Toward measurements of total cross sections for positrons and electrons scattered by potassium and rubidium atoms

Abstract

We have attempted to measure total cross sections (gr's) for positrons and electrons scattered by potassium and rubidium atoms in the energy range 1 -102 eV using a beam-transmission technique. The measurements are subject to increasing errors as the projectile energy is reduced below 20 eV due to the incomplete discrimination of our apparatus against projectiles scattered through small angles. Our measured positron-K and -Rb gr s each show a peak in the vicinity of 6 eV and decrease substantially as the positron energy is reduced below 6 eV. The observed peaks may be artifacts due to the incompletediscrimination problems referred to above, but careful consideration of those problems does not resolve the marked discrepancies between our low-energy positron-Rb results and those obtained in recent fivestate close-coupling-approximation calculations.PACS number(s): 34.80.i, 34.90.+ q

The Scattering of Positrons and Positronium by Atoms in the Close-Coupling Approximation

“…In the case of the alkali atoms, Na and K, very good agreement has been obtained with the experimental data of the Detroit group [1,2] for both total measured cross-sections and total positronium formation cross-sections. We have also performed calculations, for positron scattering by helium atoms, within the single-active electron approximation [9].…”

“…These have complemented the experimental activity in this field. The Detroit group have reported total cross-sections [1,2] and positronium formation cross-sections [3] in the case of alkali atom targets. Positronium formation cross-sections have also been obtained in positron scattering by argon atoms [3].…”

Positron scattering and annihilation on noble-gas atoms

“…A possible reason for this may lie in the fact that the differential scattering cross section for positron scattering on heavier noble gas atoms is strongly forward peaked. Poor detection of forwardscattered positrons [63] will cause an underestimate in the cross section.…”

Genetic Programming Approach for Electron-Alkali-Metal Atom Collisions

“…The running process stops when the error E is reduced to an acceptable level (0.00001). The training data set which is used based on experimental data for the total scattering cross sections of the collisions of electrons with Na, K, Rb and Cs atoms [16][17][18]. To find…”

“…Alkali-metal atoms have been a subject of interest in several theoretical and experimental investigations in electron-atom collisions because of their various interesting properties: relatively simple structure, low ionization potentials (3.9-5.4eV), large polarizabilities [11,12] and existence of resonance lines in the visible or quartz ultraviolet part of the electromagnetic spectrum (which make the alkali metals interesting as components of stellar atmosphere and other plasmas). The total collisional cross sections have been measured or estimated by different experimental research groups [13][14][15][16][17][18] for electron impact on these atoms. Neural networks have become famous in the field of electron collisions with atoms [19].…”