UCLA

This thesis details the development of a new platform for the interrogation of ion-molecule chemistry at cryogenic temperatures to experimentally observe reaction rates and branching ratios of fundamental reactions in the interstellar medium. By combining cryogenic buffer gas cooling, laser-cooled ion sympathetic cooling, and integrated mass spectrometry in an RF Paul trap. Cold molecular species produced in a cryogenic buffer gas beam react with trapped Be+ and C+ ions. Since charged reaction products are also trapped, ion imaging and time of flight mass spectrometry are used to study the reaction rates and identify the products.

I first describe the design and calibration of the apparatus from the cryogenic buffer gas beam, to the time of flight mass spectrometer. Then I will discuss the work done towards understanding quantum state resolved Be+ ion chemistry with H2O. We find that when Be+ is in the ground state, a submerged barrier in the reaction entrance channel prevents about half of the incoming trajectories from reaching the nominally exothermic product channel with good agreement between theory and experiment. Next, I will discuss the introduction of HOD to determine if there are similar dynamics involved in preferential bond breaking. Coupled with theory, our experiment does not distinguish between dynamical processes and statistical theory. Finally, I will describe the experimental results in determining the isomer branching ratio in the C+ + H2O reaction at collision temperatures around 10 K, 100 K, as well as 300 K.