THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar:
Detailed chrono-chemo-dynamics of seven metal-poor red giants from Kepler
Arthur Alencastro Puls
Research School of Astronomy and Astrophysics, Australian National University
Abstract:
The Kepler mission has yielded a revolution in the field of GalacticArchaeology, with its photometry allowing the determination of stellar parameters with an unprecedented level of precision for Red Giant stars. Recent studies have shown that a few of these objects display conflicting characteristics in the age-metallicity space (e.g., young and metal-poor). In this project we combine asteroseismic information from solar-like oscillations, high-resolution spectroscopy and Gaia astrometry to derive stellar ages, chemical abundances and kinematics for a group of metal-poor Red Giants, and characterise them in a multidimensional chrono-chemo-dynamical space. Our results suggest that underestimated parallax errors make the effect of Gaia parallaxes more important than different choices of model grid or – in the case of stars ascending the RGB – mass-loss prescription. Two stars are identified as potentially evolved halo blue stragglers. Four objects are likely members of the accreted Milky Way halo, and their possible relationship with known accretion events, such as Gaia-Sausage and Gaia-Sequoia, is discussed.
Date: November 26, 2021 – (friday) – Time: 10:15 a.m.
link to access the youtube channel: https://youtu.be/D1pIcDUoHds
THE PHYSICS GRADUATE PROGRAM invites everyone to the seminar:
Chemistry in optical microcavities: Spectral fluctuations and energy transport
Prof. Dr. Raphael Ribeiro
Department of Chemistry, Emory University – Atlanta, USA
Abstract:
Optical cavities and metallic nanoparticles confine electromagnetic fields and enable new pathways to control physicochemical processes via strong light-matter interactions. In fact, recent experiments have shown that photonic and plasmonic materials may induce significant and sometimes unexpected changes to physical properties and reactivity of molecular systems. In this talk, I will introduce and present the key results of our recent theoretical investigations on the effects of collective radiation-matter interactions on transport and spectral properties of disordered molecular ensembles hosted by a resonant 1D optical cavity (photonic wire). The main implications of our findings to future theoretical and experimental research will be discussed. I will show that widely employed minimal theoretical models fail to adequately describe photonic effects on the local properties of chemical systems and explain strategies to maximize the influence of optical cavities on molecular materials informed by our simulations.
Date: November 19, 2021 – (friday) – Time: 10:15 a.m.
link to access the youtube channel: https://youtu.be/8nV3QDFmhB8
THE PHYSCIS GRADUATE PROGRAM invites everyone to the seminar:
What Hampers Electron Transport in Organic Crystals? A Close Look at Band-like Transport in N-type Organic Semiconductors
Prof. Dr. Emanuele Orgiu
Institut National de la Recherche Scientifique – INRS, Québec – Canada
Abstract:
Charge transport in organic semiconductors is notoriously sensitive to the presence of disorder, both intrinsic and extrinsic, especially for n-type materials. Intrinsic dynamic disorder stems from large thermal fluctuations both in intermolecular transfer integrals and (molecular) site energies in weakly interacting van der Waals solids and sources transient localization of the charge carriers. The molecular vibrations that drive transient localization typically operate at low-frequency (< a-few-hundred cm-1), which makes it difficult to assess them experimentally. Hitherto, this has prevented the identification of clear molecular design rules to control and reduce dynamic disorder. In addition, the disorder can also be extrinsic, being controlled by the chemical and physical “coupling” of the π-conjugated core to the gate dielectric. During the Colloquium, I will present a comprehensive study of charge transport in two closely related n-type molecular organic semiconductors using a combination of temperature-dependent inelastic neutron scattering and photoelectron spectroscopy corroborated by electrical measurements, theory and simulations. By doing so, unambiguous evidence is provided that ad hoc molecular design enables to free the electron charge carriers from both intrinsic and extrinsic disorder to ultimately reach band-like electron transport.
Date: November 12, 2021 – (friday) – Time: 10:15 a.m.
link to access the youtube channel: https://youtu.be/TE3LD1NKi4c
