cw CO2 laser-induced and SF6-sensitized decomposition of methyl iodide-d3

1983 ◽  
Vol 48 (11) ◽  
pp. 3261-3269 ◽  
Author(s):  
Jaroslav Rejnek ◽  
Marie Jakoubková ◽  
Pavel Engst ◽  
Milan Horák
Keyword(s):  
Decomposition Rate ◽  
Total Pressure ◽  
Laser Excitation ◽  
Irradiation Time ◽  
Product Distribution ◽  
Recombination Reaction ◽  
Reaction Step ◽  
Abstraction Reaction ◽  
Excitation Line ◽  
Cw Co2 Laser

The decomposition of CD3I initiated by the irradiation of a cw CO2 laser was studied in the presence of the SF6 sensitizer. The first reaction step of the decomposition produces CD3 radical that yields either methane-d4 (the abstraction reaction of „hot" radicals), or ethane-d6 (the recombination reaction of „cold" radicals). The effect of the total pressure and the composition of the reaction mixture, that of the laser excitation line and output and that of the irradiation time upon the decomposition rate and the product distribution was examined.

Novel Products in the CO2-Laser Induced Reaction of Trichloroethylene

1995 ◽  
Vol 60 (1) ◽  
pp. 104-114 ◽  
Author(s):  
Boyd L. Earl ◽  
Richard L. Titus
Keyword(s):  
Irradiation Time ◽  
Product Distribution ◽  
Incident Power ◽  
Cell Geometry ◽  
Reaction Conditions ◽  
Peak Areas ◽  
Induced Decomposition ◽  
Nmr Methods ◽  
Induced Reaction ◽  
Novel Products

Previous reports on the thermal or CO2-laser induced decomposition of trichloroethylene have identified only one condensible product, hexachlorobenzene (in addition to HCl and mono- and dichloroacetylene). We have found that trichloroethylene vapor exposed to cw irradiation on the P(24) line of the (001 - 100) band of the CO2 laser at incident power levels from 8 - 17 W produces numerous products, of which the 13 major ones have been identified using IR, GC/MS, GC/FTIR, and NMR methods. All of these products have 4, 6, or 8 carbons, are highly unsaturated, and are completely chlorinated or contain a single hydrogen. C4HCl5 and C6Cl6 isomers (three of each) account for S 55% to 85% of total products (based on peak areas in the total ion chromatograms in GC/MS runs), depending on reaction conditions. In addition to characterizing the products, we discuss the dependence of the product distribution on laser power, irradiation time, and cell geometry, and we outline a possible mechanism.

Cw CO2 laser driven oxidation of some perhalogenocycloalkenes

1991 ◽  
Vol 56 (2) ◽  
pp. 398-405 ◽  
Author(s):  
Josef Pola ◽  
Jaroslav Včelák ◽  
Zdeněk Chvátal
Keyword(s):  
Co2 Laser ◽  
Total Pressure ◽  
Diels Alder ◽  
Title Reaction ◽  
Consecutive Reactions ◽  
Cw Co2 Laser

The title reaction of hexafluorocyclobutene, 1,2-dichloro-3,3,4,4-tetrafluorocyclobutene and decafluorocyclohexene studied at total pressure 13.3 and 16 kPa yield oxalyl halides COX.COX (X = F, Cl) and C2F4 that undergo consecutive reactions to COF2, CO and X2. The oxidation of decafluorocyclohexene is preceded by retro-Diels-Alder decomposition affording hexafluorocyclobutene and C2F4. Two alternative mechanisms for the oxidation of the cyclobutenes are presented, one involving a novel cleavage of intermediary bicyclic dioxetanes. The decomposition of oxalyl fluoride into COF2 and CO is favored over its oxidation.

Intense Photoluminescence and Photoluminescence Enhancement of Silicon Nanocrystals by Ultraviolet Irradiation

2007 ◽  
Vol 31 ◽  
pp. 74-76 ◽  
Author(s):  
P.T. Huy ◽  
P.H. Duong
Keyword(s):  
Silicon Nanocrystals ◽  
Room Temperature ◽  
Laser Excitation ◽  
Uv Light ◽  
Irradiation Time ◽  
Excitation Wavelength ◽  
Nonradiative Recombination ◽  
Emission Yield ◽  
Recombination Centers ◽  
Pl Intensity

Photoluminescence (PL) from silicon nanocrystals deposited on top of silica-glass template and from silicon nanocrystals in nc_Si/SiO2 multilayer films were studied as a function of ultraviolet (UV) laser irradiation time in vacuum. Both the films exhibit intense visible PL at room temperature under laser excitation. It was found that upon prolong irradiation time using a He-Cd laser (325 nm) the PL intensity of the films was spectacularly enhanced. The process is reversible and does not happen with excitation wavelength longer than 400 nm. Upon introducing air into the measurement chamber, a rapid decrease of the PL intensity was recorded. This observation suggests that the UV light may lead to modification of nonradiative recombination centers in the films and thus improves the emission yield of silicon nanocrystals.

scholarly journals A mass spectrometric study of secondary organic aerosols formed from the photooxidation of anthropogenic and biogenic precursors in a reaction chamber

2006 ◽  
Vol 6 (12) ◽  
pp. 5279-5293 ◽  
Author(s):  
M. R. Alfarra ◽  
D. Paulsen ◽  
M. Gysel ◽  
A. A. Garforth ◽  
J. Dommen ◽  
...  
Keyword(s):  
Irradiation Time ◽  
Organic Aerosols ◽  
Mass Spectrometric Study ◽  
Product Distribution ◽  
Reaction Chamber ◽  
Oxidation Products ◽  
Effective Density ◽  
Mass Spectral ◽  
Fragmentation Patterns ◽  
The Right

Abstract. An Aerodyne Aerosol Mass Spectrometer (AMS) has been utilised to provide on-line measurements of the mass spectral signatures and mass size distributions of the oxidation products resulting from irradiating 1,3,5-trimethylbenzene (1,3,5-TMB) and α-pinene, separately, in the presence of nitrogen oxide, nitrogen dioxide and propene in a reaction chamber. Mass spectral results indicate that both precursors produce SOA with broadly similar chemical functionality of a highly oxidised nature. However, significant differences occur in the minor mass spectral fragments for the SOA in the two reaction systems, indicating that they have different molecular composition. Nitrogen-containing organic compounds have been observed in the photooxidation products of both precursors, and their formation appeared to be controlled by the temporal variability of NOx. Although the overall fragmentation patterns of the photooxidation products in both systems did not change substantially over the duration of each experiment, the contribution of some individual mass fragments to total mass appeared to be influenced by the irradiation time. The effective densities of the 1,3,5-TMB and α-pinene SOA particles were determined for various particle sizes using the relationship between mobility and vacuum aerodynamic diameters. The effective density for the 1,3,5-TMB SOA ranged from 1.35–1.40 g/cm3, while that for α-pinene SOA ranged from 1.29–1.32 g/cm3. The determined effective densities did not show dependence on irradiation time. Results suggest that further chemical processing of SOA takes place in the real atmosphere, as neither the α-pinene nor the 1,3,5-TMB experimental results reproduce the right relative product distribution between carbonyl-containing and multifunctional carboxylic acid species measured at ambient locations influenced by aged continental organic aerosols.

Resonant Photoluminescence Excitation in GaAs Grown Directly on Si

1988 ◽  
Vol 116 ◽  
Author(s):  
S. Zemon ◽  
C. Jagannath ◽  
S. K. Shastry ◽  
W. J. Miniscalco ◽  
G. Lambert
Keyword(s):  
Ground State ◽  
Heavy Hole ◽  
Laser Excitation ◽  
Free Exciton ◽  
Light Hole ◽  
The Other ◽  
Organometallic Vapor Phase Epitaxy ◽  
Photoluminescence Excitation ◽  
Excitation Spectra ◽  
Excitation Line

AbstractWe describe new results observed during resonant excitation in the excitonic region of GaAs grown directly on Si by organometallic vapor phase epitaxy. Two resolved features were found in the light hole photoluminescence (PL) region, one identified with a free exciton process and the other with donor-related transitions. Features which track the laser excitation line were observed and identified with a process in which a donor is excited from the n=l ground state to an n=2 excited state. The PL excitation spectra associated with these features have spectral widths as narrow as 1.5 meV. PL spectral widths of ~3 meV have been attained for the heavy hole exciton band, representing the narrowest value obtained for OMVPE material and an improvement of about 30% over our best previous results.

scholarly journals Glow Discharge for High Power cw CO2 Laser Excitation

1985 ◽  
Vol 13 (7) ◽  
pp. 570-577 ◽  
Author(s):  
Masaaki TANAKA ◽  
Yukio SATO ◽  
Masao HISHII ◽  
Haruhiko NAGAI ◽  
Norikazu TABATA
Keyword(s):  
Glow Discharge ◽  
Co2 Laser ◽  
High Power ◽  
Laser Excitation ◽  
Cw Co2 Laser

scholarly journals A mass spectrometric study of secondary organic aerosols formed from the photooxidation of anthropogenic and biogenic precursors in a reaction chamber

2006 ◽  
Vol 6 (4) ◽  
pp. 7747-7789 ◽  
Author(s):  
M. R. Alfarra ◽  
D. Paulsen ◽  
M. Gysel ◽  
A. A. Garforth ◽  
J. Dommen ◽  
...  
Keyword(s):  
Irradiation Time ◽  
Organic Aerosols ◽  
Mass Spectrometric Study ◽  
Product Distribution ◽  
Reaction Chamber ◽  
Oxidation Products ◽  
Effective Density ◽  
Mass Spectral ◽  
Fragmentation Patterns ◽  
The Right

Abstract. An Aerodyne Aerosol Mass Spectrometer (AMS) has been utilised to provide on-line measurements of the mass spectral signatures and mass size distributions of the oxidation products resulting from irradiating 1,3,5-trimethylbenzene (1,3,5-TMB) and α-pinene, separately, in the presence of nitrogen oxide, nitrogen dioxide and propene in a reaction chamber. Mass spectral results indicate that both precursors produce SOA with broadly similar chemical functionality of a highly oxidised nature. However, significant differences occur in the minor mass spectral fragments for the SOA in the two reaction systems, indicating that they have different molecular composition. Nitrogen-containing organic compounds have been observed in the photooxidation products of both precursors, and their formation appeared to be controlled by the temporal variability of NOx. Although the overall fragmentation patterns of the photooxidation products in both systems did not change substantially over the duration of each experiment, the contribution of some individual mass fragments to total mass appeared to be influenced by the irradiation time. The effective densities of the 1,3,5-TMB and α-pinene SOA particles were determined for various particle sizes using the relationship between mobility and vacuum aerodynamic diameters. The effective density for the TMB-SOA ranged from 1.35–1.40 g/cm3, while that for α-pinene SOA ranged from 1.29–1.32 g/cm3. The determined effective densities did not show dependence on irradiation time. Results suggest that further chemical processing of SOA takes place in the real atmosphere, as neither the α-pinene nor the 1,3,5-TMB experimental results reproduce the right relative product distribution between carbonyl-containing and multifunctional carboxylic acid species measured at ambient locations influenced by aged continental organic aerosols.

Note: Deep ultraviolet Raman spectrograph with the laser excitation line down to 177.3 nm and its application

2014 ◽  
Vol 85 (4) ◽  
pp. 046105 ◽  
Author(s):  
Shaoqing Jin ◽  
Fengtao Fan ◽  
Meiling Guo ◽  
Ying Zhang ◽  
Zhaochi Feng ◽  
...  
Keyword(s):  
Laser Excitation ◽  
Excitation Line ◽  
Deep Ultraviolet
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