Texas Tech University

Dr. Hans Lischka


Title: Adjunct Professor

Education: Ph.D., University of Vienna, 1968
Postdoctoral Study, University of Karlsruhe, 1972-1973

Research Area: Theoretical and Computational Chemistry

Email: hans.lischka@ttu.edu

Research Group 

Principal Research Interests

  • Method development in the fields of multireference Quantum Chemistry and nonadiabatic dynamics
  • Development of massively parallel quantum chemical codes
  • Photodynamics of biological systems and nanomaterials
  • Molecular Spectroscopy
The accurate evaluation of the electronic Schrödinger equation is of fundamental importance in Quantum Chemistry. The program development work of Dr. Lischka concentrates on efficient multireference configuration interaction methods within the framework of the COLUMBUS program system (http://www.univie.ac.at/columbus). This program has unique features for computing electronically excited states and their nonadiabatic interaction. Surface hopping dynamics is performed with the program system NEWTON-X (http://www.univie.ac.at/newtonx).

The photostability of DNA bases. None of the DNA bases show significant fluorescence but deactivate after photoactivation within about one picosecond back to the ground state. The most important decay mechanisms are the NH and interring stretching and ring puckering modes. To identify the actual decay pathways, comprehensive surface hopping dynamics simulations were performed for all DNA/RNA bases. This was the first time that such an extensive photochemical simulation campaign was performed. The results clearly showed that ring puckering modes dominated the dynamics, but also that characteristic differences between purine and pyrimidine bases existed.

The current research work of Dr. Lischka focuses on the photodynamics of DNA. As the figure below shows, several processes can occur in DNA after irradiation with UV light. The most interesting ones are the excitonic interactions in comparison to charge transfer complexes. Photodynamical simulations should show which process is really responsible for the significantly longer life times found experimentally in DNA.

A second photodynamical research project of Dr. Lischka focuses on photovoltaic processes. Main interests are the evolution of excitonic states (see figure below) across kinks in p-conjugated chains such as poly(p-phenylvinylene) and the formation of charge transfer states at boundaries and the separation of charges.

Representative Publications

  • Invited Article: "Electronically excited states and photodynamics: a continuing challenge", Plasser, F.; Barbatti, M.; Aquino, A. J. A.; Lischka, H. 50th Anniversary Issue Theor. Chem. Acc., in press
  • "Semi-classical dynamics simulations of charge transport in stacked p-systems", Plasser, F.; Lischka, H. J. Chem. Phys.2011, 134, 034309.
  • "The Decay Mechanism of Photo-excited Guanine – A Nonadiabatic Dynamics Study", Barbatti, M.; Szymczak, J.J.; Aquino, A. J. A.; Nachtigallová, D.; Lischka, H. J. Chem. Phys.2011, 134, 014304.
    Selected for: JCP: BioChemical Physics,2011, 5(1).
  • "On the relaxation mechanisms of UV-photoexcited DNA and RNA nucleobases", Barbatti, M.; Aquino, A. J. A.; Szymczak, J. J.; Nachtigallová, D.; Hobza, P.; Lischka, H. Proc. of the Nat. Acad. Science USA2010, 107, 21453.
  • "The non-adiabatic deactivation of 9H-adenine: a comprehensive picture based on mixed quantum-classical dynamics", Barbatti, M.; Lischka, H. J. Am. Chem. Soc.2008, 130, 6831.
  • Perspectives Article: "Nonadiabatic excited-state dynamics of polar π-systems and related model compounds of biological relevance", Barbatti, M.; Ruckenbauer, M.; Szymczak, J.J.; Aquino, A. J. A.; H. Lischka Chem Phys2008, 10, 482.

Book Chapter

  • "Computational and Methodological Elements for Nonadiabatic Trajectory Dynamics Simulations of Molecules", in "Conical Intersections: Theory, Computation and Experiment", W. Domcke, D.R. Yarkony and H. Köppel, Eds.,
    Barbatti, M.; Shepard, R.; Lischka, H. Advanced Series in Physical Chemistry, Vol. 17, World Scientific, Singapore, in press