Anomalous electron density behaviour in dusty plasma afterglow

The anomalous increasing of electron density in RF discharge plasma with strong dust contamination after discharge switching-off was observed in experiment (J. Berndt et al, Plasma Sources Sci. Technol., 2006, {\bf 15}, 18). A possible mechanism of this is the discharging of negatively charged dust particles in afterglow plasma. The existing theoretical models of dust discharging due to ion flux show that it is not efficient to provide the observed electron density growth. In this work, it is assumed that the more fast mechanism of dust discharging is electrons desorption from dust surface. The afterglow of heavy dusted plasma in argon was simulated by PIC-MCC method, including electrons desorption from dust and metastable argon atoms kinetics. The analysis of the electron energy distribution function shows, that the fast electrons rapidly depart from the plasma volume, thus leading to dust surface potential magnitude and hence the dust charge drop. As a result, the electrons are released from dust particles, providing the anomalous electron density increasing. The metastable pooling ionization enlarges the electron density and temperature, but cannot provide the anomalous peak of electron density.