Abstract
Ultrafast proton migration and isomerization are key processes for acetylene and its ions. However, the mechanism for ultrafast isomerization of acetylene [HCCH]2+ to vinylidene [H2CC]2+ dication remains nebulous. Theoretical studies show a large potential barrier (> 2 eV) for isomerization on low-lying dicationic states, implying picosecond or longer isomerization timescales. However, a recent experiment at a femtosecond X-ray free-electron laser suggests sub-100 fs isomerization. Here we address this contradiction with a complete theoretical study of the dynamics of acetylene dication produced by Auger decay after X-ray photoionization of the carbon atom K shell. We find no sub-100 fs isomerization, while reproducing the salient features of the time-resolved Coulomb imaging experiment. This work resolves the seeming contradiction between experiment and theory and also calls for careful interpretation of structural information from the widely applied Coulomb momentum imaging method.
| Original language | English |
|---|---|
| Article number | 453 |
| Journal | Nature Communications |
| Volume | 8 |
| Issue number | 1 |
| DOIs | |
| Publication status | Published - 1 Dec 2017 |
Bibliographical note
Funding Information:This work was supported by the AMOS program within the Chemical Sciences, Geosciences and Biosciences Division of the Office of Basic Energy Sciences, Office of Science, US Department of Energy and the Hamburg Center for Ultrafast Imaging. N.M. acknowledges partial financial support from the Czech Ministry of Education (Grants LG15013 and LM2015083). Z.L. thanks the Volkswagen Foundation for support through a Peter Paul Ewald postdoctoral fellowship. Z.L. also thanks Lee-Ping Wang, Koudai Toyota, Sang-Kil Son, Robin Santra, Daniel Haxton, Daniel Neumark, Mohamed El-Amine Madjet, Kota Hanasaki, Victor Kimberg and Yajiang Hao for stimulating discussions.
Publisher Copyright:
© 2017 The Author(s).