scholarly journals The adsorption of hydrogen on the surface of an electrodeless discharge tube

1929 ◽  
Vol 123 (792) ◽  
pp. 603-613 ◽  
Keyword(s):  
High Temperature ◽  
Discharge Tube ◽  
Direct Evidence ◽  
Adsorbed Layer ◽  
Electric Discharges ◽  
Hydrogen Atoms ◽  
Electrodeless Discharge ◽  
Tungsten Filaments ◽  
Order Of Magnitude ◽  
Permanent Gases

It is well known that the pressure of hydrogen in a perfectly sealed vessel can be permanently decreased under the action of electric discharges; this is most marked when the vessel is in liquid air, but we shall here be concerned with its occurence at ordinary temperatures. Since considerable dissociation of hydrogen accompanies any discharge, this loss of pressure is intelligible by analogy with Langmuir’s experiments on hot tungsten filaments. In these he shows that hydrogen atoms dissociated at the high temperature cease to contribute to gas pressure if they reach the walls of the vessel, since they are strongly adsorbed on glass, whose adsorption of ordinary diatomic hydrogen is negligible. Langmuir states that data are of the order of magnitude for the adsorbed layer to be of monomolecular thickness. The concept of a monomolecular adsorbed layer has been much used since, sometimes with the further assumption that it constitutes a closely packed sheet of atoms, but for the permanent gases the evidence for its existence is not conclusive. It is opposed to Freundlich’s view of adsorption, and Evans and George and others have given direct evidence of multimolecular layers of several gases on glass.

Very high hole concentrations in C-doped InGaAs using new sources with APOMVPE

1997 ◽  
Vol 485 ◽  
Author(s):  
A. Tandon ◽  
R. M. Cohen
Keyword(s):  
High Temperature ◽  
Structural Change ◽  
Carrier Concentration ◽  
Hole Concentration ◽  
X Ray Diffraction ◽  
Hydrogen Atoms ◽  
Carbon Doped ◽  
High Temperature Anneal ◽  
Order Of Magnitude ◽  
P Type

AbstractNew sources have been used to grow the first carbon doped, highly p-type InxGa1-xAs (0.2>x>0.7) epilayers on InP substrates by atmospheric pressure organometallic vapor phase epitaxy (APOMVPE). Excellent morphology was obtained simultaneously with high hole concentrations at growth temperatures near 450 °C. High hole concentrations of 1.6×1019 – 8.7×1019 cm−3 (the highest reported to date for APOMVPE), and the corresponding room temperature hole mobilities of 65 – 25 cm2/s, respectively, have been obtained from Hall measurements. X-ray diffraction is consistent with excellent crystal quality. Annealing at temperatures of T=400–500 °C in the presence of either nitrogen or hydrogen was found to change the carrier concentration by only 0–15%. However, after annealing at T=650 °C, irreversible changes occurred in the InGaAs. After a high temperature anneal, reversible order of magnitude changes in the hole concentration was obtained upon further annealing at low temperatures, depending upon the ambient. These results conclusively show that hydrogen does not passivate C acceptor ions in InGaAs. Since changes in the carrier concentration become substantial and reversible only after high temperature annealing, the results strongly suggest that a structural change occurred in the crystal at high temperatures. We consider it likely that this structural change is the precipitation of carbon out of a supersaturated solid solution, and that hydrogen atoms associated with these precipitates act as donors which compensate the hole concentration.

A controller for safe, convenient operation of LaB6 emitters on electron-beam instruments

1983 ◽  
Vol 41 ◽  
pp. 408-409
Author(s):  
W. J. Abramson ◽  
H. W. Estry ◽  
L. F. Allard
Keyword(s):  
Electron Beam ◽  
Control System ◽  
Thermal Shock ◽  
Appropriate Care ◽  
Electron Guns ◽  
Tungsten Filaments ◽  
Order Of Magnitude ◽  
Main Components

LaB6 emitters are becoming increasingly popular as direct replacements for tungsten filaments in the electron guns of modern electron-beam instruments. These emitters offer order of magnitude increases in beam brightness, and, with appropriate care in operation, a corresponding increase in source lifetime. They are, however, an order of magnitude more expensive, and may be easily damaged (by improper vacuum conditions and thermal shock) during saturation/desaturation operations. These operations typically require several minutes of an operator's attention, which becomes tedious and subject to error, particularly since the emitter must be cooled during sample exchanges to minimize damage from random vacuum excursions. We have designed a control system for LaBg emitters which relieves the operator of the necessity for manually controlling the emitter power, minimizes the danger of accidental improper operation, and makes the use of these emitters routine on multi-user instruments.Figure 1 is a block schematic of the main components of the control system, and Figure 2 shows the control box.

scholarly journals Study of spider pulsar binary eclipses and discovery of an eclipse mechanism transition

2020 ◽  
Vol 494 (2) ◽  
pp. 2948-2968 ◽  
Author(s):  
E J Polzin ◽  
R P Breton ◽  
B Bhattacharyya ◽  
D Scholte ◽  
C Sobey ◽  
...  
Keyword(s):  
Direct Evidence ◽  
Low Frequency ◽  
Line Of Sight ◽  
Observational Constraints ◽  
Main Body ◽  
Theoretical Studies ◽  
Wide Range ◽  
Order Of Magnitude ◽  
Mechanism Transition ◽  
Hubble Time

ABSTRACT We present a comparative study of the low-frequency eclipses of spider (compact and irradiating binary) PSRs B1957+20 and J1816+4510. Combining these data with those of three other eclipsing systems we study the frequency dependence of the eclipse duration. PSRs B1957+20 and J1816+4510 have similar orbital properties, but the companions to the pulsars have masses that differ by an order of magnitude. A dedicated campaign to simultaneously observe the pulsed and imaged continuum flux densities throughout the eclipses reveals many similarities between the excess material within the two binaries, irrespective of the companion star properties. The observations show that the pulsar fluxes are removed from the line of sight throughout the main body of the eclipses. For PSR J1816 + 4510, we present the first direct evidence of an eclipse mechanism that transitions from one that removes the pulsar flux from the line of sight to one that merely smears out pulsations, and claim that this is a consequence of scattering in a tail of material flowing behind the companion. Inferred mass-loss rates from the companion stars are found to be $\dot{M}_{\text{C}} \sim 10^{-12}$ and $\sim 2 \times 10^{-13}\,\mathrm{M}_\odot$ yr−1 for PSR B1957+20 and PSR J1816 + 4510, respectively; seemingly too low to evaporate the stars within Hubble time. Measurements of eclipse durations over a wide range of radio frequencies show a significant dependence of eclipse duration on frequency for all pulsars, with wider eclipses at lower frequencies. These results provide a marked improvement in the observational constraints available for theoretical studies of the eclipse mechanisms.

Reaction of atomic hydrogen with tetrafluoroethene

1969 ◽  
Vol 47 (10) ◽  
pp. 1696-1698
Author(s):  
Lei Teng ◽  
W. E. Jones
Keyword(s):  
Electric Discharge ◽  
Discharge Tube ◽  
Atomic Hydrogen ◽  
Hydrogen Atoms

Hydrogen atoms, generated in a Wood's electric discharge tube, were allowed to react with tetrafluoroethene. The products of the reaction were found to be HF, C2F3H, C2H2, C2F2H2, C2F4H2, C2FH3, C2H4, and CHF3. The formation of the products with the exception of HF was studied quantitatively from 30–330 °C.

Structural transitions and electrical conductivity of C60 films at high temperature

1996 ◽  
Vol 11 (8) ◽  
pp. 2071-2075 ◽  
Author(s):  
Jinlong Gong ◽  
Guobin Ma ◽  
Guanghua Chen
Keyword(s):  
Electrical Conductivity ◽  
High Temperature ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Energy Band Gap ◽  
Defect States ◽  
Order Of Magnitude ◽  
Fcc Phase ◽  
New Phase ◽  
C60 Films

X-ray diffraction analysis on C60 films shows that besides fcc phase, there also exists hcp phase, as well as a new crystalline phase with interplanar spacing (d-spacing) of planes parallel to the substrate 0.95 nm. The new phase may relate to the intercrystalline packed C60 molecules between fcc crystallites. The room temperature electrical conductivity of C60 films is found to be in the range of 10−5–10−8 (Ω · cm)−1. The room temperature conductivities of C60 films annealed at temperatures above 473 K are lower by one order of magnitude than those at temperatures below 463 K. This is because the interconnection between the fcc crystallites is weakened due to the disappearance of the new intercrystalline phase and the subsequent heightening of the intercrystalline potential barrier. From the measurement on the conductivity versus time when the film is maintained at a constant temperature, we identified the increase of conductivity is the result of the decrease of hcp phase, while the decrease of conductivity is due to the decrease of the new intercrystalline phase. Because the structures of the films become highly ordered, and defect states in the energy band gap decrease on annealing at high temperature, the conductivity activation energy increases.

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