulter la version de l'éditeur, utilisez le lien DOI ci-dessous.http://doi.org/10.1021/acs.jpca.5b04900Access and use of this website and the material on it are subject to the Terms and Conditions set forth at Ultrafast dynamics of o-nitrophenol: An experimental and theoretical study Ernst, Hanna A.; Wolf, Thomas J. A.; Schalk, Oliver; González-García, Nuria; Boguslavskiy, Andrey E.; Stolow, Albert; Olzmann, Matthias; Unterreiner, Andreas-Neil http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/droits L'accès à ce site Web et l'utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D'UTILISER CE SITE WEB. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=ce83ef5b-a095-4e1f-85dd-e4e329f4a190 http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=ce83ef5b-a095-4e1f-85dd-e4e329f4a190 ABSTRACT: The photolysis of o-nitrophenol (o-NP), a typical push−pull molecule, is of current interest in atmospheric chemistry as a possible source of nitrous acid (HONO). To characterize the largely unknown photolysis mechanism, the dynamics of the lowest lying excited singlet state (S 1 )o fo-NP was investigated by means of femtosecond transient absorption spectroscopy in solution, time-resolved photoelectron spectroscopy (TRPES) in the gas phase and quantum chemical calculations. Evidence of the unstable aci-nitro isomer is provided both in the liquid and in the gas phase. Our results indicate that the S 1 state displays strong charge transfer character, which triggers excited state proton transfer from the OH to the NO 2 group as evidenced by a temporal shift of 20 fs of the onset of the photoelectron spectrum. The proton transfer itself is found to be coupled to an out-ofplane rotation of the newly formed HONO group, finally leading to a conical intersection between S 1 and the ground state S 0 . In solution, return to S 0 within 0.2−0.3 ps was monitored by stimulated emission. As a competitive relaxation channel, ultrafast intersystem cro...

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n'arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. Questions? Contact the NRC Publications Archive team atPublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information. NRC Publications Archive Archives des publications du CNRCThis publication could be one of several versions: author's original, accepted manuscript or the publisher's version. / La version de cette publication peut être l'une des suivantes : la version prépublication de l'auteur, la version acceptée du manuscrit ou la version de l'éditeur. NRC Publications Record / Notice d'Archives des publications de CNRC:http://nparc.cisti-icist.nrc-cnrc.gc.ca/eng/view/object/?id=abe61567-bc3d-4da8-8fbb-4d11f64ccc91 http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=abe61567-bc3d-4da8-8fbb-4d11f64ccc91 Substituent Effects on Dynamics at Conical Intersections: CyclopentadienesOliver Schalk, Andrey E. Boguslavskiy, and Albert Stolow* Steacie Institute for Molecular Sciences, National Research Council, Ottawa, Ontario K1A 0R6, Canada ReceiVed: NoVember 27, 2009; ReVised Manuscript ReceiVed: January 29, 2010 Substituent effects on dynamics at conical intersections are investigated by means of femtosecond timeresolved photoelectron spectroscopy for cyclopentadiene and its substituted analogues 1,2,3,4-tetramethylcyclopentadiene, 1,2,3,4,5-pentamethylcyclopentadiene, and 1,2,3,4-tetramethyl-5-propylcyclopentadiene. By UV excitation to the S 2 (1 1 B 2 ) state, the influence of these substitutions on dynamics for the initially excited S 2 (1 1 B 2 ) surface and the spectroscopically dark S 1 (2 1 A 1 ) surface were investigated. We observed that the dynamics depend only on a small number of specific vibrations. Whereas dynamics at the S 2 /S 1 -conical intersection are independent of substitution at the 5-position, internal conversion dynamics on the S 1 (2 1 A 1 ) surface slow down as the inertia of the 5-substituent increases. Contrary to the expectations of simple models of radiationless transitions, an increasing density of states does not lead to faster processes, suggesting that a true dynamical picture of vibrational motions at conical intersections will be required.