Total cross-sections for the scattering of positrons by helium, neon, and argon at intermediate energies

Griffith, T C; Heyland, G R; Lines, K S; Twomey, Tae

doi:10.1007/bf00930108

Cited by 35 publications

(29 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Grand total cross section measurements have been performed up to an energy of 60 eV, with a sharp increase evident in the cross section at the positronium formation threshold, as shown in figure 4, and emphasising the important role that positronium formation plays in the scattering process. The cross section rises smoothly to the maximum energy measured and is in good agreement with previous experimental data [16,17], although some discrepancies remain with older theoretical calculations [3,18]. The recent theory of Bray [5] is in good agreement everywhere except in the region between the positronium formation and ionisation thresholds, where difficulties still remain with their theoretical treatment of the positronium formation problem.…”

Section: Resultssupporting

confidence: 82%

Low energy positron scattering from helium

Sullivan

Makochekanwa

Jones

et al. 2008

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

Low energy positron scattering from helium J P Sullivan, C Makochekanwa, A Jones, P Caradonna and S J BuckmanCentre for Antimatter-Matter Studies RSPhysSE, Australian National University, Canberra ACT 0200, Australia E-mail: jps107@rsphysse.anu.edu.au Abstract. Positron scattering from helium has been historically limited to experiments with energy resolution of 0.5 eV or worse. A new apparatus has been developed that allows the investigation of scattering processes with an energy resolution as good as 30 meV, allowing new experimental insight into positron helium interactions. High resolution measurements of low energy scattering from helium will be presented, with a particular emphasis on the development of benchmark cross sections, the investigation of threshold behaviour and the search for positron scattering resonances.

show abstract

Section: Resultssupporting

confidence: 82%

Low energy positron scattering from helium

Sullivan

Makochekanwa

Jones

et al. 2008

J. Phys.: Conf. Ser.

View full text Add to dashboard Cite

show abstract

“…(13) and (14), we need a large number of partial waves [l," in Eqs. (17) - (19)] in the present intermediateand high-energy region. We carried out convergence tests with respect to radial distance and the step size to preserve numerical accuracy.…”

Section: Theorymentioning

confidence: 68%

“…The experimental points are from Ref. [23] (X ), [19]( 0 ), [16] (+), and [10] and Joachain [38] seem to be better than the DWSB results of Dewangen and Walters [37]. In Fig.…”

Section: =0mentioning

confidence: 83%

See 1 more Smart Citation

Positron scattering from rare gases (He, Ne, Ar, Kr, Xe, and Rn): Total cross sections at intermediate and high energies

Baluja

1992

Phys. Rev. A

View full text Add to dashboard Cite

The total (elastic plus inelastic) cross sections for positron scattering from all the rare gases are reported at intermediate and high energies (20-1000 eV), where experimental data are available for comparison except for the case of radon gas. A complex-optical-potential [ V,~, (ri] approach is employed in which the real part (static plus polarization terms) is calculated from Hartree-Fock or Dirac-Hartree-Fock target wave functions. The imaginary part of the optical potential, i.e. , the absorption potential [ V,b, (r}],is derived for each gas semiempirically from the corresponding electron absorption potential (r}] in the form of V+~, (r}= f (k, r}V, b, (r}, where f (k, r} depends on the incident energy (k') and radial distance (r). The V,b, is taken from the work of Truhlar and co-workers. The V,~, (r) is treated exactly in a partial-wave analysis under the variable-phase method. With the present form of V,~,(r), we are able to reproduce experimental 0, values at all energies considered here. An additional feature of the present results is that the inelastic cross sections compare very well with the measured inelastic (sum of positronium formation, excitation, and ionization cross sections) values for rare gases, where such experimental data are available. The 0. , for the positron-Rn system are predicted. We also discuss the correlation between scattering cross section and the atomic properties. We found that at intermediate and high energies, the positron-gas total cross section can be represented by an analytic formula o, (10 ' cm') =21. 16+aoia03}/EieV}, where ao is the target polarizability and E is the impact energy.This simple form of the o. , in terms of target polarizability works very well for highly polarizable targets such as the alkali-metal atoms and several hydrocarbon molecules. In particular, by using the above analytic formula for 0 "we have shown that our results for Na, K, Rb, C&H4, C,H6, and C3H6 targets compare very well with the experimental data. PACS number(s): 34.80.i, 34.90.+ q, 61.80.Fe

show abstract

“…We have solved the differential equation [4] numerically using the Numerov method for each partial wave. By using a step size of 0.05 a.u.…”

Section: Resultsmentioning

confidence: 99%

Low-energy positron–hydrogen molecule scattering

Sur¹,

Ghosh²

1982

Can. J. Phys.

View full text Add to dashboard Cite

The method of Hara using two centre formalism has been employed to investigate positron-hydrogen molecule scattering at low incident energies. Two model potentials have been used to see the importance of the choice of effective potential. It has been found that the total cross sections are sensitive to the details of the effect~ve potential. The present results are in qualitative agreement with measured values and other existing theoret~cal predictions.On a employe la mCthode de Hara utilisant un formalisme a deux centres pour ttudier la diffusion des positrons par I'hydrogene molCculaire, aux Cnergies d'incidence faibles. Deux potentiels modkles ont ete utilists, pour voir l'importance du choix de potentiel effectif. On a trouvC que les sections efficaces totales sont sens~bles aux ditails du potentiel effectif. Les resultats obtenus sont qualitativement en accord avec les valeurs mesurCes et les autres prkdictions thioriques existantes.[Traduit par le journal]Can. J. Phys.. 60. 597 (1982) Introduction Recently interests have been focused on positron-molecule scattering. Repeated measurements by different groups ( 1 -6), have given impetus to theoretical workers. The experimental situation has been reviewed recently by Griffith (7) and Ghosh et al. (8). Our knowledge of positron-molecule scattering is not satisfactory. The complexity of the problem forces theoretical workers to resort to certain approximations that may not be applicable to the case of positron-atom scattering. The fixed nuclei approximation enjoys the confidence of theoreticians for investigating the problem. By using this approximation, Hara (9) has investigated this problem, employing the two centre formalism. He has introduced the prolate spheroidal coordinates and has taken the 2 axis along the direction of the molecular axis. In his calculations, he has included the static, quadrupole tail of the static and the complete adiabatic polarization potential. He has also performed the calculations using only the dipole part of the polarization potential. The dramatic difference between the results obtained by using two different potentials suggests that the results depend on the details of the potential used. The results for the total cross sections are in fair agreement with the corresponding measured values below 6 eV. However, the position and magnitude of the maximum value of the cross sections are different from those of the experimental data.The York University group have performed a series of calculations (10-12). They have treated the problem in one centre formalism and used spherical polar coordinates. The results of Baille et al. (12) differ appreciably from those of Hara. This difference arises from the choice of their model potentials. A recent study by Darewych et al. ( 13) regarding the use of one and two

show abstract

Total cross-sections for the scattering of positrons by helium, neon, and argon at intermediate energies

Cited by 35 publications

References 13 publications

Low energy positron scattering from helium

Low energy positron scattering from helium

Positron scattering from rare gases (He, Ne, Ar, Kr, Xe, and Rn): Total cross sections at intermediate and high energies

Low-energy positron–hydrogen molecule scattering

Contact Info

Product

Resources

About