Masterclasses

Living in the quantum world
Quantum is ubiquitous. That is what we learn in the theory of quantum mechanics, which we will celebrate in its centennial soon. However, we are mostly innocent and unaware of its presence in our daily life. Quantum information science has brought new perspectives through active control and readout of quantum states. In the Masterclass, we will discuss how it is realized in superconducting circuits and other systems.

Looking for Higgs bosons in the ATLAS data
We will use real data collected with the ATLAS detector operating at the Large Hadron Collider (LHC) at CERN to look for events containing Higgs bosons. Higgs bosons are highly unstable particles with a lifetime of about 10-22 sec. So just about as soon as they are produced in proton collisions at the LHC, they decay into other particles, such as for example a pair of Z bosons, which will themselves decay into stable particles like muons or electrons. So we identify the Higgs bosons from their decay products. After a brief introduction to particle physics, the participants will first learn how to identify key particles like electrons and muons in the ATLAS detector. They will then learn how to reconstruct Z bosons from electron and muon pairs. And finally, we will look for events containing two Z bosons, which could have been produced in the decay of a Higgs boson. Students of all levels and without prior knowledge in particle physics can take part in this masterclass. We will work in groups of two using the participants own laptops.

The light stuff: enabling sustainable chemical manufacturing with atomically-architected photocatalysts
Chemical manufacturing is critical for industries spanning construction, plastics, pharmaceuticals, food, and fertilizers, yet remains among the most energy-demanding practices. Optical excitation of plasmons offers a route to more sustainable chemical synthesis. Plasmons create nanoscopic regions of high electromagnetic field intensity that can modify electronic and molecular energy levels, enable access to excited-state dynamics, and open new reaction pathways that are impossible to achieve under typical conditions. Further, plasmons can be efficiently excited with sunlight or solar-driven LEDs, for sustainable chemical transformations.

Here, we present our research advancing plasmon photocatalysis from the atomic to the reactor scale. First, we describe advances in in-situ atomic-scale catalyst characterization, using environmental optically-coupled transmission electron microscopy. With both light and reactive gases introduced into the column of an electron microscope, we can monitor chemical transformations under various illumination conditions, gaseous environments, and at controlled temperatures, correlating three-dimensional atomic-scale catalyst structure with photo-chemical reactivity.  Then, we describe how these atomic-scale insights enable optimized reactor-scale performance. As model systems, we consider acetylene hydrogenation with Ag-Pd catalysts and CO2 reduction with Au-Pd catalysts. Here, Au/Ag acts as a strong plasmonic light absorber while Pd/Ru serves as the catalyst. We find that plasmons modify the rate of distinct reaction steps differently and that reaction nucleation occurs at electromagnetic hot-spots – even when those hot-spots do not occur in the preferred nucleation site. Plasmons also open new reaction pathways that are not observed without illumination, enabling both high-efficiency and selective catalysis with tuned bimetallic catalyst composition. Our results provide a roadmap for how atomically-architected photocatalysts can precisely control molecular interactions for high-efficiency and product-selective chemistry.

The Physics of Lightning and Some Close Relatives: “There Are More Things in Heaven and Earth…”
Over the past 30 years, a wide range of completely unknown phenomena produced by lightning and atmospheric electrical processes have been discovered.  Some of these are visible to the human eye if you are lucky enough to be in the right place at the right time, such as gigantic jets that launch from the tops of thunderstorms to 90 km altitude at the edge of space.  Others are not visible but are just as impressive, such as terrestrial gamma-ray flashes that beam an intense, short burst of >1 MeV high energy photons, electrons, and even positrons upward into space and sometimes down towards the ground.  And the physics of lightning itself is much more complicated than we knew even just 5 years ago. These discoveries all owe thanks to modern optical and radio imaging techniques that have delivered images and movies exquisite space and time resolution.

Steven Cummer will tell the stories of how these phenomena were first documented (almost always through a combination of luck and persistence), and he will show some of the best images, videos, and measurements that we have of each. He will also describe their underlying physics (as best we understand them at present), and highlight some key scientific questions that remain unanswered. He will also describe the different ways that they are measured, including high speed video, instruments on orbiting satellites and the ISS, and radio interferometric imaging (my current favourite).  Together we will also do some simple calculations using straightforward physics to show that it should have been possible to predict all of these phenomena before their discovery, if we had just been clever enough.