Charge fluctuations and their influence on dust cluster oscillation modes

Summary form only given. Formation of ordered dust crystals is one of the most general and fundamental phenomenon in complex dusty plasmas. Dust crystals with a small number of particles are called dust clusters or Coulomb clusters. Two-dimensional (2D) dust particle clusters provide useful model systems for the study of properties of dust structures in complex plasmas. Such clusters consist of a small number of micron-sized particles trapped in the sheath of a discharge plasma. The ground state and metastable structure of 2D dust particle clusters, their dynamical properties, and phase transitions was extensively studied theoretically. A lot of attention was paid to oscillation modes in such clusters. The spectral power density of the modes was measured for dust clusters and several modes were compared such as the breathing mode and intershell rotation as well as the lowest- and highest-frequency modes. It is known that one of the most basic configurations are with N=3, N=7(l,6) and N=12(3,9) particles in the cluster. We report here results of numerical modeling of the cluster mode spectra. We pay particular attention for the influence of the nature (correlated vs uncorrelated character) of the charge fluctuations on the mode spectra of small clusters containing N = 3, N = 7, and N= 12 particles. We demonstrate that one of the main effects related to the charge fluctuations, a splitting of the spectrum lines, reveals different patterns depending on the nature of the fluctuations. The modes most and least affected to the character of the charge fluctuations are analyzed and comparison with experimental spectra is performed. The analysis of the influence of the charge fluctuations on the normal mode spectra of dust clusters demonstrates the mode splitting related with the nature and the variance of the fluctuations.