Electron Collision Cross-Sections Measured with the Use of a Magneto-Optical Trap

Abstract

PACS. 34.80i -Electron scattering. PACS. 32.80Pj -Optical cooling of atoms; trapping. PACS. 35.80 + s -Atomic and molecular measurement and techniques.

Electron Scattering by Atoms, Ions, and Molecules

“…In this technique, a laser is used to trap the atoms of interest, and absolute cross sections can be obtained directly from the trap loss when the laser is switched off. 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.…”

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

“…This will be discussed in the results and discussion section. The technique used in our measurements is very similar to that adopted by Schappe et al [4]. The only difference being that they started with an empty trap and recorded the trap loading data, whereas we started with a fully loaded trap with steady-state number N 0 of Cs atoms and recorded the unloading data of the trap.…”

“…These atoms can be easily excited using visible and NIR light sources and are, therefore, very convenient to study electron collisions with excited atomic states, as reported by Zuo et al [3]. Schappe et al [4] reported absolute values for the total electron scattering cross section, in the range from 7 to 500 eV, using a cloud of Rb cold atoms in a MOT. The use of ultracold atoms is very advantageous in this type of measurement, because the total cross section reported here depends only on the electron flux in the electron beam and the relative change in the atomic density of the trapped atoms and not on the total number of atoms.…”

“…In the present work, we report the measurement of the total electron impact scattering cross section of ultracold Cs atoms in a MOT, in the energy range from 80 to 500 eV, using a similar technique to that used by Schappe et al [4]. This technique is based upon the recoil of the target atoms during collision with electrons.…”

“…Following the pioneering work of Schappe et al [4,5], Zecca et al [6] have summarized all previous work on the determination of the total electron impact scattering cross section and electron impact ionization cross section. These include experimental studies in different energy regions (0.3 to 9.0 eV range by Visconti et al [7], 2 to 18 eV range by Jaduszliwer and Chen [8] and 0.3 to 400.0 eV by Brode [9]), theoretical studies including two-state close-coupling calculations (Karule and Peterkop [10], Burke and Mitchell [11]), five-state relativistic close-coupling calculations (Scott et al [12]), polarization-potential calculations (Crown and Russek [13] and Balling [14]), and Breit-Pauli R-matrix calculations (Bartschat [15]).…”