Events

Upcoming LACUS seminars

Dr. Philip Kurian (Howard University, Washington DC, USA)

Title : Ultrafast tryptophan-to-tryptophan energy transfer and superradiance in tubulin polymers.

Abstract: Oxidative stress from aerobic processes is a pathological hallmark of degenerative disorders such as Alzheimer’s disease and cancer. The precise role of reactive oxygen species (ROS) in the disease process, however, is poorly understood. It is known that the production of ROS by mitochondria can result in ultraweak photon emission (UPE) within cells, and UPEs in the UV and visible ranges have been observed with modern equipment during different stages of the mitotic cycle. Surrounding biomolecules can absorb these photons via aromatic amino acids (e.g., tryptophan and tyrosine), nucleobases (e.g., adenine, cytosine, guanine, thymine), and other chromophoric constituents, forming excited singlet or triplet transition states. One likely absorber is the microtubule cytoskeleton, as it forms a vast network spanning neurons, is highly co-localized with mitochondria, and shows a high density of aromatics, but DNA and the photoactive receptors in the mitochondrial membrane are also potential candidates. These networks may traffic ROS-generated endogenous photon energy for cellular signaling, or they may serve as dissipaters of such energy to protect the cell from potentially harmful effects. Recent modelling efforts based on ambient temperature experiment are presented, showing that such biopolymers can feasibly absorb and channel these photoexcitations via resonance energy transfer, on mesoscopic length scales of physiological significance. Additional simulations using a non-Hermitian Mukamel Hamiltonian demonstrate the possible existence of superradiant states in microtubules corresponding to similar observed phenomena in cylindrical chlorophyll complexes.

Thursday 5 July 2018 / 16:00 / CH G1 495

Poster Lacus day 2018

The event is sponsored by Swissphotonics

Program Lacus day 2018

News

2018

Roberto Monni, Gloria Capano, Gerald Auböck, Harry B. Gray, Antonín Vlcek, Ivano Tavernelli, diplatinum Majed Chergui.

“Vibrational coherence transfer in the ultrafast intersystem crossing of a di-platinum complex in solution.”

 PNAS 25 June 2018. DOI: 10.1073/pnas.1719899115

  • New publication for LSU in PRL, also highlighted on the SB news:LSU

Simon P. Neville, Majed Chergui, Albert Stolow, Michael S. Schuurman.                    “Ultrafast X-ray spectroscopy of conical intersections”

  Physical Review Letters 120, 12 June 2018.

2017

  • Raffaella Buonsanti (LNCE) got an ERC starting grant.
  • Arianna Maciaro (LBP) got an Ambizione Fellowship, SNSF: Understanding Photoinduced Processes at   Semiconductor/Aqueous Interfaces by Surface-Specific Spectroscopic Techniques.
  • Raffaella Buonsanti (LNCE) got a SNSF Assistant Professor Energy grant
  • Highlight article (LNCE): New method improves stability of perovskite quantum dots
  • A new second harmonic microscope capable of 3D imaging of interfacial water and water in pores (LBP).
  • Ulrich Lorez (LND) got an ERC starting grant.
  • The 24th issue of the Laserlab Newsletter “LASERLAB Forum” is published featuring an article by Edoardo Baldini and Majed Chergui (LSU) on the absorption of light by titanium dioxide.
  • Majed Chergui (LSU) is the keynote speaker of the 78th “Sir Jesse Boot Lecture” at the University of Nottingham, where he will talk about “Ultrafast Chemical Dynamics in Solution: Optical and X-ray studies”.
  • LACUS seminar by Prof. Richard Friend (University of Cambridge – UK):

Molecular semiconductors for LEDs and solar cells: designing around the Coulomb interaction”

An ultrashort laser ablation fiber probe shows great potential for microstruring application. Lensless focusing and digital scanning of the focus spot, using wavefront shaping techniques, lead to a submillimeter femtosecond laser ablation tool.

High power laser ablation

Ultrashort pulse ablated samples of thin gold film deposited on glass (a. EPFL letters and b. the Matterhorn).

Skyrmions are nanometric spin whirls that can be stabilized in magnets lacking inversion symmetry. The properties of isolated Skyrmions embedded in a ferromagnetic background have been intensively studied. We show that single Skyrmions and clusters of Skyrmions can also form in the helical phase and investigate theoretically their energetics and dynamics. The helical background provides natural one-dimensional channels along which a Skyrmion can move rapidly. In contrast to Skyrmions in ferromagnets, the Skyrmion-Skyrmion interaction has a strong attractive component and thus Skyrmions tend to form clusters with characteristic shapes. These clusters are directly observed in transmission electron microscopy measurements in thin films of Cu2OSeO3. Topological quantization, high mobility, and the confinement of Skyrmions in channels provided by the helical background may be useful for future spintronics devices.

Skyrmions clusters in Cu2OSeO3

Individual skyrmions and skyrmions clusters in the helical phase of Cu2OSeO3.

Edoardo Baldini, Tania Palmieri, Thomas Rossi, Malte Oppermann,Baldini et al Electron Injection Enrico Pomarico, Gerald Auböck, and Majed Chergui

“Interfacial Electron Injection Probed by a Substrate-Specific Excitonic Signature.”

  • New article of the LUMES group by E. Baldini et al. in Phys. Rev. Lett.:

Real-Time Observation of Phonon-Mediated σπ Interband Scattering in MgB2:

E. Baldini;

Illustration of the ultrafast dynamics of MgB2. After the interaction with the solid, the ultrashort laser pulse leads to the excitation of both sigma and π carriers. The nonthermal sigma carriers are strongly coupled to the branch of the E2g phonon mode and efficiently generate hot phonons during the first 170 fs. Subsequently, the energy stored in the hot phonon subsystem is released to the π carriers via interband scattering and to low-energy phonons via anharmonic decay.The microscopic details of the interplay between the two subsystems in multi band superconductors were lacking to date and represent an important information for the manipulation of superconductivity in these type of materials.

Chimia special issue LACUS

Photo gallery

Why LACUS

Fundamental and practical challenges facing our society can be addressed with new methods and thus approached from a new perspective. Examples of present day challenges are energy conversion, information technology, new materials and biology and medicine.
Over the last decade, ultrafast science and technology have made enormous progress, opening a large variety of new research fields and applications. Examples include table-top high-harmonic generation that allow new forms of spectroscopy and diffraction, lab-based sources of ultrashort electron pulses and sources of terahertz radiation that opened new directions in materials science, chemistry and biology and new sources of ultrashort X-ray pulses, such as X-ray free electron lasers.
The Lausanne Centre for Ultrafast Science (LACUS) brings together the EPFL teams working in Ultrafast Science and Technology with experimental and theoretical methods as well as those using ultrafast technology in different applications. Research areas are very diverse, spanning from fundamental to applied research and they present a very high degree of complementarity. Several EPFL groups are pioneers in ultrafast science and technology and LACUS pools in the expertise in the development and the use of advanced ultrafast laser technology, X-ray and electron technology and associated methods, along with the EPFL theory groups. It also aims at complementing and strengthening existing Swiss scientific infrastructures, e.g. the Swiss Light Source and the SwissFEL.