Recombination Energies of Positive Ions

The eventual fate of any ion is its neutralization, either by a free electron or by a negative ion formed by electron attachment. In ethylene radiolysis at high dose rates, electron capture processes should be insignificant (29), and the recombination energy of the positive ion will become available on neutralization, a portion of which may be in the form of excitation (59). 

At atmospheric pressure and in the presence of an unchanging concentration of positive ions P, the bimolecular rate constants can be replaced by pseudo-unimolecular rate constants k[> = k D[P] and 1approximately temperature-independent because recombination is exothermic since the energy is... 

Tladiation chemists have been aware for about 15 years that the presence of dilute solutes in liquid hydrocarbons can change the course of radiation chemical reactions by other than the normally expected secondary radical reactions. For example, Manion and Burton (40) in early work on the radiolysis of benzene-cyclohexane solutions, drew attention to the possibility of energy transfer from solvent to solute. Furthermore, it is known that in hydrocarbon solvents certain solutes are capable of capturing electrons, thus interfering with the normal ion-recombination process (14, 20, 65, 72). Though ionic products can be observed readily in hydrocarbon glasses [e.g., (19, 21)] demonstration of effects which can be specifically ascribed to electron capture in the liquid state has been elusive until recently. Reaction of positive ions prior to neutralization can play an important role as demonstrated recently by studies on... 

RECOMBINATION ENERGIES OF DOUBLY-CHARGED POSITIVE IONS... 

Three important detectors make use of the ionization, called here the initial ionization, that follows the absorption of x-rays by a gas and the ejection ol photoelectrons from the molecules involved. These photoelectrons subsequently ionize other molecules. The relatively large energy of the x-ray quantum thus leads to the production of a number of ion pairs, each consisting of an electron and a relatively immobile positive ion. if these ion pairs do not recombine, the extent of this initial ionization is determined by (and measures) the energy of the x-ray quantum. 

Alternatively the necessary energy can be supplied by the impact of electrons accelerated through the appropriate potential difference (2) or more subtly by collision with another positive (often atomic) ion with a higher recombination energy (the reverse of its ionization) (3). 

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