Radiation oxygen pressure

Table I shows how the quantum yields of the chief products may vary with the oxygen pressure at 36, 70, and I00°C.100 and at 150 and 200°C.81 using 3130 A. radiation. [These are calculated with reference to the carbon monoxide yield in the absence of oxygen at 131 °C. or above, which is assumed to correspond to unit quantum yield (Herr and Noyes81).] Photooxidation appears to occur by a chain reaction at 200°C. since large quantum yields of products are obtained in the first few minutes (Fig. 2), but the burst of reaction dies away later (Fig. 3). Using lower pressures and temperatures, e.g., 30 mm. at 150°C., no chain reaction is obtained and the products are produced at a constant rate (Fig. 4). Then the total quantity of carbon-containing products...

Calvert and Hanst88 using infrared analysis, have also re-investigated the photooxidation of acetaldehyde at 20°C. using 3130 A. radiation. Acetaldehyde pressures were chiefly about 42.5 nun., but the oxygen pressure was varied from 0 to 745 mm. Analyses were made for carbon monoxide, carbon dioxide, formic acid, methanol, acetic acid, peracetic acid, acetyl peroxide, methyl hydroperoxide, and unreacted acetaldehyde (Table X). Chains were short. Although they do not detect methyl hydroperoxide or diacetyl peroxide, the non-observance of a peroxide does not necessarily mean it is not formed. The decomposition of hydroperoxides on the smallest particle of catalyst is remarkably fast. 

The photooxidation has been studied by Blacet,17 who found at room temperature using 3130 A. radiation and oxygen pressures of 10 to 100 mm. that the products were carbon monoxide, carbon dioxide, water, acetaldehyde, ethanol, and propionic acid. The quantum yields of water, acetaldehyde, and ethanol were 9,3, and 3, respectively. 

Fig. 6. Evidence from ESR for the growth of oxygen anion radicals at gas/solid interfaces exposed to various radiations, (a) (i) Kinetic curves for chemisorption of oxygen (1) and the formation of ion radicals 02 (2) on A1203 under the action of 7-irradiation. T = 25°C, dose rate = 0.5 X 1017 eV g-i min (ii) ESR spectrum of 02 adsorbed on 7-Al203. Reproduced with permission and minor adaptation from ref. 81. (b) Changes in intensity of ESR signal of 02 at g 2.0, /2 0, and in oxygen pressure on illumination of an 02/Zr02 sample. Reproduced with permission and minor adaptation from ref. 82. (c)(i) ESR spectrum of O and (ii) its growth at an N20/ZnO interface on exposure to UV illumination. Reproduced with permission from ref. 85.

The initial rate of oxygen chemisorption was directly proportional to the quantity of A1203 catalyst and radiation intensity but was independent of oxygen pressure. Chemisorption stopped when 7-irradiation ceased. Radiation-enhanced chemisorption of hydrogen obeyed the expression... 

A sub-orbital spaceflight (above 100 km) or a low Earth orbit (LEO) impose on the composites the following conditions absence of oxygen, temperature variable from -120°C (dark side) to +300°C (solar side), UV and heavy ions radiation, low pressure 10 Pa. For... 

Chemical stability of uranium oxides. Both the early Manhattan Project work [9] and the ORNL work [10] indicated that uranium trioxide would be the probable stable form of uranium oxide under the radiolytic gas formed by the radiation-induced decomposition of water in a reactor. Uranium dioxide in an aqueous slurry at 250°C was oxidized to uranium trioxide in the presence of oxygen overpressure and even in the presence of excess hydrogen gas. The extent of this oxidation depended on the oxygen pressure, and seemed to be independent of the partial pressure of hydrogen (Table 4-1). The extent of oxidation of U3O8 to uranium trioxide depended on both temperature and oxygen pressure. The presence... 

Solution polymerization of VDE in fluorinated and fluorochlorinated hydrocarbons such as CEC-113 and initiated with organic peroxides (99), especially bis(perfluoropropionyl) peroxide (100), has been claimed. Radiation-induced polymerization of VDE has also been investigated (101,102). Alkylboron compounds activated by oxygen initiate VDE polymerization in water or organic solvents (103,104). Microwave-stimulated, low pressure plasma polymerization of VDE gives polymer film that is <10 pm thick (105). Highly regular PVDE polymer with minimized defect stmcture was synthesized and claimed (106). Perdeuterated PVDE has also been prepared and described (107). 

Since chlorinated PVC is totally transparent in the near-UV and visible range, it will not absorb at 488 nm, the emission line of the argon ion laser that we intended to use to perform the carbonization. Therefore C-PVC films were first exposed to the UV radiation of a medium pressure mercury lamp in order to produce the strongly absorbing polyenes. This irradiation was carried out at room temperature in the absence of oxygen, thus preventing the formation of undesirable oxidation products. 

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