Electron-impact ionization cross sections out of the ground and6P2excited states of cesium

Abstract

An atom trapping technique for determining absolute, total ionization cross sections ͑TICS͒ out of an excited atom is presented. The unique feature of our method is in utilizing Doppler cooling of neutral atoms to determine ionization cross sections. This fluorescence-monitoring experiment, which is a variant of the "trap loss" technique, has enabled us to obtain the experimental electron impact ionization cross sections out of the Cs 6 2 P 3/2 state between 7 eV and 400 eV. CCC, RMPS, and Born theoretical results are also presented for both the ground and excited states of cesium and rubidium. In the low energy region ͑Ͻ11 eV͒ where best agreement between these excited state measurements and theory might be expected, a discrepancy of approximately a factor of five is observed. Above this energy there are significant contributions to the TICS from both autoionization and multiple ionization.

Measurement of the absolute total electron impact cross section on Cs atoms using a magnetooptical trap

“…They revised their measurements with a new apparatus and reported new results [17] for the 5 to 200-eV range, which agreed with the previous experimental results as well as with the CCC calculations. They further extended their work and measured the electron impact ionization cross section of the excited states 6 2 P of Cs by using this technique, as reported by Lukomski et al [18].…”

Electron Scattering by Atoms, Ions, and Molecules

“…Examples of such measurements are the work of Schappe et al (1995) and MacAskill et al (2002). Lukomski et al (2006) showed that the technique can, in principle, also be used to obtain total cross sections from laser-excited initial states that would be hard to measure otherwise. Another trap measurement involving metastable He atoms was carried out by Uhlmann et al (2005).…”

“…Figure 8.27 shows the cross section and the spin asymmetry for electron impact ionization of atomic hydrogen in the near-threshold regime. The PECS results of Bartlett (2006) are compared to a variety of other theoretical and experimental results. As seen from the figure, the PECS theory agrees particularly well with the analytical threshold law and the experimental data.…”

Dynamics of the transport of ionic and atomic cesium in radio frequency-driven ion sources for ITER neutral beam injection

“…In contrast, the transport of cesium during the discharge phases is affected by collisions with background particles. The alkaline metal cesium has a very low ionization potential of 3.89 eV [17]. Therefore, it is necessary to consider both, atomic and ionic cesium flows at the same time.…”

“…Table 1 gives an overview of the included processes and the corresponding dependence of the collision cross section σ on the relative velocity v. A recombination factor of 100% was used in case of the wall recombination processes of Cs + . While long- [17] range Coulomb collisions are taken into account every time step by applying a binary collision model [22], the remaining short-range collisions are treated by the path length estimator algorithm [23], considering an individual probability P Col for each time step:…”