High harmonic generation from multiple orbitals in molecular nitrogen
Abstract/Contents
- Abstract
- The high harmonic amplitude and phase is modulated by the electronic structure in atoms and molecules. Past studies of high harmonic generation (HHG) attribute features in the high harmonic spectrum to solely the highest occupied molecular orbital (HOMO). Molecular electrons that are energetically below the HOMO should contribute to laser-driven high harmonic generation. We present the first evidence of HHG from multiple orbitals in molecular nitrogen. We describe measurements of the amplitude and phase of the HHG from aligned nitrogen molecules. The HHG phase from aligned nitrogen is measured interferometrically by beating the nitrogen harmonics with those of an argon reference oscillator in a gas mixture. A rapid phase shift of 0.2 pi is observed in the vicinity of the HHG spectral minimum. We compare the phase measurements to a simulation of the HHG recombination step in nitrogen that is based upon a simple interference model. The results of the simulation suggest that modifications beyond the simple interference model are needed to explain HHG spectra in molecules. Possible modifications are the inclusion of the molecular potential and multiple orbital effects. The importance of multiple orbital contributions to HHG is seen in measurements of the alignment dependent HHG amplitude from aligned nitrogen molecules. Measurements of the HHG spectrum in nitrogen molecules aligned perpendicular and parallel to the laser polarization show new features that indicate the influence of the electrons that occupy the orbital just below the molecular nitrogen HOMO, referred to as the HOMO-1. Evidence of the HOMO-1 is seen in the HHG spectrum obtained at the half revival of a rotational wave packet. Such observations of lower lying orbitals are essential to understand the influence of electron motion on atomic dynamics in laser-excited molecules.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2010 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | McFarland, Brian Keith |
|---|---|
| Associated with | Stanford University, Department of Applied Physics |
| Primary advisor | Bucksbaum, Philip H |
| Thesis advisor | Bucksbaum, Philip H |
| Thesis advisor | Doniach, S |
| Thesis advisor | Kasevich, Mark A |
| Advisor | Doniach, S |
| Advisor | Kasevich, Mark A |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Brian Keith McFarland. |
|---|---|
| Note | Submitted to the Department of Applied Physics. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2010. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2010 by Brian Keith McFarland
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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