Monatomic Hydrogen Research Articles

Hydrogen passivation of grain boundaries in polycrystalline gallium arsenide

Exposure to a plasma of monatomic hydrogen at 300 °C for periods of 3–5 h is shown to significantly reduce the reverse leakage currents of surface barrier diodes fabricated from polycrystalline GaAs. The neutralization by hydrogen of electrical activity associated with grain boundaries leads to reductions in leakage current of a factor of 50 in material with grain sizes of 150–400 μm, and a factor of 3 in material with a typical grain size of ∼1 mm.

Structure and screening in molecular and metallic hydrogen at high pressure

A variational wave function proposed by Abrikosov is used to express the (spin-restricted) Hartree-Fock energy as reciprocal-lattice sums for static-lattice fcc monatomic hydrogen and diatomic $\mathrm{Pa}3$ molecular hydrogen. In the monatomic phase the hydrogenic orbital range is found to closely parallel the inverse Thomas-Fermi wave vector; the corresponding energy $E$ has a minimum of -0.929 Ry/electron at ${r}_{s}=1.67$. For the diatomic phase $E({r}_{s})$ is similar, but the constituent energies, screening, and bond length all reflect a qualitative change in the nature of the solid at ${r}_{s}=2.8$. This change is interpreted in terms of a transition from protons as structural units (at high density) to weakly interacting molecules (at low density). Insensitivity of the total energy to a rapid fall in the bond length suggests association with the rotational transition, where the rigid molecular orientations characteristic of high pressures disappear and the molecules rotate freely at low pressure. The importance of phonons (neglected here) in a correct treatment of the total energy is emphasized, and the possible connection between the rotational transition and metallization of the diatomic phase is discussed. It is concluded that methods which sphericalize the Wigner-Seitz cell may overlook important structural properties (to which the total energy is relatively insensitive) for the diatomic phase.

H Gas: Captured at last?

In the strange world of low‐temperature physics, few more unusual phenomena have been discovered than monatomic hydrogen gas. According to a recent report (New Scientist, Jan. 1981, p. 204), hydrogen atoms do not tend to pair up to form molecules under special low‐temperature‐cryogenic experimental conditions. The reasons for the existence of atomic hydrogen gas at ultra‐low temperature, and for its implications, lie in an understanding of its almost pure quantum mechanical properties. Practical uses of atomic hydrogen will await more knowledge of its properties, but right now, if available in sufficient abundance, atomic hydrogen could be used in maser clocks because it emits highly defined frequencies of microwave radiation at room temperature, and atomic hydrogen gas could be used as an energy conservative fuel, as it recombines to the diatomic molecule. For every recombination between two hydrogen atoms, 4.5 eV of energy are released, which calculates to be over 1 million watts of power per second for 10 grams of atomic hydrogen recombined. The large impulse relative to its light mass could be significant in applications of atomic hydrogen as a rocket fuel. Practical applications aside, the main interest in atomic hydrogen at this moment is in the insight into quantum mechanics that study of its properties may provide. Atomic hydrogen atoms ‘abound throughout the universe,’ even though not on Earth, and thus quantum effects in space, and the hydrogen‐rich planets as well, may be elucidated by results of these studies.

Stable spin‐polarized atomic hydrogen

The strong attraction between hydrogen atoms of opposite electron spin would seem to make it impossible to have stable monatomic hydrogen gas, except in interstellar space. But the force between hydrogen atoms of parallel spin is predominantly repulsive. Isaac Silvera and Jook Walraven of the University of Amsterdam have taken advantage of the absence of bound states for spin‐polarized hydrogen to produce a monatomic hydrogen gas that showed no sign of reverting to ordinary H2 after almost an hour in a high magnetic field at low temperature, despite its very considerable density—more than 1016 atoms/cm3.

Quest for superfluid hydrogen

The possibility of preparing monatomic hydrogen (H1) at high densities seems to have come a stage closer with three papers published in recent issues of Physical Review Letters. Two separate research groups have simultaneously reported the first observations of magnetic resonance from H1 held at liquid helium temperatures: Crampton, Greytak, Kleppner, Phillips, Smith and Weinrib of the Massachusetts Institute of Technology (Phys. Rev. Lett. 42, 1039; 1979); and Hardy, Berlinsky and Whitehead of the: University of British Columbia, Vancouver (op. cit., 1042). On a slightly different tack, Guyer and Miller of the University of Massachusetts, Amherst, have calculated how H1 Imay be expected to interact with a helium coating on the wall of its containing vessel (op. cit., 1754).

Mechanism of hydrogen absorption by lanthanum-nickel (LaNi5)

A model is presented for the mechanism of absorption (or release) of hydrogen by LaNi/sub 5/. The surface of LaNi/sub 5/ is extensively coated by La/sub 2/O/sub 3/. The surface oxide forms in two ways: (1) by reaction of gaseous oxygen with LaNi/sub 5/ or (2) by diffusion of dissolved oxygen to the surface where it reacts with LaNi/sub 5/ to form oxide and precipitate Ni, some of which is also at the surface. Hydrogen reaches the underlying LaNi/sub 5/ by diffusion in monatomic form along the La/sub 2/O/sub 3/--Ni interface. The dissociation of H/sub 2/ at the point of entry into the interfacial region is rate controlling for absorption. Release of hydrogen involves diffusion of monatomic hydrogen along the interface followed by recombination to form molecular hydrogen at the top of the interfacial region. The latter is rate controlling. The model is in accord with the known surface features of the intermetallic and is consistent with the observed kinetics of absorption and desorption of H/sub 2/ by LaNi/sub 5/. It is also consistent with the kinetics of hydrogenation of C/sub 2/H/sub 4/ over LaNi/sub 5/ and LaNi/sub 5/H/sub 2/ /sub 4/. In the latter, interfacial diffusion of monatomic hydrogenmore » is rate controlling. The present model differs from earlier models which regarded either the phase transformation or mass transport through macroscopic cracks of fissures as the rate-controlling step. 2 figures.« less

Passivation of grain boundaries in polycrystalline silicon

Preferential diffusion of various gases down the grain boundaries in polycrystalline silicon is shown to promote significant changes in the density of defect states in these regions. A plasma of monatomic hydrogen provides a significant reduction in both the state density and the accompanying grain-boundary potential barrier while plasmas of oxygen, nitrogen, and sulfur hexafluoride are shown to increase this density of states. Boundaries passivated with hydrogen have as much as a factor of 1000 larger transconductance after treatment. Hydrogenated barriers are stable over long periods at 375 °C and essentially indefinitely at 23 °C. The results have important implications for the development of low-cost thin-film silicon photovoltaic devices.

The initial growth of a radiation driven shock wave

The time development of a radiation driven shick wave is studied from the time of commencement of radiation of Lyman continuum, frequency 3.4 × 10 15 sec −1, onto monatomic hydrogen, till a shock wave was formed. The shock wave was located from the examination of the reduced velocity distribution functions. A relaxation region with a bimodal velocity distribution was found between the shock wave and radiation front. The time development of the macroscopic properties of the atoms, protons and electrons is shown.

Characteristics of Rotationally Stabilized Long Plasma Arcs in a Chamber

An analytical method is developed to determine the gas temperature distribution and the electric field strength-arc length characteristics of a rotationally stabilized long plasma arc in a cylindrical chamber. The application of the method was demonstrated by numerical computations which were carried out for a monatomic hydrogen arc stabilized in a very large chamber. The relationships among the electric field strength, current, arc length, and arc-axis temperature are disclosed.

Energy transfer processes in a partially ionized, two-temperature gas

The elementary situation of convective energy transfer between parallel plates at different temperatures is analyzed for partially ionized, nonreacting, monatomic hydrogen wherein the electrons may be at a temperature different from that of the heavier species. The gas conditions considered are such that an ion sheath, less than a mean free path in spatial extent, forms on the fully catalytic colder surface. The numerical results obtained indicate that 1) the gross features of the continuum solution are rather insensitive to the models of sheath and transition regions employed; 2) the energy transfer between ions and electrons due to the electric field external to the sheath is appreciable, particularly in its effect of reducing electron temperature; 3) thermal nonequilibrium effects on total heat transfer are not as great as might be anticipated because of the energy transfer between species by electric fields and the contribution of diffusional processes; and 4) magnetic field effects on total heat transfer are less than the effect on electronic thermal conductivity would indicate and are further lessened by thermal non equilibrium effects.

Thermodynamic properties of a monatomic hydrogen gas at high temperatures: I. Oppenheim and D.R. Hafemann, J. Chem. Phys., 39 (1), 1 July 1963, 101–109

Thermodynamic properties of a monatomic hydrogen gas at high temperatures: I. Oppenheim and D.R. Hafemann, J. Chem. Phys., 39 (1), 1 July 1963, 101–109

Thermodynamic Properties of a Monatomic Hydrogen Gas at High Temperatures

A study is made of a gas in which the internal and intermolecular degrees of freedom are not separable. Expressions for the partition function and thermodynamic properties are derived for a gas of monatomic hydrogen. The number of bound states of the system is limited by interactions between the hydrogen atoms. The potentials of interaction of hydrogen atoms with protons, electrons, and other hydrogen atoms are estimated, and the partition function is evaluated at a series of densities from 10 to 10—5 amagats. The occupation numbers of bound states and the percent ionization are changed significantly by considering atom—atom and atom—proton interactions, but the value of the partition function is only slightly changed relative to that calculated by considering only the effect of interatomic forces upon the single-atom energies.

中性子スペクトルに及ぼすプルトニウム蓄積の影響

Wigner-Wilkins have analytically calculated the neutron spectrum in an infinitely large monatomic hydrogen gas moderator in which the absorption cross section has the usual inverse dependence on velocity, v. The above analytical methods were found to be not always applicable. A calculation is given for the neutron spectum in a monatomic hydrogen gas moderator which contains hypethetically a large amount of Pu/sup 239/ absorber or l/v law dependent absorber. The calculation is based on the assumptions that the temperature of the moderator T = 581 deg K, the scattering cross section of hydrogen is constant (50 barn), and the ratio of the number of atoms of Pu/sup 239/ or l/v law absorber to the hydrogen atoms are 0, 0.01, and 0.02. When the moderator contains no Pu/sup 239/. the distribution of the neutron velocities is approximately Maxwellian. However, when the concentration is 0.01 or 0.02, the spectrum is shifted in the direction of higher energies, i.e., the spectrum is hardened. There is a pronounced dip at the 0.3 ev resonance of Pu/sup 239/. In the case of the l/v law absorber, the distribution is Wigner-Wilkins spectrum and the spectrum is shifted in the direction of higher energies. (auth)

Effects of Low-Lying Europium Resonances on the Temperature Defect in Water-Moderated Reactors

The selection of appropriate epithermal group-averaged cross sections for use in a few-group criticality calculation is particularly difficult when resonance absorbers are present. However, by use of the SOFOCATE code for the calculation of thermal spectra in hydrogenous media, it is now practical to include low-lying resonances below 2 ev in the thermal group. Since the SOFOCATE code, which is based on the Wigner-Wilkins differential equation for monatomic hydrogen thermalization, has yielded good agreement with measured spectra in water, it is felt that use of this code and inclusion of low-lying resonances in the thermal group constitute a more accurate and convenient method of treating these resonances than other procedures. As an application of the method, a study has been made of some of the effects associated with the use of Eu as a means of reducing the temperature defect in water-moderated reactors. It is shown that the use of natural, unshielded Eu would reduce the temperature defect provided the spectral hardening introduced by the core absorption is sufficiently small. It is also shown that the strong dependence on spectral hardening is due to the presence of the Eu resonances at about 0.4 ev.

THE ELECTRODE BEHAVIOR OF MERCURY

Mercury electrode potentials in N/5 sulphuric acid were unaffected when the electrolyte was saturated with hydrogen, nitrogen, or helium but were markedly affected by trace amounts of oxygen or mercury ions. In the absence of oxygen and mercury ions, a constant potential of −0.61 volt (relative to a saturated calomel electrode) was observed. When current was passed for the first time across a fresh electrode face immersed in oxygen-free electrolyte (i.e. from initial potentials of about −0.6l volt), the potential build-up was nonlinear, but subsequent passage of current gave a linear build-up of potential. With traces of oxygen present, differences in the two types of curves were masked by reactions that appeared to involve oxygen or oxide on the electrode surface. The initial build-up curve was ascribed to the deposition of a monatomic hydrogen film (one atom per metal atom in the surface). The potential build-up curves probably result from a number of simultaneous reactions at the electrode.

Attempts at Obtaining Excitation of an Atomic Beam of Monatomic Hydrogen

Attempts at Obtaining Excitation of an Atomic Beam of Monatomic Hydrogen

Over-Voltage and Monatomic Hydrogen

Over-Voltage and Monatomic Hydrogen