@misc{LorenzSaalfrank2015, author = {Lorenz, Ulf and Saalfrank, Peter}, title = {Comparing thermal wave function methods for multi-configuration time-dependent Hartree simulations (vol 140, 044106, 2014)}, series = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, volume = {143}, journal = {The journal of chemical physics : bridges a gap between journals of physics and journals of chemistr}, number = {22}, publisher = {American Institute of Physics}, address = {Melville}, issn = {0021-9606}, doi = {10.1063/1.4938051}, pages = {1}, year = {2015}, language = {en} } @article{LorenzSaalfrank2015, author = {Lorenz, Ulf and Saalfrank, Peter}, title = {Measures for the non-Markovianity of a harmonic oscillator coupled to a discrete bath derived from numerically exact references}, series = {The European physical journal : D, Atomic, molecular, optical and plasma physics}, volume = {69}, journal = {The European physical journal : D, Atomic, molecular, optical and plasma physics}, number = {2}, publisher = {Springer}, address = {New York}, issn = {1434-6060}, doi = {10.1140/epjd/e2014-50727-8}, pages = {14}, year = {2015}, abstract = {System-bath problems in physics and chemistry are often described by Markovian master equations. However, the Markov approximation, i.e., neglect of bath memory effects is not always justified, and different measures of non-Markovianity have been suggested in the literature to judge the validity of this approximation. Here we calculate several computable measures of non-Markovianity for the non-trivial problem of a harmonic oscillator coupled to a large number of bath oscillators. The Multi Configurational Time Dependent Hart ree nietliod is used to provide a numerically converged solution of the system-bath Schrodinger equation, from which the appropriate quantities can be calculated. In particular, we consider measures based on trace-distances and quantum discord for a variety of initial states. These quantities have proven useful in the case of two-level and other small model systems Tpically encountered in quantum optics; but are less straightforward to interpret for the more complex model systems that are relevant for chemical physics.}, language = {en} } @article{SulyanovaShabalinZozulyaetal.2015, author = {Sulyanova, Elena A. and Shabalin, Anatoly and Zozulya, Alexey V. and Meijer, Janne-Mieke and Dzhigaev, Dmitry and Gorobtsov, Oleg and Kurta, Ruslan P. and Lazarev, Sergey and Lorenz, Ulf and Singer, Andrej and Yefanov, Oleksandr and Zaluzhnyy, Ivan and Besedin, Ilya and Sprung, Michael and Petukhov, Andrei V. and Vartanyants, Ivan A.}, title = {Structural Evolution of Colloidal Crystal Films in the Process of Melting Revealed by Bragg Peak Analysis}, series = {Langmuir}, volume = {31}, journal = {Langmuir}, number = {19}, publisher = {American Chemical Society}, address = {Washington}, issn = {0743-7463}, doi = {10.1021/la504652z}, pages = {5274 -- 5283}, year = {2015}, abstract = {In situ X-ray diffraction studies of structural evolution of colloidal crystal films formed by polystyrene spherical particles upon incremental heating are reported. The Bragg peak parameters, such as peak position, integrated intensity, and radial and azimuthal widths were analyzed as a function of temperature. A quantitative study of colloidal crystal lattice distortions and mosaic spread as a function of temperature was carried out using Williamson-Hall plots based on mosaic block model. The temperature dependence of the diameter of polystyrene particles was obtained from the analysis of Bragg peaks, and the form factor contribution extracted from the diffraction patterns. Four stages of structural evolution in a colloidal crystal upon heating were identified. Based on this analysis, a model of the heating and melting process in the colloidal crystal film is suggested.}, language = {en} } @article{GorobtsovLorenzKabachniketal.2015, author = {Gorobtsov, Oleg Yu. and Lorenz, Ulf and Kabachnik, Nicolai M. and Vartanyants, Ivan A.}, title = {Theoretical study of electronic damage in single-particle imaging experiments at x-ray free-electron lasers for pulse durations from 0.1 to 10 fs}, series = {Physical review : E, Statistical, nonlinear and soft matter physics}, volume = {91}, journal = {Physical review : E, Statistical, nonlinear and soft matter physics}, number = {6}, publisher = {American Physical Society}, address = {College Park}, issn = {1539-3755}, doi = {10.1103/PhysRevE.91.062712}, pages = {13}, year = {2015}, abstract = {X-ray free-electron lasers (XFELs) may allow us to employ the single-particle imaging (SPI) method to determine the structure of macromolecules that do not form stable crystals. Ultrashort pulses of 10 fs and less allow us to outrun complete disintegration by Coulomb explosion and minimize radiation damage due to nuclear motion, but electronic damage is still present. The major contribution to the electronic damage comes from the plasma generated in the sample that is strongly dependent on the amount of Auger ionization. Since the Auger process has a characteristic time scale on the order of femtoseconds, one may expect that its contribution will be significantly reduced for attosecond pulses. Here we study the effect of electronic damage on the SPI at pulse durations from 0.1 to 10 fs and in a large range of XFEL fluences to determine optimal conditions for imaging of biological samples. We analyzed the contribution of different electronic excitation processes and found that at fluences higher than 1013-1015 photons/mu m(2) (depending on the photon energy and pulse duration) the diffracted signal saturates and does not increase further. A significant gain in the signal is obtained by reducing the pulse duration from 10 to 1 fs. Pulses below a duration of 1 fs do not give a significant gain in the scattering signal in comparison with 1-fs pulses. We also study the limits imposed on SPI by Compton scattering.}, language = {en} }