Blog Archives

The 3rd Young Scientist Forum (YSF) of XLIC Action – a special half-day with talks given by young researchers (PhD students and post-docs) will take place in Prague (CZ) on March 2017 as a part of the 4th and final XLIC Action General Meeting (COST Acton CM1204, 14-16 March 2017).

Young Scientist Forum will include 12 lectures, out of which 6 oral contributions will be chosen by YSF committee based on submitted abstracts. The deadline for abstract submission for YSF is 31st January 2017.

Applicants asking for the talk at YSF are also required to submit a short CV which is to be emailed to xlic2017@jh-inst.cas.cz. Abstracts submitted after the deadline will not be considered for the selection. For more details see http://www.jh-inst.cas.cz/xlic2017/home and  http://www.xlic.eu. You can also contact A. Domaracka (domaracka@ganil.fr).

Please note that, selected YSF speakers can ask for financial support from XLIC COST Action.

Spectroscopy has taught us how the very precise measurement of resonance lineshapes gives insight into the structure of matter. However, as a time-integrated measurement, the spectral lines give only indirect information on the underlying electronic dynamics. The resonance width can be related to the timescale of the electronic excitation and relaxation, but, in the general case, this is not enough for accessing the details of the full dynamics that have to be recovered from advanced modeling. A typical case is the one of autoionizing resonances, where the system (atom, molecule, nanostructure) can be ionized either directly to the continuum or be trapped in a very excited state for a very short time (femtosecond) before reaching the continuum. The interference between the two channels results in an asymmetric lineshape, called Fano profile after the Italian theoretician Ugo Fano who first modeled this process. While the Fano profile has been extremely successful in analyzing the absorption lines measured in a wide variety of systems, the details on how the process unwraps in time have remained elusive, the ultrashort timescale at stake precluding direct time-domain investigations.

In the November 11 issue of Science magazine, two articles tackle the problem of watching the buildup of the helium 2s2p Fano resonance from two different perspectives: from the ‘inside’ and from the ‘outside’.

In the article entitled “Observing the ultrafast buildup of a Fano resonance in the time domain” (DOI: 10.1126/science.aah6972), experimental physicists from the MPI for Nuclear Physics (MPIK, Heidelberg), together with theoretical physicists at the Vienna University of Technology and the Kansas State University look at the autoionizing process from ‘inside’ the atom by measuring the time-dependent dipole response in transient absorption spectroscopy. The dipole response being determined by the electron dynamics close to the nucleus, it provides a detailed picture of what takes place ‘inside’ the atom undergoing autoionization. In this work, short bursts of XUV light around 60.15 eV trigger the dynamic buildup of the Fano resonance by inducing an oscillating dipole moment, which in turn gives rise to the optical dipole response of the transition. A time-delayed ultrashort infrared pulse is then used to strong-field ionize the system, interrupting the autoionization process. The measured time-gated dipole response shows how the absorption lineshape evolves from an initially broad distribution to the characteristically ‘narrow’ converged Fano profile.

In the article “Attosecond dynamics through a Fano resonance: Monitoring the birth of a photoelectron” (DOI: 10.1126/science.aah5188), another team composed of experimental physicists from the CEA-CNRS-Université Paris-Saclay (CEA-Saclay) and theoretical chemists and physicists at the Université Pierre et Marie Curie (UPMC-Paris) and Universidad Autónoma de Madrid look at the autoionizing process from ‘outside’ the atom by measuring the time-dependent outgoing wavepacket, i.e. by probing the photoelectron itself. Using spectrally resolved electron interferometry, they could measure the spectral amplitude and phase of the resonant wave packet. In this scheme, replicas obtained by perturbative two-photon transitions interfere with reference wave packets that are formed through smooth continua, allowing the full temporal reconstruction, purely from experimental data, of the resonant wave packet released in the continuum. In turn, this allows resolving the ultrafast buildup of the autoionizing resonance, revealing the decomposition of the process in two nearly consecutive steps governed by fairly different time scales: during the first 3 fs, the direct ionization channel dominates; then, the resonant path starts contributing as the doubly excited state decays in the continuum, resulting in interferences between the two channels that ultimately shape the celebrated Fano profile.

These two complementary studies illustrate the large potential of the diverse techniques developed in attosecond spectroscopy: detection of photons or electrons, time-domain versus frequency-domain measurements, strong-field vs. perturbative regime. They open multiple opportunities for studying ultrafast strongly correlated dynamics in a variety of systems, from molecules and nanostructures to surfaces, and controlling matter changes at a most fundamental level.

(left) Absorption spectra measured for a series of XUV-IR delays from 6 to 32 fs (from DOI: 10.1126/science.aah6972).
(right) Experimentally-retrieved photoelectron spectrum for accumulation times from -10 to 20 fs (step=1fs) (from DOI: 10.1126/science.aah5188)

Contacts:
Richard Taieb, UPMC (richard.taieb@upmc.fr)
Thomas Pfeifer (thomas.pfeifer@mpi-hd.mpg.de)

STSM by Patrick Rousseau, Université de Caen Normandie FRT) with Per Johnsson, Lund University (SE)
On July 29, 2016 (9 days)
From FRANCE to SWEDEN

XUV attosecond ionisation of ferrocene: fragmentation and charge dynamics

How charge and energy redistribute in a complex molecular system? What are timescales of subsequent electronic and nuclear dynamics? These questions are the main topics of the present STSM.

In the Lund Laser Centre, in collaboration with the group of Per Johnsson, we have investigated the ionisation of ferrocene by XUV attosecond pulse trains (APTs). This organometallic molecule [Fe(C5H5)2] is formed by an iron atom in sandwich between two aromatic rings. During this one week STSM, we successfully obtained results on the ionisation/fragmentation of the ferrocene which paved the way for a next experimental campaign on time-resolved measurements.

We have measured the fragmentation mass spectra following the ionisation by XUV APT. The molecular fragmentation is reduced as shown by the intense peak of intact molecule. Moreover due to the photon energy a good signal of the intact molecular dication is also observed. Covariance measurements have been also obtained and their analysis is under progress. Together with fragmentation patterns, the obtained results during this STSM will allow to select some decay channels to be specifically studied using XUV pump-XUV probe time resolved technique.

COST Action CM1204 (XLIC) will end on April 30th, 2017, but you can still participate in the last Action activities and take the opportunity to move forward in your joint research activities by performing the last short research missions (STSM).

If you need XLIC support to fund these missions, you can find information on how to apply here. Please, note that missions should be performed withing the Action lifetime and the deadline to apply is March 15, 2017.

Infromation on the last activities co-organised by XLIC Action can be found in the links below:

  • XLIC Experimental Training School: “The frontiers of attosecond and ultrafast X-ray science”. March 19-28, 2017
    Directors: Louis Di Mauro, Alicja Domaracka, Mauro Nisoli, Sergio Martellucci
    External meeting website
    Ettore Majorana International Centre (Erice, Sicily, Italy)
  • 4th XLIC General Meeting. March 14-16, 2017
    (Prague, Czech Republic)
    LO: Miroslav Polasek
    External meeting website
  • WG1 & WG2 Expert Meeting “From Ultrafast to Ultraslow Dynamics in Molecules and Clusters”. Jan 23-25, 2017
    Weizmann Institute of Science (Rehovot, Israel)
    LO: Oded Heber
    External meeting website

 

 

STSM by Oded Heber, Weizmann Institute of Scoence (IL) with Lars Andersen, Aarhus University (NO)
On October 24, 2016 (19 days)
From ISRAEL to NORWAY

Long time molecular internal dynamics controlled by ultrashort times between photons absorption

Molecular internal dynamics is a most important process in many basic and applied researches. Among them for example is a major astrophysics phenomena like the infra-red spectrum related to polycyclic aromatic hydrocarbon (PAH) that might be related also to the origin of life. Theoretical descriptions of internal dynamics via time dependent quantum mechanics are limited to short term processes up to picoseconds time scales. For longer time scales the only practical description can be done via statistical models. The bridge between the calculation based entirely on the time dependent Schrodinger equations and statistical models is crucial to understand and describe actual molecular dynamics. In the last few years we have developed the capability to observe experimentally the long time internal dynamics of excited molecules after photo absorption and to describe the results theoretically using a statistical model. Among the the basic assumptions in this description is that the molecule absorbs one photon on a short time scale and that subsequently an internal conversion process (IC) happened fast (evolution of electronic and nuclear wave packet) so the initial electronic excitation is statistically distributed over others degrees of freedom of the molecule that relax via much slower processes. For C6- as well as for other molecules, we found that the long time relaxation process is the same for single photon absorption of energy E as for two-photon of energy E/2 when using nanosecond laser pulses. The essential question addressed in the present work is how the IC process evolves in the time between the first and the second photon absorptioni.
We have utilized the unique system at Arhus University that include a femto second pump-probe laser system with tunability of the energy of the first (pump) and second photon (probe) as well as the time delay between them. All this is combined with ion beam facility that allows storage of ions in the electrostatic storage ring SAPHIRAii.
During the experiment, we produced C6- ions and stored them in SAPHIRAii where the ions were cooled for 17 (or 42) msec. After this time a laser pulse (~100fsec) was merged with the ions over one straight section of the ring. A second laser pulse was subsequently merged with the same ions after a variable delay time of -1500 fs to +9000fs. The much longer delayed production of neutral fragments, i.e. resulting from the IC process, was measured at the end of the next straight section of SAPHIRA ~8-15 micro second after the two laser shots. Preliminary results are presented in the figure. An immediate conclusion is that the internal dynamics occurring in a time scale of hundreds of femtoseconds can influence significantly the delayed electron emission time delays that are many orders of magnitude slower.

The data analysis, the exact processes and models are now under work for future scientific publication.

Position: Early Stage Researcher (PhD) in the framework of the Marie Skłodowska-Curie Actions (MSCA) Innovative Training Networks (ITN) H2020-MSCA-ITN-2014 MEDEA 641789

Website: http://www.medea-horizon2020.eu/

Institution: Albert-Ludwigs-University Freiburg, Germany

Duration: four years (from 01.01.2017)

Synthetic description of the project:

The project is focused on experiments to be performed at Free Electron Lasers (FELs), and, in particular at the FEL FERMI, that delivers tunable XUV pulses with a bandwidth between 30 and 90 meV. Coherent control schemes in the XUV spectral range exploiting the unique properties of the FEL FERMI will be investigated. In particular, the ESR will investigate how the combination of multi-color coherent XUV radiation can be used to control the photoionization process and electronic dynamics in inner valence shells of atoms and molecules. Finally, she/he will also investigate novel approaches for the generation of attosecond pulse trains using XUV FELs.

The work will be conducted in close collaboration with the atomic/molecular/ and optical physics group of the Elettra Sincrotrone led by Dr. Kevin Prince and Dr. Carlo Callegari.

Contact:

Prof. Dr. G. Sansone
Physikalisches Institut der
Albert-Ludwigs-Universität
Stefan-Meier-Str. 19
79104 Freiburg
Tel.: (+49)/(0)761-203-5723
FAX (+49)/(0)761-203-5955
giuseppe.sansone@physik.uni-freiburg.de

STSM by Lorenz Kranabetter, Leopold-Franzens-Universität Innsbruck (AT) with Harold Linnartz, University of Leiden (NL)loka-logos
On October 24, 2016 (20 days)
From AUSTRIA to NETHERLANDS

PAH photo dynamics linked to fullerene formation Using an ion trap time-of-flight mass spectrometer

To better understand the photo chemistry of Polycyclic Aromatic Hydrocarbons (PAHs), which are believed to play an important role in the carbon-cycle of the interstellar medium (ISM), we investigated the effects of the irradiation by a near infra-red (NIR) laser for the PAH Quinone 7 (C28H12O2).

i-popFigure 1: A sketch of the experimental setup [J. Zhen et al,; Doi: 10.1016/j.cplett.2013.12.005 ].

In the experimental setup a cloud of ionized molecules is trapped in a linear ion trap. After an initial size selection via a stored waveform inversed Fourier transformed pulse the sample is irradiated with light from a Nd:YAG laser and then the Paul trap is discharged towards a time of flight mass spectrometer. The resulting mass spectra give insight into the photo induced fragmentation processes of Quinone, i.e., show which channels are preferred and consequently which molecules form upon dissociation.

The results obtained during this short COST funded research collaboration between Leiden Observatory and the University of Innsbruck are interesting, as they extend on similar work on pure CnHm PAH species. Obviously the CO groups in Quinone offer additional reaction channels. Moreover, this study provides valuable expertise and knowledge that will be a great advantage when we adapt one of the setups in Innsbruck to study the photo processing of PAHs and fullerenes in Helium Nano Droplets. Those droplets provide a unique matrix environment that shares some important characteristics with the ISM and do not avert NIR Spectroscopy.

The 4th and final XLIC Action General Meeting (COST Acton CM1204) will take place in Prague (CZ), on March 14-16, 2017.  The registration is already open (http://www.jh-inst.cas.cz/xlic2017/registration).

This last general meeting of the XLIC Action will be a great opportunity to share with your colleagues the results derived from networking activities within the Action and try to ensure the maintenance of collaborations now that XLIC Action is about to finish.

The Meeting will also include the 3rd Young Scientist Forum (YSF) – a special half-day with talks given by young researchers (PhD students and post-docs). Part of the speakers on the YSF will be selected among those young researchers sending an abstract.

Please visit the meeting and XLIC websites for more information: http://www.jh-inst.cas.cz/xlic2017/home   and http://www.xlic.eu

Important deadlines: Abstract submission: January 31, 2017; Accommodation: February 14, 2017.

Looking forward to see you in Prague
Miroslav Polášek.                                                                                         Manuel Alcami
Local Chair of the meeting                                                                         Chair of the XLIC COST Action
Heyrovský Institute of Physical Chemistry                                              Departamento de Química
Academy of Sciences of the Czech Republic                                           Facultad de Ciencias – Modulo C-13
Dolejškova 2155/3, 182 23 Praha 8                                                          Universidad Autónoma de Madrid
Czech Republic                                                                                             28049 – Madrid (Spain)
tel.: (+420) 266053066, (+420) 266053299                                          Tel: +34 914973857
fax:  (+420) 286582307
e-mail: miroslav.polasek@jh-inst.cas.cz                                                 e-mail: manuel.alcami@uam.es

The International school on “The Frontiers of Attosecond and Ultrafast X-ray Science” will be held from 19th to 28th March 2017 in Erice, Sicily, Italy.

The primary objective of this new school is to educate the next generation of scientists who will impact the future of attosecond and ultrafast x-ray science. We anticipate that the school will meet on a regular basis every two years and become a foundation for the ultrafast community. Consequently, the main topics of the course are the following: (i) attosecond science and technology, devoted to the generation and application of attosecond pulses to the investigation of electronic dynamics in atoms, molecules, nanostructures and condensed phases; (ii) fundamentals, methods and applications of free electron lasers, synchrotron radiation, ion collisions in atomic and molecular science. Lectures will cover current developments in theory and experiments but are also intended to give the basics of the field.

Please note that, PhD students and post-docs willing to attend the school can apply for scholarships (deadline 30 January 2017). For more details see: http://www.erice-attosecond.it/registration

The school co-organised by XLIC COST Action and sponsored by Politecnico di Milano, Italian Ministry of Education and Scientific Research, Sicilian Regional Parliament, ELI-ALPS and Ettore Majorana Foundation and Centre for Scientific Culture.

The organizers,

Louis Di Mauro, Alicja Domaracka, Mauro Nisoli and  Sergio Martellucci

The research group “Femtosecond spectroscopy and ultrafast laser control” of Prof. Thomas Baumert at University of Kassel is looking for a

PhD student (f/m).

Salary will be according to TV13 / 2.

Topic:
The everyday phenomenon of chirality has been fascinating scientists and philosophers for centuries. Molecular chirality, especially, plays an important role in the fundamental building blocks of nature. It is also crucial for human health as the positive or negative effects of pharmaceuticals can depend on the chirality of its active ingredients. Furthermore, chiral molecules act as versatile testbeds in fundamental physical sciences.
Within a large research effort, our groups strives to understand and control molecular chirality on a microscopic level. Therefore, we investigate isolated molecular quantum systems in the gas phase using state-of-the-art methods of molecular physics. The specific task of this PhD project is to invert chirality of a molecule using ultra short laser pulses.
The PhD student will have to perform experiments in the lab, to evaluate the data using computational methods and to present the results on scientific conferences and through publications in peer-reviewed journals.

Prerequisite:
– MSc or equal in physics or physical chemistry with very good marks.
– Good experimental skills in at least one of the following fields: Ultra short laser pulses, high-vacuum techniques and charged-particle detection.
– Ability to work in a team, high motivation and capability to work independently.

The city of Kassel:
Kassel (c. 200 000 inhabitants) lies in the geographic center of Germany and is connected very well to various modes of the transportation network. The city hosts the famous Documenta exhibition for contemporary arts and has about 24 000 students. The high recreational value of the area is underlined by the presence of both world cultural heritage (Bergpark Kassel) and world natural heritage (Kellerwald), while housing is relatively cheap compared with other large cities in Germany.

Our research group:
Find out more about our research on our webpage (www.uni-kassel.de/go/femto). It also holds first visual impressions of our labs (www.uni-kassel.de/go/bilder).

Contact:
Interested? Please send your complete application to Prof. Thomas Baumert or Dr. Arne Senftleben. Email addresses can be found on the webpage. Please do not hesitate to contact us by phone.