Pressure Dependence of Product Yields in the Direct Photolysis of Methanol Vapor at 1849°Å

1973 ◽  
Vol 51 (1) ◽  
pp. 147-148 ◽  
Author(s):  
O. Sonia Herasymowych ◽  
Arthur R. Knight
Keyword(s):  
Quantum Yield ◽  
Exposure Time ◽  
Pressure Dependence ◽  
High Pressures ◽  
Yield Enhancement ◽  
Direct Photolysis ◽  
Methanol Vapor ◽  
Product Yields

Hydrogen and methane yields from the 1849 Å photolysis of methanol vapor in an all-quartz system have been investigated as a function of exposure time and pressure of CH3OH and added CO2.Product yields are decreased by the inert addend, and by the substrate itself at high pressures, in contrast to the collision-induced quantum yield enhancement reported to be occurring in this system.

Direct Photolysis of 2-Propanol Vapor

1972 ◽  
Vol 50 (14) ◽  
pp. 2217-2223 ◽  
Author(s):  
O. S. Herasymowych ◽  
A. R. Knight
Keyword(s):  
Quantum Yield ◽  
Wavelength Range ◽  
Exposure Time ◽  
Yield Enhancement ◽  
Quantum Yields ◽  
Unimolecular Decomposition ◽  
Direct Photolysis ◽  
Volatile Products ◽  
Temperature And Pressure

The photolysis of 2-propanol vapor in the 1800–2000 Å wavelength range has been investigated. The volatile products of the reaction and their quantum yields at 80 °C and 200 Torr substrate pressure are H2 (0.64), CH3COCH3 (0.34), CH4 (0.39), CH3CHO (0.29), CO (0.15), and C2H6 (0.08). A mechanism is proposed that accounts for the observed rate variations with substrate pressure, exposure time, temperature, and pressure of inert addend. Acetone and acetaldehyde undergo significant secondary decomposition and this is the source of CO, CH4, and C2H6. Acetaldehyde is formed in the unimolecular decomposition of C3H7O radicals produced in the primary process.The effects of CO2 and CF4 as inert addends have been examined and it has been established that the quantum yield enhancement through collision induced predissociation that has been reported to occur in methanol is not a characteristic of the 2-propanol photolysis.

The photochemistry of 2-furaldehyde vapour. II. Photodecomposition: direct photolysis at 253.7 and 313 nm and Hg(3P1)-sensitized decomposition

1976 ◽  
Vol 54 (19) ◽  
pp. 3095-3101 ◽  
Author(s):  
A. Gandini ◽  
J. M. Parsons ◽  
R. A. Back
Keyword(s):  
Quantum Yield ◽  
Pressure Dependence ◽  
Low Pressure ◽  
Major Product ◽  
The Other ◽  
Direct Photolysis

The photolysis of furaldehyde vapour at 253.7 nm, 65 °C, and pressures from about 0.2 to 7 torr, produces CO, propyne, allene, furan, cyclopropene, CO2, and C2H2. The quantum yield of CO approaches 2 at low pressure and decreases towards zero with increasing pressure of furaldehyde or added CO2. Yields of the other products also decrease but show a more complex pressure dependence. A mechanism involving excited furaldehyde and excited C4H4O and C3H4 intermediates is suggested.The Hg(3P1)-photosensitized decomposition gives products very similar to those of the direct photolysis. Photolysis at 313 and 366 nm also leads to similar products but in much lower yields, with the major product, CO, having a quantum yield of about 0.01. Some photopolymerization was observed in all Systems.

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.

Quantum yield enhancement of Mn-doped CsPbCl3 perovskite nanocrystals as luminescent down-shifting layer for CIGS solar cells

Solar Energy ◽  
2020 ◽  
Vol 206 ◽  
pp. 473-478 ◽  
Author(s):  
Fan Sui ◽  
Mingyue Pan ◽  
Zhengyan Wang ◽  
Ming Chen ◽  
Wenjie Li ◽  
...  
Keyword(s):  
Solar Cells ◽  
Quantum Yield ◽  
Yield Enhancement ◽  
Perovskite Nanocrystals ◽  
Cigs Solar Cells ◽  
Mn Doped

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.

Dehydration and decomposition of pyrophyllite at high pressures: electrical conductivity and X-ray diffraction studies to 5 GPa

1997 ◽  
Vol 34 (6) ◽  
pp. 875-882 ◽  
Author(s):  
Tara L. Hicks ◽  
Richard A. Secco
Keyword(s):  
Electrical Conductivity ◽  
South African ◽  
Pressure Dependence ◽  
High Pressures ◽  
Ionic Conduction ◽  
Temperature Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Temperature Dependence Of Conductivity

The dehydration and decomposition of South African pyrophyllite were studied in the pressure range 2.5–5.0 GPa and in the temperature (T) range 295–1473 K using both in situ electrical conductivity measurements and X-ray diffraction studies on the recovered samples. Activation energies for conduction (Qc) vary in the range 0.02–0.07 eV for T ≤ 500 K where the dominant conduction mode is electronic, and Qc is in the range 1.10–1.28 eV for T ≥ 500 K where ionic conduction dominates. Abrupt changes in the isobaric temperature dependence of conductivity mark the onset of dehydration and subsequent decomposition into kyanite plus quartz–coesite. At 2.5 GPa, South African pyrophyllite forms the dehydroxylate phase at 760 K with a pressure dependence of ~30 K/GPa and complete decomposition follows at 1080 K with a pressure dependence of ~41 K/GPa. The resulting pressure–temperature phase diagram is in very good agreement with many previous studies at 1 atm (101.325 kPa).

scholarly journals Structure‐guided evolution of Green2 toward photostability and quantum yield enhancement by F145Y substitution

2020 ◽  
Vol 29 (9) ◽  
pp. 1964-1974
Author(s):  
Tingting Sun ◽  
Tianpeng Li ◽  
Ke Yi ◽  
Xiaolian Gao
Keyword(s):  
Quantum Yield ◽  
Yield Enhancement

THE REACTION OF ISOPROPANOL VAPOR WITH Hg 6 (3P1) ATOMS: PART I. PURE SUBSTRATE

1962 ◽  
Vol 40 (6) ◽  
pp. 1134-1139 ◽  
Author(s):  
Arthur R. Knight ◽  
Harry E. Gunning
Keyword(s):  
Quantum Yield ◽  
Hydrogen Production ◽  
Exposure Time ◽  
Resonance Line ◽  
Light Period ◽  
Inert Gas ◽  
Quantum Yields ◽  
Volatile Product ◽  
Intermittent Illumination ◽  
Static Conditions

The reaction of isopropanol vapor with Hg 6(3P1) atoms has been investigated under static conditions at 25 °C under continuous and intermittent illumination. The effect of added inert gas and isolation of the 2537 Å Hg resonance line were also studied.The products of the reaction are H2 (0.72), CH3COCH3 (0.25), CO, CH4, C2H6, CH3CHO, and H2O, with the numbers in parentheses representing the quantum yields at zero exposure time. The non-volatile product remaining in the cell was a mixture of C6-glycols, containing 98.6% pinacol, 1.2% 2-methyl-2,4-pentanediol, and ca. 0.2% or less of 2,5-hexanediol.Under intermittent illumination, the quantum yield of hydrogen production, measured as a function of light period, tL, rose linearly with log tL, and had a constant value of unity for tL < 0.45 msec. A mechanism is proposed involving the primary formation with perfect efficiency of isopropoxy radicals and H atoms.

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