Part I: The Construction of a Model-Locked Nd³⁺: Glass Laser and Non-Linear Optical Techniques. Part II: Applications of Picosecond Laser Pulses in Chemistry: Vibrational Relaxation Times in Liquid Alkanes and Alkenes

Citation

Patumtevapibal, Saon (1975) Part I: The Construction of a Model-Locked Nd³⁺: Glass Laser and Non-Linear Optical Techniques. Part II: Applications of Picosecond Laser Pulses in Chemistry: Vibrational Relaxation Times in Liquid Alkanes and Alkenes. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/sska-f577. https://resolver.caltech.edu/CaltechTHESIS:02172022-193613745

Abstract

PART I. The construction and qualitative explanation of the pulsed, mode-locked laser are described: the generation of a train of picosecond 1.06μ pulses is achieved by properly aligning a saturable absorber in the Nd³⁺: glass laser cavity. The pulsewidth, being on a picosecond time scale, has to be measured' by a special two-photon method. In order to make the laser more chemically useful, second harmonic generation of the fundamental (1.06 μ) pulses is necessary. A phase-matched KDP crystal is employed in this process. Some non-linear optical techniques, such as stimulated Raman scattering and self-phased modulation, which generates continuum light from a monochromatic pulses, also enrich the usage of the laser. Azulene experiment is tried with our laser set-up.

PART II. The dephasing times and vibrational lifetimes of C-H stretching vibrations are studied systematically in a series of liquid alkanes and alkenes, using the Raman effect. The results indicate that the vibrational energy loss takes place primarily through the methyl groups in these molecules. A preliminary result of the methylene C-H stretch vibrational lifetime is conducted in liquid CD₃-CH₂-CH₂-CD₃

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