Ionization of the Hydrogen Molecular Ion by Strong Infrared Laser Fields
| dc.contributor.advisor | Horbatsch, Marko | |
| dc.creator | Tsednee, Tsogbayar | |
| dc.date.accessioned | 2015-01-26T14:05:15Z | |
| dc.date.available | 2015-01-26T14:05:15Z | |
| dc.date.copyright | 2014-05-05 | |
| dc.date.issued | 2015-01-26 | |
| dc.date.updated | 2015-01-26T14:05:15Z | |
| dc.degree.discipline | Physics And Astronomy | |
| dc.degree.level | Doctoral | |
| dc.degree.name | PhD - Doctor of Philosophy | |
| dc.description.abstract | The ionization of simple molecular targets, such as molecular hydrogen, or even the molecular hydrogen ion ($\mbox{H}^{+}_{2}$) by strong laser fields has become the focus of experimental research in the past few decades. On the theoretical side the problem presents two challenges: on the one hand one has to solve the problem numerically even in the one-electron case ($\mbox{H}^{+}_{2}$), since no analytic closed-form solution is possible; on the other hand there is the many-electron problem ($\mbox{H}_{2}$ and other diatomic molecules, such as $\mbox{N}_{2}$, $\mbox{O}_{2}$, etc.), which currently is at the limit of computational feasibility ($\mbox{H}_{2}$), or exceeds it for molecules with more than two electrons. In this thesis the single-electron problem of the hydrogen molecular ion in intense continuous-wave laser fields is addressed. The focus is on ionization rates of the molecule as a function of internuclear separation within the framework that the motion of the nuclei can be neglected (Born-Oppenheimer approximation). First, the problem of the DC limit is considered, i.e., a strong static electric field is applied along the internuclear axis. The field ionization rate is calculated by solving a stationary non-hermitean Schr\"odinger equation in a suitable coordinate system (prolate spheroidal coordinates). Some previously obtained values from the literature are reproduced; for larger internuclear separations improved values are obtained. For the more interesting case of an infrared (continuous-wave) laser field Floquet theory is applied to transform the time-dependent Schr\"odinger equation for the electronic motion into a non-hermitean coupled-channel stationary problem. Ionization rates are found as a function of laser frequency ($\omega$), and the low-frequency limit is pursued to understand how one can establish a connection to the DC limit. Results are obtained for the two lowest electronic states, which are named the {\it gerade} and {\it ungerade} (or even and odd) ground states in the field-free limit. From the calculated results it is observed that the ionization rates peak at certain internuclear separations, such that a dissociating $\mbox{H}^{+}_{2}$ molecule will be preferentially field ionized. In addition, the thesis reports on calculations of so-called high harmonic generation - a process where photo-electrons acquire energy from the laser field, are deflected back by the linearly polarized laser and recombine under the emission of photons with energies that correspond to odd-integer multiples of the laser photon energy. | |
| dc.identifier.uri | http://hdl.handle.net/10315/28160 | |
| dc.language.iso | en | |
| dc.rights | Author owns copyright, except where explicitly noted. Please contact the author directly with licensing requests. | |
| dc.subject | Atomic physics | |
| dc.subject | Molecular physics | |
| dc.subject | Quantum physics | |
| dc.subject.keywords | Spectral methods | en_US |
| dc.subject.keywords | Hydrogen molecular ion | en_US |
| dc.subject.keywords | Ionization rate | en_US |
| dc.subject.keywords | Strong laser fields | en_US |
| dc.subject.keywords | High-harmonic generation | en_US |
| dc.title | Ionization of the Hydrogen Molecular Ion by Strong Infrared Laser Fields | |
| dc.type | Electronic Thesis or Dissertation |
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