Comparison between Molecular Structure Effects in Triplet Positronium Annihilation Rates and Radiolysis Free Ion Yields in Liquid Hydrocarbons

1972 ◽  
Vol 50 (16) ◽  
pp. 2697-2698 ◽  
Author(s):  
G. R. Freeman ◽  
J.-P. Dodelet
Keyword(s):  
Molecular Structure ◽  
Chain Length ◽  
Molecular Interaction ◽  
Half Life ◽  
Density Effect ◽  
Liquid Hydrocarbons ◽  
Positronium Annihilation ◽  
Free Ion ◽  
Alkane Chain ◽  
Ion Yields

Two seemingly unrelated phenomena in liquid hydrocarbons have similar trends in their dependences upon the molecular structure of the hydrocarbon. The phenomena are the annihilation half-life of triplet positronium and the radiolysis free ion yield. In n-alkanes the effect of increasing the molecular chain length, upon both phenomena, appears to be simply to increase the density of interacting sites. Branching the alkane chain decreases the strength of molecular interaction with both electrons and positronium, although the relative decrease is much greater for the former than for the latter. The effects of double bonds on the phenomena, after separating out the density effect, are different from each other.

Electron mobility, free ion yields, and electron thermalization distances in n‐alkane liquids: Effect of chain length

1988 ◽  
Vol 89 (6) ◽  
pp. 3710-3717 ◽  
Author(s):  
Norman Gee ◽  
P. Chandani Senanayake ◽  
Gordon R. Freeman
Keyword(s):  
Chain Length ◽  
Electron Mobility ◽  
Free Ion ◽  
Ion Yields

The effect of pressure on the radiation-induced conductance of liquid hydrocarbons

1969 ◽  
Vol 47 (6) ◽  
pp. 885-892 ◽  
Author(s):  
D. W. Brazier ◽  
G. R. Freeman
Keyword(s):  
Solid Phase ◽  
The Other ◽  
Electron Localization ◽  
Cavity Model ◽  
Liquid Hydrocarbons ◽  
Appreciable Increase ◽  
Free Ion ◽  
Radiation Induced ◽  
Phase Glass ◽  
Ion Yields

An attempt was made to test the cavity model of electron localization in liquid hydrocarbons by measuring the effect of pressures up to 4000 bars on the radiation induced conductance of n-pentane, n-hexane, n-octane, cyclopentane, methylcyclohexane, and 2,2-dimethylbutane at 30°. Measurements at 3 and 56° were also made on n-hexane and n-octane. The relative induced conductance, i.e. the ratio of the induced conductance at pressure p to that at 1 bar, decreased with increasing pressure. The amount of decrease was slightly greater at low than at high temperatures. The behavior of 2,2-dimethylbutane was complex and is not understood. For the other liquids, it was concluded that the free ion yields remained constant or decreased somewhat with increasing pressure. An appreciable increase in the free ion yields, which is a possible implication of the cavity model of electron localization, did not occur. Therefore, either (a) the cavity model of electron localization in hydrocarbons is wrong, or (b) application of pressures up to 4000 bars did not appreciably alter the cavity concentrations in the liquids. Perhaps the cavity concentration is greatly reduced only by pressures great enough to cause a solid phase (glass or crystal) to form.

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.

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