THE MERCURY-PHOTOSENSITIZED DECOMPOSITION OF AMMONIA AND AMMONIA–PROPANE MIXTURES

1964 ◽  
Vol 42 (6) ◽  
pp. 1426-1432 ◽  
Author(s):  
S. Takamuku ◽  
R. A. Back
Keyword(s):  
Quantum Yield ◽  
Temperature Dependence ◽  
Primary Decomposition ◽  
Hydrogen Atoms ◽  
Increasing Temperature

A study of the mercury-photosensitized decomposition of ammonia, both with pure ammonia and with propane added as a scavenger for hydrogen atoms, suggests that the quantum yield of the primary decomposition into H and NH2 is much less than unity at 33 °C and rises with increasing temperature. The interaction of ammonia–propane mixtures with Hg 6(3P1) atoms cannot be explained in terms of simple competitive quenching; a tentative mechanism involving a long-lived Hg 6(3P1) – propane complex and Hg 6(3P0) atoms has been suggested. A temperature dependence in the relative quenching rates of C3H8 and C3D8 has also been observed.

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.

scholarly journals DELAYED LIGHT EMISSION IN GREEN PLANT MATERIALS: TEMPERATURE-DEPENDENCE AND QUANTUM YIELD

1958 ◽  
Vol 44 (10) ◽  
pp. 1035-1047 ◽  
Author(s):  
G. Tollin ◽  
E. Fujimori ◽  
M. Calvin
Keyword(s):  
Quantum Yield ◽  
Temperature Dependence ◽  
Light Emission ◽  
Green Plant ◽  
Plant Materials ◽  
Delayed Light Emission

Article

1998 ◽  
Vol 76 (4) ◽  
pp. 411-413
Author(s):  
Yixing Zhao ◽  
Gordon R Freeman
Keyword(s):  
Absorption Spectrum ◽  
Optical Absorption ◽  
Temperature Dependence ◽  
Optical Absorption Spectrum ◽  
Infrared Light ◽  
Solvated Electron ◽  
Solvated Electrons ◽  
Tert Butanol ◽  
Solvent Dependence ◽  
Increasing Temperature

The energy and asymmetry of the optical absorption spectrum of solvated electrons, es- , change in a nonlinear fashion on changing the solvent through the series HOH, CH3OH, CH3CH3OH, (CH3)2CHOH, (CH3)3COH. The ultimate, quantum-statistical mechanical, interpretation of solvated electron spectra is needed to describe the solvent dependence. The previously reported optical spectrum of es- in tert-butanol was somewhat inaccurate, due to a small amount of water in the alcohol and to limitations of the infrared light detector. The present note records the remeasured spectrum and its temperature dependence. The value of the energy at the absorption maximum (EAmax) is 155 zJ (0.97 eV) at 299 K and 112 zJ (0.70 eV) at 338 K; the corresponding values of G epsilon max (10-22 m2 aJ-1) are 1.06 and 0.74. These unusually large changes are attributed to the abnormally rapid decrease of dielectric permittivity of tert-butanol with increasing temperature. The band asymmetry at 299 K is Wb/Wr = 1.8.Key words: optical absorption spectrum, solvated electron, solvent effects, tert-butanol, temperature dependence.

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.

Temperature Dependence of the Diffusivity–Mobility Ratio in Degenerate Semiconductors in the Presence of a Large Magnetic Field

1973 ◽  
Vol 51 (4) ◽  
pp. 491-492 ◽  
Author(s):  
A. N. Chakravarti ◽  
D. P. Parui
Keyword(s):  
Magnetic Field ◽  
Temperature Dependence ◽  
Low Temperatures ◽  
Mobility Ratio ◽  
Degenerate Semiconductors ◽  
Large Magnetic Field ◽  
Increasing Temperature

The diffusivity–mobility ratio in degenerate semiconductors in the presence of a large magnetic field is found to increase with increasing temperature at a rate which is dependent on temperature at relatively low temperatures. It is also found that, at any given temperature, the ratio is increased by the application of the field.

scholarly journals Temperature dependence of the specific heat and thermodynamic functions AК1М2 alloy, doped strontium

2019 ◽  
Vol 21 (1) ◽  
pp. 35-42 ◽  
Author(s):  
I. N. Ganiev ◽  
S. E. Otajonov ◽  
N. F. Ibrohimov ◽  
M. Mahmudov
Keyword(s):  
Heat Capacity ◽  
Gibbs Energy ◽  
Specific Heat ◽  
Temperature Dependence ◽  
Specific Heat Capacity ◽  
Thermodynamic Functions ◽  
Inverse Relationship ◽  
Alloying Element ◽  
Enthalpy And Entropy ◽  
Increasing Temperature

In the heat «cooling» investigated the temperature dependence of the specific heat capacity and thermodynamic functions doped strontium alloy AK1М2 in the range 298,15—900 K. Mathematical models are obtained that describe the change in these properties of alloys in the temperature range 298.15—900 K, as well as on the concentration of the doping component. It was found that with increasing temperature, specific heat capacity, enthalpy and entropy alloys increase, and the concentration up to 0.5 wt.% of the alloying element decreases. Gibbs energy values have an inverse relationship, i.e., temperature — decreases the content of alloying component — is up to 0.5 wt.% growing.

Photolysis of ketene. I

1968 ◽  
Vol 46 (14) ◽  
pp. 2353-2360 ◽  
Author(s):  
A. N. Strachan ◽  
D. E. Thornton
Keyword(s):  
Carbon Monoxide ◽  
Quantum Yield ◽  
Triplet State ◽  
Singlet State ◽  
Inert Gases ◽  
Inert Gas ◽  
Excited Singlet State ◽  
Intersystem Crossing ◽  
Excited Singlet ◽  
Increasing Temperature

Ketene has been photolyzed at 3660 and 3130 Å both alone and in the presence of the inert gases C4F8 and SF6. The quantum yield of carbon monoxide has been determined at both wavelengths as a function of pressure and temperature. At 3660 Å the quantum yield decreases with increasing pressure but increases with increasing temperature. At 3130 Å the quantum yield with ketene alone remains 2.0 at both 37 and 100 °C at pressures up to 250 mm. At higher pressures of ketene or with added inert gas the quantum yield decreases with increasing pressure. The results are interpreted in terms of a mechanism in which intersystem crossing from the excited singlet state to the triplet state occurs at both wavelengths, and collisional deactivation of the excited singlet state by ketene is single stage at 3660 Å but multistage at 3130 Å.

The photochemical and thermal decompositions of hydrogen sulphide

1953 ◽  
Vol 216 (1126) ◽  
pp. 344-361 ◽  
Keyword(s):  
Thermal Decomposition ◽  
Quantum Yield ◽  
Hydrogen Sulphide ◽  
Low Temperatures ◽  
Room Temperature ◽  
Large Fraction ◽  
Kcal Mole ◽  
Hydrogen Atoms ◽  
Photochemical Decomposition ◽  
Bimolecular Mechanism

The photochemical decomposition of hydrogen sulphide has been investigated at pressures between 8 and 550 mm of mercury and at temperatures between 27 and 650° C, using the narrow cadmium line ( λ 2288) and the broad mercury band (about λ 2550). At room temperature the quantum yield increases with pressure from 1.09 at 30 mm to 1.26 at 200 mm. Above 200 mm pressure there was no further increase in the quantum yield. Temperature had little effect on the quantum yield at λ 2550, but there was a marked increase in the rate of hydrogen production between 500 and 650° C with 2288 Å radiation. This may have been caused by the decomposition of excited hydrosulphide radicals. The results are consistent with a mechanism involving hydrogen atoms and hydrosulphide radicals. The mercury-photosensitized reaction is less efficient than the photochemical decomposition, the quantum yield being only about 0.45. The efficiency increased with temperature and approached unity at high temperatures and pressures. This agrees with the suggestion that a large fraction of the quenching collisions lead to the formation of Hg ( 3 P 0 ) atoms. The thermal decomposition is heterogeneous at low temperatures and becomes homogeneous and of the second order at 650° C. The experimental evidence suggests the bimolecular mechanism 2H 2 S → 2H 2 + S 2 . The activation energies are 25 kcal/mole (heterogeneous) and 50 kcal/mole (homogeneous).

Single-Photon Infrared Photochemistry: Wavelength and Temperature Dependence of the Quantum Yield for the Laser-Induced Ionization of Water

1979 ◽  
pp. 561-568 ◽  
Author(s):  
David M. Goodall ◽  
Rodney C. Greenhow ◽  
Barry Knight ◽  
Joseph F. Holzwarth ◽  
Wolfgang Frisch
Keyword(s):  
Quantum Yield ◽  
Temperature Dependence ◽  
Single Photon ◽  
Ionization Of Water
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