@unpublished{PetersenLindnerMitric2018,
  author    = {Petersen, Jens and Lindner, Joachim O. and Mitric, Roland},
  title     = {Ultrafast Photodynamics of Glucose},
  series = {Journal of Physical Chemistry B},
  journal   = {Journal of Physical Chemistry B},
  doi       = {10.1021/acs.jpcb.7b08602},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-159155},
  year      = {2018},
  abstract  = {We have investigated the photodynamics of \(\beta\)-D-glucose employing our field-induced surface hopping method (FISH), which allows us to simulate the coupled electron-nuclear dynamics, including explicitly nonadiabatic effects and light-induced excitation. Our results reveal that from the initially populated S\(_{1}\) and S\(_{2}\) states, glucose returns nonradiatively to the ground state within about 200 fs. This takes place mainly via conical intersections (CIs) whose geometries in most cases involve the elongation of a single O-H bond, while in some instances ring-opening due to dissociation of a C-O bond is observed. Experimentally, excitation to a distinct excited electronic state is improbable due to the presence of a dense manifold of states bearing similar oscillator strengths. Our FISH simulations explicitly including a UV laser pulse of 6.43 eV photon energy reveals that after initial excitation the population is almost equally spread over several close-lying electronic states. This is followed by a fast nonradiative decay on the time scale of 100-200 fs, with the final return to the ground state proceeding via the S\(_{1}\) state through the same types of CIs as observed in the field-free simulations.},
  language  = {en}
}
@article{HocheSchulzDietrichetal.2019,
  author    = {Hoche, Joscha and Schulz, Alexander and Dietrich, Lysanne Monika and Humeniuk, Alexander and Stolte, Matthias and Schmidt, David and Brixner, Tobias and W{\"u}rthner, Frank and Mitric, Roland},
  title     = {The origin of the solvent dependence of fluorescence quantum yields in dipolar merocyanine dyes},
  series = {Chemical Science},
  volume    = {10},
  journal   = {Chemical Science},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-198707},
  pages     = {11013},
  year      = {2019},
  abstract  = {Fluorophores with high quantum yields are desired for a variety of applications. Optimization of promising chromophores requires an understanding of the non-radiative decay channels that compete with the emission of photons. We synthesized a new derivative of the famous laser dye 4-dicyanomethylen-2-methyl-6-p-dimethylaminostyryl-4H-pyran (DCM),i.e., merocyanine 4-(dicyanomethylene)-2-tert-butyl-6-[3-(3-butyl-benzothiazol-2-ylidene)1-propenyl]-4H-pyran (DCBT). We measured fluorescence lifetimes and quantum yields in a variety of solvents and found a trend opposite to the energy gap law.This motivated a theoretical investigation into the possible non-radiative decay channels. We propose that a barrier to a conical intersection exists that is very sensitive to the solvent polarity. The conical intersection is characterized by a twisted geometry which allows a subsequent photoisomerization. Transient absorption measurements confirmed the formation of a photoisomer in unpolar solvents, while the measurements of fluorescence quantum yields at low temperature demonstrated the existence of an activation energy barrier.},
  language  = {en}
}
@unpublished{HocheSchmittHumeniuketal.2017,
  author    = {Hoche, Joscha and Schmitt, Hans-Christian and Humeniuk, Alexander and Fischer, Ingo and Mitrić, Roland and R{\"o}hr, Merle I. S.},
  title     = {The mechanism of excimer formation: an experimental and theoretical study on the pyrene dimer},
  series = {Physical Chemistry Chemical Physics},
  journal   = {Physical Chemistry Chemical Physics},
  doi       = {10.1039/C7CP03990E},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-159656},
  year      = {2017},
  abstract  = {The understanding of excimer formation in organic materials is of fundamental importance, since excimers profoundly influence their functional performance in applications such as light-harvesting, photovoltaics or organic electronics. We present a joint experimental and theoretical study of the ultrafast dynamics of excimer formation in the pyrene dimer in a supersonic jet, which is the archetype of an excimer forming system. We perform simulations of the nonadiabatic photodynamics in the frame of TDDFT that reveal two distinct excimer formation pathways in the gas-phase dimer. The first pathway involves local excited state relaxation close to the initial Franck-Condon geometry that is characterized by a strong excitation of the stacking coordinate exhibiting damped oscillations with a period of 350 fs that persist for several picoseconds. The second excimer forming pathway involves large amplitude oscillations along the parallel shift coordinate with a period of ≈900 fs that after intramolecular vibrational energy redistribution leads to the formation of a perfectly stacked dimer. The electronic relaxation within the excitonic manifold is mediated by the presence of intermolecular conical intersections formed between fully delocalized excitonic states. Such conical intersections may generally arise in stacked π-conjugated aggregates due to the interplay between the long-range and short-range electronic coupling. The simulations are supported by picosecond photoionization experiments in a supersonic jet that provide a time-constant for the excimer formation of around 6-7 ps, in good agreement with theory. Finally, in order to explore how the crystal environment influences the excimer formation dynamics we perform large scale QM/MM nonadiabatic dynamics simulations on a pyrene crystal in the framework of the long-range corrected tight-binding TDDFT. In contrast to the isolated dimer, the excimer formation in the crystal follows a single reaction pathway in which the initially excited parallel slip motion is strongly damped by the interaction with the surrounding molecules leading to the slow excimer stabilization on a picosecond time scale.},
  language  = {en}
}
@article{HocheSchmittHumeniuketal.2017,
  author    = {Hoche, Joscha and Schmitt, Hans-Christian and Humeniuk, Alexander and Fischer, Ingo and Mitrić, Roland and R{\"o}hr, Merle I. S.},
  title     = {The mechanism of excimer formation: an experimental and theoretical study on the pyrene dimer},
  series = {Physical Chemistry Chemical Physics},
  volume    = {19},
  journal   = {Physical Chemistry Chemical Physics},
  number    = {36},
  doi       = {10.1039/C7CP03990E},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-159514},
  pages     = {25002-25015},
  year      = {2017},
  abstract  = {The understanding of excimer formation in organic materials is of fundamental importance, since excimers profoundly influence their functional performance in applications such as light-harvesting, photovoltaics or organic electronics. We present a joint experimental and theoretical study of the ultrafast dynamics of excimer formation in the pyrene dimer in a supersonic jet, which is the archetype of an excimer forming system. We perform simulations of the nonadiabatic photodynamics in the frame of TDDFT that reveal two distinct excimer formation pathways in the gas-phase dimer. The first pathway involves local excited state relaxation close to the initial Franck-Condon geometry that is characterized by a strong excitation of the stacking coordinate exhibiting damped oscillations with a period of 350 fs that persist for several picoseconds. The second excimer forming pathway involves large amplitude oscillations along the parallel shift coordinate with a period of ≈900 fs that after intramolecular vibrational energy redistribution leads to the formation of a perfectly stacked dimer. The electronic relaxation within the excitonic manifold is mediated by the presence of intermolecular conical intersections formed between fully delocalized excitonic states. Such conical intersections may generally arise in stacked π-conjugated aggregates due to the interplay between the long-range and short-range electronic coupling. The simulations are supported by picosecond photoionization experiments in a supersonic jet that provide a time-constant for the excimer formation of around 6-7 ps, in good agreement with theory. Finally, in order to explore how the crystal environment influences the excimer formation dynamics we perform large scale QM/MM nonadiabatic dynamics simulations on a pyrene crystal in the framework of the long-range corrected tight-binding TDDFT. In contrast to the isolated dimer, the excimer formation in the crystal follows a single reaction pathway in which the initially excited parallel slip motion is strongly damped by the interaction with the surrounding molecules leading to the slow excimer stabilization on a picosecond time scale.},
  language  = {en}
}
@article{MuessigLisinetskayaDewhurstetal.2020,
  author    = {Muessig, Jonas H. and Lisinetskaya, Polina and Dewhurst, Rian D. and Bertermann, R{\"u}diger and Thaler, Melanie and Mitric, Roland and Braunschweig, Holger},
  title     = {Tetraiododiborane(4) (B\(_2\)I\(_4\)) is a Polymer based on sp\(^3\) Boron in the Solid State},
  series = {Angewandte Chemie International Edition},
  volume    = {59},
  journal   = {Angewandte Chemie International Edition},
  doi       = {10.1002/anie.201913590},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-209428},
  pages     = {5531-5535},
  year      = {2020},
  abstract  = {Herein we present the first solid-state structures of tetraiododiborane(4) (B\(_2\)I\(_4\)), which was long believed to exist in all phases as discrete molecules with planar, tricoordinate boron atoms, like the lighter tetrahalodiboranes(4) B\(_2\)F\(_4\), B\(_2\)Cl\(_4\), and B\(_2\)Br\(_4\). Single-crystal X-ray diffraction, solid-state NMR, and IR measurements indicate that B\(_2\)I\(_4\) in fact exists as two different polymeric forms in the solid state, both of which feature boron atoms in tetrahedral environments. DFT calculations are used to simulate the IR spectra of the solution and solid-state structures, and these are compared with the experimental spectra.},
  language  = {en}
}
@unpublished{HumeniukBužančićHocheetal.2020,
  author    = {Humeniuk, Alexander and Bužančić, Margarita and Hoche, Joscha and Cerezo, Javier and Mitric, Roland and Santoro, Fabrizio and Bonačić-Koutecky, Vlasta},
  title     = {Predicting fluorescence quantum yields for molecules in solution: A critical assessment of the harmonic approximation and the choice of the lineshape function},
  series = {The Journal of Chemical Physics},
  journal   = {The Journal of Chemical Physics},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-199305},
  year      = {2020},
  abstract  = {For the rational design of new fluorophores, reliable predictions of fluorescence quantum yields from first principles would be of great help. However, efficient computational approaches for predicting transition rates usually assume that the vibrational structure is harmonic. While the harmonic approximation has been used successfully to predict vibrationally resolved spectra and radiative rates, its reliability for non-radiative rates is much more questionable. Since non-adiabatic transitions convert large amounts of electronic energy into vibrational energy, the highly excited final vibrational states deviate greatly from harmonic oscillator eigenfunctions. We employ a time-dependent formalism to compute radiative and non-radiative rates for transitions and study the dependence on model parameters. For several coumarin dyes we compare different adiabatic and vertical harmonic models (AS, ASF, AH, VG, VGF, VH), in order to dissect the importance of displacements, frequency changes and Duschinsky rotations. In addition we analyze the effect of different broadening functions (Gaussian, Lorentzian or Voigt). Moreover, to assess the qualitative influence of anharmonicity on the internal conversion rate, we develop a simplified anharmonic model. We adress the reliability of these models considering the potential errors introduced by the harmonic approximation and the phenomenological width of the broadening function.},
  language  = {en}
}
@article{WohlgemuthMitric2016,
  author    = {Wohlgemuth, Matthias and Mitric, Roland},
  title     = {Photochemical Chiral Symmetry Breaking in Alanine},
  series = {Journal of Physical Chemistry A},
  volume    = {45},
  journal   = {Journal of Physical Chemistry A},
  number    = {120},
  doi       = {10.1021/acs.jpca.6b07611},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-158557},
  pages     = {8976-8982},
  year      = {2016},
  abstract  = {We introduce a general theoretical approach for the simulation of photochemical dynamics under the influence of circularly polarized light to explore the possibility of generating enantiomeric enrichment through polarized-light-selective photochemistry. The method is applied to the simulation of the photolysis of alanine, a prototype chiral amino acid. We show that a systematic enantiomeric enrichment can be obtained depending on the helicity of the circularly polarized light that induces the excited-state photochemistry of alanine. By analyzing the patterns of the photoinduced fragmentation of alanine we find an inducible enantiomeric enrichment up to 1.7\%, which is also in good correspondence to the experimental findings. Our method is generally applicable to complex systems and might serve to systematically explore the photochemical origin of homochirality.},
  language  = {en}
}
@unpublished{LindnerSultangaleevaRoehretal.2019,
  author    = {Lindner, Joachim O. and Sultangaleeva, Karina and R{\"o}hr, Merle I. S. and Mitric, Roland},
  title     = {metaFALCON: A program package for automatic sampling of conical intersection seams using multistate metadynamics},
  series = {Journal of Chemical Theory and Computation},
  journal   = {Journal of Chemical Theory and Computation},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-199258},
  year      = {2019},
  abstract  = {The multistate metadynamics for automatic exploration of conical intersection seams and systematic location of minimum energy crossing points in molecular systems and its implementation into the software package metaFALCON is presented. Based on a locally modified energy gap between two Born-Oppenheimer electronic states as a collective variable, multistate metadynamics trajectories are driven toward an intersection point starting from an arbitrary ground state geometry and are subsequently forced to explore the conical intersection seam landscape. For this purpose, an additional collective variable capable of distinguishing structures within the seam needs to be defined and an additional bias is introduced into the off-diagonal elements of an extended (multistate) electronic Hamiltonian. We demonstrate the performance of the algorithm on the examples of the 1,3-butadiene, benzene, and 9H-adenine molecules, where multiple minimum energy crossing points could be systematically located using the Wiener number or Cremer-Pople parameters as collective variables. Finally, with the example of 9H-adenine, we show that the multistate metadynamics potential can be used to obtain a global picture of a conical intersection seam. Our method can be straightforwardly connected with any ab initio or semiempirical electronic structure theory that provides energies and gradients of the respective electronic states and can serve for systematic elucidation of the role of conical intersections in the photophysics and photochemistry of complex molecular systems, thus complementing nonadiabatic dynamics simulations.},
  language  = {en}
}
@article{LisinetskayaRoehrMitrić2016,
  author    = {Lisinetskaya, Polina and R{\"o}hr, Merle I. S. and Mitrić, Roland},
  title     = {First-principles simulation of light propagation and exciton dynamics in metal cluster nanostructures},
  series = {Applied Physics B},
  volume    = {122},
  journal   = {Applied Physics B},
  number    = {6},
  issn      = {0946-2171},
  doi       = {10.1007/s00340-016-6436-6},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-159193},
  pages     = {175},
  year      = {2016},
  abstract  = {We present a theoretical approach for the simulation of the electric field and exciton propagation in ordered arrays constructed of molecular-sized noble metal clusters bound to organic polymer templates. In order to describe the electronic coupling between individual constituents of the nanostructure we use the ab initio parameterized transition charge method which is more accurate than the usual dipole-dipole coupling. The electronic population dynamics in the nanostructure under an external laser pulse excitation is simulated by numerical integration of the time-dependent Schrodinger equation employing the fully coupled Hamiltonian. The solution of the TDSE gives rise to time-dependent partial point charges for each subunit of the nanostructure, and the spatio-temporal electric field distribution is evaluated by means of classical electrodynamics methods. The time-dependent partial charges are determined based on the stationary partial and transition charges obtained in the framework of the TDDFT. In order to treat large plasmonic nanostructures constructed of many constituents, the approximate self-consistent iterative approach presented in (Lisinetskaya and Mitric in Phys Rev B 89:035433, 2014) is modified to include the transition-charge-based interaction. The developed methods are used to study the optical response and exciton dynamics of Ag-3(+) and porphyrin-Ag-4 dimers. Subsequently, the spatio-temporal electric field distribution in a ring constructed of ten porphyrin-Ag-4 subunits under the action of circularly polarized laser pulse is simulated. The presented methodology provides a theoretical basis for the investigation of coupled light-exciton propagation in nanoarchitectures built from molecular size metal nanoclusters in which quantum confinement effects are important.},
  language  = {en}
}
@unpublished{RoederHumeniukGiegerichetal.2017,
  author    = {R{\"o}der, Anja and Humeniuk, Alexander and Giegerich, Jens and Fischer, Ingo and Poisson, Lionel and Mitric, Roland},
  title     = {Femtosecond Time-Resolved Photoelectron Spectroscopy of the Benzyl Radical},
  series = {Physical Chemistry Chemical Physics},
  journal   = {Physical Chemistry Chemical Physics},
  doi       = {10.1039/C7CP01437F},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-159474},
  year      = {2017},
  abstract  = {We present a joint experimental and computational study of the nonradiative deactivation of the benzyl radical, C\(_7\)H\(_7\) after UV excitation. Femtosecond time-resolved photoelectron imaging was applied to investigate the photodynamics of the radical. The experiments were accompanied by excited state dynamics simulations using surface hopping. Benzyl has been excited at 265 nm into the D-band (\(\pi\pi^*\)) and the dynamics was probed using probe wavelengths of 398 nm or 798 nm. With 398 nm probe a single time constant of around 70-80 fs was observed. When the dynamics was probed at 798 nm, a second time constant \(\tau_2\)=1.5 ps was visible. It is assigned to further non-radiative deactivation to the lower-lying D\(_1\)/D\(_2\) states.},
  language  = {en}
}