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Physics Faculty Research & Creative Works

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Articles 1831 - 1860 of 1961

Full-Text Articles in Physical Sciences and Mathematics

Note On Amorphous Magnetic Materials, Louis H. Lund Jan 1976

Note On Amorphous Magnetic Materials, Louis H. Lund

Physics Faculty Research & Creative Works

No abstract provided.

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Radiative Lifetimes Of Some Group Ii Ions By The Hanle Effect In A Fast-Flowing Helium Afterglow, F. H.K. Rambow, Laird D. Schearer Jan 1976

Radiative Lifetimes Of Some Group Ii Ions By The Hanle Effect In A Fast-Flowing Helium Afterglow, F. H.K. Rambow, Laird D. Schearer

Physics Faculty Research & Creative Works

Radiative lifetimes of the first P322 state of Mgu, Cau, Znu, Sru, Cdu, and Bau are reported as measured by the Hanle effect in a fast-flowing helium afterglow. They are, respectively, 3.65(0.12), 6.61(0.30), 2.4(0.3), 6.64(0.10), 2.86(0.25), 6.78(0.40) in units of 10-9 sec. The ions in the afterglow are created by Penning ionization of the neutral metal atoms, thus providing a steady-state, field-free region for observation. Comparisons are made with measurements by other methods, and discrepancies are discussed. © 1976 The American Physical Society.

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Radiative Lifetimes And Alignment Depolarization Cross Sections For Ybi And Ii By The Hanle Effect In A Flowing Helium System, F. H.K. Rambow, Laird D. Schearer Jan 1976

Radiative Lifetimes And Alignment Depolarization Cross Sections For Ybi And Ii By The Hanle Effect In A Flowing Helium System, F. H.K. Rambow, Laird D. Schearer

Physics Faculty Research & Creative Works

The radiative lifetimes of the 17992-,25068-,28857-, 37414-, 40564-, and 44017-cm-1 neutral levels and the 30392-cm-1 ion level of Yb have been measured by the Hanle method in a fast-flowing He system. The lifetimes (in units of 10-9 sec) were found to be 820(20), 5.12(0.12), 14.4(0.4), 77.4(6.0), 9.32(0.6), 39.1(3.5), and 5.8(0.6), respectively. In a flowing system with He as a buffer gas the alignment depolarization cross sections with Yb were obtained and are reported here for the first time. They are (in units of 10-15 cm2) 5.0(1.0), 5.9(1.0), 5.9(1.2), 17.9(2.0), 28.2(3.0), 5.16(4.0), and 7.2(2.5), respectively. © 1976 The American Physical Society.

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Surface Electromagnetic Waves With Damping. I. Isotropic Media, G. S. Kovener, Ralph William Alexander, Robert John Bell Jan 1976

Surface Electromagnetic Waves With Damping. I. Isotropic Media, G. S. Kovener, Ralph William Alexander, Robert John Bell

Physics Faculty Research & Creative Works

Surface-Electromagnetic-Wave Dispersion Curves Are Usually Calculated using a Simple Equation Derived from Maxwell's Equations and Boundary Conditions. When Complex Dielectric Functions Are Used for the Two Media, the Component of the Propagation Vector Along the Surface, Kx, Becomes Infinite as the Frequency Approaches the Surface Polariton Frequency Ωs If Ω is Considered Complex and Kx is Real. on the Other Hand, If Kx is Considered Complex and Ω Real, the Dispersion Curves Bend Back Toward Smaller Kx as Ω Approaches Ωs. We Have Previously Demonstrated that Both Types of Behavior Can Be Obtained from Attenuated-Total-Reflection Measurements of Silver. We Now …

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Comment On "Clustering Of Water On Hydrated Protons In A Supersonic Free Jet Expansion", James L. Kassner, Donald E. Hagen Jan 1976

Comment On "Clustering Of Water On Hydrated Protons In A Supersonic Free Jet Expansion", James L. Kassner, Donald E. Hagen

Physics Faculty Research & Creative Works

No abstract provided.

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Absorption In The Infrared Of Surface Electromagnetic Waves By Adsorbed Molecules On A Copper Surface, K. Bhasin, D. Bryan, Ralph William Alexander, Robert John Bell Jan 1976

Absorption In The Infrared Of Surface Electromagnetic Waves By Adsorbed Molecules On A Copper Surface, K. Bhasin, D. Bryan, Ralph William Alexander, Robert John Bell

Physics Faculty Research & Creative Works

Experimental Observations Have Been Made for the First Time that Surface Electromagnetic Wave (SEW) Spectroscopy Can Be Used to Measure the Infrared Spectra of Adsorbed Molecules and Very Thin Films on Metal Surfaces. using a Tunable CO2 Laser (9.2-10.8 Μm Wavelength), the 975 and the 1037 Cm-1 Resonances of 5-25 Å Thick Physiosorbed Benzene on Copper Were Observed. Broadening of These Resonances for the Thinnest Layers of Benzene Was Observed. Also SEW Spectroscopy and Ellipsometry Were Used to Study Thin Films of Cellulose Acetate (15-75 Å) on Copper. Further, It Was Shown that Film Thicknesses Determined by SEW Spectroscopy Are …

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Surface Electromagnetic Wave Mode And Field Analysis In A Metal-Metal-Oxide-Air System With Damping, C. A. Ward, Ralph William Alexander, Robert John Bell Jan 1976

Surface Electromagnetic Wave Mode And Field Analysis In A Metal-Metal-Oxide-Air System With Damping, C. A. Ward, Ralph William Alexander, Robert John Bell

Physics Faculty Research & Creative Works

An Explanation is Provided for the Surface Electromagnetic Wave (SEW) Energy Ejection from a Thin Film at the Longitudinal and Transverse Optical-Phonon Frequencies of the Film Material. Field Ratio Calculations Identify Previously Discussed Metal-Metal-Oxide-Air SEW Modes as Those Expected from the Berreman Configuration, and It is Shown that Greenler Technique High-Incidence-Angle-Reflectance Data on the Same System May Be Similarly Interpreted. © 1976 the American Physical Society.

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High-Frequency Dielectric Measurements On Electro-Optic Single Crystals, J. R. Teague, R. R. Rice, Robert Gerson Dec 1975

High-Frequency Dielectric Measurements On Electro-Optic Single Crystals, J. R. Teague, R. R. Rice, Robert Gerson

Physics Faculty Research & Creative Works

A slotted line was used to measure the high-frequency dielectric constant and loss tangent of several electro-optic crystals useful for wide-band laser modulator applications. Dielectric measurements were made at 0.1, 0.3, 1.0, and 2.0 GHz.

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Saturation Effects In A Tunable Coherent Near-Infrared Source, Israel L. Tyler, R. (Ralph) W. Alexander, R. (Robert) J. (John) Bell Dec 1975

Saturation Effects In A Tunable Coherent Near-Infrared Source, Israel L. Tyler, R. (Ralph) W. Alexander, R. (Robert) J. (John) Bell

Physics Faculty Research & Creative Works

A Saturation Effect in a Tunable Infrared Source Utilizing Four-Wave Parametric Conversion in Potassium Vapor is Reported and is Shown to Be the Result of Parasitic Oscillations. a Hundredfold Increase over Previously Attained Power Levels Has Been Affected Via Elimination of These Oscillations.

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Radiative Lifetime Of The B ²Σˉ State Of Ch, Richard A. Anderson, Jerry Peacher, David M. Wilcox Dec 1975

Radiative Lifetime Of The B ²Σˉ State Of Ch, Richard A. Anderson, Jerry Peacher, David M. Wilcox

Physics Faculty Research & Creative Works

The radiative lifetimes of the N'=3 to 15 rotational states of the v'=0 level of the B 2Σ- state of CH were measured. Emission lines were observed to N'=15, but no lines above this rotational state were observed. This result agrees with previous studies. The lifetimes of all rotational states were between 300 and 400 ns. Previous measurements have indicated that the N'=15 level might have a lifetime as short as 100 ns.

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Intrinsic Viscosity Of Stiff Dumbbells From Time Correlation Functions, Gerald Wilemski Sep 1975

Intrinsic Viscosity Of Stiff Dumbbells From Time Correlation Functions, Gerald Wilemski

Physics Faculty Research & Creative Works

The intrinsic viscosity of a suspension of stiff dumbbells is evaluated by a time correlation function method. The required moments of the internal coordinates are calculated directly from the diffusion equation, without explicit evaluation of the Green's function. For the rigid dumbbell, the correct high frequency limit is obtained, disposing of recent doubts over this possibility. The interplay of dumbbell stiffness and shearing frequency is also illustrated.

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Energy And Angular Distribution Of Electrons Ejected From Helium By Fast Protons And Electrons: Theory And Experiment, Steven Trent Manson, Larry H. Toburen, Don H. Madison, Nikolaus Stolterfoht Jul 1975

Energy And Angular Distribution Of Electrons Ejected From Helium By Fast Protons And Electrons: Theory And Experiment, Steven Trent Manson, Larry H. Toburen, Don H. Madison, Nikolaus Stolterfoht

Physics Faculty Research & Creative Works

A comprehensive study of the angular and energy distributions of electrons ejected in collisions of fast electrons and protons with He is presented. New experimental results for 300-keV, 1-MeV, and 5-MeV proton impact are reported along with theoretical results for 2-keV electron impact and 100-keV, 300-keV, 1-MeV, and 5-MeV proton impact. The theoretical results, based upon Born approximation with Hartree-Slater initial discrete and final continuum wave functions, show excellent agreement with experimental electron-impact results. Serious discrepancies are found between theory and experiment in the angular distribution of ejected electrons for forward angles for 100- and 300-keV proton impact; the discrepancies …

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Some Comments On Correlation-Function Formulas For Polymer Intrinsic Viscosity, Walter H. Stockmayer, Gerald Wilemski, Hiromi Yamakawa, Genzo Tanaka Jul 1975

Some Comments On Correlation-Function Formulas For Polymer Intrinsic Viscosity, Walter H. Stockmayer, Gerald Wilemski, Hiromi Yamakawa, Genzo Tanaka

Physics Faculty Research & Creative Works

No abstract provided.

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Binary Nucleation. I. Theory Applied To Water-Ethanol Vapors, Gerald Wilemski May 1975

Binary Nucleation. I. Theory Applied To Water-Ethanol Vapors, Gerald Wilemski

Physics Faculty Research & Creative Works

A quantitative study of nucleation in vapor mixtures of ethanol and water near 273°C is presented. First, Reiss' theory of binary nucleation is reexamined. The theory is modified slightly in order to yield the proper limit for homogeneous nucleation in a one-component system. Moreover, a corrected expression for the equilibrium concentration of mixed clusters is derived. Calculations of the critical vapor activities needed to produce a visible condensate are presented and compared with the results of Flood's cloud chamber experiments. The agreement is only fair, but qualitative accord is found.

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Binary Nucleation. Ii. Time Lags, Gerald Wilemski May 1975

Binary Nucleation. Ii. Time Lags, Gerald Wilemski

Physics Faculty Research & Creative Works

The role of the time lag needed to attain steady state nucleation in binary vapors is discussed. Under appropriate conditions it is possible to obtain both a large predicted rate of binary nucleation and a large time lag. In this circumstance, homogeneous nucleation of the more concentrated component may be the predominant process. It is of obvious importance to the experimentalist to differentiate between these possibilities. Approximate formulas for the time lags are developed, and representative calculations for the ethanol-water system are reported.

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Differential Cross Sections For Elastic And Inelastic Scattering Of 15-100-Kev Li⁺ By He, John T. Park, Victor Pol, James E. Lawler, Jacob M. George, John E. Aldag, John W. Parker, Jerry Peacher Mar 1975

Differential Cross Sections For Elastic And Inelastic Scattering Of 15-100-Kev Li⁺ By He, John T. Park, Victor Pol, James E. Lawler, Jacob M. George, John E. Aldag, John W. Parker, Jerry Peacher

Physics Faculty Research & Creative Works

Sets of energy-loss spectra for Li+ incident on He that were taken at a series of scattering angles were used to calculate differential cross sections. Differential cross sections are given for elastic scattering and for excitation of the He (n=2) states. The differential cross section is also given for excitation of states corresponding to a 60-eV energy loss. These inelastic differential cross sections exhibit maxima at scattering angles greater than zero. The velocity dependence of the cross sections can be compensated by displaying the elastic data in ρ-vs-τ plots and the inelastic data in ρ-vs-E3/2θ plots. When …

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Double Reflection Dips From Grating Ruled Semiconductors, L. F. Teng, Ralph William Alexander, Robert John Bell, B. Fischer Jan 1975

Double Reflection Dips From Grating Ruled Semiconductors, L. F. Teng, Ralph William Alexander, Robert John Bell, B. Fischer

Physics Faculty Research & Creative Works

The Double Reflectivity Dips, Previously Observed by Fischer Et Al. and Anderson Et Al., Which Appeared in the Reflection Spectra of Grating Surfaces On, the Te‐doped Semiconductors GaAs and InSb Around Both the Plasmon and Phonon Frequencies Have Been Measured in More Detail. in the Plasmon Region, Several Possible Explanations of the Phenomenon Are Discussed, But the Favored Explanation Involves Surface Damage. a Simple Two‐region Reflectivity Equation Checked with a Rigorous Grating Theory is Proposed and is Shown to Fit the Data Well. Copyright © 1975 WILEY‐VCH Verlag GmbH & Co. KGaA

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Strain Effects On The Esr Spectrum From Antimony Donors In Germanium, Edward Boyd Hale, John R. Dennis, Shih Hua Pan Jan 1975

Strain Effects On The Esr Spectrum From Antimony Donors In Germanium, Edward Boyd Hale, John R. Dennis, Shih Hua Pan

Physics Faculty Research & Creative Works

The electron-spin-resonance spectra from surface-strained (but not externally stressed) antimony-doped germanium are investigated in detail. Experimental data are given for the linewidth, line asymmetry, and line-shape reversal feature as well as for the changes in donor concentration, temperature, and surface conditions. The donors of interest occur in a surface layer several microns thick. A theoretical analysis is based on the Kohn-Luttinger formulation for a shallow donor electron, which is forced by surface strain to predominately occupy a [111] conduction-band valley minimum. A substantial distribution in strain among the donor sites is necessary to account for the line-structure features. These features …

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Use Of The Psi Technique In Prerequisite Courses, John T. Park, William R. Snow Jan 1975

Use Of The Psi Technique In Prerequisite Courses, John T. Park, William R. Snow

Physics Faculty Research & Creative Works

An engineering physics course, in which the Personalized System of Instruction (PSI) technique has been used, has been designed to meet the requirements that all of a prescribed list of subjects be covered and that the course be completed within a single semester. The course was modified so that it has two levels of mastery for each unit: a passing level and a complete mastery level. All students were required to reach a passing level of mastery on all of the required material. Grades were assigned according to the number of complete mastery level examinations passed. It was found that …

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Electron Impact Autoionization In Heavy Alkali Metals, Kaare J. Nygaard Jan 1975

Electron Impact Autoionization In Heavy Alkali Metals, Kaare J. Nygaard

Physics Faculty Research & Creative Works

Autoionizing levels in cesium, rubidium, and potassium have been studied by electron impact in a crossed-beam apparatus. Comparisons are made with the binary-encounter calculations of Roy and Rai. The effects of autoionization and inner-shell ionization have been overestimated in the theory. © 1975 The American Physical Society.

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Biquadratic Exchange And First-Order Ferromagnetic Phase Transitions, Harry A. Brown Jan 1975

Biquadratic Exchange And First-Order Ferromagnetic Phase Transitions, Harry A. Brown

Physics Faculty Research & Creative Works

We have calculated some properties of a ferromagnet using a Heisenberg Hamiltonian with a biquadratic exchange term added. The constant-coupling approximation was employed. If the strength of the biquadratic exchange relative to the bilinear is given by a dimensionless parameter α, there is a critical value αc at which the phase transition changes character from second order for αα>αc. The spontaneous magnetization, the exchange energy, and the spin-correlation function show discontinuous jumps at α=αc and unstable behavior for α>αc. © 1975 The American Physical Society.

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Excitation Of Atomic Hydrogen To The N=2 States By 15-200-Kev Protons, John T. Park, J. E. Aldag, J. M. George Jan 1975

Excitation Of Atomic Hydrogen To The N=2 States By 15-200-Kev Protons, John T. Park, J. E. Aldag, J. M. George

Physics Faculty Research & Creative Works

Cross sections for the process H+ + H H+ + H* (n=2) are determined from the energy-loss spectra of 15-200-keV protons. After normalization at 200 keV to the Born approximation, the maximum value (1.07 x 10-16 cm2 at 60 keV) lies below close-coupling calculations and above Glauber-approximation calculations. The agreement with low-energy (5-30-keV) data of others is very good. © 1975 The American Physical Society.

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Photoionization Of The 6p32,122 Fine-Structure Levels In Cesium, Kaare J. Nygaard, Robert E. Hebner, James A. Jones, Robert J. Corbin Jan 1975

Photoionization Of The 6p32,122 Fine-Structure Levels In Cesium, Kaare J. Nygaard, Robert E. Hebner, James A. Jones, Robert J. Corbin

Physics Faculty Research & Creative Works

The relative photoionization cross sections for cesium atoms selectively excited to the 6P32,122 states have been measured in a triple-crossed-beam experiment. A cesium discharge lamp produced resonant wavelengths of 8521 and 8944 for the excitation process. A Hg-Xe lamp combined with a grating monochromator was used for the actual ionization in the wavelength region from 2500 to 5000. Background counts due to photoionization of ground-state cesium atoms and dimers as well as various surface effects were discriminated against by chopping the excitation light source. The data are compared with results from radiative-recombination measurements in which the fine-structure levels are not …

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A High-Power Pulsed Xenon Ion Laser As A Pump Source For A Tunable Dye Laser, Laird D. Schearer Jan 1975

A High-Power Pulsed Xenon Ion Laser As A Pump Source For A Tunable Dye Laser, Laird D. Schearer

Physics Faculty Research & Creative Works

An inexpensive pulsed xenon ion laser with peak power outputs up to 4 kW has been constructed and used as a pump source for a tunable rhodamine 6G dye laser with a 0.25-A bandpass in the yellow-red range of the spectrum. The dye laser is tunable from 5465 to 6300 A. Over 50 W are obtained at the peak of the tuning range. Copyright © 1975 by The Institute of Electrical and Electronics Engineers, Inc.

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The Use Of Surface Electromagnetic Waves To Measure Materials Properties, Ralph William Alexander, Robert John Bell Jan 1975

The Use Of Surface Electromagnetic Waves To Measure Materials Properties, Ralph William Alexander, Robert John Bell

Physics Faculty Research & Creative Works

An Elementary Introduction to Surface Electromagnetic Waves (SEW) is Presented. the Emphasis is on Those Features of SEW Which Make Them Useful for Measuring Optical Properties of Thin Layers on Metals. the So-Called Two-Prism Technique for Making Such Measurements is Discussed, Some Preliminary Experimental Results Are Given, and Some Possible Applications Are Presented. © 1975.

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Multimedia Dispersion Relation For Surface Electromagnetic Waves, C. A. Ward, K. Bhasin, Robert John Bell, Ralph William Alexander, I. Tyler Jan 1975

Multimedia Dispersion Relation For Surface Electromagnetic Waves, C. A. Ward, K. Bhasin, Robert John Bell, Ralph William Alexander, I. Tyler

Physics Faculty Research & Creative Works

We Have Derived a General, N-Media Dispersion Relation for Surface Electromagnetic Waves Propagating on Isotropic Layers with Complex Dielectric Functions. the Equation is Presented in a Convenient, Compact Form for Ease of Application. Copyright © 1975 American Institute of Physics.

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Analogy Between Spinodal Decomposition And Martensitic Transformation, Tetsuro Suzuki, Manfred Wuttig Jan 1975

Analogy Between Spinodal Decomposition And Martensitic Transformation, Tetsuro Suzuki, Manfred Wuttig

Physics Faculty Research & Creative Works

The translation of the theory developed for the spinodal decomposition of a supercooled alloy to the language appropriate for the martensitic transformation is carried out. In the spinodal theory, the stability of the alloy with respect to the composition fluctuation is examined, while in the present theory the stability of the crystal with respect to the shear displacement fluctuation, the transverse phonon, is studied. The analogy to the spinodal theory requires the revival of the strain gradient energy term or the couple stress term, the presence of which has been a subject of controversies for a long time since Laval. …

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Surface Electromagnetic Waves On Layered Systems With Damping, C. A. Ward, Ralph William Alexander, Robert John Bell Jan 1975

Surface Electromagnetic Waves On Layered Systems With Damping, C. A. Ward, Ralph William Alexander, Robert John Bell

Physics Faculty Research & Creative Works

The Dispersion Curves, Propagation Distances, and Poynting Vectors of Surface Electromagnetic Waves Propagating on a System of Cu-Cu2O-Air with Variable Film Thickness Have Been Calculated using the Full Dispersion Realation Including Damping. Double-Dip Structure in the Propagation Distance for Intermediately Thick overlayers, the Shifting of One Dip Below ΣTO, and the Presence of the Other Dip at ΣLO Are Explained in Terms of Features of the Dispersion Curve. the Complete Poynting-Vector Calculations Show that Predictions of Field Bunching at ΣLO Are Probably in Error. © 1975 the American Physical Society.

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Erratum: Multimedia Dispersion Relation For Surface Electromagnetic Waves. (The Journal Of Chemical Physics (1975) 62 (1674)), C. A. Ward, K. Bhasin, Robert John Bell, Ralph William Alexander, I. Tyler Jan 1975

Erratum: Multimedia Dispersion Relation For Surface Electromagnetic Waves. (The Journal Of Chemical Physics (1975) 62 (1674)), C. A. Ward, K. Bhasin, Robert John Bell, Ralph William Alexander, I. Tyler

Physics Faculty Research & Creative Works

No abstract provided.

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Molecular Model For Ice Clusters In A Supersaturated Vapor, Barbara N. Hale, P. L. M. Plummer Nov 1974

Molecular Model For Ice Clusters In A Supersaturated Vapor, Barbara N. Hale, P. L. M. Plummer

Physics Faculty Research & Creative Works

A molecular model previously applied to prenucleation water clusters is used to examine ice Ih, embryos. The canonical partition function is evaluated for clusters having from 6 to 64 water molecules. The intermolecular vibrational free energies are extrapolated to clusters containing up to 120 molecules and free energies of formation, nucleation rates, and critical supersaturation ratios are calculated and compared with experiment. For the clusters studied, the ice Ih structure appears to be much less stable at all temperatures than the more spherical clathratelike cluster.

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