Measurements of total and (or) positronium-formation cross sections for positrons scattered by alkali, magnesium, and hydrogen atoms

1996 ◽  
Vol 74 (7-8) ◽  
pp. 313-333 ◽  
Author(s):  
T. S. Stein ◽  
J. Jiang ◽  
W. E. Kauppila ◽  
C. K. Kwan ◽  
H. Li ◽  
...  
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
Theoretical Calculations ◽  
Positronium Formation ◽  
Projectile Energy ◽  
Hydrogen Atoms ◽  
Positron Energy ◽  
Total Cross Sections ◽  
Alkali Atoms ◽  
Low Energies

Recent developments in measurements of total and (or) positronium-formation cross sections for positrons (in the range of 1 to 300 eV) scattered by alkali, magnesium, and hydrogen atoms are reviewed. Measurements of total and positronium (Ps)-formation cross sections for positrons scattered by sodium, potassium, and rubidium have revealed an interesting pattern of differences and similarities between these collision systems. These measurements, together with recent calculations, provide evidence that coupling effects between Ps formation and other scattering channels are very important at low energies for the alkali atoms. The calculations also indicate that formation of Ps in excited states in the cases of potassium and rubidium is more likely than formation in the ground state when the positron energy is greater than about 5 eV. Measurements of total and Ps-formation cross sections for positrons scattered by magnesium are in a preliminary stage, but the differences between them and the results of available theoretical calculations are providing a strong incentive to intensify experimental and theoretical investigations of this collision system. Refinements in a recently developed technique for measuring total cross sections for positrons and electrons scattered by atomic hydrogen have led to preliminary new results for these systems that are in very good agreement with recent theoretical calculations. These measurements, together with the calculations with which they agree, indicate that as the projectile energy is increased through the higher energy range (above 50 eV), the total cross sections for positrons approach the corresponding results for electrons from above, which is the reverse of the relationship between the positron and electron total cross sections in this energy range for all of the room-temperature gases that have been investigated, except possibly for molecular hydrogen.

scholarly journals Ionization Cross Sections in the Collision between Two Ground State Hydrogen Atoms at Low Energies

Atoms ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 31
Author(s):  
Saed J. Al Atawneh ◽  
Örs Asztalos ◽  
Borbála Szondy ◽  
Gergő I. Pokol ◽  
Károly Tőkési
Keyword(s):  
Cross Sections ◽  
Ground State ◽  
Classical Trajectory ◽  
Projectile Energy ◽  
Hydrogen Atoms ◽  
Total Cross Sections ◽  
Low Energies ◽  
Ionization Cross Sections ◽  
Final Channel ◽  
Classical Trajectory Monte Carlo

The interaction between two ground state hydrogen atoms in a collision was studied using the four-body classical trajectory Monte Carlo method. We present the total cross sections for the dominant channels, namely for the single ionization of the target, the ionization of the projectile, resulting from pure ionization, and also from the electron transfer (capture or loss) processes. We also present cross sections for the complete break of the system, resulting in the final channel for four free particles. The calculations were carried out at low energies, relevant to the interest of fusion research. We present our cross sections in the projectile energy range between 2.0 keV and 100 keV and compare them with previously obtained theoretical and experimental results.

scholarly journals Ground State Positronium Formation Cross Sections for Scattering of Positrons from Li

1991 ◽  
Vol 44 (5) ◽  
pp. 515 ◽  
Author(s):  
KK Mukherjee ◽  
N Ranjit Singh ◽  
Keka Basu Choudhury ◽  
PS Mazumdar ◽  
S Brajamani
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
Ground State ◽  
Positronium Formation ◽  
Distorted Wave ◽  
Total Cross Sections ◽  
Wave Approximation ◽  
Theoretical Predictions

Total cross sections for positronium formation in e+-Li scattering have been studied in the framework of the distorted wave approximation in the energy range 1-50 eV by taking consistent account of the effect of the target distortion. The results are compared with existing theoretical predictions.

Gamma-ray yields from the reaction D(p, γ)3He at low energies

1970 ◽  
Vol 48 (24) ◽  
pp. 3059-3061 ◽  
Author(s):  
G. M. Bailey ◽  
G. M. Griffiths ◽  
M. A. Olivo ◽  
R. L. Helmer
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
Gamma Ray ◽  
Total Cross Sections ◽  
Isotropic Component ◽  
Low Energies ◽  
Theoretical Predictions ◽  
Γ Ray ◽  
Deuterated Polyethylene

Total cross sections and measurements of the small isotropic component of the γ-ray yield from the reaction D(p, γ)3He have been determined in the energy range from 57 to 1100 KeV using gas and deuterated polyethylene targets. The results are compared with some theoretical predictions.

Positron–inert-gas-atom elastic DCS measurements

1996 ◽  
Vol 74 (7-8) ◽  
pp. 474-482 ◽  
Author(s):  
W. E. Kauppila ◽  
C. K. Kwan ◽  
D. Przybyla ◽  
S. J. Smith ◽  
T. S. Stein
Keyword(s):  
Cross Sections ◽  
Theoretical Calculations ◽  
Structural Features ◽  
Inert Gas ◽  
Elastic Channel ◽  
Positron Scattering ◽  
Positron Energy ◽  
Direct Ionization ◽  
Intermediate Energies ◽  
Low Energies

In this paper we review prior measurements and report new measurements of elastic differential cross sections (DCSs) obtained in our laboratory for positron scattering by the inert gas atoms He, Ne, Ar, Kr, and Xe. The gases (Ne, Ar, Kr, and Xe) for which low-energy measurements have been made below and above the positronium (Ps)-formation thresholds show evidence that the Ps-formation channel is having an observable "absorption" effect on the elastic scattering channel when compared with calculations that only consider the elastic channel. At low energies where only the elastic channel is open, good agreement is found with available calculations. DCS measurements made at high energies (≥200 eV) for He, Ne, and Ar are also found to be consistent with theoretical calculations. At intermediate energies (above the Ps-formation thresholds and below a few hundred eV) theory has not yet been able to match the relative DCSs obtained experimentally owing to the difficulty of including the effects of the most important inelastic channels (i.e., Ps formation and direct ionization). Some initial attempts by our group to obtain absolute elastic DCSs at fixed scattering angles versus positron energy revealed unexpected structure between 55–60 eV for Ar and at 25 and 200 eV for Kr. Our most recent measurements reported here do not confirm the prior observations of these structural features.

scholarly journals Positronium Formation Cross Sections for Scattering of Positrons from Potassium and Rubidium

1994 ◽  
Vol 47 (3) ◽  
pp. 265
Author(s):  
N Ranjit Singh ◽  
NC Deb ◽  
Th Subodh Chandra Singh ◽  
M Babuyaima Singh ◽  
PS Mazumdar
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
Positronium Formation ◽  
Distorted Wave ◽  
Total Cross Sections ◽  
Wave Approximation ◽  
Theoretical Results

Total cross sections for positronium formation in positron-potassium and positron-rubidium scattering have been calculated in a distorted wave approximation for incident positrons in the energy range 1 to 50 eV. The present results are compared with other theoretical results and with measurement where available.

Comparison of D–T and D– 3 He at low energies

1953 ◽  
Vol 218 (1134) ◽  
pp. 432-438 ◽  
Keyword(s):  
Angular Distribution ◽  
Energy Range ◽  
Cross Section ◽  
Cross Sections ◽  
Coulomb Barrier ◽  
Simple Theory ◽  
Absolute Cross Section ◽  
Total Cross Sections ◽  
Gas Target ◽  
Low Energies

A thin gas target was used to measure the absolute cross-section and angular distribution of α -particles from the two ‘ mirror ’ reactions D– 3 H and D– 3 He for deuteron energies below 45 keV. The reactions were found to be isotropic and the variations of the total cross-sections over the energy range 20 to 45 keV can be expressed by the simple Gamow theory of penetration of the coulomb barrier. The simple theory assuming the same energy-independent nuclear parameters for the mirror nuclei 3 H and 3 He was unable to account for the observed cross-sections of these two reactions.

Neutron total cross sections in the energy range 80 to 150 MeV

1966 ◽  
Vol 85 (1) ◽  
pp. 129-141 ◽  
Author(s):  
D.F. Measday ◽  
J.N. Palmieri
Keyword(s):  
Energy Range ◽  
Cross Sections ◽  
Total Cross Sections

PION-NUCLEON SCATTERING EXPERIMENTS AT LOW ENERGIES: π-p→π0n TOTAL CROSS SECTIONS

2005 ◽  
Vol 20 (08n09) ◽  
pp. 1818-1821
Author(s):  
J. BREITSCHOPF ◽  
M. BAUER ◽  
H. CLEMENT ◽  
M. CRÖNI ◽  
H. DENZ ◽  
...  
Keyword(s):  
Phase Shift ◽  
Cross Sections ◽  
Phase Shift Analysis ◽  
Single Charge ◽  
Charge Exchange Reaction ◽  
Total Cross Sections ◽  
Transmission Technique ◽  
Shift Analysis ◽  
Low Energies ◽  
Pion Nucleon

Total cross sections of the single charge exchange reaction π-p→π0n have been measured at PSI from about 40 to 250 MeV using a transmission technique. Preliminary results show an excellent agreement with predictions from the SAID FA02 phase shift analysis for energies above 70 MeV.

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