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 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.

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 Determination of the absorption cross-sections of higher order iodine oxides at 355 nm and 532 nm

2020 ◽  
Author(s):  
Thomas R. Lewis ◽  
Juan Carlos Gómez Martin ◽  
Mark A. Blitz ◽  
Carlos A. Cuevas ◽  
John M. C. Plane ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Atmospheric Chemistry ◽  
Absorption Cross Section ◽  
Absorption Cross ◽  
Time Resolved ◽  
Flight Mass Spectrometry ◽  
Iodine Oxides ◽  
Photo Ionization

Abstract. Iodine oxides (IxOy) play an important role in the atmospheric chemistry of iodine. They are initiators of new particle formation events in the coastal and polar boundary layer and act as iodine reservoirs in tropospheric ozone-depleting chemical cycles. Despite the importance of the aforementioned processes, the photochemistry of these molecules has not been studied in detail previously. Here, we report the first determination of the absorption cross sections of IxOy, x = 2, 3, 5, y = 1–12 at λ = 355 nm by combining pulsed laser photolysis of I2/O3 gas mixtures in air with time-resolved photo-ionization time-of-flight mass spectrometry, using NO2 actinometry for signal calibration. The oxides selected for absorption cross section determinations are those presenting the strongest signals in the mass spectra, where signals containing 4 iodine atoms are absent. The method is validated by measuring the absorption cross section of IO at 355 nm, σ355 nm, IO = (1.2 ± 0.1) ×  10–18 cm2, which is found to be in good agreement with the most recent literature. The results obtained are: σ355 nm, I2O3 

scholarly journals Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

2019 ◽  
Vol 15 ◽  
pp. 2438-2446 ◽  
Author(s):  
Alessandro Iagatti ◽  
Baihao Shao ◽  
Alberto Credi ◽  
Barbara Ventura ◽  
Ivan Aprahamian ◽  
...  
Keyword(s):  
Excited State ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Transient Absorption ◽  
Solvent Polarity ◽  
Photon Absorption ◽  
Absorption Cross ◽  
Time Resolved ◽  
Two Photon Absorption ◽  
Two Photon

In this work we apply a combination of steady state and time resolved luminescence and absorption spectroscopies to investigate the excited-state dynamics of a recently developed molecular photoswitch, belonging to the hydrazone family. The outstanding properties of this molecule, involving fluorescence toggling, bistability, high isomerization quantum yield and non-negligible two-photon absorption cross section, make it very promising for numerous applications. Here we show that the light induced Z/E isomerization occurs on a fast <1 ps timescale in both toluene and acetonitrile, while the excited state lifetime of the Z-form depends on solvent polarity, suggesting a partial charge transfer nature of its low lying excited state. Time-resolved luminescence measurements evidence the presence of a main emission component in the 500–520 nm spectral range, attributed to the Z-isomer, and a very short living blue-shifted emission, attributed to the E-isomer. Finally, transient absorption measurements performed upon far-red excitation are employed as an alternative method to determine the two-photon absorption cross-section of the molecule.

scholarly journals Polymerization Photoinitiators with Near-Resonance Enhanced Two-Photon Absorption Cross-Section: Towards High-Resolution Photoresists with Improved Sensitivity

2020 ◽  
Author(s):  
Caroline Arnoux ◽  
tatsuki konishi ◽  
Emma Van Elslande ◽  
Eric Aymé Poutougnigni ◽  
jean-christophe Mulatier ◽  
...  
Keyword(s):  
Cross Section ◽  
Absorption Cross Section ◽  
Photon Absorption ◽  
Absorption Cross ◽  
Time Resolved ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Material Evaluation ◽  
Near Resonance ◽  
Generation Mechanisms

Synthesis of novel photoinitiators, spectroscopic (UV vis, fluorescence, steady state and time resolved), electrochemical and EPR studies of their photoinduced radical generation mechanisms, Z-scan measurements of their two-photon absorption cross section, two-photon polymerization at 532 nm, with a pulsed ns laser, material evaluation by scanning electron microscopy<br>

Comparative photophysics of sapphyrin derivatives: effects of confused and fused pyrrole rings

2011 ◽  
Vol 15 (09n10) ◽  
pp. 858-864 ◽  
Author(s):  
Jong Min Lim ◽  
Iti Gupta ◽  
Hiroyuki Furuta ◽  
Dongho Kim
Keyword(s):  
Excited State ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Photophysical Properties ◽  
Photon Absorption ◽  
Absorption Cross ◽  
Time Resolved ◽  
Nonradiative Decay ◽  
Two Photon Absorption ◽  
Two Photon

We have investigated the photophysical properties of [22] π-conjugated pentapyrrolic systems, sapphyrin, N-confused and N-fused sapphyrins, with a particular focus on the effects of confused and fused pyrrole rings on their electronic structures using steady-state and time-resolved spectroscopic methods, two-photon absorption cross-section (σ(2)) measurements and quantum mechanical calculations. The absorption spectra of N-confused and N-fused sapphyrins exhibit relatively red-shifted features compared to sapphyrin. In parallel with these spectral features, the reduced HOMO–LUMO gaps were observed in going from sapphyrin to N-fused sapphyrin. In the analysis of the anisotropy of the induced current density (AICD), N-confused and N-fused sapphyrins show that extra π-electrons in confused and fused pyrrole rings contribute to the extension of their π-conjugation pathways. Slightly larger twophoton absorption cross-section values of N-confused and N-fused sapphyrins (3250 and 3900 GM) than that of sapphyrin (2900 GM) also reflect an enhanced π-conjugation effect due to bicyclic and endocyclic extensions in π-conjugation pathways, respectively. The excited singlet and triplet state lifetimes of N-confused sapphyrin were determined to be 60 ps and 1 μs, respectively, due to conformational change and acceleration of nonradiative decay processes, being in a sharp contrast with those of sapphyrin (2.4 ns and 13 μs, respectively). In the case of N-fused sapphyrin, very short singlet excited-state lifetime of 5 ps was detected probably due to the excited-state NH-tautomerization process which enhances nonradiative decay processes.

scholarly journals Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

2019 ◽  
Author(s):  
Alessandro Iagatti ◽  
Baihao Shao ◽  
Alberto Credi ◽  
Barbara Ventura ◽  
Ivan Aprahamian ◽  
...  
Keyword(s):  
Excited State ◽  
Cross Section ◽  
Absorption Cross Section ◽  
Transient Absorption ◽  
Solvent Polarity ◽  
Photon Absorption ◽  
Absorption Cross ◽  
Time Resolved ◽  
Two Photon Absorption ◽  
Two Photon

In this work we apply a combination of steady state and time resolved luminescence and absorption spectroscopies to investigate the excited-state dynamics of a recently developed molecular photoswitch, belonging to the hydrazone family. The outstanding properties of this molecule, involving fluorescence toggling, bistability, high isomerization quantum yield and non-negligible two-photon absorption cross section, make it very promising for numerous applications. Here we show that the light induced Z/E isomerization occurs on a fast <1 ps timescale in both toluene and acetonitrile, while the excited state lifetime decreases with increasing solvent polarity, suggesting a partial charge transfer nature of its low lying excited state. Time resolved luminescence measurements evidence the presence of a main emission component in the 500-520 nm spectral range, attributed to the Z isomer, and a very short living blue-shifted emission, attributed to the E isomer. Finally, transient absorption measurements performed upon far-red excitation are employed as an alternative method to determine the two-photon absorption cross-section of the molecule.

scholarly journals Polymerization Photoinitiators with Near-Resonance Enhanced Two-Photon Absorption Cross-Section: Towards High-Resolution Photoresists with Improved Sensitivity

2020 ◽  
Author(s):  
Caroline Arnoux ◽  
tatsuki konishi ◽  
Emma Van Elslande ◽  
Eric Aymé Poutougnigni ◽  
jean-christophe Mulatier ◽  
...  
Keyword(s):  
Cross Section ◽  
Absorption Cross Section ◽  
Photon Absorption ◽  
Absorption Cross ◽  
Time Resolved ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Material Evaluation ◽  
Near Resonance ◽  
Generation Mechanisms

Synthesis of novel photoinitiators, spectroscopic (UV vis, fluorescence, steady state and time resolved), electrochemical and EPR studies of their photoinduced radical generation mechanisms, Z-scan measurements of their two-photon absorption cross section, two-photon polymerization at 532 nm, with a pulsed ns laser, material evaluation by scanning electron microscopy<br>

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