Electron ranges in liquid alkenes, dienes, and alkynes: Range distribution function in hydrocarbons

KYOII SHINSAKA, JEAN-POL DODELET, and GORDON R. FREEMAN. Can. J. Chem. 53,2714 (1975.Penetration ranges bGP of secondary electrons into 21 X-irradiated liquids were estimated from measured free ion yields. The density normalized ranges bcpd are independent of temperature. Increasing the molecular symmetry by creating one or more cycles in the molecule causes the normalized range to increase, provided that the amount of bond distortion due to strain remains small. Ranges are smaller in compounds that contain strained rings. Energy transfer from the secondary electrons to the molecules is enhanced by the presence of distorted bonds in the molecules. The ranges in olefins are affected by the same factors as those in saturated hydrocarbons, with the addition of a contribution of transient negative ion states to the energy transfer processes. Shielding the double bond by methyl groups is not effective; the effect of the added methyl groups on the molecular symmetry is a more important factor. The magnitude of the energy transfer interaction is an inverse function of molecular symmetry.The general correlation between bGp and thermal electron mobilities u. in liquids contains significant variations within it. For a given value of bGp, u, in different liquids increases in the order n-alkane < cycloalkane < cycloalkene < 1,4-cyclohexadiene or benzene. Arrhenius plots of u, in cyclic olefins curve downwards at low temperatures, due to the formation of a deeper trapped state of the electron. The trap is deepest in 1,4-cyclohexadiene (21 kcal/mol) and is attributed to an equilibrium between solvated electrons and anions at temperatures below about280K.KYOJI SHINSAKA, JEAN-POL DODELET et GORDON R. FREEMAN. Can. J. Chem. 53,2714Chem. 53, (1975. Les parcours des electrons secondaires, bGp, ont etk estimes d'aprts les rendements en ions libres mesurks dans 21 liquides irradits aux rayons X. NormalisCs pour la densite, ces parcours, bcpd, deviennent independants de la temperature. Une augmentation de la symktrie molCculaire par cyclisation simple ou multiple entraine une augmentation du parcours normalise, tant que la distorsion des liaisons demeure faible. Un important transfert d'energie des electrons secondaires est realise dans le cas de molCcules a cycle tendu, ce qui reduit le parcours des electrons dans de tels liquides. Les parcours electroniques dans les olefines sont fonction des mCmes facteurs que dans les alcanes, avec en plus la possibilite d'un transfert d'energie via la tendance a former un ion negatif CphCmere. L'addition de groupes mtthyles ne protege pas une double liaison, mais affecte la symetrie moleculaire. L'importance de la quantite d'energie transferee par collision est une fonction inverse de la symktrie moltculaire. La correlation gknerale entre bGP et la mobilitC de I'electron thermique dans les liquides presente une structure fine. Pour une valeur de bGp donnte, u. augmente selon I'ordre suivant: n-alcane < cycloalcane < cycloalctne < cyclohexaditne-1,4 ou benzene. La courbe obtenue en portant u, s...

“…The equipment and methods of measurement were described earlier (7,8). Briefly, a 1 ps (or 0.1 ps) pulse of 1.7 MeV X-rays delivered 3 x 10" eV/g (or 5 x lo9 eV/g) to the sample.…”

Section: Apparatus and Techniquesmentioning

confidence: 99%

“…Both saturated and unsaturated compounds were used. The molecular structure dependence of electron behavior in liquid olefins (7,8) is peculiar and is not even qualitatively understood. The search for a key to the understanding continues.…”

Section: Introductionmentioning

confidence: 99%

Electron Mobilities and Ranges in Liquid Hydrocarbons: Cyclic and Polycyclic, Saturated and Unsaturated Compounds

Shinsaka¹,

Dodelet²,

Freeman³

1975

“…5 ) , which means that electron energy-loss collisions are more effective in the latter. The lower efficiency in cis-correlates with the greater sphericity of the molecules (4,25).…”

Section: Results and Discussion Free Ion Yields And Electron Thermalimentioning

confidence: 99%

“…Previous measurements showed remarkable differences in the radiolytic free ion yields (3,4) and in the mobilities of thermal electrons (3,5) in these liquids. It appears that electrons are captured to form transient anions in the trans-isomer.…”

Section: Introductionmentioning

confidence: 99%

Molecular shape effects on electron and ion behavior in dielectric liquids: cis- and trans-butene-2 between the freezing and critical points

Sasakaki¹,

Freeman²

1994

Radiolysis free ion yields, electron mobilities, and ion mobilities were measured as functions of applied electric field strength in the liquids cis-and trans-butene-2 at temperatures from near their freezing points to near their critical points. The dielectric permittivities were also measured, to permit extraction of electron thermalization distances from free ion yield data. The thermalization distance distribution in each liquid was found to be the Gaussian YGP, rather than the exponential YE or YEP. This indicates that electrons are not captured before thermalization in either liquid. The density-normalized therrnalization distances bGpd were -40% larger in cis-than in trans-butene-2; this correlates with the more globular structure of the cis-molecules, which decreases the efficiency of electron energy loss collisions in the liquid phase. Electron mobilities were not appreciably different from those reported earlier. Cation mobilities in the liquids from the freezing points (TIT, % 0.35, d/dc % 3.2) up to -400 K (TIT, % 0.92, d/dc % 2.0) are adequately described by the free-volume model.At densities d/dc < 2.0 the mobilities are smaller than predicted by the free-volume model. SHINICHI SASAKAKI et GORDON R. FREEMAN. Can. J. Chem. 72, 1625 (1994. OpCrant 5 des tempkratures allant de leurs point de congClation 5 leurs point critiques, on a mesuri les rendements en ions libres, les mobilitCs des Clectrons et les mobilitts des ions produits, en fonction de la force du champ Clectrique appliquC, lors de la radiolyse des cis-et trans-but-2-knes liquides. On a aussi mesurC les permittivitCs afin de pouvoir diterminer les distances de thermalisation des Clectrons a partir des donnCes des rendements en ions libres. On a trouvC que la distribution des distances de thermalisation dans chaque liquide prCsente une forme gaussienne YGP plutat qu'une exponentielle YE ou YEP. Ce resultat indique que, dans chacun des liquides, les Clectrons ne sont pas capturCs avant la thermalisation. Les distances de thermalisation normalisCes pour la densite, bGpd, sont environ 40% plus grandes dans le cis-que dans le transbut-2-kne; ce rCsultat est en bon accord avec la structure plus globulaire des molicules cis qui, en phase liquide, diminue IntroductionThe present work continues the study of distribution functions of secondary electron thermalization distances in Xirradiated liquids (1). The scattering of low energy electrons in a liquid is strongly dependent on the molecular structure (2). Comparison of electron behaviors in isomeric hydrocarbons is particularly useful, because physical properties such as molar volume and average polarizability are similar, so differences in electron scattering properties can be attributed to differences in molecular shape.Isomers of special interest are cis-and trans-butene-2. Previous measurements showed remarkable differences in the radiolytic free ion yields (3, 4) and in the mobilities of thermal electrons (3, 5) in these liquids. It appears that electrons are captured to form transient anion...

“…6 to compensate for the lower mobilities and lower ion yields. It was described earlier (8). The low temperature bath was a Styrofoam box with walls 3 cm thick and a net inner volume -(lo Cold nitrogen gas from a 50 !…”

Section: And Techniquesmentioning

confidence: 99%

Electron mobilities in fluids through the liquid and critical regions: isomeric butenes

Dodelet¹,

Freeman²

1977

JEAN-POL DODELET and GORDON R. FREEMAN. Can. J. Chem. 55,2893(1977. Electron mobilities are similar in all four isomeric butenes near the critical region, N 10 cm2/V s at -420 K, and again in the low temperature liquids, -cm2/V s at --150 K, but not at intermediate temperatures. The Arrhenius temperature coefficient of the mobility decreases with increasing temperature in cis-butene-2 and isobutene, and increases with temperature in butene-1 and trans-butene-2. This difference in behavior is reflected in the temperature dependence of the dispersion parameter o in the assumed Gaussian distribution of transition energies between localized and extended states. The extreme cases are trans-butene-2, for which do/dT = 0, and cis-butene-2, for which do/dT z (2kCp)'12. Mobilities in mixtures of cis-and trans-butene-2 do not display ideal solution behavior; the transition energies Eo go through a maximum. The mobility in liruid cis-butene-2 under its vapor pressure goes through a maximum value of 17 cm2/V s at 426 K, decreases to 14 cm2/V s at T, = 433 K, then increases with temperature in the constant density supercritical gas. Maxima are not observed in the other butenes. Electron migration in each of the supercritical gases is an activated process with an activation energy of ~0 . 3eV. The present results emphasize the large role played by phase structure in electron migration.JEAN-POL DODELET et GORDON R. FREEMAN. Can. J. Chem. 55,2893(1977. Les mobilitts Blectroniques des quatre isomeres du butene sont semblables pres de la region critique: -10 cm2/V s a -420 K, ainsi qu'en phase liquide a basse temperature: N cm2/.V s a -150 K. Toutefois, ces mobilitks different dans la region des temperatures intermediaires. Pour ces mobilitks, le coefficient de temperature d'Arrh6nius decroit en augmentant la temperature du cis-butene-2 et de l'isobutene tandis qu'il augmente en Blevant la temperature du buthe-1 et du trans-buthe-2. Cette difference de comportement se refl&te dans la variation de o avec la temperature. o est le parametre de dispersion dans la distribution, supposk gaussienne, des transitions entre les Btats localises et Btendus d'energie. Les cas extrsmes sont le trans-buttne-2 pour lequel do/dT = 0 et le cis-butene-2 pour lequel do/dT % (2kCP)'l2. Les mobilites dans les melanges de cis-et trans-buttne-2 ne presentent pas le comportement d'une solution idkale; les energies de transition E, passent par un maximum. La mobilite dans le cisbutene-2 liquide, sous sa propre tension de vapeur, passe par un maximum de 17 cmZ/V s a 426 K pour ensuite dkroitre a 14 cmZ/V s a T, = 433 K. Dans le gaz supercritique, a densite constante, cette mobilitB augmente avec la temperature. Aucun maximum n'est observe pour les autres butbnes. La migration Blectronique pour tous ces gaz au dessus de la temperature critique est un processus accompagnk d'une Bnergie d'activation de -0.3 eV. Ces rksultats mettent l'accent sur le rBle joue par la structure de la phase dans la migration Blectronique.