title: Femtosecond electron dynamics driven by ponderomotive gradients
creator: Heldt, Tobias Valentin
subject: ddc-530
subject: 530 Physics
description: Electrons driven by the oscillating electric field of intense femtosecond laser pulses experience an effective cycle-averaged ponderomotive potential. This thesis investigates the ponderomotive effects of circularly polarized few-cycle pulses and standing waves on photoionization, photoemission, and the subsequent electron motion. Reconstructing the time-dependent dipole moment of recolliding electron wave packets from an extreme ultraviolet absorption spectrum reveals an envelope-driven recollision channel in circularly polarized light, as predicted by the theory of recolliding periodic orbits. Furthermore, tomography of photoelectron angular distributions is achieved using velocity-map imaging  within a femtosecond enhancement cavity operating at 100MHz. This cavity supports two counter-propagating pulses that form a transient standing wave at the focus. Exploiting  the standing wave structure allows to probe the photoemission at different crystal facets of a tungsten nanotip and to minimize the source volume of above-threshold ionization. In addition, the high-intensity Kapitza-Dirac effect for resonantly ionized electrons in the picosecond regime is presented together with still unexplained diffraction results for femtosecond pulses. The intense intra-cavity standing waves are a promising tool for coherent control of electron matter waves, potentially advancing the development of a femtosecond electron interferometer at low energies.
date: 2025
type: Dissertation
type: info:eu-repo/semantics/doctoralThesis
type: NonPeerReviewed
format: application/pdf
identifier: https://archiv.ub.uni-heidelberg.de/volltextserver/36534/1/PhD-Thesis_Tobias_Heldt_open.pdf
identifier: DOI:10.11588/heidok.00036534
identifier: urn:nbn:de:bsz:16-heidok-365344
identifier:   Heldt, Tobias Valentin  (2025) Femtosecond electron dynamics driven by ponderomotive gradients.  [Dissertation]     
relation: https://archiv.ub.uni-heidelberg.de/volltextserver/36534/
relation: info:eu-repo/grantAgreement/EC/FP7/20FUN01 TSCAC, 23FUN03 HIOC
rights: info:eu-repo/semantics/openAccess
rights: Please see front page of the work (Sorry, Dublin Core plugin does not recognise license id)
language: eng