TDDFT alternative for photoionisation of the water molecule
The main purpose of this work is to study various models to treat the photoionisation of the water molecule. This topic is of very hot interest because of the biological importance of water molecules. Possible models are the strong field approximation (SFA) and a model based on separable potentials and from which SFA can be derived as a first order approximation.
Being an expert in the field, Prof. Decleva shed some light on the simplest ways to adapt my existing separable potentials model code to molecular calculations using widely spread Gaussian type orbital basis sets.
As an outcome of this visit, I developed a working prototype of the code based on the separable potential model for water molecule in a 6-31G basis. Moreover, in Trieste we have discussed a workplan for the nearest future, and decided to compare separable potential model results with those obtained by solving the time-dependent Schroedinger equation for a water molecule in the single active electron approximation.
Simulations of doubly charged fullerene clusters
In this short term scientific mission (STSM) we continued our collaboration between Stockholm University and the University of Innsbruck to investigate the stability of doubly charged fullerenes. In experiments it was found that the fullerene pentamer is the smallest fullerene cluster which can accommodate two charges without undergoing Coulomb explosion.
Initiated by a previous STSM we investigated the stability of doubly charged fullerene clusters by means of density functional theory (DFT). Although the pentamer dication is thermodynamically unstable, Coulomb explosion is hindered due to a barrier in the potential energy surface for the release of a singly charged fullerene. We also established two simple models based on the van-der-Waals interaction of the neutral fullerene dimer and simple, electrostatic considerations.
In this STSM we used one of these simple models to carry out molecular dynamics simulations. Thereby the fullerene clusters are replaced by metallic spheres. In a first attempt we investigated small fullerene clusters below the pentamer to compare our results to results from DFT. We plan to continue the investigations and apply our model to systems larger than the pentamer.
Simulating resonantly enhanced strong-field ionization with shaped femtosecond pulses
Our understanding of strong-field ionization is still rudimentary due to the complex interplay of multiphoton transitions between initial, final, and intermediate resonant states, their dynamic Stark shift, the ponderomotive potential and many more fundamental processes. Strong laser pulses are necessary to investigate these processes and the results can be measured e.g. as photoelectron spectra. The question tackled in this STSM was, how the signals and dynamics of strong-field ionization change if different parameters of the laser pulse are varied. To answer the question, we used our previously developed method to simulate molecular strong-field ionization (SFI) in the presence of vibrational motion. Within this method, the ionic continuum is described by Legendre polynomials and the treatment of intermediate non-resonant states of the yet neutral molecule is simplified by the so-called adiabatic elimination of off-resonant neutral states.
We investigated pulses with a so-called triangular phase, whereby a pulse can be separated into two subpulses with a tunable time delay between them. As a result of such pulses, we obtained interestingly shaped photoelectron spectra in our simulations. The system under study is a one-dimensional model for Iodobromomethane (CH2BrI) including four electronic states of the neutral and three ionic states. Looking at the photoelecton spectrum, we found additional peaks when using shaped laser pulses compared to the outcome with unshaped pulses. Further investigation revealed that the new peaks stem from the same electronic states as the previously observed peaks, i.e., a peak originating from D1 splits into two. Further investigations and comparison to experiment are necessary to further understand these results.
Simulation of time-resolved photoelectron spectroscopy along nonadiabatic dynamics trajectories
The goal of the two week scientific mission was preparing a code for simulating photoelectron spectroscopy observables along nonadiabatic dynamics trajectories. To achieve this, changes had to be made in the input part of the code developed by prof. Decleva and co-workers for calculating photoionization observables to accommodate easy interfacing with output from trajectory based nonadiabatic dynamics simulations.
A new subroutine was added to the code based on the separation of the B-spline basis into two parts, a set of atom centred knots for the description of the short range interactions and a grid of linear knots for the description of the continuum. Convergence of the basis set was tested for three key geometries taken from a nonadiabatic dynamics simulation of the pyrrole molecule.
The modified code is easy to interface with a nonadiabatic dynamics program and can be used to calculate photoionization observables without losing accuracy for a wide range of geometries using a benchmark method. Once the basis set is shown to be converged on a single (or a few) geometry of a system of interest, it is safe to assume that accurate results can be obtained along an entire dynamics run.
The group of Fernando Martin in Madrid (Spain) offers the possibility to develop a research project on Theoretical Attosecond Electron Dynamics, oriented to obtain a PhD diploma, to theoretically investigate the coupled electron and nuclear dynamics induced by attosecond laser pulses and strong electromagnetic fields on small and mid-size molecules, as well as in solids.
The position shall be funded by the doctoral fellowship programme INPhINIT, which is devoted to attract international Early-Stage Researchers (ESR) to top Spanish research centres. INPhINIT is promoted by the “la Caixa” Foundation and relies on the European Commission’s support through the Horizon 2020 Marie Skłodowska-Curie Actions – COFUND programme.
The fellowship shall cover a 3-year doctoral employment contract with good remuneration conditions (gross salary 26.000 € per year) in comparison with the standard of living in Spain, and a top up contribution for training and networking activities. Researchers shall complement their training with a variety of transnational, intersectoral and interdisciplinary activities.
In addition, phd candidates may opt to a price amounting to 7.500 € if they got the diploma earlier than 6 months after the finalization of the contract.
For more information on the fellowship programme, please visit: www.inphinitlacaixa.org
More information on the PhD position on Theoretical Attosecond Electron Dynamics can be found here: phd-position-descrption. If selected, researchers should join the Condensed Matter Physics Center (IFIMAC) by September 2017.
In case you are interested in this fellowship position and consider you fulfil the excellence criteria and other specific call requirements (research experience, training, language and mobility requirements), please, do not doubt to submit you application here: https://www.lacaixafellowships.org/index.aspx, before February 10th, 2017.
The Department of Physics has an opening for an assistant professor in theoretical atomic and molecular physics (Reference number SU FV-1610-16)
Atomic, molecular and chemical physics has been identified as one of the profile areas at Stockholm University. In this field there are broad and highly successful experimental as well as theoretical activities.
Main responsibilities are research and, in addition, some teaching and supervision.
Deadline for applications: 2 December 2016.
More information here.
Scientists can now directly track the locations of all the atoms of an entire molecule while one of its bonds breaks and a single proton escapes.
Source: Dr. Alina Hirschmann (Corporate Communications – ICFO)
Imagine what it would be like to watch how the individual atoms of molecules rearrange during a chemical reaction to form a new substance, or to see the compounds of DNA move, rearrange and replicate. Such capability would give unprecedented insight to understand and potentially control the processes.
The simple idea of watching how molecules break, or transform, during chemical reactions has, until now, been unfathomable since it requires tracking all of the atoms, which constitute a molecule, with sub-atomic spatial and few-femtosecond temporal resolution. Hence, taking such “snapshots” with a combined spatio-temporal resolution to witness a molecular reaction was considered fodder for science fiction. Exactly 20 years ago, one of the ideas proposed considered using the molecule’s own electrons to image its structure: Teach the molecule to take a selfie! The idea was brilliant but impossible to implement – until today.
In their recent study, reported in Science, ICFO researchers from the Attoscience and Ultrafast Optics Group in collaboration with researchers from the USA, the Netherlands, Denmark and Germany, have reported on the imaging of molecular bond breakup in acetylene (C2H2) nine femtoseconds (1 femtosecond = 1 millionth of a billionth of a second) after its ionization. The team was able to track the individual atoms of the isolated acetylene molecule with a spatial resolution as small as 0.05 Ångström – less than the width of an individual atom – and with a temporal resolution of 0.6 femtoseconds. What’s more, they were able to trigger the breakup of only one of the bonds of the molecule and see how one proton leaves the molecule.
“Our method has finally achieved the required space and time resolution to take snapshots of molecular dynamics without missing any of its events, and we are eager to try it out on other molecular systems such as chemical catalysts and bio-relevant systems” said Jens Biegert, ICREA professor at ICFO and leader of the research.
Teaching a molecule to take a selfie
The team developed a world-leading ultrafast mid-IR laser source and combined it with a reaction microscope to detect the 3D momentum distribution of electrons and ions in full kinematic coincidence. In the experiment, a single isolated acetylene molecule was oriented in space with a short laser pulse. A strong enough, follow up, infrared pulse liberated one electron from the molecule, accelerated it on a returning trajectory and forced it to scatter off its own parent molecular ion, all within only 9 femtoseconds.
Benjamin Wolter explained, “the flight path and kinetic energy of all collision fragments were recorded with the reaction microscope similar to a big particle physics experiment.”
After some clever data processing, the team was able to extract the entire molecular structure and, moreover, they could show that orienting the molecule along the electric field of the laser, or perpendicular to it, completely changed its dynamics. In one case, the molecule underwent vibrational motion with the laser field, while in the other case a C-H bond was clearly broken. The experiment is the first direct visualization of bond cleavage and observation of the proton during its departure from the [C2H2]2+ ion, something that was never seen before.
“We took one electron, steered it along a specific path with the laser and scattered it off an isolated molecule to record its diffraction pattern” said Biegert, “it is mind-boggling to imagine the length and time scales of the experiment. The fantastic cooperation between experimentalists and theorists, atomic physicists and quantum chemists from ICFO, Kansas State University, Max-Planck-Institut für Kernphysik, Physikalisch Technische Bundesanstalt, Center for Free Electron Laser Science/DESY/CUI, Aarhus University, Friedrich-Schiller University Jena, Leiden University, and Universität Kassel made it possible to achieve such feat”.
Wolter et al “Ultrafast electron diffraction imaging of bond breaking in di-ionized acetylene”, Science, 2016, Vol. 354, Issue 6310, pp. 308-312, DOI: 10.1126/science.aah3429 (http://science.sciencemag.org/content/354/6310/308)
ICFO – The Institute of Photonic Sciences, member of The Barcelona Institute of Science and Technology, is a research center located in a specially designed, 14.000 m2-building situated in the Mediterranean Technology Park in the metropolitan area of Barcelona. It currently hosts 400 people, including research group leaders, post-doctoral researchers, PhD students, research engineers, and staff. ICFOnians are organized in 23 research groups working in 60 state-of-the-art research laboratories, equipped with the latest experimental facilities and supported by a range of cutting-edge facilities for nanofabrication, characterization, imaging and engineering.
The Severo Ochoa distinction awarded by the Ministry of Science and Innovation, as well as 13 ICREA Professorships, 21 European Research Council grants and 6 Fundació Cellex Barcelona Nest Fellowships, demonstrate the centre’s dedication to research excellence, as does the institute’s consistent appearance in top worldwide positions in international rankings. From an industrial standpoint, ICFO participates actively in the European Technological Platform Photonics21 and is also very proactive in fostering entrepreneurial activities and spin-off creation. The center participates in incubator activities and seeks to attract venture capital investment. ICFO hosts an active Corporate Liaison Program that aims at creating collaborations and links between industry and ICFO researchers. To date, ICFO has created 5 successful start-up companies.
Next XLIC Expert Meeting will join WG1 and WG2 topics under the title “From Ultrafast to Ultraslow Dynamics in Molecules and Clusters”. It will be held in the Weizmann Institute of Science Israel , from 23th to 25th January 2017.
The workshop will bring together top researchers in a wide range of fields with the hope of establishing new interactions and future directions. The workshop participation is open to everybody and is jointly organised by COST CM1204 Action (XLIC). For more information please visit the conference website: http://www.weizmann.ac.il/conferences/UUDMC2016/
Abstract Submission Deadline: November 1st, 2016
Registration Deadline: January 5th, 2017
List of Invited speakers:
Noam Agmon, Hebrew University, Israel
Lars H. Andersen, Aarhus University, Denmark
Itzik Ben-Itzhak, Kansas State University, USA
Valerie Blanchet, CELIA, Bordeaux, France
Anastasia Bochenkova, Moscow State University, Russia
Steen Brondsted Nielsen, Aarhus University, Denmark
Philip Bucksbaum, Stanford, USA
Francesca Calegari, Politecnico Milano, Italy
Lorenz Cederbaum, University of Heidelberg, Germany
Henrik Cederquist, Stockholm University, Sweden
Brett Esry, Kansas State University, USA
Sharly Fleischer, Tel-Aviv University, Israel
Jason Greenwood, Queen’s University Belfast, UK
Christiane Koch, Universität Kassel, Germany
Ronni Kosloff, Hebrew University, Israel
Holger Kreckel, MPI-K Heidelberg, Germany
Stephen Leone, UC Berkeley, USA
Nimrod Moiseyev, Technion, Israel
Edvardas Narevicius, Weizmann Institute, Israel
Daniel Neumark, UC Berkeley USA
Thomas Pfeifer, MPI-K Heidelberg, Germany
Igor Schapiro, Hebrew University, Israel
Haruo Shiromaru, Tokyo Metropolitan University, Japan
Jan. R. R. Verlet, Durham University, UK
Mathias Weber, JILA, Colorado, USA
Roland Wester, Universität Innsbruck , Austria
Local Organiser: Yoni Toker (Bar Ilan University)
2nd WG1 Meeting “Ultrafast electron dynamics in molecules” (COST Action CM1204)
29-30 August 2016
The second WG1 meeting of COST CM1204 Action was organized by Prof. Olga Smirnova and Dr. Adam Kirrander. It was aimed at presenting advances of all the nodes participating in the WG1 of the action, as well as to discuss problems and promote collaborations between all partners.
The meeting was organized into 6 sessions. Each session was moderated by a discussion leader. Each session opens with 10 min introduction to the field, presented by a discussion leader. The introduction was followed by 3 or 4 talks, 20 minutes each (without the questions). Each session was concluded by a 30 minutes general discussion involving 3 or 4 speakers (altogether at the stage, see pictures below) on the topics of their talks and topics suggested by the the discussion leader, who guided this discussion. The audience participated very actively in these discussions. 3 hot-topics were selected from contributed abstracts. The meeting also included 2 poster-sessions.
The number of participants was 78.
The final program of the meeting can be found below.
The Local Organiser,
Dr. Olga Smirnova
Max-Born strasse 2a, 12489 Berlin
- 2nd WG1 meeting (Edinburgh, UK) - Short Programme (75 downloads)
- 2nd WG1 meeting (Edinburgh, UK) - Programme (79 downloads)
- 2nd WG1 meeting (Edinburgh, UK) - Conference Picture (101 downloads)
Ion induced fragmentation studies of halouracil molecules
The main objective of this STSM was to work on the experimental results previously obtained in the ion induced fragmentation of 5-BrUracil (5BrU) and 5-FUracil (5FU) at the GANIL ion beam facility in a collaboration between the CNR-ISM (Rome, Italy) and the CIMAP (Caen, France). These molecules are halogen substituted analogues of uracil molecule with radiosensitizing properties. In order to understand their fundamental mechanisms of radiosensitisation, it is essential to gain a clear characterization of their interaction with ionizing radiation in a ‘realistic’ biological environment mimicked by embeding them into pure and nano-hydrated clusters.
It is found that the environment has an overall ‘protecting’ effect, reducing the damage and the yield of low mass fragments. However, it is also responsible for the opening of new fragmentation channels and formation of ‘new’ species as a result of the altered molecular bonding conditions. The most striking result of the study is the appearance of a large number of hydrated fragments formed most probably due to a very strong water-molecule interaction holding the water clusters bound to the 5BrU molecule.
The main results will be published in an article (in preparation) where the discussion will be focused on how the presence of the Br atom in position 5 of the ring affects the fragmentation mechanisms of the uracil molecule  as well as the role of the environment in form of surrounding molecules of the same species or with the inclusion of water molecules in the fragmentation dynamics of 5BrU.
Figure 1. The 36 keV 12C4+ ion induced mass spectrum of the 5BrU molecule (a), pure 5BrU clusters (b) and nano-hydrated 5BrU clusters (c) in the m/z region up to the monomer.
- Pal Markush, Paola Bolognesi, Antonella Cartoni, Patrick Rousseau, Sylvain Maclot, Rudy Delaunay, Alicja Domaracka, Jaroslav Kocisek, Mattea C. Castrovilli, Bernd A. Huberc and Lorenzo Avaldi. Phys. Chem. Chem. Phys., 2016,18, 16721-16729.