Max Planck Institute For Struktur Und Dynamik Der Materie

Hamburg, Germany

Max Planck Institute For Struktur Und Dynamik Der Materie

Hamburg, Germany
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Dimitrov T.,Fritz Haber Institute | Dimitrov T.,Max Planck Institute For Struktur Und Dynamik Der Materie | Appel H.,Fritz Haber Institute | Appel H.,Max Planck Institute For Struktur Und Dynamik Der Materie | And 3 more authors.
New Journal of Physics | Year: 2016

In the present work, we employ exact diagonalization for model systems on a real-space lattice to explicitly construct the exact density-to-potential and graphically illustrate the complete exact density-to-wavefunction map that underly the Hohenberg-Kohn theorem in density functional theory. Having the explicit wavefunction-to-density map at hand, we are able to construct arbitrary observables as functionals of the ground-state density. We analyze the density-to-potential map as the distance between the fragments of a system increases and the correlation in the system grows. We observe a feature that gradually develops in the density-to-potential map as well as in the density-to-wavefunction map. This feature is inherited by arbitrary expectation values as functional of the ground-state density. We explicitly show the excited-state energies, the excited-state densities, and the correlation entropy as functionals of the ground-state density. All of them show this exact feature that sharpens as the coupling of the fragments decreases and the correlation grows. We denominate this feature as intra-system steepening and discuss how it relates to the well-known inter-system derivative discontinuity. The inter-system derivative discontinuity is an exact concept for coupled subsystems with degenerate ground state. However, the coupling between subsystems as in charge transfer processes can lift the degeneracy. An important conclusion is that for such systems with a near-degenerate ground state, the corresponding cut along the particle number N of the exact density functionals is differentiable with a well-defined gradient near integer particle number. © 2016 IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.


PubMed | Physikalisch - Technische Bundesanstalt, Max Planck Institute For Struktur Und Dynamik Der Materie, Max Planck Institute fuer medizinische Forschung, Max Planck Institute for the Structure and Dynamics of Matter and 3 more.
Type: | Journal: Journal of physics. Condensed matter : an Institute of Physics journal | Year: 2016

Carrier and lattice dynamics of laser excited CdTe was studied by time-resolved reflectivity for excitation fluences spanning about three orders of magnitude from 0.064 to 6.14 mJ/cm2. At fluences below 1 mJ/cm2 the transient reflectivity is dominated by the dynamics of hybrid phonon-plasmon modes. At fluences above 1 mJ/cm2 the time-dependent reflectivity curves show a complex interplay between band-gap renormalization, band filling, carrier dynamics and recombination. A framework that accounts for such complex dynamics is presented and used to model the time-dependent reflectivity data. This model suggests that the excess energy of the laser-excited hot carriers is reduced much more efficiently by emitting hybrid phonon-plasmon modes rather than bare longitudinal optical phonons.


Medcraft C.,Max Planck Institute For Struktur Und Dynamik Der Materie | Medcraft C.,Center for Free Electronic Laser Science | Wolf R.,University of Regensburg | Schnell M.,Max Planck Institute For Struktur Und Dynamik Der Materie | Schnell M.,Center for Free Electronic Laser Science
Angewandte Chemie - International Edition | Year: 2014

Heavy-metal containing chiral compounds have been suggested as promising candidates for studying parity-violation effects. We report herein the broadband rotational spectroscopy study of the chiral complex [CpRe-(CH3)(CO)(NO)] in the gas phase. The spectra obtained are very rich due to the two rhenium isotopologues (185Re and 187Re), hyperfine structure arising from the rhenium and nitrogen nuclei, and the asymmetry of the chiral complex. Since rhenium is located very close to the molecular center of mass, the rotational constants for the two rhenium isotopologues are very similar. However they can be differentiated by their characteristic nuclear quadrupole hyperfine splitting patterns. Comparison with calculated nuclear quadrupole coupling constants shows that all-electron relativistic basis sets are necessary for a correct description of the rhenium atom in this type of complex. The present study is an important step towards future precision studies on chiral molecules. © 2014 Wiley-VCH Verlag GmbH & Co. KGaA.


Schmitz D.,Max Planck Institute For Struktur Und Dynamik Der Materie | Schmitz D.,Center for Free Electronic Laser Science | Shubert V.A.,Max Planck Institute For Struktur Und Dynamik Der Materie | Shubert V.A.,Center for Free Electronic Laser Science | And 5 more authors.
Journal of Physical Chemistry Letters | Year: 2015

We here report on double-resonance experiments using broadband chirped pulse Fourier transform microwave spectroscopy that can facilitate spectral assignment and yield information about weak transitions with high resolution and sensitivity. Using the diastereomers menthone and isomenthone, we investigate the dependence of pumping a radio frequency transition on both the amplitude and phase of the signal from a microwave transition with which it shares a common rotational level. We observe a strong phase change when scanning the radio frequency through molecular resonance. The direction of the phase change depends on the energy level arrangement, that is, if it is progressive or regressive. The experimental results can be simulated using the three-level optical Bloch equations and described with the AC Stark effect, giving rise to an Autler-Townes splitting. © 2015 American Chemical Society.


Patterson D.,Harvard University | Schnell M.,Max Planck Institute For Struktur Und Dynamik Der Materie | Schnell M.,Center for Free Electronic Laser Science
Physical Chemistry Chemical Physics | Year: 2014

Chirality plays a fundamental role in the activity of biological molecules and broad classes of chemical reactions. The chemistry of life is built almost exclusively on left-handed amino acids and right-handed sugars, a phenomenon known as "homochirality of life". Furthermore, most drugs developed in the last decade are of specified chirality. Thus, fast and reliable methods that can differentiate molecules of different handedness, determine the enantiomeric excess of even molecular mixtures, and allow for an unambiguous determination of molecular handedness are of great interest, in particular with respect to complex mixtures. In this perspective article, we discuss the recent developments, with an emphasis on modern spectroscopic methods using gas-phase samples, such as photoelectron circular dichroism, Coulomb explosion imaging, and microwave three-wave mixing. © 2014 the Partner Organisations.


Alvin Shubert V.,Center for Free Electronic Laser Science | Schmitz D.,Center for Free Electronic Laser Science | Schnell M.,Max Planck Institute For Struktur Und Dynamik Der Materie
Journal of Molecular Spectroscopy | Year: 2014

We demonstrate three-wave mixing for enantiomer differentiation in the microwave regime using rotational transitions in cold gas-phase samples of menthone and carvone. The technique can also be understood as a polarization-dependent double-resonance experiment and has recently been shown to have high chiral sensitivity and mixture compatibility due to its resonant character. We here apply it to molecules containing two stereogenic centers, an important step towards investigating more complex species. We also demonstrate simultaneous microwave three-wave mixing of two structurally related monoterpenes, menthone and carvone, in a chiral mixture, which is possible due to the high sensitivity of rotational spectroscopy to structural differences. © 2014 Elsevier Inc. All rights reserved.


Shubert V.A.,Max Planck Institute For Struktur Und Dynamik Der Materie | Shubert V.A.,Center for Free Electronic Laser Science | Schmitz D.,Max Planck Institute For Struktur Und Dynamik Der Materie | Schmitz D.,Center for Free Electronic Laser Science | And 5 more authors.
Angewandte Chemie - International Edition | Year: 2014

Chirality-sensitive broadband microwave spectroscopy was performed on mixtures of carvone enantiomers and conformers to distinguish enantiomers, measure enantiomeric excesses, and determine the absolute configurations of the enantiomers. This method uses microwave three-wave mixing and is inherently well-suited to the analysis of mixtures - a unique advantage over other techniques. In contrast to conventional microwave spectroscopy, the phase of the received signal is also exploited. This phase depends upon the signs of the molecules' dipole-moment components and is used to identify the excess enantiomer. The measured signal amplitude determines the size of the excess. The broadband capabilities of the spectrometer were used to simultaneously excite and measure two conformers of carvone, demonstrating the analysis of a sample with multiple chiral species. Employing quantum chemical calculations and the measured phases, the absolute configurations of the enantiomers are determined. Enantiomer differentiation, enantiomeric excess measurement, and absolute configuration determination within a mixture of gas-phase chiral molecules are demonstrated. In these experiments, microwave three-wave mixing within supersonic jets is combined with chirped-pulse broadband microwave spectroscopy. This new technique is now a significant step closer to broader application. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


PubMed | Max Planck Institute For Struktur Und Dynamik Der Materie, University of Kaiserslautern and University of Gottingen
Type: Journal Article | Journal: Physical chemistry chemical physics : PCCP | Year: 2016

Dispersion interactions are omnipresent in intermolecular interactions, but their respective contributions are difficult to predict. Aromatic ethers offer competing docking sites for alcohols: the ether oxygen as a well known hydrogen bond acceptor, but also the aromatic system. The interaction with two aromatic moieties in diphenyl ether can tip the balance towards binding. We use a multi-spectroscopic approach to study the molecular recognition, the structure and internal dynamics of the diphenyl ether-methanol complex, employing infrared, infrared-ultraviolet and microwave spectroscopy. We find that the conformer with the hydroxy group of the alcohol binding to one aromatic cloud and being coordinated by an aromatic C-H bond of the other phenyl group is preferred. Depending on the expansion conditions in the supersonic jet, we observe a second conformer, which exhibits a hydrogen bond to the ether oxygen and is higher in energy.


Brumme T.,CNRS Institute of Mineralogy, Materials Physics and Cosmochemistry | Brumme T.,Max Planck Institute For Struktur Und Dynamik Der Materie | Calandra M.,CNRS Institute of Mineralogy, Materials Physics and Cosmochemistry | Mauri F.,University of Rome La Sapienza
Physical Review B - Condensed Matter and Materials Physics | Year: 2016

The transition-metal dichalcogenides have attracted a lot of attention as a possible stepping-stone toward atomically thin and flexible field-effect transistors. One key parameter to describe the charge transport is the time between two successive scattering events - the transport scattering time. In a recent report, we have shown that it is possible to use density functional theory to obtain the band structure of two-dimensional semiconductors in the presence of field effect doping. Here, we report a simple method to extract the scattering time from the experimental conductivity and from the knowledge of the band structure. We apply our approach to monolayers and multilayers of MoS2, MoSe2, MoTe2, WS2, and WSe2 in the presence of a gate. In WS2, for which accurate measurements of mobility have been published, we find that the scattering time is inversely proportional to the density of states at the Fermi level. Finally, we show that it is possible to identify the critical doping at which different valleys start to be occupied from the doping dependence of the conductivity. © 2016 American Physical Society.


PubMed | Max Planck Institute For Struktur Und Dynamik Der Materie and Harvard University
Type: Journal Article | Journal: Angewandte Chemie (International ed. in English) | Year: 2016

Cooling molecules in the gas phase is important for precision spectroscopy, cold molecule physics, and physical chemistry. Measurements of conformational relaxation cross sections shed important light on potential energy surfaces and energy flow within a molecule. However, gas-phase conformational cooling has not been previously observed directly. In this work, we directly observe conformational dynamics of 1,2-propanediol in cold (6K) collisions with atomic helium using microwave spectroscopy and buffer-gas cooling. Precise knowledge and control of the collisional environment in the buffer-gas allows us to measure the absolute collision cross-section for conformational relaxation. Several conformers of 1,2-propanediol are investigated and found to have relaxation cross-sections with He ranging from =4.7(3.0)10(-18) cm(2) to >510(-16) cm(2). Our method is applicable to a broad class of molecules and could be used to provide information about the potential energy surfaces of previously uninvestigated molecules.

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