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Publication costs assisted by the National Science FoundationThe reaction of 2,2'-bipyridine (bpy), 1,lO-phenanthroline (phen), and their monoprotonated cations (bpyH+ and phenH+) with radiation-generated one-electron reducing agents yields radicals, the spectra, kinetics, and acid-base properties of which have been established. BpyH2+. has a pK, of 5.6 and exhibits an intense absorption maximum at 375 nm ( e 4.5 X lo4 M-l cm-' 1; bpyH. shows A, , , 365 nm ( E 3.0 X lo4 M-' cm-'). BpyH. decays via second-order kinetics (2h = 4.0 X lo9 M-' sd) representing primarily a disproportionation reaction. BpyH2+. appears to decay via concurrent first-and second-order reactions; the processes are complicated by unidentified dose-dependent sequences. Irrespective of pH, the final isolatable product is a pale yellow solid which can be identified by elemental analysis, molecular weight determination, and IR spectrum as a trimer of dihydrobipyridine isomers. PhenHz+. shows A,, 370 nm (e 7.8 X lo3 M-' cm-l ) and 510 nm ( e 3.8 X lo3 M-l cm-' ) and pK, = 6.3 while phenH. exhibits A, , , 350 nm ( E 5.8 X lo3 M-' cm-' ) and 475 nm (t 3.0 X lo3 M-' cm-l ).PhenH. protonates to form phenHz+-with k = 8.3 X lo9 M-' s-' a nd phenHz+. decays via second-order kinetics (2k = 1.6 x lo9 M-l s-l ). In alkaline solution (pH 10-13) the decay of phenH. is first order ( k = 2 X IO3 9-l).The bimolecular reaction appears to proceed predominantly via combination; a product has been isolated with the empirical formula C12HllN2C104. The behavior of the one-electron reduction products is compared with that of species believed to be similar arising from the photoreduction of bpy and phen in aqueous solution.

The relative increase in the free ion yield with increasing field strength E, expressed as GE/G:, is smaller when the following quantities are larger: (I ) dielectric constant, (2) temperature, and (3) separation distance between the geminate ion-electron pairs. The field dependence (dGc/dE)/G: equals 9.7/&T2 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 OK), 2-methylpropane (isobutane, 148-294 OK), 2,2-dimethylpropane (neopentane, 295 OK), argon (87 OK), oxygen (87 OK) and argon-oxygen solutions (87 OK) 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) = ymi, y-% with x < 4 provides a good interpretation of the results when GE < 0.2; a Gaussian distribution function provides the best interpretation of the field effects when GE > 0.2. Either they 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 A) is much smaller than had been expected and is only 2.6 times greater than that in liquid methane (b = 500 A at 120 OK). Phonon emission by 10-0.01 eV electrons in liquid argon may be relatively efficient and might involve transient states of the type Ar*,.L'accroissement relatif du rendement en ion libre avec le champ E, exprime par GE/GP,, est plus faible lorsque les grandeurs suivantes croissent: (I) la constante dielectrique, (2) la temperature, (3) la distance stparant les paires ion-electron geminees. La variation du champ (dGi/dE)/G:, est tgale a 9.7/&T2 cm/V pour E faible mais aux champs plus eleves elle est affectee par les trois facteurs cites ci-dessous et par E lui-mCme. Les rtsultats obtenus a partir des liquides propane (123-233 OK) methyl-2 propane (isobutane, 148-294 OK) dimethyl-2,2 propane (neopentane, 295 OK), argon (87 OK), oxygtne (87 OK), et argon-oxygine en melange (87 OK), sont prtsentes et analyses selon un modele theorique. Differents types de fonctions de distribution pour la separation ion-electron sont essayes. Dans le cadre du modele une fonction puissance F ( > y ) = ymi, y-% avec x < 4 fournit une bonne interprttation des resultats pour GFi < 0.2; une fonction de distribution gaussienne donne la meilleure interpretation des effets du champ pour GE10.2. La distribution y a soit une allure de type gaussien au centre finissant par une legtre inclinaison soit une allure reellement gaussienne pour les liquides dans lesquels la distance parcouru par les electrons est plus grande. Le parcours de I'electron dans l'argon pur (b = 1300 A) est beaucoup plus petit que celui attendu; il est seulement 2.6 fois plus grand que dans le methane liquide (b = 500 A a 120 OK). L'emission de phonons par les electrons de 10-0.01 eV dans I'argon liquide peut Etre relativement efficace et pourrait impliquer des etats...

The free-ion yields in liquid alkanes increase with increasing molecular sphericity and increasing temperature, in agreement with earlier observations. The Arrhenius temperature coefficient of free-ion formation is 0.8 kcal/mole in propane and 0.7 kcal/mole in 2-methylpropane. The free-ion yield in purified argon at 87°K appears to be Gfi=2.0. Addition of oxygen to liquid argon decreased the free-ion yield, mainly because the efficiencies of electron energy loss processes with the diatomic oxygen molecules were much greater than those with monatomic argon molecules; the oxygen served to decrease the ion—electron separation distance more by de-energizing the electron than by scavenging it before it reached the end of its normal track. In pure liquid oxygen at 87°K, Gfi=0.013. The ion—electron neutralization rate constant equals 8 × 10−5 cm3/ion · sec in pure argon at 87°K and 3.1 × 10−4 cm3/ion · sec in liquid methane at 120°K. The mobility of electrons in liquid methane is 300 cm2/V · sec and decreases in other hydrocarbons with decreasing sphericity of the molecules. The Arrhenius temperature coefficient of electron mobility in 2-methylpropane is 3 kcal/mole. Ion—ion neutralization rate constants in the present liquids were all of the order of 10−9 cm3/ion·sec, and the ion mobilities were all in the vicinity of 10−3 cm2/V · sec.

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