Simulation of photo-excited adenine in water with a hierarchy of equations of motion approach

Abstract

We present a theoretical method to simulate the electronic dynamics and two-dimensional ultraviolet spectra of the nucleobase adenine in water. The method is an extension of the hierarchy of equations of motion approach to treat a model with one or more conical intersections. The application to adenine shows that a two-level model with a direct conical intersection between the optically bright state and the ground state, generating a hot ground state, is not consistent with experimental observations. This supports a three-level model for the decay of electronically excited adenine in water as was previously proposed in the work of V. I. Prokhorenko et al. [J. Phys. Chem. Lett. 7, 4445 (2016)].

Spectral Filtering as a Tool for Two-Dimensional Spectroscopy: A Theoretical Model

“…The hierarchy is terminated via selection of a convergence parameter, Γ, which is significantly greater than the energy scales of the system-bath coupling; as described by Dijkstra and Prokhorenko. 57 Elements of the hierarchy which are deep enough to correspond to fluctuations faster than this convergence parameter are assumed to be Markovian. The termination criterion is expressed as…”

Phase-space wavepacket dynamics of internal conversion via conical intersection: Multi-state quantum Fokker-Planck equation approach

“…Internal conversion (IC) of a photoexcited molecule through conical intersection (CI) points plays an important role in photochemical processes, such as ultrafast electronic and vibrational transitions [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16]. Such systems are characterized by adiabatic ground and excited potential energy surfaces (PESs) that are functions of multidimensional reaction coordinates.…”

Quantifying non-Markovianity in underdamped versus overdamped environments and its effect on spectral lineshape

“…34 Assuming a continuum of bath modes with masses, m α , and frequencies, ω α , the distribution of coupling strengths, g α is determined by the spectral density, J(ω). 35,36…”

“…Through a canonical transformation, the vibrational mode of the system is subsumed into the bath degrees of freedom, creating a Brownian oscillator which couples directly to the electronic states of the system and is damped by the motion of the wider environment through the parameter γ. [34][35][36] The system couples to the bath through the operator,V…”

“…14,39 This obeys the fluctuationdissipation theorem, where the imaginary component causes dissipation and the real component is responsible for thermally induced fluctuations. 36,40 The solution to the correlation function is the sum of exponential terms, containing the bosonic Matsubara frequencies, ν k ; k = 0, 1, 2, ..., M , and prefactors, c k , 1,39…”