Mountney, Miles Elliott;
(2025)
Interaction of XUV and X-ray pulses
with diatomic molecules.
Doctoral thesis (Ph.D), UCL (University College London).
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Abstract
In this thesis, we study theoretically the angular distributions of electron escape and the process of molecular dissociation during the interaction between diatomic molecules and intense laser pulses in the ultraviolet and X-ray range. We start by demonstrating theoretically a one-to-one mapping between the direction of electron ionization and the phase delay between a linearly-polarized vacuum ultraviolet and a circularly-polarized infrared laser pulse for the N2 molecule. We compute the dipole matrix element to transition from an initial bound state to the continuum using quantum mechanical techniques. Following the release of the electron in the infrared pulse, we evolve classical trajectories. Neglecting the Coulomb potential and accounting for quantum interference, we compute the distribution of the direction and magnitude of the final electron momentum. We then streak single-photon ionization processes, driven by an X-ray pulse, in open-shell molecules. We obtain continuum molecular wavefunctions while accounting for the singlet or triplet total spin symmetry of the molecular ion. After ionization, we streak the electron dynamics using a circular infrared pulse. For a high intensity infrared pulse, we achieve control of the angle of escape of the ionizing electron. For a low intensity infrared pulse, we obtain final electron momenta distributions on the plane of the infrared pulse and compare them to the angular patterns of electron escape solely due to the X-ray pulse. Finally, we study the interaction between molecular oxygen, O2, and an extreme ultraviolet pulse. We compute potential energy curves of O2 up to O2+ 2 . We find the dissociation limits of these states and the atomic fragments to which they dissociate. We use the Velocity Verlet algorithm to account for the nuclear dynamics. Using Monte Carlo simulations which monitor the nuclear motion and electronic structure of the molecule, we obtain kinetic energy release distributions of the atomic fragments of O2.
| Type: | Thesis (Doctoral) |
|---|---|
| Qualification: | Ph.D |
| Title: | Interaction of XUV and X-ray pulses with diatomic molecules |
| Open access status: | An open access version is available from UCL Discovery |
| Language: | English |
| Additional information: | Copyright © The Author 2025. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10203875 |
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