No description available.

No description available.

Thesis (Ph. D.)--University of Chicago, Department of Chemistry, 2002. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI Company.

Not available / text

No description available.

Thesis (Ph.D.)--University of California, Berkeley, 1963. / "UC-4 Chemistry" -t.p. "TID-4500 (19th Ed.)" -t.p. Includes bibliographical references (p. 84-85).

Thesis (Ph. D.)--University of Chicago, Dept. of Chemistry, December 1997. / Includes bibliographical references. Also available on the Internet.

Magnetic properties of cobalt clusters (20 N 200) were studied in molecular beams. The magnetization of cobalt clusters is studied at a broad range of temperatures, magnetic fields and clusters sizes. It is shown that the agnetization of ferromagnetic clusters in a cluster beam can be understood as an adiabatic process using the avoided crossing theory. Besides the ground state that bears magnetic moment of about 2 Bohr magneton per atom, an excited state that has 1 Bohr magneton per atom was discovered for every cobalt cluster observed. The energy separations between the two states was investigated by photo-ionization experiments. The ionization threshold shows that the energy gap between the two states is on the order of 0.1 eV for small clusters (N 100) and vanishes for larger clusters. Experiments also show that the polarizability of the excited state is lower than that of the ground state, which indicates a significant electronic tructure difference between the two states. Two states are also found for iron clusters (20 N 200) for which the magnetic moments per atom are about 3 Bohr magneton for the ground state and 1 Bohr magneton for the excited states. This explains the fractional magnetic moments as well as the local magnetic order observed above the Curie temperatures for iron group ferromagnets. Further experiments show two states for manganese clusters for which the ground state has magnetic moment of 1 Bohr magneton per atom in about the same size range. This suggests that the two states are a universal phenomenon of 3d transition metal clusters, which originate from the interaction between 3d and 4s electrons.

Molecular beam methods provide rich possibilities for producing and studying novel species. These can include (1) clusters that would not be accessible in conventional gas phase chemistry and (2) generation and stabilization of reactive species. The methods that allow for (2) can be extended to (3) survey of evolving product chemistry following an initial fast impulse (photolysis, pyrolysis, electrical discharge) on some reactant. The projects undertaken touch on all three of these areas, but the centerpiece and most challenging project applies to the production, for the first time, of several novel organosilicon species. We first present an efficient molecular beam method of silylene production, a method meant to be used for the study of silylene chemistry. A particular goal was to produce a silanone. We present evidence that a silanone has been produced. Of even greater interest is the possible molecular beam production of small disilynes. This development would finally open the future opportunity to study these species in detail. Key to our approach here was the use of laser ablation of several different selected custom synthesized precursors. Based on past work, our expectation was that certain bonds in the precursors would selectively be broken, leading to the production of disilynes that then would be stabilized in cold gas expansions. For three different precursors, we present consistent evidence that the target disilynes were in fact produced. These conclusions were not clear in our initial analysis of the data; only a later and different form of analysis led to convincing evidence that the experiments were in fact successful. Because the main component of the intended project did not at first seem to have been successful, work in several other areas was carried out, related to themes (1) and (3). Related to (1) was methods development, demonstrating the ability to produce clusters of porphyrin and porphyrin-C60, for later extended study. For (3), study was carried out on the possible role of halogen adducts on alkylbenzenes in inhibiting PAH formation following corona discharge. Similarly for (3), method development was carried out to enable to study early product chemistry following the pyrolysis of triacylglycerols (triglycerides). / acase@tulane.edu