scholarly journals Positronium Formation in e+ ?Na Scattering

1992 ◽  
Vol 45 (6) ◽  
pp. 757
Author(s):  
N Ranjit Singh ◽  
Keka Basu Choudhury ◽  
PS Mazumdar ◽  
S Brajamani
Keyword(s):  
Cross Section ◽  
Energy Region ◽  
Intermediate Energy ◽  
Positronium Formation ◽  
Distorted Wave ◽  
Formation Cross Section ◽  
Wave Approach

The positronium formation cross section in positron-sodium scattering has been evaluated by employing a distorted wave approach in the low and intermediate energy region. The effect of the positronium� formation cross section on the total cross ection for positron-sodium scattering has also been discussed.

scholarly journals Positron?Lithium Inelastic Scattering with Polarisation Potentials

1991 ◽  
Vol 44 (6) ◽  
pp. 677 ◽  
Author(s):  
M EI-Shabshiry ◽  
SY EI Bakry ◽  
AH Moussa ◽  
MA Abdel-Raouf
Keyword(s):  
Inelastic Scattering ◽  
Cross Section ◽  
Cross Sections ◽  
Excitation Cross Section ◽  
Positronium Formation ◽  
Elastic Channel ◽  
Formation Cross Section ◽  
Positron Energy ◽  
Maximum Value

Positron-lithium inelastic scattering is studied at positron energies ranging from 0�005 to 20 eV using the coupled static model. Two channels are open namely the elastic and positronium formation. The polarisation potentials of the Li atom in the first channel and that of the positronium atom in the second channel are taken into consideration in calculating the corresponding cross sections. The partial cross sections in each channel are calculated for eight values of the total angular momentum (0 ~.e ~ 7). In the elastic channel the total cross section Ull has its maximum value at the lowest energy, and decreases with an increase in positron energy Ki. The total positronium formation cross section has a small dip at 0�1 eV, and maximum value at Ki = 1 �4 eV, and then decreases smoothly with e+ energy. We compare our results with those of Ward et al. (1989) where positronium formation is ignored. The agreement in elastic cross sections improves with e+ energy, while the total collisional cross sections have the closest agreement at 1�0 eV. From this comparison, we find that positronium formation is important in the very low energy region, and the role of the excitation cross section increases steadily with e+ energy.

Positronium formation in low-energy positron–helium scattering

1996 ◽  
Vol 74 (7-8) ◽  
pp. 335-342 ◽  
Author(s):  
J. W. Humberston ◽  
P. Van Reeth
Keyword(s):  
Elastic Scattering ◽  
Cross Section ◽  
Cross Sections ◽  
Wave Functions ◽  
Positronium Formation ◽  
Recent Analysis ◽  
S Wave ◽  
Small Magnitude ◽  
Formation Cross Section ◽  
Positron Collisions

Detailed investigations were made of positron collisions with helium atoms in the Ore gap using a two-channel version of the Kohn variational method with very flexible trial wave functions and accurate correlated helium-target wave functions. Accurate values of the s-wave elastic scattering and positronium-formation cross sections are presented, together with preliminary values of the cross sections for s-wave scattering. The s-wave positronium-formation cross section in helium displays a remarkable similarity in both magnitude and energy dependence to the corresponding cross section in positron–hydrogen scattering, with a rapid rise from the positronium-formation threshold and a more gradual rise thereafter. Its small magnitude is consistent with the findings of a recent analysis of experimental measurements of the positronium-formation cross section. Calculations of the s-wave elastic-scattering cross section above and below the positronium-formation threshold reveal a Wigner "rounded step" at the threshold itself.

Au photofission cross section by quasimonochromatic photons in the intermediate energy region

1989 ◽  
Vol 39 (3) ◽  
pp. 911-916 ◽  
Author(s):  
V. Lucherini ◽  
C. Guaraldo ◽  
E. De Sanctis ◽  
P. Levi Sandri ◽  
E. Polli ◽  
...  
Keyword(s):  
Cross Section ◽  
Energy Region ◽  
Intermediate Energy

Precision measurements of the np scattering differential cross section in the intermediate energy region

2007 ◽  
Vol 126 (1-4) ◽  
pp. 109-112
Author(s):  
P. Mermod ◽  
J. Blomgren ◽  
L. Nilsson ◽  
S. Pomp ◽  
A. Ohrn ◽  
...  
Keyword(s):  
Differential Cross Section ◽  
Cross Section ◽  
Differential Cross ◽  
Energy Region ◽  
Intermediate Energy ◽  
Precision Measurements

Measurement of Intermediate Energy Gamma-Ray Cross Sections

1971 ◽  
Vol 49 (9) ◽  
pp. 1167-1178 ◽  
Author(s):  
L. C. Henry ◽  
T. J. Kennett
Keyword(s):  
Pair Production ◽  
Production Process ◽  
Cross Section ◽  
Cross Sections ◽  
Energy Region ◽  
Gamma Ray ◽  
Intermediate Energy ◽  
Energy Gamma ◽  
Pair Production Process ◽  
Better Than

Gamma-ray cross sections for 30 well-distributed energies from 121 keV to 10.827 MeV in 9 target elements ranging from carbon to uranium have been measured with an accuracy of better than 1%. Deviations from recently quoted theoretical cross sections were observed in the energy region from 6–11 MeV, particularly for high-Z target materials. The approximately Z2 dependent deviations are certainly associated with the elastic pair-production process, the present opinion being that they arise from an overestimation of the effects of atomic–electron screening on the pair cross section in the intermediate energy region.

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