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  • `Attoclock' experiments on atomic and molecular hydrogen

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    Undurti, Satya_Final Thesis_Redacted.pdf (20.00Mb)
    Author(s)
    Undurti, Sainadh S.
    Primary Supervisor
    Litvinyuk, Igor
    Sang, Robert
    Year published
    2018-08-24
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    Abstract
    The current thesis aims at benchmarking strong- eld physics with the help of precision measurements performed on the simplest atomic (H) and molecular (H2) systems. The importance of H in validating strong- eld models is demonstrated through the rst set of experimental data. It aims at calibrating the absolute Carrier-envelope phase (CEP) of few-cycle laser pulses using H against complete ab initio solution of the three dimensional time-dependent Schr odinger equation (3D-TDSE). Subsequent set of measurements with noble gases against widely used strong- eld models based on single-active electron (SAE) approximation, is shown ...
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    The current thesis aims at benchmarking strong- eld physics with the help of precision measurements performed on the simplest atomic (H) and molecular (H2) systems. The importance of H in validating strong- eld models is demonstrated through the rst set of experimental data. It aims at calibrating the absolute Carrier-envelope phase (CEP) of few-cycle laser pulses using H against complete ab initio solution of the three dimensional time-dependent Schr odinger equation (3D-TDSE). Subsequent set of measurements with noble gases against widely used strong- eld models based on single-active electron (SAE) approximation, is shown to reveal a systematic o set of 0:25 radians in tagging CEP, questioning the validity of such models. The second experimental study forms the main result of this thesis, that attempts to resolve the ongoing debate on tunnelling times (tunnelling delays in the context of strong- eld physics). We address this by employing the `attoclock' technique with 6 fs pulses on H and validating the results against full numerical solutions of ab initio 3D-TDSE. The validated numerical codes are then used to arti cially screen the parent ion-electron interaction, concluding that the tunnelling time 1.8 as. The nal experimental results presented in this dissertation are the alignmentdependent attoclock measurements using both few-cycle (7 fs) and multi-cycle (28 fs) pulses on H2. The measured attoclock observable for various molecular orientations (in laser polarisation frame) shows a strong modulation with a periodicity of . Initial ab initio simulations for few-cycle pulses under the frozen-nuclei and SAE approximations, fail to explain these observations. Further experimental studies with H2/D2 (50:50 mixed gases) show no signi cant relative di erences among the attoclock observables, suggesting a prominent role of the electron-electron correlations at play. The ongoing study is believed to have far reaching implications in applications such as studying molecular dissociation processes and tomography.
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    Thesis Type
    Thesis (PhD Doctorate)
    Degree Program
    Doctor of Philosophy (PhD)
    School
    School of Environment and Sc
    DOI
    https://doi.org/10.25904/1912/3311
    Copyright Statement
    The author owns the copyright in this thesis, unless stated otherwise.
    Subject
    Atomic hydrogen
    Molecular hydrogen
    Attoclock
    Tunnelling times
    Few-cycle
    Multi-cycle
    Publication URI
    http://hdl.handle.net/10072/381373
    Collection
    • Theses - Higher Degree by Research

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