Physical Seminar – Leah Dodson (University of Maryland)

1315 Seminar Hall
@ 11:00 am

Title: Fundamental Reaction Kinetics Studies for Low-Temperature Astrochemistry Applications

Bio: Link to Bio


Many of the new molecules discovered in astrophysical objects are totally outlandish by traditional perspectives: long linear unsaturated carbon chains, metals in surprising charge states, and strained ring structures have all challenged chemists to think beyond terrestrial conventions in explaining how these molecules form and react, and where they fit into the overall cycle of planetary and stellar evolution. The challenge to the community is to study this exotic chemistry under the relevant physical conditions—most importantly the low temperatures of space. In this talk, I will describe two orthogonal research projects occurring in our group that are unified by their study of the fundamental physical processes that impact low-temperature (down to 10 K) experiments.

In the first part of my talk, I will describe our efforts to measure reaction rate constants for radiative association reactions, a special class of chemical reactions that is most relevant under the low-temperature, low-pressure conditions of space. In these experiments, gaseous ions are generated in a glow-discharge ion source, mass selected, and trapped in a multipole ion trap. Reaction kinetics are monitored in real time by mass spectrometry. Our plans for incorporating buffer-gas cooling in the ion trap, as well as injection of the buffer-gas-cooled neutral co-reactant will also be discussed.

In the second part of my talk, I will share a second research avenue we are pursuing in investigating photodissociation of methanol by ultraviolet photons, a subject of interest to the astronomy community. This work is carried out at the Advanced Light Source user facility in Berkeley in collaboration with scientists at Sandia National Labs using their Multiplexed Photoionization Mass Spectrometer to directly detect reactants, intermediates, and products in the reaction system. Methanol photodissociation products were measured quantitatively, enabling the determination of absolute photodissociation yields, while also revealing new insights into unique product channels, including the tentative detection of a carbene species.

Host: Prof. Susanna Widicus-Weaver