<i>Ab initio</i> investigation of potential-energy surfaces involved in the photophysics of benzene and pyrazine

Sobolewski, Andrzej L.; Woywod, Clemens; Domcke, Wolfgang

doi:10.1063/1.464907

Cited by 141 publications

(100 citation statements)

References 62 publications

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“…This is also in agreement with theoretical results. 43 Consequently, for BZA and ACP, each with a low-lying S 1 (nπ*) state, their rapid electronic relaxation rates are much greater than that of benzene because (i) the isomerization pathway to the prefulvenic form has no barrier, as in the case of pyrazine, or (ii) because electronic relaxation to S 1 (nπ*) followed by rapid ISC to triplet states becomes important. Since T 1 (nπ*) f S 0 phosphorescence of BZA was observed upon S 2 (ππ*) excitation, 83 it was suggested that a S 2 (ππ*)-T 1 (nπ*) relaxation channel may exist prior to phosphorescence.…”

Section: Discussionmentioning

confidence: 99%

“…In direct S 2 (ππ*) excitation, it was assumed that the S 2 (ππ*)-S 1 (nπ*) IC rate is much more rapid than the S 1 (nπ*) decay rate. 33 Theoretical calculations on pyrazine 43 indicate that the S 1 (nπ*) PES intersects the S 2 (ππ*) surface near the S 2 minimum and, via the ν 10a (B 1g ) vibrational mode, form a conical intersection. 82 Theoretical results 43 also indicate that the pyrazine S 2 (ππ*) surface exhibits a behavior similar to that of the benzene S 1 (ππ*) surface, the latter correlating with the ground state of the prefulvenic form and, therefore, there exists no isomerization barrier in the reaction path.…”

Section: Discussionmentioning

confidence: 99%

“…With increasing size, the channel-three threshold falls in the order benzene < naphthalene < anthracene < tetracene. Sobolewski et al 43 performed quantum-chemical calculations on potential energy surfaces (PES) for benzene isomerization to prefulvene (diradical form); they concluded that the S 1 PES minimum is separated from that of prefulvene by a 3750 cm -1 barrier, in accordance with the threshold for channel-three decay in benzene. The proposed IC pathway starts at the S 1 minimum geometry and then overcomesstunnels throughsthe transition state to prefulvene, whereupon it enters the S 0 surface via S 1 -S 0 IC.…”

Section: Photophysics Of Benzenesmentioning

confidence: 99%

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Substituent Effects in Molecular Electronic Relaxation Dynamics via Time-Resolved Photoelectron Spectroscopy: ππ* States in Benzenes

et al. 2002

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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=316e48fa-9e40-45c2-af08-952c6eee950f http://nparc.cisti-icist.nrc-cnrc.gc.ca/fra/voir/objet/?id=316e48fa-9e40-45c2-af08-952c6eee950f We study the applicability of femtosecond time-resolved photoelectron spectroscopy to the study of substituent effects in molecular electronic relaxation dynamics using a series of monosubstituted benzenes as model compounds. Three basic types of electronic substituents were used: CdC (styrene), CdO (benzaldehyde), and CtC (phenylacetylene). In addition, the effects of the rigidity and vibrational density of states of the substituent were investigated via both methyl (R-methylstyrene, acetophenone) and alkyl ring (indene) substitution. Femtosecond excitation to the second ππ* state leads, upon time-delayed ionization, to two distinct photoelectron bands having different decay constants. Variation of the ionization laser frequency had no effect on the photoelectron band shapes or lifetimes, indicating that autoionization from super-excited states played no discernible role. From assignment of the energy-resolved photoelectron spectra, a fast decaying component was attributed to electronic relaxation of the second ππ* state, a slower decaying component to the first ππ* state. Very fast electronic relaxation constants (<100 fs) for the second ππ* states were observed for all molecules studied and are explained by relaxation to the first ππ* via a conical intersection near the planar minimum. Although a "floppy" methyl substitution (R-methylstyrene, acetophenone) leads as expected to even faster second ππ* decay rates, a rigid ring substitution (indene) has no discernible effect. The much slower electronic relaxation constants of the first ππ* states for styrene and phenylacetylene are very similar to those of benzene in its first ππ* state, at the same amount of vibrational energy. By contrast, the lifetime of the first ππ* state of indene was much longer, attributed to its rigid structure. The second ππ* state of benzaldehyde has a short lifetime, similar to the other derivat...

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Photophysics Of Benzenesmentioning

confidence: 99%

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Substituent Effects in Molecular Electronic Relaxation Dynamics via Time-Resolved Photoelectron Spectroscopy: ππ* States in Benzenes

et al. 2002

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“…In this paper, we describe a method which enables the a priori selection of these important coordinates for a photochemical reaction using an analytic simultaneous representation of both ground and excited states correct to second order in the energy ͑i.e., using analytic gradients and second derivatives of the energy difference [8][9][10] ͒. The efficacy of the method will be illustrated using the channel 3 photochemistry of benzene, 11,12 where the energy difference was analyzed at the S 0 minimum.…”

Section: Introductionmentioning

confidence: 99%

Automatic generation of active coordinates for quantum dynamics calculations: Application to the dynamics of benzene photochemistry

Lasorne¹,

Sicilia²,

Bearpark³

et al. 2008

The Journal of Chemical Physics

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A new practical method to generate a subspace of active coordinates for quantum dynamics calculations is presented. These reduced coordinates are obtained as the normal modes of an analytical quadratic representation of the energy difference between excited and ground states within the complete active space self-consistent field method. At the Franck-Condon point, the largest negative eigenvalues of this Hessian correspond to the photoactive modes: those that reduce the energy difference and lead to the conical intersection; eigenvalues close to 0 correspond to bath modes, while modes with large positive eigenvalues are photoinactive vibrations, which increase the energy difference. The efficacy of quantum dynamics run in the subspace of the photoactive modes is illustrated with the photochemistry of benzene, where theoretical simulations are designed to assist optimal control experiments.

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“…The first two excited singlet states, S 1 and S 2 , resulting from promotion of either a non-bonding or a valence π electron to an anti-bonding π * orbital, correspond to diabatic states with 1 B 3u and 1 B 2u symmetries, respectively. [22] These diabatic states are strongly coupled by the 10a bending mode of b 1u symmetry. [23] Because of this strong coupling, the S 2 spectrum is very diffuse, [24,25] and IC occurs in only 22 fs.…”

Section: Introductionmentioning

confidence: 99%

Coherent phase control of internal conversion in pyrazine

Seideman

Singha

et al. 2015

The Journal of Chemical Physics

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Shaped ultrafast laser pulses were used to study and control the ionization dynamics of electronically excited pyrazine in a pump and probe experiment. For pump pulses created without feedback from the product signal, the ion growth curve (the parent ion signal as a function of pump/probe delay) was described quantitatively by the classical rate equations for internal conversion of the S 2 and S 1 states. Very different, non-classical behavior was observed when a genetic algorithm (GA) was used to minimize the ion signal at some pre-determined target time, T. Two qualitatively different control mechanisms were identified for early (T< 1.5 ps) and late (T> 1.5 ps) target times. In the former case, the ion signal was largely suppressed for t < T , while for t T the ion signal produced by the GA-optimized pulse and a transform limited (TL) pulse coalesced. In contrast, for T > 1.5 ps the ion growth curve followed the classical rate equations for t < T , while for t T the quantum yield for the GA-optimized pulse was much smaller than for a TL pulse. We interpret the first type of behavior as an indication that the wave packet produced by the pump laser is localized in a region of the S 2 potential energy surface where the vertical ionization energy exceeds the probe photon energy, whereas the second type of behavior may be described by a reduced absorption cross section for S 0 → S 2 followed by incoherent decay of the excited molecules. * rjgordon@uic.edu 2

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Ab initio investigation of potential-energy surfaces involved in the photophysics of benzene and pyrazine

Cited by 141 publications

References 62 publications

Substituent Effects in Molecular Electronic Relaxation Dynamics via Time-Resolved Photoelectron Spectroscopy: ππ* States in Benzenes

Substituent Effects in Molecular Electronic Relaxation Dynamics via Time-Resolved Photoelectron Spectroscopy: ππ* States in Benzenes

Automatic generation of active coordinates for quantum dynamics calculations: Application to the dynamics of benzene photochemistry

Coherent phase control of internal conversion in pyrazine

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