Photochemical Reactions of Leuco Dyes in Rigid Solvents. Quantum Efficiency of Photo-oxidation

1943 ◽  
Vol 65 (12) ◽  
pp. 2419-2423 ◽  
Author(s):  
Gilbert N. Lewis ◽  
Jacob Bigeleisen
Keyword(s):  
Quantum Efficiency ◽  
Photochemical Reactions ◽  
Photo Oxidation

Toluene and styrene photo-oxidation quantum efficiency: Comparison between doped and composite tungsten-containing anatase-based catalysts

2019 ◽  
Vol 245 ◽  
pp. 49-61 ◽  
Author(s):  
Uriel Caudillo-Flores ◽  
Mario J. Muñoz-Batista ◽  
Ana B. Hungría ◽  
Miguel López Haro ◽  
Marcos Fernández-García ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Photo Oxidation ◽  
Efficiency Comparison

Photochemical Reactions. V. [1] Photo-oxidation of 17 β-acetoxy-4-aza-androst-5-en-3-one

1975 ◽  
Vol 58 (8) ◽  
pp. 2549-2552 ◽  
Author(s):  
F. Abelló ◽  
José Boix ◽  
José Gómez ◽  
José Morell ◽  
Juan-Julio Bonet
Keyword(s):  
Photochemical Reactions ◽  
Photo Oxidation

scholarly journals The photochemistry of phosphine

1932 ◽  
Vol 138 (835) ◽  
pp. 374-395 ◽  
Keyword(s):  
Experimental Data ◽  
Absorption Spectrum ◽  
Photochemical Reactions ◽  
Metallic Elements ◽  
Chain Reaction ◽  
Photo Oxidation ◽  
Considerable Success ◽  
Photochemical Decomposition ◽  
The Subject ◽  
A Chain

Within recent years the spectroscopy and the photochemistry of the hydrides of the non-metallic elements has been the subject of much study and the results explained with considerable success on the basis of the newer theories of photochemical reactions. In spite of the fact that the photochemistry of ammonia has attracted some attention, yet the investigation of the equally simple molecule of phosphine seems to have been entirely neglected. It is with the object of filling this gap in photochemistry that the present experiments have been undertaken. The investigation naturally falls into three parts: ( a ) the absorption spectrum of phosphine, ( b ) the direct photochemical decomposition, ( c ) the photosensitised decomposition. Experimental data on the photo-oxidation are also of importance in view of the fact that the thermal oxidation of phosphine is a chain reaction.

scholarly journals Aqueous-Phase Production of Secondary Organic Aerosols from Oxidation of Dibenzothiophene (DBT)

Atmosphere ◽  
2020 ◽  
Vol 11 (2) ◽  
pp. 151 ◽  
Author(s):  
Yu Liu ◽  
Junchen Lu ◽  
Yanfang Chen ◽  
Yue Liu ◽  
Zhaolian Ye ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
Aqueous Phase ◽  
Reaction Pathway ◽  
Photochemical Reactions ◽  
Oxidation Products ◽  
Gas Phase Reactions ◽  
Photo Oxidation ◽  
Oxygenated Compounds ◽  
Direct Light ◽  
Triplet Excited States

Intermediate-volatility organic compounds (IVOCs) have been recognized as an important contributor to the secondary organic aerosol (SOA) formation via gas-phase reactions. However, it is unclear whether or not IVOCs-SOA can be produced in the aqueous phase. This work investigated aqueous oxidation of one model compound of IVOCs, dibenzothiophene (DBT). Results show that DBT can be degraded by both hydroxyl radical and the triplet excited states of organic light chromophores (3C*). Aqueous dark oxidation of DBT was also possible. SOA yields of 32% and 15% were found for hydroxyl radical (OH)-mediated photo-oxidation and dark oxidation, respectively. A continuous and significant increase of oxidation degree of SOA was observed during OH photo-oxidation, but not during the dark oxidation. Factor analyses revealed that there was a persistent production of highly oxygenated compounds from the less oxygenated species. OH-initiated photochemical reactions can also produce species with a relatively large light-absorbing ability, while such photo-enhancement due to direct light irradiation and 3C*-initiated oxidation could occur, but is much less important. In the future, studies on the second-order rate constants, molecular characterization of the oxidation products from this and other IVOCs precursors are needed to better understand the role of this reaction pathway in SOA budget, air quality and climate change.

scholarly journals Polar organic compounds in rural PM<sub>2.5</sub> aerosols from K-puszta, Hungary, during a 2003 summer field campaign: Sources and diel variations

2005 ◽  
Vol 5 (7) ◽  
pp. 1805-1814 ◽  
Author(s):  
A. C. Ion ◽  
R. Vermeylen ◽  
I. Kourtchev ◽  
J. Cafmeyer ◽  
X. Chi ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Malic Acid ◽  
Sampling Site ◽  
Photochemical Reactions ◽  
Oxidation Products ◽  
Forest Site ◽  
Supporting Evidence ◽  
Diel Pattern ◽  
Field Campaign ◽  
Photo Oxidation

Abstract. In the present study, we examined PM2.5 continental rural background aerosols, which were collected during a summer field campaign at K-puszta, Hungary (4 June-10 July 2003), a mixed coniferous/deciduous forest site characterized by intense solar radiation during summer. Emphasis was placed on polar oxygenated organic compounds that provide information on aerosol sources and source processes. The major components detected at significant atmospheric concentrations were: (a) photo-oxidation products of isoprene including the 2-methyltetrols (2-methylthreitol and 2-methylerythritol) and 2-methylglyceric acid, (b) levoglucosan, a marker for biomass burning, (c) malic acid, an intermediate in the oxidation of unsaturated fatty acids, and (d) the sugar alcohols, arabitol and mannitol, markers for fungal spores. Diel patterns with highest concentrations during day-time were observed for the 2-methyltetrols, which can be regarded as supporting evidence for their fast photochemical formation from locally emitted isoprene. In addition, a diel pattern with highest concentrations during day-time was observed for the fungal markers, suggesting that the release of fungal fragments that are associated with the PM2.5 aerosol is enhanced during that time. Furthermore, a diel pattern was also found for levoglucosan with the highest concentrations at night when wood burning may take place in the settlements around the sampling site. In contrast, malic acid did not show day/night differences but was found to follow quite closely the particulate and organic carbon mass. This is interpreted as an indication that malic acid is formed in photochemical reactions which have a much longer overall time-scale than that of isoprene photo-oxidation, and the sources of its precursors are manifold, including both anthropogenic and natural emissions. On the basis of the high concentrations found for the isoprene oxidation products during day-time, it can be concluded that rapid photo-oxidation of isoprene is an important atmospheric chemistry process that contributes to secondary organic aerosol (SOA) formation at K-puszta during summer.

scholarly journals Polar organic compounds in rural PM<sub>2.5</sub> aerosols from K-puszta, Hungary, during a 2003 summer field campaign: sources and diurnal variations

2005 ◽  
Vol 5 (2) ◽  
pp. 1863-1889 ◽  
Author(s):  
A. C. Ion ◽  
R. Vermeylen ◽  
I. Kourtchev ◽  
J. Cafmeyer ◽  
X. Chi ◽  
...  
Keyword(s):  
Organic Compounds ◽  
Malic Acid ◽  
Photochemical Reactions ◽  
Oxidation Products ◽  
Forest Site ◽  
Diurnal Pattern ◽  
Field Campaign ◽  
Photo Oxidation ◽  
Isoprene Oxidation ◽  
Isoprene Oxidation Products

Abstract. In the present study, we examined PM2.5 continental rural background aerosols, which were collected during a summer field campaign at K-puszta, Hungary (4 June–10 July 2003), a mixed coniferous/deciduous forest site characterized by intense solar radiation during summer. Emphasis was placed on polar oxygenated organic compounds that provide information on aerosol sources and source processes. Analysis was performed using gas chromatography/mass spectrometry (GC/MS) after suitable sample workup consisting of extraction with methanol and derivatisation into trimethylsilyl (TMS) derivatives. The major components detected at significant atmospheric concentrations were: (a) photo-oxidation products of isoprene including the 2-methyltetrols (2-methylthreitol and 2-methylerythritol) and 2-methylglyceric acid, (b) levoglucosan, a marker for biomass burning, (c) malic acid, an end-oxidation product of unsaturated fatty acids, and (d) the sugar alcohols, arabitol and mannitol, markers for fungal spores. Diurnal patterns with highest concentrations during day-time were observed for the isoprene oxidation products, i.e., the 2-methyltetrols and 2-methylglyceric acid, which can be regarded as supporting evidence for their fast photochemical formation from their locally emitted precursor. In addition, a diurnal pattern with highest concentrations during day-time was observed for the fungal markers, arabitol and mannitol, suggesting that the release of fungal fragments that are associated with the PM2.5 aerosol is enhanced during that time. Furthermore, a diurnal pattern was also found for levoglucosan with the highest concentrations at night when wood burning may take place in the settlements around the sampling site. In contrast, malic acid did not show day/night differences but was found to follow quite closely the particulate and organic carbon mass. This is interpreted as an indication that malic acid is formed in photochemical reactions which have a much longer overall time-scale than that of isoprene photo-oxidation, and the sources of its precursors are manifold, including both anthropogenic and natural emissions. On the basis of the high concentrations found for the isoprene oxidation products, i.e., the 2-methyltetrols (28.5 ng m-3) and 2-methylglyceric acid (7.6 ng m-3), it can be concluded that rapid photo-oxidation of isoprene is an important atmospheric chemistry process that contributes to secondary organic aerosol (SOA) formation at K-puszta during summer.

Thermal lens determination of fluorescence quantum efficiency of3F4level of Tm3+ions in solids

2005 ◽  
Vol 125 ◽  
pp. 193-196 ◽  
Author(s):  
S. L. Oliveira ◽  
S. M. Lima ◽  
T. Catunda ◽  
H. Vargas ◽  
L. A.O. Nunes ◽  
...  
Keyword(s):  
Quantum Efficiency ◽  
Thermal Lens
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