Dynamics starting at a conical intersection: Application to the photochemistry of pyrrole

Sellner, Bernhard; Barbatti, Mario; Lischka, Hans

doi:10.1063/1.3175799

Cited by 58 publications

(74 citation statements)

References 54 publications

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“…10,[12][13][14]21,22,29 These are generally in good agreement with experiment and provide very detailed information on the nonadiabatic decay channels of the electronically excited states.…”

Section: Introductionsupporting

confidence: 76%

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Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

Neville

Schalk

et al. 2015

The Journal of Chemical Physics

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Coherent polyatomic dynamics studied by femtosecond time-resolved photoelectron spectroscopy: Dissociation of vibrationally excited C S 2 in the 6 s and 4 d Rydberg states J. Chem. Phys. 125, 174314 (2006) The dynamics of pyrrole excited at wavelengths in the range 242-217 nm are studied using a combination of time-resolved photoelectron spectroscopy and wavepacket propagations performed using the multi-configurational time-dependent Hartree method. Excitation close to the origin of pyrrole's electronic spectrum, at 242 and 236 nm, is found to result in an ultrafast decay of the system from the ionization window on a single timescale of less than 20 fs. This behaviour is explained fully by assuming the system to be excited to the A 2 (πσ * ) state, in accord with previous experimental and theoretical studies. Excitation at shorter wavelengths has previously been assumed to result predominantly in population of the bright A 1 (ππ * ) and B 2 (ππ * ) states. We here present time-resolved photoelectron spectra at a pump wavelength of 217 nm alongside detailed quantum dynamics calculations that, together with a recent reinterpretation of pyrrole's electronic spectrum [S. P. Neville and G. A. Worth, J. Chem. Phys. 140, 034317 (2014)], suggest that population of the B 1 (πσ * ) state (hitherto assumed to be optically dark) may occur directly when pyrrole is excited at energies in the near UV part of its electronic spectrum. The B 1 (πσ * ) state is found to decay on a timescale of less than 20 fs by both N-H dissociation and internal conversion to the A 2 (πσ * ) state. C 2015 AIP Publishing LLC. [http://dx

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Section: Introductionsupporting

confidence: 76%

“…(14). There is only one time constant derived for pyrrole pumped at long wavelengths: 19 fs and 12 fs for pump wavelengths of 236 and 242 nm, respectively.…”

Section: A Assignment Of the Fitted Time Constantsmentioning

confidence: 99%

Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

Neville

Schalk

et al. 2015

The Journal of Chemical Physics

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“…[1][2][3][4][5] They serve as efficient funnels for non-adiabatic relaxation of electronically excited states and thus often govern their lifetimes and the branching ratio of photoproducts. [4][5][6][7] The topography of CIs and the shapes of the corresponding intersecting potential energy surfaces (PESs) are important characteristics that largely determine the non-adiabatic dynamics. [7][8][9] The most important descriptors in this regard are the so-called branching plane vectors, 8 i.e., the atomic displacements along which the degeneracy of the electronic states at a CI is lifted.…”

Section: Introductionmentioning

confidence: 99%

“…These vectors span the branching plane (BP) which comprises the possible directions for exiting the strong non-adiabatic coupling regime at a CI. 6,7 Conceptually, multireference quantum-chemical methods of ab initio wavefunction theory are best suited to investigate CIs and non-adiabatic dynamics in molecules. 10 Methods such as complete-active-space second-order perturbation theory (CASPT2) 11 and multireference configuration interaction with single and double excitations (MRCISD or MRCI, for brevity) 12 are capable of providing accurate computational results for small and mid-size molecules.…”

Section: Introductionmentioning

confidence: 99%

Assessment of approximate computational methods for conical intersections and branching plane vectors in organic molecules

Nikiforov

Gámez

Thiel

et al. 2014

The Journal of Chemical Physics

136

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Quantum-chemical computational methods are benchmarked for their ability to describe conical intersections in a series of organic molecules and models of biological chromophores. Reference results for the geometries, relative energies, and branching planes of conical intersections are obtained using ab initio multireference configuration interaction with single and double excitations (MRCISD). They are compared with the results from more approximate methods, namely, the state-interaction state-averaged restricted ensemble-referenced Kohn-Sham method, spin-flip time-dependent density functional theory, and a semiempirical MRCISD approach using an orthogonalization-corrected model. It is demonstrated that these approximate methods reproduce the ab initio reference data very well, with root-mean-square deviations in the optimized geometries of the order of 0.1 Å or less and with reasonable agreement in the computed relative energies. A detailed analysis of the branching plane vectors shows that all currently applied methods yield similar nuclear displacements for escaping the strong non-adiabatic coupling region near the conical intersections. Our comparisons support the use of the tested quantum-chemical methods for modeling the photochemistry of large organic and biological systems. © 2014 AIP Publishing LLC. [http://dx

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“…We note that a similar approach has also been used to investigate the dynamics starting from conical intersection on top of the reaction barrier on the excited states. 59,60 (c) Experimental approach Experiments were done by photolyzing undecanal (a straight-chain aliphatic C11 aldehyde), which conveniently adopts a liquid state under standard conditions. A sample cell with 1 inch diameter calcium fluoride windows and an adjustable (10-1000 mm) path length from Harrick Scientific was used in these experiments.…”

confidence: 99%

Photochemistry of aldehyde clusters: cross-molecular versus unimolecular reaction dynamics

Shemesh

Blair

Nizkorodov

et al. 2014

Phys. Chem. Chem. Phys.

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The unimolecular photochemistry of aldehydes has been extensively studied, both experimentally and computationally. However, less is known about the role of cross-molecular photochemical processes in the condensed-phase photolysis of aldehydes. The triplet-state photochemistry of pentanal in its pentameric (n = 5) cluster was investigated as a model for photochemical reactions of aliphatic aldehydes in atmospheric aerosols. This study employs ''on the fly'' dynamics simulations using a semi-empirical MRCI electronic code for the singlet and triplet states involved. Previous studies have shown that the triplet-state photochemistry of an isolated pentanal molecule is dominated by Norrish I and II reactions. The main findings for the cluster are: (1) 55% of the trajectories lead to a unimolecular or cross-molecular reaction within a timescale of 100 ps; (2) cross-molecular reactions occur in over 70% of the reactive trajectories; (3) the main cross-molecular processes involve an H-atom transfer from the CHO group of the excited pentanal to an O atom of a nearby pentanal; and (4) the unimolecular Norrish II reaction is suppressed by the cluster environment. The predictions are qualitatively supported by experimental results on the condensed-phase photolysis of an aliphatic aldehyde, undecanal. The computational approach should be useful for predicting the mechanisms of other condensed-phase organic photochemical reactions. These results demonstrate a major role of cross-molecular processes in the condensed-phase photolysis of carbonyls. The cross-molecular reactions discussed in this work are relevant to photolysis-driven processes in atmospheric organic aerosols. It is expected that the condensed-phase environment of an organic aerosol particle should support a multitude of similar cross-molecular photochemical processes.

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Dynamics starting at a conical intersection: Application to the photochemistry of pyrrole

Cited by 58 publications

References 54 publications

Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

Excited state non-adiabatic dynamics of pyrrole: A time-resolved photoelectron spectroscopy and quantum dynamics study

Assessment of approximate computational methods for conical intersections and branching plane vectors in organic molecules

Photochemistry of aldehyde clusters: cross-molecular versus unimolecular reaction dynamics

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