Physikalisch Chemisches Institute

Zürich, Switzerland

Physikalisch Chemisches Institute

Zürich, Switzerland

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Inarrea M.,University of La Rioja | Salas J.P.,University of La Rioja | Gonzalez-Ferez R.,University of Granada | Schmelcher P.,Physikalisch Chemisches Institute | Schmelcher P.,University of Heidelberg
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2010

We study the classical dynamics of a polar diatomic molecule in the presence of a strong static homogeneous electric field. Our full rovibrational investigation includes the interaction with the field due to the permanent electric dipole moment and the polarizability of the molecule. Using the LiCs molecule as a prototype, we explore the stability of the equilibrium points and their bifurcations as the field strength is increased. The phase space structure and its dependence on the energy and field strength are analyzed in detail. We demonstrate that depending on the field strength and on the energy, the phase space is characterized either by regular features or by small stochastic layers of chaotic motion. © 2009 Elsevier B.V. All rights reserved.


Burdzinski G.,Adam Mickiewicz University | Sliwa M.,University of Lille Nord de France | Zhang Y.,Massachusetts Institute of Technology | Delbaere S.,University of Lille Nord de France | And 2 more authors.
Photochemical and Photobiological Sciences | Year: 2013

Photochemistry of 4-phenyl-1,2,3-thiadiazole (PT) and 4,5-diphenyl-1,2,3- thiadiazole (DPT) in solution was studied at room temperature using UV-vis and IR transient absorption spectroscopies (λex = 266 nm). Ultrafast techniques show a very fast rise (<0.3 ps) of thiirene and thioketene species, formed from 1,2,3-thiadiazoles in the singlet excited state. The remarkable unimolecular stability of thiirenes in solution is observed. On a millisecond time scale thiirenes with phenyl substituents undergo an intermolecular reaction (dimerization of thiirene-thioketene complexes) leading to 1,3-dithiole derivatives. © 2013 The Royal Society of Chemistry and Owner Societies.


Pont F.M.,National University of Cordoba | Bande A.,Helmholtz Center Berlin | Bande A.,Physikalisch Chemisches Institute | Cederbaum L.S.,Physikalisch Chemisches Institute
Journal of Physics Condensed Matter | Year: 2016

We recently predicted that the interatomic Coulombic electron capture (ICEC) process, a long-range electron correlation driven capture process, is achievable in gated double quantum dots (DQDs). In ICEC an incoming electron is captured by one quantum dot (QD) and the excess energy is used to remove an electron from the neighboring QD. In this work we present systematic full three-dimensional electron dynamics calculations in quasi-one dimensional model potentials that allow for a detailed understanding of the connection between the DQD geometry and the reaction probability for the ICEC process. We derive an effective one-dimensional approach and show that its results compare very well with those obtained using the full three-dimensional calculations. This approach substantially reduces the computation times. The investigation of the electronic structure for various DQD geometries for which the ICEC process can take place clarify the origin of its remarkably high probability in the presence of two-electron resonances. © 2016 IOP Publishing Ltd. All rights reserved.


Bezchastnov V.G.,Physikalisch Chemisches Institute | Bezchastnov V.G.,RAS Ioffe Physical - Technical Institute | Pernpointner M.,Physikalisch Chemisches Institute | Schmelcher P.,Physikalisch Chemisches Institute | And 2 more authors.
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2010

We present all-electron relativistic studies of the polarizability properties of the Xe dimer. The studies rely on finite-field calculations of the dimer energies obtained by ab initio methods including electron correlations. An extended set of basis functions is designed in order to ensure a high accuracy of the calculations. Particular attention is paid to the analysis of the nonadditivity and anisotropy of the polarizability of the dimer. It is found that the polarizability of the dimer relative to that of the atoms can be accurately described analytically, at least for internuclear distances around and larger than the equilibrium distance of the dimer. © 2010 The American Physical Society.


Rehbinder J.,Physikalisch Chemisches Institute | Rehbinder J.,Ecole Polytechnique - Palaiseau | Bruckner L.,Physikalisch Chemisches Institute | Wipfler A.,Physikalisch Chemisches Institute | And 2 more authors.
Optics Express | Year: 2014

We demonstrate the use of shaped 10 fs pulses for multimodal microscopy. The combination of a broadband oscillator and a pulse shaper provides a flexible light source that can be optimized for various nonlinear effects produced in the sample, either for signal intensity or for selectivity. While the highest nonlinear generation efficiency is achieved with the shortest pulses, more complex waveforms address specific transitions in the sample for better contrast. This is shown experimentally with the imaging of a moss leaf and of human skin biopsies using coherent anti-Stokes Raman scattering, two-photon fluorescence and second harmonic generation signals. ©2014 Optical Society of America


Helbing J.,Physikalisch Chemisches Institute | Hamm P.,Physikalisch Chemisches Institute
Journal of the Optical Society of America B: Optical Physics | Year: 2011

We describe an optimized setup for two-dimensional (2D) IR spectroscopy, which can be implemented at low additional cost and with standard optics in any laboratory equipped for femtosecond mid-IR spectroscopy. An interferometer produces a pair of intense pump pulses, whose interferogram is simultaneously recorded and directly yields the relative phase needed for the calculation of absorptive 2D spectra. We analyze different sampling methods based on a realistic noise model and introduce fast population time modulation as an alternative to the use of choppers in the suppression of scatter. Signal levels are compared to those of a photon-echo setup. © 2010 Optical Society of America.


Bande A.,Physikalisch Chemisches Institute | Gokhberg K.,Physikalisch Chemisches Institute | Cederbaum L.S.,Physikalisch Chemisches Institute
Journal of Chemical Physics | Year: 2011

In this work we demonstrate that the interatomic Coulombic decay (ICD), an ultrafast electron relaxation process known for atoms and molecules, is possible in general binding potentials. We used the multiconfiguration time-dependent Hartree method for fermions to study ICD in real time in a two-electron model system of two potential wells. Two decay channels were identified and analyzed by using the box stabilization analysis as well as by evaluating the autocorrelation function and measuring the outgoing electron flux during time-propagations. The total and partial ICD widths of an excited state localized in one potential well as a function of the distance between the two potentials was obtained. Finally, we discuss the results with a view to a possible application of ICD in quantum dot technology. © 2011 American Institute of Physics.


Pont F.M.,Physikalisch Chemisches Institute | Bande A.,Physikalisch Chemisches Institute | Cederbaum L.S.,Physikalisch Chemisches Institute
Physical Review B - Condensed Matter and Materials Physics | Year: 2013

Highly accurate quantum electron dynamics calculations demonstrate that energy can be efficiently transferred between quantum dots. Specifically, in a double quantum dot an incoming electron is captured by one dot and the excess energy is transferred to the neighboring dot and used to remove an electron from this dot. This process is due to long-range electron correlation and shown to be operative at rather large distances between the dots. The efficiency of the process is greatly enhanced by preparing the double quantum dot such that the incoming electron is initially captured by a two-electron resonance state of the system. In contrast to atoms and molecules in nature, double quantum dots can be manipulated to achieve this enhancement. This mechanism leads to a surprisingly narrow distribution of the energy of the electron removed in the process which is explained by resonance theory. We argue that the process could be exploited in practice. © 2013 American Physical Society.


Bruckner L.,Physikalisch Chemisches Institute | Buckup T.,Physikalisch Chemisches Institute | Motzkus M.,Physikalisch Chemisches Institute
Optics Letters | Year: 2015

A novel approach for spectral focusing using a single-beam coherent anti-Stokes Raman scattering setup with a pulse shaper controlling the phase and amplitude is presented. By identifying the frequencies acting as the pump, Stokes, and probe, the high degree of control can be exploited in order to specifically and independently tailor the spectral region to act only as probe to achieve the highest signal intensity. While maintaining the optimal excitation of the vibrational coherence, a signal increase by a factor of six in comparison with usual spectral focusing schemes is readily obtained. The signal improvement and contrast is demonstrated on human skin tissue. © 2015 Optical Society of America.


Bruckner L.,Physikalisch Chemisches Institute | Buckup T.,Physikalisch Chemisches Institute | Motzkus M.,Physikalisch Chemisches Institute
Journal of the Optical Society of America B: Optical Physics | Year: 2016

We introduce an advanced and flexible spectral focusing coherent anti-Stokes Raman scattering (CARS) microspectroscopy scheme based on the independent control of pump, Stokes, and probe frequencies offered by a pulse shaper. Adjusting the instantaneous bandwidth of 10 fs pulses in the focus of a microscope to different Raman linewidths assures high spectral resolution and signal intensities from the CH-bond to the fingerprint region. Experimental results are confirmed by simulations based on the CARS signal generation process. By delaying the probe, increased signal intensity and minimized nonresonant background are achieved while enabling timedependent measurements. Contrast based on the difference of decoherence times is established and used to distinguish initially overlapping CH resonances of sunflower oil. Because of the transform-limited nature of the tailored probe, enhanced instantaneous nonlinear signals enable simultaneous multimodal imaging and molecule-specific CARS contrast as demonstrated on human skin tissue. © 2016 Optical Society of America.

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