THE QUENCHING OF POTASSIUM RESONANCE RADIATION BY HYDROGEN AND DEUTERIUM

1954 ◽  
Vol 32 (10) ◽  
pp. 961-968 ◽  
Author(s):  
W. M. Smith ◽  
J. A. Stewart ◽  
G. W. Taylor
Keyword(s):  
Cross Sections ◽  
Resonance Radiation ◽  
Temperature Range

The quenching of the resonance radiation of potassium by hydrogen and deuterium has been studied over the temperature range 71 °C to 83 °C. The quenching cross sections at 76 °C were found to be 1.56 × 10−16 cm2 and 1.10 × 10−16 cm2 respectively.

Structural Evolution of Nb/NbC Multilayer Coatings

2007 ◽  
Vol 336-338 ◽  
pp. 879-882 ◽  
Author(s):  
I. Dahan ◽  
M.P. Dariel
Keyword(s):  
Thermal Annealing ◽  
Cross Sections ◽  
Structural Evolution ◽  
Multilayer Coatings ◽  
Subsequent Growth ◽  
Present Communication ◽  
Temperature Range ◽  
Nucleation Stage ◽  
Initial Nucleation ◽  
Interdiffusion Kinetics

The present communication is concerned with the interdiffusion kinetics and the interface breakdown that take place in the Nb/NbC multilayer system as the result of thermal annealing in the 400-800oC temperature range. Within this temperature range carbon is the diffusing species. Carbon diffuses from the carbide layer into the adjacent Nb layer, depleting its concentration within the carbide, causing the nucleation and subsequent growth of an intermediate Nb2C layer and decreasing the width of the original Nb layer. TEM examination of the cross-sections of the multilayer specimens provides data regarding the evolution of the microstructure and, in particular, regarding the initial nucleation stage of the newly formed Nb2C layer.

Temperature dependence of cross sections for 72P1/2 ↔ 72P3/2 excitation transfer and for quenching in cesium, induced in collisions with H2, N2, CH4, and CD4

1982 ◽  
Vol 60 (2) ◽  
pp. 239-244 ◽  
Author(s):  
I. N. Siara ◽  
R. U. Dubois ◽  
L. Krause
Keyword(s):  
Energy Transfer ◽  
Temperature Dependence ◽  
Cross Sections ◽  
Rotational Energy ◽  
Excitation Transfer ◽  
Sensitized Fluorescence ◽  
Temperature Range ◽  
Rotational Energy Transfer ◽  
Order Of Magnitude

The temperature dependence of cross sections for 72P1/2 ↔ 72P3/2 excitation transfer in cesium, as well as the effective quenching of these states, induced in collisions with H2, N2, CH4, and CD4 molecules have been investigated in a series of sensitized fluorescence experiments over a temperature range 390–640 K. The 72P mixing cross sections are of the order of 10−15 cm2 and exceed by at least one order of magnitude similar cross sections for mixing by collisions with Ne, Ar, Kr, and Xe. The large sizes of the mixing cross sections and their variation with temperature are ascribed to a phenomenon of electronic-to-rotational energy transfer.

Specific Features of Interfaces in Cu-Nb Nanocomposites

2014 ◽  
Vol 354 ◽  
pp. 183-188 ◽  
Author(s):  
Elena N. Popova ◽  
I.L. Deryagina ◽  
E.G. Valova-Zaharevskaya ◽  
A.V. Stolbovsky ◽  
N.E. Khlebova ◽  
...  
Keyword(s):  
Thermal Stability ◽  
Uniform Distribution ◽  
Cross Sections ◽  
True Strain ◽  
Structure And Properties ◽  
Temperature Range ◽  
Thermal Stability Of

The structure and properties of multi-rod Cu-Nb composites with the true strain of 10.2 and 12.5 have been studied by TEM, SEM and microhardness measurements. The non-uniform distribution of Nb ribbons throughout the composite cross sections was revealed, at higher strain their structure being more dispersed. In both wires the Cu/Nb interfaces are partly coherent, and the Nb lattice is more distorted at interfaces than in the bulk. The behavior at heating was studied in the temperature range of 300-800оС. In the range of 600-800oC complete coagulation of Nb filaments accompanied with drastic microhardness drop is observed. The thermal stability of Cu-Nb nanocomposites is higher than that of Nb and Cu nanostructured by SPD.

Analysis of a Bow-Free Prestressed Test Specimen

2014 ◽  
Vol 81 (11) ◽  
Author(s):  
E. Suhir ◽  
J. Nicolics
Keyword(s):  
Cross Sections ◽  
Test Specimen ◽  
Thermal Loading ◽  
Thermal Stresses ◽  
Effective Means ◽  
Physical Nature ◽  
Accelerated Testing ◽  
Mode Shift ◽  
Temperature Range ◽  
Operation Conditions

Broadening the temperature range in accelerated testing of electronic products is a typical measure to assure that the product of interest is sufficiently robust. At the same time, a too broad temperature range can lead to the shift in the modes and mechanisms of failure, i.e., result in failures that will not occur in actual operation conditions. Application of mechanical prestressing of the test specimen could be an effective means for narrowing the temperature range during accelerated testing and thereby achieving trustworthy and failure-mode-shift-free accelerated test information. Accordingly, simple engineering predictive models are developed for the evaluation of the magnitude and the distribution of thermal and mechanical stresses in a prestressed bow-free test specimen. A design, in which an electronic or a photonic package is bonded between two identical substrates, is considered. Such a design is often employed in some today's packaging systems, in which the “inner,” functional, component containing active and/or passive devices and interconnects is placed between two identical “outer” components (substrates). The addressed stresses include normal stresses acting in the component cross sections and the interfacial shearing and peeling stresses. Although the specimen as a whole remains bow-free, the peeling stresses might be nevertheless appreciable, since the outer components, if thin enough, deflect to a greater or lesser extent with respect to the inner component. The numerical example has indicated that the maxima of the interfacial thermal shearing and peeling stresses are indeed comparable and that these maxima are on the same order of magnitude as the normal thermal stresses acting in the components' cross sections. It is shown that since the thermal and the prestressing mechanical loads are of different physical nature, the stresses caused by these two load categories are distributed differently over the specimen's length. It is shown also that although it is possible and even advisable to apply mechanical prestressing for a lower temperature range, it is impossible to reproduce the same stress distribution as in the case of thermal loading. The obtained results enable one to shed light on the physics of the state of stress in prestressed bow-free test specimens in electronics and photonics engineering.

Sensitized fluorescence in thallium induced in collisions with Hg(63P1) atoms

1978 ◽  
Vol 56 (7) ◽  
pp. 891-896 ◽  
Author(s):  
M. K. Wade ◽  
M. Czajkowski ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Ground State ◽  
Excitation Transfer ◽  
Resonance Radiation ◽  
Resonance Fluorescence ◽  
Collisional Excitation ◽  
Vapor Mixture ◽  
Sensitized Fluorescence ◽  
Intensity Measurements ◽  
Metallic Vapor

The transfer of excitation from excited mercury atoms to ground-state thallium atoms was investigated using techniques of sensitized fluorescence. A Hg–Tl vapor mixture contained in a quartz cell was irradiated with Hg 2537 Å resonance radiation which caused the mercury atoms to become excited to the 63P1, state. Subsequent collisions between the Hg(63P1) and Tl(62P1/2) atoms resulted in the population of the 82S1/2, 62D, and 72S1/2 thallium states, whose decay gave rise to sensitized fluorescence of wavelengths 3231, 3520, 3776, and 5352 Å. Intensity measurements on the sensitized fluorescence and on the Hg 2537 Å resonance fluorescence, observed at right angles to the direction of excitation, yielded cross sections of 3.0, 0.3, and 0.05 Å2 for collisional excitation transfer from Hg(63P1) to the 82S1/2, 62D, and 72S1/2 states in thallium, respectively. The results are fully consistent with previously determined cross sections for excitation transfer in other binary metallic vapor systems.

Collisional Depolarization of Mercury Resonance Radiation

1973 ◽  
Vol 51 (7) ◽  
pp. 724-726 ◽  
Author(s):  
R. A. Phaneuf ◽  
J. Pitre ◽  
K. Hammond ◽  
L. Krause
Keyword(s):  
Cross Sections ◽  
Resonance Radiation

The depolarization of mercury resonance radiation (2537 Å), induced in collisions of Hg(63p1) atoms with various buffer gases, has been investigated using the method of delayed coincidences. The experiments yielded the following depolarization cross sections. Hg–He, 37.8 Å2; Hg–Ne, 43.5 Å2; Hg–Ar, 72.9 Å2; Hg–Kr, 101 Å2; Hg–Xe, 144 Å2; Hg–N2, 120 Å2.

The determination of cross sections for the quenching of resonance radiation of metal atoms II. Results for potassium, rubidium and caesium

1968 ◽  
Vol 303 (1475) ◽  
pp. 453-465 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Cross Sections ◽  
Resonance Radiation ◽  
Fluorescence Technique ◽  
Metal Atoms

The flame fluorescence technique has been used to study the fluorescence of the metals potassium, rubidium and caesium. Measurements of the intensity of fluorescence of each of these metals in isothermal groups of hydrogen-oxygen flames diluted with each of the gases argon, helium, nitrogen and carbon dioxide have given the following values (Å 2 ) for the square of the distance between the centres of colliding species, σ 2 : for potassium: σ 2 H 2 = 1.03 ± 0.05 σ 2 H 2 O = 0.9 ± 0.3 σ 2 Ar < 0.2 σ 2 He < 0.08 σ 2 N 2 = 5.6 ± 0.3 σ 2 CO = 12.4 ± 0.8 σ 2 CO 2 = 21.4 ± 1.0 σ 2 O 2 = 15.5 ± 1.5 for rubidium: σ 2 H 2 = 0.61 ± 0.1 σ 2 H 2 O = 1.27 ± 0.15 σ 2 Ar < 0.3 σ 2 He < 0.11 σ 2 N 2 = 6.1 ± 0.6 σ 2 CO = 11.8 ± 2.0 σ 2 CO 2 = 24 ± 2 σ 2 O 2 = 25 ± 5 for caesium: σ 2 H 2 = 1.7 ± 0.3 σ 2 H 2 O = 5.5 ± 1.6 σ 2 Ar < 0.9 σ 2 He < 0.4 σ 2 N 2 = 25 ± 6

scholarly journals Processing and application of nuclear data for low temperature criticality assessment

2020 ◽  
Vol 239 ◽  
pp. 14006
Author(s):  
Tim Ware ◽  
David Hanlon ◽  
Tara Hanlon ◽  
Richard Hiles ◽  
Malcolm Lingard ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Low Temperature ◽  
Cross Sections ◽  
Nuclear Data ◽  
Scattering Data ◽  
Monte Carlo Code ◽  
Temperature Range ◽  
Nuclear Data Library ◽  
Criticality Assessment ◽  
Good Agreement

Until recently, criticality safety assessment codes had a minimum temperature at which calculations can be performed. Where criticality assessment has been required for lower temperatures, indirect methods, including reasoned argument or extrapolation, have been required to assess reactivity changes associated with these temperatures. The ANSWERS Software Service MONK® version 10B Monte Carlo criticality code, is capable of performing criticality calculations at any temperature, within the temperature limits of the underlying nuclear data in the BINGO continuous energy library. The temperature range of the nuclear data has been extended below the traditional lower limit of 293.6 K to 193 K in a prototype BINGO library, primarily based on JEFF-3.1.2 data. The temperature range of the thermal bound scattering data of the key moderator materials was extended by reprocessing the NJOY LEAPR inputs used to produce bound data for JEFF-3.1.2 and ENDF/B-VIII.0. To give confidence in the low temperature nuclear data, a series of MONK and MCBEND calculations have been performed and results compared against external data sources. MCBEND is a Monte Carlo code for shielding and dosimetry and shares commonalities to its sister code MONK including the BINGO nuclear data library. Good agreement has been achieved between calculated and experimental cross sections for ice, k-effective results for low temperature criticality benchmarks and calculated and experimentally determined eigenvalues for thermal neutron diffusion in ice. To quantify the differences between ice and water bound scattering data a number of MONK criticality calculations were performed for nuclear fuel transport flask configurations. The results obtained demonstrate good agreement with extrapolation methods. There is a discernible difference in the use of ice and water data.

The determination of cross-sections for the quenching of resonance radiation of metal atoms. IV. Results for lithium

1968 ◽  
Vol 306 (1486) ◽  
pp. 413-421 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Cross Section ◽  
Cross Sections ◽  
Hollow Cathode ◽  
Alkali Metals ◽  
Resonance Radiation ◽  
The Other ◽  
Fluorescence Technique ◽  
Metal Atoms

The flame fluorescence technique has been used to study the fluorescence of lithium in sets of isothermal hydrogen-oxygen flames diluted with each of the gases argon, nitrogen and carbon dioxide. The measurements have given the following values (Å 2 ) for the quenching cross-sections, σ 2 , of lithium in the 2 p 2 P state: σ 2 H 2 = 5⋅2, σ 2 H 2 O ═ 1⋅9, σ 2 N 2 ═ 6⋅75, σ 2 CO ═ 12⋅6, σ 2 CO 2 ═ 9⋅2, σ 2 Ar ≼ 0⋅3. The cross-section is defined as the square of the distance between centres of colliding species. These values are compared with those previously reported (Jenkins 1966, 1968) for the other alkali metals and their interpretation discussed. Details of the high intensity hollow cathode lamp used as a source of lithium resonance radiation are also given.

The determination of cross sections for quenching of resonance radiation of metal atoms III. Results for thallium

1968 ◽  
Vol 303 (1475) ◽  
pp. 467-475 ◽  
Keyword(s):  
Carbon Dioxide ◽  
Cross Section ◽  
Cross Sections ◽  
Rate Constants ◽  
Resonance Radiation ◽  
Metal Atoms ◽  
The Cross

The intensity of fluorescence of thallium has been measured in hydrogen-oxygen flames diluted with each of the gases, argon, helium, nitrogen and carbon dioxide and the measurements used to obtain the following values for the quenching cross section (Å 2 ) for the 7 s 2 S ½ state of thallium σ 2 H 2 = 0.03, σ 2 O 2 = 13.2 ± 1.5, σ 2 N 2 = 6.4 ± 0.2, σ 2 H 2 O = 1.75 ± 0.2, σ 2 CO = 13.6 ± 0.8, σ 2 CO 2 = 32.5 ± 1.5, σ 2 Ar ≤ 0.1, σ 2 He ≤ 0.12. These values for the cross sections have been used to re-calculate the rate constants of the reactions, Tl + H + X → H X + Tl*, where X = H, OH, Cl or Br, from the data obtained by Phillips & Sugden (1961). The re-calculated values are lower than the original ones by a factor of 2.2.

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