@incollection{SaalfrankBedurkeHeideetal.2020,
  author    = {Saalfrank, Peter and Bedurke, Florian and Heide, Chiara and Klamroth, Tillmann and Klinkusch, Stefan and Krause, Pascal and Nest, Mathias and Tremblay, Jean Christophe},
  title     = {Molecular attochemistry: correlated electron dynamics driven by light},
  series = {Advances in quantum chemistry},
  volume    = {81},
  booktitle = {Advances in quantum chemistry},
  editor    = {Ruud, Kenneth and Br{\"a}ndas, Erkki J.},
  publisher = {Elsevier},
  address   = {Amsterdam [u.a.]},
  isbn      = {978-0-12-819757-8},
  issn      = {0065-3276},
  doi       = {10.1016/bs.aiq.2020.03.001},
  pages     = {15 -- 50},
  year      = {2020},
  abstract  = {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. <br /> 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).},
  language  = {en}
}
@article{MartinazzoNestSaalfranketal.2006,
  author    = {Martinazzo, Rocco and Nest, Mathias and Saalfrank, Peter and Tantardini, Gian Franco},
  title     = {A local coherent-state approximation to system-bath quantum dynamics},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {125},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {19},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.2362821},
  pages     = {16},
  year      = {2006},
  abstract  = {A novel quantum method to deal with typical system-bath dynamical problems is introduced. Subsystem discrete variable representation and bath coherent-state sets are used to write down a multiconfigurational expansion of the wave function of the whole system. With the help of the Dirac-Frenkel variational principle, simple equations of motion-a kind of Schrodinger-Langevin equation for the subsystem coupled to (pseudo) classical equations for the bath-are derived. True dissipative dynamics at all times is obtained by coupling the bath to a secondary, classical Ohmic bath, which is modeled by adding a friction coefficient in the derived pseudoclassical bath equations. The resulting equations are then solved for a number of model problems, ranging from tunneling to vibrational relaxation dynamics. Comparison of the results with those of exact, multiconfiguration time-dependent Hartree calculations in systems with up to 80 bath oscillators shows that the proposed method can be very accurate and might be of help in studying realistic problems with very large baths. To this end, its linear scaling behavior with respect to the number of bath degrees of freedom is shown in practice with model calculations using tens of thousands of bath oscillators.},
  language  = {en}
}
@article{NestLudwigUlusoyetal.2013,
  author    = {Nest, Mathias and Ludwig, M. and Ulusoy, I. and Klamroth, Tillmann and Saalfrank, Peter},
  title     = {Electron correlation dynamics in atoms and molecules},
  series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  volume    = {138},
  journal   = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr},
  number    = {16},
  publisher = {American Institute of Physics},
  address   = {Melville},
  issn      = {0021-9606},
  doi       = {10.1063/1.4801867},
  pages     = {6},
  year      = {2013},
  abstract  = {In this paper, we present quantum dynamical calculations on electron correlation dynamics in atoms and molecules using explicitly time-dependent ab initio configuration interaction theory. The goals are (i) to show that in which cases it is possible to switch off the electronic correlation by ultrashort laser pulses, and (ii) to understand the temporal evolution and the time scale on which it reappears. We characterize the appearance of correlation through electron-electron scattering when starting from an uncorrelated state, and we identify pathways for the preparation of a Hartree-Fock state from the correlated, true ground state. Exemplary results for noble gases, alkaline earth elements, and selected molecules are provided. For Mg we show that the uncorrelated state can be prepared using a shaped ultrashort laser pulse.},
  language  = {en}
}
@article{Nest2009,
  author    = {Nest, Mathias},
  title     = {The multi-configuration electron-nuclear dynamics method},
  issn      = {0009-2614},
  doi       = {10.1016/j.cplett.2009.03.013},
  year      = {2009},
  abstract  = {An approach to the correlated quantum dynamics of electrons and nuclei is proposed. It is an ab initio method, based on a multi-configuration expansion of the full molecular wave function. The objective of this development is to be able to describe the correlated motion of electrons in molecules beyond the fixed-nuclei approximation. Neither potential energy surfaces nor diabatic couplings need to be calculated, and Pulay forces do not appear. The method is illustrated by application to the 12 + 1 dimensional LiH molecule.},
  language  = {en}
}
@article{KlamrothNest2009,
  author    = {Klamroth, Tillmann and Nest, Mathias},
  title     = {Ultrafast electronic excitations of small sodium clusters and the onset of electron thermalization},
  issn      = {1463-9076},
  doi       = {10.1039/B813619j},
  year      = {2009},
  abstract  = {In this paper we report simulations of the ultrafast laser excitation and relaxation of the correlated valence electrons of a Na-8 cluster. The aim is twofold: first, while the total energy stays constant when the exciting laser pulse is over, we observe that the entropy computed from the reduced one electron density matrix rises on a much longer time scale. We discuss whether this can be understood as the onset of the thermalization of a finite system. Second, we describe this process with eight different methods of wavefunction-based electronic structure theory, which have been adapted for an explicitly time-dependent description. Their respective advantages and limitations for the simulation of the excitation and subsequent relaxation are explained.},
  language  = {en}
}
@article{SchaeferBungNest2008,
  author    = {Sch{\"a}fer-Bung, Boris and Nest, Mathias},
  title     = {Correlated dynamics of electrons with reduced 2-electron density matrices},
  year      = {2008},
  abstract  = {We present an approach to the correlated dynamics of many-electron systems. We show, that the two-electron reduced density matrix (2RDM) can provide a suitable description of the real time evolution of a system. To achieve this, the hierarchy of equations of motion must be truncated in a practical way. Also, the computational effort, given that the 2RDM is represented by products of two-electron determinants, is discussed, and numerical model calculations are presented.},
  language  = {en}
}
@article{BurghardtNestWorth2003,
  author    = {Burghardt, I. and Nest, Mathias and Worth, G. A.},
  title     = {Multiconfigurational system-bath dynamics using Gaussian wave packets : Energy relaxation and decoherence induced by a finite-dimensional bath},
  issn      = {0021-9606},
  year      = {2003},
  language  = {en}
}
@article{NestSaalfrank2004,
  author    = {Nest, Mathias and Saalfrank, Peter},
  title     = {Enhancement of femtosecond-laser-induced molecular desorption by thin metal films},
  year      = {2004},
  abstract  = {We investigate femtosecond-laser induced desorption [desorption induced by multiple electronic transitions (DIMET)] of NO molecules from thin Pt(111) films. On the basis of a two-state, open-system density matrix treatment in combination with a two-temperature model, we argue that decreasing the film thickness enhances desorption cross sections by orders of magnitude in comparison to bulk materials. Both the spatial confinement and the laser fluence appear therefore as efficient, nonlinear enhancement factors for nonadiabatic photoreactions of metal surfaces and, possibly, of nanostructered materials in general},
  language  = {en}
}
@article{HenkelNestDomokosetal.2004,
  author    = {Henkel, Carsten and Nest, Mathias and Domokos, P. and Folman, R.},
  title     = {Optical discrimination between spatial decoherence and thermalization of a massive object},
  year      = {2004},
  abstract  = {We propose an optical ring interferometer to observe environment-induced spatial decoherence of massive objects. The object is held in a harmonic trap and scatters light between degenerate modes of a ring cavity. The output signal of the interferometer permits to monitor the spatial width of the object's wave function. It shows oscillations that arise from coherences between energy eigenstates and that reveal the difference between pure spatial decoherence and that coinciding with energy transfer and heating. Our method is designed to work with a wide variety of masses, ranging from the atomic scale to nanofabricated structures. We give a thorough discussion of its experimental feasibility},
  language  = {en}
}
@article{BurghardtNestWorth2004,
  author    = {Burghardt, I. and Nest, Mathias and Worth, G. A.},
  title     = {Multiconfigurational system-bath dynamics using Gaussian wave packets : Energy relaxation and decoherence induced by a finite-dimensional bath},
  issn      = {0021-9606},
  year      = {2004},
  language  = {en}
}
@article{NestKlamrothSaalfrank2005,
  author    = {Nest, Mathias and Klamroth, Tillmann and Saalfrank, Peter},
  title     = {The multiconfiguration time-dependent Hartree-Fock method for quantum chemical calculations},
  issn      = {0021-9606},
  year      = {2005},
  abstract  = {We apply the multiconfiguration time-dependent Hartree-Fock method to electronic structure calculations and show that quantum chemical information can be obtained with this explicitly time-dependent approach. Different equations of motion are discussed, as well as the numerical cost. The two-electron integrals are calculated using a natural potential expansion, of which we describe the convergence behavior in detail},
  language  = {en}
}
@article{NestKlamroth2005,
  author    = {Nest, Mathias and Klamroth, Tillmann},
  title     = {Correlated many-electron dynamics : application to inelastic electron scattering at a metal film},
  year      = {2005},
  abstract  = {The multiconfiguration time-dependent Hartree-Fock and the time-dependent configuration interaction singles method are applied to the correlated many-electron dynamics of a one-dimensional jellium model system. We study the scattering of an initially free electron at a model film in the framework of both approaches. In particular, both methods are compared with regard to how they describe the underlying physical processes, namely inelastic electron scattering, inverse photoemission, and electron impact ionization},
  language  = {en}
}
@article{SaalfrankNestAndrianovetal.2006,
  author    = {Saalfrank, Peter and Nest, Mathias and Andrianov, Igor V. and Klamroth, Tillmann and Kroner, Dominic and Beyvers, Stephanie},
  title     = {Quantum dynamics of laser-induced desorption from metal and semiconductor surfaces, and related phenomena},
  volume    = {18},
  number    = {30},
  publisher = {IOP Publ.},
  address   = {Bristol},
  issn      = {1361-648X},
  doi       = {10.1088/0953-8984/18/30/S05},
  pages     = {S1425 -- S1459},
  year      = {2006},
  abstract  = {Recent progress towards a quantum theory of laser-induced desorption and related phenomena is reviewed, for specific examples. These comprise the photodesorption of NO from Pt(111), the scanning tunnelling microscope and laser- induced desorption and switching of H at Si(100), and the electron stimulated desorption and dissociation of CO at Ru(0001). The theoretical methods used for nuclear dynamics range from open-system density matrix theory over nonadiabatically coupled multi-state models to electron-nuclear wavepackets. Also, aspects of time-dependent spectroscopy to probe ultrafast nonadiabatic processes at surfaces will be considered for the example of two-photon photoemission of solvated electrons in ice layers on Cu(111)},
  language  = {en}
}
@article{Nest2006,
  author    = {Nest, Mathias},
  title     = {Quantum carpets and correlated dynamics of several fermions},
  doi       = {10.1103/Physreva.73.023613},
  year      = {2006},
  abstract  = {We study theoretically the coherent and correlated motion of many fermions inside an infinite square well potential. We will look at electrons and He-3 atoms, which behave very differently not only because of their masses, but also because of their different interaction potential. Also, the level of theory and the role of approximations in the solution of the time-dependent Schrodinger equation will be discussed},
  language  = {en}
}
@phdthesis{Nest2007,
  author    = {Nest, Mathias},
  title     = {Quantum dynamics for large systems: System-bath type situations and correlated dynamics of many electrons},
  address   = {Potsdam},
  pages     = {176 S., I-V, graph. Darst.},
  year      = {2007},
  language  = {en}
}
@phdthesis{Nest2007,
  author    = {Nest, Mathias},
  title     = {Quantum dynamics for large systems : system-bath type situations and correlated dynamics of many electrons},
  address   = {Potsdam},
  pages     = {v, 176 S.: graph. Darst.},
  year      = {2007},
  language  = {en}
}
@misc{SchaeferBungNest2008,
  author    = {Sch{\"a}fer-Bung, Boris and Nest, Mathias},
  title     = {Correlated dynamics of electrons with reduced two-electron density matrices},
  issn      = {1866-8372},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-41774},
  year      = {2008},
  abstract  = {We present an approach to the correlated dynamics of many-electron systems. We show, that the twoelectron reduced density matrix (2RDM) can provide a suitable description of the real time evolution of a system. To achieve this, the hierarchy of equations of motion must be truncated in a practical way. Also, the computational effort, given that the 2RDM is represented by products of two-electron determinants, is discussed, and numerical model calculations are presented.},
  language  = {en}
}