Dynamics of proton migration and dissociation in core-excited ethyne probed by multiple ion momentum imaging

Abstract

The study focuses on the rapid geometry change in ethyne excited near the carbon 1s edge. Core excitation and ionization lead to population of dicationic states in ethyne. We study three competing dissociation pathways associated with deprotonation in the linear ethyne molecule, and two cases of rapid proton migration. We investigate the alignment of the molecule in the excited state and find startling differences in these three cases. We present evidence for a strong anisotropy in the production of H2+/C2+ fragments through a rapid deformation of the molecule to a dibridged conformation with the transition dipole moment parallel to the polarization of the exciting radiation.

Role of the Renner-Teller effect after core hole excitation in the dissociation dynamics of carbon dioxide dication

“…A fragmentation channel indicating a dibridged configuration was identified in acetylene. 35 This channel was isolated by filtering on H + 2 /C + 2 coincidences and it was found that we monitor only molecules undergoing a cis-bending motion. The sharp alignment that was registered for acetylene in the C 1s…”

Ultrafast isomerization initiated by X-ray core ionization

“…Isomerization of acetylene (HCCH) to form vinylidene (H 2 CC) has been studied in the neutral molecule, as well as singly and doubly charged acetylene ions 1,2,[24][25][26][27][28][29][30][31][32][33][34][35][36] . Acetylene cations are important not only as a model for molecular dynamics and radiation damage investigations, but also in a range of applications, from plasma devices 37 , combustion 38 , semiconductor manufacturing 39 and to understanding planetary atmospheres 40 .…”

“…Acetylene cations are important not only as a model for molecular dynamics and radiation damage investigations, but also in a range of applications, from plasma devices 37 , combustion 38 , semiconductor manufacturing 39 and to understanding planetary atmospheres 40 . Isomerization of the dication has been investigated in synchrotron experiments 1,2,27,28,34 . Osipov et al 1,2 performed ion-ionphotoelectron and ion-ion-Auger electron coincidence measurements to study the fragmentation of the dication formed on core ionization of acetylene.…”

Angular Distributions of Fragment Ions Produced by Coulomb Explosion of Simple Molecular Dications of Astrochemical Interest

“…5 and related to reaction (7). It is well known this reaction is very fast [42][43][44] and occurs more quickly than the usual rotation period of the precursor dication, which is on the order of picoseconds. The results indicate rota distribution, and therefore t an upper limit to the intrins propensity to occur with th zation vector.…”