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Title: Studies of ultrafast molecular photofragmentation and dynamics using fast imaging sensors
Author: Amini, Kasra
ISNI:       0000 0004 7430 5608
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2017
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In this thesis, the three-dimensional (3D) and multi-mass imaging capabilities of the Pixel Imaging Mass Spectrometry (PImMS) camera are demonstrated in a range of ion imaging experiments. The full 3D velocity distributions of the CO+ and S+ fragments, resulting from the photodissociation of OCS, are shown to be successfully captured with the PImMS camera by recording time-resolved slices through the full Newton sphere. In the laser-induced Coulomb explosion of difluoroiodobenzene (DFIB) and dihydroxybromobenzene (DHBB) isomers, two- and three-fold covariance analysis revealed angular correlations between recoil ions, recorded by the PImMS2 camera, which were used to unambiguously identify structural isomers present in pure and mixed molecular beam samples. The Coulomb explosion imaging (CEI) technique and covariance analysis was extended to a femtosecond-resolved pump-probe study of the trans-cis isomerization in 4,4'2-difluoroazobenzene (DFAB). Using a background-subtraction method, two-colour time-dependent features are extracted and are tentatively assigned to cis-DFAB with vibrationally hot trans-DFAB following S2 ← S0 excitation of vibrationally cold trans-DFAB. The Coulomb explosions of laser-aligned and mixed-field oriented 2,6-DFIB molecules induced by strong-field or inner-shell ionization were found to be comparable, with only subtle differences observed. Using multi-photon inner-shell ionization with an ultrabright, femtosecond 11.6 nm free-electron laser probe pulse, high charge states of iodine in CH3I and 2,6-DFIB are generated. The ensuing photodissociation, initiated by a 267 nm pump pulse, and charge transfer dynamics were observed in 'real-time' with the PImMS camera.
Supervisor: Brouard, Mark Sponsor: Engineering and Physical Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available