@article{EhlertGuehrSaalfrank2018,
  author    = {Ehlert, Christopher and G{\"u}hr, Markus and Saalfrank, Peter},
  title     = {An efficient first principles method for molecular pump-probe NEXAFS spectra},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {149},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {14},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.5050488},
  pages     = {13},
  year      = {2018},
  abstract  = {Pump-probe near edge X-ray absorption fine structure (PP-NEXAFS) spectra of molecules offer insight into valence-excited states, even if optically dark. In PP-NEXAFS spectroscopy, the molecule is "pumped" by UV or visible light enforcing a valence excitation, followed by an X-ray "probe" exciting core electrons into (now) partially empty valence orbitals. Calculations of PP-NEXAFS have so far been done by costly, correlated wavefunction methods which are not easily applicable to medium-sized or large molecules. Here we propose an efficient, first principles method based on density functional theory in combination with the transition potential and Delta SCF methodology (TP-DFT/Delta SCF) to compute molecular ground state and PP-NEXAFS spectra. We apply the method to n ->pi* pump/O-K-edge NEXAFS probe spectroscopy of thymine (for which both experimental and other theoretical data exist) and to n -> pi* or pi -> pi* pump/N-K-edge NEXAFS probe spectroscopies of trans-and cis-azobenzene. Published by AIP Publishing.},
  language  = {en}
}
@article{MayerPicconiRobinsonetal.2022,
  author    = {Mayer, Dennis and Picconi, David and Robinson, Matthew S. and G{\"u}hr, Markus},
  title     = {Experimental and theoretical gas-phase absorption spectra of thionated uracils},
  series = {Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature},
  volume    = {558},
  journal   = {Chemical physics : a journal devoted to experimental and theoretical research involving problems of both a chemical and physical nature},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0301-0104},
  doi       = {10.1016/j.chemphys.2022.111500},
  pages     = {9},
  year      = {2022},
  abstract  = {We present a comparative study of the gas-phase UV spectra of uracil and its thionated counterparts (2-thiouracil, 4-thiouracil and 2,4-dithiouracil), closely supported by time-dependent density functional theory calculations to assign the transitions observed. We systematically discuss pure gas-phase spectra for the (thio)uracils in the range of 200-400 nm (similar to 3.2-6.4 eV), and examine the spectra of all four species with a single theoretical approach. We note that specific vibrational modelling is needed to accurately determine the spectra across the examined wavelength range, and systematically model the transitions that appear at wavelengths shorter than 250 nm. Additionally, we find in the cases of 2-thiouracil and 2,4-dithiouracil, that the gas-phase spectra deviate significantly from some previously published solution-phase spectra, especially those collected in basic environments.},
  language  = {en}
}
@article{WolfHolzmeierWagneretal.2017,
  author    = {Wolf, Thomas J. A. and Holzmeier, Fabian and Wagner, Isabella and Berrah, Nora and Bostedt, Christoph and Bozek, John and Bucksbaum, Phil and Coffee, Ryan and Cryan, James and Farrell, Joe and Feifel, Raimund and Martinez, Todd J. and McFarland, Brian and Mucke, Melanie and Nandi, Saikat and Tarantelli, Francesco and Fischer, Ingo and G{\"u}hr, Markus},
  title     = {Observing Femtosecond Fragmentation Using Ultrafast X-ray-Induced Auger Spectra},
  series = {Applied sciences},
  volume    = {7},
  journal   = {Applied sciences},
  number    = {7},
  publisher = {MDPI},
  address   = {Basel},
  issn      = {2076-3417},
  doi       = {10.3390/app7070681},
  pages     = {11},
  year      = {2017},
  abstract  = {Molecules often fragment after photoionization in the gas phase. Usually, this process can only be investigated spectroscopically as long as there exists electron correlation between the photofragments. Important parameters, like their kinetic energy after separation, cannot be investigated. We are reporting on a femtosecond time-resolved Auger electron spectroscopy study concerning the photofragmentation dynamics of thymine. We observe the appearance of clearly distinguishable signatures from thymines neutral photofragment isocyanic acid. Furthermore, we observe a time-dependent shift of its spectrum, which we can attribute to the influence of the charged fragment on the Auger electron. This allows us to map our time-dependent dataset onto the fragmentation coordinate. The time dependence of the shift supports efficient transformation of the excess energy gained from photoionization into kinetic energy of the fragments. Our method is broadly applicable to the investigation of photofragmentation processes.},
  language  = {en}
}
@article{WolfSanchezYangetal.2019,
  author    = {Wolf, Thomas J. A. and Sanchez, David M. and Yang, J. and Parrish, R. M. and Nunes, J. P. F. and Centurion, M. and Coffee, R. and Cryan, J. P. and G{\"u}hr, Markus and Hegazy, Kareem and Kirrander, Adam and Li, R. K. and Ruddock, J. and Shen, Xiaozhe and Vecchione, T. and Weathersby, S. P. and Weber, Peter M. and Wilkin, K. and Yong, Haiwang and Zheng, Q. and Wang, X. J. and Minitti, Michael P. and Martinez, Todd J.},
  title     = {The photochemical ring-opening of 1,3-cyclohexadiene imaged by ultrafast electron diffraction},
  series = {Nature chemistry},
  volume    = {11},
  journal   = {Nature chemistry},
  number    = {6},
  publisher = {Nature Publ. Group},
  address   = {London},
  issn      = {1755-4330},
  doi       = {10.1038/s41557-019-0252-7},
  pages     = {504 -- 509},
  year      = {2019},
  abstract  = {The ultrafast photoinduced ring-opening of 1,3-cyclohexadiene constitutes a textbook example of electrocyclic reactions in organic chemistry and a model for photobiological reactions in vitamin D synthesis. Although the relaxation from the photoexcited electronic state during the ring-opening has been investigated in numerous studies, the accompanying changes in atomic distance have not been resolved. Here we present a direct and unambiguous observation of the ring-opening reaction path on the femtosecond timescale and subangstrom length scale using megaelectronvolt ultrafast electron diffraction. We followed the carbon-carbon bond dissociation and the structural opening of the 1,3-cyclohexadiene ring by the direct measurement of time-dependent changes in the distribution of interatomic distances. We observed a substantial acceleration of the ring-opening motion after internal conversion to the ground state due to a steepening of the electronic potential gradient towards the product minima. The ring-opening motion transforms into rotation of the terminal ethylene groups in the photoproduct 1,3,5-hexatriene on the subpicosecond timescale.},
  language  = {en}
}