Title: Unravelling Molecular Mass Growth Processes to Polycyclic Aromatic Hydrocarbons - From Deep Space to Carbonaceous Nanomaterials
Time: 14:00-16:00, November.27, 2024
Place: F207, School of Mechanical Engineering
Host: ZHOU Zhongyue, Assoc. Professor (Institute of Aerospace Propulsion)

Biography
Ralf I. Kaiser received his Ph.D. in Chemistry from the University of Mü nster and Nuclear Research Center Jü lich (Germany) in 1994 and conducted postdoctoral work at UC Berkeley (Department of Chemistry). During 1997−2000, he performed his Habilitation at the Department of Physics (University Chemnitz, Germany) and Institute of Atomic and Molecular Sciences (Academia Sinica, Taiwan). He joined the Department of Chemistry at the University of Hawai’i in 2002, where he is currently Professor of Physical Chemistry and Director of the W. M. Keck Research Laboratory in Astrochemistry. His research focusses on Reaction Dynamics & Materials in Extreme Environments spanning Astrochemistry & Astrobiology, Combustion & Energy, Material Sciences & Propellants, Reaction Dynamics & Kinetics along with Planetary Sciences. These findings have been published so far in some 610 peer-refereed publications with an overall H-index of 72 and some 20,000 citations. For his research achievements, Ralf I. Kaiser was elected Fellow of the Royal Astronomical Society (UK), the Royal Society of Chemistry (UK), the Institute of Physics (UK), the American Physical Society (APS), the American Asso¬ciation for the Advancement of Science (AAAS), and of the American Chemical Society (ACS).

Abstract

For decades, polycyclic aromatic hydrocarbons (PAHs) – organic molecules carrying fused benzene rings - have been invoked in fundamental molecular mass growth processes leading eventually to carbonaceous nanostructures in the interstellar medium (grains) and in combustion processes (soot). However, the elementary steps involved in low- and high-temperature growth mecha¬nisms of these aromatics have remained essentially elusive until recently. Extracted from gas phase molecular beam studies on the molecular level combined with isomer-selective photo-ionization mass spectrometry and electronic structure calculations, this talk presents a comprehensive mecha¬nistical framework on key elementary reaction mechanisms synthesizing aromatic mo¬lecules in extreme environments. These versatile findings are translated from the interstellar medium to combustion systems and to two- and three-dimensional carbonaceous nanostructures such as graphenes, chiral heli¬cenes, nano bowls, and fullerenes. Facile low-temperature ro¬utes to complex aromatics signify a fundamental shift in the perception that PAHs can be only formed at high-tem¬perature combustion and circum¬stellar conditions on electronic ground state surfaces with novel mechanisms compri¬sing excited state dynamics, submerged barriers, and uncon¬ven¬tional concer¬ted reactions between aromatic radicals to ultimately shed light on the aromatic universe we live in.