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47Complex Systems of Charged Particles and their Interactions with Electromagnetic Radiation 2016
APPROXIMATION OF THE ION DRIFT VELOCITY IN PARENT GAS
R.I.Golyatina, S.A. Maiorov I.I.
A.M. Prokhorov General Physics Institute, Moscow, Russia, E-mail: mayorov_sa@mail.ru
In work we carried out calculations characteristics drift of ions in the gas, helium, neon, argon, krypton, xenon, and cesium, rubidium and mercury at gas temperatures 4.2, 77, 300, 1000, 2000 K, and a wide range of reduced electric field strength - from 1 to 10000 Td [1 - 3]. For the calculation ion-atom collisions model was used, it was implemented by the Monte Carlo method [1]. Numerous experimental data show that the drift velocity of the ions in their own gas is very well described by the semi-empirical formula Frost [2, 3]:
f i bE V1/2 E (1)
u = al 1 + b— I —. (1)
t N) N
This dependence of the drift velocity of the reduced electric field E / N has two parameters: a - the mobility in the weak field limit and b = 1/(E /N)heating . The value
(E / N)heating - this is the value of the reduced electric field strength, which due to the heating of
the ions according to the formula Frost mobility decreases in the root of two times. Parameters of the approximation in the formula (1) were identified based on the analysis of the calculations of the kinetic characteristics for different gas temperatures:
a = Kpol x (NJ N)/ (1 + Tat0m / £0 )1/2. (2)
Here s0 - adjustable parameter, Taoom and N - temperature and density of the atoms, Kpol = 13.853(ad/) 1/2 - polarization mobility in units cm2 / (V s) at a standard density of the gas N0 = 2.686763 x 1019 atoms in cm3 (number Loschmidt), ad - polarizability in cubic Angstroms, / - reduced mass in grams per mole [5]. 1/ b = (E / N)0 (1 +1.5Taoom / s0).
In the Table for different gases are given the values of polarization mobility Kpol, parameters s0 and (E / N)0 - a
value of a warming field at zero temperature gas. As the analysis of calculated data, parameter (E / N)0 is not independent, and can be determined by the formula (E / N)0 = (2ms0)1/2 / KpolN0. This formula is derived
from the relation < s >pol = s0 , which is performed with an accuracy of about 1%, here
<s> o = 2 m [1.5 (E / N )0 KpoA)2.
This work was supported by RFBR-14-02-00502-a grant. References
[1]. S.A. Maiorov, Plasma Physics Reports, 2009, 35, No. 9, 802.
[2]. R.I. Golyatina, S.A. Maiorov, Bulletin of the Lebedev Physics Institute, 2015, 42, No 10, 294.
[3]. R.I. Golyatina, S.A. Maiorov, Plasma Physics Reports, 2016, 42.
Kpol £0 - (E/N)o,
System cm2/c b K Td
He+ in He 21.6 90 16
Ne+ in Ne 6.8 210 34
Ar+ in Ar 2.42 240 73
Kr+ in Kr 1.36 330 106
Xe+ in Xe 0.85 270 122
Hg+ in Hg 0.61 58 63
