Attosecond phenomena in atoms and molecules driven by intense and ultra-fast laser pulses

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Attosecond phenomena in atoms and molecules driven by intense and ultra-fast laser pulses

Katsoulis, Georgios Petros; (2021) Attosecond phenomena in atoms and molecules driven by intense and ultra-fast laser pulses. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

In this thesis, we study theoretically the physical mechanisms underlying ionisation processes in strongly driven atoms and molecules. We start by investigating double ionisation in atomic systems, in particular, in Helium and Argon. For Helium, we present a new mechanism for double ionisation, called Slingshot Nonsequential Double Ionisation. This mechanism offers an alternative explanation to the anticorrelated two-electron escape found in this work and in previous studies at low intensities of the laser pulses. For Argon, we take the first step towards time-resolving double ionisation triggered by an ultra-short visible laser pulse, using a perpendicularly aligned mid-infrared long laser pulse. Next, we focus on two-electron molecules. We demonstrate that one can significantly increase frustrated double ionisation in the triatomic molecule D₃⁺ by using counter-rotating two-colour circular laser pulses. This enhancement of the frustrated double ionisation probability is achieved by tuning the ratio of the field strengths of the two pulses. We explain the basic features of the system that we study by employing a simplified model of the system. Finally, we investigate nondipole effects in the nonsequential double ionisation of strongly driven two-electron diatomic molecules. We formulate a three-dimensional semiclassical model that fully accounts for magnetic field effects while treating all Coulomb forces. Using this model, we show that the recolliding electron backscatters along the direction of light propagation. This is in striking contrast to the atomic case, where the recolliding electron scatters forward.

Type:	Thesis (Doctoral)
Qualification:	Ph.D
Title:	Attosecond phenomena in atoms and molecules driven by intense and ultra-fast laser pulses
Event:	UCL (University College London)
Open access status:	An open access version is available from UCL Discovery
Language:	English
Additional information:	Copyright © The Author 2021. 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/10140227