Date of Award
Doctor of Philosophy (PhD)
John B. Hopkins
The chirped pulse regenerative amplification in Nd:YAG lasers is demonstrated to be able to provide picosecond optical pulses with $\sim$gigawatt peak powers at a repetition rate of 2kHz. By taking advantage of the effects of gain narrowing and gain saturation in the regenerative amplifier, it is shown that the chirped amplified pulse width can be varied systematically from $\sim$12ps to 150ps. These high peak power pulses were utilized to perform several picosecond time-resolved resonance Raman spectroscopic experiments. One study involves the investigation of excited state electron transfer in symmetric and asymmetric polypyridineruthenium(II) complexes. The competing influences of solvent relaxation, vibrational relaxation and interligand electronic coupling in the metal-to-ligand charge transfer (MLCT) excited state were investigated. The results indicate that vibrational relaxation is the dominant mechanism for electron ligand-localization phenomenon. In addition, the results from dynamic solvent effects study indicate that the solvent motions do not contribute significantly to this localization. The interligand electron transfer during the lifetime of the MLCT excited state was also investigated using a variety of mixed-ligand Ru(II) complexes. The rate of this electron transfer is found to depend greatly on the free energy gap between the two dissimilar ligands. The excited state proton transfer in a pentaamineruthenium(II) complex was also investigated. The role of ultrafast solvent relaxation in facilitating an accelerated non-equilibrium proton transfer in the MLCT excited state of this complex was studied. No proton transfer was observed to occur with a rate significantly faster than that predicted by diffusion-controlled kinetics. This result indicates that the charge on the heteroatom in the reduced ligand expected to receive the proton is not strong enough to structure the solvent molecules in such a way which facilitates non-equilibrium proton transfer.
Chang, Yong Joon, "I. Temporal Compression in Chirped Pulse Regenerative Amplification. II. Picosecond Time-Resolved Raman Study of Excited State Charge Transfers." (1990). LSU Historical Dissertations and Theses. 4902.