Doctoral Dissertations
Date of Award
12-1988
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Major
Physics
Major Professor
L. G. Christophorou
Abstract
The total electron attachment rate constant ka(〈&epsilon〉 ,T) for n-C4F10 and for n-C6F14 has been measured in a buffer gas of Ar using an electron swarm technique in the mean electron energy range, 〈&epsilon〉, 0.41 to 4.81 eV, over the temperature range, T, 300 to 750 K and over the total gas number density, Nt, 2.25 to 12.88 × 1019 molecules/cm3. The measured ka(〈&epsilon〉 ,T) and the total electron attachment cross section σa(ε, T) obtained from them are reported and discussed. The ka(〈&epsilon〉 ,T) for n—C4F10 first decrease slowly with T between 300 to 400 K then decrease precipitously between 400 and ≈ 500 K and subsequently increase for T ≥ 500 K. The ka{{e) ,T) for n—C6F14 initially increase slowly with T between 300 and 400 K, then decrease precipitously between 400 and ≈ 550 K and subsequently decrease for T > 550 K. For both molecules the overall variation of ka(〈&epsilon〉 ,T) with T depends on 〈ε〉 and was independent of Nt except for n-C4F10 which exhibits an increase with Nt for T ≤ 500 K. From the measured dependence of ka(〈&epsilon〉 ,T) for n-C4F10 on Nt and T the contribution of the nondissociative and dissociative electron attachment to ka(〈&epsilon〉 ,T) was determined as a function of 〈ε〉. From the analysis of these results the effect of temperature on nondissociative electron attachment was quantified.
The total electron attachment rate constant ka(〈&epsilon〉 ,T) for SO2F2 in N2 has been measured as a function of 〈&epsilon〉 (0.046 to 0.911 eV), temperature (300 to 700 K) and total gas number density (2.25 to 6.44 × 1019 molecules/cm3). From the measured ka(〈&epsilon〉 ,T) the σa(ε, T) were determined. At T = 300 K the σa(ε, T) exhibits a maximum at ≈ 0.22 eV which is due to dissociative electron attachment and an increase below ≈ 0.1 eV which is due to the formation of parent anions at near zero energies. At T = 400 K the σa(ε, T) posseses only one main peak at ~ 0.13 eV which shifts to lower ε with increasing T so that at 700 K the peak is located at ≈ 0.03 eV. The value σa(εmax, T) of σa(ε, T) at the peak increases by a factor of 32 as T increases from 300 to 700 K. The analysis of the present results and earlier similar work leads to the conclusion that the increase of the dissociative electron attachment with temperature is due to the increase of the internal energy (principally vibrational) of the molecule.
The ionization onset, If, for TMPD (N,N,N',N'-tetramethyl-p-phenylenediamene) molecules in ethane has been measured for the first time in the number density, N, range 0.09 to 8.01 × 1021 molecules/cm3 and over the temperature T range 293 to 413 K, using a multiphoton ionization conductivity technique. The If was found to depend on both N and T in the ranges studied. At a fixed T{=373K), If was found first to decrease with increasing N and then to level off at number densities of ≈ 5.96 × 1021 molecules/cm3. For N ≥ 6.84 × 1021 molecules/cm3 and T = 293 K the If was found to increase with increasing number density. At a constant number density (N = 3.55 × 1021 molecules/cm3) If decreased with increasing T between 323 and 413 K.
Recommended Citation
Datskos, Panagiotis George, "Effect of temperature and density on electron attachment and ionization processes. " PhD diss., University of Tennessee, 1988.
https://trace.tennessee.edu/utk_graddiss/11848