Thermal electron attachment to oxygen and van der Waals molecules containing oxygen

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

DOI:https://doi.org/10.1063/1.440853· OSTI ID:7011870

Shimamori, H; Fessenden, R W

Thermal electron attachment to O/sub 2/ has been studied for pure O/sub 2/ (/sup 16/O/sub 2/ and /sup 18/O/sub 2/), O/sub 2/--N/sub 2/, O/sub 2/--CO, and O/sub 2/--n-C/sub 4/H/sub 10/ (/sup 16/O/sub 2/ and /sup 18/O/sub 2/) systems at temperatures from approx.330 down to 78/sup 0/ K using pulse radiolysis and microwave conductivity. For pure O/sub 2/, O/sub 2/--N/sub 2/, and O/sub 2/--CO mixtures, the electron attachment rates showed three-body pressure dependences at all temperatures over the pressure range studied (P/sub O2/<10Torr, P/sub N2/<60 Torr, P/sub CO/<40 Torr). The three-body rate constant of /sup 16/O/sub 2/ decreases from approx.2.4 x 10/sup -30/ cm/sup 6/ molecule/sup -2/ sec/sup -1/ at 330 /sup 0/K to about 0.9 x 10/sup -30/ cm/sup 6/ molecule/sup -2/ sec/sup -1/ at approx. 140 /sup 0/K but unexpectedly increases again to about 1.7 x 10/sup -30/ cm/sup 6/ molecule/sup -2/ sec/sup -1/ at 79 /sup 0/K. Similarly, the three-body rate constant of /sup 18/O/sub 2/ decreases from 5.1 x 10/sup -30/ cm/sup 6/ molecule/sup -2/ sec/sup -1/ at 300 /sup 0/K to 1.8 x 10/sup -30/ cm/sup 6/ molecule/sup -2/ sec/sup -1/ at approx.110 /sup 0/K but increases to 2.3 x 10/sup -30/ cm/sup 6/ molecule/sup -2/ sec/sup -1/ at 80 /sup 0/K. The three-body rate constant of N/sub 2/ shows a more dramatic monotonic increase from 0.9 x 10/sup -31/ cm/sup 6/ molecule/sup -2/ sec/sup -1/ at 300 /sup 0/K to 9.4 x 10/sup -31/ cm/sup 6/ molecule/sup -2/ sec/sup -1/ at 78 /sup 0/K. In the case of CO, the three-body rate constant appears to have a very shallow minimum around 170 /sup 0/K and again increases with further decrease of temperature. Since theory predicts a simple decrease in rate constant with reduced temperature, an extra contribution to the rate constant which increases with lowered temperature is evident. Electron attachment to the van der Waals molecules (O/sub 2/)/sub 2/, (O/sub 2/xN/sub 2/), and (O/sub 2/xCO) is proposed to account for this behavior. It has been found that the dependence of the excess rate on temperature follows rather closely the predicted concentration of van der Waals molecules.

• Research Organization: Radiation Laboratory and Department of Chemistry, University of Notre Dame, Notre Dame, Indiana 46556
• OSTI ID: 7011870
• Journal Information: J. Chem. Phys.; (United States), Vol. 74:1
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
ALKANES
RADIOLYSIS
CARBON MONOXIDE
NITROGEN
OXYGEN
ELECTRON ATTACHMENT
BINARY MIXTURES
CHEMICAL REACTION KINETICS
LOW TEMPERATURE
MEDIUM TEMPERATURE
PRESSURE DEPENDENCE
VAN DER WAALS FORCES
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
DECOMPOSITION
DISPERSIONS
ELEMENTS
HYDROCARBONS
KINETICS
MIXTURES
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RADIATION CHEMISTRY
RADIATION EFFECTS
REACTION KINETICS
400600* - Radiation Chemistry