Heating and expansion of radio frequency driven ultracold plasmas

Ronghua Lu, Shensheng Han

Kevin A. Twedt, S. L. Rolston

John Guthrie, Puchang Jiang, Jacob Roberts

Peter W. Smorenburg, L. P. J. Kamp, O.J. Luiten

Several mechanisms by which an external electromagnetic field influences the temperature of a plasma are studied analytically and specialized to the system of an ultracold plasma (UCP) driven by a uniform radio-frequency (rf) field. Heating through collisional absorption is reviewed and applied to UCPs. Furthermore, it is shown that the rf field modifies the three-body recombination process by ionizing electrons from intermediate high-lying Rydberg states and upshifting the continuum threshold, resulting in a suppression of three-body recombination. Heating through collisionless absorption associated with the finite plasma size is calculated in detail, revealing a temperature threshold below which collisionless absorption is ineffective.

James D. Hanson, F. Robicheaux

Sergey Ya. Bronin, Evgenii Vladimirovich Vikhrov, Sergey A. Saakyan +2 more

Calculations of the spectrum of eigen oscillations of an inhomogeneous ultracold plasma are presented both in the absence and in the presence of charge imbalance. The collective modes of these plasma oscillations are recorded in experiments as absorption resonances of a radio frequency electric field. It is shown that in the presence of friction of the electronic component, a discrete spectrum of plasma eigen oscillations is formed. The dependence of the frequency of these resonances on the plasma expansion time in the presence of a charge imbalance is obtained. There is good agreement with the experiments of different authors.