Quantum yield of photolysis

The fact that these estimated quantum yields are between 350 and 390 nm not too different from the quantum yields of photolysis of the corresponding solution... 

Ohnishi T, Nakato Y, Tsubumura H (1975) Quantum yield of photolysis of water on titanium oxide. Ber Bunsenges Phys Chem 79 523-525... 

The high quantum yield of photolysis of C02 suggests the rapid destruction of C02 and the formation of CO and 02 by sunlight of wavelengths below about 2200 A (see Section VI- 5). According to an estimate by McElroy and McConnell (675), the column abundance of C02 in the atmosphere is 2 x 1023 molec cm"2. With a dissociation rate of 2.5 x 1012 cm-2 sec-, the entire C02 may be destroyed in less than 10,000 years. 

Ultraviolet light without hydrogen peroxide is not very effective for the degradation of organics. When UV light and H202 are combined, the overall oxidative reaction potential is greatly enhanced even under ambient temperature and pressure. The efficiency of direct photolysis depends on (1) UV absorbance by substrates (2) quantum yield of photolysis (3) presence of other competitive UV absorbents and (4) intensity of UV sources. 

One can see from Table 7.1 that the quantum yield of photolysis of alkyl-substituted anthraquinones only slightly depended on the replacement of the methyl group by the ethyl or isopropyl group.26 However, it decreased drastically after the introduction of electron-donor substituents in 3- or 4-positions of the anthraquinone ring.17 Quantum yields of phototransformations of l-arylcyanomethyl-9,10-anthra-quinones were found to be substantially lower (by two orders of magnitude) than for 1-methylanthraquinone.36... 

Dulin D, Drossman H, Mill T(1986), Environ. Sci. Technol. 20 72-77.. .Products and quantum yields of photolysis of chloroaromatics in water"... 

The Quantum Yield of Photolysis of Water on Ti02 Electrodes Very low quantum yields ( 10 3) were measured when no external bias was applied. The effect of photon flux also explored. 224... 

Quantum Yields of Photolysis. These photochemical studies on high-molecular-weight polysilanes suggest that these polymers constitute a new class of photosensitive materials. The bleaching studies indicate that significant molecular weight reduction occurs upon irradiation in air or in vacuo, which in turn implies that the polymers are predominantly of the scissioning type. 

PRIMARY QUANTUM YIELDS OF PHOTOLYSIS OF THE rt-CsHTCOR-TVPE KETONES AT... 

Quantum yields of photolysis of higher alkyl azides vary between 0.7 and 0.9, depending on the medium and the size of the alkyl group It has been reported that the same factors influence the subsequent reactions of the intermediate nitrene, viz. 

The photolysis of aryl azides in low-temperature matrices yields triplet (ground) state nitrenes which have been identified by and absorption spectroscopy. Dinitrenes and trinitrenes have also been reported in the solid-state photolysis of di- and triazides. Quantum yields of photolysis of some aromatic azides are listed in Table 21 and it appears that nitrenes are produced in solution, at room temperature, as well. The lifetimes of some aromatic nitrenes and the absolute rates of some of their reactions have been measured . Some interesting features of photolytic azide decompositions will now be briefly described. 

QUANTUM YIELDS OF PHOTOLYSIS OF AROMATIC DIAZIDES AT 77 "K IN A METHYLCYCLOHEXANE-ISOPENTANE MATRIX... 

The quantum yields of photolysis of various nitroso compounds are very nearly unity in the long-wavelength absorption region (Table 37). In the photolysis of CF3NO process step (a) predominates and the major product is the dimer, (CF3)2N0N0, probably formed via nitroxide radicals the photochemistry of... 

Table 3. Quantum yield of photolysis of aromatic azides...

The rate of electron transfer approaches diffusion control when AG is more negative than -10 Kcal/mole. AG was calculated for all sensitizers used in this study with bothI AsF and AsF. An examination of Tables 1 and 2 shows that sensi-tizer systems with AG < -10 exhibit relatively large quantum yields of photolysis and high relative polymerization rates (RPR). 

Kinetic investigations showed that the photochemical ring-opening reaction depends on the nature of the C-5 substituents, i.e., the quantum yield is the highest for short alkyl substituents and decreases for long alkyl, unsaturated, and aromatic ones. Moreover, the quantum yield of photolysis is higher for the monoanion forms than for the undissociated molecules.385,386... 

TABLE 2 Quantum Yields of Photolysis of Ph2I + and Ph3S+ Hexafluoroarsenates [69)... 

The quantum yield of photolysis of carbon tetrabromlde could be determined by gas chromatographic measurements and the coloration efficiency could be determined by spectrophotometrical monitoring of the formation of the pyrylium salt at 630 nm. By comparison of both values It appears that approximately 50% of the decomposed carbon tetrabromlde produces hydrogen bromide, which is responsible for the formation of dye molecules. A typical Imaging system based on these materials gives a sensitivity of... 

The quantum yields of photolysis of a series of tertiary alkyl azides (2a-d) were measured and found to be in the range of 0.27-0.53. ... 

The direct photolysis of diaUcylphenacylsulfonium and dialkyl-4-hydroxyphenyl-sulfonium salts shown in Scheme 10 results in the reversible formation of ylides and Bronsted acids. Because of this reversibility, the efficiency of initiation of cationic polymerization is reduced over what would be predicted based on the magnitude of their quantum yields of photolysis (relative nucleophilicities of these two species. Further, the ylides themselves can terminate the growing cationic chain by the addition process shown in Eqs. (87) and (88). 

---