scholarly journals Zero-Energy Elastic Scattering Length of Positrons from Helium Atoms

1966 ◽  
Vol 36 (4) ◽  
pp. 671-678 ◽  
Author(s):  
Tasuke Hashino
Keyword(s):  
Elastic Scattering ◽  
Scattering Length ◽  
Zero Energy ◽  
Helium Atoms

Dispersion relations and the elastic scattering of electrons by helium atoms

1966 ◽  
Vol 294 (1437) ◽  
pp. 149-159 ◽  
Keyword(s):  
Dispersion Relation ◽  
Elastic Scattering ◽  
Cross Sections ◽  
Scattering Length ◽  
Excitation Threshold ◽  
Zero Energy ◽  
Total Cross Sections ◽  
Scattering Angle ◽  
Helium Atoms ◽  
Microwave Probe

The elastic scattering of electrons by helium is analysed in terms of a dispersion relation for the forward scattering intensity. The zero energy scattering length obtained from this relation agrees well with that derived from application of effective range formulae to observed data on total cross sections and to drift velocity and microwave probe data. It also agrees well with results of exchange-adiabatic calculations. At energies below the excitation threshold these calculations give total and differential cross sections which agree well with observed results except at small scattering angles at energies of 10 eV and below. The dispersion relation gives results agreeing with the calculated at zero scattering angle suggesting that the observed distributions are in error. At energies above the excitation threshold the dispersion relation shows that Born’s first approximation is still considerably in error (by a factor of 2) at zero scattering angle at energies of 300 eV. Experimental data between 100 and 300 eV are consistent with extrapolation to the values given by the dispersion relation for the forward scattered intensity.

scholarly journals On the Elastic Scattering of Electrons of Nearly Zero Energy by Helium Atoms

1963 ◽  
Vol 29 (3) ◽  
pp. 370-373 ◽  
Author(s):  
Tasuke Hashino ◽  
Hidehiko Matsuda
Keyword(s):  
Elastic Scattering ◽  
Zero Energy ◽  
Helium Atoms

Inclusion of a Coulomb interaction potential in a variational model for positronium–helium scattering

2013 ◽  
Vol 91 (2) ◽  
pp. 188-190 ◽  
Author(s):  
Joseph DiRienzi ◽  
Richard J. Drachman
Keyword(s):  
Wave Function ◽  
Short Range ◽  
Scattering Length ◽  
Variational Model ◽  
Coulomb Interactions ◽  
Zero Energy ◽  
Close Coupling ◽  
Helium Atoms ◽  
Coupling Approximation ◽  
Variational Wave

While carrying out investigations on Ps–He scattering it was discovered that it would be possible to improve the results of a previous work on zero-energy scattering of ortho-positronium by helium atoms. The previous work used a model to account for exchange and also attempted to include the effect of short-range Coulomb interactions in the close-coupling approximation. The three terms that were then included did not produce a well-converged result but served to give some justification to the model. Now we improve the calculation by using a simple variational wave function, and derive a much better value of the scattering length. The new result is compared with other computed values, and when an approximate correction due to the van der Waals potential is included the total is consistent with an earlier conjecture.

scholarly journals Getting the Elastic Scattering Length by Observing Inelastic Collisions in Ultracold Metastable Helium Atoms

2004 ◽  
Vol 93 (9) ◽  
Author(s):  
S. Seidelin ◽  
J. Viana Gomes ◽  
R. Hoppeler ◽  
O. Sirjean ◽  
D. Boiron ◽  
...  
Keyword(s):  
Elastic Scattering ◽  
Scattering Length ◽  
Inelastic Collisions ◽  
Metastable Helium ◽  
Helium Atoms

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.

scholarly journals Elementary Particle Scattering Lengths and Resonances

1974 ◽  
Vol 27 (1) ◽  
pp. 13
Author(s):  
DC Peaslee
Keyword(s):  
Optical Potential ◽  
Scattering Length ◽  
Compound System ◽  
Zero Energy ◽  
S Wave ◽  
Nucleon System ◽  
Level Shifts ◽  
Wave States ◽  
Scattering Lengths

An investigation is made of the relation between scattering lengths and resonances in a two-nucleon system. For resonances Eo near zero energy the usual determination of an effective optical potential in mesonic atoms is limited, and it is shown here that the scattering length can only be represented usefully as a sum over resonances of the compound system if the condition IEolDI ~ (PDo)! Is satisfied, where D is the average spacing of s-wave states, p the density of target nucleons and Do the Compton volume of the reduced system. This condition is seen to be valid for mr:, nK and KK interactions and these systems are considered in some detail. It is shown that knowledge of the level shifts of each of these examples can help resolve present uncertainties in associated boson structure.

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