The e.p.r. spectrum of vibrationally excited hydroxyl radicals

1971 ◽  
Vol 323 (1555) ◽  
pp. 541-554 ◽  
Keyword(s):  
Gas Phase ◽  
Hydroxyl Radicals ◽  
Hyperfine Coupling ◽  
Vibrational Energy ◽  
Theoretical Calculations ◽  
Coupling Constants ◽  
Hydrogen Atoms ◽  
Vibrationally Excited ◽  
The Matrix ◽  
Van Vleck

The e. p. r. spectrum of vibrationally excited hydroxyl radicals in levels v = 1, 2, 3 and 4 of the 2 II 3/2 ground state has been observed in the reaction between hydrogen atoms and ozone in the gas phase. Although the variation of ∧ -doubling with vibrational energy superficially agrees well with the ‘pure precession’ model of Van Vleck, there is clear evidence that the matrix element <II│ L y │ ∑> decreases considerably with increasing internuclear distance. The form of the decrease in the hyperfine coupling constants with increasing vibrational energy agrees well with that deduced from Kayama’s theoretical calculations.

Observation of initial cracking in hydrogen-charged pure iron

1978 ◽  
Vol 36 (1) ◽  
pp. 602-603
Author(s):  
T. Takeyama ◽  
H. Takahashi
Keyword(s):  
Mechanical Properties ◽  
Hydrogen Embrittlement ◽  
Gas Phase ◽  
Pure Iron ◽  
Gaseous Hydrogen ◽  
Hydrogen Atoms ◽  
Electrolytic Cells ◽  
The Matrix ◽  
Cold Rolled ◽  
Diffusion Of Hydrogen

It is considered that hydrogen atoms in iron dissolve interstitially in the matrix, segregate at some lattice defects, are absorbed at the interface of foreign atoms or inclusion, and/or precipitate as a gas phase. This precipitation of gaseous hydrogen in iron causes the formation of void, microcrack and blister, which affects the mechanical properties of the iron. Fracture due to hydrogen embrittlement may be caused by a crack initiation and growth, and propagation. It is obvious that this fracture depends on the diffusion of hydrogen atoms through the iron. However, the mechanism of hydrogen embrittlement cracking has not been fully explained.The aim of the present work was to investigate the microcrack and microvoid generated by the precipitation of hydrogen charged by cathodic method.Pure iron was cold-rolled to a sheet of 0.5mm thickness. After cutting, specimens were annealed at 700°C for one hour in a vacuum of 10-5torr. The grain size was l0̴20 μm. The specimens were charged with hydrogen by applying cathodic potentials in electrolytic cells containing O.1N-H2SO4 with the addition of 250 mg/ℓsodium arsenite to act as a recombination poison.

THE EFFECTS OF HIGH ENERGY RADIATIONS ON WATER AND AQUEOUS SYSTEMS

1948 ◽  
Vol 26b (9) ◽  
pp. 647-656 ◽  
Author(s):  
F. H. Krenz
Keyword(s):  
Hydroxyl Radicals ◽  
Indirect Effect ◽  
Active Material ◽  
Radiation Chemistry ◽  
High Energy ◽  
Biologically Active ◽  
Hydrogen Atoms ◽  
Vibrationally Excited ◽  
Production Of Hydrogen ◽  
Effects Of Radiation

Radiation chemistry is a study of the chemical effects produced by the high energy particles and quanta usually associated with nuclear mutations. When water absorbs this kind of radiation, it is decomposed into hydrogen and hydrogen peroxide. The primary act of absorption is thought to result in the production of hydrogen atoms and hydroxyl radicals which then react to give the decomposition products. In dilute aqueous solutions the effects of radiation can generally be explained from a consideration of the probable effects of hydrogen atoms and hydroxyl radicals on the solute. This is true when the solute consists of biologically active material. Since biological systems consist largely of water, the "indirect effect" that radiation has upon them through the medium of atoms and radicals produced in the water is very important. In this laboratory an attempt is being made to gain information about the "indirect effect" by investigating the properties of irradiated water. Evidence has been obtained for the production of long lived activity in irradiated water which may be attributed to vibrationally excited "polymers" of water. The extraordinary efficiency of the indirect effect" of radiation is possibly related to properties of these excited polymers.

Photochemical studies of unimolecular processes III. Subsidiary processes in the photolysis of cycloheptatriene

1970 ◽  
Vol 316 (1524) ◽  
pp. 143-151 ◽  
Keyword(s):  
Gas Phase ◽  
Ground State ◽  
Hydrogen Atoms ◽  
Vibrationally Excited ◽  
Sufficient Energy ◽  
Benzyl Radicals

In addition to toluene, the photolysis of cyclo[l. 3. 5]heptatriene (CHT) in the gas phase yields small amounts of benzene, methane, ethane, cyclopentadiene and acetylene. Most of the toluene molecules formed by the photo-isomerization of CHT have sufficient energy to dissociate to benzyl radicals and hydrogen atoms; the small fraction which do are responsible for the first three minor products. Cyclopentadiene and acetylene arise from vibrationally excited ground state CHT molecules with energies greater than 268 ± 12 kJ/mol, bicyclo[2. 2. l]heptadiene being the intermediate involved.

scholarly journals Kinetics and dynamics of near-resonant vibrational energy transfer in gas ensembles of atmospheric interest

2018 ◽  
Vol 376 (2115) ◽  
pp. 20170150 ◽  
Author(s):  
Anthony J. McCaffery
Keyword(s):  
Energy Transfer ◽  
Gas Phase ◽  
Quantum State ◽  
Vibrational Energy ◽  
Chem Phys ◽  
Theoretical Chemistry ◽  
Computational Method ◽  
Vibrationally Excited ◽  
Kinetics And Dynamics ◽  
Kinetics Of

This study of near-resonant, vibration–vibration (V–V) gas-phase energy transfer in diatomic molecules uses the theoretical/computational method, of Marsh & McCaffery (Marsh & McCaffery 2002 J. Chem. Phys. 117 , 503 ( doi:10.1063/1.1489998 )) The method uses the angular momentum (AM) theoretical formalism to compute quantum-state populations within the component molecules of large, non-equilibrium, gas mixtures as the component species proceed to equilibration. Computed quantum-state populations are displayed in a number of formats that reveal the detailed mechanism of the near-resonant V–V process. Further, the evolution of quantum-state populations, for each species present, may be followed as the number of collision cycles increases, displaying the kinetics of evolution for each quantum state of the ensemble's molecules. These features are illustrated for ensembles containing vibrationally excited N 2 in H 2 , O 2 and N 2 initially in their ground states. This article is part of the theme issue ‘Modern theoretical chemistry’.

On the e. p. r. spectrum of vibrationally excited hydroxyl radicals

1973 ◽  
Vol 331 (1587) ◽  
pp. 553-560 ◽  
Keyword(s):  
Gas Phase ◽  
Hydroxyl Radicals ◽  
Diagonal Matrix ◽  
Matrix Elements ◽  
Vibrationally Excited

Recent results by Clough, Curran & Thrush (1971) have suggested that Van Vleck’s concept of 'pure precession’ breaks down in the X 2 II 3/2 state of OH, and in order to explain the gas phase e. p. r. spectrum interactions with several states have to be included. In their work, they have assumed that the off-diagonal matrix elements of B are proportional to overlap between the vibrational wavefunctions of the interacting states. Results from R. K. R. curves suggest that this is not the case. Using theoretical wavefunctions, we calculate ∧ -doubling constants and ∆ g J factors for the v " = 0 to 4 levels of the X 2 II 3/2 . state assuming interaction with A 2 Ʃ + alone. Agreement with experiment is found to be good and it is concluded that pure precession does hold for this molecule.

Benchmark Experimental Gas-Phase Intermolecular Dissociation Energies by the SEP-R2PI Method

2020 ◽  
Vol 71 (1) ◽  
pp. 189-211 ◽  
Author(s):  
Richard Knochenmuss ◽  
Rajeev K. Sinha ◽  
Samuel Leutwyler
Keyword(s):  
Gas Phase ◽  
Vibrational Energy ◽  
Noncovalent Interactions ◽  
Theoretical Calculations ◽  
Interaction Strength ◽  
Closed Shell ◽  
Stimulated Emission ◽  
Laser Method ◽  
Experimental Database ◽  
Dissociation Energies

The gas-phase ground-state dissociation energy D0( S0) of an isolated and cold bimolecular complex is a fundamental measure of the intermolecular interaction strength between its constituents. Accurate D0 values are important for the understanding of intermolecular bonding, for benchmarking high-level theoretical calculations, and for the parameterization of dispersion-corrected density functionals or force-field models that are used in fields ranging from crystallography to biochemistry. We review experimental measurements of the gas-phase D0( S0) and D0( S1) values of 55 different M⋅S complexes, where M is a (hetero)aromatic molecule and S is a closed-shell solvent atom or molecule. The experiments employ the triply resonant SEP-R2PI laser method, which involves M-centered ( S0 → S1) electronic excitation, followed by S1 → S0 stimulated emission spanning a range of S0 state vibrational levels. At sufficiently high vibrational energy, vibrational predissociation of the M⋅S complex occurs. A total of 49 dissociation energies were bracketed to within ≤1.0 kJ/mol, providing a large experimental database of accurate noncovalent interactions.

VIBRATIONAL DISEQUILIBRIUM IN REACTIONS BETWEEN ATOMS AND MOLECULES

1960 ◽  
Vol 38 (10) ◽  
pp. 1769-1779 ◽  
Author(s):  
N. Basco ◽  
R. G. W. Norrish
Keyword(s):  
Hydroxyl Radicals ◽  
Flash Photolysis ◽  
Vibrational Energy ◽  
Electronic Energy ◽  
Reaction Products ◽  
Energy Distributions ◽  
Vibrationally Excited ◽  
Atoms And Molecules ◽  
New Class ◽  
Excited Oxygen

Observations on the production of vibrationally excited oxygen molecules in the flash photolysis of nitrogen peroxide and of ozone have extended previous work on these systems. In the case of nitrogen peroxide it has been shown that oxygen molecules possessing the entire exothermicity of the reaction in the form of vibrational energy are produced. A new class of reactions is reported in which vibrationally excited hydroxyl radicals are produced under isothermal conditions by the reaction O(1D) + RH → OH* + R, in which the energy for excitation is contributed by the electronic energy of the oxygen atom.These and other cases of non-equilibrated energy distributions in reaction products and theories accounting for this phenomenon are reviewed.

Hyperfine coupling constants of muonium-substituted cyclohexadienyl radicals in the gas phase: C6H6Mu, C6D6Mu, C6F6Mu

1997 ◽  
Vol 13 (1-2) ◽  
pp. 181-194 ◽  
Author(s):  
D. G. Fleming ◽  
D. J. Arseneau ◽  
J. (Jun) Pan ◽  
M. Y. Shelley ◽  
M. Senba ◽  
...  
Keyword(s):  
Gas Phase ◽  
Hyperfine Coupling ◽  
Coupling Constants ◽  
Hyperfine Coupling Constants
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