Reply to A. Zecca’s Comment on ‘Positron scattering in helium: Virtual-positronium resonances’ by G.P. Karwasz, D. Pliszka, A. Zecca, R.S. Brusa [Nucl. Instr. and Meth. B 240 (2005) 666]

Karwasz, Grzegorz P.; Brusa, R. S.; Pliszka, D.

doi:10.1016/j.nimb.2006.07.014

Cited by 21 publications

(103 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In San Diego annihilation rates in Ar and Xe were measured, showing a steep rise below 1 eV [15]. In Trento total cross sections in Ar and N 2 were measured [16] with angular resolution better by a factor of 30 than in some previous experiments [12]. Both laboratories confirm the early observations from WSU Detroit on the rise of positron cross sections in the zero-energy limit.…”

supporting

confidence: 68%

“…Such a rise is also predicted by ab-initio theories [17], see [16] for detailed comparison. A phenomenological attempt to apply MERT-like fit for low-energy cross sections in benzene and cyclohexane was done by Karwasz, Pliszka and Zecca [18].In the present paper we apply MERT to positron total cross sections on argon and nitrogen, using recent experimental data from Trento [16]. We use MERT model based on direct solution of Schrödinger equation with polarization potential as originally proposed by O'Malley, Spruch and Rosenberg [1].…”

supporting

confidence: 66%

“…Both laboratories confirm the early observations from WSU Detroit on the rise of positron cross sections in the zero-energy limit. Such a rise is also predicted by ab-initio theories [17], see [16] for detailed comparison. A phenomenological attempt to apply MERT-like fit for low-energy cross sections in benzene and cyclohexane was done by Karwasz, Pliszka and Zecca [18].…”

supporting

confidence: 66%

See 2 more Smart Citations

Applicability of modified effective-range theory to positron-atom and positron-molecule scattering

Idziaszek

Karwasz²

2006

Phys. Rev. A

View full text Add to dashboard Cite

We analyze low-energy scattering of positrons on Ar atoms and N2 molecules using Modified Effective-Range Theory (MERT) developped by O'Malley, Spruch and Rosenberg [Journal of Math. Phys. 2, 491 (1961)]. We use formulation of MERT based on exact solutions of Schrödinger equation with polarization potential rather than low-energy expansions of phase shifts into momentum series. We show that MERT describes well experimental data, provided that effective-range expansion is performed both for s-and p-wave scattering, which dominate in the considered regime of positron energies (0.4 -2 eV). We estimate the values of the s-wave scattering lenght and the effective range for e + -Ar and e + -N2 collisions.Electron (and positron) scattering on atoms at very low energies is dominated by polarization forces. Applicability of MERT to low-energy positron scattering was already hypothesized in [2]. However, first measurements of total cross sections for positron scattering at low energies on noble atoms come only from seventies [10,11].The most systematic data for noble atoms, extending down to 0.3 eV were done in WSU Detroit lab, using positrons from a short-lived C 11 radionuclid, with about 0.1 eV energy resolution [11]. Those data indicated clearly a rise of the cross section in the zero energy limit in gases, like He, Ar, H 2 , Kr, Xe, CO 2 , see [11]. Unfortunately, subsequent experiments [12, 13] used Ne 22 source and thick W-vanes positron moderator, thus worsening energy resolution and not allowing to make reliable measurements below 1 eV. To gain in signal, large apertures and strong guiding magnetic fields were used, leading to underestimation of cross sections -some data showed even a fall in the limit of zero energy for highly polarizable targets, like C 6 H 6 [14].Only two of the most recent set-ups reached energies below 1 eV with good signal-to-noise ratio. In San Diego annihilation rates in Ar and Xe were measured, showing a steep rise below 1 eV [15]. In Trento total cross sections in Ar and N 2 were measured [16] with angular resolution better by a factor of 30 than in some previous experiments [12]. Both laboratories confirm the early observations from WSU Detroit on the rise of positron cross sections in the zero-energy limit. Such a rise is also predicted by ab-initio theories [17], see [16] for detailed comparison. A phenomenological attempt to apply MERT-like fit for low-energy cross sections in benzene and cyclohexane was done by Karwasz, Pliszka and Zecca [18].In the present paper we apply MERT to positron total cross sections on argon and nitrogen, using recent experimental data from Trento [16]. We use MERT model based on direct solution of Schrödinger equation with polarization potential as originally proposed by O'Malley, Spruch and Rosenberg [1]. Differently from earlier works, for the p-wave phaseshift we consider not only the polarization potential but contribution from a general-type short range interaction. This allows us to extend the MERT applicability for positrons to energies above 1 e...

show abstract

supporting

confidence: 68%

supporting

confidence: 66%

supporting

confidence: 66%

See 1 more Smart Citation

Applicability of modified effective-range theory to positron-atom and positron-molecule scattering

Idziaszek

Karwasz²

2006

Phys. Rev. A

View full text Add to dashboard Cite

show abstract

“…[26]). It would also yield the integral cross-section exceeding by a factor of ten or more the values measured [4,27] in a few eV energy range. Clearly, the quantum mechanical hard-sphere model is not applicable to low-energy positron scattering.…”

Section: A Few Ev Energy Range: a Hard-sphere Model Vs Virtual Positmentioning

confidence: 91%

“…For Sueoka data, triangles are his data corrected for angular resolution error, see Ref. [27] for details.…”

Section: Methodsmentioning

confidence: 99%

Positron Scattering on Atoms and Molecules in the Limit of Low Energy

et al. 2006

View full text Add to dashboard Cite

Starting from experimental cross-sections for positron scattering in argon and nitrogen, we examine different energy ranges. In the zero-energy limit the cross-section falls with energy and can be described by modified effective range theory for polarization potential. In a few eV range the cross-sections are constant vs. energy. As far as it is possible to force the elastic scattering phase shifts in a way that both experimental differential cross-sections are reproduced and the total cross-section remains constant in energy, such a model lacks the physical justification. Only the virtualpositronium model, developed recently by Gribakin, reproduces a constant dependence of the total cross-section in a few eV energy range.

show abstract

The influence of f-type function in positron-He/positron-H2 scattering with the Schwinger multichannel method

Sanchez

Lima

2008

Nuclear Instruments and Methods in Physics Research Section B:

View full text Add to dashboard Cite

Reply to A. Zecca’s Comment on ‘Positron scattering in helium: Virtual-positronium resonances’ by G.P. Karwasz, D. Pliszka, A. Zecca, R.S. Brusa [Nucl. Instr. and Meth. B 240 (2005) 666]

Cited by 21 publications

References 14 publications

Applicability of modified effective-range theory to positron-atom and positron-molecule scattering

Applicability of modified effective-range theory to positron-atom and positron-molecule scattering

Positron Scattering on Atoms and Molecules in the Limit of Low Energy

The influence of f-type function in positron-He/positron-H2 scattering with the Schwinger multichannel method

Contact Info

Product

Resources

About