Download or read book CAVITY RINGDOWN LASER ABSORPTI written by Tongmei Ma and published by Open Dissertation Press. This book was released on 2017-01-27 with total page 110 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Cavity Ringdown Laser Absorption Spectroscopy of Free Radicals" by Tongmei, Ma, 馬彤梅, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled CAVITY RINGDOWN LASER ABSORPTION SPECTROSCOPY OF FREE RADICALS submitted by MA TONGMEI for the degree of Doctor of Philosophy at The University of Hong Kong in July 2004 This thesis reports studies of the electronic transitions of gas phase diatomic transition metal containing free radicals in the spectral region of 440-520 nm using the technique of laser vaporization/reaction with supersonic free jet expansion (LVRFE) and cavity ringdown laser absorption spectroscopy (CRLAS) with a pulsed Nd: YAG pumped dye laser system. This combination of experimental techniques offered great advantages in versatility of producing metal containing free radicals and sensitivity for their detection. Three different molecular transition systems were recorded and analyzed. They are the (0,0), (1,0) and (2,0) bands of the 2 2 3 3 LΦ - XΔ transition of iridium carbide (IrC); the (0,0) band of the EΔ - X Δ 7/2 5/2 2 + 2 + transition of vanadium nitride (VN); the (2,0) and (2,1) bands of the BΣ - XΣ transition of yttrium oxide (YO), respectively. Least squares fit of measured line positions of these transitions yielded vibrational, rotational and spin fine structure constants for the electronic states studied. Molecular orbital energy level diagrams have been constructed to explain the observed molecular properties in these free radicals. In addition, a setup of cavity enhanced absorption spectroscopy (CEAS) using tunable continuous wave diode laser and an optical cavity with ultra-high reflectivity mirrors was constructed. Data acquisition procedure is modified to extract the highest signal at a specific time period rather than to record the -9 -1 time-integrated signal as usual. An absorption sensitivity of about 4.8 10 cm could be achieved. DOI: 10.5353/th_b3013734 Subjects: Free radicals (Chemistry) Cavity-ringdown spectroscopy Transition metal complexes Laser spectroscopy