Environmental Engineering Reference
In-Depth Information
electron temperature
T
e
10
4
K [13, 15-17] corresponds to that of the solar wind.
In this manner other types of dusty plasma are formed in the solar system [18-22].
In particular, interaction of the solar wind, a flux of plasma emitted by the Sun's
corona [12, 13], with dust from the rings of Jupiter and Saturn leads to formation
of a specific dusty plasma [23-26]. A similar type of dusty plasma corresponds to
comet tails [27, 28], and the properties of this plasma are determined by interaction
of comet dust with the solar wind [29]. A laboratory dusty plasma is formed in a
trap, usually near the cathode of radio-frequency discharge or inside striations of
glow discharge. A strong impetus for study of the laboratory dusty plasma was the
discovery of ordered structures formed by particles of identical size in a trap [30-
33]. This fact testifies to the self-consistency of a dusty plasma as a physical system.
This allowed the laboratory dusty plasma to be considered as a specific physical
object [34-38]. A detailed study of the laboratory dusty plasma paves the way for
applications of this plasma [4, 39].
A cluster plasma is an ionized gas containing nanosized clusters [40-42]. This
plasma differs from a dusty plasma not only by particle sizes, but also by the pro-
cesses which occur this system. Indeed, clusters may grow or evaporate in a cluster
plasma, that is, the nucleation and evaporation processes are of importance for a
cluster plasma. Below we will be guided by a cluster plasma consisting of a buffer
gas (e.g., argon) and a metal vapor with a low concentration of metal atoms. This
plasma may be used for transport of heatproof metals and as a light source. We
consider below some aspects of complex plasmas.
We mostly consider the behavior of an individual nanocluster or microparticle
in ionized gas. We use the liquid drop model for a cluster [43] to identify it as a
spherical liquid drop that is cut out from a bulk system. Within the framework of
this model, the principal property of a cluster as a physical object due to magic
numbers [44-51] is lost, so nanoclusters and microparticles become identical. This
model corresponds to averaging a cluster property under consideration of nearby
sizes, which simplifies the analysis a certain cluster property. Therefore, we consid-
er now the behavior of individual clusters or particles in a gas. In this context, the
behavior of a probe in an ionized gas [52-56] and satellites in the atmosphere [57]
has an analogy with the properties of individual nanoclusters and microparticles.
6.1.2
Transport Parameters of Clusters
In considering transport phenomena involving large clusters, it is convenient to
use for a cluster the liquid drop model, according to which the cluster is cut out of
a bulk system and has spherical shape. Then the number densities of atoms in the
cluster and the bulk liquid are identical, and the number of cluster atoms
n
and the
cluster radius
r
0
are connected by (2.16),
n
(
r
0
/
r
W
)
3
,where
r
W
is the Wigner-
Seitz radius [58, 59], which is given by (2.17) and its values are represented in
Table2.2.Forlargeclusters
r
0
D
a
0
,where
a
0
is a typical atomic size, the diffusion
cross section of atom-cluster collisions is given by (2.18),
r
0
.Wehavetwo
limiting cases for cluster transport in a gas depending on the relation between the
σ
D
π
