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Application of algebraic diagrammatic construction theory with B-spline and gaussian-type basis on static and dynamical electronic systems

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Title: Application of algebraic diagrammatic construction theory with B-spline and gaussian-type basis on static and dynamical electronic systems
Authors: Yun, Renjie
Item Type: Thesis or dissertation
Abstract: This thesis is focused on the application of an efficient ab initio numerical method based on algebraic diagrammatic construction (ADC) theory to the calculation of many-electron dynamics in atomic and molecular systems, in the absence or presence of (non-)perturbative laser fields. The first part of the research applies the ADC method to the calculation of Penning ionisation widths. Along with the numerical method, an analytical formula for PI is also derived in the asymptotic regions. The calculations show the exact region of inter-molecular distances, where the electron transfer mechanism in PI is the dominant one. It also shows that the regime of the energy transfer mechanism in PI cannot be reached in collisions even when approaching zero collisional temperature, but might be realised in He droplet environment. The second part of the research applies the ADC method to the calculations of high harmonic generation (HHG) spectra with counter-rotating bi-circular fields in B-spline basis. B-spline basis set is able to accurately describe the strongly oscillating continuum orbitals, such as in the case of HHG processes. Such a task poses a challenge to Gaussian-type basis which will easily run into linear dependence problems for high energy and high resolution calculations. The calculations show that, for He, Ne and Ar, the difference between the intensities of left- and right-circularly polarised harmonics is present at single atom level. The dominant polarisation shifts from left to right around the ionisation potential of the atom. The calculated spectra also suggest that changing the relative intensity of the driving \omega_0 and 2\omega_0 pulses, or varying the time delay between them has limited control over the intensity difference in the spectra at single atom level.
Content Version: Open Access
Issue Date: Sep-2018
Date Awarded: Feb-2019
URI: http://hdl.handle.net/10044/1/67916
DOI: https://doi.org/10.25560/67916
Copyright Statement: Creative Commons Attribution NonCommercial No Derivatives Licence
Supervisor: Averbukh, Vitali
Sponsor/Funder: Lee Family Scholarship
Department: Physics
Publisher: Imperial College London
Qualification Level: Doctoral
Qualification Name: Doctor of Philosophy (PhD)
Appears in Collections:Physics PhD theses