Strong-field ionization of CH₃Cl: proton migration and association

Abstract

Strong-field ionization of CH3Cl using femtosecond laser pulses, and the subsequent two-body dissociation of CH3Cl2+ along Hn+ (n =1-3) and HCl+ forming pathways, have been experimentally studied in a home-built...

Dynamic Effects on the Ionization-Induced Reactions of Methyl Halides: Quantum Mechanical and Molecular Dynamics Studies

“…A relatively large variation in the energy of three levels indicates that the transition states involving the H−Cl and C−Cl bonds dissociation are sensitive to the description of the electron correlation. The reactions passing through the transition states, TS5 Cl and TS6 Cl , occur as experimentally reported 7,8,26 for the generation of CH 2 + + HCl + because the energies of TS5 Cl and TS6 Cl are lower than the 44.1 kcal/mol of the starting ionized state, 1 Cl . In the molecular dynamics simulations, there were three and one trajectories when the reactions occurred through TS5 Cl and TS6 Cl , respectively.…”

“…The ionization-induced fragmentation of methyl halides is of great interest, because the methyl chloride is present in the stratosphere and interstellar medium and contributes to ozone depletion in the stratosphere. For this reason, numerous experimental and theoretical studies have been intensively conducted, with particular emphasis on the two important processes: (i) ionization − and (ii) subsequent fragmentation reaction, ,,− which together constitute the ionization-induced fragmentation reaction. Many experiments have shown that the doubly ionized methyl chloride yields not only H + and H 2 + but also H 3 + as well as other substances such as HCl + and Cl + .…”

“…However, despite the significant amount of studies that have been conducted, there remains a lack of thorough examination regarding the dynamic process of fragmentation. We therefore focused on the fact that the proportion of H 3 + in the product is relatively small, as previously reported for divalent methanol, , ethane, and methyl chloride, , and anticipated that some dynamic effects would play a role in controlling the product distribution for ionization-induced reactions as well as for the photoreaction. , We performed the molecular dynamics simulations in addition to the quantum mechanical calculations to examine the mechanism from dynamical point of view. We followed the reaction from the vertically ionized state in the ground state (S 0 ), as it is critical to understand the product distribution in the ground state.…”

“…In recent years, molecular behaviors in the presence of an intense laser field have attracted much attention because, even in complex chemical reactions involving cleavage and formation of multiple chemical bonds, H migration can be simultaneously achieved. − It has also been reported that those chemical reactions can be intentionally controlled by laser parameters such as intensity, pulse duration, wavelength, and polarization. − When a molecule is multiply ionized in a strong laser field, a huge amount of internal energy is generated inside the molecule. The activated molecule shows an intricate series of reactions through the transformation of internal energy into atomic motion, especially when a multiply ionized molecule finally collapses in a Coulomb explosion due to the repulsion between the positive charges generated inside of it.…”

“…The formation of H 3 + from methyl chloride cannot be ignored in the interstellar space because H 3 + acts as an initiator of a series of ion–molecule reactions that yield various organic molecules. Therefore, many efforts have been devoted to elucidating the structures and the electronic properties of the ionized methyl chloride and its isomer as an intermediate during the fragmentation reaction using the ab initio electronic structure calculations. ,− Furthermore, researchers have conducted computational studies to elucidate the mechanism behind the H 3 + formation ,, as well as the H + and H 2 + formation and to explore multiple fragmentation pathways leading to various products, including those that involve H-migration. , Recently, the examination has been extended to include the triply ionized CH 3 Cl 3+ in addition to the doubly ionized CH 3 Cl 2+ as a parent ion, and has covered not only ground state but also the excited state of their parent ions …”