Laser Power Density Dependence in Absorption Measurements

1980 ◽  
Vol 34 (3) ◽  
pp. 311-313
Author(s):  
Peter M. Castle
Keyword(s):  
Power Density ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Continuous Wave ◽  
Strong Dependence ◽  
Wave Mode ◽  
Input Power ◽  
Absorption Cross ◽  
Continuous Wave Mode ◽  
Absorption Measurements

The absorption cross section of CF2Cl2 has been measured as a function of presure and CO2 laser input power at 10.764 μm. The laser was operated in the continuous wave mode providing a continuous energy deposition in the sample. It is shown that the absorption cross section measured has a strong dependence on input power density in the range from 5 to 15 W/cm2 and pressure in the 3 to 50 Torr regime. It is demonstrated that most of these effects can be attributed to the temperature rise in the beam interaction volume.

scholarly journals Absolute Absorption Cross Section of the Ã←X ̃ Electronic Transition of the Ethyl Peroxy Radical and Rate Constant of its Cross Reaction with HO2

2021 ◽  
Author(s):  
Cuihong Zhang ◽  
Mirna Shamas ◽  
Mohamed Assali ◽  
Xiaofeng Tang ◽  
Weijun Zhang ◽  
...  
Keyword(s):  
Cross Section ◽  
Rate Constant ◽  
Absorption Cross Section ◽  
Electronic Transition ◽  
Continuous Wave ◽  
Peroxy Radical ◽  
Cross Reaction ◽  
Peroxy Radicals ◽  
Absorption Cross ◽  
Time Resolved

The absolute absorption cross section of the ethyl peroxy radical, C2H5O2, in the Ã←X ̃ electronic transition with the peak wavelength at 7596 cm-1, has been determined by the method of dual wavelengths time resolved continuous wave cavity ring down spectroscopy. C2H5O2 radicals were generated from pulsed 351 nm photolysis of C2H6/Cl2 mixture in presence of O2 and detected on one of the CRDS paths. Two methods have been applied for the determination of the C2H5O2 absorption cross section: (i) based on Cl-atoms being converted alternatively to either C2H5O2 by adding C2H6 or to hydro peroxy radicals, HO2, by adding CH3OH to the mixture, whereby HO2 was reliably quantified on the second CRDS path in the 21 vibrational overtone at 6638.2 cm-1 (ii) based on the reaction of C2H5O2 with HO2, measured under either excess HO2 or under excess C2H5O2 concentration. Both methods lead to the same peak absorption cross section of C2H5O2,7596 cm-1 = (1.0±0.2) × 10-20 cm2. The rate constant for the cross reaction between of C2H5O2 and HO2 has been measured to be (6.5±1.6) × 10-12 cm3 molecule-1 s-1.

scholarly journals Absolute Absorption Cross-Section of the Ã←X˜ Electronic Transition of the Ethyl Peroxy Radical and Rate Constant of Its Cross Reaction with HO2

Photonics ◽  
2021 ◽  
Vol 8 (8) ◽  
pp. 296
Author(s):  
Cuihong Zhang ◽  
Mirna Shamas ◽  
Mohamed Assali ◽  
Xiaofeng Tang ◽  
Weijun Zhang ◽  
...  
Keyword(s):  
Cross Section ◽  
Rate Constant ◽  
Absorption Cross Section ◽  
Electronic Transition ◽  
Continuous Wave ◽  
Peroxy Radical ◽  
Cross Reaction ◽  
Peroxy Radicals ◽  
Absorption Cross ◽  
Time Resolved

The absolute absorption cross-section of the ethyl peroxy radical C2H5O2 in the Ã←X˜ electronic transition with the peak wavelength at 7596 cm−1 has been determined by the method of dual wavelengths time resolved continuous wave cavity ring down spectroscopy. C2H5O2 radicals were generated from pulsed 351 nm photolysis of C2H6/Cl2 mixture in presence of 100 Torr O2 at T = 295 K. C2H5O2 radicals were detected on one of the CRDS paths. Two methods have been applied for the determination of the C2H5O2 absorption cross-section: (i) based on Cl-atoms being converted alternatively to either C2H5O2 by adding C2H6 or to hydro peroxy radicals, HO2, by adding CH3OH to the mixture, whereby HO2 was reliably quantified on the second CRDS path in the 2ν1 vibrational overtone at 6638.2 cm−1 (ii) based on the reaction of C2H5O2 with HO2, measured under either excess HO2 or under excess C2H5O2 concentration. Both methods lead to the same peak absorption cross-section for C2H5O2 at 7596 cm−1 of σ = (1.0 ± 0.2) × 10−20 cm2. The rate constant for the cross reaction between of C2H5O2 and HO2 has been measured to be (6.2 ± 1.5) × 10−12 cm3 molecule−1 s−1.

scholarly journals Photoelectric absorption cross section of silicon near the bandgap from room temperature to sub-Kelvin temperature

AIP Advances ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 025120
Author(s):  
C. Stanford ◽  
M. J. Wilson ◽  
B. Cabrera ◽  
M. Diamond ◽  
N. A. Kurinsky ◽  
...  
Keyword(s):  
Cross Section ◽  
Absorption Cross Section ◽  
Room Temperature ◽  
Absorption Cross ◽  
Photoelectric Absorption

scholarly journals Ultraviolet Absorption Cross-Sections of Ammonia at Elevated Temperatures for Nonintrusive Quantitative Detection in Combustion Environments

2021 ◽  
pp. 000370282199044
Author(s):  
Wubin Weng ◽  
Shen Li ◽  
Marcus Aldén ◽  
Zhongshan Li
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Elevated Temperatures ◽  
Uv Absorption ◽  
Energy Utilization ◽  
Quantitative Detection ◽  
Absorption Cross ◽  
Hot Gas

Ammonia (NH3) is regarded as an important nitrogen oxides (NOx) precursor and also as an effective reductant for NOx removal in energy utilization through combustion, and it has recently become an attractive non-carbon alternative fuel. To have a better understanding of thermochemical properties of NH3, accurate in situ detection of NH3 in high temperature environments is desirable. Ultraviolet (UV) absorption spectroscopy is a feasible technique. To achieve quantitative measurements, spectrally resolved UV absorption cross-sections of NH3 in hot gas environments at different temperatures from 295 K to 590 K were experimentally measured for the first time. Based on the experimental results, vibrational constants of NH3 were determined and used for the calculation of the absorption cross-section of NH3 at high temperatures above 590 K using the PGOPHER software. The investigated UV spectra covered the range of wavelengths from 190 nm to 230 nm, where spectral structures of the [Formula: see text] transition of NH3 in the umbrella bending mode, v2, were recognized. The absorption cross-section was found to decrease at higher temperatures. For example, the absorption cross-section peak of the (6, 0) vibrational band of NH3 decreases from ∼2 × 10−17 to ∼0.5 × 10−17 cm2/molecule with the increase of temperature from 295 K to 1570 K. Using the obtained absorption cross-section, in situ nonintrusive quantification of NH3 in different hot gas environments was achieved with a detection limit varying from below 10 parts per million (ppm) to around 200 ppm as temperature increased from 295 K to 1570 K. The quantitative measurement was applied to an experimental investigation of NH3 combustion process. The concentrations of NH3 and nitric oxide (NO) in the post flame zone of NH3–methane (CH4)–air premixed flames at different equivalence ratios were measured.

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