THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar:
Reaching 100% efficient OLEDs. Converting triplet excitons into singlet states without spin orbit coupling
Prof. Dr. Andy Monkman
Organic Electroactive Materials Research Group
Department of Physics, Durham University, England
Abstract:
Organic light emitting diodes are now a common place technology, but increasing their internal efficiency to near 100% is difficult. The main reason for this is that on charge recombination, 75% of excited states formed have triplet character and are non emissive. At present iridium containing phosphors are used to harvest these states to produced light, but a new type of emitter has been developed that can also convert triplet to singlet states but without the need for a heavy metal or spin orbit coupling, Thermally Activated Delay Fluorescence; ‘TADF’. In my talk I will describe the mechanisms that drive TADF and show how molecular design and careful energy level tuning give rise to 22% external quantum efficiency deep blue OLEDs. Throughout, new time resolved photophysical measurements will be explained and used to elucidate the physics behind TADF.
Date: 27/April/2016 – (wednesday) – Place: Sala 212 – Auditório do Departamento de Física – Time: 14 horas
THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar:
“Massas de mésons nêutros na presença de campos magnéticos fortes”
Prof. Dr. Sidney dos Santos Avancini
UFSC/FSC
Abstract:
O estudo da matéria na presença de campos magnéticos ultra intensos é hoje em dia um dos tópicos de grande interesse nas áreas de física de partículas e astrofísica. Na superfície de certa clásse de estrelas de nêutrons, denominadas magnetares, são encontrados campos magnéticos da ordem de até 10¹⁵ Gauss e em certas colisões em grandes aceleradores de partículas, como no CERN, acreditá-se que os maiores campos magnéticos do universo, da ordem de 10²⁰ Gauss, possam ser produzidos. Neste seminário vamos descrever como certos tipos de partículas mesônicas nêutras, especificamente o píon e o méson sigma, se comportam na presença de campos magnéticos fortes. A descrição dessas partículas será feita através do modelo efetivo da cromodinâmica quântica conhecido por Nambu-Jona-Lasinio e o formalismo utilizado será o da teoria quântica de campos.
Date: 15/April/2016 – (friday) – Place: Auditório do Departamento de Química – Time: 10h15min
THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar:
STATUS OF THE CHERENKOV TELESCOPE ARRAY PROJECT (CTA)
Prof. Ulisses Barres de Almeida
Centro Brasileiro de Pesquisas Físicas – CBPF/MCT
Abstract:
Gamma-ray astronomy holds a great potential for astrophysics, particle physics, and cosmology. The CTA is an international initiative to build the next generation of ground-based gamma-ray observatories which will represent a factor of 5–10× improvement in the sensitivity of observations in the range 100 GeV–10 TeV, as well as an extension of the observational capabilities down to energies below 100 GeV and beyond 100 TeV. The array will consist of two telescope networks (one in the northern hemisphere and another in the south) so to achieve a full-sky coverage, and will be composed by a hybrid system of 4 different telescope types. It will operate as an observatory, granting open access to the community through calls for submission of proposals competing for observation time. The CTA will give us access to the non-thermal and high-energy universe at an unprecedented level, and will be one of the main instruments for high-energy astrophysics and astroparticle physics of the next 30 years. CTA has now entered its prototyping phase with the first, stand-alone instruments being built. Brazil is an active member of the CTA consortium, and the project is represented in Latin America also by Argentina, Mexico, and Chile. This year, the consortium has defined the sites for installation of CTA in the South and Northern hemispheres which will be hosted near Cerro Paranal in the Chilean Andes, and in the Canary Island of La Palma, respectively. The installation of CTA in Chile holds great potential for scientific and industrial as well as operational participation for Brazil and other South American countries. The first CTA telescopes should be installed on site during the next couple of years and the full CTA array is expected to be operational by 2022.
Date: 01/April/2016 – (friday) – Place: Sala 212 – Auditório do Departamento de Física – Time: 10h15min
THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar:
Nature’s Extreme Accelerators
Felix Aharonian – Dublin Institute for Advanced Studies
Abstract:
Exploring the Nonthermal Universe with High Energy Gamma Rays
Cosmic gamma rays carry key information about high energy phenomena in a variety of astrophysical environments. Being a part of modern astrophysics and astroparticle physics, gamma-ray astronomy is a discipline in its own right. It addresses an impressively broad range of topics related to the nonthermal Universe – acceleration, propagation, and radiation of relativistic particles on all astronomical scales: from compact objects like
pulsars (neutron stars) and microquasars (accreting black holes) to giant radiogalaxies and galaxy clusters. I will briefly describe the status and discuss the objectives of the field with an emphasis on three major topics: Origin of Cosmic Rays, Physics and Astrophysics of relativistic outflows, and cosmological issues related to the intergalactic radiation and magnetic fields
Date: 11/March/2016 – (wednesday) – Place: Auditório (LAED) do Departamento de Matemática, andar térreo – Time: 10 horas
