With more atoms in a system, coupling between quantum states complicates the system dynamics. We shine intense laser pulses on three systems with increasing complexity: a molecule, a dimer, and a solid.
For single molecules, a 400 nm photon excites NO_2 and initiates a dissociation process. We probe the dynamics using a strong laser pulse to ionize the molecule, and detect the resulting electrons and ions. The evolution of the NO-O molecular bond was directly measured in our experiment.
For dimers, a laser pulse removes three electrons from (CO)_2. The dimer breaks up into C^+, O^+ and CO^+. Compared to a monomer, CO^{2+} in the dimer has a new prompt dissociation pathway that produces fragments with higher kinetic energy. Calculation shows that the Coulomb field of the neighboring CO^+ modifies the electronic state of the dimer, giving rise to a prompt channel. Coupling between different charge state configurations results in a new dimer electronic state, which leads to dissociation with higher kinetic energy.
For solids, coupling among many atoms creates bands and a bandgap that plays the role of the ionization potential and reduces the threshold for electron-hole pair generation. Thus, solids are a good medium for high-order harmonic generation at the high repetition rates needed for frequency combs. We generate up to the 7th harmonic in silicon and zinc oxide with femtosecond pulses from a thulium fiber laser.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/38504 |
| Date | 29 November 2018 |
| Creators | Ding, Xiaoyan |
| Contributors | Corkum, Paul |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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