INTRODUCTION
It is well known that the electron loss and capture
that occurs when fastmoving ions pass through a sub
stance alter the charge fraction value in an ion beam,
and in establishing charge equilibrium when a thick
target is involved [1]. In this case, the average equilib
rium charge, the value of which does not depend
on the initial charge of the incident ion, i0, is a conve
nient parameter for describing the stopping process.
There are many semiempirical equations that
allow us to calculate the average equilibrium charges
for ions with different values of the ion nucleus charge,
Z, the target’s nucleus charge, Zt
, and the ion’s veloc
ity, V [2, 3]. In recent years, however, there has been
increasing interest in the processes of ion stopping
inside thin films. Incident ions, in passing such films,
do not have enough time to reach charge equilibrium;
the energy losses then depend to a great extent on the
initial state of the incident ion when passing through
the first atomic layers several hundreds of nanometers
thick [4].
More detailed research into the preequilibrium
charge distributions of ions is thus becoming ever more
vital. Organic films as targets are of special interest,
since light ions are more widely used in ion therapy. At
present, however, there have only been scattered stud
ies on the nonequilibrium processes that occur when
light ions, Z ≤ 10, pass mainly through thin carbon
films [5].
In this work, the authors consider on the basis of
experimental data [6–8] some methods for computing
the average charge that forms when helium (He) and
nitrogen (N) ions with different initial charges pass
through celluloid films at various velocities.
, eq i