THE RADIOLYSIS OF HCl–HBr MIXTURES

1963 ◽  
Vol 41 (5) ◽  
pp. 1104-1112 ◽  
Author(s):  
R. C. Rumfeldt ◽  
D. A. Armstrong
Keyword(s):  
Hydrogen Yield ◽  
Hydrogen Atoms ◽  
A Value ◽  
Excited Molecules

Bromine was the only halogen formed in irradiated mixtures of HCl and HBr. A study of its effect on the hydrogen yield from HCl showed that it reacted with the first hydrogen-forming species (or its precursor), and indicated the same yield for this species as did the earlier experiments with chlorine. The results were consistent with thermal hydrogen atoms, formed in the reaction[Formula: see text]as the first hydrogen-forming species, and hot hydrogen atoms, resulting from the dissociation of excited HCl molecules, as the second species.The hydrogen yield from liquid HBr at −79°C was a factor of two larger than that from liquid HCl at the same temperature, and in mixtures of the two the hydrogen yield increased gradually from a value characteristic of pure HCl [Formula: see text] to one characteristic of pure HBr [Formula: see text] The smaller yield from HCl cannot be explained by radical combinations:[Formula: see text] [Formula: see text]in the radiation tracks and must be attributed either to differences in the ion-combination reactions in the two liquids or to a genuinely greater yield of ions and/or dissociative excited molecules in HBr. The hydrogen yield from solid HBr at −196 °C was [Formula: see text].

The X-radiolysis of water vapor containing methanol. Effects of some electron and hydrogen atom scavengers

1968 ◽  
Vol 46 (12) ◽  
pp. 1957-1964 ◽  
Author(s):  
R. S. Dixon ◽  
M. G. Bailey
Keyword(s):  
Nitrous Oxide ◽  
Water Vapor ◽  
Carbon Tetrachloride ◽  
Hydrogen Atom ◽  
Sulfur Hexafluoride ◽  
Hydrogen Yield ◽  
Hydrogen Atoms ◽  
A Value ◽  
Ion Recombination ◽  
Positive Ion

The X-radiolysis of water vapor containing methanol at 125 °C and 1 atm pressure has been studied alone and in the presence of some electron and hydrogen atom scavengers. In water vapor containing methanol only, a plateau value G(H2) = 7.9 ± 0.3 is obtained at all methanol concentrations above 0.5 mole %. Addition of propylene drastically reduces this yield due to efficient scavenging of hydrogen atoms, and values for the total number of H atoms from all precursors g(H)t = 7,5 ± 0.2 and [Formula: see text] are deduced from the competition. An unscavengeable hydrogen yield g(H2) ~ 0.5 is also indicated in mixtures containing propylene. Nitrous oxide and sulfur hexafluoride are found to scavenge electrons efficiently in water vapor containing methanol and the number of hydrogen atoms arising from electron–positive ion recombination is estimated to have a value G = 2.2 ± 0.6. The number of hydrogen atoms arising from processes not involving electrons is g(H) = 5.2 ± 0.3. Carbon tetrachloride reacts efficiently with both electrons and hydrogen atoms, with k(H + CH3OH)/k(H + CCl4) = 0.085. Values of g(H) = 4.9 ± 0.5 and g(H2) = 0.8 ± 0.2 are deduced from mixtures containing carbon tetrachloride.

HYDROGEN FORMATION IN γ-IRRADIATED HYDROGEN CHLORIDE

1962 ◽  
Vol 40 (7) ◽  
pp. 1385-1393 ◽  
Author(s):  
D. A. Armstrong
Keyword(s):  
Hydrogen Chloride ◽  
Solid Hydrogen ◽  
Pure Liquid ◽  
Hydrogen Yield ◽  
Hydrogen Atoms ◽  
A Value ◽  
Low Concentrations ◽  
Electronically Excited ◽  
Γ Rays ◽  
Electronically Excited Molecules

Hydrogen yields from pure liquid and solid hydrogen chloride irradiated with Co60 γ-rays were [Formula: see text](liquid) = 6.50 ± 0.10 and [Formula: see text] (solid) = 3.30 ± 0.10 at −79 °C and −196 °C respectively. The yield from solid hydrogen chloride was only slightly reduced by the addition of chlorine; but the yield from liquid samples was reduced sharply by low concentrations of chlorine to a value of about 4.5, and then much more gradually by larger concentrations. A [Formula: see text] value of 2.1 persisted at 10 mole% chlorine. The results were interpreted in terms of the formation of hydrogen in the reactions[Formula: see text]and[Formula: see text]Reduction of the hydrogen yields by chlorine was attributed to the reactions[Formula: see text]and[Formula: see text]Values of k11/k15 and k11*/k15* were estimated to be 1.7 × 10−3 and 0.10 respectively, while those of GH and GH(hot) were 2.4 ± 0.2 and 4.0 ± 0.2. Electron scavenging by chlorine was considered as a less likely mechanism for reduction of the hydrogen yield. Sources of the thermal and hot hydrogen atoms were examined and it was suggested that the decomposition of electronically excited molecules might be an important mode of decomposition.

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.

RADIATION CHEMISTRY OF CYCLOHEXANE: VI. DILUTE SOLUTIONS OF CARBON TETRACHLORIDE AND CHLOROFORM IN CYCLOHEXANE

1964 ◽  
Vol 42 (3) ◽  
pp. 669-681 ◽  
Author(s):  
J. A. Stone ◽  
P. J. Dyne
Keyword(s):  
Carbon Tetrachloride ◽  
Chemical Reaction ◽  
Physical Process ◽  
Radical Scavenging ◽  
Radiation Chemistry ◽  
Hydrogen Yield ◽  
Halogenated Compounds ◽  
Dilute Solutions ◽  
Hydrogen Atoms

A study of the effect of the addition of small amounts (<3.5%) of the halogenated compounds CCl4, CHCl3, and CDCl3 on the radiolysis of cyclohexane has shown that processes other than radical scavenging occur. At the lowest concentrations of solute that it was practical to employ (0.004 M) cyclohexyl radicals were scavenged without a corresponding reduction in the hydrogen yield. At higher solute concentrations G(H2) was reduced by a physical process which did not involve the scavenging of thermal hydrogen atoms but did lead to chemical reaction involving the solute.

Photodissociation of H2 near Threshold Energies

1970 ◽  
Vol 25 (2) ◽  
pp. 237-242 ◽  
Author(s):  
F. J. Comes ◽  
U. Wenning
Keyword(s):  
Electric Field ◽  
Cross Section ◽  
Configuration Interaction ◽  
Atomic Hydrogen ◽  
Molecular Hydrogen ◽  
Hydrogen Atoms ◽  
Dissociation Cross Section ◽  
Excited Molecules ◽  
Threshold Energies ◽  
Near Threshold

Abstract Measurements of the atomic hydrogen fluorescence (Lyα) yield important information on the dissociation behavior of molecular hydrogen under photon impact. Under certain assumptions the dissociation cross section of the molecule can be deduced from such experiments. By applying an appropriate electric field in the observation region those dissociations leading to the formation of metastable hydrogen atoms can be quantitatively determined. This information opens the possibility to describe the predissociation of the excited H2-molecules in the C-, D-and B″-states. The experiments show that the excited molecules in these particular states dissociate into H(1S) and H(2S) by configuration interaction with the B′-state.

Photolyse du butène-1 dans l'ultraviolet à vide

1973 ◽  
Vol 51 (17) ◽  
pp. 2853-2859 ◽  
Author(s):  
Guy J. Collin
Keyword(s):  
Double Bond ◽  
Hydrogen Atom ◽  
Kinetic Energy ◽  
Thermal Energy ◽  
Hydrogen Atoms ◽  
Excited Molecules

The vacuum u.v. photolysis of 1 -butene was studied in the 147–105 nm region. The main products formed from the fragmentation of excited molecules are allene, 1,3-and 1,2-butadienes, ethylene, and acetylene. The addition of a hydrogen atom to the double bond produces mainly secondary butyl radicals (91%) at 147 nm. At 123.6 nm, this proportion becomes 82%. Thus at shorter wavelengths (10 and 11.6–11.8 eV), hydrogen atoms are produced with a kinetic energy higher than the thermal energy.

A study of α -resorcinol by neutron diffraction

1956 ◽  
Vol 235 (1203) ◽  
pp. 552-559 ◽  
Keyword(s):  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Oxygen Atom ◽  
Neutron Scattering ◽  
Benzene Ring ◽  
Unit Cell ◽  
The Other ◽  
Aromatic Molecule ◽  
Hydrogen Atoms ◽  
A Value

The first study of an aromatic molecule by neutron diffraction, leading to a Fourier projection of the neutron scattering density in the unit cell, gives a value of 1·08 ± 0·04 Å for the length of the C—H bonds which link hydrogen atoms to the benzene ring. The spirals of hydrogen bonds which bind together neighbouring molecules are found to consist of typical ‘long bonds’, with the proton much closer to one oxygen atom than to the other. The O—H distance is 1·02 Å, and it appears that the O, H, O atoms are not collinear.

Photolyse de pentène-1 dans l'ultraviolet à vide

1973 ◽  
Vol 51 (5) ◽  
pp. 724-731 ◽  
Author(s):  
Patrick M. Perrin ◽  
Guy J. Collin
Keyword(s):  
Double Bond ◽  
Low Pressure ◽  
Hydrogen Atoms ◽  
Ethyl Radical ◽  
Excited Molecules

Photolysis of 1-pentene molecules at 8.4 eV (xenon photolysis) and 10.0 eV (krypton photolysis) was studied. Excited molecules decompose to produce mainly ethylene, propadiene, 1,3-butadiene, acetylene, and other minor products. Hydrogen atoms add to the double bond of the monomer and the resulting excited pentyl radical decomposes at low pressure (P < 1 Torr) into propene and ethyl radical. Isomerization of excited 1-pentene molecules is unimportant at these energies.

Rates of elementary processes in the chain reaction between hydrogen and oxygen II. Kinetics of the reaction of hydrogen atoms with molecular oxygen

1963 ◽  
Vol 275 (1363) ◽  
pp. 559-574 ◽  
Keyword(s):  
Molecular Oxygen ◽  
Kinetic Studies ◽  
Negative Temperature ◽  
Product Analysis ◽  
Hydrogen Atoms ◽  
The Third ◽  
Rate Determining Step ◽  
A Value ◽  
Explosion Limit ◽  
Kinetics Of

The addition of molecular oxygen was found to increase the rate of rem oval of hydrogen atoms in a flow system at and below room temperature. Kinetic studies of this process using argon carrier showed that the rate-determining step is the third-order reaction H + O2 + Ar = HO 2 + Ar. (2) Atomic oxygen in small concentrations is produced in the system. Product analysis and measurements of oxygen atom concentrations indicated that the principal reactions removing HO 2 under these conditions are H+HO 2 = H 2 +O 2 , (12a) H+HO 2 = OH+OH, (12b) H+HO 2 = H 2 O+O 2 , (12c) A value for k 2 of 2.2 x 10 -32 cm 6 molecule -2 s -1 was determined at 293 °K. Reaction (2) was found to have a small negative temperature coefficient. These data and values of k 2 from explosion limit studies can be represented by the expression k 2 = 1.3 x 10 -33 exp (+ 1600 + 700/ RT ) cm 6 molecule -2 s -1 in the range 250 to 800 °K. The third-body efficiencies in reaction (2) at 293 °K of He and H 2 O relative to Ar are similar to those obtained from data on the second explosion limit at higher temperatures.

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