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Showing papers on "Ion published in 1986"


01 Jan 1986
TL;DR: In this article, an expression for the probability of tunnel ionization in an alternating field, of a complex atom and of an atomic ion that are in an arbitrary state, was derived in the quasiclassical approximation n* $1.
Abstract: An expression is derived for the probability of tunnel ionization, in an alternating field, of a complex atom and of an atomic ion that are in an arbitrary state. The expression for the tunnel-ionization probability is obtained in the quasiclassical approximation n* $1. Expressions are also obtained for states with arbitrary values of I at arbitrary ellipticity of the radiation. A quasiclassical approximation yields results up to values n * ~ 1, with accuracy up to several percent.

1,504 citations


Journal ArticleDOI
TL;DR: In this article, a corrected analytic formulation was developed which on radial integration closely reproduces the value of stopping power for protons in the energy range 0.1-1000 MeV.

449 citations


Journal ArticleDOI
TL;DR: In this article, the charged particle fluxes from circular planar magnetrons with different magnetic field configurations were investigated and the authors reported measurements of the currents to earthed substrates, the substrate self-biasing voltages, the ion currents to substrates at −100 V, and deposition rates as functions of axial and radial positions with respect to the target.
Abstract: We have investigated the charged particle fluxes from circular planar magnetrons with different magnetic field configurations and report measurements of the currents to earthed substrates, the substrate self‐biasing voltages, the ion currents to substrates at −100 V, and deposition rates as functions of axial and radial positions with respect to the target. The magnetrons fall into two classes, whose characteristics are explained in terms of electron motion in inhomogeneous magnetic fields. Both low and high electron/ion bombardment of the growing film can be achieved by small alterations to the magnetic field configuration.

396 citations


Journal ArticleDOI
TL;DR: In this paper, the ion-aerosol attachment coefficients are calculated for Fuchs' theory and for a theory which includes three body trapping, and the resulting charge distributions agree quite well for particles with radii greater than about 0.007 μm.
Abstract: Calculations of the ion—aerosol attachment coefficients are carried out for Fuchs' theory (as corrected in this paper) and for a theory which includes three body trapping. The resulting charge distributions agree quite well for particles with radii greater than about 0.007 μm. For smaller particles three-body trapping becomes increasingly important. Comparison of theoretically predicted charge distributions with recently measured charge distributions at radii smaller than 0.02 μm show good agreement. Asymmetric charging due to differences in the physical properties of positive and negative ions can result in large differences in the number of positively and negatively charged particles, particularly at larger radii. The asymmetric charge distribution is also shown to depend on the ionization rate. For the case when aerosol concentrations are comparable to the ion concentrations the effect of polydispersity on the charge distribution is difficult to predict. It is shown that a dominant size particle can es...

383 citations


Journal ArticleDOI
TL;DR: A specific model for the membrane dipole potential is introduced, treating it as a two-dimensional array of point dipoles located near each membrane-water interface, and successfully describes the complete set of thermodynamic parameters for binding and translocation for the two hydrophobic ion structural analogues, tetraphenylphosphonium (TPP+) and tetrapenylboron (TPB-).

345 citations


Journal ArticleDOI
TL;DR: In this article, a strong correlation has been found between the bulk energy per AMU for fast ions measured by charge cups and the x-ray-determined hot electron temperature.
Abstract: Data on the emission of energetic ions produced in laser–matter interactions have been analyzed for a wide variety of laser wavelengths, energies, and pulse lengths. Strong correlation has been found between the bulk energy per AMU for fast ions measured by charge cups and the x‐ray‐determined hot electron temperature. Five theoretical models have been used to explain this correlation. The models include (1) a steady‐state spherically symmetric fluid model with classical electron heat conduction, (2) a steady‐state spherically symmetric fluid model with flux limited electron heat conduction, (3) a simple analytic model of an isothermal rarefaction followed by a free expansion, (4) the lasnex hydrodynamics code [Comments Plasma Phys. Controlled Fusion 2, 85 (1975)], calculations employing a spherical expansion and simple initial conditions, and (5) the lasnex code with its full array of absorption, transport, and emission physics. The results obtained with these models are in good agreement with the experiments and indicate that the detailed shape of the correlation curve between mean fast ion energy and hot electron temperature is due to target surface impurities at the higher temperatures (higher laser intensities) and to the expansion of bulk target material at the lower temperatures (lower laser intensities).

342 citations


Journal ArticleDOI
TL;DR: In this paper, a simple model of the distributions of charge created in an insulator by bombardment with electrons, the components of the electric field are evaluated by using Maxwell's equations and image effects, applied to the most common experimental situations: a semi-infinite sample (i) bounded by a vacuum or (ii) covered by a conducting film, and a sample in the form of a film (iii) unsupported or (iv) covering a conducting substrate.
Abstract: Starting from a simple model of the distributions of charge created in an insulator by bombardment with electrons, the components of the electric field are evaluated by using Maxwell’s equations and image effects. The results are applied to the most common experimental situations: a semi‐infinite sample (i) bounded by a vacuum or (ii) covered by a conducting film, and a sample in the form of a film (iii) unsupported or (iv) covering a conducting substrate. The results are compared to some experimental data concerning, for instance, electromigration and electron‐stimulated desorption. In surface analysis the decay of the Auger signal from ions of opposite charges and the opposite behavior of ions of the same charge are explained. Similar effects observed in electron‐probe microanalysis of glasses are also elucidated. The results concern scanning electron microscopy, transmission electron microscopy, and electron‐beam lithography applied to biological objects, polymers, ceramics, minerals, glasses, and electronic devices. With slight modifications, the same model can be applied to cases of irradiation with ions or x rays. The evolution of the trapped charges with time is suggested, and the need to indicate the electric parameters (e and γ) of the investigated samples is outlined.

299 citations


Journal ArticleDOI
TL;DR: In this article, the complex refractive index and the complex dielectric constant for diamond-like amorphous carbon (a•C) films in the photon energy range 0.5 − 7.3 eV were derived via the use of sum rules.
Abstract: The complex refractive index N(ω)=n+ik and the complex dielectric constant e(ω)=e1+ie2 are presented for diamondlike amorphous carbon (a‐C) films in the photon energy range 0.5–7.3 eV. The effective number of valence electrons neff per carbon atom, the static dielectric constant e0,eff, and the energy loss function Im[−1/e(ω)] are deduced via the use of sum rules and are used to interpret the optical data. The a‐C films were deposited using an unbalanced magnetron gun to sputter a graphite target (effective sputtering area of 20 cm2) in ultrapure argon gas. The magnetron is characterized by a high deposition flux of condensing atoms (1.5×1014–1.2×1016 cm−2 s−1) and a concomitant high ion flux (6×1014–2.5×1016 cm−2 s−1). A series of films were prepared by sputtering at different power levels in the range 5–500 W. Insulating substrates were used which allowed the films to self‐bias negatively with respect to the plasma, so that the films were bombarded during their growth by Ar+ ions of energy 16–13 eV at a...

284 citations


Journal ArticleDOI
TL;DR: In this paper, the interference on the ionization of cobalt by five salts, NaCl, MgCl/sub 2/, NH/sub 4/I, NH/Sub 4/Br, and NH/ Sub 4/Cl, is first looked at theoretically, and subsequently the theoretical trends are established experimentally by mass spectrometry (ICP-MS).
Abstract: The interference on the ionization of cobalt by five salts, NaCl, MgCl/sub 2/, NH/sub 4/I, NH/sub 4/Br, and NH/sub 4/Cl, in an inductively coupled plasma (ICP) is first looked at theoretically, and subsequently the theoretical trends are established experimentally by mass spectrometry (ICP-MS). The interference trends are found to be in the order of the most easily ionized element in the matrix salt, i.e., Na > Mg > I > Br > Cl. Quantitatively the theoretical values for the amount of salt needed to produce a particular interference are 1-2 orders of magnitude higher than the experimentally determined values. The results reported here indicate that ICP-MS is somewhat more susceptible to ionization suppression effects than ICP atomic emission spectrometry. It is also found that the most easily ionized element in the salt dominates the matrix ion spectrum observed from the ICP in the order mentioned above. Total ion current measurements by ICP-MC at solute levels above 1% are complicated by orifice plugging and transport loss of the salt and analyte in the desolvation system for the ultrasonic nebulizer used. 27 references, 7 figures, 3 tables.

279 citations


Journal ArticleDOI
TL;DR: In this article, it is suggested that the observed broad band electric field fluctuations in the frequency range between 0 and 100 Hz can be responsible for the transverse energization of the ions through cyclotron resonance heating with the left-hand polarized electromagnetic waves.
Abstract: Central plasma sheet (CPS) ion conics are oxygen-dominated, with peak energies ranging from tens to hundreds of eV centered around pitch-angles between 115 and 130 degrees. Because of the lack of correlation between the CPS conics and the observed currents and/or electron beam-like structures, it is not likely that all of these conics are generated by interactions with electrostatic ion cyclotron waves or lower hybrid waves. Instead, it is suggested that the observed intense broad band electric field fluctuations in the frequency range between 0 and 100 Hz can be responsible for the transverse energization of the ions through cyclotron resonance heating with the left-hand polarized electromagnetic waves. This process is much more efficient for heating the oxygen ions than hydrogen ions, thus providing a plausible explanation of the oxygen dominance in CPS conics. Simple algebraic expressions are given from which estimates of conic energy and pitch angle can be easily calculated. This suggested mechanism can also provide some preheating of the oxygen ions in the boundary plasma sheet (BPS) where discrete aurorae form.

253 citations


Journal ArticleDOI
TL;DR: In this paper, the infrared spectra of hydrated hydronium ions weakly bound to an H2 molecule, specifically H7O + 3 ·H2 and H9O + 4 ·H 2, have been observed.
Abstract: Infrared spectra of hydrated hydronium ions weakly bound to an H2 molecule, specifically H7O + 3 ·H2 and H9O + 4 ·H2, have been observed. Mass-selected parent ions, trapped in a radio frequency ion trap, are excited by a tunable infrared laser; following absorption, the complex predissociates with loss of the H2, and the resulting fragment ions are detected. Spectra have been taken from 3000 to 4000 cm^−1, with a resolution of 1.2 cm^−1. They are compared to recent theoretical and experimental spectra of the hydronium ion hydrates alone. Binding an H2 molecule to these clusters should only weakly perturb their vibrations; if so, our spectra should be similar to spectra of the hydrated hydronium ions H7O + 3 and H9O + 4 .


Journal ArticleDOI
Richard A. Gottscho1, Carl E. Gaebe1
TL;DR: Using temporally and spatially resolved laser spectroscopy, this paper determined the identities, approximate concentrations, effects on the local field, and kinetics of formation and loss of negative ions in RF discharges.
Abstract: Using temporally and spatially resolved laser spectroscopy, we have determined the identities, approximate concentrations, effects on the local field, and kinetics of formation and loss of negative ions in RF discharges. Cl- and BCl3- are the dominant negative ions found in low-frequency discharges through Cl2 and BCl3, respectively. The electron affinity for Cl is measured to be 3.6118 ± 0.0005 eV. Negative ion kinetics are strongly affected by application of the RF field. Formation of negative ions by attachment of slow electrons in RF discharges is governed by the extent and duration of electron energy relaxation. Similarly, destruction of negative ions by collisional detachment and field extraction is dependent upon ion energy modulation. Thus, at low frequency, the anion density peaks at the beginning of the anodic and cathodic half-cycles after electrons have attached but before detachment and extraction have had time to occur. At higher frequencies, electrons have insufficient time to attach before they are reheated and the instantaneous anion density in the sheath is greatly reduced. When the negative ion density is comparable to the positive ion density, the plasma potential is observed to lie below the anode potential, double layers form between sheath and plasma, and anions and electrons are accelerated by large sheath fields to electrode surfaces.

Journal ArticleDOI
TL;DR: In this article, the characteristics of a new design of magnetron sputter source (a UM‐gun), based on the principle of an unbalanced magnetic design, and capable of giving ion fluxes at the substrate greater than the flux of depositing atoms, were reported.
Abstract: We report the characteristics of a new design of magnetron sputter source (a UM‐gun), based on the principle of an unbalanced magnetic design, and capable of giving ion fluxes at the substrate greater than the flux of depositing atoms The dependencies of ion flux and self‐bias potential at a typical substrate position for certain target materials (copper and silicon), gas pressures (025–5 Pa), gas compositions (Ar with O2, N2, and He), and sputtering power levels (up to 2 kW) have been measured for a particular UM‐gun The results show that such guns can be characterized approximately by an ion flux proportional to the discharge current and a constant self‐bias potential

Journal ArticleDOI
TL;DR: The electron affinities (EA) of the corresponding neutral clusters are roughly bracketed by measuring the fluence dependence for photodetachment from anions at discrete probe laser wavelengths.
Abstract: Silicon, germanium, and gallium arsenide negative cluster ions are produced by laser vaporization followed by free supersonic expansion. Electron affinities (EA) of the corresponding neutral clusters are roughly bracketed by measuring the fluence dependence for photodetachment from anions at discrete probe laser wavelengths (above the photodetachment threshold the dependence on fluence is linear, below it is quadratic). An even/odd alternation is found in the negative ion distribution with gallium arsenide clusters with an odd number of atoms having higher EA’s than their even neighbors. This suggests that the surfaces of the even clusters are extensively restructured in a way which eliminates dangling chemical bonds. For GaxAsy with x+y constant, EA increases with increasing ratio of y to x. The EA of silicon increases smoothly with cluster size extrapolating towards the EA of bulk silicon. Photofragmentation studies show that, like the corresponding positive ions, silicon and germanium negative ions wit...

Journal ArticleDOI
TL;DR: In this paper, the anions Fe−2 and Co−2 were prepared and cooled to 300 K in a flowing afterglow ion source, and the low-lying electronic states of the neutral dimers were probed by negative ion photoelectron spectroscopy.
Abstract: The anions Fe−2 and Co−2 were prepared and cooled to 300 K in a flowing afterglow ion source, and the low‐lying electronic states of the neutral dimers were probed by negative ion photoelectron spectroscopy. Previous ab initio studies of Fe2 and Co2 have predicted single 4s–4s bonds, and extremely high densities of low‐lying states due to the small energy cost in transferring electrons among nonbonding 3d orbitals. In contrast to the complex photoelectron spectra implied by these calculations, the observed spectra are remarkably simple. It is argued that this spectral simplicity implies a greater role for the 3d electrons in the iron and cobalt dimer bonds. These data also provide values for the electron affinities of the neutral dimers (0.902±0.008 eV Fe2, 1.110±0.008 eV Co2), the bond elongation on electron attachment (0.08±0.02 A Fe2, Co2), and the vibrational frequencies of the anions (250±20 cm−1 Fe−2, 240±15 cm−1 Co−2). Related studies of the atomic anions yield improved values for the electron affi...

Journal ArticleDOI
Charles Angell1
TL;DR: In this article, a review of recent developments in the expanding phenomenology of amorphous solid electrolytes is presented, and the authors emphasize the importance of studying the fast ion motions by mechanical response, in addition to electrical response measurements.

Journal ArticleDOI
TL;DR: In this article, an unbalanced magnetron (UM-gun) sputtering source with the unique characteristic of a high deposition rate and concomitant high ion flux represent an exciting new development in ion-assisted deposition of thin films.
Abstract: Unbalanced magnetron (UM‐gun) sputtering sources with the unique characteristic of a high deposition rate and concomitant high ion flux represent an exciting new development in ion‐assisted deposition of thin films. We have used a UM‐gun capable of producing ion current densities up to 5 mA cm−2 (ion flux 3×1016 cm−2 s−1) when operated at a power of 500 W to produce a variety of thin films of amorphous and crystalline materials by varying both the bombarding ion energy in the range 2–100 eV and the ion/atom arrival rate ratio in the range 0.4–10. The great flexibility and usefulness of UM‐guns is demonstrated with examples which include (a) hard diamondlike a‐C films prepared under very low ion energy (13–16 eV) bombardment which possess a metastable bonding configuration consisting of a mixture of tetrahedral and trigonal coordination that varies with ion energy, (b) hard and wear‐resistant TiN films whose electrical and optical properties change dramatically with ion bombardment, and (c) Ni/Cr alloy fil...

Journal ArticleDOI
TL;DR: In this paper, a photodissociation method was used for mass-selected transition metal cluster ions cooled in a supersonic expansion to reveal the thresholds and time scales of various fragmentation pathways.
Abstract: Photofragmentation studies are described for mass‐selected transition metal cluster ions cooled in a supersonic expansion. Examples of the spectral utility of this technique are presented in the cases of Ni+2 and Nb+2 for which well resolved vibronic bands have been recorded by monitoring fragment yield as a function of dissociation laser wavelength. For larger, more complicated metal clusters the absorption spectrum is far too congested and perturbed for analysis, but photodissociation can reveal the thresholds and time scales of various fragmentation pathways. The order of the absorption event leading to dissociation is found from the extent of fragmentation as a function of laser fluence. Using this method, the one‐photon dissociation threshold of Fe+2 is found to lie between 2.43 and 2.92 eV, which determines the binding energy of this transition metal dimer cation. Combined with previous ionization potential measurements this places the binding energy of the Fe2 neutral between 0.83 and 1.32 eV. Simi...

Journal ArticleDOI
TL;DR: Comparison with experimental data demonstrates the applicability of the model for ion specific energies greater than 1 MeVu-1 and shows that the energy density varies according to an inverse-square function with distance from the track centre.
Abstract: The energy deposition in ion tracks as a function of radial distance is calculated on the basis of classical collision dynamics and using empirical range-energy relationships for electrons The calculations show that the energy density (ie energy deposited per unit mass) varies according to an inverse-square function with distance from the track centre The maximum extension, the 'penumbra radius', is a power function of the ion's kinetic energy divided by its mass Comparison with experimental data demonstrates the applicability of the model for ion specific energies greater than 1 MeV u-1

Journal ArticleDOI
TL;DR: In this paper, a hybrid mass spectrometer of BEQQ geometry (B, magnetic sector; E, electric sector; Q, quadrupole mass filter), designed for fundamental and applied studies in gaseous ion chemistry, is described.

Journal ArticleDOI
TL;DR: In this article, a model is proposed in which transient complex formation is followed by vibrational predissociation in the complex and a vibrational rate constant in the range 10/sup 9/-10/sup 10/ s/sup -1/ is found applicable to a number of cases.
Abstract: Selected ion flow drift tube techniques have recently been developed for the measurement of molecular ion vibrational relaxation rate constants. The first systematic studies of ion vibrational relaxation show that the collisional quenching rate constants are generally large and generally decrease with relative energy in the thermal range. This is a clear indication that the quenching is dominated by the long-range attractive forces. A model is proposed in which transient complex formation is followed by vibrational predissociation in the complex. If one utilizes ion-neutral vibrational relaxation and three-body association of the same ion-neutral reactants, a vibrational predissociation rate constant in the range 10/sup 9/-10/sup 10/ s/sup -1/ is found applicable to a number of cases. The magnitudes of vibrational relaxation rate constants in some cases yield new insights into ion-molecule interaction potentials. 62 references, 4 figures, 2 tables.

Journal ArticleDOI
TL;DR: In this paper, a negative ion photoelectron spectrometer using time-of-flight for both ion mass selection and photo-electron energy analysis is described and demonstrated on the 532 nm photodetachment of the well-known O − and O − 2 ions.

Journal ArticleDOI
18 Apr 1986-Science
TL;DR: Conclusive evidence is presented for the existence of energetic (∼535,0000 to 150,000 electron volts), heavy (>-12 atomic mass units), singly charged cometary ions within ∼1.5 x 106 kilometers of comet Giacobini-Zinner.
Abstract: Conclusive evidence is presented for the existence of heavy energetic, singly charged cometary ions within 1.5 million km of comet Giacobini-Zinner. The most direct evidence for establishing the mass of these ions was obtained from an analysis of the energy signals in one of the solid state detector on board the International Cometary Explorer. Maximum fluxes were recorded approximately one hour before and after closest approach to the cometary nucleus. Transformation of the particle angular distribution observed at approximately 50,000 km radial distance from the comet, during the inbound pass into a rest frame in which the distributions are nearly isotropic, requires a transformation velocity that is consistent with the local solar wind velocity (assuming these particles are primarily singly ionized with a mass of 18 + or - 6 amu). It is implied that these water-group ions underwent strong pitch angle scattering subsequent to ionization and that they were accelerated or heated. The derived ion density, approximately 0.1/cu cm, is consistent with a crude model for the production and transport of pickup ions.

Journal ArticleDOI
TL;DR: In this article, a vibrational analysis of the title compound and of its monomeric radical anion is reported, based on the Raman depolarization ratio measurements and on infrared data of solutions of both neutral and ionic species as well as on polarized infrared spectra of oriented crystals of the neutral molecule.
Abstract: A fundamental aspect in the study of the charge–transfer (CT) organic crystals with ionic or partially ionic ground states is the investigation of the spectroscopic effect of the electron–molecular vibration coupling. 7,7,8,8‐tetracyano‐2,3,5,6‐tetrafluoroquinodimethane (TCNQF4), an electron acceptor much stronger than TCNQ, is an outstanding component of many interesting CT systems. A thorough vibrational analysis of the title compound and of its monomeric radical anion is reported. The analysis is based on the Raman depolarization ratio measurements and on infrared data of solutions of both neutral and ionic species as well as on polarized infrared spectra of oriented crystals of the neutral molecule. The vibrational assignment, completed by a normal coordinate analysis (NCA), brings to the identification of the ionization frequency shifts and to the choice of the fundamentals (b1uν19 and b2uν33) whose frequencies are diagnostic of the degree of charge transfer for a TCNQF4 moiety partner of a CT system...

Journal ArticleDOI
TL;DR: In this paper, a typical upwelling event is analyzed using Dynamic Explorer 1 satellite retarding ion mass spectrometer (RIMS) observations of the low-energy plasma, and energetic ion and local electromagnetic field observations.
Abstract: The characteristics of an upwelling ion source are discussed. A typical upwelling event is analyzed using Dynamic Explorer 1 satellite retarding ion mass spectrometer (RIMS) observations of the low-energy plasma, and energetic ion and local electromagnetic field observations. The RIMS spectrograms of the O(+) ion species, radial and axial head data for O(+), and spin plan O(+) distribution functions are examined. The features of the upwelling observed include: (1) transverse ion heating to temperature of 100,000 K, (2) large outward flows of O(+), (3) enhanced flow of H(+) and He (+), (4) moderately strong field-aligned current sheets, (5) an associated intense eastward convection channel, and (6) strong wave emissions in the range near and below the proton gyrofrequency. The association between the upwelling O(+) signature and auroral current is investigated. Plasma wave and electric field environments are studied and plasma flows and densities are derived. It is noted that the mechanism for ion heating which defines the source region for these polar ion outflows is related to field-aligned currents and an associated auroral convection channel or jet.

Journal ArticleDOI
TL;DR: In this article, Monte Carlo simulations were performed on the stability of the water cluster ion (H2O)21H+ and H2O28H+ for the first time, with very small excess energy.
Abstract: The near threshold vacuum‐UV photoionization of water clusters has been performed by using a resonance line emission of argon at 1183 eV The well‐known intensity anomaly at the cluster ion (H2O)21H+ is observed even in this threshold photoionization, for the first time, with very small excess energy Structures for the water cluster ions (H2O)21H+ and (H2O)28H+ which exhibit enhanced structural stability (magic number), are presented based on Monte Carlo simulations as well as on the analogy of our previous study on the stability of the (H2O)20NH+4 ion The Monte Carlo calculations are carried out at the temperatures of 200, 150, 100, and 50 K for the ionized water clusters (H2O)nH+ around n=21 and also around n=28, which includes the ionic hydrogen‐bond interactions between an H3O+ ion and neutral H2O molecules The clusters (H2O)21H+ and (H2O)28H+ have greater binding energies per molecule than their neighbors although the enhancement of the latter is somewhat temperature dependent The calculations s

Journal ArticleDOI
TL;DR: In this paper, the mass distributions of negative cluster ions of copper (Cu), silver (Ag), and gold (Au) were investigated up to cluster size n = 250 and were compared with those of the positive cluster ions.

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TL;DR: In this paper, the electrical characteristics of low frequency (50 kHz) and high frequency (13.56 MHz) discharges used for the deposition of amorphous hydrogenated carbon thin films from CH4, C6H6 and theeir mixtures with helium gas were investigated.

Journal ArticleDOI
TL;DR: In this article, the authors considered the linear theory of waves near and below the ion cyclotron frequency in an isothermal electron-ion Vlasov plasma which is isotropic, homogeneous and magnetized.
Abstract: This paper considers the linear theory of waves near and below the ion cyclotron frequency in an isothermal electron-ion Vlasov plasma which is isotropic, homogeneous and magnetized. Numerical solutions of the full dispersion equation for the magnetosonic/whistler and Alfven/ion cyclotron modes at beta(i) = 1.0 are presented, and the polarizations, compressibilities, helicities, ion Alfven ratios and ion cross-helicities are exhibited and compared. At sufficiently large beta(i) and theta, the angle of propagation with respect to the magnetic field, the real part of the polarization of the Alfven/ion cyclotron wave changes sign, so that, for such parameters, this mode is no longer left-hand polarized. The Alfven/ion cyclotron mode becomes more compressive as the wavenumber increases, whereas the magnetosonic/whistler becomes more compressive with increasing theta.