Sulfur ylides generated from the reaction of arylchlorocarbenes with trimethylenesulfide: determination of rate parameters by laser flash photolysis

The photochemical dehalogenation of α-haloacetophenones (Cl, Br) in benzene solution has been examined under conditions of continuous and pulsed laser irradiation. Product and quantum yield studies indicate that carbon-halogen bond cleavage occurs with quantum yields of 0.88 and 0.41 for α-chloro- and α-bromoacetophenone, respectively. These values are based on trapping studies in which the PhC(O)ĊH2 radicals produced photochemically are scavenged by hydrogen donors such as benzenethiol. Laser flash photolysis studies lead to intense transient signals due to benzene–halogen complexes. Combination of transient data and quantum yields lead to extinction coefficients of 1 800 and 23 700 M−1 cm−1 for the chlorine (490 nm) and bromine (550 nm) complexes, respectively.

Download Full-text

Determination of association constants by laser flash photolysis between Zn-TPPS3 and bipyridinium salts in photocatalytic hydrogen evolution systems

Journal of Molecular Catalysis ◽

10.1016/0304-5102(85)85040-9 ◽

1985 ◽

Vol 32 (1) ◽

pp. 119-123 ◽

Cited By ~ 4

Author(s):

Ichiro Okura ◽

Naruhiko Kaji ◽

Shigetoshi Aono ◽

Akira Yamada

Keyword(s):

Hydrogen Evolution ◽

Flash Photolysis ◽

Laser Flash Photolysis ◽

Laser Flash ◽

Association Constants ◽

Photocatalytic Hydrogen Evolution ◽

Evolution Systems

Download Full-text

Measurement of OH reactivity by laser flash photolysis coupled with laser-induced fluorescence spectroscopy

10.5194/amt-2016-51 ◽

2016 ◽

Cited By ~ 4

Author(s):

Daniel Stone ◽

Lisa K. Whalley ◽

Trevor Ingham ◽

Peter M. Edwards ◽

Daniel R. Cryer ◽

...

Keyword(s):

Loss Rate ◽

Flash Photolysis ◽

Laser Flash Photolysis ◽

Laser Flash ◽

Laser Induced Fluorescence ◽

Ozone Production ◽

Oh Radicals ◽

Field Campaigns ◽

Lif Spectroscopy

Abstract. OH reactivity (k'OH) is the total pseudo-first-order loss rate coefficient describing the removal of OH radicals to all sinks in the atmosphere, and is the inverse of the chemical lifetime of OH. Measurements of ambient OH reactivity can be used to discover the extent to which measured OH sinks contribute to the total OH loss rate. Thus, OH reactivity measurements enable determination of the comprehensiveness of measurements used to predict air quality and ozone production, and, in conjunction with measurements of OH radical concentrations, to assess our understanding of OH production rates. In this work, we describe the design and characterisation of an instrument to measure OH reactivity using laser flash photolysis coupled to laser-induced fluorescence (LFP-LIF) spectroscopy. The LFP-LIF technique produces OH radicals in isolation, and thus minimises potential interferences in OH reactivity measurements owing to the reaction of HO2 with NO which can occur if HO2 is co-produced with OH in the instrument. Capabilities of the instrument for ambient OH reactivity measurements are illustrated by data collected during field campaigns in London, UK, and York, UK. We also present the coupling and characterisation of the LFP-LIF instrument to an atmospheric chamber for measurements of OH reactivity during simulated experiments, and provide suggestions for future improvements to OH reactivity LFP-LIF instruments.

Download Full-text