scholarly journals Positron - Hydrogen Scattering at Intermediate Energies

1996 ◽  
Vol 49 (5) ◽  
pp. 919 ◽  
Author(s):  
Jim Mitroy
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Maximum Energy ◽  
Reaction Cross ◽  
Impact Excitation ◽  
Total Reaction Cross Section ◽  
Positron Impact ◽  
Close Coupling ◽  
Formation Cross Section ◽  
Intermediate Energies

Calculations of positron–hydrogen scattering at intermediate energies up to a maximum energy of 10 Ryd are performed using the close coupling (CC) approach. A large L2 basis of positron–hydrogen channels (28 states) is supplemented by the Ps(1s), Ps(2s) and Ps(2p) channels. The inclusion of the positronium states in the CC expansion leads to a model which can describe most of the physics of the positron–hydrogen system with a reasonable degree of accuracy. In particular, the positronium formation cross section, the total reaction cross section and the ionisation cross section are all in agreement with experiment. The elastic scattering cross section and the cross sections for positron impact excitation of the H(2s) and H(2p) levels are also reported.

A measurement of the cross section for production of He + (2 S ) ions by electron impact excitation of ground state helium ions

1966 ◽  
Vol 290 (1420) ◽  
pp. 74-93 ◽  
Keyword(s):  
Plane Wave ◽  
Cross Section ◽  
Cross Sections ◽  
Absolute Magnitude ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Close Coupling ◽  
Born Cross Section ◽  
The Absolute ◽  
The Cross

A crossed beams method has been used to measure the cross section for the production of He + (2 S ) by electrons incident upon He + (1 S ) in the energy range from threshold to 750 eV. The cross section was measured in arbitrary units with an accuracy of ± 5 % and at the higher energies its energy dependence is in close agreement with that calculated by means of the plane-wave Born approximation. Consequently the cross section has been normalized to the plane-wave Born cross section at energies between 435 and 750 eV to obtain the absolute magnitude. An independent estimate of the absolute magnitude was made to with in ± 30 % using only the experimental parameters, and the absolute cross sections given by the two methods agree within the experimental uncertainties. The normalized cross section is compared with cross sections given by the close-coupling approximation and various Coulomb-Born approximations. At the lower energies the normalized cross section is considerably smaller than any of the theoretical values, but the measurements are consistent with the existence of a finite cross section at threshold if the energy spread of the electron beam is taken in to account.

ALPHA-NUCLEUS TOTAL REACTION CROSS SECTION IN THE RIGID PROJECTILE MODEL USING MICROSCOPIC N-α AMPLITUDE

2001 ◽  
Vol 10 (01) ◽  
pp. 43-53 ◽  
Author(s):  
I. AHMAD ◽  
M. A. ABDULMOMEN ◽  
L. A. AL-KHATTABI
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Reaction Cross Section ◽  
Scattering Amplitude ◽  
Reaction Cross ◽  
Glauber Model ◽  
Total Reaction Cross Section ◽  
Total Reaction ◽  
Rigid Projectile ◽  
Optical Limit Approximation

Coulomb modified Glauber model has been applied to calculate α total reaction cross-section for 12 C , 16 O and 40 Ca nuclei in the rigid projectile model using microscopic N-α amplitude which is evaluated in terms of NN scattering amplitude parameters. Using realistic densities for target nuclei and the same input information, we find that the predictions of the rigid projectile approximation for α reaction cross sections are, in general, in better agreement with the experimental data than those of the optical limit approximation.

scholarly journals Large Basis Calculation of Positron?Hydrogen Scattering at Low Energies

1995 ◽  
Vol 48 (4) ◽  
pp. 645 ◽  
Author(s):  
Jim Mitroy
Keyword(s):  
Cross Sections ◽  
Reaction Cross ◽  
Positronium Formation ◽  
Total Reaction Cross Section ◽  
Close Coupling ◽  
Variational Calculations ◽  
Low Energies ◽  
Coupling Approach ◽  
Channel Space ◽  
Basis Calculation

Calculations of low energy positron-hydrogen scattering using the close coupling approach are reported at low energies. The channel space includes nine physical hydrogen and positronium states and in addition twelve hydrogen and positronium pseudo-states. For energies below the positronium formation threshold, phase shifts are reported for J = 0 to 6 and are believed to have an absolute accuracy of 0�0015 radian or better. Elastic scattering and positronium formation cross sections in the Ore gap for the J = 0 and J = 1 partial waves are essentially identical with previous variational calculations. Total elastic and positronium formation cross sections are reported at incident energies below the ionisation threshold. Cross sections for the excitation of the H(n=2), H(n=3) and Ps( n=2) levels are also reported over a restricted energy range, and the total reaction cross section has been computed and compared with experiment.

scholarly journals Positron Impact Excitation of the nS States of Atomic Hydrogen

Atoms ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 9 ◽  
Author(s):  
Anand K. Bhatia
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Born Approximation ◽  
Atomic Hydrogen ◽  
Impact Excitation ◽  
Orbital Method ◽  
Positron Impact ◽  
Excitation Cross Sections ◽  
Theoretical Results ◽  
Incident Positron

The excitation cross sections of the nS states, n = 2 to 6, of atomic hydrogen at various incident positron energies (10.23 to 300 eV) were calculated using the variational polarized-orbital method. Nine partial waves were used to obtain converged cross sections. The present results should be useful for comparison with results obtained from other theories and approximations. The positron-impact cross section was found to be higher than the electron-impact cross sections. Experimental and other theoretical results are discussed. The threshold law of excitation is discussed and the cross sections in this region were seen to obey the threshold law proportional to ( ln k f ) − 2 . Cross sections were calculated in the Born approximation also and compared to those obtained using the variational polarized orbital method.

scholarly journals Excitation of the lowest autoionizing level of caesium atoms by positron impact

2021 ◽  
Vol 2 (1) ◽  
pp. 77-83
Author(s):  
A. W. Munywoki ◽  
J. Okumu ◽  
C. S Singh
Keyword(s):  
Electron Impact ◽  
Cross Sections ◽  
High Energy ◽  
Impact Excitation ◽  
Electron Impact Excitation ◽  
Distorted Wave ◽  
Positron Impact ◽  
Intermediate Energies ◽  
Threshold Energies ◽  
Determining Factor

We have obtained differential and integral cross sections for the excitation of caesium atom to the lowest autoionizing level by positron impact using the distorted wave approximation. We have also done calculations for electron impact excitation of the same level using the same method and compared our present positron/electron impact results with the available theoretical positron/ electron impact results and experimental electron impact results. It is found that the present positron impact integral cross sections are higher than the cross sections of Pangantiwar and Srivastava at low and intermediate energies, but the results converge as the energy increases in the high energy range. The disagreement at near threshold energies is due to the different distortion potentials used in the two calculations. The charge on the projectile is also a determining factor in the shape of the scattering cross section curves.

Fermi motion and medium effects on reaction cross sections of 13,14,15B + C, Al at intermediate and high energies

2020 ◽  
Vol 35 (36) ◽  
pp. 2050297
Author(s):  
M. Rashdan ◽  
T. A. Abdel-Karim
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Reaction Cross Section ◽  
Reaction Cross ◽  
Glauber Model ◽  
Total Reaction Cross Section ◽  
Boron Isotopes ◽  
Medium Effects ◽  
Fermi Motion ◽  
Reaction Cross Sections

Analysis of reaction cross sections of [Formula: see text] are performed with Glauber model (GM) including medium modifications arising from Fermi motion and in-medium nucleon–nucleon (NN) total reaction cross section. The density distributions of Boron isotopes are described by a deformed-average Fermi shape, whose proton and neutron radii and deformation parameters are derived from relativistic mean field (RMF), harmonic oscillator (HO) and two-parameter Fermi (2pF). These densities can describe the reaction cross section of Boron isotopes except for [Formula: see text] which is better described by an HO core plus extended Gaussian (HOG) or HO plus a modified Yukawa (HOMY) tail, which depends on the 1n separation energy. It is found that Fermi motion effects dominated at intermediate energy, and they are important to describe the data in addition to in-medium effects. In-medium effects, which are incorporated locally, reduced the reaction cross section by about 3–5% at all energies. [Formula: see text] is confirmed as a one-neutron halo nucleus, where a large extended tail is observed in the extracted HOMY and HOG model densities as well as in the extracted radii, where the matter radius of [Formula: see text] is found to be about 2.92 fm, which is larger than that of [Formula: see text] (2.5 fm) and [Formula: see text] (2.82 fm) predicted using the GM model including Fermi motion and in-medium effects.

scholarly journals Inclusive neutrino-nucleus reaction cross sections at intermediate energies

2020 ◽  
Vol 5 ◽  
pp. 29
Author(s):  
T. S. Kosmas ◽  
E. Oset
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Reaction Cross ◽  
Point Of View ◽  
Electron Neutrino ◽  
Muon Capture ◽  
Light Nuclei ◽  
Experimental Point ◽  
Intermediate Energies ◽  
Reaction Cross Sections

Inclusive neutrino-nucleus reaction cross sections at intermediate energies (20 MeV < Ey < 500 MeV) are calculated throughout the periodic table for the most interesting nu­ clei from an experimental point of view. The method used had previously proved to be very accurate in calculating the induced reaction cross section for T=0 light nuclei (12C and 16O) and in the study of other similar processes like the ordinary muon capture. The electron-neutrino (ve) cross section weighted by the Michel distribution is also discussed in conjuction with the existing experimental results at LAMPF and ΚARMEN.

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