Controlled Excitation of the Hydrogen Molecular Ion via Intense Laser Pulses

Date of Completion

January 2010


Physics, Molecular|Physics, Atomic|Physics, Optics




The molecular hydrogen ion has been an enormously well studied molecule. Yet, despite its simplicity of structure, it continues to offer new and intriguing insights regarding the nature of molecules. In this dissertation, we present new experiments regarding the laser-matter interaction of molecular hydrogen. In particular, we demonstrate, for the first time, controlled electronic excitation of the molecular ion. The initial study in this work is a fluorescence experiment that investigates the pathway of excitation. We identify and verify that the excitation due to a single, high-intensity laser pulse proceeds along the following path: ionization of the hydrogen molecule, bond-softening of the molecular ion, and finally direct excitation via a multiphoton transition to an excited state. We build upon this study by varying the laser wavelength, and find evidence that resonance enhanced transitions to excited states are possible. We support this experiment with a theoretical three-level excitation model. Finally, through an ion time-of-flight experiment, we demonstrate that we can control the photodissociation of the molecular hydrogen ion, either by enhancing one-photon bond-softening or by significantly slowing the dissociation process. This last study presents a promising route to further control of molecular hydrogen by significantly enhancing the probability of resonant excitations. ^