The particles are cooled by the neutral gas. A comparable temperature was measured by Boufendi et al. We estimate the plasma parameters and the grain charge in the following way. When the rf power was raised, however, we found that particles moved more violently, and many appeared to have no equilibrium positions, so the cloud qualitatively appeared to be liquid-like. However, we did not observe a distinct phase transition of the cloud as a whole.
Positive ions flowing toward the lower electrode exert the ion drag force.
Measurements showed that the electrode temperature was not elevated above the surroundings. In addition to these forces, there are inter-particle electrostatic forces, which are responsible for the internal structure of the cloud, including the crystalline structure. Image analysis reveals the crystalline structure, which is consistent with a large value of the Coulomb coupling parameter. J. E. Daugherty et al., J. Appl. FIG.1 Schematic of apparatus.