08.05.2024

Prof. Eberhard K. U. Gross, The Hebrew University of Jerusalem 

Analysis and control of electron dynamics, and the predictive power of time-dependent density-functional theory

Gedenkkolloquium für Prof. Dr. Reiner M. Dreizler

This lecture is about the motion of electrons on the femto- and atto-second time scale; how it can be monitored, analyzed and, ultimately, controlled with ultra-short laser pulses. Real-time simulations are performed employing the ab-initio approach of time-dependent density functional theory (TDDFT). The mathematical foundation of TDDFT is a Frankfurt invention which evolved naturally from the specific scientific environment of the Dreizler group in the 70s and 80s of the past century. The theory guarantees that the time-dependent density of an interacting many-electron system can be calculated, in principle exactly, from a system of single-particle Schrödinger equations. Using TDDFT, we shall visualize the laser-induced formation and breaking of chemical bonds in real time, and we shall highlight non-steady-state features of the electronic current through nano-scale junctions. In another application, with the goal of pushing magnetic storage processes towards faster and faster time scales, we have predicted that in some magnetic materials, an optically induced spin transfer (OISTR) from one magnetic sub-lattice to another can be triggered by short laser pulses. As an all-optical process, OISTR is temporally limited only by the duration of the laser pulse. OISTR was first predicted by TDDFT calculations and later found experimentally. The OISTR effect marks the birth of “atto-magnetism". It allows for switching times six orders of magnitude faster than present-day magnetic read-write devices.

Local host: Prof. Dr. Carsten Greiner

22.05.2024

Dr. Tanja Heftrich, Goethe-Universität Frankfurt

Nukleosynthese der schweren Elemente

Antrittsvorlesung

Bis auf wenige Ausnahmen verändert sich die Zusammensetzung der äußeren, beobachtbaren Bereiche der Sterne im Laufe der Sternentwicklung nicht. Einblicke in das Innere der Sterne sind deshalb nur zeitverzögert möglich. In sehr späten Phasen verlieren Sterne Material - sei es durch explosive Ereignisse oder infolge von Sternwinden. Dieses Material enthält nun beobachtbare Informationen über die geänderte Häufigkeitsverteilung im sonst verborgenen Inneren der Sterne. Das genaue Verständnis der Reaktionswahrscheinlichkeiten verschiedener Atomkerne unter stellaren Bedinungen erlaubt Rückschlüsse auf die Abläufe im Sterninneren. Moderne kernphysikalische Experimente sind somit der Schlüssel zu einem immer besseren Verständnis der verschiedenen Phasen der Sternentwicklung. In diesem Vortrag folgt nach einer kurzen Einführung in die stellare Nukleosynthese eine Übersicht der Messmethoden zur Bestimmung des Wirkungsquerschnittes unter stellaren Bedingungen.

Local host: Prof. Dr. Camilla Hansen

05.06.2024

Prof. Dr. Reinhard Kienberger, TU München

Attosecond science – from the beginning to measuring electron dynamics in molecules, solids and layered systems

The generation and measurement of single isolated attosecond pulses in the extreme ultraviolet (XUV) at the beginning of this century has recently been awarded with the Nobel Prize in Physics. This talk will give a historic review since the beginning of attosecond science and its impact on the understanding of electronic processes on the attosecond timescale.

A pump/probe technique, “attosecond streaking", was used to investigate electron dynamics on surfaces and layered systems with unprecedented resolution. Photoelectrons generated by laser based attosecond extreme ultraviolet pulses (XUV), are exposed to a dressing electric field from well synchronized few-cycle infrared (IR) laser pulses. The energy shift experienced by the photoelectrons by the dressing field is dependent on the delay between the XUV pulse and the dressing field and makes it possible to measure the respective delay in photoemission between electrons of different type (core electrons vs. conduction band electrons). The information gained in such experiments on tungsten triggered many theoretical activities leading to different explanations on the physical reason of the delay. Attosecond streaking experiments have been performed on different solids, layered structures and liquids, resulting in different delays – also depending on the excitation photon energy. These measurements lead to a stepwise increase of the understanding of different physical effects contributing to the timing of photoemission. In this presentation, an overview on the different physical contributions to attosecond time delays in photoemission will be given. The “absolute" time delay, i.e. the delay between the instant of ionization and the emission of a photoelectron will be discussed and latest measurements will be presented.

Local host: Prof. Dr. Reinhard Dörner

12.06.2024

Prof. Dr. Wei Xiong, University of California San Diego

Shedding Infrared Lights on Molecules: From Molecular Polaritons to Multiplexing Imaging

Mid-Infrared (MIR) light can interact with molecules by selectively exciting molecular vibrational modes. On one hand, MIR can populate molecular species to specific vibrational states to manipulate chemical reactions; on the other hand, IR spectroscopy has long been used as a molecular sensing tool. In this talk, I will discuss recent advancement in my lab concerning both aspects: controlling molecules and molecular imaging.

In the first half of my talk, I will delve into the dynamics of molecular vibrational polaritons – a hybrid quasiparticle between light and matter through strong coupling interactions.1-4 Using two-dimensional infrared (2D IR) spectroscopy, we have unambiguously demonstrated that polaritons can efficiently promote energy transfer within or between molecules, subsequently slowing down competing reaction pathways. This research sheds light on the potential roles of polaritons in modifying chemical energy landscapes and influencing reaction pathways. The second half of my talk will discuss the development of a new IR-based imaging technique - MultiDimensional Widefield Infrared-encoded Spontaneous Emission (MD-WISE) microscopy.5 This technique takes advantages of the IR-visible double resonance interactions, which enable using IR photon to modulate fluorescence imaging. As a result, it allows for the distinction of chromophores with overlapping emission spectra by leveraging mid-infrared pulses to encode spatial and temporal data into photoluminescence images. This method shows promises for multiplexing detection channels in biomedical imaging of complex biological entities. These research results highlight how mid-infrared light-matter interaction serves as a powerful mean for both manipulating molecular dynamics and enhancing imaging capabilities, thereby offering new insights into molecular behaviors and interactions at the nano-scale. The implications of these technologies extend across chemistry and biophysics, promising new avenues for research and application in fields ranging from chemical, materials science to biomedical imaging.

Local host: Prof. Dr. Jens Bredenbeck

19.06.2024

PD Dr. Markus Röllig & Prof. Dr. Horst Schmidt-Böcking, Physikalischer Verein

200 Jahre Physikalischer Verein

Am 24. Oktober 1824 gründeten Frankfurter Bürger den Physikalischen Verein um sich selbst und die Öffentlichkeit über die neuesten Entwicklungen in Physik und Chemie zu informieren. In den darauffolgenden 90 Jahren entwickelte sich der Verein zu einer international anerkannten Forschungs- und Lehrinstitution, die die naturwissenschaftliche Entwicklung der Stadt Frankfurt entscheidend prägte und 1914 mit der Stiftung seiner 8 Institute an die neugegründete Universität den Grundstein legte für den erfolgreichen Start der Fachbereiche Physik und Chemie.

Frankfurter Sternstunden der Quantenphysik 1919-1923

Die Frankfurter Universität kann stolz auf ihre Physikgeschichte nach Ende des 1. Weltkrieges sein. Mit Max von Laue, Otto Stern, Max Born, Alfred Lande und Walther Gerlach wirkten in der Physikfakultät mehrere große Pioniere der Quantenphysik. Von Laue hatte wichtige Beiträge zur Aufklärung der X-Strahlung erbracht und dafür 1915 für das Jahr 1914 den Nobelpreis für Physik erhalten. In den Jahren 1919 bis 1922 wurden in Frankfurt bahnbrechende Entdeckungen gemacht, die entscheidend zur Entwicklung der Quantenmechanik beigetragen haben. Das sind die 1919 von Otto Stern entwickelte Molekularstrahlmethode, für die er den Nobelpreis für Physik des Jahres 1943 erhielt. Im Jahre 1922 lieferte er zusammen mit Walther Gerlach den experimentellen Nachweis der Richtungsquantelung atomarer magnetischer Momente und damit konnten sie auch erstmals die Drehimpulsquantelung in Atomen nachweisen. Max Born zusammen mit Elisabeth Bormann haben 1920 erstmals die freie Weglänge von Atomen in Gasen und die Größe von Molekülen gemessen. Alfred Landé hat 1919 in seiner Habilitationsarbeit erstmals die Drehimpulskopplung als die Grundlage der inneratomaren Elektronendynamik postuliert und den Anomalen Zeeman-Effekt erklärt, indem er halbzahlige Drehimpulse einführte und das inner-atomare gyromagnetische Verhalten (den g- Faktor) empirisch herleitete.

Local host: Prof. Dr. Marc Wagner

26.06.2024

Prof. Dr. Sebastian Becker-Genschow, Universität zu Köln

Niemals krank, rund um die Uhr erreichbar, verfügt über das gesamte Weltwissen - Ist ein KI-Chatbot die bessere (Physik-)Lehrkraft

Der Vortrag behandelt den Einsatz KI-basierter Technologien in Schule im Allgemeinen und dem naturwissenschaftlichen Unterricht im Speziellen. Dabei wird insbesondere aufgezeigt, welche Anwendungen für KI möglich sind bzw. möglich sein werden und wie diese das Lehren und Lernen verändern könnten. Einen Schwerpunkt bildet dabei das generative KI-System ChatGPT. Neben den Potenzialen der Technologie werden aber auch Risiken, die ein schulischer Einsatz mit sich bringt und Implikationen für die Lehrkräftebildung diskutiert.

Local host: Prof. Dr. Thomas Wilhelm

03.07.2024

Dr. Theresa Palm, Süddeutsche Zeitung

The Hypothetical Electric Dipole Moment of Electrons - Why Should I care? Carrying Research into Society with Science Journalism

Odds are, you have been there: At a family function or in a new friend group, someone asks, “So what are you working on?" and the brain-wracking begins, for them and for you. How do you outline what your master's thesis is about or what you're doing your PhD on? Where do you even begin explaining, how much detail do you go into? And how in the world do you manage to avoid the term "Fourier transform"? Generally, there is a great deal of interest in physics; the fascination of understanding the material universe captivates laypeople as well as physicists. But it is challenging to bridge the gap between the day-to-day minutiae of seminars and labs and the bigger lines of research. That's why journalistic platforms are always looking for experts who are enthusiastic about explaining physical topics to a broad audience, who can prioritize and who have a connection to research.

From editorial conferences to spontaneous research trips to Gran Sasso, California and the French Atlantic coast: the working world of journalists is different from university in many ways. What attracted me the most was the idea that I could immerse myself in a different subject every other week – and the hope that more than ten people might read my publications.

In my talk, I will give insights into how I personally got into journalism and the Süddeutsche Zeitung as a physicist. I will outline which career opportunities there are in science journalism in general and what you can expect in the industry. And I'm interested to hear how students and doctoral candidates perceive science journalism, which media outlets are particularly interesting to you, what you miss and what you find intolerable. I'm looking forward to a lively exchange!

Local host: Gleichstellungsrat Physik

10.07.2024

Prof. Dr. Sean Tulin, York University, Canada

Title

Abstract

Local host: Prof. Dr. Laura Sagunski

17.07.2024

Hon.-Prof. Dr. Dorothée Weber-Bruls, Jones Day & Physikalischer Verein

From Laboratory to Courtroom and Science Communication - It's All About Curiosity

Local host: Gleichstellungsrat Physik