@article{EhlertKroenerSaalfrank2015,
  author    = {Ehlert, Christopher and Kr{\"o}ner, Dominik and Saalfrank, Peter},
  title     = {A combined quantum chemical/molecular dynamics study of X-ray photoelectron spectra of polyvinyl alcohol using oligomer models},
  series = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy},
  volume    = {199},
  journal   = {Journal of electron spectroscopy and related phenomena : the international journal on theoretical and experimental aspects of electron spectroscopy},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0368-2048},
  doi       = {10.1016/j.elspec.2014.12.007},
  pages     = {38 -- 45},
  year      = {2015},
  abstract  = {X-ray photoelectron spectroscopy (XPS) is a powerful tool for probing the local chemical environment of atoms near surfaces. When applied to soft matter, such as polymers, XPS spectra are frequently shifted and broadened due to thermal atom motion and by interchain interactions. We present a combined quantum mechanical QM/molecular dynamics (MD) simulation of X-ray photoelectron spectra of polyvinyl alcohol (PVA) using oligomer models in order to account for and quantify these effects on the XPS (C1s) signal. In our study, molecular dynamics at finite temperature were performed with a classical forcefield and by ab initio MD (AIMD) using the Car-Parrinello method. Snapshots along, the trajectories represent possible conformers and/or neighbouring environments, with different C1s ionization potentials for individual C atoms leading to broadened XPS peaks. The latter are determined by Delta-Kohn Sham calculations. We also examine the experimental practice of gauging XPS (C1s) signals of alkylic C-atoms in C-containing polymers to the C1s signal of polyethylene. We find that (i) the experimental XPS (C1s) spectra of PVA (position and width) can be roughly represented by single-strand models, (ii) interchain interactions lead to red-shifts of the XPS peaks by about 0.6 eV, and (iii) AIMD simulations match the findings from classical MD semi-quantitatively. Further, (iv) the gauging procedure of XPS (C1s) signals to the values of PE, introduces errors of about 0.5 eV. (C) 2014 Elsevier B.V. All rights reserved.},
  language  = {en}
}
@article{KroenerEhlertSaalfranketal.2011,
  author    = {Kr{\"o}ner, Dominik and Ehlert, Christopher and Saalfrank, Peter and Holl{\"a}nder, Andreas},
  title     = {Ab initio calculations for XPS chemical shifts of poly(vinyl-trifluoroacetate) using trimer models},
  series = {Surface science},
  volume    = {605},
  journal   = {Surface science},
  number    = {15-16},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0039-6028},
  doi       = {10.1016/j.susc.2011.05.021},
  pages     = {1516 -- 1524},
  year      = {2011},
  abstract  = {X-ray photoelectron spectra (XPS) of the polymer poly(vinyl-trifluoroacetate) show C(1s) binding energy shifts which are unusual because they are influenced by atoms which are several bonds away from the probed atom. In this work, the influence of the trifluoroacetate substituent on the 1s ionization potential of the carbon atoms of the polyethylene chain is investigated theoretically using mono-substituted, diad and triad models of trimers representing the polymer. Carbon 1s ionization energies are calculated by the Hartree-Fock theory employing Koopmans' theorem. The influence of the configuration and conformation of the functional groups as well as the degree of substitution are found to be important determinants of XPS spectra. It is further found that the 1s binding energy correlates in a linear fashion, with the total electrostatic potential at the position of the probe atom, and depends not only on nearest neighbor effects. This may have implications for the interpretation of high-resolution XP spectra.},
  language  = {en}
}
@article{GoetzeKroenerBanerjeeetal.2014,
  author    = {Goetze, Jan P. and Kr{\"o}ner, Dominik and Banerjee, Shiladitya and Karasulu, Bora and Thiel, Walter},
  title     = {Carotenoids as a shortcut for chlorophyll Soret-to-Q band energy flow},
  series = {ChemPhysChem : a European journal of chemical physics and physical chemistry},
  volume    = {15},
  journal   = {ChemPhysChem : a European journal of chemical physics and physical chemistry},
  number    = {15},
  publisher = {Wiley-VCH},
  address   = {Weinheim},
  issn      = {1439-4235},
  doi       = {10.1002/cphc.201402233},
  pages     = {3391 -- 3400},
  year      = {2014},
  abstract  = {It is proposed that xanthophylls, and carotenoids in general, may assist in energy transfer from the chlorophyll Soret band to the Q band. Ground-state (1A(g)) and excited-state (1B(u)) optimizations of violaxanthin (Vx) and zeaxanthin (Zx) are performed in an environment mimicking the light-harvesting complex II (LHCII), including the closest chlorophyll b molecule (Chl). Time-dependent density functional theory (TD-DFT, CAM-B3LYP functional) is used in combination with a semi-empirical description to obtain the excited-state geometries, supported by additional DFT/multireference configuration interaction calculations, with and without point charges representing LHCII. In the ground state, Vx and Zx show similar properties. At the 1B(u) minimum, the energy of the Zx 1Bu state is below the Chl Q band, in contrast to Vx. Both Vx and Zx may act as acceptors of Soret-state energy; transfer to the Q band seems to be favored for Vx. These findings suggest that carotenoids may generally mediate Soret-to-Q energy flow in LHCII.},
  language  = {en}
}
@article{Kroener2011,
  author    = {Kr{\"o}ner, Dominik},
  title     = {Chiral distinction by ultrashort laser pulses electron wavepacket dynamics incorporating magnetic interactions},
  series = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory},
  volume    = {115},
  journal   = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory},
  number    = {50},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1089-5639},
  doi       = {10.1021/jp207270s},
  pages     = {14510 -- 14518},
  year      = {2011},
  abstract  = {The qualitative and quantitative distinction of enantiomers is one of the key issues in chemical analysis. In the last years, circular dichroism (CD) has been combined with laser ionization mass spectrometry (LIMS), applying resonance enhanced multiphoton ionization (REMPI) with ultrashort laser pulses. We present theoretical investigations on the CD in the populations of the first electronic excited state of the REMPI process, caused by the interaction of 3-methylcyclopentanone with either left or right circular polarized fs-laser pulses. For this we performed multistate laser driven many electron dynamics based on ab initio electronic structure calculations, namely, TD-CIS(D)/6-311++(2d,2p). For a theoretical description of these experiments, a complete description of the field-dipole correlation is mandatory, including both electric field electric dipole and magnetic field magnetic dipole interactions. The effect of various pulse parameters on the CD are analyzed and compared with experimental results to gain further understanding of the key elements for an optimal distinction of enantiomers.},
  language  = {en}
}
@article{KroenerGaebel2015,
  author    = {Kr{\"o}ner, Dominik and Gaebel, Tina},
  title     = {Circular Dichroism in Mass Spectrometry: Quantum Chemical Investigations for the Differences between (R)-3-Methylcyclopentanone and Its Cation},
  series = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory},
  volume    = {119},
  journal   = {The journal of physical chemistry : A, Molecules, spectroscopy, kinetics, environment \& general theory},
  number    = {34},
  publisher = {American Chemical Society},
  address   = {Washington},
  issn      = {1089-5639},
  doi       = {10.1021/acs.jpca.5b05247},
  pages     = {9167 -- 9177},
  year      = {2015},
  abstract  = {In mass spectrometry enantiomers can be distinguished by multiphoton ionization employing circular polarized laser pulses. The circular dichroism (CD) is detected from the normalized difference in the ion yield after excitation with light of opposite handedness. While there are cases in which fragment and parent ions exhibit the same sign of the CD in the ion yield, several experiments show that they might also differ in sign and magnitude. Supported by experimental observations it has been proposed that the parent ion, once it has been formed, is further excited by the laser, which may result in a change of the CD in the ion yield of the formed fragments compared to the parent ion. To gain a deeper insight in possible excitation pathways we calculated and compared the electronic CD absorption spectra of neutral and cationic (R)-3-methylcyclopentanone, applying density functional theory. In addition, electron wavepacket dynamics were used to compare the CD of one- and two-photon transitions. Our results support the proposed subsequent excitation of the parent ion as a possible origin of the difference of the CD in the ion yield between parent ion and fragments.},
  language  = {en}
}
@article{KroenerKruegerThesen2011,
  author    = {Kr{\"o}ner, Dominik and Kr{\"u}ger, Hartmut and Thesen, Manuel W.},
  title     = {Electronic structure calculations for Hole-Transporting Triphenylamine Derivatives in Polymer Light-Emitting Diodes},
  series = {Macromolecular theory and simulations},
  volume    = {20},
  journal   = {Macromolecular theory and simulations},
  number    = {9},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  issn      = {1022-1344},
  doi       = {10.1002/mats.201100016},
  pages     = {790 -- 805},
  year      = {2011},
  abstract  = {Hole-transporting polymers based on polyethene-triphenylamine derivatives are investigated with respect to their UV/Vis spectra. Two substituents, N-phenyl-1-naphthylamine and carbazole, are examined as their respective polymer light-emitting diodes (PLEDs) show very different luminous efficiencies. In order to identify the origin of these phenomena electronic structure calculations based on TD-DFT were performed using monomer models of the hole-transporting polymers. In experiment these hole-transporting polymers show very specific differences in their absorption and emission (fluorescence and phosphorescence) spectra. The analysis of the simulated absorption and emission spectra, the MOs as well as the ground and excited state geometries give explanations for the different optical performances of the corresponding PLEDs.},
  language  = {en}
}
@article{Kroener2015,
  author    = {Kr{\"o}ner, Dominik},
  title     = {Laser-driven electron dynamics for circular dichroism in mass spectrometry},
  series = {Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies},
  volume    = {29},
  journal   = {Physical chemistry, chemical physics : PCCP ; a journal of European Chemical Societies},
  number    = {17},
  publisher = {The Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/C5CP02193F},
  pages     = {19643 -- 19655},
  year      = {2015},
  abstract  = {The distinction of enantiomers is a key aspect of chemical analysis. In mass spectrometry the distinction of enantiomers has been achieved by ionizing the sample with circularly polarized laser pulses and comparing the ion yields for light of opposite handedness. While resonant excitation conditions are expected to be most efficient, they are not required for the detection of a circular dichroism (CD) in the ion yield. However, the prediction of the size and sign of the circular dichroism becomes challenging if non-resonant multiphoton excitations are used to ionize the sample. Employing femtosecond laser pulses to drive electron wavepacket dynamics based on ab initio calculations, we attempt to reveal underlying mechanisms that determine the CD under non-resonant excitation conditions. Simulations were done for (R)-1,2-propylene oxide, using time-dependent configuration interaction singles with perturbative doubles (TD-CIS(D)) and the aug-cc-pVTZ basis set. Interactions between the electric field and the electric dipole and quadrupole as well as between the magnetic field and the magnetic dipole were explicitly accounted for. The ion yield was determined by treating states above the ionization potential as either stationary or non-stationary with energy-dependent lifetimes based on an approved heuristic approach. The observed population dynamics do not allow for a simple interpretation, because of highly non-linear interactions. Still, the various transition pathways are governed by resonant enantiospecific n-photon excitation, with preferably high transition dipole moments, which eventually dominate the CD in the ionized population.},
  language  = {en}
}
@misc{Kroener2015,
  author    = {Kr{\"o}ner, Dominik},
  title     = {Laser-driven electron dynamics for circular dichroism in mass spectrometry},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-82109},
  year      = {2015},
  abstract  = {The distinction of enantiomers is a key aspect of chemical analysis. In mass spectrometry the distinction of enantiomers has been achieved by ionizing the sample with circularly polarized laser pulses and comparing the ion yields for light of opposite handedness. While resonant excitation conditions are expected to be most efficient, they are not required for the detection of a circular dichroism (CD) in the ion yield. However, the prediction of the size and sign of the circular dichroism becomes challenging if non-resonant multiphoton excitations are used to ionize the sample. Employing femtosecond laser pulses to drive electron wavepacket dynamics based on ab initio calculations, we attempt to reveal underlying mechanisms that determine the CD under non-resonant excitation conditions. Simulations were done for (R)-1,2-propylene oxide, using time-dependent configuration interaction singles with perturbative doubles (TD-CIS(D)) and the aug-cc-pVTZ basis set. Interactions between the electric field and the electric dipole and quadrupole as well as between the magnetic field and the magnetic dipole were explicitly accounted for. The ion yield was determined by treating states above the ionization potential as either stationary or non-stationary with energy-dependent lifetimes based on an approved heuristic approach. The observed population dynamics do not allow for a simple interpretation, because of highly non-linear interactions. Still, the various transition pathways are governed by resonant enantiospecific n-photon excitation, with preferably high transition dipole moments, which eventually dominate the CD in the ionized population.},
  language  = {en}
}
@article{KroenerGoetze2012,
  author    = {Kr{\"o}ner, Dominik and G{\"o}tze, Jan Philipp},
  title     = {Modeling of a violaxanthin-chlorophyll b chromophore pair in its LHCII environment using CAM-B3LYP},
  series = {Journal of photochemistry and photobiology : B, Biology},
  volume    = {109},
  journal   = {Journal of photochemistry and photobiology : B, Biology},
  number    = {2},
  publisher = {Elsevier},
  address   = {Lausanne},
  issn      = {1011-1344},
  doi       = {10.1016/j.jphotobiol.2011.12.007},
  pages     = {12 -- 19},
  year      = {2012},
  abstract  = {Collecting energy for photosystem II is facilitated by several pigments, xanthophylls and chlorophylls, embedded in the light harvesting complex II (LHCII). One xanthophyll, violaxanthin (Vio), is loosely bound at a site close to a chlorophyll b (Chl). No final answer has yet been found for the role of this specific xanthophyll. We study the electronic structure of Vio in the presence of Chl and under the influence of the LHCII environment, represented by a point charge field (PCF). We compare the capability of the long range corrected density functional theory (DFT) functional CAM-B3LYP to B3LYP for the modeling of the UV/vis spectrum of the Vio + Chl pair. CAM-B3LYP was reported to allow for a very realistic reproduction of bond length alternation of linear polyenes, which has considerable impact on the carotenoid structure and spectrum. To account for the influence of the LHCII environment, the chromophore geometries are optimized using an ONIOM(DFT/6-31G(d):PM6) scheme. Our calculations show that the energies of the locally excited states are almost unaffected by the presence of the partner chromophore or the PCF. There are, however, indications for excitonic coupling of the Chl Soret band and Vio. We propose that Vio may accept energy from blue-light excited Chl.},
  language  = {en}
}
@article{KlaumuenzerKroenerLischkaetal.2012,
  author    = {Klaum{\"u}nzer, Bastian and Kr{\"o}ner, Dominik and Lischka, Hans and Saalfrank, Peter},
  title     = {Non-adiabatic excited state dynamics of riboflavin after photoexcitation},
  series = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  volume    = {14},
  journal   = {Physical chemistry, chemical physics : a journal of European Chemical Societies},
  number    = {24},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1463-9076},
  doi       = {10.1039/c2cp40978j},
  pages     = {8693 -- 8702},
  year      = {2012},
  abstract  = {Flavins are chromophores in light-gated enzymes and therefore central in many photobiological processes. To unravel the optical excitation process as the initial, elementary step towards signal transduction, detailed ultrafast (femtosecond) experiments probing the photo-activation of flavins have been carried out recently [Weigel et al., J. Phys. Chem. B, 2011, 115, 3656-3680.]. The present paper contributes to a further understanding and interpretation of these experiments by studying the post-excitation vibrational dynamics of riboflavin (RF) and microsolvated riboflavin, RF center dot 4H(2)O, using first principles non-adiabatic molecular dynamics. By analyzing the characteristic atom motions and calculating time-resolved stimulated emission spectra following pi pi* excitation, it is found that after optical excitation C-N and C-C vibrations in the isoalloxazine rings of riboflavin set in. The Franck-Condon (vertically excited) state decays within about 10 fs, in agreement with experiment. Anharmonic coupling leads to Intramolecular Vibrational energy Redistribution (IVR) on the timescale of about 80-100 fs, first to (other) C-C stretching modes of the isoalloxazine rings, then by energy spread over the whole molecule, including low-frequency in-plane modes. The IVR is accompanied by a red-shift and broadening of the emission spectrum. When RF is microsolvated with four water molecules, an overall redshift of optical spectra by about 20 nm is observed but the relaxation dynamics is only slightly affected. For several trajectories, a tendency for hydrogen transfer from water to flavin-nitrogen (N-5) was found.},
  language  = {en}
}