Formation of H$_{3}^{+}$ in methanol : an intramolecular bond rearrangement study

We report here results of TOF multi-hit coincidence experiment [1] that provide evidence for intramolecular reactions involving proton coagulation in methanol [2] after interaction with 1.2 MeV Ar$^{8+}$ projectiles produced from the ECR ion source in the LEIBF laboratory of Inter-University Accelerator Centre, India. Quite remarkably, we have observed the formation of H$_{3}^{+}$ due to movement of protons within the multiply charged parent molecular ion through two-body process (CH$_{3}$OH$^{2+}\to $H$_{3}^{+}$ + COH$^{+})$ and such bond formation occurs before the Coulomb repulsion makes the fragment ions to fly apart. Analysis of the fragmentation pattern of CH$_{3}$OH$^{2+}$ has been carried out using \textit{ab initio} quantum chemical techniques. Structural calculations indicate that the formation of H$_{3}^{+}$ is the preferred pathway in the overall fragmentation dynamics of the ground state of this alcohol. The field generated from highly charged ions induces the system to rearrange its structure following a minimum energy pathway and form hydrogen molecular ions. Repeating the experiment with CH$_{3}$OD confirm our bond rearrangement phenomenon and establish that H$_{3}^{+}$ formation occurs only within the methyl group of the alcohol. Ref: [1] S. De et. al. NIMB, 243, 435 (2006) [2] Sankar De et. al. PRL, 97, 213201 (2006)