Citation
Gutschick, Vincent P. (1972) 1. Ultrasonic studies of binary liquid structure in the critical region. Theory and experiment for the 2,6lutidine/water system. 2. HartreeFock calculations of electric polarizabilities of some simple atoms and molecules, and their practicality. 3. Calculation of vibrational transition probabilities in collinear atomdiatom and diatomdiatom collisions with LennardJones interaction. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/B8K2V070. https://resolver.caltech.edu/CaltechTHESIS:04112016103207668
Abstract
Part 1. Many interesting visual and mechanical phenomena occur in the critical region of fluids, both for the gasliquid and liquidliquid transitions. The precise thermodynamic and transport behavior here has some broad consequences for the molecular theory of liquids. Previous studies in this laboratory on a liquidliquid critical mixture via ultrasonics supported a basically classical analysis of fluid behavior by M. Fixman (e. g., the free energy is assumed analytic in intensive variables in the thermodynamics)at least when the fluid is not too close to critical. A breakdown in classical concepts is evidenced close to critical, in some welldefined ways. We have studied herein a liquidliquid critical system of complementary nature (possessing a lower critical mixing or consolute temperature) to all previous mixtures, to look for new qualitative critical behavior. We did not find such new behavior in the ultrasonic absorption ascribable to the critical fluctuations, but we did find extra absorption due to chemical processes (yet these are related to the mixing behavior generating the lower consolute point). We rederived, corrected, and extended Fixman's analysis to interpret our experimental results in these more complex circumstances. The entire account of theory and experiment is prefaced by an extensive introduction recounting the general status of liquid state theory. The introduction provides a context for our present work, and also points out problems deserving attention. Interest in these problems was stimulated by this work but also by work in Part 3.
Part 2. Among variational theories of electronic structure, the HartreeFock theory has proved particularly valuable for a practical understanding of such properties as chemical binding, electric multipole moments, and Xray scattering intensity. It also provides the most tractable method of calculating firstorder properties under external or internal oneelectron perturbations, either developed explicitly in orders of perturbation theory or in the fully selfconsistent method. The accuracy and consistency of firstorder properties are poorer than those of zeroorder properties, but this is most often due to the use of explicit approximations in solving the perturbed equations, or to inadequacy of the variational basis in size or composition. We have calculated the electric polarizabilities of H_{2}, He, Li, Be, LiH, and N_{2} by HartreeFock theory, using exact perturbation theory or the fully selfconsistent method, as dictated by convenience. By careful studies on total basis set composition, we obtained good approximations to limiting HartreeFock values of polarizabilities with bases of reasonable size. The values for all species, and for each direction in the molecular cases, are within 8% of experiment, or of best theoretical values in the absence of the former. Our results support the use of unadorned HartreePock theory for static polarizabilities needed in interpreting electronmolecule scattering data, collisioninduced light scattering experiments, and other phenomena involving experimentally inaccessible polarizabilities.
Part 3. Numerical integration of the closecoupled scattering equations has been carried out to obtain vibrational transition probabilities for some models of the electronically adiabatic H_{2}H_{2} collision. All the models use a LennardJones interaction potential between nearest atoms in the collision partners. We have analyzed the results for some insight into the vibrational excitation process in its dependence on the energy of collision, the nature of the vibrational binding potential, and other factors. We conclude also that replacement of earlier, simpler models of the interaction potential by the LennardJones form adds very little realism for all the complication it introduces. A brief introduction precedes the presentation of our work and places it in the context of attempts to understand the collisional activation process in chemical reactions as well as some other chemical dynamics.
Item Type:  Thesis (Dissertation (Ph.D.))  

Subject Keywords:  Chemistry  
Degree Grantor:  California Institute of Technology  
Division:  Chemistry and Chemical Engineering  
Major Option:  Chemistry  
Thesis Availability:  Public (worldwide access)  
Research Advisor(s): 
 
Thesis Committee: 
 
Defense Date:  8 September 1971  
Funders: 
 
Record Number:  CaltechTHESIS:04112016103207668  
Persistent URL:  https://resolver.caltech.edu/CaltechTHESIS:04112016103207668  
DOI:  10.7907/B8K2V070  
Default Usage Policy:  No commercial reproduction, distribution, display or performance rights in this work are provided.  
ID Code:  9669  
Collection:  CaltechTHESIS  
Deposited By:  Leslie Granillo  
Deposited On:  12 Apr 2016 15:14  
Last Modified:  20 Dec 2019 19:53 
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