Pulse radiolysis of gaseous ammonia--oxygen mixtures. [Pulsed irradiation]

Journal Article · Thu Mar 08 04:00:00 EST 1979 · J. Phys. Chem.; (United States)

DOI:https://doi.org/10.1021/j100468a006· OSTI ID:6478467

Pagsberg, P B ^[1]; Eriksen, J; Christensen, H C

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1. Riso National Lab., Roskilde, Denmark

The effect of oxygen concentration on the decay rates of the radicals NH/sub 2/ and NH was studied using the well-known electronic absorption bands of the two species. We also observed the OH radical being formed with the yield going through a maximum with increasing oxygen concentrations. Due to the possible role of OH as a chain carrier in the system, we investigated the important reaction OH + NH/sub 3/ ..-->.. H/sub 2/O + NH/sub 2/ and found k(OH+NH/sub 3/) = (1.6+-0.2) x (1.6+-0.2) x 10/sup 8/M/sup -1/s/sup -1/ at 300 K and an activation energy of 0.87 +- 0.08 kcal/mol. H atoms are consumed by the reaction H + O/sub 2/ ..-->.. HO/sub 2/, and the transient yield of OH is explained consistently by the reaction H + HO/sub 2/ ..-->.. 2OH with k(H+HO/sub 2/) = 2 x 10/sup 10/M/sup -1/s/sup -1/ in a computer-simulated model. The decay of NH/sub 2/ was found to be independent of the oxygen partial pressure in the range 0-420 mbar at 349 K. A transient species absorbing at 2300 A is formed in NH/sub 3/-O/sub 2/ mixtures. The kinetic features show that the precursor is HO/sub 2/ reacting with NH/sup 3//sub 3/ to form either a hydrogen-bonded complex NH/sub 4/O/sub 2/, or, by water elimination, NHOH. A model for high-dose rate radiolysis of pure gaseous ammonia is proposed. The computer-simulated model, which incorporates N/sub 2/H/sub 3/ as an important intermediate species, is consistent with the observed kinetic features and with the experimental product yields. On the basis of this model we obtained the following rate constants: k(NH/sub 2/+NH/sub 2/) = k(H+NH/sub 2/) = 1.6 x 10/sup 10/M/sup -1/s/sup -1/, k(NH+NH/sub 2/) = 7 x 10/sup 10/m/sup -1/s/sup -1/, and k(N/sub 2/H/sub 3/+N/sub 2/H/sub 3/) = 10/sup 11/M/sup -1/s/sup -1/ at 349 K. 11 figures, 4 tables.

• OSTI ID: 6478467
• Journal Information: J. Phys. Chem.; (United States), Journal Name: J. Phys. Chem.; (United States) Vol. 83:5; ISSN JPCHA
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
ABSORPTION SPECTRA
ACTIVATION ENERGY
AMMONIA
AMMONIUM COMPOUNDS
CHALCOGENIDES
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISTRY
COMPUTER CALCULATIONS
CRYOGENIC FLUIDS
DATA
DATA FORMS
DECAY
DECOMPOSITION
ELEMENTS
ENERGY
EXPERIMENTAL DATA
FLUIDS
GASES
HYDRATES
HYDRIDES
HYDROGEN COMPOUNDS
HYDROXYL RADICALS
INFORMATION
IRRADIATION
ISOLATED VALUES
KINETICS
LOW PRESSURE
MEDIUM TEMPERATURE
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
NUMERICAL DATA
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PRESSURE DEPENDENCE
PULSED IRRADIATION
QUANTITY RATIO
RADIATION CHEMISTRY
RADIATION EFFECTS
RADICALS
RADIOLYSIS
REACTION INTERMEDIATES
REACTION KINETICS
SPECTRA
TEMPERATURE DEPENDENCE
THEORETICAL DATA