PRIMARY PROCESS STUDIES BY MONOISOTOPIC PHOTOSENSITIZATION ON THE REACTIONS OF Hg 6(3P1) ATOMS WITH ALKYL CHLORIDES

1964 ◽  
Vol 42 (9) ◽  
pp. 2056-2064 ◽  
Author(s):  
J. K. S. Wan ◽  
O. P. Strausz ◽  
W. F. Allen ◽  
H. E. Gunning
Keyword(s):  
Mercury Vapor ◽  
Quantum Yields ◽  
Primary Process ◽  
Reaction Parameters ◽  
Specific Nature ◽  
Electrodeless Discharge ◽  
Discharge Source ◽  
Bond Scission ◽  
Decomposition Formula ◽  
Process Studies

The specific nature of the primary process in the reaction of 202Hg 6(3P1) atoms, photoexcited in natural mercury vapor by a cool 202Hg electrodeless discharge source, with CH3Cl has been examined in detail. Primary C–Cl bond scission occurs with unit efficiency. Quantum yields (φ) for the two primary modes of decomposition[Formula: see text]were found to have values of 0.71 (b) and 0.29 (a). The effect of various reaction parameters on the 202Hg enrichment in the calomel product has been investigated and the importance of isotopic mercury depletion in the reaction zone demonstrated by the use of intermittent illumination.A brief study of the reaction of ethyl, n-propyl, i-propyl, t-butyl, and n-amyl chlorides has revealed a relation between the molecular structure of the alleyl chloride and the efficiency of the monoisotopic route (a) to calomel formation. Thus, while the reactions of all the normal alkyl chlorides have φa values between 0.29 and 0.32, φa (isopropyl chloride) is only 0.22 and φa (t-butyl chloride) is 0.17.

THE Hg 6(3P1) PHOTOSENSITIZATION OF CHLORODIFLUOROMETHANE

1965 ◽  
Vol 43 (5) ◽  
pp. 1022-1029 ◽  
Author(s):  
M. G. Bellas ◽  
O. P. Strausz ◽  
H. E. Gunning
Keyword(s):  
Incident Light ◽  
Strong Dependence ◽  
Quantum Yields ◽  
Primary Process ◽  
Reaction Products ◽  
Light Intensities ◽  
Principal Reaction ◽  
Bond Scission ◽  
Circulatory Apparatus ◽  
Cl Atoms

The reaction was studied in a circulatory apparatus under a variety of conditions. The sole primary process occurring is C—Cl bond scission. The Cl atoms formed in the primary step, through an abstractive attack on the substrate, generate chlorodifluoromethyl radicals (CF2Cl) All principal reaction products, CF2H2, CF2Cl2, CF2ClCF2Cl, CF2HCF2H, and CF2HCF2Cl, can be accounted for by the combination–disproportionation reactions of the CF2H• and CF2Cl• radicals. The observed strong dependence of the primary quantum yields on the incident light intensities has been ascribed to a rapid substrate-reforming step.

Reactions of Thiyl Radicals. VII. Photolysis of Methyl Sulfide Vapor

1972 ◽  
Vol 50 (6) ◽  
pp. 844-852 ◽  
Author(s):  
P. M. Rao ◽  
A. R. Knight
Keyword(s):  
Wavelength Range ◽  
Sulfur Hexafluoride ◽  
Quantum Yields ◽  
Primary Process ◽  
Methyl Radicals ◽  
Methyl Sulfide ◽  
Thiyl Radicals ◽  
Several Variables ◽  
Bond Scission ◽  
Function Of Several Variables

The photolysis of methyl sulfide vapor has been investigated as a function of substrate pressure, exposure time, and temperature in the wavelength range 2000 to 2300 Å. The effects of added propane, sulfur hexafluoride, and 2-methylpentane have been studied. The principal products of the decomposition are CH4, C2H6, CH3SSCH3, and CH3SH. The data indicate direct C—S bond scission in the primary process giving rise to "hot" CH3 and CH3S radicals. A mechanism in which disproportionation of methylthiyl radicals is a very minor process is proposed.The reactions of CH3 and CH3S radicals with methyl sulfide have been examined also by photolyzing CH3SSCH3 and CH3COCH3 in the presence of CH3SCH3. Quantum yields at 2288 Å have been determined as a function of several variables. A number of rate parameters for the reactions of methyl radicals and methylthiyl radicals have been calculated.

The Mechanism of the HgH A22Π3/2 → X2Σ+ Emission in the Hg(63P0) Photosensitization of Hydrogen and the Alkanes

1973 ◽  
Vol 51 (8) ◽  
pp. 1207-1214 ◽  
Author(s):  
A. C. Vikis ◽  
D. J. Le Roy
Keyword(s):  
Ground State ◽  
Quantum Yields ◽  
Primary Process ◽  
Relative Quantum

The mechanism of the HgH A22Π3/2 → X2Σ+ emission detected in the Hg(63P0) photosensitized decomposition of H2 and some of the lower alkanes, RH, was investigated. It was concluded that ground state HgH was formed in the primary process Hg(63P0) + RH(or H2) → HgH(X2Σ+) + R(or H). The HgH A22Π3/2 → X2Σ+ emission and presumably the A12Π1/2 → X2Σ+ and B2Σ+ → X2Σ+ emission, also observed in the above systems, result from secondary excitation of ground state HgH on collision with Hg(63P0). Studies of the emission made possible the estimation of relative quantum yields for the above primary process.

Spectrum of Br V

1971 ◽  
Vol 49 (3) ◽  
pp. 391-393 ◽  
Author(s):  
Charan J. Budhiraja ◽  
Y. N. Joshi
Keyword(s):  
Ionization Potential ◽  
Electrodeless Discharge ◽  
Discharge Source

The spectrum of Br V has been revised and extended using an electrodeless discharge source. Twelve new lines have been assigned to the spectrum. A tentative value of the ionization potential has been found to be 502 860 cm−1 (62.33 eV).

Transformation of Phenylphenol Isomers by UVC Irradiation in Aqueous Solution

2015 ◽  
Vol 18 (2) ◽  
Author(s):  
Magdalena Olak-Kucharczyk ◽  
Marcin Bizukojć ◽  
Stanisław Ledakowicz
Keyword(s):  
Aqueous Solution ◽  
Degradation Rate ◽  
Degradation Products ◽  
Quantum Yields ◽  
Uv Disinfection ◽  
Reaction Parameters ◽  
Oxygen Scavengers ◽  
Photolytic Degradation ◽  
Reaction Solution ◽  
Disinfection Process

AbstractThe objective of this work was to study the photochemical behavior of ortho-phenylphenol (o-PP), metaphenylphenol (m-PP) and para-phenylphenol (p-PP) aqueous solutions exposed to 254 nm radiation. The influence of various reaction parameters on degradation rate was examined. Moreover, degradation products and toxicity of the reaction solutions were studied. It was observed that photolysis of phenylphenols was dependent on oxygen concentration in the reaction solution. The presence of radical and singlet oxygen scavengers in the reaction solution did not affect the photolytic degradation of the studied compounds. The values of apparent quantum yields of o-PP, m-PP and p-PP photolysis at pH 7 were equal to 0.019±0.00043, 0.023±0.00038 and 0.014±0.00083, respectively. The main intermediates of phenylphenols phototransformation were isomers of dihydroxybiphenyl. The degradation of phenylphenols during photolysis by 254 nm radiation ran quite fast. However, for the total mineralization of these compounds in water several times higher UV doses than those usually applied during UV disinfection process were required.

PRIMARY QUANTUM YIELD DETERMINATION BY INTERMITTENT ILLUMINATION IN THE REACTION OF METHANOL VAPOR WITH Hg 6(3P1) ATOMS

1961 ◽  
Vol 39 (11) ◽  
pp. 2251-2255 ◽  
Author(s):  
Arthur R. Knight ◽  
Harry E. Gunning
Keyword(s):  
Quantum Yield ◽  
Primary Process ◽  
Static System ◽  
Dark Light ◽  
Methanol Vapor ◽  
Maximum Value ◽  
Yield Determination ◽  
Intermittent Illumination ◽  
Process Studies ◽  
Kinetic Effects

The decomposition of methanol vapor by Hg 6(3P1) atoms has been studied under intermittent illumination conditions, in a static system at 25 °C. The behavior of the NO-inhibited reaction under intermittent illumination has also been examined.For the pure substrate at a pressure of 50 mm, the quantum yield of hydrogen formation, Φ(H2), was found to rise steadily toward unity with decreasing light period (tL). The maximum value of Φ(H2) at a given tD could only be obtained if the dark period (tD) exceeded 100 mseconds. At the shortest tL studied, 0.156 msecond, Φ(H2) was 0.89 compared with the steady illumination value, at zero extent of reaction, of 0.46. A linear relation was found to obtain between Φ(H2) and log (tL) at a given tD Extrapolation showed that Φ(H2) would be unity at tL = 0.040 msecond.For a mixture of 4.8 mm of NO and 50 m of CH3OH, Φ(CH3ONO) was found to rise from its steady illumination value of 0.14 to 0.27 at a sector speed of 300 r.p.m., with a dark/light ratio of 20. At higher speeds the quantum yield decreased again.From the study it is concluded that the primary process of H atom detachment is at least 89% efficient, and that the primary quantum yield is likely unity. The fact that the quantum yield under steady illumination is only 0.46 is attributed to the consumption of H atoms by radical addition processes of which the most probable is the addition of H to CH2OH. For the inhibited reaction the low value of Φ(CH3ONO) under steady illumination is ascribed to the abstractive attack of CH3O on NOH.The kinetic effects of intermittent illumination are discussed, in the light of the results. It is concluded that the technique should be of considerable value in primary process studies in mercury photosensitization.

ERRATUM: PRIMARY PROCESS STUDIES BY MONOISOTOPIC PHOTOSENSITIZATION ON THE REACTIONS OF Hg 6(3P1) ATOMS WITH ALKYL CHLORIDES

1965 ◽  
Vol 43 (1) ◽  
pp. 318-318 ◽  
Author(s):  
J. K. S. Wan ◽  
O. P. Strausz ◽  
W. F. Allen ◽  
H. E. Gunning
Keyword(s):  
Primary Process ◽  
Process Studies

not available

Reactions of thiyl radicals. XII. Triplet mercury photosensitized decomposition of ethyl sulfide in the gas phase

1976 ◽  
Vol 54 (8) ◽  
pp. 1290-1295 ◽  
Author(s):  
Conrad S. Smith ◽  
Arthur R. Knight
Keyword(s):  
Quantum Yield ◽  
Gas Phase ◽  
Quantum Yields ◽  
Second Step ◽  
Primary Process ◽  
Reaction Products ◽  
Process Comparison ◽  
Thiyl Radicals ◽  
Ethyl Radicals ◽  
High Sulfide

The triplet mercury photosensitized decomposition of ethyl sulfide vapour has been studied at 25 °C. The reaction products include C2H4 (Φ0 = 0.075), C2H6 (Φ0 = 0.043), C4H10 (Φ0 = 0.011), C2H5SH (Φ0 = 0.068), 4-methyl-3-thiahexane (Φ0 = 0.011), and C2H5SSC2H5 (Φ0 = 0.175). The overall decomposition quantum yield is 0.38 at high sulfide pressures. The initial decomposition gives principally ethyl radicals and ethylthiyl radicals; a second step which yields ethylene and ethanethiol may account for up to 20% of the primary process. Comparison of the direct and sensitized decompositions indicates that both likely originate in the triplet manifold of ethyl sulfide.Primary decomposition quantum yields have been accurately redetermined for the direct, 254 nm, photolysis of methyl sulfide (0.51), methylethyl sulfide (0.46), and ethyl sulfide (0.49).

Reactions of Thiyl Radicals. X. Photolysis of Ethyl Sulfide Vapor

1973 ◽  
Vol 51 (5) ◽  
pp. 780-786 ◽  
Author(s):  
Conrad S. Smith ◽  
Arthur R. Knight
Keyword(s):  
Reaction Rates ◽  
Quantum Yields ◽  
Minor Role ◽  
Primary Decomposition ◽  
Primary Process ◽  
Temperature Reaction ◽  
Reaction Products ◽  
Thiyl Radicals ◽  
Pressure Time ◽  
A Minor

The photolysis of ethyl sulfide vapor at 2537 Å has been investigated as a function of substrate and CF4 pressure, time, and temperature. Reaction products with quantum yields in parentheses are ethyl disulfide (0.178), ethane (0.138), butane (0.086), ethanethiol (0.096), 4-methyl-3-thiahexane (0.034) and 4-methyl-3,5-dithiaheptane.Ethyl and ethylthiyl radicals are formed in the primary process and the product yields indicate a net primary decomposition quantum yield of 0.48. A reaction mechanism involving subsequent reactions of the primary fragments is proposed and explains the observed products and the observed variation in rates. Excited radicals and hot radical combination products play a minor role in this system, in contrast to the behavior of lower molecular weight sulfides. Secondary photolysis of the disulfide produced and consumption of ethanethiol are important factors in determining the time dependence of reaction rates in this system.

A Hot Wire Loop Atomizer for Atomic Fluorescence Spectrometry

1970 ◽  
Vol 24 (5) ◽  
pp. 518-521 ◽  
Author(s):  
M. P. Bratzel ◽  
R. M. Dagnall ◽  
J. D. Winefordner
Keyword(s):  
Quantum Yields ◽  
Atomic Fluorescence Spectrometry ◽  
Argon Flow Rate ◽  
Electrodeless Discharge ◽  
Atomic Fluorescence ◽  
Argon Flow ◽  
Discharge Tubes ◽  
Argon Stream ◽  
Anion Type ◽  
Platinum Loop

Samples containing Ag, Be, Bi, Cd, Cu, Ga, Hg, Mg, Pb, Tl, and Zn are vaporized from a tungsten or platinum loop into an argon stream and excited by radiation from electrodeless discharge tubes to produce atomic fluorescence. The integrated atomic fluorescence signals are independent of loop material and loop temperature, and nearly independent of anion type, sample nature, and argon flow rate. The device may have use for fundamental studies for measurement of quantum yields as well as for applied studies of measuring nanogram to picogram quantities of volatile metals in small amounts of sample (about 2 µl needed for analysis). The loop and sheathing device are described.

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