Astrochemical investigations with molecular beams and synchrotron radiation

Space Science & Astrobiology Division 
N245 Conference Room 215
Thursday, November 8, 2018 – 3:00PM
Speaker: Musahid Ahmed, Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, USA
Abstract: Single photon ionization with vacuum ultraviolet (VUV) photons is an efficient (and “soft”) method of ionizing fragile molecules, whereby the tunable radiation provides precise threshold ionization imparting little excess internal energy into the molecular ion1. Furthermore, tunable VUV ionization has been shown to be a selective, yet universal technique in elucidating molecule-specific information since it can resolve isomers via ionization energy (IE), absorption cross-sections follow rules which are quantifiable, and all molecules will ionize beyond its IE and hence can be detected in a mass spectrometer. In this talk, I will describe recent results showcasing how tunable synchrotron radiation allows for an understanding of molecular growth processes relevant to astrochemistry. We, in collaboration with Ralf Kaiser (University of Hawaii, Manoa), and Alex Mebel (Florida International University) have performed systematic and extensive studies of two- and three-membered ring polycyclic aromatic hydrocarbons (PAHs) 2 utilizing a high-temperature chemical reactor coupled to synchrotron-based VUV photoionization mass spectrometry. Moving beyond these studies, the critical step in the understanding of the mass-growth processes from simple PAHs to larger particles is to unravel the synthesis of key building blocks as present in two- and three-dimensional precursors to carbonaceous nanoparticles: coronene and corannulene. In this talk, I will describe our recent results on the formation of larger compounds (four-ringed pyrene) generated from the reaction of the anthracenyl radical with acetylene 3, and low-temperature routes to formation of PAH’s in Titan’s atmosphere.
Point of contact:  
lisseth.gavilanmarin@nasa.gov
salma.bejaoui@nasa.gov