Monoatomic oxygen

From the above results, one can conclude the existence of the two types of adsorbed oxygen species which may be speculated as monoatomic and diatomic oxygen species. The monoatomic oxygen species can produce (In) and the diatomic oxygen species can produce C2Hi,0 and decompose (In). 

Monoammonium phosphate (MAP), 77 120-121 72 67 78 835 manufacture of, 78 854 Monoatomic oxygen, 70 642 Monoazo dyes, 9 245, 395 Monoazo Orange, colorant for plastics, 7 374t... 

This Set 8 consistently explained all other transient response curves, as typically presented in Figure 2 by a dotted curve. Comparing Sets 6 and 8 in Table 2, the value of k2 in the 02-C0 reaction is a hundred times larger than that in the N20-C0 reaction. This means that adsorbed oxygen is very quickly dissociated into monoatomic oxygen, in contrast to the N20-C0 reaction. This is consistent with Clarkson and Cirillo s estimation [ 1 1 ] in which they evaluated only 0.02% of all adsorbed oxygen to be diatomic oxygen on oxidized silver. 

In early proposals the species responsible for epoxidation was identified as the adsorbed molecular oxygen, Ag 02(ads)> while combustion was attributed to monoatomic Ag O(ads) (Equations 14-16). The oxidation step envisages the transfer of one atom of molecularly adsorbed oxygen to the double bond, while the other remains adsorbed on silver. The consumption of the latter by the total oxidation of ethylene restores the site vacancies necessary for the continuation of catalysis. Up to a maximum of six oxygen atoms are required for the combustion of one ethylene molecule. Thus, the combination of the reactions (Equation 14) and (Equation 15) predicts that the maximum attainable selectivity in the epoxidation of ethylene is 6/7, i.e., 85.7% (Equation 16). A lower selectivity should normally be expected because some monoatomic oxygen independently formed by dissociative adsorption (Equation 13) raises the level of ethylene combustion above that predicted by Equation 16. 

Materials that are directly exposed to the space environment must also withstand or be protected from atomic oxygen. Atomic oxygen is prevalent in the low earth orbit (LEO), approximately 100 to 350 miles from Earth. At this distance, molecular oxygen reacts with ultraviolet light to produce monoatomic oxygen which is extremely chemically reactive and erosive. Most adhesives used in spacecraft, however, are sandwiched between two adherends, thus not directly exposed. 

Principally, when exposed to an RF or MW energy field, oxygen is broken down into monoatomic oxygen (0), 0", and 0. Monoatomic oxygen is the most reactive element in this type of plasma and will readily combine with any organic hydrocarbon. The resultant combination in atmosphere is water vapor and CO2, which is carried away in the exhaust stream. However, inorganics such as salts and silicones are not so readily removed. 

---