Effect of Electric Field Strength on the Free Ion Yields in the X-Radiolysis of Liquids: Influence of Molecular Structure and Temperature

1972 ◽  
Vol 50 (11) ◽  
pp. 1617-1626 ◽  
Author(s):  
J.-P. Dodelet ◽  
P. G. Fuochi ◽  
G. R. Freeman
Keyword(s):  
Field Strength ◽  
Liquid Argon ◽  
Separation Distance ◽  
Relative Increase ◽  
Distribution Functions ◽  
Electron Pairs ◽  
Gaussian Distribution Function ◽  
Free Ion ◽  
Liquid Methane ◽  
Ion Yields

The relative increase in the free ion yield with increasing field strength E, expressed as [Formula: see text] is smaller when the following quantities are larger: (1) dielectric constant, (2) temperature, and (3) separation distance between the geminate ion–electron pairs. The field dependence [Formula: see text] equals 9.7/εT2 cm/V at low E, but at higher fields it is affected by the above three factors and by E itself. Results obtained from the liquids propane (123–233 °K), 2-methylpropane (isobutane, 148–294 °K), 2,2-dimethylpropane (neopentane, 295 °K), argon (87 °K), oxygen (87 °K) and argon–oxygen solutions (87 °K) are presented and analyzed according to a theoretical model. Several types of ion–electron separation (y) distribution functions are tested. Within the framework of the model a power function F(> y) = yminy−x with x < 4 provides a good interpretation of the results when [Formula: see text] a Gaussian distribution function provides the best interpretation of the field effects when [Formula: see text] Either the y distribution has a Gaussian core with a more gently sloping tail, or distributions are more Gaussian-like in liquids in which the electron ranges are greater. The electron range in pure argon (b = 1300 Å) is much smaller than had been expected and is only 2.6 times greater than that in liquid methane (b = 500 Å at 120 °K). Phonon emission by 10–0.01 eV electrons in liquid argon may be relatively efficient and might involve transient states of the type [Formula: see text]

Low energy electron ranges in liquids: determination by nonhomogeneous kinetics

1977 ◽  
Vol 55 (11) ◽  
pp. 2050-2062 ◽  
Author(s):  
J.-P. Dodelet
Keyword(s):  
Critical Temperature ◽  
Melting Point ◽  
Distribution Functions ◽  
Liquid Density ◽  
Range Distribution ◽  
Total Ionization ◽  
Free Ion ◽  
Drastic Increase ◽  
Pass Through ◽  
Ion Yields

Free ion yields have been measured in four hydrocarbon liquids: n-pentane, cyclopentane, neopentane, and neohexane. Each liquid has been studied from room temperature or below up to the critical temperature. Theoretical curves have been calculated using the relation between the free ion yields and the external field strength derived by Terlecki and Fiutak on the basis of an equation by Onsager. Two popular electron range distribution functions, Gaussian and exponential, have been shown not to be an adequate representation of the reality as far as the model used for the calculations is concerned. In order to fit experimental points, both range distribution functions would require a drastic increase in the total ionization yield, Gtot, with temperature increase. This would mean an unrealistic decrease of the ionization potential of the molecule from the melting point up to the critical temperature.It is possible to keep Gtot quite constant and within the range of values obtained by other techniques by extending the Gaussian range distribution function with a (range)−3 probability tail. The most probable range can be normalized for the liquid density. This parameter has been used to obtain information about the behaviour of epithermal electrons in the four alkane liquids from the melting point up to the critical temperature.(1) Normalized penetration ranges of epithermal electrons are dependent on the structure of the molecule in the entire liquid range but differences are smaller at critical than at low temperatures.(2) Normalized penetration ranges of epithermal electrons pass through a maximum in the liquid phase for neopentane, neohexane, and cyclopentane. No maximum is observed for n-pentane.(3) There is no drastic change in the behaviour of epithermal electrons in these alkanes at the critical temperature.

X-Radiolysis Ion Yields and Electron Ranges in Liquid Xenon, Krypton, and Argon: Effect of Electric Field Strength

1973 ◽  
Vol 51 (5) ◽  
pp. 641-649 ◽  
Author(s):  
Maurice G. Robinson ◽  
Gordon R. Freeman
Keyword(s):  
Field Strength ◽  
Gas Phase ◽  
Electric Fields ◽  
Zero Field ◽  
Energy Effect ◽  
Secondary Electrons ◽  
Total Ionization ◽  
Field Dependent ◽  
Free Ion ◽  
Ion Yields

X-Radiolysis ion yields were measured at electric fields between 1 and 60 kV/cm in argon at 87 °K, krypton at 148 °K, and xenon at 183 °K. The results were analyzed according to a theoretical model to obtain the total ion yields Gtot,the free ion yields at zero field strength Gfi0 and the most probable penetration ranges b of the secondary electrons in the liquids. The respective values were: Ar, 7.3, 2.9, 1330 Å; Kr, 13.0, 5.8, 880 Å; Xe, 13.7, 7.0, 720 Å. The total ionization yields in these substances are greater in the liquid than in the gas phase, probably due to smaller ionization potentials in the condensed phase (polarization energy effect). Field dependent electron mobilities are also reported.

Electron thermalization-distance distributions in electron-attaching fluids

1990 ◽  
Vol 68 (9) ◽  
pp. 930-934 ◽  
Author(s):  
Norman Gee ◽  
Gordon R. Freeman
Keyword(s):  
Carbon Monoxide ◽  
Field Strength ◽  
Electric Field ◽  
Carbon Disulfide ◽  
Sharp Decrease ◽  
Liquid Carbon ◽  
Distance Distributions ◽  
Free Ion ◽  
Ion Yields ◽  
Liquid Carbon Disulfide

The electron ejected from a molecule by an energetic impact moves away from the resultant ion and loses energy to the molecules with which it collides. The distance such electrons travel away from their ions during thermalization can be estimated by measuring the free-ion yields as a function of electric-field strength. This was done in gaseous and liquid carbon disulfide and hexafluorobenzene over wide ranges of densities. The electron thermalization-distance distribution in C6F6 was the same as that in most other liquids; it was a Gaussian distribution with a power tail. However in liquid CS2 the distribution was different, an exponential with a power tail, as in liquid nitrogen and liquid carbon monoxide. The different distributions reflect differences in the thermalization processes. The thermalizing ability of both CS2 and C6F6 is less in the liquid than in the gas. There is an especially sharp decrease in the thermalizing ability of CS2 at the highest densities.

Behavior of Extra Electrons in the Liquids Methane, Ethane, and Propane

1971 ◽  
Vol 49 (6) ◽  
pp. 984-985 ◽  
Author(s):  
M. G. Robinson ◽  
P. G. Fuochi ◽  
G. R. Freeman
Keyword(s):  
Field Strength ◽  
Ion Pairs ◽  
Liquid Argon ◽  
Low Field ◽  
Electrical Conductances ◽  
Radiation Induced ◽  
Liquid Methane ◽  
Field Strengths

The radiation induced electrical conductances of liquids methane, ethane, and propane have been measured. At a field strength of 5 kV/cm the number of ion pairs collected at the electrodes per 100 eV absorbed by the liquid was 1.5 in methane (−160°), 0.20 in ethane (−90°), and 0.14 in propane (−90°). The short-lived conductance transient (k/u overshoot) observed at low field strengths in methane was 40% as large as that in argon. No transient was observable in ethane or propane. The freeness of motion of electrons in liquid methane is nearly as great as that in liquid argon and much greater than that in ethane or propane.

scholarly journals Residues in a Jellyfish Shaker-Like Channel Involved in Modulation by External Potassium

1999 ◽  
Vol 82 (4) ◽  
pp. 1740-1747 ◽  
Author(s):  
Nikita G. Grigoriev ◽  
J. David Spafford ◽  
Andrew N. Spencer
Keyword(s):  
Potassium Channels ◽  
Field Strength ◽  
Binding Site ◽  
Weak Field ◽  
Relative Increase ◽  
Inactivation Rate ◽  
Side Chain ◽  
Kinetic Measurements ◽  
Inactivation Curve ◽  
Peak Current

The jellyfish gene, jShak2, coded for a potassium channel that showed increased conductance and a decreased inactivation rate as [K+]out was increased. The relative modulatory effectiveness of K+, Rb+, Cs+, and Na+ indicated that a weak-field-strength site is present. Cysteine substituted mutants (L369C and F370C) of an N-terminal truncated construct, ( jShak2Δ2–38) which only showed C-type inactivation, were used to establish the position and nature of this site(s). In comparison with jShak2Δ2–38 and F370C, L369C showed a greater relative increase in peak current when [K+]out was increased from 1 to 100 mM because the affinity of this site was reduced at low [K+]out. Increasing [K+]out had little effect on the rate of inactivation of L369C; however, the appearance of a second, hyperbolic component to the inactivation curve for F370C indicated that this mutation had increased the affinity of the low-affinity site by bringing the backbone oxygens closer together. Methanethiosulphonate reagents were used to form positively (MTSET), negatively (MTSES), and neutrally (MTSM) charged side groups on the cysteine-substituted residues at the purported K+ binding site(s) in the channel mouth and conductance and inactivation kinetic measurements made. The reduced affinity of the site produced by the mutation L369C was probably due to the increased hydrophobicity of cysteine, which changed the relative positions of carbonyl oxygens since MTSES modification did not form a high-field-strength site as might be expected if the cysteine residues project into the pore. Addition of the side chain -CH2-S-S-CH3, which is similar to the side chain of methionine, a conserved residue in many potassium channels, resulted in an increased peak current and reduced inactivation rate, hence a higher affinity binding site. Modification of cysteine substituted mutants occurred more readily from the inactivated state confirming that side chains probably rotate into the pore from a buried position when no K ions are in the pore. In conclusion we were able to show that, as for certain potassium channels in higher taxonomic groups, the site(s) responsible for modulation by [K+]out is situated just outside the selectivity filter and is represented by the residues L369and F370 in the jellyfish Shaker channel, jShak2.

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