Photo-Induced Coupled Nuclear and Electron Dynamics in the Nucleobase Uracil

Abstract

Photo-initiated processes in molecules often involve complex situations where the induced dynamics is characterized by the interplay of nuclear and electronic degrees of freedom. The interaction of the molecule with an ultrashort laser pulse or the coupling at a conical intersection (CoIn) induces coherent electron dynamics which is subsequently modified by the nuclear motion. The nuclear dynamics typically leads to a fast electronic decoherence but also, depending on the system, enables the reappearance of the coherent electron dynamics. We study this situation for the photo-induced nuclear and electron dynamics in the nucleobase uracil. The simulations are performed with our ansatz for the coupled description of the nuclear and electron dynamics in molecular systems (NEMol). After photo-excitation uracil exhibits an ultrafast relaxation mechanism mediated by CoIn's. Both processes, the excitation by a laser pulse and the non-adiabatic relaxation, are explicitly simulated and the coherent electron dynamics is monitored using our quantum mechanical NEMol approach. The electronic coherence induced by the CoIn is observable for a long time scale due to the delocalized nature of the nuclear wavepacket.

Conical intersection and coherent vibrational dynamics in alkyl iodides captured by attosecond transient absorption spectroscopy

“…The detection of chemical dynamics with electronic-state and vibrationalmode specificity is especially important for understanding nonadiabatic conical intersection dynamics in which the interplay of electronic and nuclear degrees of freedom is key in determining the course of a chemical reaction. [1][2][3][4][5][6][7] Attosecond transient absorption spectroscopy (ATAS) is a powerful, recently developed experimental tool for investigating chemical dynamics. 8 In ATAS, dynamics are tracked through the measurement of element-specific core-tovalence absorption transitions using isolated attosecond pulses in the extreme-ultraviolet (XUV).…”

Q-Band relaxation in chlorophyll: new insights from multireference quantum dynamics

“…Finally, the results are complemented by a simulation of the coupled nuclear and electron dynamics within the Q-band, using the NEMol ansatz. 26–30 Our results shed light on the intimate coupling of the two Q states in chlorophyll and provide a reference for future theoretical and experimental studies.…”

“…The coupled nuclear and electron dynamics was determined using the NEMol ansatz 26–30 developed in our group. Within this purely quantum-mechanical ansatz the electronic wave functions are propagated in the eigenstate basis and coupled to the nuclear wave packet propagated on coupled PESs.…”

“…Within this purely quantum-mechanical ansatz the electronic wave functions are propagated in the eigenstate basis and coupled to the nuclear wave packet propagated on coupled PESs. In this work a NEMol-grid 29,30 of 45 grid points with the same dimensions and spacing as for the calculations of the energies, transition dipole moments and NACs was used. Using the NEMol ansatz, the coupled one-electron density is determined.…”

Time-resolved X-ray and XUV based spectroscopic methods for nonadiabatic processes in photochemistry

“…19–22 In general, a CI creates a coherent superposition of electronic states whose composition is determined by the shape and size of the NAC elements. The coherence lifetime of the superposition depends strongly on the nuclear dynamics 23–26 which is directly influenced by the topography of the CI.…”