Temperature dependence of Nuclear Magnetic Resonance (NMR) chemical shifts and longitudinal and transverse relaxation times (T₁ and T₂) was studied for the pyrrole protons in a number of six-coordinate S = 1/2 iron(III) tetraphenylporphyrin (TPP) and tetramesitylporphyrin (TMP) complexes in the temperature range 190--310 K. In all complexes, temperature behavior of the chemical shifts and relaxation times is consistent with the presence of a low spin - high spin exchange caused by the dissociation of one axial ligand. In symmetric sterically hindered complexes, cyclic exchange induced by the synchronous rotation of axial ligands is also present. In all complexes, T₂s are considerably shorter than T₁s. Relaxation times in the TMP complexes are generally longer than corresponding values for the TPP complexes. Estimate of the electronic T₁ is given and mechanisms of nuclear relaxation are discussed. The rate of NOE buildup for a pair of pyrrole protons in [TMPFe(2-MeImH)₂]⁺ was measured; it is consistent with the Stokes rotational correlation time. A method is proposed to predict the detectability and optimum detection conditions of NOE between a pair of structurally rigid protons in similar complexes. Contrary to previous studies, no NOE is detected between pyrrole protons of two unsymmetrically substituted bis-N-methylimidazole Fe(III) TPP complexes. Two NMR approaches were utilized to measure the rate constant of axial ligand rotation in the TMP complex. Saturation transfer measurements yield overestimated rate constant. The measurement based on the temperature dependence of the T₂s(ΔH‡ = 48 ± 1 kJ/mol, ΔS‡ = -10 ± 6 J/K · mol) is consistent with previous studies. Modified MM2 potentials were also used to study the rotation of axial ligands in [TMPFe(1,2-Me₂Im)₂]⁺ and [TPPFe(1-MeIm)₂]⁺. Adiabatic potential energy surfaces (PES) for rotation of axial ligands were constructed for both complexes. Synchronous rotation of the axial ligands (ΔH‡ = 48 kJ/mol) is highly preferable in the TMP complex. For the TPP complex, the enthalpy barriers to synchronous and asynchronous rotation are 3.3 and 5.4 kJ/mol, respectively. The relationship between the orientation of axial ligands, distortion of metalloporphyrin core from planarity, and the bulkiness of axial ligands and porphyrin substituents is discussed.

There has been much interest in the last five or ten years in supercritical fluid extraction. In addition to the fact that some supercritical fluids may be less harmful to the environment than traditional extraction solvents, claims have been made for the superior extraction capabilities of supercritical fluids. In a few cases concentrations from absorbance measurements in the supercritical have been calculated with absorptivities derived from studies in liquid systems. This study suggests that the molar absorptivity in the supercritical may be quite different from that in a liquid system. The Beer's Law analysis done here was not adaquate to determine the absolute molar absorptivities in the system being examined, anthracene in carbon dioxide. This failure is in large part due, however, to the relative crudeness of the equipment and procedure used. While failing in the quantitative analysis, a use of Beer's Law in a qualitative capacity may be warranted. The analysis does succeed as an indicator of changes in molecular behavior that occur not only between liquid and high-pressure systems but also those, much slighter, that occur between high-pressure liquid and supercritical fluid systems.

CaOH and CaOD were studied in the gas phase using dye laser spectroscopy. The molecules were produced in a Broida-type oven. Laser excitation spectroscopy was used to study the Ḃ²Σ⁺-X²Σ⁺ transition of CaOD near 5500 Å. The 000-000 band was rotationally analyzed and r₀ structures were established for both states. Like other alkaline earth monohydroxides, CaOD is a linear molecule. For the Ḃ²Σ⁺ state the following bond lengths were found: r(Ca-O) = 1.9697Å and r(O-H) = 0.9179Å, while for the X²Σ⁺ state, r(Ca-O) = 1.9849 and r(O-H) = 0.9207Å. Optical-optical double resonance (OODR) was used to investigate the upper electronic states of CaOH. A ²Π electronic state and three ²Σ vibronic states were observed for the first time in the region 2990 - 3070 Å. For the ²Π state the rotational constant, B°, and the band origin energy, T₀, were calculated: B° = 0.347 cm⁻¹ and T = 32360 cm⁻¹.

The translational-rotovibronic Hamiltonian for a polyatomic molecule is derived by using the Schrodinger equation in tensor form and employing the Eckart conditions (determining the nuclear-framework rotational variables). The present derivation is a unified comprehensive one by a quantum-mechanical pathway and contrasts with fragmentary previous derivations via a classical-intermediate path. The method presented affords a firm conceptual picture of the nature of the transformation and the origin of coupling terms, and avoids mathematical complexities with their residue of obscurity. The Hamiltonian for the linear molecule compared with that for the non-linear molecule differs significantly in the coupling terms, in the rotational kinetic energy term and in the U(Q) term (Watson term), which is found to be non-zero in the linear case, in contrast to previous literature. The correct form of the total angular momentum operators is also derived quantum-mechanically. / Source: Dissertation Abstracts International, Volume: 43-02, Section: B, page: 0436. / Thesis (Ph.D.)--The Florida State University, 1982.

Fractions of both linear polyethylene and ethylene-butene copolymers were found to form thermally reversible gels when crystallized from quiescent p-xylene solutions. For linear polyethylene, gels were observed over the molecular weight range from 1.26 x 10('3) to 1.62 x 10('6). The maximum polymer concentration required for gelation to occur was found to depend on the molecular weight and the crystallization temperature. For linear polyethylene solutions cooled rapidly to 22(DEGREES)C, this concentration was found to range from 2.0% (wt./vol.) for the low molecular weight fractions to 0.3% for the highest molecular weight. The concentration required for gelation to occur was found to increase greatly for crystallization at 86(DEGREES). Linear polyethylene fractions were observed to form gels at substantially lower concentrations than ethylenebutene copolymer fractions of comparable molecular weight. / Studies of the crystallite thickness and accompanying thermodynamic properties demonstrated that the gels were composed of lamellar crystallites very similar in nature to those shown to be characteristic of crystallization from dilute solutions (0.08%). / Polarized light microscopy studies revealed in all the gels studied large supermolecular structures up to 100 microns in length. The concentration where adjacent supermolecular structures begin to exhibit substantial overlap was found to correspond to the minimum concentration required for gel formation. These morphological studies of ethylene-butene copolymers and linear polyethylene fractions when crystallized from relatively dilute solutions were shown to provide interesting parallels with similar studies on bulk crystallized samples. / In conclusion, this work showed thermally reversible gelation to be a more general aspect of polymer crystallization than had been thought previously. / Source: Dissertation Abstracts International, Volume: 42-10, Section: B, page: 4077. / Thesis (Ph.D.)--The Florida State University, 1981.

The Hiller-Sucher-Feinberg (HSF) identity for matrix elements of Dirac's delta-function is used to obtain an alternative equation for the electron density. Asymptotics of the HSF electron density are derived; the HSF density obeys a relationship analogous to Kato's cusp condition, and decays to a constant if the sum of approximate Hellmann-Feynman forces is finite. The HSF molecular integrals, ${\cal L},{\cal U}$ and ${\cal V}$, involving s-type Gaussian basis functions are derived. Formulae that yield optimal quadrature parameters for the numerical integration of the ${\cal U}$ and ${\cal V}$ integrals are developed. An analytic component, corresponding to Rosser's rocket flight function, $\int\sbsp{0}{a} {e\sp{-bt}\over 1+2t\sp2} dt$, is extracted from the ${\cal V}$ integral, and novel methods for its computation are presented. M scATHEMATICA programs that calculate accurate and efficient approximates of special functions are listed, including rational approximates with expanding interpolation grids. These developments are implemented in scRHODOS, which runs at sustained rates of 120 MFLOPS on a single, Cray YMP CPU. Results obtained with scRHODOS demonstrate that the HSF density is an order of magnitude more accurate than the conventional density at the nuclei of heavy atoms, but is less accurate at hydrogen nuclei bound to heavy atoms due to its improper decay. The constrained-variational method is developed to eliminate Hellmann-Feynman forces; application of this method increases the accuracy of the HSF density at hydrogen nuclei dramatically. In the case of the di-lithium molecule, the electron density and its topological properties converge more rapidly when derived from the HSF identity. / Source: Dissertation Abstracts International, Volume: 55-04, Section: B, page: 1449. / Major Professor: Jerzy Cioslowski. / Thesis (Ph.D.)--The Florida State University, 1994.

The Marangoni (surface-tension-induced) instability of surfactant-containing lenses of paraffin oil was investigated experimentally in the first part of this work. Results of these experiments are described and qualitative explanations are proposed. An unsuccessful attempt was made to quantitatively model a simple case of instability. / Attention was then shifted to the instability at a plane interface between two immiscible fluids, each containing a surface-active solute. The literature on this instability is reviewed and a simple finite-layer model is developed and subjected to a linear stability analysis. The mathematical structure and results of this analysis were used as tools in disclosing the physical mechanisms that underlie the onset of convective flow. It was found that the growth or decay of a normal-mode disturbance depends upon the relative rates of transport of momentum and solute in ways more subtle than have been recognized heretofore. In addition, the wave-number of the dominant mode was found to be determined primarily by the efficiency of solute transport, rather than by factors related to viscous dissipation. / The mathematical apparatus of the model was then used to elucidate the mechanism of conversion of chemical potential energy to kinetic energy. It was found that this connection cannot be made unless the surface excess concentration is explicitly included in the model. It is the convective transport of excess solute down chemical potential gradients in the interfacial plane that accounts for the conversion of chemical to kinetic energy. Use of the Gibbs adsorption equation allows this relation to be demonstrated quite simply. / The model was used in a global thermodynamic analysis to show that a convecting system does correspond to a process with less entropy production than a quiescent, diffusing system, at least for marginally supercritical values of the Marangoni number. This result follows because the generation of kinetic energy occurs at the expense of diffusive dissipation, while the net boundary fluxes are unchanged by convection. / A model for Marangoni instability at a cylindrical interface is developed in an Appendix. / Source: Dissertation Abstracts International, Volume: 44-02, Section: B, page: 0509. / Thesis (Ph.D.)--The Florida State University, 1983.

The kinetics of the isothermal decomposition of a series of compounds are studied using electron paramagnetic resonance spectroscopy. The general formula for the compounds under investigation is the guest chromophore, {Cr(NH(,3))(,5)X}('2+) doped into the isomorphous host material, {M(NH(,3))(,5)Y}Z(,2), where X = Cl or Br, M = Co or Rh, Y = Cl or Br, and Z = Cl('-), Br('-), I('-), N(,3)('-), or NO(,3)('-). All of the investigated displayed first order kinetics and excellent adherence to the Arrhenius law. The observations, including the activation energies and frequency factors, are presented for each system. Also displayed are the Arrhenius diagrams for each decomposition as well as pre- and post-reaction spectra. Several trends emerge from the data and these are discussed and possible explanations of the observables are offered. Lastly, several possible avenues of continued endeavor are suggested. / Source: Dissertation Abstracts International, Volume: 45-09, Section: B, page: 2929. / Thesis (Ph.D.)--The Florida State University, 1984.

An expression is derived for the charge density susceptibility which, under the Unsold approximations, reduces to the Fourier transforms of electron density functions. When considering uncorrelated wavefunctions, the susceptibility is given simply by static form factors in terms of which the second order Coulomb energy may be calculated. This is equivalent to applying the Unsold approximations directly unto the second order Coulomb energy expression in the usual time independent Rayleigh-Schrodinger perturbation theory. / Using the interactions of hydrogen-hydrogen and helium-helium diatoms as test cases, we evaluated numerically and analytically the various integrals for their second order dispersion energies. The two approaches differ in that while the latter requires analytic form factors, the former can use both analytic as well as the readily available tabulated form factors. Their results are found to be in excellent agreements. / Appropriate choices for the Unsold average excitation energy are made to put the values of the dispersion energy on an absolute scale. Precise potentials at large separations are obtained. By adding to our dispersion energy the first order Coulomb, exchange and second order induction contributions, the whole potential curves too agree remarkably well with previous accurate results. / The present treatment allows the use of the full Coulomb potential without recourse to the multipole expansion. In addition, the formulation in momentum space affords considerable mathematical simplification. / Source: Dissertation Abstracts International, Volume: 42-06, Section: B, page: 2392. / Thesis (Ph.D.)--The Florida State University, 1981.

7-Azaindole is a molecule which undergoes excited-state proton-transfer in alcohol solvents (12). Tautomer luminescence arises from double-proton-transfer in a cyclical hydrogen-bonded complex between 7-azaindole and one alcohol molecule. The lack of 7-azaindole tautomer luminescence in water solvents is thought to be unusual since alcohol and water are both hydroxyllic solvents. We have shown that tautomer fluorescence can be detected in ether solutions that have been saturated with water. The position of the fluorescence is identical to that in ethanol. The formation of the hydrogen-bonded 7-azaindole complex in dilute water solutions has been attributed to the presence of monomer and small clusters of water molecules in these dilute solutions. In liquid water 7-azaindole cannot effectively compete with the extended network of water hydrogen bonds for monomeric water, and excited-state proton-transfer cannot occur. / We also have proposed that the excited 7-azaindole can form an exciplex with one alcohol molecule. This exciplex is directly analogous to the indole:alcohol exciplex (33) in a number of ways. Dramatic quenching of the exciplex luminescence can be explained by postulating the ejection of an electron by the exciplex upon deactivation. We have found luminescence yield effects and picosecond lifetime dependences on the acidity and state of aggregation of the alcohol which support this hypothesis. A deuterium isotope effect also has been observed. / 3-Hydroxyflavone can undergo intramolecular excited-state proton-transfer in hydrocarbon solvents. 5-Hydroxyflavone, however, exhibits no luminescence under similar conditions. An investigation of the extinction coefficients of these molecules and flavone, in addition to their luminescence properties and resonance Raman spectra, has allowed us to propose that in hydrocarbon solvents, the ('1)n, (pi)* state is lowest in flavone, the ('1)n, (pi)* state and the ('1)(pi), (pi)* state are degenerate in 5-hydroxyflavone, and that the ('1)(pi), (pi)* is lowest in 3-hydroxyflavone. The consequence of the degeneracy of the first two excited states in 5-hydroxyflavone results in a pseudo Jahn-Teller Splitting and rapid radiationless transition to the ground state. / Source: Dissertation Abstracts International, Volume: 42-10, Section: B, page: 4076. / Thesis (Ph.D.)--The Florida State University, 1981.