The photolysis of 2,3- and 3,3-dimethyl-1-butene at 147.0 and 184.9 nm

1985 ◽  
Vol 63 (1) ◽  
pp. 62-67 ◽  
Author(s):  
Hélène Deslauriers ◽  
Guy J. Collin
Keyword(s):  
Quantum Yield ◽  
Gas Phase ◽  
Electronic State ◽  
Photon Energy ◽  
Low Pressure ◽  
Decomposition Process ◽  
Primary Decomposition ◽  
Primary Process ◽  
The One

The photofragmentation of 2,3-dimethylbutene and 3,3-dimethylbutene has been studied at 147 and 184.9 nm in the gas phase. The main primary decomposition process at both wavelengths involves the rupture of a β(C—C) bond. The quantum yield for this process is higher than 0.7 at 147 nm and is probably even higher at 184.9 nm. All dimethallyl radicals formed at 147 nm in this process decompose at low pressure, but some of them isomerize from the α,β- to the α,α- structure (and vice versa) — via a 1,4-H transfer — before decomposition. At 184.9 nm, the same primary process is used to get a rough value for the lifetime of the photoexcited molecule, compared with the one made with RRKM calculations by assuming that all the photon energy resides in the vibrational framework of the fundamental electronic state. These lifetimes are about one nanosecond or less.

Photolyse du méthyl-2-butène-1, du méthyl-3-butène-1 et du cis-pentène-2 à 174, 163 et 147 nm

1979 ◽  
Vol 57 (8) ◽  
pp. 863-869 ◽  
Author(s):  
Guy J. Collin ◽  
Hélène Deslauriers ◽  
Sylvain Auclair
Keyword(s):  
Double Bond ◽  
Photon Energy ◽  
Rate Constant ◽  
Pressure Effect ◽  
Low Pressure ◽  
Decomposition Process ◽  
Fragmentation Process ◽  
Quantum Yields ◽  
Methyl Radicals ◽  
Hydrogen Atoms

Photolysis of 2-methyl-1-butene (M2B1), cis-2-pentene (CP2), and 3-methyl-1-butene (M3B1) has been systematically studied at 163 nm. Pressure effect has been measured at 147, 163, and 174 nm. The main fragmentation process of the photoexcited olefine is the C—C split of the bond located in position β relative to the double bond:[Formula: see text] α-Methallyl radicals obtained in the M3B1 and CP2 photolysis decompose partly at low pressure, giving rise to the formation of 1,3-butadiene and hydrogen atoms. β-Methallyl radicals decompose also at low pressure into allene and methyl radicals. Butadiene and allene quantum yields follow the Stern–Volmer law, and this allows us to determine the ratio of the rate constant of dissociation relative to the rate constant of stabilization, kd/ks, through collision of the α- and β-methallyl radicals. From these values, we conclude that the excess of photon energy is not statistically distributed into the fragments, and that the decomposition process follows one (or several) particular law(s).

Photosensitization by Cd(3P1) Atoms. II. Gas Phase Decomposition of Cyclohexane

1972 ◽  
Vol 50 (13) ◽  
pp. 2010-2016 ◽  
Author(s):  
B. L. Kalra ◽  
A. R. Knight
Keyword(s):  
Quantum Yield ◽  
Gas Phase ◽  
Vapor Phase ◽  
Exposure Time ◽  
Molecular Hydrogen ◽  
Primary Decomposition ◽  
Phase Decomposition ◽  
Hydrogen Atoms ◽  
Hydrogen Formation ◽  
Volatile Products

The photodecomposition of cyclohexane sensitized by Cd(3P1) atoms has been studied in the vapor phase at 355 °C. The primary decomposition gives hydrogen atoms and cyclohexyl radicals. The volatile products of the decomposition are H2, cyclohexene, propylene, ethane, ethylene, methane, propane, butadiene, and methylcyclopentane. Products other than H2 and cyclo-C6H10 arise from unimolecular reactions of cyclohexyl radicals, the most important such process being the production of propylene and allyl radicals. Hydrogen yields decrease rapidly with time because of H-atom scavenging reactions involving olefinic products. The quantum yield of molecular hydrogen formation at the shortest exposure time examined is 0.53.

Reactions of thiyl radicals. XII. Triplet mercury photosensitized decomposition of ethyl sulfide in the gas phase

1976 ◽  
Vol 54 (8) ◽  
pp. 1290-1295 ◽  
Author(s):  
Conrad S. Smith ◽  
Arthur R. Knight
Keyword(s):  
Quantum Yield ◽  
Gas Phase ◽  
Quantum Yields ◽  
Second Step ◽  
Primary Process ◽  
Reaction Products ◽  
Process Comparison ◽  
Thiyl Radicals ◽  
Ethyl Radicals ◽  
High Sulfide

The triplet mercury photosensitized decomposition of ethyl sulfide vapour has been studied at 25 °C. The reaction products include C2H4 (Φ0 = 0.075), C2H6 (Φ0 = 0.043), C4H10 (Φ0 = 0.011), C2H5SH (Φ0 = 0.068), 4-methyl-3-thiahexane (Φ0 = 0.011), and C2H5SSC2H5 (Φ0 = 0.175). The overall decomposition quantum yield is 0.38 at high sulfide pressures. The initial decomposition gives principally ethyl radicals and ethylthiyl radicals; a second step which yields ethylene and ethanethiol may account for up to 20% of the primary process. Comparison of the direct and sensitized decompositions indicates that both likely originate in the triplet manifold of ethyl sulfide.Primary decomposition quantum yields have been accurately redetermined for the direct, 254 nm, photolysis of methyl sulfide (0.51), methylethyl sulfide (0.46), and ethyl sulfide (0.49).

Decomposition Process of Benzene in a Low Pressure DC Glow Discharge

2010 ◽  
Vol 130 (11) ◽  
pp. 1004-1008
Author(s):  
Shinobu Hayashi ◽  
Kohki Satoh ◽  
Hidenori Itoh
Keyword(s):  
Glow Discharge ◽  
Low Pressure ◽  
Decomposition Process ◽  
Dc Glow Discharge

scholarly journals Monte Carlo Modeling and Design of Photon Energy Attenuation Layers for >10× Quantum Yield Enhancement in Si-Based Hard X-ray Detectors

Instruments ◽  
2021 ◽  
Vol 5 (2) ◽  
pp. 17
Author(s):  
Eldred Lee ◽  
Kaitlin M. Anagnost ◽  
Zhehui Wang ◽  
Michael R. James ◽  
Eric R. Fossum ◽  
...  
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Quantum Yield ◽  
Photon Energy ◽  
High Efficiency ◽  
High Energy ◽  
Yield Enhancement ◽  
X Ray ◽  
Simulation Results ◽  
Conversion Efficiencies

High-energy (>20 keV) X-ray photon detection at high quantum yield, high spatial resolution, and short response time has long been an important area of study in physics. Scintillation is a prevalent method but limited in various ways. Directly detecting high-energy X-ray photons has been a challenge to this day, mainly due to low photon-to-photoelectron conversion efficiencies. Commercially available state-of-the-art Si direct detection products such as the Si charge-coupled device (CCD) are inefficient for >10 keV photons. Here, we present Monte Carlo simulation results and analyses to introduce a highly effective yet simple high-energy X-ray detection concept with significantly enhanced photon-to-electron conversion efficiencies composed of two layers: a top high-Z photon energy attenuation layer (PAL) and a bottom Si detector. We use the principle of photon energy down conversion, where high-energy X-ray photon energies are attenuated down to ≤10 keV via inelastic scattering suitable for efficient photoelectric absorption by Si. Our Monte Carlo simulation results demonstrate that a 10–30× increase in quantum yield can be achieved using PbTe PAL on Si, potentially advancing high-resolution, high-efficiency X-ray detection using PAL-enhanced Si CMOS image sensors.

High Quantum Yield Dual Emission from Gas-Phase Grown Crystalline Si Nanoparticles

2014 ◽  
Vol 118 (19) ◽  
pp. 10375-10383 ◽  
Author(s):  
A. M. P. Botas ◽  
R. A. S. Ferreira ◽  
R. N. Pereira ◽  
R. J. Anthony ◽  
T. Moura ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Gas Phase ◽  
High Quantum Yield ◽  
Dual Emission ◽  
High Quantum ◽  
Si Nanoparticles

CsOH and its Lighter Homologues – a Comparison

2014 ◽  
Vol 69 (11-12) ◽  
pp. 1229-1236
Author(s):  
Matthias Wörsching ◽  
Constantin Hoch
Keyword(s):  
Gas Phase ◽  
Room Temperature ◽  
Structure Type ◽  
Alkali Metal Hydroxide ◽  
X Ray ◽  
Raman Spectroscopic ◽  
Cesium Hydroxide ◽  
Free Ion ◽  
The One ◽  
First Time

Abstract Cesium hydroxide, CsOH, was for the first time characterised on the basis of single-crystal data. The structure is isotypic to the one of the room-temperature modification of NaOH and can be derived from the NaCl structure type thus allowing the comparison of all alkali metal hydroxide structures. Raman spectroscopic investigations show the hydroxide anion to behave almost as a free ion as in the gas phase. The X-ray investigations indicate possible H atom positions.

Hg(63P1)-sensitized decomposition of HNCO vapor and HNCO–H2 mixtures; the reaction of hydrogen atoms with HNCO

1968 ◽  
Vol 46 (4) ◽  
pp. 527-530 ◽  
Author(s):  
N. J. Friswell ◽  
R. A. Back
Keyword(s):  
Quantum Yield ◽  
Cross Section ◽  
Initial Step ◽  
Primary Process ◽  
Hydrogen Atoms ◽  
Direct Photolysis ◽  
A Value ◽  
The Cross

The Hg(63P1)-sensitized decomposition of HNCO vapor has been briefly studied at 26 °C with HNCO pressures from about 3 to 30 Torr. The products detected were the same as in the direct photolysis, CO, N2, and H2. The quantum yield of CO was appreciably less than unity, compared with a value of 1.5 in the direct photolysis under similar conditions. From this and other observations it is tentatively concluded that a single primary process occurs:[Formula: see text]From a study of the mercury-photosensitized reactions in mixtures of HNCO with H2, it was concluded that hydrogen atoms react with HNCO to form CO but not N2. The initial step is probably addition to form NH2CO. From the competition between reaction [1] and the corresponding quenching by H2, the cross section for reaction [1] was estimated to be 2.3 times that of hydrogen.

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