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Articles 35011 - 35040 of 36534

Full-Text Articles in Physical Sciences and Mathematics

He+ Lamb-Shift Measurement By The Quenching-Radiation Anisotropy Method, Gordon W. F. Drake, S. P. Goldman, A. Van Wijngaarden Jan 1979

He+ Lamb-Shift Measurement By The Quenching-Radiation Anisotropy Method, Gordon W. F. Drake, S. P. Goldman, A. Van Wijngaarden

Physics Publications

The Lamb shift of He+ is derived from the measured anisotropy in the electric-field-induced quenching radiation of the metastable 2s12 state. The results demonstrate that the anisotropy method can be applied with high precision to one-electron ion beams, as well as neutral beams. We find a Lamb shift of 14040.22.9 MHz (1 standard deviation). The sources of error and difficulties encountered in working with ion beams are discussed in detail. © 1979 The American Physical Society.

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Unified Relativistic Theory For 1s2p P13-1s2 S01 And 1s2p P11-1s2 S01 Frequencies And Transition Rates In Heliumlike Ions, Gordon W. F. Drake Jan 1979

Unified Relativistic Theory For 1s2p P13-1s2 S01 And 1s2p P11-1s2 S01 Frequencies And Transition Rates In Heliumlike Ions, Gordon W. F. Drake

Physics Publications

The aim of this paper is to test a simple method for converting accurate nonrelativistic predictions of atomic properties into accurate relativistic predictions with a minimum of additional computational effort. The method connects smoothly the exact nonrelativistic LS-coupling results appropriate at small Z with the relativistic jj-coupling results appropriate at large Z. For the processes stated in the title, the method appears to offer a significant improvement in accuracy over relativistic Hartree-Fock or random-phase- approximation calculations, particularly in the low and intermediate range of nuclear charge. For large Z, the present results agree well with the relativistic random-phase approximation. © …

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Energy And Angular Distributions Of Secondary Electrons From 5-100-Kev-Proton Collisions With Hydrogen And Nitrogen Molecules, M. Eugene Rudd Jan 1979

Energy And Angular Distributions Of Secondary Electrons From 5-100-Kev-Proton Collisions With Hydrogen And Nitrogen Molecules, M. Eugene Rudd

M. Eugene Rudd Publications

Cross sections for the ejection of electrons from hydrogen and nitrogen by protons have been measured as a function of the energy and angle of ejection of the electrons at incident proton energies of 5-70 keV and 100 keV for hydrogen. The range of angles measured was 10-160° and the electron energy range was 1.5-300 eV. The doubly differential cross sections were also integrated over angle, over electron energy, or over both to obtain singly differential and total cross sections for electron production. Average electron energies were also calculated from the data. The angular distributions of electrons are peaked in …

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Temperature Dependent Spatial Order In Superfluid And Normal 4he, Robert Hallock, H. N. Robkoff, D. A. Ewen Jan 1979

Temperature Dependent Spatial Order In Superfluid And Normal 4he, Robert Hallock, H. N. Robkoff, D. A. Ewen

Robert Hallock

Measurements of the structure factor S(k) for 4He at constant density above and below Tλ are reported. The results show a clear loss of spatial order on cooling through Tλ. Application of the theory of Cummings, Hyland, and Rowlands to the data allows a measurement of the condensate fraction for He II.

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Behavior Of Persistent Currents Under Conditions Of Strong Decay, Robert Hallock, D. T. Ekholm Jan 1979

Behavior Of Persistent Currents Under Conditions Of Strong Decay, Robert Hallock, D. T. Ekholm

Robert Hallock

We report observations of the decay of persistent currents of thin superfluid 4He films for which the superfluid velocity deviates strongly from the previously observed logt behavior. We present data which document the evolution of this behavior as a function of film thickness. The Iordanskii-Langer-Fisher theory does not accurately describe our observation

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Electronic Structure Calculation Of Icosahedral B-12, R. P. Wagner, Gust Bambakidis Jan 1979

Electronic Structure Calculation Of Icosahedral B-12, R. P. Wagner, Gust Bambakidis

Physics Faculty Publications

No abstract provided.

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Ionization, Luminosity, And Heating Of The Upper Atmosphere Of Mars, Jane L. Fox, Alexander Dalgarno Jan 1979

Ionization, Luminosity, And Heating Of The Upper Atmosphere Of Mars, Jane L. Fox, Alexander Dalgarno

Physics Faculty Publications

A model based upon Viking data is constructed of the Martian atmosphere, and a comprehensive quantitative discussion is given of the measurements of the ultraviolet dayglow. A detailed assessment is made of the heating of the neutral and ionized components of the atmosphere arising from the absorption of ultraviolet solar radiation.

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Dissociative Excitation Of Hgbr2 In Collisions With A Beam Of Metastable Nitrogen, D. W. Fahey, Laird D. Schearer Jan 1979

Dissociative Excitation Of Hgbr2 In Collisions With A Beam Of Metastable Nitrogen, D. W. Fahey, Laird D. Schearer

Physics Faculty Research & Creative Works

No abstract provided.

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Negative Ion Production Rates In Rare Gas-Halide Lasers, Kaare J. Nygaard, Howard L. Brooks, Scott R. Hunter Jan 1979

Negative Ion Production Rates In Rare Gas-Halide Lasers, Kaare J. Nygaard, Howard L. Brooks, Scott R. Hunter

Physics Faculty Research & Creative Works

This paper reports on dissociative electron attachment in F2, NF3, Cl2, and I2. The principle of the method is to produce a short burst of photoelectrons from a photocathode by means of light from an argon-fluoride laser. Subsequently, by studying the motion of electrons and negative ions in a constant electric field (E) region, information is obtained about drift velocities and effective attachment cross sections. Helium, argon, and nitrogen were used as buffer gases. Of particular interest is a very strong temperature dependence of the attachment coefficient in I2. Measurements were taken from 35 to 110°C, covering an E/N range …

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Precision Doubly Differential Cross Section Measurements, John T. Park Jan 1979

Precision Doubly Differential Cross Section Measurements, John T. Park

Physics Faculty Research & Creative Works

Ion Energy Loss Spectrometry has been applied to the measurement of cross sections differential in both scattering angle and ion energy loss. Differential cross sections obtained for excitation of the n=2 level of atomic hydrogen by various ions provides unexpectedly good agreement with the available theories. Copyright © 1978 by The Institute of Electrical and Electronics Engineers, Inc.

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Nucleation Experiments With Monodisperse Nacl Aerosols., Darryl J. Alofs, M. B. Trueblood, D. R. White, V. L. Behr Jan 1979

Nucleation Experiments With Monodisperse Nacl Aerosols., Darryl J. Alofs, M. B. Trueblood, D. R. White, V. L. Behr

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Nucleation Experiments with Monodisperse NaCl Aerosols Showed Good Agreement with the Kohler Theory Relating the Critical Super-Saturation S//c to the Dry Size. Aerosols Produced by Condensing NaCl Showed the Same S//c as Those Produced by Evaporating Aqueous NaCl Solution Droplets. This Indicates that If There is an Energy Barrier in Going from a Dry NaCl Particle to a Solution Droplet, This Energy Barrier is Small. the Fact that the Evaporation Aerosol Particles Are Cubical Crystals and the Condensation Aerosols Are Amorphous Spheres is Shown to Make No Difference in the Nucleation Threshold. the Investigation Also Gives Insights into the Performance …

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Temperature Dependence Of The Electron Attachment Coefficient In Iodine, Howard L. Brooks, Scott R. Hunter, Kaare J. Nygaard Jan 1979

Temperature Dependence Of The Electron Attachment Coefficient In Iodine, Howard L. Brooks, Scott R. Hunter, Kaare J. Nygaard

Physics Faculty Research & Creative Works

The attachment coefficient for iodine in a (1% I2+99% N 2) mixture, 50 Torr total pressure, has been measured in an electron swarm experiment from 1 to 50 Townsends (1 Townsend=1Td=10-17 V cm2). As the temperature was increased from 35 to 110°C, the attachment coefficient increased for any E/N (electric field intensity/gas number density) values greater than 7 Td. These results are compared to other experimental data and an explanation for the temperature dependence, based on the population of upper vibrational states, is presented. © 1979 American Institute of Physics.

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Mechanism Of ¹⁴N(T,P) To The Ground State Quadruplet In ¹⁶N, H. T. Fortune, Oleksa-Myron Bilaniuk, G. Stephans, R. Middleton Jan 1979

Mechanism Of ¹⁴N(T,P) To The Ground State Quadruplet In ¹⁶N, H. T. Fortune, Oleksa-Myron Bilaniuk, G. Stephans, R. Middleton

Physics & Astronomy Faculty Works

Complete angular distributions (8°-168°) have been measured for the ¹⁴N(t,p)¹⁶N reaction, at a bombarding energy of 15 MeV, leading to the lowest four levels of ¹⁶N. Results have been analyzed using distorted-wave Born approximation and microscopic wave functions. The approximate magnitude of the compound-nucleus component has been extracted. NUCLEAR REACTION ¹⁴N(t,p), E=15 MeV; ¹⁶N levels, deduced reaction mechanism and tested shell-model wave functions. DWBA analysis.

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

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Electrical Resistivity Studies Of Order-Disorder Phenomena In V2h And V2d, Gust Bambakidis, M. W. Pershing, R. C. Bowman Jan 1979

Electrical Resistivity Studies Of Order-Disorder Phenomena In V2h And V2d, Gust Bambakidis, M. W. Pershing, R. C. Bowman

Physics Faculty Publications

No abstract provided.

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Excitation Of Cd, Zn, And Sr By A Beam Of Active Nitrogen, D. W. Fahey, William F. Parks, Laird D. Schearer Jan 1979

Excitation Of Cd, Zn, And Sr By A Beam Of Active Nitrogen, D. W. Fahey, William F. Parks, Laird D. Schearer

Physics Faculty Research & Creative Works

Excitation of the electronic levels of Cd, Zn, and Sr is observed when these metal vapors collide with a thermal-energy, active nitrogen beam. The beam is extracted from a glow discharge in pure N2. The active beam component is inferred to be vibrationally excited N2 in the A 3Σu+ electronic state. The absolute relative intensity of the emission lines in each element was measured. The excitation rates of the Cd and Zn target levels were found to depend exponentially on their energies indicating an effective temperature of approximately 4000°K. We believe that this temperature is related to the vibrational temperature …

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Distortion Isomerism In Ferrous Thiourea Complexes - Ii(1) Thermodynamics And Kinetics, R. Latorre, J. A. Costamagna, E. Frank, C. R. Abeledo, R. B. Frankel Jan 1979

Distortion Isomerism In Ferrous Thiourea Complexes - Ii(1) Thermodynamics And Kinetics, R. Latorre, J. A. Costamagna, E. Frank, C. R. Abeledo, R. B. Frankel

Physics

Mössbauer spectroscopy as a function of temperature of Fe(II)(N,N′-dicyclohexyl-thiourea)6(ClO4)2(FeDCTU) shows the existence of two isomeric forms A and B which coexist in the temperature range 200 < T < 300 K. The relative concentrations of A and B were studied as a function of time at different temperatures in the coexistence region. From the equilibrium constant as a function of temperature we obtain the following thermodynamic parameters: ΔH = −4520 ± 120 cal/mol and δS = 20 ± 0.1 e.u. The kinetics seem to follow an ordinary first order law but with an unusual temperature dependence of the rate constant k1. The results are discussed in terms of hydrogen bonded interactions between the perchlorate anions and the cyclohexylthiourea moieties.

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Ferromagnetism In Freshwater Bacteria, Richard P. Blakemore, Richard B. Frankel, Ralph S. Wolfe Jan 1979

Ferromagnetism In Freshwater Bacteria, Richard P. Blakemore, Richard B. Frankel, Ralph S. Wolfe

Physics

Magnetotactic bacteria isolated from swamp water were grown in pure culture in the laboratory. This newly isolated species was cultured in the magnetic and the nonmagnetic state. Magnetic cells, which were rich in iron, also produced particles similar to those found previously in other magnetic bacteria of marshes and bogs. By contrast, their nonmagnetic counterparts had much lower iron levels and lacked the crystal structures. Mossbauer spectroscopic analyses of whole cells of magnetic bacteria indicated that they contained the mineral magnetite.

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Semiclassical Calculations Of Vibrational Energy Levels For Non-Separable Systems Using The Birkhoff-Gustavson Normal Form, Randall T. Swimm, John B. Delos Jan 1979

Semiclassical Calculations Of Vibrational Energy Levels For Non-Separable Systems Using The Birkhoff-Gustavson Normal Form, Randall T. Swimm, John B. Delos

Arts & Sciences Articles

We present a semiclassical method of calculating vibrational energy levels for a system of nonseparable coupled oscillators. For a Hamiltonian written as a power series in which the leading terms are given by a sum of one‐dimensional harmonic oscillator Hamiltonians, the method involves transforming the original classical Hamiltonian via a succession of canonical transformations into a normal form which is a power series originally defined by Birkhoff and later generalized by Gustavson. Two cases are distinguished. If the harmonic oscillator frequencies in the unperturbed Hamiltonian are incommensurable, then the normal form is a power series whose terms are products of …

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The Modification And Use Of An Electron Paramagnetic Resonance Spectrometer For Data Collection At Liquid Nitrogen Temperature, Vernon Lee Baumberger Jan 1979

The Modification And Use Of An Electron Paramagnetic Resonance Spectrometer For Data Collection At Liquid Nitrogen Temperature, Vernon Lee Baumberger

Electronic Theses and Dissertations

The scope of this study includes the modification of an EPR spectrometer for acquisition of low temperature data. The modification involved adaptation of the system for use with a cylindrical cavity specifically designed for low temperature operation. This modification increased the capability of the present system for data collection at liquid nitrogen temperature and gave such greater stability than the rectangular cavity previously used. A comparison was made of signal to noise for the two cavities. This study showed a somewhat greater signal to noise ratio for the low temperature cylindrical cavity. Operation at low temperature also allowed the observation …

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Effect Of Displaced Geomagnetic And Geographic Poles On High-Latitude Plasma Convection And Ionospheric Depletions, Jan Josef Sojka, W. J. Raitt, Robert W. Schunk Jan 1979

Effect Of Displaced Geomagnetic And Geographic Poles On High-Latitude Plasma Convection And Ionospheric Depletions, Jan Josef Sojka, W. J. Raitt, Robert W. Schunk

All Physics Faculty Publications

We assumed that the ionospheric plasma at high latitudes has a tendency to corotate about the geographic pole and that magnetospheric convection is relative to the geomagnetic pole. With this assumption we calculated plasma drift patterns over the polar cap for a range of constant magnetospheric electric fields as well as for asymmetric electric fields with enhanced plasma flow on either the dawnside or the duskside of the polar cap. We calculated the drift patterns in both the geographic inertial and the geomagnetic inertial frame taking into account the displacement between the geographic and geomagnetic poles. We found that this …

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High Latitude Plasma Convection: Predictions For Eiscat And Sondre Stromfjord, Jan Josef Sojka, W. John Raitt, Robert W. Schunk Jan 1979

High Latitude Plasma Convection: Predictions For Eiscat And Sondre Stromfjord, Jan Josef Sojka, W. John Raitt, Robert W. Schunk

All Physics Faculty Publications

We have used a plasma convection model to predict diurnal patterns of horizontal drift velocities in the vicinity of the EISCAT incoherent scatter facility at Tromso, Norway and for Sondre Stromfjord, Greenland, a proposed new incoherent scatter facility site. The convection model includes the offset of 11.4° between the geographic and geomagnetic poles (northern hemisphere), the tendency of plasma to corotate about the geographic pole, and a magnetospheric electric field mapped to a circle about a center offset by 5° in the antisunward direction from the magnetic pole. Four different magnetospheric electric field configurations were considered, including a constant cross‐ …

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Equatorialelectric Fields During Magnetically Disturbed Conditions, 2. Implications Of Simultaneousauroral And Equatorial Measurements, C. A. Gonzales, M. C. Kelley, Bela G. Fejer, J. F. Vickrey, R. F. Woodman Jan 1979

Equatorialelectric Fields During Magnetically Disturbed Conditions, 2. Implications Of Simultaneousauroral And Equatorial Measurements, C. A. Gonzales, M. C. Kelley, Bela G. Fejer, J. F. Vickrey, R. F. Woodman

Bela G. Fejer

Simultaneous auroral and equatorial electric field data are used along with magnetic field data to study anomalous electric field patterns during disturbed times. During some substorms, accompanied by ring current activity, the worldwide equatorial zonal electric field component reverses from the normal pattern. This is interpreted as a partial closure of high latitude field aligned currents in the dayside, low latitude ionosphere. These currents flow westward across the dayside. In several cases the zonal equatorial electric field component was nearly identical in form to the zonal auroral component, indicating the close electrical coupling between these regions. Less certain, but equally …

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Laf3 Insulators For Mis Structures, A. Sher, W. E. Miller, Y. H. Tsuo, John A. Moriarty, R. K. Crouch, B. A. Seiber Jan 1979

Laf3 Insulators For Mis Structures, A. Sher, W. E. Miller, Y. H. Tsuo, John A. Moriarty, R. K. Crouch, B. A. Seiber

Physics Publications

Thin films of Laf3 deposited on Si or GaAs substrates have been observed to form blocking contacts with very high capacitances. This results in comparatively‐hysteresis‐free and sharpC‐V (capacitance‐voltage) characteristics for MIS structures. Such structures have been used to study the interface states of GaAs with increased resolution and to construct improved photocapacitive infrared detectors.

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Negative Ion Charge Transfer Of The Reaction Of S⁻ And O⁻ With Atomic Hydrogen Producing H⁻ Ions From 1500 To 10 Kev, George F. Hagner Jan 1979

Negative Ion Charge Transfer Of The Reaction Of S⁻ And O⁻ With Atomic Hydrogen Producing H⁻ Ions From 1500 To 10 Kev, George F. Hagner

Doctoral Dissertations

"The charge transfer reactions of 0-, S- with atomic hydrogen were studied from 1.5 to 10 KeV, and the reaction Cl- + O2 + O2- + Cl was studied from 10 eV to 10 KeV. The reactions studied were normalized to the reaction H- + H + H + H-. The maximum measured cross sections were 4.6 x 10-16 cm2 for the reaction Cl- + O2 + O2- + Cl and 4.4 x 10-15 cm2 for the reaction 0- + H …

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Alignment Of Ions In Penning Collisions, D. W. Fahey, Laird D. Schearer, William F. Parks Jan 1979

Alignment Of Ions In Penning Collisions, D. W. Fahey, Laird D. Schearer, William F. Parks

Physics Faculty Research & Creative Works

The authors have observed the alignment of the 5p P322 state of strontium ions produced in Penning collisions between an unpolarized beam of helium metastable atoms and a strontium vapor target. The alignment is shown by a linear polarization of the optical emission from the excited ion. For a 66-meV beam of helium metastable atoms a 3.5% linear polarization of the emission relative to the beam axis was measured. It is shown how the alignment may be used to determine the probabilities for populating the various final Quasi molecular states of the ion-atom pair. The alignment of the Penning ions …

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The Oguchi-Kaneyoshi Method For Spin-Glasses, M. Jursich, Harry A. Brown Jan 1979

The Oguchi-Kaneyoshi Method For Spin-Glasses, M. Jursich, Harry A. Brown

Physics Faculty Research & Creative Works

The results of an effective field calculation of the phase diagram and order parameters for a random exchange Ising model are presented. This calculation was based on an exchange coupled pair instead of the single-spin molecular-field theory. This approach should be an improvement over the infinite-ranged models because it includes localized effects. The results indicate that the local disorder effects are especially important at low temperatures. © 1979, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

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Electron Transport In Se-Doped Lt-Tas2, Paul D. Hambourger, F. J. Disalvo Jan 1979

Electron Transport In Se-Doped Lt-Tas2, Paul D. Hambourger, F. J. Disalvo

Physics Faculty Publications

No abstract provided.

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Nonlinear Anelasticity And The Martensitic Transformation, Manfred Wuttig, Tetsuro Suzuki Jan 1979

Nonlinear Anelasticity And The Martensitic Transformation, Manfred Wuttig, Tetsuro Suzuki

Materials Science and Engineering Faculty Research & Creative Works

Zener's model of a standard linear solid is extended to include nonlinearities characteristic of metals and alloys in the vicinity of a martensitic transformation. The equation of motion of a nonlinear anelastic solid is derived and solved using van der Pol's method. The characteristics of the solutions indicate that auto-oscillations of finite amplitude can be excited externally. It is proposed that the streaming oscillations represent the beat between the external excitation and the auto-oscillation. © 1979.

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Proton Spin Relaxation And Methyl And Hydroxy Group Motion, Peter A. Beckmann Jan 1979

Proton Spin Relaxation And Methyl And Hydroxy Group Motion, Peter A. Beckmann

Physics Faculty Research and Scholarship

Proton spin-lattice relaxation rates R = T1−1 have been measured in powdered samples of 4-methyl-2,6-di-tertiarybutyl phenol between 77 and 170 K. Deuteration of the hydroxy proton leads to a large change in R in the vicinity of the 120-K R maximum and in the high-temperature region. The data are successfully, although probably not uniquely, fitted and the interpretation suggests that in addition to the motion of the hydroxy proton playing a significant role in the relaxation, the two pairs of t-butyl methyl groups also contributing are inequivalent. The departure, at low temperatures, from an ω−2dependence of R where …

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