15min:

ZHOU LIN AND ANNE B. MCCOY, Department of Chemistry and Biochemistry, The Ohio State University, Columbus, OH 43210.

Protonated hydrogen dimer, or H₅⁺, is the intermediate of the proton-transfer reaction between H₃⁺ and H₂. The dynamics of this reaction has been postulated to play a significant role in the non-thermal H/D and ortho-/para- ratio in the interstellar clouds. As a weakly-bound, fluxional molecular ion, H₅⁺ has a very rich vibrational spectrum. The large-amplitude vibrational motions of H₅⁺ make theoretical studies interesting but challenging. This work aims at understanding how these large-amplitude motions are reflected in the dynamics of the proton transfer between H₃⁺ and H₂, or between the deuterated analogues of these two species. The shared-proton stretch mode is closely related to the proton-transfer process and is thus of particular interest. Diffusion Monte Carlo calculations of minimum energy paths are performed for the ground state and selected excited states, in order to explore how the vibrational energetics and wavefunctions evolve as H₅⁺ dissociates into H₃⁺ and H₂. The effects of deuteration on the structures and properties are also investigated.