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Position openings for postdoctoral fellows co-funded by the Office of the National Administrative Committee for Postdoctoral Researchers in China (ONACPR) and DESY. Please see http://res.chinapostdoctor.org.cn/BshWeb/info.shtml?id=1db9f068-8a23-4cc2-80ab-3a470a7853bc for details and the following zip file for all announced projects at DESY: http://res.chinapostdoctor.org.cn/UserFile/Attachment/2015-06-10/12bac7ba-4741-4a1f-882a-3bea5af1b3e9.zip

General position announcements in Jochen Küpper’group are at http://www.controlled-molecule-imaging.org/careers/projects

Theyare looking for (senior) postdocs, especially for our COMOTION project: http://www.controlled-molecule-imaging.org/research/comotion

Univ.-Prof. Dr. Jochen Küpper
Controlled Molecule Imaging Group – http://www.controlled-molecule-imaging.org
Center for Free-Electron Laser Science (CFEL)
Department of Physics & Center for Ultrafast Imaging (CUI)

STSM by Sandra Gomez,  Complutense University of Madrid (ES)  with Volker Engel, Institut für Physikalische und Theoretische Chemie der Universität Würzburg (DE)
On March 15th, 2015 (75 days)
From SPAIN to GERMANY 

Two-dimensional spectroscopy of coupled nuclear and electronic motion.

The analysis of the dynamics of molecular systems is normally done by solving the Schrödinger equation for the electronic degrees of freedom for multiple fixed geometries of the nuclei obtaining potential energy surfaces, molecular orbitals,densities and more interesting properties. This description, within the Born-Oppenheimer approximation, fails in many cases. However, the computational effort of treating both kinds of particles at the same level of theory is huge, and this problem can only be solved if drastic simplifications are perfomed.

Here we use a model introduced by Shin and Metiu which consists in a four particles system, three nuclei and one electron, where only the electron and one of the nuclei are allowed to move in one dimension. The interaction between charges is parametrized such that we can consider two cases: one in which the coupling between the electron and the nucleous in movement is small enough to consider the Born-Oppenheimer approximation still valid, and the other one, where the BO approximation breaks down.
For obtaining the 2D-Spectra we focused on electric-dipole transitions caused by the interaction with three laser pulses, where the second and the third come at the same time and the response function is recovered in direction -k1+k2+k3 (as in a photon-echo experiment).
The spectra are calculated for the case of soft and large coupling and compared with those obtained applying the Born-Oppenheimer approximation, i.e. using electronic eigenfunctions only dependant on nuclear coordinates.

SAGOM2-imgAs we can observe in the picture, the results show that the Born-Oppenheimer approximation is valid for the case of small coupling, where the potential energy surfaces are far away enough, but it breaks completely down for the case of large coupling.

The results obtained on this stay are pending publication.

A post-doctoral researcher position is presently available to join a collaborative program between two research groups at the Institut des Sciences Moléculaires d’Orsay and the SOLEIL Synchrotron light source , dedicated to ultrafast dynamics of electronic and nuclear wavepackets in isolated molecules, from valence- and inner-shell photoionization to fragmentation and reaction dynamics, in time-resolved studies at the attosecond (as) and femtosecond (fs) time scales.

This program will take place in the context of the development of the ATTOLab facility which includes two high performance laser systems (Ti:sapphire IR, <20fs, CEP phase stabilized, respectively 15W/1kHz and 20W/10kHz, installed at CEA/l’Orme-les-Merisiers), and associated attosecond sources in the extreme-UV (XUV) based on laser-driven high harmonic generation. Advanced optical instrumentation of the XUV beamlines is being developed in the related OPT2X project with support of the Université Paris-Saclay.

The experiments will make use of multiparticle coincidence spectroscopy techniques to access physical observables at the most sensitive level, in particular through time-resolved studies of molecular-frame photoemission in excited molecules undergoing ultrafast dynamical changes. The postdoc will contribute to further develop existing equipment, e.g., electron/ion momentum imaging spectrometer of COLTRIMS type, and adapt it to the new capabilities of the 10 kHz attosecond beamline in ATTOLab. In parallel, photoemission studies will be carried out on the PLEIADES beamline at SOLEIL synchrotron. Within the synergy provided by the Université Paris-Saclay groups, opportunities will exist for the post-doctorate fellow to test new ideas using harmonic sources, synchrotron radiation and possibly FEL sources. Close collaborations with theoretical groups have already been established and will be essential to the interpretation of the data.

The candidate should have a PhD degree in either physics or physical chemistry granted within the last four years, and experience with some of the following topics:

– Gas phase molecular & photoionization dynamics using XUV radiation sources
– Multiparticle coincidence spectroscopy & data analysis
– Time & position sensitive charged particle detection

The position is currently available for one year with the possibility of one year extension on mutual agreement. Motivated candidates should forward a CV and contact information for two references before July 10th to:

Danielle Dowek – danielle.dowek@u-psud.fr and/or John Bozek – john.bozek@synchrotron-soleil.fr

ISMO, http://www.ismo.u-psud.fr/
SOLEIL Synchrotron, http://www.synchrotron-soleil.fr/
ATTOLab, http://attolab.fr/index.php

The WG2 expert meeting of XLIC COST Action (CM1204) Energetic Processing of Large Interstellar Molecules took place in Leiden (the Netherlands) at the Lorentz Center. The meeting was co-organized and co-sponsored with the Lorentz Center, the NWO Dutch Astrochemistry Network (DAN), and the Dutch Top Research School NOVA.

WG2EM-leiden-picture

The organizers/chairs of the meeting were professors R. Hoekstra (University of Groningen, the Netherlands), H. Cederquist (Stockholm University, Sweden), and A.G.G.M. Tielens (Leiden Observatory, the Netherlands).

The expert meeting aimed at overviewing the state of the art in experimental and theoretical studies on energetic processing of large molecules by ions and photons and the implications for the evolution of astrophysically relevant molecules. The fields of expertise of the participants therefore covered molecular physics, physical chemistry, and astronomy. It included molecular physicists involved in laboratory or quantum chemical studies on the interaction of energetic ions or photons with large molecules and astronomers involved in studies of the origin and evolution of large molecules in space.

The specific objective of the workshop was to identify and initiate joint experimental, theoretical, and observational studies with the aim of understanding energetic processing of large molecules of astrophysical relevance, including polycyclic aromatic hydrocarbons as well as carbon chains, and fullerenes.

To facilitate the identification of joint challenges across scientific disciplinary borders, the program started off by talks which introduced the mutual subfields to the participants highlighting the key questions, challenges, and opportunities. These introductory talks were given by Els Peeters, Nigel Mason and Franck Lépine. Four half-day topical sessions of 3 or 4 invited talks provided an in-depth view into the four directions of: “Large molecules in space“, “Molecular processes and structure“, “Particle interactions“, and “Photonic interactions“. For the full program see the attached meeting schedule. Each topical session was concluded by a plenary discussion in which specific points were further clarified and challenges for future research. The discussion sessions were very lively. The very high, overall degree of participation was inspired by the excellent talks and the scaffolding of the Lorentz center which is fully geared to the creation of an inspiring, informal, academic environment and atmosphere for open discussions.

The ample time left in the schedule for informal “splinter” discussions led to a further scientific cross-fertilization. In the concluding session, many topics for concerted research efforts were discussed and generic, prototypeical molecular systems identified that should serve as linking pin systems in projects involving members of the two networks, represented by XLIC and the astronomy network.

It was decided to have a successor meeting on Energetic Processing of Large Molecules (EPoLM-2, April 11-13, 2016). EPoLM-2 will be held in conjunction with the XLIC Stockholm meeting which runs from April 13-15.

The organisers:

Ronnie Hoekstra,
Henrik Cederquist, and
Xander Tielens

Related links:

WG2 Expert Meeting on Large Interstellar Molecules  (Netherlands, May2015) – Program Meeting web site – List of Participants

The Department of Physics and Astronomy (www.phys.au.dk) invites applications for an independent permanent position as Associate Professor in theoretical quantum molecular physics. The Department wants to strengthen its theory activities within interdisciplinary molecular sciences, covering physics and chemistry as well as applications in biological environments. The position is open from September 1, 2015.

The Department of Physics and Astronomy particularly wants to strengthen the theory activities within photo-physical properties of molecules (spectroscopy and dynamics). Documented research on molecular processes of biophysical relevance and experience with theoretical modeling of non-adiabatic molecular dynamics involving excited states is seen as an advantage. Documented collaboration with experimental groups, and application of the theoretical methods to a broader range of problems, is considered an asset.

Applicants must have a strong record of original scientific research at a high international level. They must document dynamic leadership and talent for supervision of young researchers. Abilities to promote collaborative research and to attract external funding are additionally favorable qualifications of the candidate for the position.

Applicants are expected to document their experience with University teaching in physics at all levels, including the supervision of MSc and PhD students.

Further information can be obtained from Head of Department Lars H. Andersen, Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C by e-mail: lha@phys.au.dk.

Formalities and salary range
Science and Technology refers to the Ministerial Order on the Appointment of Academic Staff at Danish Universities under the Danish Ministry of Science, Technology and Innovation.
The application must be in English and include a curriculum vitae, degree certificate, a complete list of publications, a statement of future research plans and information about research activities, teaching qualifications and management experience. Guidelines for applicants can be found here.
Appointment shall be in accordance with the collective labour agreement between the Danish Ministry of Finance and the Danish Confederation of Professional Associations. Further information on qualification requirements and job content may be found in the Memorandum on Job Structure for Academic Staff at Danish Universities. (in Danish).
Salary depends on seniority as agreed between the Danish Ministry of Finance and the Confederation of Professional Associations.

STSM by Fernando Aguilar-Galindo, Universidad Autónoma de Madrid (ES) with Michele Pavone, University of Naples (IT)
On February 8, 2015 (90 days)
From SPAIN to ITALY

AGUILAR-LOGOSShifting in the electronic levels of the acrylamide due its interaction with a Cu(100) surface

When the light interacts with a molecule it suffers internal changes due to the energy of the photon. With the appropriate light, it is possible even to break the molecule. This have been used in the recent years to treat cancer (phototherapy). In this work, we want to study the effect of a metallic surface (as a nanoparticle) on a molecule, in order to modify its electronic structure and reach the breaking with a less energetic light, which can be helpful to use less invasive radiation in the treatment of cancer.
We have performed a methodological assessment, in which we have compared several combinations of DFT functionals and basis with the results obtained with by CASPT2(8,6)/ANO-S (active space: the lone pairs, the π orbitals and the empty π* orbitals). We have found that for the acrylamide the transition S0->S2 (mainly a single excitation from the lone pair of the nitrogen to a π* orbital) can be correctly represented by TD-DFT with a deviation lower than 0.05 eV from the CASPT2 result by employing these combinations: LC-BLYP/6-31G, LC-wPBE/6-31G and M06HF/6-31G.
With those levels of theory, we have calculated the excitation of the molecule adsorbed on a cluster of Cu atoms emulating the Cu(100) surface (shown in the figure 1). In the results obtained with the three
functionals we have observed a red shift in this electronic level respect to the gas phase (see figure 2)

Now, and thanks to this STSM, a new collaboration between two groups of the COST Action have been consolidated. Since the first results obtained with TD-DFT are in good agreement with those at the CASPT2 level in the gas phase, we are currently working in the development of a more complex methodology to compute the electronic excited states of a molecule adsorbed on a metallic surface with a greater precision, using ab initio techniques.

FERAG_IMG1Figure 1. The cluster model used to simulate the Cu(100) surface with the molecule adsorbed.

FERAG_IMG2Figure 2. The excitation energies of the acrylamide in the gas-phase and on the cluster model.

STSM by Marcos del Cueto, Universidad Autónoma de Madrid (ES) with Geert-Jan Kroes, Leiden University (NL)
On March 02, 2015 (91 days)
From SPAIN to NETHERLANDS

Theoretical study of molecular scattering and dissociative adsorption on surfaces

Diffractive scattering is a technique extensively used to study the topology of surfaces and gain insight in the atom/molecule – surface dynamics. This process may also shed light on molecular dissociative chemisorption on surfaces, which is of special interest in the field of heterogeneous catalysis.
We have used a quantum treatment of the H2/LiF(001) system using the SPO-DVR implementation proposed by Prof. Kroes’ group [1], and we intend to compare our results with previous experimental surface analysis results at grazing incidence using fast atom/molecule diffraction, that show a strong dependence with respect to the crystallographic incidence direction studied [2-3]. In addition, we have studied the dissociative adsorption of HCl molecules on a Au(111) surface (see Fig. 1) by performing AIMD simulations, which produce results that can be compared to experimental data obtained by the group of Prof. Alec Wodtke [4].
During this collaboration we have been able to set up both systems and obtain promising preliminary results. We expect to publish complete results shortly.

MARDEC_imgFigure 1: Scheme of a HCl molecule motion on a Au(111) surface. The molecule can follow one of the two pathways depicted in the figure, leading to a) scattering or b) adsorption.

References:
[1] – G. J. Kroes, Prog. Surf. Sci. 60, 1 (1999)
[2] – P. Rousseau et al, J. Phys. Conf. Series 133, 012013 (2008)
[3] – H. Winter. Private communication
[4] – A. Wodtke. Private communication

STSM by Marta Tarkanovskaja, University of Tartu (EE)  with Edwin Kukk, University of Turku (FI)
On May 18, 2015 (7 days)
From ESTONIA to FINLAND
MATAR_logo

Partial ion yield study of gas-phase acetamide and acetic acid clusters

Clusters of a variety of molecules are receiving increasing attention due to thier unique size-dependent physicochemical properties in the transition from gas to condensed phase and wide number of possible applications in electronics, biomedicine, and materials science. Theoretical and experimental investigations of molecular clusters structure and properties is an attractive growing field of research.

We used vacuum ultraviolet (VUV) photoionization mass spectroscopy and partial ion yield (PIY) technique to study gas-phase homogeneous clusters of acetamide and acetic acid molecules produced by the supersonic expansion source in order to explore their electronic properties as a function of their size. We were able to produce acetamide clusters containing up to eight molecules (Fig. 1) and acetic acid clusters containing up to seven molecules. From the PIY measurements, PIY curves were extracted showing yield of ions as a function of photon energy. Analyzing the slopes of these curves, appearance energies of acetic acid clusters up to tetramer and acetamide clusters up to hexamer were experimentally determined.

The obtained results allow to learn novel information about dissociation patterns and fragmentation pathways of the acetamide and acetic acid clusters followed by valence region ionization. Comparison of these two compounds can specifically give an answer concerning the role of the -NH2 or -OH functional groups on the energetic properties of the acetic acid or acetic acid amide clusters. To conclude, the goal of this scientific mission was achieved – data analysis was finalized and writing the article about homogeneous acetamide clusters PIY study has begun.

MATAR-figure

Figure 1. Positive ion time of flight spectrum of acetamide clusters measured at hʋ = 9.8 eV. The numbers correspond to the amount of acetamide molecules contained in a protonated cluster.

STSM by Manuel Lara Astiaso, Universidad Autónoma de Madrid (ES) with Christoph Meier, IRSAMC – Université Paul Sabatier III, (Toulouse (FR)
On February 13, 2015 (64 days)
From SPAIN to FRANCE

MANLA_logos

Controlling the harmonic spectrum of diatomic molecules

The process of generating high-order harmonics is a result of the non-linear response of the electrons in a strong laser field, and leads to the emission of light of much higher frequency than that of the driving laser. One of the most appealing applications of HHG is the generation of attosecond pulses of light, which can in be used in time-resolved pump-probe experiments, to resolve physical processes at such timescales.

We analyzed to which extend the harmonic spectrum can be modified by using shaped laser pulses, starting with chirped pulses in the H2+ molecule. As major new finding we show that the sign of the chirp plays a crucial role, with identical spectrum.

In this context, two distinct situations have been considered: the first one considers pulses of constant pulse duration, the second one of constant spectrum.

In the case of a constant pulse duration, chirping the pulses inevitably means broadening the spectrum, which is at the origin of the previously documented chirp effects. However, in our case, we find significant differences for time-symmetric pulses having exactly the same spectrum, i.e. it is the appearance of the different colors within the laser pulse which -in combination with the electron dynamics- leads to a different HHG process.

This simple model of collinear laser-molecule interaction is being used to get deeper insights of the chirp effects in the coupled electron-nuclear dynamics. The numerical much more time consuming simulations shall elucidate if the observed chirp sign effect is still visible, or even enhanced within this more realistic description. The upcoming results of this STSM are to be presented at the XXIX International Conference on Photonic, Electronic, and Atomic Collisions (ICPEAC 2015). A publication intended to a refereed journal is also in preparation.

MANLA-imgFigure: Chirp effects on harmonic generation. The harmonic yield is greatly enhanced near the cutoff frequency, especially for the down-chirped pulse (green) when normal intensities are applied. In the high-intensity regime, up chirps (red) become more efficient to extend the cutoff.

STSM by Zdenek Masin, The Open University (UK) with Olga Smirnova, Max Born Institute, Berlin (DE)
On February 17, 2015 (12 days)
From UNITED KINGDOM to GERMANY

Tracking coupled electronic-nuclear dynamics at conical intersections in NO2

The purpose of the STSM was to generate the data required to model high harmonic spectra for NO2 which include the effects of the coupled electronic-nuclear dynamics. Specifically, the data obtained will be used to probe the mixing amplitudes of the electronic states at the conical intersection and to track the footprint of the mixing in the high harmonic spectra.

The work carried out concerned optimization of the UKRmol suite of codes that was used to generate the recombination dipoles between the bound and the continuum states of NO2.

For the present application the recombination dipoles are required for relatively high photon energies (up to approximately 80eV), i.e. for electron energies up to approximately 70eV. For electron energies much larger than 10-15eV the unbound electron’s wavefunction oscillates rapidly making it very hard to represent accurately using the methodology implemented in UKRmol (i.e. using Gaussian-type orbitals). We have overcome this problem using the new parallel integral core of the UKRmol suite which has the capability to generate the required molecular integrals in quadruple precision. The original code (running on 5 nodes on the MBI cluster) took approximately 5 hours to calculate integrals for one geometry (in quad precision). After optimization the compute time has been reduced to just under 2 hours per geometry.

The success in overcoming difficulties with representation of the continuum by employing the quad precision code is demonstrated in Fig. 1 where the total photoionization cross section for NO2 for one (non-equilibrium) geometry is shown as calculated using the double precision and the quad precision code. The calculations using the double precision code employed a smaller continuum basis set (in order to guarantee numerical stability) while the calculations in quad precision used a larger continuum basis. The calculations carried out using the quad precision code show no signs of numerical instabilities and an excellent quality of the continuum.

The main outcomes of the STSM included optimization of the parallel molecular integral transformation routines and a utility program to compute relative phases between Dyson orbitals computed for different geometries of NO2. The relative phases are obtained computing the overlap integrals between a pair of Dyson orbitals: the sign of the overlap integral corresponds to the relative phase between the orbitals. The details of the scattering calculations and the results obtained will be published in a publication that is in preparation.

fig1

Figure 1: Total photoionization cross section for NO2 (non-equilibrium geometry) obtained using a Close-Coupling scattering model and with a small and a large continuum basis. The small continuum basis was obtained using double precision and deleting those orbitals from the basis which caused the most severe numerical problems. The large continuum basis kept all available continuum orbitals in the basis and used quad precision to compute the molecular integrals.