Thermodynamic model for excess-electron energy and drift transport in liquid alkanes

Journal Article · Thu Jan 01 04:00:00 EST 1981 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j150614a024· OSTI ID:6130535

Hamill, W H

Electrons in liquid alkanes exhibit striking regularities between the electron energy V/sub 0/ (in the quasi-free state e/sub f//sup -/, relative to vacuum), the drift mobility ..mu.. and its activation energy E/sub a/, the dependence of V/sub 0/ on composition in binary mixtures, and the frequently very large negative value of dV/sub 0//dT identical with ..beta... Experimentally, U/sub p/ + T/sub 0/ = V/sub 0/ + ..beta..T for e/sub f//sup -/. For several alkanes the average value of V/sub 0/ + ..beta..T is -0.74 +- 0.003 eV at 296 K. In terms of the hopping transport model the activation free energy is ..cap alpha..(V/sub 0/ - V/sub 0t/) where V/sub 0t/ is the energy of the trapped electron e/sub t//sup -/, also relative to vacuum, and 0 < ..cap alpha.. < 1. The observed regularities require that ..cap alpha.. approx. = 0.38 at 296 K for the alkanes. Identification of V/sub 0/ with the free energy difference for e/sub vac//sup -/ ..-->.. e/sub f//sup -/ leads to ..beta.. = ..delta..S/sub 0/ and similarly ..gamma.. = ..delta..S/sub 0t/ for V/sub 0t/. This is qualitatively consistent with entropy changes for thermal electron detachment from anions in alkanes to produce e/sub t//sup -/. The necessity of considering an entropy of activation ..delta..S/sub a/ affects the interpretation ..mu../sub 0/ approx. = 150 cm/sup 2/ V/sup -1/ s/sup -1/ in ..mu.. = ..mu../sub 0/ exp(-E/sub a//kT). In mixtures of very unlike alkanes, E/sub a/ may vanish in a range of composition of ..delta..S/sub a/ remain positive and linear in composition, as in methane-ethane. Over a wide range of temperature V/sub 0/ may minimize, as in neopentane, and dV/sub 0//dT = 0 leads to ..delta..S/sub a/ = 0 at a minimum coincident with ..mu../sub max/.

• Research Organization: Univ. of Notre Dame, IN
• OSTI ID: 6130535
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 85:14; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400301* -- Organic Chemistry-- Chemical &amp; Physicochemical Properties-- (-1987)
ACTIVATION ENERGY
ALKANES
DATA
ELECTRON ATTACHMENT
ELECTRON DRIFT
ELECTRONS
ELEMENTARY PARTICLES
ENERGY
EXPERIMENTAL DATA
FERMIONS
FLUIDS
HYDROCARBONS
INFORMATION
LEPTONS
LIQUIDS
NUMERICAL DATA
ORGANIC COMPOUNDS