Cation transport in gaseous nitrogen: density and temperature effects

1986 ◽  
Vol 64 (4) ◽  
pp. 777-779 ◽  
Author(s):  
Toshinori Wada ◽  
Norman Gee ◽  
Gordon R. Freeman
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Temperature Effects ◽  
Cation Transport ◽  
Polarization Potential ◽  
Gaseous Nitrogen ◽  
Nitrogen Gas ◽  
High Energies ◽  
Low Energies ◽  
Body Potential

The density-normalized mobility of nμ of cations in nitrogen gas at densities up to nc = 6.7 × 1027 molecules/m3 increases with temperature. At n ≤ 5.7 × 1025 molecules/m3 and T > 250 K, the dominating ion is N4+. At lower temperatures and higher densities, relatively loosely bound clusters N4+(N2), N4+(N2)2, … form. Momentum transfer cross sections for N4+–N2 are governed at low energies by the polarization potential, and at high energies by the hard body potential. The cross section for N2+–N2 at high energies is larger than that for N4+–N2.

scholarly journals Odderon and pomeron as fractal dimension in pp and p̄p total cross-sections

2016 ◽  
Vol 31 (10) ◽  
pp. 1650066 ◽  
Author(s):  
F. S. Borcsik ◽  
S. D. Campos
Keyword(s):  
Fractal Dimension ◽  
Total Cross Section ◽  
Cross Section ◽  
Cross Sections ◽  
Fractal Dimensions ◽  
Total Cross Sections ◽  
High Energies ◽  
Fitting Procedure ◽  
Low Energies ◽  
Section Structure

In this paper, one presents a naive parametrization to [Formula: see text] and [Formula: see text] total cross-sections. The main goal of this parametrization is to study the possible fractal structure present in the total cross-section. The result of the fitting procedure shows two different fractal dimensions: a negative (low-energies) and a positive (high-energies). The negative fractal dimension represents the emptiness of the total cross-section structure and the positive represents the filling up process with the energy increase. Hence, the total cross-section presents a multifractal behavior. At low-energies, the odderon exchange may be associated with the negative fractal dimension and at high-energies, the pomeron may be associated with the positive fractal dimension. Therefore, the exchange of odderons and pomerons may be viewed as a transition from a less well-defined to a more well-defined internal structure, depending on the energy.

scholarly journals The 7Be(p, ?)8B Cross Section at Low Energies

1980 ◽  
Vol 33 (2) ◽  
pp. 177 ◽  
Author(s):  
FC Barker
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Solar Neutrinos ◽  
Model Calculations ◽  
Spectroscopic Factors ◽  
Low Energies ◽  
Standard Values ◽  
Experimental Values ◽  
Parameter Values ◽  
Potential Parameters

The nonresonant part of the 7Be(p, )I)8B cross section at low energies is recalculated by means of a direct-capture potential model, using parameter values determined by fitting 7Li(n, n)7Li and 7Li(n, )I)8Li data. Standard values of the potential parameters and spectroscopic factors give values of the 7Li(n,)I) cross section that are too large. Modified values that fit the thermal-neutron capture cross section predict 7Be(p,)I) cross sections that are much less than the experimental values. Also, shell model calculations predict resonant 7Be(p,)I) cross sections that are smaller than the experimental values. It is suggested that the accepted experimental values of the 7Be(p, )I) cross section may be too large, perhaps due partly to an overlarge accepted value for the 7Li(d, p)8Li cross section, which has been used for normalization purposes. A decrease in the 7Be(p,)I) cross section would reduce the calculated detection rate of solar neutrinos and lessen the discrepancy with the measured value.

Electron Energy Dependence of Amorphization in Zr3Fe

1993 ◽  
Vol 316 ◽  
Author(s):  
A.T. Motta ◽  
L.M. Howe ◽  
P.R. Okamoto
Keyword(s):  
Electron Energy ◽  
Cross Section ◽  
Sharp Increase ◽  
Low Dose ◽  
National Laboratory ◽  
Argonne National Laboratory ◽  
High Energies ◽  
Intermediate Energies ◽  
Low Energies ◽  
Order Of Magnitude

ABSTRACTThis paper reports the results from a study conducted to determine the effect of electron energy on the dose-to-amorphization of Zr3Fe at 23-30 K. Zr3Fe samples were irradiated in the HVEM at Argonne National Laboratory, at energies ranging from 200 to 900 keV. Amorphization occurred at electron energies from 900 keV down to 250 keV. Three distinct regions were observed: between 900 and 700 keV amorphization occurred at a constant low dose of ~ 4 × 1021 e cm-2; a higher plateau at 1022 was observed between 600 and 400 keV, and finally there was a sharp increase in the dose-to-amorphization below 400 keV, so that at 250 keV the necessary dose was an order of magnitude higher than that at 900 keV. In the region below 400 keV there was evidence of a dependence of the dose-to-amorphization on the orientation of the sample with respect to the electron beam. The results can be analyzed in terms of a composite displacement cross section dominated at high energies by displacements of Zr and Fe atoms, by displacements of Fe atoms at intermediate energies and of secondary displacements of lattice atoms by recoil impurities at low energies.

scholarly journals Absolute cross section measurements of 238U(n,f) and 237Np(n,f) in the neutron energy range 1-2.4 MeV

2019 ◽  
Vol 211 ◽  
pp. 03009
Author(s):  
Paula Salvador-Castiñeira ◽  
Franz-Josef Hambsch ◽  
Alf Göök ◽  
Marzio Vidali ◽  
Nigel P. Hawkes ◽  
...  
Keyword(s):  
Cross Section ◽  
Neutron Energy ◽  
Cross Sections ◽  
Energy Region ◽  
Power Plants ◽  
National Physical Laboratory ◽  
Absolute Cross Section ◽  
Neutron Energy Range ◽  
Physical Laboratory ◽  
Low Energies

New standard (n,f) cross sections other than 235U are important to study the relevant cross sections for Generation-IV power plants. A specific need for such standards is for performing new experiments with quasimonoenergetic neutron beams, such as those produced by Van de Graaf accelerators. Neutrons down-scattered to low energies in the experimental environment, so called room-return, become relevant for this type of measurements. Hence, a standard (n,f) cross section with a fission threshold is of great interest, in order to suppress the contribution from room-return background. For this reason we have performed two experiments at the VDG of the National Physical Laboratory to measure absolutely the (n,f) cross sections of 235U, 238U and 237Np in the fast neutron energy region. Our preliminary results are in agreement with the most up-to-date evaluations.

The Scattering of Positrons by Helium: Total Cross Sections up to 270 eV

1975 ◽  
Vol 53 (10) ◽  
pp. 962-967 ◽  
Author(s):  
B. Jaduszliwer ◽  
A. Nakashima ◽  
D. A. L. Paul
Keyword(s):  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Born Approximation ◽  
Reasonable Agreement ◽  
Experimental Results ◽  
Formation Cross Section ◽  
Sum Rule ◽  
Total Cross Sections ◽  
High Energies

The total cross sections for the scattering of positrons by helium have been measured by the method of transmission in the 16 to 270 eV energy range. The experimental results are higher than those of Canter et al. but are in reasonable agreement with recent results of Griffith et al., and at high energies tend towards Born approximation calculations. The integral of the cross section over positron momentum is smaller than the sum rule estimate made by Bransden et al. A tentative value of (0.034 ± 0.017)πa02 is assigned to the positronium formation cross section at threshold.

scholarly journals Taming the Energy Rise of the Total Proton-Proton Cross-Section

Universe ◽  
2019 ◽  
Vol 5 (5) ◽  
pp. 106 ◽  
Author(s):  
Sergey Ostapchenko ◽  
Marcus Bleicher
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Strong Increase ◽  
Momentum Fraction ◽  
Proton Proton ◽  
High Energies ◽  
Model Predictions ◽  
Potential Impact ◽  
Very High

Steep rise of parton densities in the limit of small parton momentum fraction x poses a challenge for describing the observed energy-dependence of the total and inelastic proton-proton cross sections σ p p tot / inel : considering a realistic parton spatial distribution, one obtains a too-strong increase of σ p p tot / inel in the limit of very high energies. We discuss various mechanisms which allow one to tame such a rise, paying special attention to the role of parton-parton correlations. In addition, we investigate a potential impact on model predictions for σ p p tot, related to dynamical higher twist corrections to parton-production processes.

Chemische Reaktionskinematik

1968 ◽  
Vol 23 (12) ◽  
pp. 2084-2090 ◽  
Author(s):  
A. Ding ◽  
A. Henglein ◽  
D. Hyatt ◽  
K. Lacmann
Keyword(s):  
Cross Sections ◽  
Degrees Of Freedom ◽  
Forward Scattering ◽  
Small Shift ◽  
High Energies ◽  
Direct Measurements ◽  
Wide Range ◽  
Ion Energies ◽  
Low Energies ◽  
Velocity Spectra

The velocity spectra and cross sections of reactions of the type X*+D2 → XD++D (X+=Ar+, N2+, CO+) have been found to be independent of the temperature of the target gas ( — 190° to 20°C). The additional forward scattering (as compared to spectator stripping) of the product ion at high energies cannot be explained by the thermal motion of the D2 molecules. A recoil stripping mechanism is proposed. At low energies, an intermediate XD2* is postulated that lives shorter than half a period of rotation and is forward scattered but quickly equilibrates the excess energy among the vibrational degrees of freedom. The reactions of Ar+ and N2+ with CD4 can well be understood by the stripping model over a wide range of energy. At low energies, no preferential forward scattering of the product ion is found as in the corresponding reactions with D2. The strongly unsymmetric broadening of the product ion band together with a small shift to lower velocities indicate a strong interaction of the incident ion with the CD3 group at low energies. The formation of an intermediate complex XCD4+ which isotropically decays is expected at energies of a few tenth of one eV. Direct measurements at such low primary ion energies have not yet been possible.

UNDERSTANDING THE NATURE OF PROTON–AIR CROSS-SECTIONS AT VERY HIGH ENERGIES AND THE IMPLICATIONS

2001 ◽  
Vol 16 (37) ◽  
pp. 2387-2397 ◽  
Author(s):  
BHASKAR DE ◽  
S. BHATTACHARYYA ◽  
P. GUPTAROY
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Cross Section Data ◽  
Section Data ◽  
High Energies ◽  
Production Models ◽  
Simulation Based ◽  
Effective Role ◽  
Very High

The purpose of this paper is to focus on the possible effective role of two relatively less-known models in analyzing comprehensively the very up-to-date data on proton–air inelastic cross-sections at high and ultra high energies. The standard versions of all the familiar simulation-based multiparticle production models, which nowadays normally claim front-ranking positions, address on the contrary, only a small part of the cross-section data for a very limited or sectional range of energy values. Against this background, the relevance and impact of the present study have finally been highlighted.

scholarly journals Antiproton-nucleus annihilation cross section at low energy

2018 ◽  
Vol 182 ◽  
pp. 03013
Author(s):  
H. Aghai–Khozani ◽  
A. Bianconi ◽  
M. Corradini ◽  
R. Hayano ◽  
M. Hori ◽  
...  
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Medical Physics ◽  
Low Energy ◽  
Annihilation Cross Section ◽  
Experimental Result ◽  
Heavy Nuclei ◽  
Fundamental Physics ◽  
Low Energies ◽  
Few Data

The antinucleon-nuclei annihilation cross sections at low energies were systematically measured at CERN in the 80’s and 90’s with the LEAR facility and later with the Antiproton Decelerator. Unfortunately only few data exist for very low energy antiprotons (p<500 MeV/c) on medium and heavy nuclei. A deeper knowledge is required by fundamental physics and can have consequence also in cosmology and medical physics. In order to fill the gap, the ASACUSA Collaboration has very recently measured the annihilation cross section of 100 MeV/c antiprotons on carbon. In the present work the experimental result is presented together with a comparison both with the antineutron data on the same target at the same energies and with the other existing antiproton data at higher energies.

MEASUREMENTS OF ABSOLUTE PAIR PRODUCTION CROSS SECTIONS AT LOW ENERGIES

1958 ◽  
Vol 36 (9) ◽  
pp. 1154-1160 ◽  
Author(s):  
S. Standil ◽  
V. Shkolnik
Keyword(s):  
Pair Production ◽  
Cross Section ◽  
Gamma Rays ◽  
Cross Sections ◽  
Production Cross ◽  
Relative Method ◽  
Low Energies

Using an improved analysis in conjunction with a relative method for the measurement of absolute pair production cross sections, the pair production cross sections per atom of lead have been measured for the gamma rays emitted by Co60 and Sb124. The Z-dependence of this cross section was measured for the Co60 radiation using targets of Al, Fe, Cu, Mo, Ag, Sn, and Pb. The results obtained are generally in agreement with other experimental determinations and are, along with those of other investigators, represented graphically.

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