High harmonic generation in atoms is well understood in terms of the three step model (ionization, propagation and recombination), and much attention has been payed to the dynamics of the continuum electron in the propagation step. However, a molecular medium can be used to further understand the ionization and recombination steps. High harmonic generation can also be used to probe the dynamics of rotational and vibrational wave packets in molecular media.
This thesis reports on two experiments using high harmonic generation from molecular media. In the first experiment, an impulsive Raman pump is used to excite a rotational wave packet in the molecular system, and a second time-delayed pulse generates high harmonics from the rotationally excited medium. Both the intensity and the phase of the high harmonic emission are measured. The general features of the orientational dipole are extracted from the phase and intensity modulations.
A second experiment uses a vibrationally excited molecule as the high harmonic generation medium. The coherently excited molecular vibrations modulate the intensity of the high harmonic generation. Using high harmonic generation as a probe makes it possible to see all excited modes include two modes which were not present using a comparable visible probe. The rotational dephasing of the vibrational wave packet is also observed.
}, year = {2008}, publisher = {University of Colorado Boulder}, address = {Boulder}, }