Tuesday 5 pm (Freiburg) / 8 am (Vancouver)
18.10.2022 – Jennifer Meyer, TU Kaiserslautern
25.10.2022 – cancelled
08.11.2022 – Patrick Rupprecht, MPI für Kernphysik Heidelberg
15.11.2022 – Volker Karle, ISTA Austria
22.11.2022 – Graziano Amati, University of Freiburg
29.11.2022 – Francisco Gonzalez Montoya, University of Leeds, UK
06.-08.12.2022 – Albert Stolow, University of Ottawa & National Research Council Canada
13.12.2022 – Donatas Zigmantas, Lund University, Sweden
20.12.2022 – Oriol Vendrell, University of Heidelberg
10.01.2023 – Abolfazl Bayat, Chengdu University, China
17.01.2023 – Nina Morgner, University of Frankfurt
24.01.2023 – Serguei Patchkovskii, Max Born Institute Berlin
31.01.2023 – Brendan Wouterlood, University of Freiburg
07.02.2023 – Zdenek Masin, Charles University Prague, Czechia
07.02.2023 – Zdenek Masin, Charles University Prague, Czechia
Electronic coupling delay and the dipole laser-coupling delay in RABBITT
Time-delays appeared in quantum mechanics first as a theoretical concept introduced by Wigner and Smith [1] in the course of their study of scattering of wave packets. However, a direct measurement of time-delays in scattering has not been achieved in practice. Instead, time-delays have proved to be measurable in ultrafast photoionization experiments such as RABBITT and attosecond streaking. RABBITT relies on two-photon above-threshold ionization which leads to two types of delay: the intrinsic (field-free) atomic/molecular Wigner-Smith delay and the Coulomb-laser coupling delay. The second one is the result of absorption of the second photon by the liberated electron.
I will describe how we have unraveled two new contributions to RABBITT delays by performing accurate calculations of two-photon matrix elements and their subsequent analysis for various molecules. The new contributions are the laser-induced ionic coupling delay [2] and the dipole laser-induced delay in strongly polar molecules [3]. These delays open new opportunities for probing laser-induced electron-electron and electron-nuclear correlation and molecular polarization. Finally, the separation of the total two-photon time delay into its components is only an approximation which we can rigorously test using our newly developed multi-photon R-matrix theory [4]. Failure of the factorization of the time-delay into its components also carries a valuable information about the laser-induced dynamics in the system.
[1] F. T. Smith, Phys. Rev. 118, 349 (1960).
[2] J. Benda and Z. Mašín and J. D. Gorfinkiel, Phys. Rev. A 105, 053101 (2022).
[3] J. Benda and Z. Mašín, arXiv:2209.06676 [physics] (2022).
[4] J. Benda and Z. Mašín, Sci Rep 11, 11686 (2021).
Chair: Giuseppe Sansone
31.01.2023 – Brendan Wouterlood, University of Freiburg
Time-Resolved Photoelectron and Photoion Spectroscopy of Isolated Organic Molecules and their Clusters
I will briefly present the design and characterisation of a new glass-based molecular beam source for the generation of dense molecular beams of low vapour pressure organic molecules, which was part of my master thesis. In a second part of my talk, I will present the outline of my PhD project, including an introduction to the current experimental apparatus, its capabilities and limitations, which motivate planned upgrades. One major upgrade will be the implementation of photoelectron-photoion coincidence detection for cluster-size resolved pump-probe spectroscopy of clusters of organic molecules, and the development of 200nm UV beam line for efficient photoemission from doped helium nanodroplets.
Chair: Frank Stienkemeier
24.01.2023 – Serguei Patchkovskii, Max Born Institute Berlin
Electron–nuclear correlations in attosecond and strong-field dynamics
On the timescale of interest to attosecond and strong-field science, electronic dynamics reign supreme. The heavier nuclei barely have time to move – and yet, electrons and nuclei remain correlated. I will look at two, limiting-case examples of such correlations: electronic-hole dynamics induced by broad-band, one-photon ionization; and centre-of-mass motion triggered by strong-field electronic excitation. For the hole dynamics, the minute nuclear displacements can cause the reduced electronic coherence to vanish after a few femtoseconds, effectively suppressing electronic dynamics on the longer time scales. In the other limiting case, the weak coupling of electronic dynamics to the centre-of-mass motion provides a sensitive, yet non-destructive probe of strong-field processes.
Chair: Giuseppe Sansone
17.01.2023 – Dr. Nina Morgner, University of Frankfurt
Biomolecular complexes: required and unwanted assemblies – what can we learn with native mass spectrometry
Assembly processes play an important role in the cellular environment. Large macromolecular complexes such as the ATPase from the respiratory chain, need to self-assemble into the correct complex structure in order to be fully functional. Opposed to these well guided processes there are assembly processes, which lead to less wanted structures, such as Amyloid-ß fibrils, which are correlated to Alzheimer’s disease.
We investigate such processes by means of native mass spectrometry and ion mobility. We can reveal underlying mechanisms for the above mentioned processes, including environmental conditions which are prerequisite for assembly of the ATPase into a functional complex1, or the weak point in the Amyloid-ß assembly2, which allows to disrupt this process.
[1] Khanh Vu Huu, Rene Zangl, Jan Hoffmann et al. Bacterial F-type ATP synthases follow a well-choreographed assembly pathway
NATURE COMMUNICATIONS | (2022)13:1218 |
https://doi.org/10.1038/s41467-022-28828-1[2] Tobias Lieblein*, Rene Zangl*, Janosch Martin, Jan Hoffmann, Marie J Hutchison, Tina Stark, Elke Stirnal, Thomas Schrader, Harald Schwalbe, Nina Morgner, Structural rearrangement of amyloid-β upon inhibitor binding suppresses formation of Alzheimer disease related oligomers
eLife 2020;9:e59306 https://doi.org/10.7554/eLife.59306Chair: Bernd von Issendorff
10.01.2023 – Abolfazl Bayat, University of Electronic Science and Technology of China
Quantum many-body probes
Abstract: Ground state criticality of many-body systems is a resource for quantum enhanced sensing, namely Heisenberg precision limit, provided that one has access to the whole system. Indeed, for partially accessible probes the sensing capacity in the ground state reduces to the sub-Heisenberg limit. To compensate for this, we drive the system periodically and use the local steady state for quantum sensing. Remarkably, the steady state sensing shows a significant enhancement in its precision in comparison with the ground state and even shows super-Heisenberg scaling for a certain range of frequencies. The same setup can also be used for sensing AC fields. The precision in partially accessible systems may also be compensated through a sequence of measurements which are performed after a period of free evolution. We show that as the length of measurement sequence increases the precision surpasses the standard limit and asymptotically reaches Heisenberg scaling.
While most many-body quantum sensors achieve enhanced sensitivity within a very narrow region, known as local sensing, one may need a probe to measure an unknown parameter over a large interval. To address this issue, we formulate the notion of global sensing and establish a systematic method to optimize quantum many-body probes to achieve the best possible precision when the parameters of interest vary over arbitrarily large intervals.
References:
[1] V. Montenegro, U. Mishra, A. Bayat, Phys. Rev. Lett. 126, 200501 (2021)
[2] U. Mishra, A. Bayat, Phys. Rev. Lett. 127, 080504 (2021)
[3] V. Montenegro, G. S. Jones, S. Bose, A. Bayat, Phys. Rev. Lett. 129, 120503 (2022)
Chair: Amir Mohammadi (AG Schaetz)
20.12.2022 – Oriol Vendrell, University of Heidelberg
Polaritonic chemistry: manipulating molecular processes with confined light
Polaritonic Chemistry has emerged in recent years as a quickly evolving field where new and exciting experimental and theoretical results appear in rapid succession. At its core is the aim of modifying, and ultimately controlling chemical reactivity with confined electromagnetic radiation instead of the usual approach with optical or infrared lasers (1).
In this talk, I will introduce the key concepts behind this new paradigm and will describe the main challenges and open questions. These will be illustrated with recent theoretical results from our group covering both excited-state, non-adiabatic chemical processes (2,3,5), as well as ground-state, thermally activated chemistry (4).
(1) Thomas, A.; Lethuillier-Karl, L.; Nagarajan, K.; Vergauwe, R. M. A.; George, J.; Chervy, T.; Shalabney, A.; Devaux, E.; Genet, C.; Moran, J.; Ebbesen, T. W. Tilting a Ground-State Reactivity Landscape by Vibrational Strong Coupling.
Science 2019, 363 (6427), 615–619.
https://doi.org/10.1126/science.aau7742.(2) Ulusoy, I. S.; Gomez, J. A.; Vendrell, O. Modifying the Nonradiative Decay Dynamics through Conical Intersections via Collective Coupling to a Cavity Mode.
J. Phys. Chem. A 2019, 123 (41), 8832–8844.
https://doi.org/10.1021/acs.jpca.9b07404.(3) Ulusoy, I. S.; Vendrell, O. Dynamics and Spectroscopy of Molecular Ensembles in a Lossy Microcavity. J. Chem. Phys. 2020, 153 (4), 044108.
https://doi.org/10.1063/5.0011556.(4) Sun, J.; Vendrell, O. Suppression and Enhancement of Thermal Chemical Rates in a Cavity.
J. Phys. Chem. Lett. 2022, 13, 4441-4446.
https://doi.org/10.1021/acs.jpclett.2c00974(5) Nandipati, K; Vendrell, O. Cavity Jahn-Teller Polaritons in Molecules.
https://arxiv.org/abs/2210.16037Chair: Michael Thoss
13.12.2022 – Donatas Zigmantas, Lund University, Sweden
Studying charge carrier dynamics with time-resolved photoemission electron microscopy
There is a need to understand photo-excited charge carrier dynamics in semiconductor and other materials, which are used for making photoactive devices. One example of relevance can be found in the new generation photovoltaic devices employing hot charge carriers, which could beat the solar cell efficiency (Shockley–Queisser) limit. At the same time, it is important to study dynamic processes at the spatial scale that is relevant to the functions of the materials, which is usually nm-mm scale, because of their morphology. To achieve these goals, we use time-resolved photoemission electron microscopy (TR-PEEM), which at simultaneously provides femtosecond time resolution and tens of nanometers spatial resolution. We used this method to study hot carrier dynamics in individual InAs nanowires. Recently we expanded the technique to include a couple of additional modalities: excitation frequency resolution and transient grating excitation. Whereas the former allows for targeted investigation of hot charge carriers and surface defects such as intraband traps, the latter enables studies of charge carrier diffusion and therefore mobility in nanomaterials, as demonstrated in the experiments on InP nanoplatelets.
Chair: Lukas Bruder
06.-08.12.2022 – Albert Stolow, University of Ottawa & National Research Council Canada
Tuesday, December 6, 17:00h
[1] Ultrafast Non-adiabatic Molecular DynamicsWednesday, December 7, 12:00h
[2] Polyatomic Molecules in Strong Laser FieldsThursday, December 8, 14:00h
[3] Non-perturbative Quantum Control of Molecular DynamicsChair: Lucas Bruder
Please find more information here
29.11.2022 – Francisco Gonzalez Montoya, University of Leeds, UK
The calculation of long term dynamics of a spin chain using coherent states
The time dependent variational principle and the coherent states has been successfully used to calculate the evolution of quantum systems with classical analog. Based on this approach, we explore the possibility to calculate the long term dynamics of an experimental time dependent spin chain.
Chair: Andreas Buchleitner
22.11.2022 – Graziano Amati, University of Freiburg
Quasiclassical approaches to nonadiabatic dynamics
In this talk I will discuss quasiclassical techniques aimed at accurately predicting quantum nonadiabatic dynamics at long time with a favorable classical scaling with time and system size. In particular, I will introduce spin mapping, a recently developed quasiclassical approach suited to study a large class of nonadiabatic systems out-of-equilibrium. Spin mapping, although substantially more accurate than Ehrenfest mean-field dynamics, can suffer from low accuracy in the long-time dynamics of strongly asymmetric systems. I will show how such limitation can be overcome by coupling the method to the formalism of the generalized quantum master equation. On the other side, the same strategy applied to Ehrenfest dynamics does not result in meaningful improvements in accuracy. In the second part of the talk I will introduce ellipsoid mapping, a method that we recently developed by generalizing spin mapping to study nonadiabatic systems in thermal equilibrium. The approach fulfills detailed balance by construction; in particular, the method is time reversible, and it guarantees the correct long-time relaxation of thermal correlation functions.
References:
– G. Amati, M. A. C. Saller, A. Kelly, J. O. Richardson,
https://arxiv.org/abs/2209.01076 (2022)
– J. E. Runeson, J. R. Mannouch, G. Amati, M. R. Fiechter, J. O.
Richardson, Chimia 76 582–588 (2022)
Chair: Tanja Schilling
15.11.2022 – Volker Karle, Institute of Science and Technology Austria
Multiband topological phases of periodically kicked molecules
In this talk will show that the simplest of existing molecules – closed-shell diatomics not interacting with one another – host topologically nontrivial phases when driven by periodic far-off-resonant laser pulses. A periodically kicked molecular rotor can be mapped onto a “crystalline“ lattice in angular momentum space. This allows to define quasimomenta and the band structure in the Floquet representation, by analogy with the Bloch waves of solid-state physics. Applying laser pulses spaced by 1/3 of the molecular rotational period creates a lattice with three atoms per unit cell with staggered hopping, whose band structure features Dirac cones. These Dirac cones, topologically protected by reflection and time-reversal symmetry, are reminiscent of (although not equivalent to) the ones seen in graphene. They – and the corresponding edge states – are broadly tunable by adjusting the laser intensities and can be observed in present-day experiments by measuring molecular alignment and populations of rotational levels. This paves the way to study controllable topological physics in gas-phase experiments with small molecules as well as to classify dynamical molecular states by their topological invariants.
Chair: Andreas Buchleitner
08.11.2022 – Patrick Rupprecht, MPI für Kernphysik Heidelberg
From femtoseconds to femtometers – controlling quantum dynamics in molecules using core-level transient absorption spectroscopy
Core-level absorption spectroscopy has proven to be a valuable tool to gain a deeper understanding of quantum dynamics in atoms, molecules and solid-state materials on the femtosecond time scale. Especially the capability of x-ray transient absorption spectroscopy (XTAS) to elucidate dynamics in neutral and thus chemically highly relevant molecules stands out.
In this talk I will present a novel few-cycle laser source and transient absorption setup at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. In addition, first results of purely electronic as well as structural control within molecules using intense femtosecond laser pulses are discussed.
The performed XTAS experiments are enabled by a laser source providing center-wavelength tunable few-cycle pulses in the 1-2 µm short-wavelength infrared (SWIR) regime. These pulses drive high-order harmonic generation (HHG) resulting in measured soft x-ray (SXR) spectra up to 200 eV photon energy. In the first presented experiment, the quantum-mechanical part of the electron-electron interaction, the exchange interaction, is controlled by perturbing gaseous SF6 molecules with SWIR pulses of variable intensity (≤2.2×1014 W/cm2) [1]. A simultaneous HHG probe of the sulfur L2,3 absorption edge reveals a change in the relative oscillator strengths within a spin-orbit-split doublet resonance. We trace this branching-ratio [2,3] alteration back to an exchange-energy increase of up to 50% by employing a theoretical toy-model. These findings are further supported by an ab-initio quantum many-body calculation based on the QUANTY code [4]. In a second experiment, time-resolved x-ray absorption spectroscopy is used to elucidate vibrational molecular dynamics in the perturbative limit. Here, the SWIR pulse precedes the SXR and induces molecular vibrations via nonresonant impulsive stimulated Raman excitation. XTAS can trace vibrational dynamics as imprinted in the resonance-energy shift due to the different involved potential energy curves [5]. In our experiment, we were capable of inducing and measuring the fundamental vibrational breathing mode (period of T = 43 fs) within an ensemble of SF6 molecules with an amplitude of only 50 fm and an unprecedented precision of 14 fm [6]. With the help of a combined quantum many-body and classical simulation, the electronic signature in temporal overlap can be disentangled from the vibrational one and electronic-vibrational coupling dynamics are analyzed.
These XTAS studies pave the way for new ultrafast chemical control schemes as well as molecular vibrational precision metrology.[1] Rupprecht, et al. Laser control of electronic exchange interaction within a molecule. Phys. Rev. Lett. 128, 153001 (2022).
[2] Onodera, Toyozawa. Excitons in alkali halides. J. Phys. Soc. Jpn. 22, 833 (1967).
[3] Thole, van der Laan. Branching ratio in x-ray absorption spectroscopy. Phys. Rev. B 38, 3158 (1988).
[4] M.W. Haverkort, et al. Multiplet ligand-field theory using Wannier orbitals, Phys. Rev. B 85, 165113 (2012).
[5] Hosler, Leone. Characterization of vibrational wave packets by core-level high-harmonic transient absorption spectroscopy. Phys. Rev. A 88, 023420 (2013).
[6] Rupprecht, et al. Resolving vibrations in a polyatomic molecule with femtometer precision. arXiv 2207.01290 (2022).Chair: Andreas Buchleitner
18.10.2022 – Jennifer Meyer, TU Kaiserslautern
Reactive scattering of ion molecule reactions for disentangling chemical reactivity
Reaction dynamics open a window into the fundamental process of a elementary reactions, namely the reactive collision. Understanding chemistry at this level will help us to derive detailed structure reactivity relations with the final aim at controlling chemical reactivity in a bottom up approach. We use gas phase methods to study the intrinsic atomistic dynamics of chemical reactions, i.e. how atoms rearrange during the chemical reaction. Our experimental approach uses a combination of crossed beams with 3D velocity map imaging to record energy and angle differential cross sections of ion molecule reactions [1].Here, I will present two studies on reactions, each with its individual challenges. The first reaction studies the reaction between F– and CH3CH2Cl. One of the most studied competition in physical organic chemistry is the one between bimolecular nucleophlic substitution SN2 and elimination E2 due to the importance of both mechanisms in chemical synthesis. The challenge of disentangling these reaction pathways lies in the fact, that the same ionic product is formed which requires methods beyond standard mass spectrometry [2]. The second reaction involves transition metal ions, which due their complex electronic structure are a challenge to experiment and theory alike. I will present first results from our new 3D crossed beam velocity map imaging experiment at Kaiserslautern on the oxygen atom transfer (OAT) reaction Ta+ + CO2 ® TaO+ + CO. The OAT reaction between Ta+ and CO2 is exothermic but spin forbidden in the electronic ground state but spin allowed for the first electronically excited state. Yet, the reaction was found to almost proceed with collision rate at room temperature [3]. This requires the reaction to efficiently cross from the quintet surface over to the triplet surface. Our aim is to identify dynamic signatures related to effects from individual electronic states in either reactants or products.
[1] J. Meyer, R. Wester, Annu. Rev. Phys. Chem. 2017, 68, 333;
[2] J. Meyer, V. Tatji, E. Carrascosa, T. Gyori, M. Stei, T. Michaelsen, B. Bastian, G. Czakó, R. Wester, Nat. Chem. 2021, 13, 977;
[3] G. K. Koyanagi, D. K. Bohme, J. Phys. Chem. A 2006, 110, 1232;https://www.chemie.uni-kl.de/meyer/seite
Chair: Tobias Sixt
