B-spline ADC PDF
Preview B-spline ADC
Imperial College London Department of Department of Physics B-spline ADC: Many-body ab initio theory for electron dynamics in strong laser fields Marco Ruberti 10 August Submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Department of Physics of Imperial College London and the Diploma of Imperial College London 1 Declaration of Originality I herewith certify that all the results presented in this thesis are my own and that all else has been appropriately referenced. Marco Ruberti 3 Copyright Declaration The copyright of this thesis rests with the author and is made available under a Creative Commons Attribution Non-Commercial No Derivatives licence. Researchers are free to copy, distribute or transmit the thesis on the condition that they attribute it, that they do not use it for commercial purposes and that they do not alter, transform or build upon it. For any reuse or redistribution, researchers must make clear to others the licence terms of this work. Marco Ruberti 5 Abstract This thesis is focused on the development of an efficient first-principles the- oretical and numerical method based on the many-electron algebraic dia- grammatic construction [ADC(n)] schemes, in order to describe the corre- lated ionisation dynamics in atomic and molecular systems interacting with perturbative and non-perturbative laser fields. The first line of research has focused on the calculation of total single- photonphotoionisationcross-sections,applyingtheStieltjes-Imagingtheory to Lanczos pseudospectra of the ADC Hamiltonian in Gaussian basis. We have established the accuracy of this technique by comparing the ADC- Lanczos-Stieltjes ground-state cross-sections obtained using different lev- els of many-body theory to the experimental ones for a series of organic molecules. We have extended this method to excited states cross-sections showing that a theoretical modelling of photoionisation from excited states requires an intrinsically double excitation theory. However, above 80 eV photonenergyallthreemethodsleadtoinaccurateresultsduetothelimita- tions of the Gaussian basis to describe continuum wave-functions of ionised electrons. The second, main line of research, has therefore been dedicated to con- structing and computationally optimising the first implementation of the single [ADC(1)] and double excitations [ADC(2)] schemes in the B-spline basis,whichisabletoaccuratelydescribethestronglyoscillatingcontinuum orbitals. As first application of this new method, we have calculated the photoionisation cross-sections of noble gas atoms showing that the features thatposeachallengefortheGTOcalculationsarereproducedinaverygood agreement with the experiment. We also have developed a time-dependent version with which we have calculated the HHG spectra of Ar, reproducing the effect of the Cooper minimum, and CO , quantitatively investigating 2 the multi-channel effects on its dynamical minimum. Finally we have pro- vided a numerical answer to the highly topical question of coherence and 7 ionic wavepacket formation in short pulse photoionisation. 8 I would like to thank my supervisor, Dr. Vitali Averbukh, for the precious support and the valuable suggestions that he has made during my PhD. He has motivated me and, at the same time, he has given me the freedom to explore new ideas and to increase my experience. I would like to thank Professor Piero Decleva, who has kindly hosted me several times in the Chemistry department at University of Trieste and has been extremely supportive during the implementation of the B-spline ADC method, dedicating a lot of his time to explain me how B-spline functions work, to answer my questions, to solve my doubts and to constructively debate about the possible ways of implementing the code. I would like to thank Professor Misha Ivanov for the numerous wise suggestions and the stimulating discussions. I would like to thank Renjie Yun for having collaborated with me in the GTO calculations. I would like to thank all the people of the theory office and all the members of the Laser Consortium for having made my PhD experience extremely pleasant not only from a professional point of view, but also from a sociable and human point of view. Finally I would like to thank my family, as without them I would not be here right now writing this dedication. Their support has been my fuel during all these years and will definitely continue to be so. 9
Description:The list of books you might like
