Dissertation / PhD Thesis

PUBDB-2026-00745

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Coulomb explosion as a high-dimensional probe of single molecules

Richard, B. (Corresponding author)Extern* ; Santra, R. (Thesis advisor)CFEL*XFEL.EU*DESY* ; Inhester, L. (Thesis advisor)CFEL*Extern*XFEL.EU*DESY*

2024

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Please use a persistent id in citations: urn:nbn:de:gbv:18-ediss-131275

Abstract: The past decades saw the development of X-ray induced Coulomb ex-plosion imaging as one of several methods to perform single-particlemolecular imaging on a femtosecond timescale. It has been enabledby the advent of x-ray free electron lasers. It works by firing intenseultrashort x-ray pulses on a gas jet of molecules. A single pulserapidly and strongly ionizes a single molecule, resulting in its ultra-fast dissociation, after which the momenta of the atomic fragmentsare measured in coincidence. This method has been successfully ap-plied to molecules composed of few atoms, but its extension to largersystems remains a challenge. In this thesis, we use simulation and ad-vanced analysis techniques to explore the potential of Coulomb explo-sion imaging and its applicability to larger molecules, focusing on the2-iodopyridine molecule (C5H4NI), which has been measured experi-mentally. We show that, despite detecting only few fragments in co-incidence, Coulomb explosion imaging provides meaningful imagesof the molecule. Analyzing our simulations in detail, we establishthat collisions between atoms during the explosion induce measur-able correlations between the momenta of the measured fragments,indicating that a large amount of information is hidden in the highdimensionality of the data. We then include the vibrational ground-state fluctuations of the molecule in our simulations, and show thatthey also leave a fingerprint in the ion-ion correlations, demonstrat-ing that Coulomb explosion can be used to image the complex collec-tive features of a distribution of molecular structures. To apply thoseanalyses to the experiment, we develop an algorithm to systematicallyfind the correlations in the experimental data. Our method succeedsdespite the random orientation of the molecule in the lab frame andthe limited efficiency of the detectors, thereby opening new ways tointerpret Coulomb explosion data, and allowing to exploit some ofits untapped potential.

Note: Dissertation, University of Hamburg, 2024

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Contributing Institute(s):

1. FS-CFEL-3 (CFEL-DESYT)
2. CFEL-Theory (FS-CFEL-3)

Research Program(s):

1. 631 - Matter – Dynamics, Mechanisms and Control (POF4-631) (POF4-631)
2. DFG project G:(GEPRIS)390715994 - EXC 2056: CUI: Tiefe Einblicke in Materie (390715994) (390715994)

Experiment(s):

1. No specific instrument

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