Reactions of thermal hydrogen atoms at cryogenic temperature below 77 K as studied by ESR. Competitive hydrogen abstraction from ethane and hydrogen iodide in rare-gas matrixes

1980 ◽  
Vol 84 (25) ◽  
pp. 3402-3408 ◽  
Author(s):  
Hachizo Muto ◽  
Keichi Nunome ◽  
Machio Iwasaki
Keyword(s):  
Cryogenic Temperature ◽  
Hydrogen Abstraction ◽  
Hydrogen Iodide ◽  
Rare Gas ◽  
Hydrogen Atoms

Production of Metastable Hydrogen Atoms in Proton—Rare-Gas Collisions

1965 ◽  
Vol 137 (2A) ◽  
pp. A340-A346 ◽  
Author(s):  
D. Jaecks ◽  
B. Van Zyl ◽  
R. Geballe
Keyword(s):  
Rare Gas ◽  
Hydrogen Atoms

Quantum chemistry calculation of reaction pathways of carboxyl groups during coal self-heating

2017 ◽  
Vol 95 (8) ◽  
pp. 824-829 ◽  
Author(s):  
Xuyao Qi ◽  
Haibo Xue ◽  
Haihui Xin ◽  
Ziming Bai
Keyword(s):  
Quantum Chemistry ◽  
Oxidation Process ◽  
Hydrogen Abstraction ◽  
Thermal Parameters ◽  
Reaction Pathways ◽  
Carboxyl Groups ◽  
Heating Process ◽  
Hydrogen Atoms ◽  
Self Heating ◽  
Quantum Chemistry Calculations

During coal self-heating, reactions of carboxyl groups feature in the evolution of the spontaneous combustion of coal. However, their elementary reaction pathways during this process still have not been revealed. This paper selected the Ar–CH2–COOH as a typical carboxyl group containing structure for the analysis of the reaction pathways and enhancement effect on the coal self-heating process by quantum chemistry calculations. The results indicate that the hydrogen atoms in carboxyl groups are the active sites, which undergo the oxidation process and self-reaction process during coal self-heating. They both have two elementary reactions, namely (i) the hydrogen abstraction of –COOH by oxygen and the decarboxylation of the –COO· free radical and (ii) the hydrogen abstraction of –COOH and its pyrolysis. The total enthalpy change and activation energy of the oxidation process are 76.93 kJ/mol and 127.85 kJ/mol, respectively, which indicate that this process is endothermic and will occur at medium temperatures. For the hydrogen abstraction of –COOH by hydrocarbon free radicals, the thermal parameters are 53.53 kJ/mol and 56.13 kJ/mol, respectively, which has the same thermodynamic properties as the oxidation process. However, for the pyrolysis, the thermal parameters are –42.53 kJ/mol and 493.68 kJ/mol, respectively, and is thus exothermic and would not occur until the coal reaches high temperatures. They affect heat accumulation greatly, generate carbon dioxide, and provide new active centers for enhancing the coal self-heating process. The results would be helpful for further understanding of the coal self-heating mechanism.

Reaction pathways of hydroxyl groups during coal spontaneous combustion

2016 ◽  
Vol 94 (5) ◽  
pp. 494-500 ◽  
Author(s):  
Xuyao Qi ◽  
Haibo Xue ◽  
Haihui Xin ◽  
Cunxiang Wei
Keyword(s):  
Activation Energy ◽  
Free Radicals ◽  
Hydrogen Abstraction ◽  
Enthalpy Change ◽  
Reaction Pathways ◽  
Hydroxyl Groups ◽  
Hydrogen Atoms ◽  
Typical Structure ◽  
Self Heating ◽  
Hydroxyl Free Radicals

Hydroxyl groups are one of the key factors for the development of coal self-heating, although their detailed reaction pathways are still unclear. This study investigated the reaction pathways in coal self-heating by the method of quantum chemistry calculation. The Ar–CH2–CH(CH3)–OH was selected as a typical structure unit for the calculation. The results indicate that the hydrogen atoms in hydroxyl groups and R3–CH are the active sites. For the hydrogen atoms in hydroxyl groups, they are directly abstracted by oxygen. For hydrogen atoms in R3–CH, they are abstracted by oxygen at first and generate peroxy-hydroxyl free radicals, which abstract the hydrogen atoms in hydroxyl groups later. The reaction of R3–CH contains three elementary reactions, i.e., the hydrogen abstraction of R3–CH by oxygen, the conjugation reaction between the R3C■ and oxygen atom, and the hydrogen abstraction of –OH by hydroxyl free radicals. Then, the microstructure parameters, IRC pathways, and reaction dynamic parameters were respectively analyzed for the four reactions. For the hydrogen abstraction of –OH by oxygen, the enthalpy change and activation energy are 137.63 and 334.44 kJ/mol, respectively, which will occur at medium temperatures and the corresponding heat effect is great. For the reaction of R3–CH, the enthalpy change and the activation energy are −3.45 and 55.79 kJ/mol, respectively, which will occur at low temperatures while the corresponding heat influence is weak. They both affect heat accumulation and provide new active centers for enhancing the coal self-heating process. The results would be helpful for further understanding of the coal self-heating mechanism.

Multiple Trapping Sites for Hydrogen Atoms in Rare Gas Matrices

1960 ◽  
Vol 32 (4) ◽  
pp. 963-971 ◽  
Author(s):  
S. N. Foner ◽  
E. L. Cochran ◽  
V. A. Bowers ◽  
C. K. Jen
Keyword(s):  
Rare Gas ◽  
Hydrogen Atoms ◽  
Multiple Trapping ◽  
Trapping Sites

Laser Photochemical Vapour Deposition of Epitaxial Ge Films on GaAs from GeH4 Using NH3 as a Sensitiser

1988 ◽  
Vol 129 ◽  
Author(s):  
C.J. Kiely ◽  
C. Jones ◽  
V. Tavitian ◽  
J.G. Eden
Keyword(s):  
Growth Rate ◽  
Photoelectron Spectroscopy ◽  
Vapour Deposition ◽  
Film Growth ◽  
Hydrogen Abstraction ◽  
Auger Spectroscopy ◽  
Hydrogen Atoms ◽  
Production Of Hydrogen ◽  
Substrate Temperatures ◽  
Secondary Ion

ABSTRACTThe viability of ammonia as a sensitiser for the epitaxial growth of Ge on GaAs by laser photochemical vapour deposition (LPVD) has been investigated. Specifically NH3/GeH4/He (0.8/5/95 sccm, 5.5 Torr total pressure) mixtures have been irradiated by a 193nm ArF excimer laser in parallel geometry for substrate temperatures, Ts<400°C. As evidenced by a dramatic acceleration in Ge film growth rate, the NH3 efficiently couples the laser radiation to the GeH4 precursor molecule. The microstructures of LPVD Ge films grown with and without NH3 have been examined by TEM, and the epitaxial nature of both types of films has been verified, although some subtle differences are noted. Chemical analysis of the deposited films has been carried out using Auger spectroscopy, X-ray photoelectron spectroscopy and secondary ion mass spectroscopy. Our results show that there is little or no nitrogen incorporation into the Ge films grown in the presence of NH3, and that hydrogen contamination in our films is minimal. The beneficial effect of NH3 on the growth rate of LPVD Ge films is attributed to the photolytic production of hydrogen atoms which efficiently decompose GeH4 by hydrogen abstraction collisions.

Reactions of thermal hydrogen atoms at cryogenic temperature below 77 K as studied by ESR. 4. Abstraction from propane and isobutane and addition to ethylene in xenon matrixes

1981 ◽  
Vol 85 (10) ◽  
pp. 1326-1332 ◽  
Author(s):  
Machio Iwasaki ◽  
Kazumi Toriyama ◽  
Hachizo Muto ◽  
Keichi Nunome ◽  
Mitsuharu Fukaya
Keyword(s):  
Cryogenic Temperature ◽  
Hydrogen Atoms
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