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Imaging photoinduced isomerization in triply ionized acetonitrile

Noah Frese1,*,†, Sergio Díaz-Tendero4,2,3,*,‡, Debadarshini Mishra1, Aaron C. LaForge1, Cameron Brady1, Fernando Martín5,2,§, and Nora Berrah1,∥

  • *These authors contributed equally to this work.
  • †Contact author: noah.frese@uconn.edu
  • ‡Contact author: sergio.diaztendero@uam.es
  • §Contact author: fernando.martin@uam.es
  • ∥Contact author: nora.berrah@uconn.edu
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Phys. Rev. A 114, 043106 – Published 8 October, 2026

DOI: https://doi.org/10.1103/z6qs-63z6

Abstract

Isomerization is a fundamental process usually initiated in molecules via photoionization. Using intense femtosecond IR laser pulses, in combination with coincident Coulomb explosion imaging, we are able to reconstruct the structure of the acetonitrile tri-cation after it undergoes isomerization and prior to fragmentation. Using momentum imaging, the Newton diagrams in tandem with native frame analysis reveal the signature of a triangular geometry. This indicates that upon photoionization to a triply ionized state, acetonitrile undergoes a clear structural change from its linear canonical form along with hydrogen migration. We further corroborate this with the aid of quantum chemistry calculations, which allow us to fully resolve this unique isomerization process. Understanding the underlying mechanisms behind such complex processes is relevant to biology and industrial applications.

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Phys. Rev. A 114, 043106– Published 8 October, 2026
  • Received 15 January 2026
  • Accepted 31 August 2026
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Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

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