Interaction Potentials of Atom-Molecule and Molecule-Molecule Systems from Crossed Beam Experiments

Author: Slankas, John T.

Year: 1979

Degree: Dissertation (Ph.D.)

Advisor: Kuppermann, Aron

Committee Member: Unknown, Unknown

Option: Chemistry

DOI: 10.7907/9d88-2h72

Abstract

The text of this thesis is comprised of eight chapters and six appendices.

The first chapter is an introduction, overviewing the purpose of the experiments and outlining the remainder of the thesis. Chapters 2 and 3 survey the theory of intermolecular potentials and of elastic scattering and provide the basis for interpreting the results obtained. Chapter 4 reviews the investigations and optimizations/ characterizations made to the apparatus and procedures.

Chapters 5, 6, and 7 present the results. Chapter 5 details studies on the H2 (D2) + Ar system. Essentially three independent experiments were performed on this system to check internal consistency. The results obtained were also consistent with other laboratories, some using different techniques. Tue effects of the non-spherical part of the intermolecular potential were found to be negligible, within error of the experiment. A potential model with five independent parameters, the Simmons-Parr-Finlan-modified Dunham (SPFD), was found to provide the best representation of the intermolecular potential. In Chapter 6, studies on the He + CH4, NH3, H2O, SF6 systems are described. Central-field SPFD potentials were found to provide satisfactory descriptions of the intermolecular potential for these systems. The potentials described for the He + isoelectronic hydride series (CH4, NH3, H2O) are physically reasonable; however, the He + SF6 system is shown to have an anomalously deep potential well which can not be readily explained. Central-field SPFD potentials were found to provide satisfactory descriptions of the intermolecular potential for all these systems. Chapter 7 presents the results of studies on the H2 (D2) + NH3, H2O systems. Results for H2 and D2 with each hydride molecule were found to be in agreement with each other, as expected. Again, the five-parameter central-field SPFD potentials provided satisfactory descriptions of the intermolecular potential. In Chapter 8 we present a summary of the results and conclusions of the intermolecular potential studies performed.

Appendices 1, 2, 3, and 4 outline changes to and tests of the apparatus which represent considerable effort. They were essential to establish the reliability and quality of the experimental data and, furthermore, to increase the capabilities of the apparatus.

Appendices 5 and 6 present the results of two additional experiments on which the author played a major role. Each represents a paper in press.

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