Atomic And Molecular Clusters

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Tracking Attosecond Electronic Coherences using Phase-Manipulated Extreme Ultraviolet Pulses (1906.07112v1)

Andreas Wituschek, Lukas Bruder, Enrico Allaria, Ulrich Bangert, Marcel Binz, Carlo Callegari, Giulio Cerullo, Paolo Cinquegrana, Luca Gianessi, Miltcho Danailov, Alexander Demidovich, Michele Di Fraia, Marcel Drabbels, Raimund Feifel, Tim Laarmann, Rupert Michiels, Najmeh Sadat Mirian, Marcel Mudrich, Ivaylo Nikolov, Finn H. O'Shea, Giuseppe Penco, Paolo Piseri, Oksana Plekan, Kevin Charles Prince, Andreas Przystawik, Primož Rebernik Ribič, Giuseppe Sansone, Paolo Sigalotti, Simone Spampinati, Carlo Spezzani, Richard James Squibb, Stefano Stranges, Daniel Uhl, Frank Stienkemeier

2019-06-17

The recent development of novel extreme ultraviolet (XUV) coherent light sources bears great potential for a better understanding of the structure and dynamics of matter. Promising routes are advanced coherent control and nonlinear spectroscopy schemes in the XUV energy range, yielding unprecedented spatial and temporal resolution. However, their implementation has been hampered by the experimental challenge of generating XUV pulse sequences with precisely controlled timing and phase properties. In particular, direct control and manipulation of the phase of individual pulses within a XUV pulse sequence opens exciting new possibilities for coherent control and multidimensional spectroscopy schemes, but has not been accomplished. Here, we overcome these constraints in a highly time-stabilized and phase-modulated XUV-pump, XUV-probe experiment which directly probes the evolution and dephasing of an inner subshell electronic coherence. This new approach, avoiding any XUV optics for direct pulse manipulation, opens up extensive applications of advanced nonlinear optics and spectroscopy at XUV wavelengths.

Fast reconstruction of single-shot wide-angle diffraction images through deep learning (1906.06883v1)

Thomas Stielow, Robin Schmidt, Christian Peltz, Thomas Fennel, Stefan Scheel

2019-06-17

Single-shot X-ray imaging of short-lived nanostructures such as clusters and nanoparticles near a phase transition or non-crystalizing objects such as large proteins and viruses is currently the most elegant method for characterizing their structure. Using hard X-ray radiation provides scattering images that encode two-dimensional projections, which can be combined to identify the full three-dimensional object structure from multiple identical samples. Wide-angle scattering using XUV or soft X-rays, despite yielding lower resolution, provides three-dimensional structural information in a single shot and has opened routes towards the characterization of non-reproducible objects in the gas phase. The retrieval of the structural information contained in wide-angle scattering images is highly non-trivial, and currently no efficient algorithm is known. Here we show that deep learning networks, trained with simulated scattering data, allow for fast and accurate reconstruction of shape and orientation of nanoparticles from experimental images. The gain in speed compared to conventional retrieval techniques opens the route for automated structure reconstruction algorithms capable of real-time discrimination and pre-identification of nanostructures in scattering experiments with high repetition rate -- thus representing the enabling technology for fast femtosecond nanocrystallography.

Time delay of slow electrons-endohedral elastic scattering (1906.06710v1)

M. Ya. Amusia, A. S. Baltenkov

2019-06-16

We discuss the temporal picture of electron collisions with fullerene. Within the framework of a Dirac bubble potential model for the fullerene shell, we calculate the time delay in slow-electron elastic scattering by it. It appeared that the time of transmission of an electron wave packet through the Dirac bubble potential sphere that simulates a real potential of the C60 reaches up to 104 attoseconds. Resonances in the time delays are due to the temporary trapping of electron into quasi-bound states before it leaves the interaction region. As concrete targets we choose almost ideally spherical endohedrals C20, C60, C72, and C80. We present dependences of time-delay upon collision energy.

Intershell correlations in endohedral atoms (1906.06708v1)

M. Ya. Amusia, L. V. Chernysheva

2019-06-16

We have calculated partial contributions of different endohedral and atomic subshells to the total dipole sum rule in the frame of the random phase approximation with exchange (RPAE) and found that they are essentially different from the numbers of electrons in respective subshells. This difference manifests the strength of the intershell interaction. We present concrete results of calculations for endohedrals, composed of fullerene C60 and all noble gases He, Ne, Ar, Kr and Xe thus forming respectively He@C60, Ne@C60, Ar@C60, Kr@C60, and Xe@C60. For comparison we obtained similar results for isolated noble gas atoms. The deviation from number of electrons in outer subshells proved to be much bigger in endohedrals than in isolated atoms thus demonstrating considerably stronger intershell correlations there.

A Novel Discrete Theory of a Screw Dislocation in the BCC Crystal Lattice (1906.04332v1)

Shigeki Matsutani

2019-06-11

In this paper, we proposed a novel method using the elementary number theory to investigate the discrete nature of the screw dislocations in crystal lattices, simple cubic (SC) lattice and body centered cubic (BCC) lattice, by developing the algebraic description of the dislocations in the previous report (Hamada, Matsutani, Nakagawa, Saeki, Uesaka, Pacific J. Math.~for Industry {\bf{10}} (2018), 3). Using the method, we showed that the stress energy of the screw dislocations in the BCC lattice and the SC lattice are naturally described; the energy of the BCC lattice was expressed by the truncated Epstein-Hurwitz zeta function of the Eisenstein integers, whereas that of SC lattice is associated with the truncated Epstein-Hurwitz zeta function of the Gauss integers.

Generation and Characterization of Tailored MIR Waveforms for Steering Molecular Dynamics (1906.03519v1)

Markus A. Jakob, Mahesh Namboodiri, Mark J. Prandolini, Tim Laarmann

2019-06-08

The dream of physico-chemists to control molecular reactions with light beyond electronic excitations pushes the development of laser pulse shaping capabilities in the mid-infrared (MIR) spectral range. Here, we present a compact optical parametric amplifier platform for the generation and shaping of MIR laser pulses in the wavelength range between m and m. Opportunities for judiciously tailoring the electromagnetic waveform are investigated, demonstrating light field control with a spectral resolution of 60 GHz at a total spectral bandwidth of 5 THz. In experiments focusing on spectral amplitude manipulation these parameters result in a time window of 1.8 ps available for shaping the temporal pulse envelope and a phase modulation resolution of 100 mrad for several picosecond delays.

Efimov universality with Coulomb interaction (1901.03643v3)

C. H. Schmickler, H. -W. Hammer, E. Hiyama

2019-01-11

The universal properties of charged particles are modified by the presence of a long-range Coulomb interaction. We investigate the modification of Efimov universality as a function of the Coulomb strength using the Gaussian expansion method. The resonant short-range interaction is described by Gaussian potentials to which a Coulomb potential is added. We calculate binding energies and root mean square radii for the three- and four-body systems of charged particles and present our results in a generalised Efimov plot. We find that universal features can still be discerned for weak Coulomb interaction, but break down for strong Coulomb interaction. The root-mean-square radius plateaus at increasingly smaller values for strong Coulomb interaction and the probablity distributions of the states become more concentrated inside the Coulomb barrier. As an example, we apply our universal model to nuclei with an alpha-cluster substructure. Our results point to strong non-universal contributions in that sector.

The Ratio Law of the Structure Evolution and Stability for TiO (-, -) Clusters (1906.05354v1)

Hongbo Du, Yu Jia, Chunyao Niu, Kaige Hu, Haifeng Li, Lingmin Yu

2019-06-03

Most theoretical investigations about titanium oxide clusters focus on (TiO). However, many TiO clusters with are produced experimentally. In this work, first-principles calculations are performed to probe the evolution of TiO clusters. Our investigations show that for -, there exist one relatively stable specie; while for -, there are two relatively stable species: Ti-rich and O-rich species. HOMO-LOMO calculations show that the gap can be tuned by changing the size and configurations of TiO clusters. Our investigation provides insights into the evolution of cluster-to-bulk process in titanium oxide.

Crystalline droplets with emergent topological color-charge in many-body systems with sign-changing interactions (1905.13217v1)

P. Karpov, F. Piazza

2019-05-30

We introduce a novel type of self-bound droplet which carries an emergent color-charge. We consider a system of particles hopping on a lattice and interacting via a commensurately sign-changing potential which is attractive at short range. The droplet formation is heralded by spontaneous crystallization into topologically distinct domains. This endows each droplet with an emergent color-charge governing their mutual interactions: attractive for equal colors and repulsive otherwise. The number of allowed colors is fixed only by the discrete spatial symmetries of the interaction potential. With increasing interaction range, the droplets become progressively more mobile, with their color-charge still being energetically protected, allowing for non-trivial viscous dynamics of the interacting droplet plasmas formed during cooling. Sign-changing potentials with short-range attraction appear quite naturally for light-mediated interactions and we concretely propose a realization in state-of-the-art experiments with cold atoms in a multimode optical cavity.

Dissociation dynamics in the dissociative electron attachment to ammonia molecule (1905.10993v1)

Dipayan Chakraborty, Aranya Giri, Dhananjay Nandi

2019-05-27

Complete dissociation dynamics of low energy electron attachment to ammonia molecule has been studied using velocity slice imaging (VSI) spectrometer. One low energy resonant peak around 5.5 eV and a broad resonance around 10.5 eV incident electron energy has been observed. The resonant states mainly dissociate via H and NH fragments, though for the upper resonant state, signature of NH fragments are also predicted due to three body dissociation process. Kinetic energy and angular distributions of the NH fragment anions are measured simultaneously using VSI technique. Based on our experimental observations, we find the signature of A symmetry in the 10.5 eV resonance energy whereas, the 5.5 eV resonance is associated with the well known A symmetry.

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