Plasma Oscillations and Expansion of an Ultracold Neutral Plasma
S Kulin, T C. Killian, S D. Bergeson, S L. Rolston
We report the observation of plasma oscillations in an ultracold neutral plasma. Using this collective mode, we probe the electron density distribution and study the expansion of the plasma as a function of time. For classical plasma conditions, i.e. weak Coulomb coupling, the expansion is dominated by the pressure of the electron gas and is described by a hydrodynamic model. Discrepancies between the model and observations at low temperature and high density may be due to strong coupling of the electrons.