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Viewing upcoming talks in: EaStCHEM Colloquia
Speaker: Sebastian Schulz (School of Physics and Astronomy)
Nonlinear effects hold great potential for a wide range of applications - all-optical signal processing, beam shaping and steering, optical computing, sensing, detection and general meteorology, to name a few. However, typically non-linear effects are weak; a typical non-linear index change is on the order of 0.01% or less and therefore they typically require high-power, short-pulse lasers, as well as long interaction length or resonant enhancement. Here, we show that a thin metasurface (50 nm total thickness), consisting of metal antennas on an epsilon-near-zero (ENZ) film, can produce a giant non-linear response with the refractive index change, Δn , exceeding 2 across a broad spectral range in the near-infrared wavelength region.
On: March 26, 2019 From: 13h00 To: 14h00View talk
Speaker: Ian Manners (University of Victoria, British Columbia, Canada and the University of Bristol, UK)
Molecular, and more recently, macromolecular synthesis has evolved to an advanced state allowing the creation of remarkably complex organic molecules and well -defined polymers with typical dimensions from 0.5 nm - 10 nm. In contrast, the ability to prepare materials in the 10 nm – 100 micron size regime with controlled shape, dimensions, and structural hierarchy i s still in its relative infancy and currently remains the virtually exclusive domain of biology. In this talk recent developments concerning a promising “seeded growth” route to well -defined 1D and 2D nano - and microparticles termed “living” crystalliza tion -driven self -assembly (CDSA), will be described. Living CDSA can be regarded as a type of “living supramolecular polymerization” that is analogous to living covalent (e.g. anion initiated) polymerizations of molecular monomers but on a much longer leng th scale (typically, 10 nm – 5 microns). Living CDSA also shows analogies to biological “nucleation -elongation” processes such as amyloid fiber growth . The building blocks or “monomers” used for living CDSA consist of a rapidly expanding range of crystal lizable block copolymers, homopolymers with charged termini, or planar p-stacking molecules with a wide variety of chemistries. The seeds used as “initiators” for living CDSA are usually prepared from preformed polydisperse 1D or 2D micelles by sonication. As a useful alternative, they can be formed in situ in solution by thermal treatment and/or by using conditions of controlled solvency. The “ in situ ” method is termed 1D or 2D “self -seeding” and has its origins in early work on the growth of polymer singl e crystals . Recent results indicate that through combination with the polymerization -induced self - assembly (PISA) method, living CDSA is scalable and therefore offers the potential to prepare uniform samples of 1D and 2D nanoparticles and hierarchical ma terials with potential applications in areas such as optoelectronics, catalysis, and biomedicine. Recent examples of work by our group and our collaborators, and also by other workers in the field, will be discussed . Selected Recent References: Scienc e 2015, 347, 1329; Science 2016 , 352, 697; Nature Chem. , 2017 , 9, 785; Nature Mater. 2017 , 16 , 481; Nature Comm. , 2017 , 8: 15909; ACS Nano 2017 , 11 , 9162; Nature Comm. 2017 , 8: 426. Science 2018 , 360 , 897. Download PDF
On: April 1, 2019 From: 16h00 To: 17h00View talk
Speaker: Leticia Gonzalez (Vienna)
Excited states and ultrafast chemical dynamics on the computer
Leticia González Department of Theoretical Chemistry, University of Vienna, Währinger Strasse 17, 1090 Vienna, Austria,
When molecules are irradiated by light, they are electronically excited, undergoing photophysical and photochemical processes. These processes mean that the molecule will explore different regions of the excited potential energy surfaces, which nowadays can be mapped with different theoretical methods, from the stationary and dynamical point of view. Due to the often pseudo-degeneracy of states and the involvement of potential surfaces of same or different multiplicity that can cross, breaking the Born-Oppenheimer approximation, the calculation of electronic excited states has not yet reached the maturity and accuracy which is golden standard in the electronic ground state. In this lecture, the current efforts of our group on understanding the behaviour of molecules under light irradiation and its dynamics will be reported. Particular emphasis will be made on the recent advancements made using SHARC , our home-made code for the studying ultrafast excited state dynamics.
 S. Mai, P. Marquetand, L. González, Nonadiabatic dynamics: The SHARC approach Wiley Interdiscip. Rev. Comput. Mol. Sci. 8, e1370, (2018) Download PDF
On: April 3, 2019 From: 15h30 To: 16h30View talk
Physics and Astronomy Colloquia
Speaker: Prof. Til Birnstiel (LMU)
Building planets is a dirty business. First of all, planets are made out of the dirt we call interstellar dust. Secondly, the physics involved is not “clean” in a sense that neither the processes involved, nor the initial conditions are known. Solid state physics, radiation transport, gas phase and surface chemistry, magnetic fields and hydrodynamic instabilities at high Reynolds numbers are just some of the aspects that are certainly involved in growing the sub-micrometer sized interstellar dust by 40 orders of magnitude in mass to a full-fledged planet. Given this complexity and dynamic range, it is perhaps not surprising, that the formation processes of planets are still poorly understood, even though thousands of planets beyond our solar system are known today.
Some of the biggest mysteries of planet formation lie in the early stages: growing the asteroid-sized building blocks of planets. Recent years have seen a revolution in observing capabilities delivering data of unprecedented detail and sensitivity. They have partially confirmed our theoretical expectations, partially surprised us. In this lecture, I will discuss some of the basic concepts and the problems we are facing from the theoretical side. I will outline how they might be overcome and will show how recent observational break-throughs revolutionize this exciting field, bringing us closer to solving the puzzle of planet formation.
On: April 5, 2019 From: 10h00 To: 11h00View talk
Physics and Astronomy Colloquia
Speaker: Prof Jane Greaves (Cardiff University )
A very small number of planet-forming discs around young stars host hydrogenated nano-diamonds. These nano-particles were discovered in meteorites on Earth in the 1930s, and their infrared signatures were first found in space environments in 1980. The origins of the particles are obscure, even in the solar system, and most astronomers have been happily oblivious of the whole topic. I will discuss an unexpected outcome of our observations made to track grain growth in these proto-planetary discs, where the only three systems known to host nano-diamonds also showed anomalous microwave emission. This serendipitous result has led to a well-evidenced carrier-particle for this AME (after twenty years of debate), using the well characterised environments of circumstellar discs.
On: April 12, 2019 From: 10h00 To: 11h00View talk