THE DECAY OF THE POPULATIONS OF METASTABLE ATOMS AND IONS FROM THE SAME D-C. DISCHARGE IN NEON

1957 ◽  
Vol 35 (8) ◽  
pp. 941-953 ◽  
Author(s):  
B. C. Blevis ◽  
J. M. Anderson ◽  
R. W. McKay
Keyword(s):  
Pressure Range ◽  
Principal Factor ◽  
Measurable Effect ◽  
Population Changes ◽  
Electron Population ◽  
Diffusion Constants ◽  
Ion Recombination ◽  
Low Pressures ◽  
Limits Of Error ◽  
Positive Ion

Measurements of electron density and of the population of the 3P2 metastable state have been made following cessation of a d-c. discharge in neon gas. Determinations of these populations were made under identical conditions at accurately determined times after termination of the discharge and decay curves were plotted for a pressure range from 0.5 to 12.0 mm. Hg. At low pressures, where diffusion is the principal factor in the decay, both curves are exponential and show the same mean life, within the limits of error. Values of the diffusion constants obtained from these curves are consistent with the results of previous workers in both fields. At higher pressures the metastable decay remains exponential while the reciprocal of the electron population changes linearly with time. In general, the two decays are unrelated. Only at the highest pressure studied, and in this case for only the first half millisecond, was a measurable effect of positive ion recombination found in the metastable population curve.

Duration of energy storage following a discharge in xenon

1970 ◽  
Vol 48 (15) ◽  
pp. 1817-1829 ◽  
Author(s):  
P. R. Timpson ◽  
J. M. Anderson
Keyword(s):  
Diffusion Coefficient ◽  
Energy Storage ◽  
Metastable State ◽  
Exponential Decay ◽  
Resonance Line ◽  
High Pressures ◽  
Ambipolar Diffusion ◽  
Ion Recombination ◽  
Low Pressures ◽  
Positive Ion

It has been shown that the afterglow following a discharge in xenon consists of two parts: (1) the resonance line, whose intensity initially decays exponentially in agreement with Holstein's theory; (2) an accompanying distributed radiation, experimentally a continuum, extending to about 1900 a.u. The intensity of this continuum decays exponentially at the same rate as the population of the lower metastable state at all wavelengths and each pressure studied. All departures from an exponential decay seem to be caused by repopulation of states by ionic recombination and are current dependent. Electron disappearance is due to ambipolar diffusion at low pressures and ion recombination at high pressures. The value of the ambipolar diffusion coefficient indicates that the afterglow positive ion is Xe2+ for pressures greater than 0.3 Torr. No phenomena which could be due to interchange of population between metastable states have been found in xenon.

Low-pressure superconductivity in lithium-doped methane predicted by first principles

2020 ◽  
pp. 2150032
Author(s):  
Ning Lu ◽  
Yu-Long Hai ◽  
Hai-Yan Lv ◽  
Wen-Jie Li ◽  
Chun-Lei Yang ◽  
...  
Keyword(s):  
Charge Transfer ◽  
High Temperature ◽  
Crystal Field ◽  
First Principles ◽  
Pressure Range ◽  
High Temperature Superconductor ◽  
Low Pressure ◽  
First Principles Calculations ◽  
A Charge ◽  
Low Pressures

To explore the high-temperature superconductor at low pressures, we have investigated the crystal structures, electronic properties, and possible superconductivity in the case of methane (CH4) doped by lithium in the pressure range of [Formula: see text][Formula: see text]GPa, based on the first-principles calculations. The results show that Li-intercalated CH4 (Lix(CH4)[Formula: see text]) can realize metallization and superconductivity at low pressures, even 5[Formula: see text]GPa. We find that there is a charge transfer between Li and CH4, but the metallization is driven by the change of crystal field induce by doping instead of charge transfer. The critical temperture is predicted from 3.8[Formula: see text]K at 5[Formula: see text]GPa for LiCH4 to 12.1[Formula: see text]K at 100[Formula: see text]GPa for Li(CH4)4. The low-pressure superconductivity of Lix(CH4)[Formula: see text] can be further optimized by adjusting component and pressure.

THE LOSS OF FREE ELECTRONS IN IRRADIATED AIR

1963 ◽  
Vol 41 (4) ◽  
pp. 625-631 ◽  
Author(s):  
B. G. Young ◽  
A. W. Johnson ◽  
J. A. Carruthers
Keyword(s):  
High Pressures ◽  
Irradiation Time ◽  
High Energy ◽  
Free Electrons ◽  
Loss Mechanism ◽  
High Energy Electrons ◽  
Ion Recombination ◽  
Three Body ◽  
Microwave Probe ◽  
Low Pressures

The loss of free electrons in air, nitrogen, and oxygen is studied as a function of pressure by continuously irradiating the gases with high-energy electrons and measuring the equilibrium electron densities with a microwave probe. At low pressures (1–10 mm Hg) electrons are lost by free diffusion to the chamber walls before cooling. At intermediate pressures (10–100 mm Hg) electrons cool rapidly without loss to thermal energy and then disappear by three-body attachment in air and oxygen, and by electron–ion recombination in nitrogen. At high pressures (100–1000 mm Hg) the electron density increases with irradiation time and the controlling loss mechanism is uncertain.

scholarly journals Towards the “Pressure and Materials Gap”: Hydrogenation of Acrolein Using Silver Catalysts

2004 ◽  
Vol 218 (4) ◽  
pp. 405-424 ◽  
Author(s):  
M. Bron ◽  
E. Kondratenko ◽  
A. Trunschke ◽  
P. Claus
Keyword(s):  
Allyl Alcohol ◽  
Pressure Range ◽  
Hydrogen Adsorption ◽  
Structural Features ◽  
Support Material ◽  
Silver Catalysts ◽  
Partial Pressures ◽  
Structure Sensitive ◽  
Low Pressures ◽  
Electrolytic Silver

AbstractThe hydrogenation of acrolein has been studied over various Ag/SiO2 catalysts in a pressure range from 50mbar to 20bar. Increasing partial pressures of acrolein and/or hydrogen lead to increasing selectivities of allyl alcohol. The selectivity towards allyl alcohol also depends on the structural features of the Ag/SiO2 catalyst. Larger particles seem to favour the production of propanal. This observation is discussed in view of the different plane-to-edge-ratio of the different catalysts. The interaction of hydrogen with silver samples has been studied with TAP at very low pressures as well as with calorimetry at ambient pressures. Both methods indicate, that also the hydrogen adsorption is structure-sensitive. No interaction of hydrogen with electrolytic silver or the support material alone was observed. IR spectroscopy has been used to elucidate the interaction of acrolein with Ag/SiO2 catalysts. A strong interaction with the support material was found, hindering the observation of probable silver-acrolein interaction.

scholarly journals Mobility of the positive and negative ions in gases at high pressure

1912 ◽  
Vol 86 (584) ◽  
pp. 154-162 ◽  
Keyword(s):  
High Pressure ◽  
High Pressures ◽  
Mathematical Expression ◽  
Negative Ions ◽  
Negative Ion ◽  
Positive Ions ◽  
Low Pressures ◽  
Positive Ion ◽  
Reduced Pressures

The velocity of ions in gases at reduced pressures was first investigated by Rutherford and by Langevin. Recently the author and others have carried out similar investigations. The results of these investigations show that for the negative ions in air the product of the mobility and the pressure is constant for pressures ranging from 760 mm. to 200 mm. of mercury, but with further reduction the product increases with the reduction of pressure, this increase becoming very great at low pressures. For the positive ions in air the product of the mobility and pressure is constant for pressures investigated between 760 mm. and 3 mm. of mercury. Similar results were obtained for the mobilities of the ions in other gases. The results show that if the ion is an aggregation of molecules, this aggregation becomes, at low pressures, less complex in the ease of the negative ion, while in the ease of the positive ion it persists down to 3 mm. of mercury. The purpose of the present research was the study of the mobilities of both kinds of ions in gases at high pressures. The method of investigation is based on the mathematical expression, developed by Prof. Rutherford, for the current between two plates, assuming that a very intense ionisation exists near the surface of one of the electrodes.

The X-radiolysis of water vapor containing methanol. Effects of some electron and hydrogen atom scavengers

1968 ◽  
Vol 46 (12) ◽  
pp. 1957-1964 ◽  
Author(s):  
R. S. Dixon ◽  
M. G. Bailey
Keyword(s):  
Nitrous Oxide ◽  
Water Vapor ◽  
Carbon Tetrachloride ◽  
Hydrogen Atom ◽  
Sulfur Hexafluoride ◽  
Hydrogen Yield ◽  
Hydrogen Atoms ◽  
A Value ◽  
Ion Recombination ◽  
Positive Ion

The X-radiolysis of water vapor containing methanol at 125 °C and 1 atm pressure has been studied alone and in the presence of some electron and hydrogen atom scavengers. In water vapor containing methanol only, a plateau value G(H2) = 7.9 ± 0.3 is obtained at all methanol concentrations above 0.5 mole %. Addition of propylene drastically reduces this yield due to efficient scavenging of hydrogen atoms, and values for the total number of H atoms from all precursors g(H)t = 7,5 ± 0.2 and [Formula: see text] are deduced from the competition. An unscavengeable hydrogen yield g(H2) ~ 0.5 is also indicated in mixtures containing propylene. Nitrous oxide and sulfur hexafluoride are found to scavenge electrons efficiently in water vapor containing methanol and the number of hydrogen atoms arising from electron–positive ion recombination is estimated to have a value G = 2.2 ± 0.6. The number of hydrogen atoms arising from processes not involving electrons is g(H) = 5.2 ± 0.3. Carbon tetrachloride reacts efficiently with both electrons and hydrogen atoms, with k(H + CH3OH)/k(H + CCl4) = 0.085. Values of g(H) = 4.9 ± 0.5 and g(H2) = 0.8 ± 0.2 are deduced from mixtures containing carbon tetrachloride.

Responses of Pests to Fumigation. VI.—Water Losses and the Mortality of Calandra Spp. at reduced Pressures

1956 ◽  
Vol 47 (4) ◽  
pp. 749-753 ◽  
Author(s):  
H. J. Bhambhani
Keyword(s):  
Water Loss ◽  
Pressure Range ◽  
High Humidity ◽  
Physical Change ◽  
Water Losses ◽  
Mortality Response ◽  
Relative Humidity Range ◽  
Low Pressures ◽  
Humidity Range ◽  
Reduced Pressures

The water loss and mortality of Calandra granaria (L.) and C. oryzae (L.) have been studied at low pressures in controlled humidities. The mortality of both species is closely associated with the loss of water under these conditions, a loss which is prevented by a high humidity in the surrounding air. C. oryzae is consistently more susceptible than C. granaria. Substantially linear relations were observed between water loss and decreasing relative humidity (range 0–85%), increasing period of exposure (range 4–16 hr.), and decreasing pressure (range 2–8 cm. mercury). At lower pressures (3–4 mm. mercury), the Water loss and mortality of both species were greatly reduced, suggesting that some physical change had occurred in the insects. A covariance analysis of the mortality response, using the loss of water as a concomitant variate, showed that there was no significant part of the mortality that was not accounted for by the water loss from the insects.

The effects produced by positive ion bombardment of solids: metallic ions

1928 ◽  
Vol 24 (3) ◽  
pp. 451-469 ◽  
Author(s):  
M. L. Oliphant ◽  
E. Rutherford
Keyword(s):  
Ion Bombardment ◽  
The Self ◽  
Metallic Ions ◽  
Positive Ions ◽  
Preliminary Account ◽  
Energy Relations ◽  
Low Pressures ◽  
Positive Ion ◽  
Sustained Discharge ◽  
Made In

The following is a preliminary account of experiments made in an attempt to obtain information about the relation between the energy of a positive ion and the effect produced on a surface which it bombards. The energy relations which hold in collisions between rapidly moving positive ions and the molecules of a gas or of a solid are of extreme importance in the theory of gaseous discharges at low pressures, in particular of the initiation of the self-sustained discharge.

THE EFFECT OF AN ARRAY OF OBSTACLES ON HEAT CONDUCTION IN GASES

1963 ◽  
Vol 41 (11) ◽  
pp. 1883-1894
Author(s):  
C. F. Mate
Keyword(s):  
Heat Conduction ◽  
Pressure Range ◽  
Cell Model ◽  
Temperature Data ◽  
Obstacle Array ◽  
Helium Gas ◽  
Wide Pressure Range ◽  
A Cell ◽  
Low Pressures ◽  
Wide Pressure

The main features of heat conduction in an obstructed gas are described with the help of a cell model of the obstacle array. An expression is derived for calculation of the average conductivity of the obstructed gas over a wide pressure range extending to indefinitely low pressures. Conductivities calculated from this expression are compared with low-temperature data for helium gas in powdered alumina. The relevant transport properties of gases are summarized in an appendix.

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