Dr. Alexander Schubert

Dr. Alexander Schubert

Dr. Alexander Schubert
Image: Dr. Alexander Schubert

Short CV

  • Since 09/2018: Postdoctoral Researcher in the group of Prof. Stefanie Gräfe,
    Friedrich-Schiller Universität Jena, Germany.
  • 01/2016-08/2018: Postdoctoral Researcher in the group of Prof. Eitan Geva,
    University of Michigan, MI,
    and Senior Research Associate in the group of Prof. Barry D. Dunietz,
    Kent State University, OH, USA;
    supported by a Fellowship of the Institute for Complex Adaptive Matter (www.icam-i2cam.org).
  • 01/2012-11/2015: Postdoctoral Researcher in the group of Prof. Christoph Meier,
    LCAR, IRSAMC, Université Toulouse III – Paul Sabatier, France;
    partially supported by a DFG Research Fellowship.
  • 2008-2012: PhD in Theoretical Chemistry in the group of Prof. Volker Engel,
    Julius-Maximilians Universität Würzburg, Germany,
    Thesis: “Coherent and dissipative wave packet dynamics and time-resolved spectroscopy: from diatomic molecules to molecular aggregates”,  (urn:nbn:de:bvb:20-opus-74258)
    awarded with the faculty price by the faculty of chemistry and pharmacy.
  • 2003-2008: Diploma in Physics (M.Sc. Equiv) in the group of Prof. Christian Spielmann,
    Julius-Maximilians Universität Würzburg, Germany

Research Topics

  • Quantum Dynamics
  • Non-linear Spectroscopy
  • Charge and Energy Transfer
  • Organic Photovoltaics
  • Photosynthesis

My primary research interest lies in the fields of molecular quantum dynamics and non-linear spectroscopy. In particular, I focus on intermolecular energy, charge, and spin transfer processes, which are of central importance in various biological systems and optoelectronic devices, such as photosynthetic complexes and photovoltaic applications.

By means of first-principle quantum-chemical calculations and time-dependent quantum-mechanical simulations of such processes and their spectroscopic signatures, I aim to identify the essential molecular influence factors that either impede or enhance transfer efficiencies. A primary research objective is to provide precise guidelines for an improved rational design of functional materials. On a more fundamental level, I also investigate the potential of non-linear spectroscopic techniques to reveal sensitive dynamical information about photoactive systems and their molecular environment.

In both areas, transfer processes and spectroscopy, a rigorous treatment of quantum coherences is of paramount importance. Therefore, new simulation techniques are developed and employed, addressing quantum dynamics beyond the perturbative and secular approximation.

Methods

Besides direct quantum-dynamical simulations, I’m applying mixed quantum-classical methods, such as the Ehrenfest Mean-Field (MF) method or Surface Hopping (FSSH) approaches, to electronic and vibrational degrees of freedom. Transfer and transport is simulated by means of kinetic models based on the Generalized Quantum Master Equation (GQME) and Fermi’s golden rule (FGR) approaches. Electronic structure information is obtained from time-dependent density functional theory employing polarization-consistent screened range-separated hybrid functionals (SRSH-PCM).

Mixed quantum-classical methods based on MD simulations were developed and employed to study energy flux, vibrational relaxation, and decoherence in a protein system beyond the weak-coupling and secular approximation. After UV-photolysis from a heme iron, a carbon monoxide is in coherently excited vibrational states, which are non-adiabatically coupled (blue and red arrows) through the protein environment. The vibrational-surface-hopping approach revealed the energy flow to protein residues with atomistic resolution. Physical Review A, 92, p. 053402 (2015), https://doi.org/10.1103/PhysRevA.92.053402

Mixed quantum-classical methods based on MD simulations Image: Dr. Alexander Schubert

Publications

2019 Show content
  • Huseyin Aksu, Alexander Schubert, Eitan Geva, and Barry D. Dunietz: Explaining spectral asymmetries and excitonic characters of the core pigment pairs in the bacterial reaction center using a screened range-separated hybrid functional, J. Phys. Chem B, (2019), 10.1021/acs.jpcb.9b07646

  • Ellen Mulvihill, Xing Gao, Yudan Liu, Alexander Schubert, Barry D. Dunietz, and Eitan Geva: Combining the mapping Hamiltonian linearized  semiclassical approach withthe generalized quantum master equation to simulate electronically nonadiabatic molecular dynamicsJ. Chem. Phys., 151, 074103 (2019),  10.1063/1.5110891

  • Yin Song, Alexander Schubert, Elizabeth Maret, Ryan K. Burdick, Barry D. Dunietz, Eitan Geva, and Jennifer P. Ogilvie: Vibronic structure of photosynthetic pigments probed by polarized two-dimensional electronic spectroscopy and ab initio calculations, Chem. Sci., 10, p.8143, (2019),  https://doi.org/10.1039/C9SC02329A

  • Ellen Mulvihill, Alexander Schubert, Xiang Sun, Barry D. Dunietz, and Eitan Geva: A modified approach for simulating electronically nonadiabatic dynamics via the generalized quantum master equation, J. Chem. Phys., 150, p. 034101 (2019). https://doi.org/10.1063/1.5055756

2018 Show content
  • Alexei A. Kananenka, Xiang Sun, Alexander Schubert, Barry D. Dunietz and Eitan Geva: A comparative study of different methods for calculating electronic transition rates, J. Chem. Phys., Special Topic: Nuclear Quantum Effects, 148, p. 102304 (2018).
    http://dx.doi.org/10.1063/1.4989509
2017 Show content
  • Buddhadev Maiti, Alexander Schubert, Sunandan Sarkar, Srijana Bhandari, Kunlun Wang, Zhe Li, Eitan Geva, Robert J. Twieg, and Barry D. Dunietz: Enhancing charge mobilities in organic semiconductors by selective fluorination: a design approach based on a quantum mechanical perspective, Chem. Sci., 8, p. 6947 (2017). http://doi.org/10.1039/C7SC02491F
2016 Show content
  • Alexander Schubert, Cyril Falvo, Christoph Meier: Mixed quantum-classical simulation of the vibrational relaxation of photolyzed carbon monoxide in a hemoprotein, J. Chem. Phys., 145, p. 054108 (2016). http://dx.doi.org/10.1063/1.4959859

2015 Show content
  • Alexander Schubert, Cyril Falvo, and Christoph Meier: Vibrational-coherence measurement of nonequilibrium quantum systems by four-wave mixing, Phys. Rev. A, 92, p. 053402 (2015).
    https://doi.org/10.1103/PhysRevA.92.053402

2014 Show content
  • Volker Settels, Alexander Schubert, Maxim Tafipolski, Wenlan Liu, Vera Stehr, Anna K. Topczak, Jens Pflaum, Carsten Deibel, Reinhold F. Fink, Volker Engel, and Bernd Engels: Identification of ultrafast relaxation processes as a major reason for inefficient diffusion in perylene-based organic semiconductors, J. Am. Chem. Soc., 136, p. 9327 (2014).

    http://dx.doi.org/10.1021/ja413115h
  • Alexander Schubert, Mirjam Falge, Martin Kess, Volker Settels, Stefan Lochbrunner, Walter T. Strunz, Frank Würthner, Bernd Engels, and Volker Engel: Theoretical analysis of the relaxation dynamics in perylene bisimide dimers excited by femtosecond laser pulses, J. Phys. Chem. A, 118, p. 1403 (2014). http://dx.doi.org/10.1021/jp412166a

until 2013 Show content
  • Alexander Schubert, Volker Settels, Wenlan Liu, Frank Würthner, Christoph Meier, Reinhold F. Fink, Stefan Schindlbeck, Stefan Lochbrunner, Bernd Engels, and Volker Engel: Ultrafast exciton self-trapping upon geometry deformation in perylene-based molecular aggregates,

    J. Phys. Chem. Lett., 4 (5), p. 792 (2013). http://dx.doi.org/10.1021/jz4000752
  • Julian Albert, Alexander Schubert, and Volker Engel: Two-dimensional vibronic spectroscopy of molecular predissociation, New Journal of Physics, 15, p. 025008 (2013).

    http://dx.doi.org/10.1088/1367-2630/15/2/025008
  • Johannes Wehner, Alexander Schubert, and Volker Engel: Vibronic energy localization in weakly coupled small molecular aggregates, Chem. Phys. Lett., 541, p. 49 (2012).
    http://dx.doi.org/10.1016/j.cplett.2012.05.034

  • Alexander Schubert and Volker Engel: Interference Effects in Vibronic 2D-Spectra of Diatomic Molecules, Z. Phys. Chem., 225, p. 703 (2011). https://doi.org/10.1524/zpch.2011.0087

  • Alexander Schubert and Volker Engel: Two-dimensional vibronic spectroscopy of coherent wave-packet motion, J. Chem. Phys., 134, p. 104304 (2011). http://dx.doi.org/10.1063/1.3560165

  • Alexander Schubert, Klaus Renziehausen, and Volker Engel: Mapping of quantum phases by two-dimensional vibronic spectroscopy of wave-packet revivals, Phys. Rev. A, 82, p. 013419 (2010). http://dx.doi.org/10.1103/PhysRevA.82.013419

  • Christof Walter, Robert Kritzer, Alexander Schubert, Christoph Meier, Otto Dopfer, and Volker Engel: Dissipative Wave Packet Dynamics of Hydrophobic→Hydrophilic Site Switching in Phenol-Ar Clusters, J. Phys. Chem. A, 114, 36, p. 9743 (2010). https://doi.org/10.1021/jp101964e

Contact

Alexander Schubert, Dr
PostDoc
Dr. Alexander Schubert
Phone
+49 3641 9-48338
Fax
+49 3641 9-48302
Room E010
Helmholtzweg 4
07743 Jena
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