title: Particle charge in the bulk of gas discharges.
abstract: An experimental determination of particle charge in a bulk dc discharge plasma covering a wide range of neutral gas pressures, was recently reported [S. Ratynskaia, Phys. Rev. Lett. 93, 085001 (2004)]. The charges obtained were several times smaller than the predictions of collisionless orbital motion limited theory. This discrepancy was attributed to the effect of ion-neutral collisions. In the present paper a more detailed description of this experiment is provided and additional experimental results obtained with particles of different sizes are reported. The measurements are compared with molecular dynamics simulations of particle charging for conditions similar to those of the experiment, with other available experimental data on particle charge in the bulk of gas discharges, and with a simple analytical model accounting for ion-neutral collisions. All the considered evidence indicates that ion-neutral collisions represent a very important factor, which significantly affects (reduces) the particle charge under typical discharge conditions.
authors.affiliation: Max-Planck-Institut für Extraterrestrische Physik, D-85741 Garching, Germany.
authors.forename: S A
authors.initials: SA
authors.lastname: Khrapak
authors.forename: S V
authors.initials: SV
authors.lastname: Ratynskaia
authors.forename: A V
authors.initials: AV
authors.lastname: Zobnin
authors.forename: A D
authors.initials: AD
authors.lastname: Usachev
authors.forename: V V
authors.initials: VV
authors.lastname: Yaroshenko
authors.forename: M H
authors.initials: MH
authors.lastname: Thoma
authors.forename: M
authors.initials: M
authors.lastname: Kretschmer
authors.forename: H
authors.initials: H
authors.lastname: Höfner
authors.forename: G E
authors.initials: GE
authors.lastname: Morfill
authors.forename: O F
authors.initials: OF
authors.lastname: Petrov
authors.forename: V E
authors.initials: VE
authors.lastname: Fortov