Monthly Archives: March 2015

Fluid approach to evaluate sound velocity in Yukawa systems (complex plasmas). (arXiv:1503.00560v1 [physics.plasm-ph])

The conventional fluid description of multi-component plasma, supplemented by an appropriate equation of state for the macroparticle component, is used to evaluate the longitudinal sound velocity of Yukawa fluids. The obtained results are in very good agreement with those obtained earlier employing the quasi-localized charge approximation and molecular dynamics simulations in a rather broad parameter regime. Thus, a simple yet accurate tool to estimate the sound velocity across coupling regimes is proposed, which can be particularly helpful in estimating the dust-acoustic velocity in strongly coupled dusty (complex) plasmas. It is shown that, within the present approach, the sound velocity is completely determined by particle-particle correlations and the neutralizing medium (plasma), apart from providing screening of the Coulomb interaction, has no other effect on the sound propagation. The ratio of the actual sound velocity to its "ideal gas" (weak coupling) scale only weakly depends on the coupling strength in the fluid regime, but exhibits a pronounced decrease with the increase of the screening strength. The limitations of the present approach in applications to real complex plasmas are briefly discussed.

Using higher ionization states to increase Coulomb coupling in an ultracold neutral plasma

Author(s): M. Lyon, S. D. Bergeson, A. Diaw, and M. S. Murillo

We report measurements and simulations of the time-evolving rms velocity distribution in an ultracold neutral plasma. A strongly coupled ultracold neutral Ca+ plasma is generated by photoionizing laser-cooled atoms close to threshold. A fraction of these ions is then promoted to the second ionizatio...

[Phys. Rev. E 91, 033101] Published Mon Mar 02, 2015

Relativistic symmetries of a multiparameter exponential-type potential within Coulomb-like and Yukawa-like tensor interactions

Abstract In this paper, we study the Dirac equation with a multiparameter exponential-type potential including two tensor interactions. We obtain the energy eigenvalues by using the Nikiforov-Uvarov method. The corresponding wave functions are obtained and expressed in terms of hypergeometric functions. The effects of the Coulomb and the Yukawa tensor interactions are also investigated numerically and discussed in detail.