H₃⁺ Formation From Methyl Halogens and Pseudohalogens

The H₃⁺ ion is of critical importance to interstellar chemistry due to its reactivity and ability to protonate other species. This ion is highly abundant in interstellar space and plays a key role in the formation of small molecules which are important for the formation of stars. Due to the relevance of H₃⁺, understanding the nature of its molecular dynamics is critical to gaining insight into astrochemistry. Here, we study H₃⁺ formation from compounds of the form CH₃X, where X = (Cl, I, OH, NCS, SCN) following strong-field double ionization. The nature of the X group affects the CH₃ moiety in different ways, altering the formation timescale and yield of H₃⁺. We find that CH₃I and CH₃SCN generate no appreciable H₃⁺, while the remaining compounds generate H₃⁺ in increasing yield: CH₃NCS, CH₃OH, CH₃Cl. We performed time-resolved strong field measurements and find the timescale of H₃⁺ formation to be 150 fs from CH₃OH, 175 fs from CH₃NCS, and 415 fs from CH₃Cl. High-level computation work is also done to analyze the possible formation mechanisms of H₃⁺ from these systems, and to help elucidate the differences in yield and timescale of H₃⁺ from these different methyl halogens and pseudohalogens.