Negative mobilities of electrons in radio frequency fields

In this paper, we perform calculations of mobilities (represented by drift velocities) of electrons in mixtures of F₂ and Ar in radio frequency (RF) fields. The conditions were chosen which correspond to those that led to observation of negative absolute mobility in dc fields in decaying plasmas. In RF fields, a similar effect is observed as the mobility corresponding to the flux drift velocity is negative. At the same time, it was found that the mobility corresponding to the bulk drift velocity is mainly positive in respect to the expected value, but that it has a large phase delay. The effect is caused by nonconservative nature of the attachment and in the absence of nonconservative collisions both mobilities are positive and in phase with the field.