The J.R. Macdonald Laboratory, Physics Department, Kansas State University, is seeking three or more FELLOWS (POSTDOCS) in experimental ultrafast atomic, molecular and optical (AMO) physics. The Laboratory has two state-of-the-art CEP-stable lasers — a 10 kHz, 2 mJ, 21 fs laser and a 1 kHz, 20 mJ, 25 fs laser with an OPA to generate few-cycle pulses in the mid-IR — that are enabling new experiments aimed at studying ultrafast light-induced dynamics in atoms, molecules, and nanostructures.
More information is available in this website: https://www.phys.ksu.edu/jobs/2016/jrm.html and this document: [Download not found]
COST WG1 meeting (August 29, 2016 – August 30, 2016, Edinburgh, UK) is approaching.
Abstract submission for the WG1 meeting is now open. Submission deadline is June 20.
7 hot topic talks will be selected from all submitted abstracts.
Please send abstracts to: email@example.com and Adam.Kirrander@ed.ac.uk and use the subject line: Edinburgh COST WG1 abstract.
The on-line link for booking the rooms will appear soon.
Do not miss the opportunity to attend the Faraday discussion on ‘Ultrafast imaging of photochemical dynamics’, which will also take place in Edinburgh on August 31-Sept 2, see: http://www.rsc.org/ConferencesAndEvents/RSCConferences/FD/Photodynamics-FD2016/index.asp
Abstract (poster) submission deadline for the Faraday discussion is June 20
Brief programme for the WG1 meeting
(Detailed programme can be downloaded here: 2ndWG1meeting-table)
Session 1: “Ultrafast Non-adiabatic dynamics, Surface hopping, solvent effects”.
Discussion leader: V. Engel.
Invited speakers: M. Barbatti, B. Lasorne, F. Santoro
Session 2: “Synchrotrons, ultrafast optical and X-ray absorption spectroscopies”
Discussion leader: V. Averbukh
Invited speakers: O. Travnikova, M.A. Hervé du Penhoat, C. Milne
Session 3: “Time-resolved cluster dynamics”
Discussion leader: T. Fennel
Invited speakers: D. Rolles, M. Krikunova, U. Saalman
Session 4: “Imaging and control of molecular dynamics”
Discussion leader: R. Moshammer
Invited speakers: J. Kuepper, R. Forbes, M. Richter, J. Feist
Session 5: “Multielectron dynamics in external fields: advances in theory”
Discussion leader: E. Suraud
Invited speakers: L. Madsen, A. Scrinzi, H. Bachau, S. Patchkovskii
Session 6: “New trends in attosecond spectroscopy”
Discussion leader: M. Ivanov
Invited speakers: J. Mauritsson, A. Brown, M. Dahlström, F. Lepine
Interaction of short laser pulses with atoms
During the present STSM we developed and tested a semi- classical simulation code for the study of laser-atom interactions. In our recent case we focus on the multielectron atomic systems. The interaction between the active target electron and the target nucleus mimic with the Garvey-type model potential. In the semiclassical model, it is assumed that wavepacket propagation in the post-tunneling process can be well described within the framework of the classical mechanics. The method is similar to the Classical Trajectory Monte Carlo (CTMC) method based on the inclusion of the classical phase information of the motion. Using this code we study the ionization of H, He, Ne an Ar. We also analyzed the classical trajectories individually. We sorted the events according the number of recollisions as a function of the final energy of the ejected electrons. We clearly identify and separate the regions in momentum distributions of the ejected electrons according to the number of recollisions (see Fig. 1). We analyzed the similarities and differences between the pure classical description and the semi-classical treatment of the collision problem.
Fig.1. Ionization probability densities for He atom as a function of the electron parallel and perpendicular momentum measured from the polarization vector which coincides with the Oz axis. The electric field is defined
STSM by Ignacio Sola Reija, Universidad Complutense de Madrid (ES) with Agnes Vibok, University of Debrecen (HU)
On March 28, 2016 (6 days)
From SPAIN to HUNGARY
LICCIs: Laser Induced and Controlled Conical Intersections
Whether they are chemical reactions or photophysical processes, chemists conceive most chemical processes as events occurring in the potential energy surface (PES) of a molecule. The excited PES are the main roads for large transformations, but they are quagmired with ridges and bottlenecks that quickly lead to other PES and more often than not, to the ground potential. These topological features are usually called conical intersections. A strong field completely transforms this landscape and offers the opportunity to place and design laser induced conical intersections (LICIs) to control the flow of energy and population in the excited state of molecules.
In this work our main goal was to analyze the set of quantum control techniques that could be used to control the dynamics of wave packets around LICIs. We studied the simplest set-ups that involve LICIs either as deactivation mechanisms or as drivers to the desired target, and conceived different scenarios where the control was possible or very unlikely.
As the outcome of the STSM we elaborated a short memorandum for LICCIs (laser-induced and –controlled conical intersections) and planned the first steps for a future project involving the UCM and the Debrecen groups.
Photo-induced dissociation of hydrogenated polycyclic aromatic hydrocarbons at ELISA
Pyrene (C16H10) is a Polycyclic Aromatic Hydrocarbon (PAH) consisting of four fused aromatic rings. On one hand hydrogenation of PAHs allows for enhanced deexcitation through dissociation of the additional hydrogen atoms, a fact that has been found to potentially protect the carbon backbone against fragmentation . On the other hand conversion of unsaturated carbon-carbon bonds into single bonds weakens the carbon backbone, and CID experiments have shown that this weakening effect might prevail [2,3].
During this STSM hydrogenated pyrene (C16H10+m, m = 0, 6, or 16) molecules were injected into the ELISA storage ring and overlapped with high-intensity laser pulses in the optical range (420-650 nm). We have measured action spectra and fragmentation mass distributions. We have further measured the power dependencies of the total fragmentation yield as well as the power dependencies for individual fragmentation channels.
Figure 1 shows preliminary results of the power dependencies of the total fragmentation as a function of laser pulse energy. The exponent in the power law gives the number of photons involved in the fragmentation process. This number decreases from three 2.72 eV photons for m = 0, to two 2.88 eV photons for m = 6, to one 2.95 eV photon for m = 16. This shows that photo induced carbon backbone fragmentation is more likely for hydrogenated pyrene. The results will be published in an article in a peer-reviewed journal later this year. During this STSM we have also started additional measurements on hydrogenated coronene (C24H12+m), which will set the stage for continued collaboration.
 M. Gatchell et al., Phys. Rev. A 92, 050702(R) (2015).
 M. Wolf et al., Eur. Phys. J. D, in press.
Producing cold ions in He nanodroplets for DESIREE
The focus of this STSM was to establish a partnership between groups at Stockholm University and Universität Innsbruck with the goal of developing a He droplet cluster source for the DESIREE facility. Superfluid droplets of He consisting of up to 105 atoms can be doped with other molecules or atoms. Through evaporative cooling the dopants will reach the temperature of the surrounding droplets (0.37 K). The dopants will collect at the center of the droplets where bound complexes may be formed. The droplets can be ionized by electron impact so that they can be manipulated with electric fields. This offers an efficient yet gentle way of producing ions and charged complexes for a wide range of experimental applications.
During my time with the group in Innsbruck we performed two different sets of experiments. Figure 1 shows results from a measurement of C60 anions enclosed in H2 molecules that formed in He droplets. We can see that a wide range of cluster sizes are formed and that clusters with 32 or less H2 molecules are more stable than larger clusters. This is due to shell closing where the H2 molecules align with the 32 faces of a C60 molecule (20 hexagons and 12 pentagons, see inset).
This STSM will result in two publications and the future joint development of a He droplet source for the DESIREE facility at Stockholm University.
Figure: Cluster size distribution of H2 molecules attached to C60 anions. These are produced in a He droplet and
ionized by electron impact. A shell closure is observed at 32 H2 molecules, which form the first complete layer around
the fullerene molecule.
Stereoselective fragmentation of nitroimidazoles following UV-photoabsorption
The primary ionizing beams and the secondary particles (electrons, ions, radicals, excited fragments) may provoke significant alterations to biological systems, particularly within living cells and the DNA/RNA molecules. At the molecular level these modifications are mostly related to the bond cleavages of the DNA building components, which before decomposition may be a subject of excitation, ionization and/or isomerization. To determine the most sensitive part of the DNA molecular chains to the photon-induced bond rupture, it is therefore important to explore the possible fragmentation mechanisms of their constituents. In this perspective, investigations of the excitation, relaxation and fragmentation processes of the cyclic hydrocarbons containing oxygen and nitrogen heteroatoms (furan, tetrahydrofuran, isoxazole, and pyrimidine) are of particular relevance, because they are often considered to be simple archetypes of the structure units of the DNA. The results of the photon-induced dissociation of these heterocyclic molecules in the inner-valence photon energy range showed that the general fragmentation mechanism involves initial excitation of these molecules into the superexcited states, which are inner-valence or high-Rydberg excited states, lying at higher energies above the first ionization threshold.
During the STSM we investigated a new class of mechanisms of the photon-induced fragmentation of the heterocyclic molecules, namely ultrafast recapture processes to Rydberg states by detection of the neutral high-Rydberg (HR) fragments after inner-shell C1s, N1s and O1s core excitation and ionization. First, we measured the NEXAFS spectra by recording total ion yields at each inner-shell edge (C1s, N1s and O1s) without field ionization. Then, we switched on field ionization and measured the sum (or total yield) of HR fragments and energetic photons. The differences between both curves (see figure below) demonstrate that core ionization of the molecule with a photon energy just above the 1s ionization potential leads to ultrafast photoelectron recapture processes where the photoelectron is pushed back to HR orbital of the molecular ion. Then, neutral HR fragments can be created together with ions after subsequent dissociation processes. In order to identify particular HR fragments, the TOF spectra were measured at the selected energies using field ionization. For better understanding of the fragmentation processes we also measured the PEPICO spectra (i.e. coincidence spectra without field ionization) at numerous photon energies at the C1s, N1s and O1s edges.
All the results measured during this STSM are being currently analyzed. They will be presented in imminent international conferences and published in high-profile journals as soon as possible. The main goals of this STSM were successfully accomplished and I am grateful to the COST Action CM1204 XLIC for the opportunity to collaborate with the Elettra GasPhase beamline team. This cooperation will be continued during the upcoming years.
Figure shows the example patterns of total ion yield and HR fragments+VUV photons yield recorded in isoxazole at the N1s edge in the photon energy range of 398-416 eV. Both yields are normalized to the photon flux and scaled to have the same intensity at the lowest energy resonance.
The Universidad Autónoma de Madrid (Spain) and the Université de Bordeaux (France) offer a salaried PhD position (36 months) to be carried out under a co-tutelle agreement, starting by September 1st, 2016.
The successful applicant shall develop a research project on “Study of relativistic effect in non-linear interaction between molecules and xuv/soft x-ray short laser pulses”, oriented to obtain a PhD diploma.
We seek for applicants possessing a bachelor degree in Physics or Chemical Physics plus post-graduate education (MSc), and good programming skills.
Further information can be found here: https://www.xchem.uam.es/xchem/?p=2585
Within the ERC Consolidator Grant project COMOTION — CONTROLLING THE MOTION OF COMPLEX MOLECULES AND PARTICLES there are several position openings.
For instance, the following two projects, amongst others, are open and to be filled as soon as possible. Further project descriptions are available at https://www.controlled-molecule-imaging.org/careers/projects
Aerosols into vacuum
This project will develop strategies to optimally transfer large molecules/particles into high-vacuum through nebulization techniques, possibly combined with aerodynamic transport and focusing. Techniques include gas-dynamics-virtual-nozzle thin water jets, electrospray, and other analytical chemistry nebulization techniques, which will be combined with special aerodynamic lenses currently being developed in our group. This includes methodologies to cryogenically cool the produced beams. The resulting (bio)particle beams will be thoroughly characterized (density, distribution, charge-state,…) and applied in fundamental physics and biochemistry/structural biology studies. Subsequently, the experiments will be extended toward the control of these beams (mass selection, isomer separation, angular alignment).
The produced and well-controlled cold samples of large molecules/nanoparticles will be investigated using femtosecond lasers and with x-ray or electron diffraction experiments, using table-top (laboratory) as well as at Free-Electron laser sources.
The successful candidate will have an outstanding Ph.D. in experimental physics, physical chemistry, or a related field. Experience with aerosol technologies, lasers, vacuum equipment, or diffractive imaging is highly desirable.
Aerosol Sci. Technol. 22, 314 (1995)
Struct. Dyn. 2, 041717 (2015)
Opt. Exp., accepted (2016), arxiv:1512.06231 (2015)
Control of aerodynamically focussed beams of very large molecules and nanoparticles
In this project we develop strategies to control the transfer of very large molecules and nanoparticles to the interaction point of modern imaging experiments, in high-vacuum, through the use of cryogenic techniques and optical manipulation. “Shock-freezing” the molecules makes them especially amenable to the control of their internal and external degrees of freedom. External electric and laser fields allow for precise steering of the particles as well as for spatial separation based on physical properties (size, mass, structure). Methodologies to characterize these beams regarding density, distribution, charge-state, etc will be further developed.
The produced and well-controlled cold samples of very large molecules/nanoparticles will be investigated using X-ray or electron diffraction experiments in laboratory experiments, as well as at Free-Electron lasers.
The successful candidate will have an outstanding Ph.D. in experimental physics, physical chemistry, or a related field. Experience with lasers, aerosol technologies, vacuum equipment, or imaging is highly desirable.
Opt. Exp. 21, 30492 (2013)
Phys. Rev. X 2, 031002 (2012)
Int. Rev. Phys. Chem. X 34, 557 (2015)
Phys. Rev. Applied 4, 064001 (2015)
Opt. Expr., accepted (2016), arXiv:1512.06231 (2015)
More information at:
Controlled Molecule Imaging Group – https://www.controlled-molecule-imaging.org
Univ.-Prof. Dr. Jochen Küpper, Center for Free-Electron Laser Science, DESY and Universität Hamburg
open positions – https://www.controlled-molecule-imaging.org/careers
CFEL Molecular Physics Seminar – https://www.molecular-physics.org/news/seminar
ERC COMOTION – https://www.comotion.info
During this Short Term Scientific Mission the UV photoionization of two imidazolic derivatives, 2-nitroimidazole and 4(5)-nitroimidazole (see Fig. 1), were studied. These compounds have been proposed as radiosensitizers and have shown very interesting effects in their fragmentation patterns upon collision induced dissociation and low energy electron attachment,. These studies suggest that even rather small structural changes can alter the fragmentation chemistry significantly thus also affecting the radiosensitizing properties.
We found out that the fragmentation processes induced by valence photoionization depend greatly on the site of the nitro (NO2) group, especially when the six outmost orbitals are ionized. Basically, 2-nitroimidazole seems to be more unstable upon valence ionization compared to 4(5)-nitroimidazole. Furthermore, the imidazole ring always breaks via the same bond cleavages; in 2-nitroimidazole the NO2 at the C2 site blocks the HNCH+ production. As for in 4(5)-nitroimidazole, the NO2 at the C4(5) site blocks the C2H2N+ formation.
Figure 1 Mass spectra of 2-nitroimidazole (top) and 4(5)-nitroimidazole (bottom) following the ionization of the six outmost valence orbitals.
Future collaborations between the Institute for Ion Physics and Applied Physics have been planned during the STSM. Especially experiments concerning clustered (molecular and hydrated) nitroimidazoles were envisioned. A publication concerning this STSM, the photofragmentation of 2-nitroimidazole and 4(5)-nitroimidazole, is currently under preparation and will be finished within a month.
 M.R. Horsman & A.J. van der Kogel. In: Joiner & van der Kogel, Basic Clinical Radiobiology, Hodder Arnold, 2009
 K. Tanzer et al. Angew. Chem. Int. Ed., 2014, 53, 12240-12243
 L. Feketeová et al. Phys. Chem. Chem. Phys., 17, 12598 (2015)