Abstract
The purpose of this work is to describe the diffusion process of
heavy ions in a light gas in presence of an external
electromagnetic field, by assuming a constant magnetic field
pointing along an arbitrary direction $B=(B_x,B_y,B_z)$ and
a general time-varying electric field $E(t)$. This process
will be described through the Fokker-Planck (FP) equation
associated with the corresponding Langevin equation. The exact
solution of the FP equation can be found, by means of a
transformation, through a time-dependent rotation matrix, of the
associated Lagevin equation, which renders quite similar to that
of the ordinary Brownian motion under the action of an external
force. In this sense, the solution of the FP equation in the
transformed velocity-space comes out immediately. We also use the
same initial heavy-ion velocity Maxwellian distribution at
temperature different from that of equilibrium, and around the
mean velocity $u\rangle_0$, proposed by Ferrari
Physica A 163, 596 (1990), to calculate a more general
probability density.
PACS numbers: 05.40.-a, 02.50.-r
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