  Micron-size charged particles can be easily levitated in low-density plasma
environments. At low pressures, suspended particles have been observed to
spontaneously oscillate around an equilibrium position. In systems of many
particles, these oscillations can catalyze a variety of nonequilibrium,
collective behaviors. Here, we report spontaneous oscillations of single
particles that remain stable for minutes with striking regularity in amplitude
and frequency. The oscillation amplitude can also exceed 1 cm, nearly an order
of magnitude larger than previously observed. Using an integrated experimental
and numerical approach, we show how the motion of an individual particle can be
used to extract the electrostatic force and equilibrium charge variation in the
plasma sheath. Additionally, using a delayed-charging model, we are able to
accurately capture the nonlinear dynamics of the particle motion, and estimate
the particle's equilibrium charging time in the plasma environment.
