Validity of the Bersohn–Zewail model beyond justification

Petersen, Jakob; Henriksen, Niels Engholm; Møller, Klaus Braagaard

doi:10.1016/j.cplett.2012.05.022

Cited by 11 publications

(8 citation statements)

References 30 publications

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“…In a second vacuum ΔSCF BOMD simulation, we have propagated an S 1 trajectory starting from the optimized geometry of the ground state. This second choice of initial conditions corresponds to a CW (infinitely long) pump pulse, in which case, the excitation window of eq 17 is a delta function and only one trajectory is propagated (this is the Bersohn− Zewail model; see ref 88). This simulation was aimed at producing a picture of the dynamics that is closer to the events that take place in an ultrafast pump−probe experiment than the one that emerges from the first simulation.…”

Section: ■ Computational Methodsmentioning

confidence: 99%

“…82 Throughout the dynamics the positions of the counterions were restrained by applying a spherical harmonic potential of the form: Excitation to the S 1 state by an ultrashort optical pulse was simulated by instantaneously promoting ground-state molecules from the underlying ground-state distribution of Pt-Pt distances (P eq GS (d PtPt )) according to a spatial filtering (SF) approximation. [87][88][89][90][91] This approximation takes into account the bandwidth of the pulse but neglects any effect due to nuclear motion throughout its finite temporal duration. Hence, we assumed a Gaussian…”

Section: Computational Detailsmentioning

confidence: 99%

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Solution Structure and Ultrafast Vibrational Relaxation of the PtPOP Complex Revealed by ΔSCF-QM/MM Direct Dynamics Simulations

et al. 2018

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Recent ultrafast experiments have unveiled the time scales of vibrational cooling and decoherence upon photoexcitation of the diplatinum complex [Pt2(P2O5H2)4]4– in solvents. Here, we contribute to the understanding of the structure and dynamics of the lowest lying singlet excited state of the model photocatalyst by performing potential energy surface calculations and Born–Oppenheimer molecular dynamics simulations in the gas phase and in water. Solvent effects were treated using a multiscale quantum mechanics/molecular mechanics approach. Fast sampling was achieved with a modified version of delta self-consistent field implemented in the grid-based projector-augmented wave density functional theory code. The known structural parameters and the PESs of the first singlet and triplet excited states are correctly reproduced. Besides, the simulations deliver clear evidence that pseudorotation of the ligands in the excited state leads to symmetry lowering of the Pt2P8 core. Coherence decay of Pt–Pt stretching vibrations in solution was found to be governed by vibrational cooling, which is in agreement with previous ultrafast experiments. We also show that the flow of excess Pt–Pt vibrational energy is first directed toward vibrational modes involving the ligands, with the solvent favoring intramolecular vibrational energy redistribution. The results are supported by thorough vibrational analysis in terms of generalized normal modes.

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Section: ■ Computational Methodsmentioning

confidence: 99%

Section: Computational Detailsmentioning

confidence: 99%

Solution Structure and Ultrafast Vibrational Relaxation of the PtPOP Complex Revealed by ΔSCF-QM/MM Direct Dynamics Simulations

et al. 2018

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“…All ab initio calculations were performed with the Gaussian 09 program package. 33 The CAM-B3LYP 34 The evolution of vibrational wavepackets on the ionic potential surfaces D 0 and D 1 was assessed using classical trajectories 35,36 of the packet center. The dependence of the potential surfaces on the CNNC angle, ϕ , was represented via the truncated Fourier series,…”

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confidence: 99%

Conserving Coherence and Storing Energy during Internal Conversion: Photoinduced Dynamics of cis- and trans-Azobenzene Radical Cations

et al. 2017

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Light harvesting via energy storage in azobenzene has been a key topic for decades and the process of energy distribution over the molecular degrees of freedom following photoexcitation remains to be understood. Dynamics of a photoexcited system can exhibit high degrees of nonergodicity when it is driven by just a few degrees of freedom. Typically, an internal conversion leads to the loss of such localization of dynamics as the intramolecular energy becomes statistically redistributed over all molecular degrees of freedom. Here, we present a unique case where the excitation energy remains localized even subsequent to internal conversion. Strong-field ionization is used to prepare cis- and trans-azobenzene radical cations on the D₁ surface with little excess energy at the equilibrium neutral geometry. These D₁ ions are preferably formed because in this case D₁ and D₀ switch place in the presence of the strong laser field. The postionization dynamics are dictated by the potential energy landscape. The D₁ surface is steep downhill along the cis/trans isomerization coordinate and toward a common minimum shared by the two isomers in the region of D₁/D₀ conical intersection. Coherent cis/trans torsional motion along this coordinate is manifested in the ion transients by a cosine modulation. In this scenario, D₀ becomes populated with molecules that are energized mainly along the cis–trans isomerization coordinate, with the kinetic energy above the cis–trans interconversion barrier. These activated azobenzene molecules easily cycle back and forth along the D₀ surface and give rise to several periods of modulated signal before coherence is lost. This persistent localization of the internal energy during internal conversion is provided by the steep downhill potential energy surface, small initial internal energy content, and a strong hole–lone pair interaction that drives the molecule along the cis–trans isomerization coordinate to facilitate the transition between the involved electronic states

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“…From a theoretical perspective, an accurate description of molecular dynamics in excited electronic states, when the Born-Oppenheimer approximation may break down, is required for understanding light-triggered phenomena. However, an important, yet often neglected aspect when seeking a synergy between experiment and theory is that the latter should include the description of the external field which generates the initial photoexcited state [4,5].…”

Section: Introductionmentioning

confidence: 99%

Excited state dynamics initiated by an electromagnetic field within the Variational Multi-Configurational Gaussian (vMCG) method

Penfold

Pápai

Møller

et al. 2019

Computational and Theoretical Chemistry

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The Variational Multi-Configurational Gaussian (vMCG) approach offers a framework to perform exact trajectory-based quantum dynamics. Herein we use two model vibronic coupling Hamiltonians of pyrazine to explore, for the first time, the influence of the coupling between the external field and the Gaussian basis functions (GBFs) in vMCG on the dynamics. We show that when the excitation pulse is short compared to the nuclear dynamics, vertical projection without a field and explicit description of the external field converge. For longer pulses, a sizeable change is observed. We demonstrate that comparatively few GBFs are sufficient to provide qualitative agreement to MCTDH dynamics and a quantitative agreement can be achieved using ∼100 GBFs. Longer pulses require more GBFs due to the prolonged coupling between the ground and excited states. Throughout the single set formalism offers the fastest convergence.

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Validity of the Bersohn–Zewail model beyond justification

Cited by 11 publications

References 30 publications

Solution Structure and Ultrafast Vibrational Relaxation of the PtPOP Complex Revealed by ΔSCF-QM/MM Direct Dynamics Simulations

Solution Structure and Ultrafast Vibrational Relaxation of the PtPOP Complex Revealed by ΔSCF-QM/MM Direct Dynamics Simulations

Conserving Coherence and Storing Energy during Internal Conversion: Photoinduced Dynamics of cis- and trans-Azobenzene Radical Cations

Excited state dynamics initiated by an electromagnetic field within the Variational Multi-Configurational Gaussian (vMCG) method

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