Chemistry Commons^™

Studies Of Radiation Effects In Three High Polymers, Heidi Rene-Mitchell Ries

Physics Theses & Dissertations

Three high polymers, Mylar®, Ultem®, and Kapton®, were irradiated to total doses of 1, 5, and 9.5 gigarad using 1-MeV electrons. The glass transition temperatures (T_g) of the materials before and after irradiation were measured using an AC electrical dissipation factor technique. From the T_g data, it was found that the electron radiation at these total doses results in net chain scissioning in Mylar and net crosslinking in Ultem, while self-mending is predominant in Kapton. The dielectric constant was measured before and after irradiation, but no significant changes due to irradiation were observed. Electron paramagnetic resonance (EPR) …

The Aperiodic Crystal Picture And Free Energy Barriers In Glasses, Randall W. Hall, Peter G. Wolynes

Collected Faculty Scholarship

The aperiodic crystal picture associates the glass transition with freezing into a nonperiodic structure. Dynamics in the glassy state involves activated jumps between different aperiodic free energy minima. Activation barriers may be estimated through the use of freezing theory and the theory of dense solids. The results resemble, but are distinct from, free volume theory. Reasonable fits to experimental data are obtained.

Determination Of Dissociation Energies And Thermal Functions Of Hydrogen‐Bond Formation Using High Resolution Ftir Spectroscopy, B. A. Wofford, M. E. Eliades, Shannon Lieb, J. W. Bevan

Scholarship and Professional Work - LAS

A technique which employs high resolution Fourier transform infrared spectroscopy is demonstrated for evaluation of hydrogen bonddissociation energiesD ₀ and D _e . Results for HCN‐‐HF give a D ₀=20.77(22) and D _e =28.77(45) kJ/mol which are compared with previously determined values obtained from microwave absolute intensity measurements and a b i n i t i o molecular orbital calculations. Rovibrational band information available for HCN‐‐HF also permits evaluation of thermal functions of dimer formation in kJ/mol: ΔU ^○ _298.2 =20.1(2), ΔH ^○ _298.2 =22.6(2), ΔG ^○ _298.2 =59.4(2), ΔS ^○ _298.2 =−0.1235.

Molecular Dynamics In Hydrogen‐Bonded Interactions: A Preliminary Experimentally Determined Harmonic Stretching Force Field For Hcn‐‐‐Hf, B. A. Wofford, Shannon Lieb, J. W. Bevan

Scholarship and Professional Work - LAS

Observation of the 2ν₁ overtone band in the hydrogen‐bonded complex HCN‐‐‐HF permits evaluation of the anharmonicity constant X _{1 1}=−116.9(1) cm^{− 1} and determination of the anharmonicity corrected fundamental frequency ω₁. This information, and available data from previous rovibrational analyses in the common and perdeuterated isotopic species of HCN‐‐‐HF, offer an opportunity for calculation of an approximate stretching harmonic force field. With the assumptions f _{1 2}=f _{2 4}=0.0, the remaining force constants (in mdyn/Å) are evaluated as: f _{1 1}=8.600(20), f _{2 2}=6.228(9), f _{3 3}=19.115(40), f _{4 …}

Measurement Of The Condensation Coefficient Of Water In The Umr Simulation Chamber, Daniel R. White, James L. Kassner, John C. Carstens, Donald E. Hagen, John L. Schmitt, Darryl J. Alofs, Alfred R. Hopkins, Max B. Trueblood, Max W. Alcorn, William L. Walker

Physics Faculty Research & Creative Works

The UMR Cloud Simulation Facility is described. The facility is designed to provide a controlled environment simulating the conditions of natural atmospheric processes. It consists of two cooled-wall expansion cloud chambers and peripheral instrumentation for generation and characterization of aerosols used for cloud formation studies. Results of initial studies of the growth of warm cloud droplets and inferred measurements of the condensation coefficient are described.

A Mössbauer Effect Study Of The Structural And Magnetic Properties Of Y₂(Fe₁₋ₓalₓ)₁₄B, Ying-Chang Yang, Dwayne E. Tharp, Gary J. Long, Oran Allan Pringle, William Joseph James

Chemistry Faculty Research & Creative Works

The crystallographic and magnetic properties of Y₂(Fe₁₋ₓAlₓ)₁₄B, where x equals 0.00, 0.02, 0.04, 0.06, and 0.08, have been investigated by Mössbauer spectroscopy and magnetic measurements at room temperature and 85 K. Magnetic anisotropy and magnetization changes with aluminum substitution indicate that, because of size, the aluminum preferentially occupies the j₂ site over the remaining five crystallographically nonequivalent iron sites. This preferential occupation has been confirmed by Mössbauer spectral studies, which indicate that the compositional variation of the hyperfine field for each site is related to the number of near-neighbor aluminum atoms for the site. This compositional variation is helpful in …

28th Rocky Mountain Conference

Rocky Mountain Conference on Magnetic Resonance

Program and abstracts from the 28th annual meeting of the Rocky Mountain Conference, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, August 3-7, 1986.

Mössbauer Spectroscopic Studies Of Hemoglobin And Its Isolated Subunits, G. R. Hoy, D. C. Cook, R. L. Berger, F. K. Friedman

Physics Faculty Publications

Samples of 90% enriched ⁵⁷Fe hemoglobin and its isolated subunits have been prepared. Mössbauer spectroscopic measurements have been made on three such samples. Sample one contained contributions of oxyhemoglobin, deoxyhemoglobin, and carbonmonoxyhemoglobin. This sample was studied from a temperature of 90 K down to 230 mK. Measurements were also made at 4.2 K using a small applied magnetic field of 1.0 T. In general, the measured quadrupole splittings and isomer shifts for each component agreed with previous measurements on single component samples in the literature, and thus demonstrated that chemically enriched hemoglobin has not been altered. The second and …

Laser Pump And Probe Excited State Absorption Measurements, Shawpin Jong

Electrical & Computer Engineering Theses & Dissertations

A pump and probe technique was used to investigate triplet-triplet excited state absorption in solutions of the scintillators 2,5 diphenyloxazole (PPO) and 2,1 naphthyl,5 phenylzole (a-NPO) in several solvents.

KrF excimer radiation (248 nm) was used to pump the samples under investigation as well as a tunable dye laser which was used as the probe. Time-resolution was obtained by changing the optical path difference between the pump and probe beams.

Transient excited state absorption was measured in a wide spectral region between 330 nm and 600 nm, showing a peak at 400 nm for PPO solutions, and two …

Nonadiabatic Theory Of Fine-Structure Branching Cross Sections For Na-He, Na-Ne, And Na-Ar Optical Collisions, Linda L. Vahala, P. S. Julienne, Mark D. Havey

Electrical & Computer Engineering Faculty Publications

The nonadiabatic close-coupled theory of atomic collisions in a radiation field is generalized to include electron spin and is used to consider the weak-field Na–rare-gas (RG) optical collision Na(²S_1/2)+RG+nhν μNa(²P_j)+RG+(n-1)hν. The effects of detuning and incident energy on the branching into the atomic Na 3p²P_3/2 and 3p²P_1/2 states are examined. The cross sections σ(j) are found to have a strong asymmetry between red and blue detuning as well as a complex threshold and resonance structure dependence on energy. A partial cross-section analysis …

The Design And Construction Of Microprocessor-Computer Controlled Rapid Scanning Fiberoptic Spectrophotometer, Kathleen Marie Tobin

Masters Theses

Conventional spectrophometers require the transfer of a sample to a cuvette for obtaining spectra. The measurement of absorbance in situ can be accomplished using a fiber optic probe which can be placed directly in the sample. The fiber optic probe also minimizes environmental factors such as thermal or vibrational which may affect the absorbing species. A rapid scanning speed allows for essentially simultaneous wavelength monitoring.

The effect of coupling a rapid scanning spectrophotometer with a fiber optic probe provides for an extremely versatile system. When used in comjunction with a microprocessor or computer, this approach offers advantages such as data …

27th Rocky Mountain Conference

Rocky Mountain Conference on Magnetic Resonance

Program and abstracts from the 27th annual meeting of the Rocky Mountain Conference, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, July 14-18, 1985.

26th Rocky Mountain Conference

Rocky Mountain Conference on Magnetic Resonance

Program and abstracts from the 26th annual meeting of the Rocky Mountain Conference, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, August 7-8, 1984.

25th Rocky Mountain Conference

Rocky Mountain Conference on Magnetic Resonance

Abstracts and meeting program from the 25th annual meeting of the Rocky Mountain Conference, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, August 14-17, 1983.

Preliminary Rovibrational Analysis Of The Nν6+Ν1−Nν6 Vibration In Hcn⋅⋅⋅Hf, E. Kyrö, K. Mcmillan, M. Eliades, D. Danzeiser, P. Shoja-Chaghervand, Shannon Lieb, J. W. Bevan

Scholarship and Professional Work - LAS

A preliminary rotation‐vibration analysis of the n=0 and n=1 subbands associated with the nν₆+ν₁−nν₆ hydrogen‐bonded vibration in HCN⋅⋅⋅HF has been completed. The following excited staterotational constantsB′ and band origin frequencies ν₀ have been determined for the complex. The results are consistent with a rotation‐vibration interaction constant α₁=−68.3±1 MHz which correlates with an excited stater(N⋅⋅⋅F) internuclear distance of 2.762 Å, a decrease of 0.034 Å relative to the ground state.Excited state lifetimes associated with assigned transitions are demonstrated to be …

Intermolecular Interactions For Phosphatidyl Choline And Phosphatidyl Ethanolamine, Tony Flaim, Stig Friberg, Patricia L.M. Plummer

Chemistry Faculty Research & Creative Works

Intermolecular interaction between pairs of methylphosphocholine (MPC) and methylphosphoethanolamine were calculated using an extended CNDO/2 program. Experimentally determined conformations were used for the ethanolamine and choline groups. In the methylphosphocholine the major interaction was intramolecular, involving the phosphate ester-choline groups, while in the ethanolamine the maximum attraction was intermolecular between the ethanolamine and the phophate ester of a neighboring molecule(s). © 1983.

Thermal Decomposition Kinetics Of Iodine‐Doped Polyacetylene In Vacuum, J. ‐E Osterholm, H. Yasuda, L. L. Levenson

Physics Faculty Research & Creative Works

The thermal stability of iodine‐doped polyacetylene films, (CHIy)x, has been studied by means of electrical conductivity measurements, measurements on weight loss, and mass spectrometric analysis of desorbing species. When heated between room temperature and 125°C in vacuum, these films proved to be of poor thermal stability, being unstable at temperatures above 20°C. During the thermal treatments, molecular iodine desorbs from the films, resulting in an appreciable dopant weight loss with accompanying decrease in the electrical conductivity. The decomposition process does not follow simple kinetics. Copyright © 1983 John Wiley & Sons, Inc.

24th Rocky Mountain Conference

Rocky Mountain Conference on Magnetic Resonance

Abstracts and meeting program from the 24th annual meeting of the Rocky Mountain Conference, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, August 1-5, 1982.

Travelling-Wave Sub-Doppler Excited Molecule Energy Transfer Spectroscopy, Khalid Iqbal, Shannon G. Lieb, J. W. Bevan

Scholarship and Professional Work - LAS

A general formulation of traveling‐wave sub‐Doppler excited molecule energy transferspectroscopy is presented. The line profile analysis is applied to that determined experimentally for the R(22) ν3 HCN transition. Pn the noise equivalent power of the detector is demonstrated to be ⩽10−12 W. Finally, the technique is applied to resolve the KsR(7) ν1 transition head in NH3.

A Laser Interferometric Study Of Electric Field Effects On Methane-Oxygen Flame Plasmas, Mark D. Prairie

Masters Theses

A laser interferometer is developed to study the refractive index field, aerodynamic structure, and three dimensional temperature profile of a methane-oxygen flame system under the influence of D.C. electric fields. A combined graphical-numerical method is used to transform the observed interference patterns into radial temperature distributions. The results indicate that the electric field exerts a marked influence on the flame stability, geometry, and charged particle flow. Experimental evidence shows that these effects are most apparent under fuel rich conditions. It is suggested an electric field may change the concentration gradients of reacting species, leading to an altered course of fuel …

A Study Of Poly(P‐Xylylene)‐Coated Asf5‐Doped Polyacetylene, J. E. Osterholm, H. Yasuda, L. L. Levenson

Physics Faculty Research & Creative Works

Electrical conductivity measurements and scanning electron microscopy have been used to study uncoated and poly(p‐xylylene)‐coated samples of polyacetylene doped with AsF5. These initial results indicate a considerable reduction in the decay rate of conductivity in the presence of oxygen as well as a decreased rate of thermal decomposition of the dopant when heated between 50°C and 115°C in vacuum by the coating. Copyright © 1982 John Wiley & Sons, Inc.

Picosecond Laser Pulse Irradiation Of Crystalline Silicon, K. L. Merkle, H. Baumgart, R.H. Uebbing, F. Phillipp

Electrical & Computer Engineering Faculty Publications

Morphology changes introduced by picosecond laser pulses at λ = 532 nm and 355 nm in (111) and (100) silicon samples are studied by means of optical and high-voltage electron microscopy. Depending on energy fluence, orientation and wavelength, amorphous or highly defective regions may be created. From an analysis of damage thresholds and damage depth distributions it is concluded that melting and energy confinement precedes the formation of the structural changes.

23rd Rocky Mountain Conference

Rocky Mountain Conference on Magnetic Resonance

Abstracts and meeting program from the 23rd annual meeting of the Rocky Mountain Conference, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, August 2-6, 1981.

Thermal Decomposition Kinetics Of Asf5-Doped Polyacetylene In Vacuum, T. Inoue, J. E. Osterholm, H. Yasuda, L. L. Levenson

Physics Faculty Research & Creative Works

Electrical conductivity measurements, mass spectra of desorbing species, and ESCA surface analysis are reported for AsF5-doped polyacetylene heated between 50 and 130°C in vacuum. All measurements indicate first-order decomposition kinetics with activation energies between 13 and 20 kcal mole-1. Decomposition leads to the desorption of AsF3 and F2. Metallic arsenic remains in the polyacetylene as a decomposition by-product.

22nd Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Abstracts and meeting program from the 22nd annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, August 10-14, 1980.

Pressure Dependence Of Fluorescent And Photolytic Interferences In Ho Detection By Laser-Excited Fluorescence, Thomas M. Hard, Robert J. O'Brien, T. B. Cook

Chemistry Faculty Publications and Presentations

In the measurement of HO concentrations by laser-excited fluorescence, expansion of the sampled air offers a way to reduce fluorescent and photolytic interference by other species. The decrease in [HO] upon expansion is balanced by an increase in HO fluorescence yield over a wide range of pressures. Background air fluorescence is reduced if the responsible species have fluorescence yields higher than those of HO. Preliminary experiments indicate that most of the fluorescence observed in laboratory air is due to such species. Upon expansion, the suppression of fluorescent interference can be no greater than the reduction in pressure, whereas the suppression …

Influence Of Las Vegas Wash Density Current On Nutrient Availability And Phytoplankton Growth In Lake Mead, John R. Baker, Larry J. Paulson

Publications (WR)

Density currents are commonly formed in reservoirs because of temperature or salinity induced density differences between inflowing and receiving waters. Anderson and Pritchard (1951) were among the first to demonstrate this in their investigations of density currents in Lake Mead. They found that the Colorado River formed an underflow in Lake Mead during the winter, an overflow in the spring and an interflow in the summer and fall. Wunderlich and Elder (1973) have since described the hydromechanics of these types of flow patterns, and density currents have been reported for several other large reservoirs (Carmack et al. 1979, Johnson and …

Studies Of The Reorientational Relaxation Of Pyridine In Water By Depolarized Rayleigh Light Scattering, C. H. Wang, Scott L. Whittenburg, P. A. Lund, D. H. Christensen

Chemistry and Biochemistry Faculty Publications

The depolarized Rayleigh spectra of aqueous solutions of pyridine have been studied using a high‐finesse Fabry–Perot interferometer as a function of temperature and concentration. The Rayleigh relaxation times are found to have a complex concentration and viscosity dependence. The classical Stokes–Einstein–Debye equation for molecular reorientation breaks down in this system. The Rayleigh relaxation time of pyridine molecules is not determined by the macroscopic shear viscosity of the solution. The specific interaction due to the formation of hydrogen bonds between pyridine and water molecules plays a very important role in affecting the relaxation time. At a fixed temperature the plot of …

21st Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Abstracts and meeting program from the 21st annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Rocky Mountain Section of the Society for Applied Spectroscopy and the Rocky Mountain Chromatography Discussion Group. Held in Denver, Colorado, July 30 - August 1, 1979.

Cndo Calculations On The Structure Of A Liquid Sodium Carboxylate-Carboxylic Acid Compound, Beverly Bendiksen, Stig Friberg, Patricia L.M. Plummer

Chemistry Faculty Research & Creative Works

The molecular interactions in a carboxylic acid/sodium carboxylate compound which is a liquid at room temperature were calculated using a CNDO/2 approach. The calculations gave results distinguishing the energy for different conformations in the molecular compound. The maximum binding energy was found for a structure in which the four acids were bridging with a hydrogen bond from the acid OH group to the carboxylate group and the acid carbonyl groups forming a ligand bond to the carboxylate sodium ion. © 1979 Academic Press, Inc.