J. Phys. IV France 10 (2000) Pr5-493-Pr5-496
Atomic excitation in strongly coupled plasmasH. Kitamura1, 2, 3, M.S. Murillo1 and J.C. Weisheit1, 3
1 Applied Physics Division, Los Alamos National Laboratory, Los Alamos, NM 87545, U.S.A.
2 Institute for Solid State Physics, University of Tokyo, Roppongi, Tokyo 106-8666, Japan
3 Space Physics and Astronomy Department, Rice University, Houston, TX 77005, U.S.A.
In dense plasmas atomic excitation rates arising from scattering between atoms and surrounding plasma particles are formulated on the basis of the equations of motion for density matrices in a stochastic potential. This model enables us to treat strong transitions for which the first-order perturbation theory does not apply. Within a decorrelation approximation, which enables one to break up the higher-order correlation functions of plasma density fluctuations into the products of binary correlation functions (i.e., dynamic structure factors), the interaction is effectively summed to infinite order. This method is applied to two-level atoms in hydrogen plasmas. It is thereby demonstrated that when the plasma density is sufficiently high, low-frequency ion-density fluctuations may cause coherent atomic excitation between close lying states. Such coherent excitation cannot be described by the conventional collisional rate equations based on the first-order perturbation theory.
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