Photochemical reactions of triplet benzophenone and anthraquinone molecules with amines in the gas phase

2004 ◽  
Vol 96 (4) ◽  
pp. 503-511 ◽  
Author(s):  
G. A. Zalesskaya ◽  
E. G. Sambor ◽  
N. N. Belyĭ
Keyword(s):  
Gas Phase ◽  
Photochemical Reactions

Simultaneous photochemical generation of ozone in the gas phase and photolysis of aqueous reaction systems using one VUV light source

1997 ◽  
Vol 35 (4) ◽  
pp. 41-48 ◽  
Author(s):  
T.M. Hashem ◽  
M. Zirlewagen ◽  
A. M. Braun
Keyword(s):  
Gas Phase ◽  
Light Source ◽  
Organic Pollutants ◽  
Vacuum Ultraviolet ◽  
Oxidative Degradation ◽  
Reaction System ◽  
Photochemical Reactions ◽  
Experimental Conditions ◽  
Photochemical Generation ◽  
Kinetics Of

A more efficient use of vacuum ultraviolet (VUV) radiation produced by an immersed Xe-excimer light source (172 nm) was investigated for the oxidative degradation of organic pollutants in aqueous systems. All emitted VUV radiation from one light source was used in two simultaneous but separate photochemical reactions: (1) photochemical generation of ozone by irradiating oxygen in the gas phase and (2) photolysis of the aqueous reaction system. The gas stream containing the generated ozone is sparged into the reaction system, thus enhancing the oxidative degradation of organic pollutants. The photochemically generated ozone in the gas phase was quantitatively analyzed, and the kinetics of the degradation of 4-chlorophenol (4-CP) and of the dissolved organic carbon (DOC) were determined under different experimental conditions. The results show that the rates of degradation of the substrate and of the DOC decrease in the order of the applied processes, VUV/O3 > O3 > VUV.

scholarly journals Evaluated kinetic and photochemical data for atmospheric chemistry: Volume II – reactions of organic species

2005 ◽  
Vol 5 (4) ◽  
pp. 6295-7168 ◽  
Author(s):  
R. Atkinson ◽  
D. L. Baulch ◽  
R. A. Cox ◽  
J. N. Crowley ◽  
R. F. Hampson ◽  
...  
Keyword(s):  
Kinetic Parameters ◽  
Gas Phase ◽  
Atmospheric Chemistry ◽  
Kinetic Data ◽  
Photochemical Reactions ◽  
Data Evaluation ◽  
Organic Species ◽  
Summary Sheet

Abstract. This article, the second in the series, presents kinetic and photochemical data evaluated by the IUPAC Subcommittee on Gas Kinetic Data Evaluation for Atmospheric Chemistry. It covers the gas phase and photochemical reactions of Organic species, which were last published in 1999, and were updated on the IUPAC website in late 2002. The article consists of a summary sheet, containing the recommended kinetic parameters for the evaluated reactions, and eight appendices containing the data sheets, which provide information upon which the recommendations are made.

Modelling the photochemical formation of high H2O2 concentrations and secondary sulfate observed during winter haze periods in the NCP

2020 ◽  
Author(s):  
Andreas Tilgner ◽  
Erik Hans Hoffmann ◽  
Lin He ◽  
Bernd Heinold ◽  
Can Ye ◽  
...  
Keyword(s):  
Air Pollution ◽  
Gas Phase ◽  
Aqueous Phase ◽  
Photochemical Reactions ◽  
Data Availability ◽  
Phase Reaction ◽  
Aerosol Composition ◽  
Chemistry Research ◽  
The Impact

<p>During winter, the North China Plain (NCP) is frequently characterized by severe haze conditions connected with extremely high PM2.5 and NOx concentrations, i.e. strong air pollution. The NCP is one of the most populated regions worldwide where haze periods have direct health effects. Tropospheric haze particles are a complex multiphase and multi-component environment, in which multiphase chemical processes are able to alter the chemical aerosol composition and deduced physical aerosol properties and can strongly contribute to air pollution. Despite many past investigations, the chemical haze processing is still uncertain and represents a challenge to atmospheric chemistry research. Recent NCP studies during autumn/winter 2017 haze periods have revealed unexpected high H<sub>2</sub>O<sub>2</sub> concentrations of about 1 ppb suggesting H<sub>2</sub>O<sub>2</sub> as a potential contributor to secondary PM2.5 mass, e.g., due to sulfur(IV) oxidation. However, the multiphase H<sub>2</sub>O<sub>2</sub> formation under such NOx concentrations is still unclear. Therefore, the present study aimed at the examination of potential multiphase H<sub>2</sub>O<sub>2</sub> formation pathways, and the feedback on sulfur oxidation.</p><p>Multiphase chemistry simulations of a measurement campaign in the NCP are performed with the box model SPACCIM. The multiphase chemistry model within SPACCIM contains the gas-phase mechanism MCMv3.2 and the aqueous-phase mechanism CAPRAM4.0 together with both its aromatics module CAPRAM-AM1.0 and its halogen module CAPRAM-HM2.1. Furthermore, based on available literature data, the multiphase chemistry mechanism is extended considering further multiphase formation pathways of HONO and an advanced HOx mechanism scheme enabling higher in-situ H<sub>2</sub>O<sub>2</sub> formations in haze particles. The simulations have been performed for three periods characterized by high H<sub>2</sub>O<sub>2</sub> concentrations, high RH and PM2.5 conditions and high measurement data availability. Several sensitivity runs have been performed examining the impact of the soluble transition metal ion (TMI) content on the predicted H<sub>2</sub>O<sub>2</sub> formation.</p><p>Simulations with the improved multiphase chemistry mechanism shows a good agreement of the modelled H<sub>2</sub>O<sub>2</sub> concentrations with field data. The modelled H<sub>2</sub>O<sub>2</sub> concentration shows a substantial dependency on the soluble TMI content. Higher soluble TMI contents result in higher H<sub>2</sub>O<sub>2</sub> concentrations demonstrating the strong influence of TMI chemistry in haze particles on H<sub>2</sub>O<sub>2</sub> formation. The analysis of the chemical production and sink fluxes reveals that a huge fraction of the multiphase HO<sub>2</sub> radicals and nearly all of the subsequently formed reaction product H<sub>2</sub>O<sub>2</sub> is produced in-situ within the haze particles and does not origin from the gas phase. Further chemical analyses show that, during the morning hours, the aqueous-phase reaction of H<sub>2</sub>O<sub>2</sub> with S(IV) contributes considerably to S(VI) formation beside the HONO related formation of sulfuric acid by OH in the gas-phase.</p><p>Finally, a parameterization was developed to study the particle-phase H<sub>2</sub>O<sub>2</sub> formations as potential source with the global model ECHAM-HAMMOZ. The performed global modelling identifies an increase of gas-phase H<sub>2</sub>O<sub>2</sub> by a factor of 2.8 through the newly identified particle chemistry. Overall, the study demonstrated that photochemical reactions of HULIS and TMIs in particles are an important H<sub>2</sub>O<sub>2</sub> source leading to increased particle sulfate formation.</p>

Wavelength-Dependent Area Selectivity in Photochemical Vapor Deposition of Aluminum Films

1989 ◽  
Vol 158 ◽  
Author(s):  
Mitsugu Hanabusa ◽  
Masashi Ikeda
Keyword(s):  
Gas Phase ◽  
Vapor Deposition ◽  
Emission Spectra ◽  
Nucleation Mechanism ◽  
Photochemical Reactions ◽  
Aluminum Films ◽  
Thickness Profile ◽  
Uv Photons ◽  
Photochemical Vapor Deposition ◽  
Deuterium Lamp

ABSTRACTThickness profile of aluminum thin films deposited from dimethylaluminum hydride on silicon substrate changed with wavelengths of light chosen from the wide emission spectra of a deuterium lamp. Under illumination of the VUV around 160 nm deposits were formed preferentially in illuminated regions, while such area selectivity was lost and uniformly thick films were deposited all over the substrate when the UV around 240 nm was used. The observed area selectivity can be interpreted as arising from a wavelength-dependent nucleation mechanism; namely, surface photochemical reactions leading to nucleation are induced only by the VUV, while the UV photons are capable of producing photofragments in gas phase responsible for nucleation.

A beamline for photochemical processes at atmospheric pressure

1998 ◽  
Vol 5 (3) ◽  
pp. 548-550 ◽  
Author(s):  
Jun-ichi Takahashi ◽  
Yuichi Utsumi ◽  
Teruo Hosokawa ◽  
Jun Ushiki ◽  
Toshiaki Tadano
Keyword(s):  
Gas Phase ◽  
Atmospheric Pressure ◽  
Water Concentration ◽  
Reaction Chamber ◽  
Supply System ◽  
Photochemical Reactions ◽  
Effective Control ◽  
Chamber Studies ◽  
Differential Pumping ◽  
Gas Supply

A beamline especially designed for atmospheric photochemical reactions has been constructed at the NTT synchrotron radiation facility. By inserting a buffer helium chamber with Be and Si3N4 partition windows between the beamline and the reaction chamber, studies can be performed without the differential pumping systems normally used in existing photochemistry beamlines. The reaction chamber is equipped with a gas supply system and analysis systems to investigate gas-phase and surface reactions. Purging using dry purified gases in combination with water-bubbling gives effective control of water concentration in the reaction chamber.

scholarly journals Photodegradation of Riboflavin under Alkaline Conditions: What can Gas-Phase Photolysis Tell Us About What Happens in Solution?

2021 ◽  
Author(s):  
Natalie G.K. Wong ◽  
Chris Rhodes ◽  
Caroline E.H. Dessent
Keyword(s):  
Mass Spectrometry ◽  
Gas Phase ◽  
Direct Method ◽  
Photochemical Reactions ◽  
Solution Phase ◽  
Ionization Mass ◽  
Phase Reaction ◽  
Esi Ms ◽  
Alkaline Conditions ◽  
On Line

The application of electrospray ionization mass spectrometry (ESI-MS) as a direct method for detecting reactive intermediates is a technique of developing importance in the routine monitoring of solution-phase reaction pathways. Here, we utilize a novel on-line photolysis ESI-MS approach to detect the photoproducts of riboflavin in aqueous solution under mildly alkaline conditions. Riboflavin is a constituent of many food products, so its breakdown processes are of wide interest. Our on-line photolysis setup allows for solution-phase photolysis to occur within a syringe using UVA LEDs, immediately prior to being introduced into the mass spectrometer via ESI. Gas-phase photofragmentation studies via laser-interfaced mass spectrometry of deprotonated riboflavin, [RFH], the dominant solution-phase species under the conditions of our study, are presented alongside the solution-phase photolysis. The results obtained illustrate the extent to which gas-phase photolysis methods can inform our understanding of the corresponding solution-phase photochemistry. We determine that the solution-phase photofragmentation observed for [RFH] closely mirrors the gas-phase photochemistry, with the m/z 241 ion being the only major condensed-phase photoproduct. Further gas-phase photoproducts are observed at m/z 255, 212, and 145. The value of exploring both the gas- and solution-phase photochemistry to characterize photochemical reactions is discussed.

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