Some of the thermal electrons formed when a liquid
is subjected to high-energy radiations eventually become
solvated. These solvated electrons (e⁻solv) are of
special chemical interest due to their powerful reducing
nature. The mechanism by which solvation occurs is not
well understood, but must depend upon several solvent
properties, of which the static dielectric constant is
probably the most important. Some insight into the
factors determining electron solvation may be gained
through a knowledge of the radiation yields of e⁻solv in
a wide variety of liquids. Since water is the liquid of
highest dielectric constant (є=80) studied to date it
seemed worthwhile to extend our knowledge beyond this
point. Of the four common liquids with dielectric
constants greater than that of water, formamide (є=109)
was best suited for this study.
In the present work the e⁻solv yield in formamide
was found to be only slightly greater than its yield in water, which is surprising considering the large increase in dielectric constant. A modified correlation which, in addition to the dielectric constant, included the solvating ability and the stopping power of the solvent was shown to give a better fit to data for a number of liquids (resolving, for instance, the ammonia anomaly), indicating that these factors also govern the yield of e⁻solv. The yields of hydrogen, carbon monoxide, and nitrogen formed when formamide and its nitrous oxide solutions were irradiated with ⁶⁰Co Ƴ-rays gave information
concerning the e⁻solv yield. Using the electron
scavenger N₂O and the scavenger pairs N₂O/Cd⁺⁺, N₂O/Ag⁺,
and N₂O/acid, the number of e⁻solv formed per 100 eV of
energy absorbed was found to be 2.9±0.1. This yield corresponds fairly closely with the value which can be calculated using Freeman's non-homogeneous model. The primary yields of H₂ HCONH*₂, CO, and HCO were evaluated as .75±0.05, 0.4±0.1, ≤ 0.55±0.07, and ≥ 1.15±0.20
molecules/l00eV respectively. At low doses (up to ∼5xl0¹⁹
eV/ml) the yields of H₂, N₂, and CO were dose independent
for the dose rate of ∼4xl0¹⁷ eV/ml-minute used.
In two types of pulse radiolysis experiments light absorption was not observed in the 4500 Å to 8500 Å wavelength region contrary to expectations. A comparison of these results with those from other work may be interpreted as suggesting that the half-life of formation
of e⁻solv, in formamide is between 0.36 and 1.9
microseconds. This tentative conclusion, if correct, would mean that e⁻solv was a secondary, not a primary, product in formamide and this would be of general significance to the primary processes of radiation chemistry. / Science, Faculty of / Chemistry, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/34676 |
| Date | January 1969 |
| Creators | Head, David Alan |
| Publisher | University of British Columbia |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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