On the first Tuesday of each month, the InterCat Center hosts an online webinar, with an invited speaker. We encourage interested colleageus to join our webinar to learn more about the center and to meet the center members.
If you would like to be informed about upcoming webinars you should subscribe to the InterCat mailing list. In the meantime, you can browse the list of publically available webinars below.
Andrew Cassidy, Aarhus University
The condensation of dipolar, molecular species to form thin films, can lead to the spontaneous orientation of dipoles in the resulting solid. This phenomenon is long range and homogenous, producing polarized films of nanometer thicknesses that habour internal electric fields of up to 107 V/m. Simple molecular species have been used to demonstrate this phenomenon, including nitrous oxide, carbon monoxide, methyl formate and, most recently, ammonia. The spontaneous generation of the electric field upon growth has been termed the “Spontelectric Effect” and a mean field model has been developed to explain the temperature dependent variation of the strength of the electric fields produced.
Molecular films find technical applications as semi-conductors and pharmaceutical products, and represent the largest source of solid molecular ice in the Interstellar Medium. The spontelectric effect can have impact on all of these areas. In this seminar, I will introduce the experiments that led to the identification and characterisation of the spontelectric effect, namely the measurement of polarization charge on film surfaces and Stark effects in reflection absorption infrared spectroscopy measurements. I will then show how these internal electric fields can be used to understand the physics of Wannier-Mott excitons in ammonia ices and carbon monoxide ices, and introduce a potential role for polarized carbon monoxide ices in astrochemical-reactions.
Stefan T. Bromley (Universitat de Barcelona, Spain)
José Angel Martín-Gago (Institute of Material Science of Madrid, Spain)
Mie Andersen (AIAS and InterCat, Aarhus University, Denmark)
Cornelia Jäger (Max Planck Institute for Astronomy and Friedrich Schiller University Jena, Germany)
Melissa McClure (Leiden Observatory, Leiden University, The Netherlands)
Planets form at the midplane of the protoplanetary disks surrounding newborn stars. The habitability of a planet is determined in part by the relative amounts of CHON elements at the planet's surface, and these CHONs are most likely delivered through incorporation or delivery of astronomical ices during planet formation. These ices originate in cold, dense molecular cloud cores and chemically evolve as the cores collapse to form protostars surrounded by protoplanetary disks. To understand the relative amounts and degree of complexity of the ices incorporated into comets and planets, we need observational constraints on both the chemical evolution of ices from where they form in clouds to the locations in disks where planets are being formed.
In the first part of the talk, I will describe a cutting-edge Early Release Science (ERS) program, Ice Age (P.I. McClure, over 50 team members world wide) with the upcoming James Webb Space Telescope (JWST) to measure the chemical evolution of ices entering disks. This ERS program will provide the star and planet formation and astrochemistry communities with a non-proprietary dataset of JWST spectra, laboratory data, and chemical models within the 5 months of JWST's science operations. With this dataset, and other GTO JWST programs, we will be able to confirm the amount and complexity of ice formed non-energetically within molecular clouds and test the degree to which energetic processing increases its complexity prior to its incorporation into the disk. These programs will also be able to determine the radial distribution of ices in these disks. Time permitting, in the last part of the talk I will demonstrate a new method for identifying specific locations where ices are "left behind" in protoplanetary disks (McClure 2019; McClure, Dominik, and Kama 2020), possibly by formation of planetesimals. By combining these direct JWST studies of the icy dust input into protoplanetary disks with the direct measurement of material moving out of the disk onto the central star, we can map out where icy material is being retained in a given disk, which is a first, critical step to forming planets.
Sergio Ioppolo (Queen Mary University of London, United Kingdom)
An international team of laboratory astrophysicists, in part active within INTERCAT, have shown that glycine, the simplest amino acid and an important building block of life, can form under the harsh conditions that govern chemistry in space. The results, recently published in Nature Astronomy, show that glycine and very likely other amino acids are formed in dense interstellar clouds, well before these transform into new stars and planets.
Jose Angel Martin-Gago (Institute of Material Science of Madrid, Spain)
Frederik Doktor Skødt Simonsen (IFA, Aarhus University)
Zeyuan Tang (IFA, Aarhus University)
The fragmentation of polycyclic aromatic hydrocarbons (PAHs) is important for understanding the survivability of PAHs under harsh interstellar environment and the formation of small molecules like H2, C2H2, C2H4. It is a challenge for current computational technology to explain the complex rearrangements of chemical bonds during the fragmentation in a comprehensive manner. This work combines molecular dynamics (MD) and density functional theory (DFT) to investigate the fragmentation of PAHs and propose a possible route for ethylene (C2H4) formation caused by fragmentation. MD simulations have successfully revealed the fragmentation pattern of two hydrogenated pyrenes and confirmed the structure of fragments. We have found that the edge of PAHs having three connected hydrogenated carbon atoms is the active site for ethylene formation. A more general rule for ethylene formation is introduced based on DFT calculations of other PAHs with similar edge structures.
Alec Wodtke, (Göttingen Univ. and Max Planck Inst. Biophys. Chem., Germany)