Diffusion and excitation transfer of metastable helium in normal gaseous helium

1952 ◽  
Vol 213 (1115) ◽  
pp. 506-519 ◽  
Keyword(s):  
Diffusion Coefficient ◽  
Elastic Scattering ◽  
Potential Barrier ◽  
Cross Section ◽  
Cross Sections ◽  
Excitation Transfer ◽  
Experimental Results ◽  
Metastable Helium ◽  
Helium Atoms ◽  
Gaseous Helium

The resonance collision of normal and metastable helium atoms has been investigated, and cross-sections calculated for total elastic scattering, diffusion and transfer of excitation. The theoretical diffusion coefficient of metastable atoms in normal helium agrees reasonably well with experimental results of Ebbinghaus and Biondi. As a consequence of a potential barrier in the interaction of the atoms at large separations, the transfer cross-section shows an unusual variation, being small for low collision energies and reaching a maximum of the order of 10 πa 2/0 for collisions about 0.25 eV energy. Comparison is made with experiments by Reynolds.

Differential cross-section measurements in positron–argon collisions

1996 ◽  
Vol 74 (7-8) ◽  
pp. 505-508 ◽  
Author(s):  
R. M. Finch ◽  
Á. Kövér ◽  
M. Charlton ◽  
G. Laricchia
Keyword(s):  
Elastic Scattering ◽  
Differential Cross Section ◽  
Inelastic Scattering ◽  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Differential Cross ◽  
Coupling Effect ◽  
Channel Coupling ◽  
Scattering Cross

Differential cross sections for elastic scattering and ionization in positron–argon collisions as a function of energy (40–150 eV) are reported at 60°. Of particular interest is the energy range 55–60 eV, where earlier measurements by the Detroit group found a drop in the elastic-scattering cross section of a factor of 2. This structure has been tentatively attributed to a cross channel-coupling effect with an open inelastic-scattering channel, most likely ionization. Our results indicate that ionization remains an important channel over the same energy range and only begins to decrease at an energy above 60 eV.

Pseudopotential calculations of elastic scattering of electrons by helium atoms in the range 0–20 eV

1990 ◽  
Vol 68 (1) ◽  
pp. 104-110 ◽  
Author(s):  
B. Plenkiewicz ◽  
P. Plenkiewicz ◽  
J.-P. Jay-Gerin
Keyword(s):  
Experimental Data ◽  
Elastic Scattering ◽  
Momentum Transfer ◽  
Cross Sections ◽  
Theoretical Calculations ◽  
Incident Electron ◽  
Elastic Electron ◽  
Scattering System ◽  
Helium Atoms ◽  
Pseudopotential Calculations

Our earlier pseudopotential calculations on electrons colliding with argon and krypton are extended to consider the elastic electron–helium scattering system. In this paper, we present detailed results for phase shifts, differential, total, and momentum-transfer cross sections for this system for incident electron energies in the range from 0 to 20 eV. These agree very well with existing experimental data and with other theoretical calculations.

The elastic scattering of fast electrons and positrons by hydrogen and helium atoms

1959 ◽  
Vol 250 (1262) ◽  
pp. 337-345 ◽  
Keyword(s):  
Elastic Scattering ◽  
Cross Sections ◽  
Differential Cross ◽  
Born Approximation ◽  
Logarithmic Singularity ◽  
Hydrogen Atoms ◽  
Fast Electrons ◽  
Helium Atoms ◽  
Electrons And Positrons ◽  
Angle Scattering

A simplification of the second Born approximation due to Massey & Mohr is used to calculate the differential cross-sections for the elastic scattering of fast electrons and fast positrons by hydrogen atoms and helium atoms, the method of Dalitz being applied to evaluate all the relevant integrals. Although the logarithmic singularity which is found in the differential cross-section for zero-angle scattering is shown to be absent in the true second Born approximation the use of the simplification of this approximation is justified at sufficiently high impact energies provided the angle of scattering is not too small. The results of the calculations for incident electrons in helium are compared with the available experimental data.

Elastic Scattering of Electrons by Helium Atoms at Intermediate Energies

1993 ◽  
Vol 48 (3) ◽  
pp. 465-468
Author(s):  
V. M. Chhaya ◽  
J. J. Tarwadi ◽  
Smita Chhag
Keyword(s):  
Elastic Scattering ◽  
Energy Range ◽  
Cross Sections ◽  
Differential Cross ◽  
Hydrogen Atoms ◽  
Helium Atoms ◽  
Intermediate Energies ◽  
Born Series ◽  
Electrons And Positrons ◽  
Theoretical Results

Abstract The unitarised Eikonal Born series (UEBS) method has been used successfully by Byron et al. for elastic scattering of electrons and positrons by hydrogen atoms. Here an attempt is made to apply the UEBS method in the case of elastic scattering of electrons by helium atoms. The total and differential cross sections are calculated for the energy range 100-700 eV. The results are compared with experimental and other theoretical results. It is found that the results obtained with the UEBS method agree best with the experimental results.

scholarly journals Do we understand near-forward elastic scattering up to TeV energies?

2015 ◽  
Vol 30 (08) ◽  
pp. 1542006 ◽  
Author(s):  
Claude Bourrely ◽  
Jacques Soffer ◽  
Tai Tsun Wu
Keyword(s):  
Experimental Data ◽  
Elastic Scattering ◽  
Cross Sections ◽  
Phenomenological Model ◽  
Experimental Results ◽  
Proton Proton ◽  
Total Cross Sections

In 1970, on purely theoretical grounds, all total hadronic total cross-sections were predicted to increase without limit for higher and higher energies. This was contrary to the conventional belief at that time. In 1978, an accurate phenomenological model was formulated for the case of proton–proton and antiproton-proton interactions. The parameters for this model were slightly improved in 1984 using the additional available experimental data. Since then, for 30 years these parameters have not changed. This development, including especially the difficult task of formulating this phenomenological model and the comparison of the predictions of this model with later experimental results, is summarized.

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.

The 16O(p, γ)17F Direct Capture Cross Section with an Extrapolation to Astrophysical Energies

1975 ◽  
Vol 53 (17) ◽  
pp. 1672-1686 ◽  
Author(s):  
H. C. Chow ◽  
G. M. Griffiths ◽  
T. H. Hall
Keyword(s):  
Elastic Scattering ◽  
Excited States ◽  
Cross Section ◽  
Cross Sections ◽  
Capture Cross Section ◽  
Scattering Cross Section ◽  
Scattering Data ◽  
Capture Cross ◽  
Scattering Cross ◽  
Elastic Scattering Cross Section

The cross section for the direct radiative capture of protons by 16O has been measured relative to the proton elastic scattering cross section for energies from 800 to 2400 keV (CM). The elastic scattering cross section was normalized to the Rutherford scattering cross section at 385.5 keV. The capture cross section for the reaction 16O(p,γ)17F, which plays a role in hydrogen burning stars, has been extrapolated to stellar energies using a theoretical model which gives a good fit to the measured cross sections. The model involves calculation of electromagnetic matrix elements between initial and final state wave functions evaluated for Saxon–Woods potentials with parameters adjusted to fit both elastic scattering data and binding energies for the ground and first excited states of 17F. Cross sections for capture to the 5/2+ ground and 1/2+ first excited states of 17F in terms of astrophysical S factors valid for energies ≤ 100 keV have been found to be: S5/2+ = (0.317 + 0.0002E) keV b (± 8%); S1/2+ = (8.552 − 0.353E + 0.00013E2) keV b (± 5%).

scholarly journals Drift Velocity and Longitudinal Diffusion Coefficient of Electrons in CO2?Ar Mixtures and Electron Collision Cross Sections for CO2 Molecules

1995 ◽  
Vol 48 (3) ◽  
pp. 357 ◽  
Author(s):  
Y Nakamura
Keyword(s):  
Diffusion Coefficient ◽  
Momentum Transfer ◽  
Cross Section ◽  
Drift Velocity ◽  
Cross Sections ◽  
Vibrational Excitation ◽  
Electron Collision ◽  
Longitudinal Diffusion ◽  
Excitation Cross Sections ◽  
Momentum Transfer Cross Section

The drift velocity and longitudinal diffusion coefficient of electrons in 0�2503% and 1� 97% C02-Ar mixtures were measured for 0�03 ~ E/N ~ 20 Td. The measured electron swarm parameters in the mixtures were used to derive a set of consistent vibrational excitation cross sections for the C02 molecule. Analysis of electron swarms in pure C02 using the present vibrational excitation cross sections was also carried out in order to determine a new momentum transfer cross section for the C02 molecule.

Gaseous and surface reactions involving helium metastable atoms and resonance photons

1957 ◽  
Vol 241 (1225) ◽  
pp. 270-282 ◽  
Keyword(s):  
Cross Sections ◽  
Gold Surface ◽  
Target Atom ◽  
Photon Flux ◽  
Total Cross Sections ◽  
Metastable Helium ◽  
Helium Atoms ◽  
Atom Flux ◽  
Collision Chamber ◽  
Argon Ions

The absolute electron yield ( γ M ) for He (2 3 S ) metastable atoms incident on a gold surface has been measured. The method requires passage of a metastable atom flux through a collision chamber containing argon and thence to the gold surface. From observations on the current of argon ions arising from collisions of the type He (2 3 S ) + A → He + A + + e , together with measurements of the electron emission from the gold surface, γ M may be determined. The total cross-sections for collisions between metastable helium atoms and He, Ne, A and K have been measured and in the asymmetrical cases are observed to rise linearly with increasing atomic number of the target atom. Some collisions involving helium resonance radiation have also been studied. In particular, the photo-electric yield from the gold surface has been determined together with the attenuation of the photon flux in passage through certain noble gases.

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