TY - JOUR A1 - Klinkusch, Stefan A1 - Klamroth, Tillmann T1 - Simulations of pump-probe exitations of electronic wave packets for a large qusi-rigid molecular system by means of an extension to the time-dependent configuration interaction singles method JF - Journal of theoretical and computational chemistry N2 - In this paper, we report simulations of laser-driven many-electron dynamics by means of the time-dependent configuration interaction singles (TD-CIS) approach. Photoionization is included by a heuristic model within calculations employing standard Gaussian basis sets. Benzo[g]-N-methyl-quinolinium-7-hydroxylate (BMQ7H) serves as a test system to generate predefined wave packets, i.e. a superposition between the ground and fifth excited state, in a large molecule. For this molecule, these two states have a very similar geometry, which enables us to use the fixed nuclei approximation. Furthermore, this geometric stability would also prevent a dephasing of the electron wave packet due to nuclear dynamics in an experimental realization of our simulations. We also simulate the possible detection of such a wave packet by ultra short probe laser pulses, i.e. pump-probe spectra. KW - Electron dynamics KW - time-dependent configuration interaction KW - pump-probe Y1 - 2013 U6 - https://doi.org/10.1142/S0219633613500053 SN - 0219-6336 VL - 12 IS - 3 PB - World Scientific CY - Singapore ER - TY - JOUR A1 - Tremblay, Jean Christophe A1 - Klinkusch, Stefan A1 - Klamroth, Tillmann A1 - Saalfrank, Peter T1 - Dissipative many-electron dynamics of ionizing systems JF - The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr N2 - In this paper, we perform many-electron dynamics using the time-dependent configuration-interaction method in its reduced density matrix formulation (rho-TDCI). Dissipation is treated implicitly using the Lindblad formalism. To include the effect of ionization on the state-resolved dynamics, we extend a recently introduced heuristic model for ionizing states to the rho-TDCI method, which leads to a reduced density matrix evolution that is not norm-preserving. We apply the new method to the laser-driven excitation of H(2) in a strongly dissipative environment, for which the state-resolve lifetimes are tuned to a few femtoseconds, typical for dynamics of adsorbate at metallic surfaces. Further testing is made on the laser-induced intramolecular charge transfer in a quinone derivative as a model for a molecular switch. A modified scheme to treat ionizing states is proposed to reduce the computational burden associated with the density matrix propagation, and it is thoroughly tested and compared to the results obtained with the former model. The new approach scales favorably (similar to N(2)) with the number of configurations N used to represent the reduced density matrix in the rho-TDCI method, as compared to a N(3) scaling for the model in its original form. Y1 - 2011 U6 - https://doi.org/10.1063/1.3532410 SN - 0021-9606 VL - 134 IS - 4 PB - American Institute of Physics CY - Melville ER - TY - JOUR A1 - Klinkusch, Stefan A1 - Klamroth, Tillmann A1 - Saalfrank, Peter T1 - Long-range intermolecular charge transfer induced by laser pulses : an explicitly time-dependent configuration interaction approach N2 - In this paper, we report simulations of laser-driven many-electron dynamics by means of the time-dependent configuration interaction singles (TD-CIS) approach. The method is capable of describing explicitly time-dependent phenomena beyond perturbation theory and is systematically improvable. In contrast to most time-dependent density functional methods it also allows us to treat long-range charge-transfer states properly. As an example, the laser-pulse induced charge transfer between a donor (ethylene) and an acceptor molecule (tetracyanoethylene, TCNE) is studied by means of TD-CIS. Also, larger aggregates consisting of several donors and/or acceptors are considered. It is shown that the charge distribution and hence the dipole moments of the systems under study are switchable by (a series of) laser pulses which induce selective, state-to-state electronic transitions. Y1 - 2009 UR - http://xlink.rsc.org/jumptojournal.cfm?journal_code=CP U6 - https://doi.org/10.1039/B817873a SN - 1463-9076 ER - TY - JOUR A1 - Klinkusch, Stefan A1 - Saalfrank, Peter A1 - Klamroth, Tillmann T1 - Laser-induced electron dynamics including photoionization : a heuristic model within time-dependent configuration interaction theory N2 - We report simulations of laser-pulse driven many-electron dynamics by means of a simple, heuristic extension of the time-dependent configuration interaction singles (TD-CIS) approach. The extension allows for the treatment of ionizing states as nonstationary states with a finite, energy-dependent lifetime to account for above-threshold ionization losses in laser-driven many-electron dynamics. The extended TD-CIS method is applied to the following specific examples: (i) state-to-state transitions in the LiCN molecule which correspond to intramolecular charge transfer, (ii) creation of electronic wave packets in LiCN including wave packet analysis by pump-probe spectroscopy, and, finally, (iii) the effect of ionization on the dynamic polarizability of H-2 when calculated nonperturbatively by TD-CIS. Y1 - 2009 UR - http://jcp.aip.org/ U6 - https://doi.org/10.1063/1.3218847 SN - 0021-9606 ER - TY - THES A1 - Klinkusch, Stefan T1 - Simulations of laser-induced correlated many-electron dynamics in molecular systems T1 - Simulationen laserinduzierter korrelierter Vielelektronendynamik in molekularen Systemen N2 - In this thesis, simulations of laser-driven many-electron dynamics in molecules are presented, i.e., the interaction between molecules and an electromagnetic field is demonstrated. When a laser field is applied to a molecular system, a population of higher electronic states takes place as well as other processes, e.g. photoionization, which is described by an appropriate model. Also, a finite lifetime of an excited state can be described by such a model. In the second part, a method is postulated that is capable of describing electron correlation in a time-dependent scheme. This is done by introducing a single-electron entropy that is at least temporarily minimized in a further step. N2 - Im Rahmen dieser Doktorarbeit werden Simulationen lasergetriebener Vielelektronendynamik in Molekülen präsentiert, d.h., die Wechselwirkung zwischen Molekülen und einem elektromagnetischen Feld wird demonstriert. Bei Laseranregungen finden nicht nur elektronische Übergänge statt, sondern auch weitere Prozesse wie die Photoionisation, die mit einem geeigneten Modell beschrieben wird. Auch die endliche Lebensdauer angeregter Zustände kann mit einem solchen Modell beschrieben werden. Im zweiten Teil wird eine Methode postuliert, die fähig ist, die Elektronenkorrelation zeitabhängig zu beschreiben. Dies wird durch die Einführung einer Einelektronenentropie erreicht, die in einem weiteren Schritt zumindest kurzzeitig minimiert wird. KW - Elektronendynamik KW - Laserpulse KW - Photoionisation KW - Elektronenkorrelation KW - electron dynamics KW - laser pulses KW - photoionization KW - electron correlation Y1 - 2011 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-55445 ER - TY - CHAP A1 - Saalfrank, Peter A1 - Bedurke, Florian A1 - Heide, Chiara A1 - Klamroth, Tillmann A1 - Klinkusch, Stefan A1 - Krause, Pascal A1 - Nest, Mathias A1 - Tremblay, Jean Christophe ED - Ruud, Kenneth ED - Brändas, Erkki J. T1 - Molecular attochemistry: correlated electron dynamics driven by light T2 - Advances in quantum chemistry N2 - Modern laser technology and ultrafast spectroscopies have pushed the timescales for detecting and manipulating dynamical processes in molecules from the picosecond over femtosecond domains, to the attosecond regime (1 as = 10(-18) s). This way, real-time dynamics of electrons after their photoexcitation can be probed and manipulated. In particular, experiments are moving more and more from atomic and solid state systems to molecules, opening the fields of "molecular electron dynamics" and "attosecond chemistry." Also on the theory side, powerful quantum dynamical tools have been developed to rationalize experiments on ultrafast electron dynamics in molecular species.
In this contribution, we concentrate on theoretical aspects of ultrafast electron dynamics in molecules, mostly driven by lasers. The dynamics will be described with the help of wavefunction-based ab initio methods such as time-dependent configuration interaction (TD-CI) or the multiconfigurational time-dependent Hartree-Fock (MCTDHF) methods. Besides a survey of the methods and their extensions toward, e.g., treatment of ionization, laser pulse optimization, and open quantum systems, two specific examples of applications will be considered: The creation and/or dynamical fate of electronic wavepackets, and the nonlinear optical response to laser pulse excitation in molecules by high harmonic generation (HHG). KW - dipole approximation KW - electron dynamics KW - electronic wavepackets KW - high harmonic generation KW - ionization KW - optimal control theory KW - time-dependent Schrödinger equation Y1 - 2020 SN - 978-0-12-819757-8 U6 - https://doi.org/10.1016/bs.aiq.2020.03.001 SN - 0065-3276 VL - 81 SP - 15 EP - 50 PB - Elsevier CY - Amsterdam [u.a.] ER -