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@PHDTHESIS{Walmsley:612494,
      author       = {Walmsley, Tiffany},
      othercontributors = {Burt, Michael and Ritchie, Grant},
      title        = {{C}oulomb explosion imaging and covariance analysis of
                      concurrent fragmentation mechanisms},
      school       = {University of Oxford},
      type         = {Dissertation},
      publisher    = {University of Oxford},
      reportid     = {PUBDB-2024-05347},
      pages        = {256},
      year         = {2024},
      note         = {Dissertation, University of Oxford, 2024},
      abstract     = {This thesis uses Coulomb explosion imaging and covariance
                      analysis to characterise concurrent fragmentation processes
                      generating identical sets of products via different reaction
                      pathways, highlighting the potential of extending these
                      methods to study the photochemistry of larger, more
                      chemically relevant species than those that have previously
                      been studied. The photodissociation dynamics of CH2I2 at
                      202.5 nm were investigated using site-selective ionisation
                      at the I 4d orbitals using photons of 95 eV. A concerted
                      three-body dissociation process was assigned using charge
                      transfer features and time-dependent covariance. Dynamic
                      changes to the C-I internuclear distances and I-C-I bond
                      angle were characterised, demonstrating the potential of
                      Coulomb explosion imaging to simultaneously map potential
                      energy surfaces of reaction dynamics along multiple degrees
                      of freedom. Site-selective ionisation of 1- and
                      2-iodopropane at the I 4d orbitals was carried out using
                      photons of 95 eV. Modified three-dimensional momentum
                      covariance analysis techniques were used to disentangle
                      fragmentation processes generating the same sets of products
                      as well as the individual steps of multi-step fragmentation
                      mechanisms. Observable isomeric differences demonstrated the
                      sensitivity of individual fragmentation processes, and the
                      corresponding nuclear dynamics, to the geometry and charge
                      distribution of the parent polycation species. Iodobenzene
                      was site-selectively ionised at the I 4d orbitals using
                      photons of 120 eV, and valence-shell ionisation was also
                      conducted using 800 nm laser pulses. Covariance analysis
                      techniques were employed to analyse the range of products
                      generated from stable and metastable phenyl cations and
                      polycations, demonstrating how concurrent fragmentation
                      processes generating long-lived species in lowly-charged
                      cationic states can be characterised. Valence-shell
                      ionisation could initially ionise more atomic sites than
                      just iodine, leading to fragmentation channels that were not
                      observed with site-selective, inner-shell ionisation. Both
                      ionisation regimes generated similar sets of products but on
                      different relative timescales due to initially populating
                      different electronic excited states. Each ionisation regime
                      results in many observable fragmentation processes, but
                      photoelectron information is required to relate specific
                      fragmentation channels to specific ionisation and charge
                      generation/redistribution processes.},
      keywords     = {Chemistry, Physical and theoretical (Other)},
      cin          = {DOOR ; HAS-User},
      cid          = {I:(DE-H253)HAS-User-20120731},
      pnm          = {6G2 - FLASH (DESY) (POF4-6G2)},
      pid          = {G:(DE-HGF)POF4-6G2},
      experiment   = {EXP:(DE-H253)F-BL1-20150101},
      typ          = {PUB:(DE-HGF)11},
      doi          = {10.5287/ORA-Z6JGMXRRA},
      url          = {https://bib-pubdb1.desy.de/record/612494},
}