Forwand backward electron yield ratio for α-particle induced emission from different materials
TIn this work, the ratio of forward and backward electron yields for emission induced by the isotropic flux of α-particles from zinc was measured. On the basis of the measured values and experimental data obtained in earlier experiments for other materials, a systematization of the electron yield ra...
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irk-123456789-1946502023-11-28T12:54:04Z Forwand backward electron yield ratio for α-particle induced emission from different materials Zhurenko, V.P. Kononenko, S.I. Kalantaryan, O.V. Avotin, S.S. Rokhmanov, N.Ya. Plasma dynamics and plasma-wall interaction TIn this work, the ratio of forward and backward electron yields for emission induced by the isotropic flux of α-particles from zinc was measured. On the basis of the measured values and experimental data obtained in earlier experiments for other materials, a systematization of the electron yield ratio for forward and backward emission was done, and a relationship of the ratio with stopping power of an ion in a substance was found. The dependence of work function for various materials on the ratio of the electron emission yields was analyzed. Виміряно відношення коефіцієнтів емісії електронів на простріл і на відбиття, яка індукована ізотропним потоком α-частинок з цинку. На основі виміряних значень і експериментальних даних, отриманих в попередніх експериментах для інших матеріалів, проведена систематизація відношення коефіцієнтів на простріл і відбиття, і встановлено зв'язок цього параметра з питомими іонізаційними втратами іона в речовині. Проаналізовано залежність роботи виходу електронів для різних матеріалів від відношення коефіцієнтів емісії. Измерено отношение коэффициентов эмиссии электронов на прострел и на отражение, которая индуцирована изотропным потоком α-частиц из цинка. На основе измеренных значений и экспериментальных данных, полученных в более ранних экспериментах для других материалов, проведена систематизация отношения коэффициентов на прострел и отражение, и установлена связь этого параметра с удельными ионизационными потерями иона в веществе. Проанализирована зависимость работы выхода электронов для различных материалов от отношения коэффициентов эмиссии. 2020 Article Forwand backward electron yield ratio for α-particle induced emission from different materials / V.P. Zhurenko, S.I. Kononenko, O.V. Kalantaryan, S.S. Avotin, N.Ya. Rokhmanov // Problems of atomic science and tecnology. — 2020. — № 6. — С. 89-92. — Бібліогр.: 17 назв. — англ. 1562-6016 PACS: 79.20.Rf78 http://dspace.nbuv.gov.ua/handle/123456789/194650 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Plasma dynamics and plasma-wall interaction Plasma dynamics and plasma-wall interaction |
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Plasma dynamics and plasma-wall interaction Plasma dynamics and plasma-wall interaction Zhurenko, V.P. Kononenko, S.I. Kalantaryan, O.V. Avotin, S.S. Rokhmanov, N.Ya. Forwand backward electron yield ratio for α-particle induced emission from different materials Вопросы атомной науки и техники |
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TIn this work, the ratio of forward and backward electron yields for emission induced by the isotropic flux of α-particles from zinc was measured. On the basis of the measured values and experimental data obtained in earlier experiments for other materials, a systematization of the electron yield ratio for forward and backward emission was done, and a relationship of the ratio with stopping power of an ion in a substance was found. The dependence of work function for various materials on the ratio of the electron emission yields was analyzed. |
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Article |
| author |
Zhurenko, V.P. Kononenko, S.I. Kalantaryan, O.V. Avotin, S.S. Rokhmanov, N.Ya. |
| author_facet |
Zhurenko, V.P. Kononenko, S.I. Kalantaryan, O.V. Avotin, S.S. Rokhmanov, N.Ya. |
| author_sort |
Zhurenko, V.P. |
| title |
Forwand backward electron yield ratio for α-particle induced emission from different materials |
| title_short |
Forwand backward electron yield ratio for α-particle induced emission from different materials |
| title_full |
Forwand backward electron yield ratio for α-particle induced emission from different materials |
| title_fullStr |
Forwand backward electron yield ratio for α-particle induced emission from different materials |
| title_full_unstemmed |
Forwand backward electron yield ratio for α-particle induced emission from different materials |
| title_sort |
forwand backward electron yield ratio for α-particle induced emission from different materials |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2020 |
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Plasma dynamics and plasma-wall interaction |
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http://dspace.nbuv.gov.ua/handle/123456789/194650 |
| citation_txt |
Forwand backward electron yield ratio for α-particle induced emission from different materials / V.P. Zhurenko, S.I. Kononenko, O.V. Kalantaryan, S.S. Avotin, N.Ya. Rokhmanov // Problems of atomic science and tecnology. — 2020. — № 6. — С. 89-92. — Бібліогр.: 17 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-07-16T22:03:06Z |
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| fulltext |
ISSN 1562-6016. ВАНТ. 2020. №6(130)
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2020, № 6. Series: Plasma Physics (26), p. 89-92. 89
https://doi.org/10.46813/2020-130-089
FORWAND BACKWARD ELECTRON YIELD RATIO FOR -PARTICLE
INDUCED EMISSION FROM DIFFERENT MATERIALS
V.P. Zhurenko
1
, S.I. Kononenko
1
, O.V. Kalantaryan
1
, S.S. Avotin
2
, N.Ya. Rokhmanov
2
1
V.N. Karazin Kharkiv National University, Kharkiv, Ukraine;
2
Kharkiv National Agrarian University, «Dokuchaieske-2», Kharkiv region, Ukraine
E-mail: v.zhurenko@gmail.com
In this work, the ratio of forward and backward electron yields for emission induced by the isotropic flux of -
particles from zinc was measured. On the basis of the measured values and experimental data obtained in earlier
experiments for other materials, a systematization of the electron yield ratio for forward and backward emission was
done, and a relationship of the ratio with stopping power of an ion in a substance was found. The dependence of
work function for various materials on the ratio of the electron emission yields was analyzed.
PACS: 79.20.Rf78
INTRODUCTION
Energy losses of a fast ion in matter can be
anisotropic, that is associated with the dominant transfer
of energy to electrons, which, as a result of collisions,
move in the direction of the primary incident particle.
Experimentally, this phenomenon can be observed in
the study of secondary electron emission induced by a
flux of fast ions from the front (from the side of
incidence of the beam – backward emission) and rear
(from the side of the beam exit – forward emission)
surfaces of a thin target. The emission research of
Mekback, Brownstein and Arista [1] was the pioneering
work in which attention was drawn to this phenomenon.
Since then, considerable attention has been paid to the
study of the difference between the electron yields for
the forward emission F and for the backward one B,
namely, the ratio R = F/B depending on various
parameters [2-8]. The difference can be explained by
the fact that an electron yield of emission is directly
proportional to the stopping power of the ion in the
substance [9, 10]. In turn, it allows, by studying the
behavior of the R-ratio or R-factor of Mekback, to
obtain information about the energy loss of a moving
ion in a substance and the distribution of this energy
among various groups of electrons [8].
Emission process occurs due to the collisions of the
ion with the atoms of the target material and the
formation of electrons of different velocities. Slow
electrons, produced both by direct collisions with small
transferred momenta, and by ionization of atoms by the
wake potential, move isotropically in matter, while fast
convoy and -electrons move mainly in the direction of
ion motion [11]. Since a significant part of the energy of
a fast ion is transferred to electrons moving in the
direction of motion of the primary particle (convoy and
-electrons), a difference arises in the energy losses of
the particle in the forward and backward directions.
In our earlier works, we experimentally investigated
the ratio R for a number of metals and assumed the
existence of a certain dependence of this parameter on
the stopping power of an ion in a substance [12]. In this
work, we measured the ratio R for zinc in the case of
emission induced by an isotropic flux of fast -particles,
investigated the correlation between the work function
of electrons and the ratio R, and also systematized the
data on the dependence of R on the stopping power of
an ion in the substance.
EXPERIMENTAL SETUP
Forward-backward asymmetry experiment for zinc
was done on the experimental setup described in detail
in [13]. The projectile source (Fig. 1) was radioisotope
with isotope Pu
239
(initial flow intensity 4.64∙10
6
particles per second, energy of -particles is 5.15 MeV,
isotropic flux of projectile radiated into the solid angle
2). -particles passed through the thin aluminum foil
target (thickness 5.6 m) induced forward emission
from deposited zinc layer and backward emission from
the surface of massive zinc collector. Electron yields of
forward F and backward B emissions were calculated
basing on electrometric current measurement. The
experiment was performed at room temperature and
standard vacuum conditions with residual gas pressure
approximately 2∙10
-4
Pa.
Fig. 1. Scheme of forward-backward electron emission
experiments
The target was aluminum foil substrate with
deposited zinc layer (thickness of 0.85 m). Zinc layer
on the substrate surface was formed by thermal vacuum
deposition of pure Zn (99.99 %) in vacuum universal
station «VUP-5M». The residual gas pressure was
approximately 2∙10
-3
Pa.
90 ISSN 1562-6016. ВАНТ. 2020. №6(130)
SRIM SIMULATIONS
We simulated passage of fast alpha-particles through
the target in SRIM/TRIM software [14]. Two cases
were described: normal incidence and passage at angle
of 20°. Initially, an isotropic particle flux falls on the
target. As a result of oblique incidence at different
angles, some of the particles stop in the target, since for
these particles the path length can become equal to the
path length of the ion in the substance. As a result, at the
exit from the target, the particles have an energy
distribution from 0 to Emax, which corresponds to
normally incident ions, and is equal to 3.91 MeV in our
case (calculated by SRIM/TRIM). The energy of ions
impinged at 20° is approximately 3.82 MeV after the
passage of the target.
Figs. 2, 3 shows the calculation of the passage of
ions with energy of 5.15 MeV for normal and oblique
incidence. The ions transmitted through the target with
some scattering, only a small fraction of ions are
backscattered. Energy losses were evaluated by TRIM’s
«Ion stopping and range tables». Electron stopping
power is the main part of the total energy loss of the
projectiles in the zinc layer.
Fig. 2. Ion trajectories in Al-Zn target for normal
incidence
Fig. 3. Ion trajectories in Al-Zn target for oblique
incidence at angle of 20
RESULTS AND DISCUSSIONS
The measurements showed that for zinc forward
emission was higher than backward ones, and R ratio
was equal 1.83, that is in good agreement with previous
results for other materials [8, 12, 13, 15].
As we mentioned above it is considered theoretically
and experimentally confirmed that electron yield of ion-
induced emission is directly proportional to the specific
energy losses (stopping power) of a fast ion in a
substance. This conclusion concerns primarily slow,
true secondary electrons. It is logical to assume that the
Mekbach’s factor also depends on the energy loss of the
ion in a substance. We summarized R data from our
previous experiments [8, 12, 13, 15] and from the paper
[2]. Fig. 4 shows the dependence of R ratio on stopping
power for various materials, which are given in the
series of works [8, 12, 13, 15]. In addition, the figure
shows data for a thin carbon film bombarded by lithium
ions from A. Clouvas’s work [2]. As can be clearly
seen, the hypothesis of the dependence of the Mekbach
factor on stopping power is experimentally confirmed.
As it was found earlier [16], energy distribution
function of electron emission induced by fast ions, had
power-law dependence. Besides, it was shown
experimentally that energy distribution function for
ISSN 1562-6016. ВАНТ. 2020. №6(130) 91
metals had a piecewise-power-law character (two
energy intervals) with various power indices for the
energy interval 0...30 and 30...100 eV. The power index
for slow electrons was significantly higher than for
more energetic electrons (with energies higher than
30 eV).
For slow electrons, the influence of conditions of
their output from the surface (taking into account a
larger power index) will significantly change the value
of total electron yield. Thus, an increase in the work
function value leads to a decrease in the electron yield
(mainly slow electrons) from the material being studied.
This effect occurs both in the case of forward and
backward electron emissions. However, forward and
backward distribution functions differ significantly in
the high-energy part. It is well known that fast electrons
(convoy and delta electrons) contribute mainly to
forward emission [6]. Consequently, an increase in the
work function leads to a relative decrease in the
backward electron yield in comparison with forward
one.
Fig. 5 demonstrates the dependence of R ratio on the
work function of materials that were used as targets in a
series of experiments [8, 12, 13, 15]. The values of work
function were taken from the handbook [17]. The curve
fits well with our assumption about relation between R
and work function.
In addition, it was previously shown that the power
index in the first energy interval increased with growth
of energy losses of the ion in a substance. This leads to
a relative decrease of electron emission from the
collector (backward yield) due to a decrease in the
number of slow electrons, while there is a small high-
energy component (convoy and -electrons) in the
energy distribution of backward emitted electrons. This
tendency of more rapid decrease of backward electron
yield in comparison with forward one also affects the
Mekbach’s ratio. As a result the R ratio increases with
growth of the stopping power (see Fig. 4).
10 15 20 25 30 35 40 45 50
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
Mg
Ni
C
TiN
CuTi
Zn
Al
R
f
a
c
to
r,
a
.
u
.
Stopping power, eV/A
Fig. 4. R ratio as a function of stopping power for
different materials (approximating solid line curve is
shown to guide eye)
3.6 3.8 4.0 4.2 4.4 4.6 4.8 5.0
1.0
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
1.9
Mg
Ni
C
TiN
Cu
Ti
Zn
Al
R
f
a
c
to
r,
a
.
u
.
Work function, eV
Fig. 5. R ratio dependence on work function for
different materials (approximating solid line curve is
shown to guide eye)
CONCLUSIONS
The paper presents the experimental results of zinc
electron emission induced by the flux of -particles
emitted by radioisotope source. The electron yields for
forward and backward emission were measured for the
same energy of -particles. The last fundamentally
distinguished our experiment from other studies, in
which the corresponding electron yields were measured
from both surfaces of a thin, most often, carbon foil
during the passage of a beam of fast ions. Zinc
Mekbach’s ratio calculated basing on forward-backward
measurements was in good agreement with the data
obtained in our previous works for several metals and
the data published by A. Clouvas’s group for the carbon
foil target and lithium ions [2].
We demonstrated that the Mekbach’s ratio for
various substances depended on the stopping power of a
fast ion. The reasons have been discussed in the paper.
In addition, it was shown that work function of a
substance significantly affected the ratio of the forward
and backward electronic yields. This fact was associated
with piecewise power-law energy distribution function
of emission electrons and significantly higher power
index on the first energy interval in comparison with
one for more energetic electrons.
ACKNOWLEDGEMENT
We would like thank to D. L. Ryabchikov for
assistance in sample preparing and Zn layer deposition.
REFERENCES
1. W. Meckbach, G. Braunstein, N. Arista. Secondary-
electron emission in the backward and forward
directions from thin carbon foils traversed by
25...250 keV proton beams // J. Phys. B. 1975, v. 8,
№ 14, p. L344-L349.
2. A. Clouvas et al. Role of projectile electrons in
secondary electron emission from solid surfaces under
fast-ion bombardment // Phys. Rev. B. 1997, v. 55,
p. 12086-12098.
92 ISSN 1562-6016. ВАНТ. 2020. №6(130)
3. H. Rothard et al. Secondary-electron yields from thin
foils: A possible probe for the electronic stopping power
of heavy ions // Phys. Rev. A. 1990, v. 41, p. 2521-2536.
4. H. Rothard. Electron ejection from solids by heavy
ions at high energies (1...100 MeV/u) // Nucl. Instr. and
Meth. B. 1998, v. 146, p. 1-10.
5. H. Rothard, J. Schou, K.O. Groeneveld. Projectile-
and charge-state-dependent electron yields from ion
penetration of solids as a probe of preequilibrium
stopping power // Phys. Rev. A. 1992, v. 45, p. 1701-
1710.
6. H. Rothard et al. Strong projectile-dependent
forward-backward asymmetry of electron ejection by
swift heavy ions in solids // Phys. Rev. A. 1998, v. 57,
p. 3660-3664.
7. T. Kaneko, Y. Mitsunobu. Forward/backward
secondary electron emission from foils by swift ion
impact // Nucl. Instr. and Meth. B. 1994, v. 90, p. 560-
563.
8. V.P. Zhurenko, S.I. Kononenko, V.I. Karas’,
V.I. Muratov. Dissipation of the Energy of a Fast
Charged Particle in a Solid-State Plasma // Plasma
Physics Reports. 2003, v. 29, № 2, p. 130-136.
9. E.J. Sternglass. Theory of secondary electron
emission by high-speed ions // Phys. Rev. 1957, v. 108,
№ 1, p. 1-12.
10. J. Schou. Transport theory for kinetic emission of
secondary electrons from solids // Phys. Rev. B. 1980,
v. 22, p. 2141-2173.
11. D. Hasselkamp et al. Particle Induced Electron
Emission II // Springer Tracts in Modern Physics. 2006,
v. 123.
12. V. Zhurenko et al. -particle induced forward-
backward electron emission from titanium nitride //
Problems of Atomic Science and Technology. Series
«Plasma Physics» (116). 2018, № 4 p. 293-296.
13. V. Zhurenko et al. Secondary electron emission
induced by -particles from Mg-MgO layers //
Problems of Atomic Science and Technology. Series
«Plasma Physics» (122). 2019, № 4, p. 207-210.
14. J.F. Ziegler, J.P. Biersack, U. Littmark. SRIM – The
stopping and range of ions in matter // Nucl. Instrum.
Methods Phys. Res. B. 2010, v. 268, p. 1818-1823.
http://dx. doi.org/10.1016/j.nimb.2010.02.091
15. S.I. Kononenko, V.P. Zhurenko, O.V. Kalantaryan,
A.A. Semerenskiy. Forward and backward electron
emission in binary cell of radioisotope current source //
Problems of Atomic Science and Technology. Series
«Plasma Physics» (9). 2015, № 4, p. 331-334.
16. S.I. Kononenko et al. energy distributions of
electrons in stainless steel bombarded by fast ions //
Journal of Kharkiv University. 2004, v. 619, p. 119-122.
17. H.B. Michaelson. The work function of the elements
and its periodicity // J. Appl. Phys. 1977, v. 48, p. 4729.
doi: 10.1063/1.323539.
Article received 10.10.2020
ОТНОШЕНИЕ КОЭФФИЦИЕНТОВ ВЫХОДА ЭЛЕКТРОНОВ НА ПРОСТРЕЛ И НА ОТРАЖЕНИЕ
ДЛЯ ИНДУЦИРОВАННОЙ -ЧАСТИЦАМИ ЭМИССИИ ИЗ РАЗЛИЧНЫХ МАТЕРИАЛОВ
В.П. Журенко, С.И. Кононенко, O.В. Калантарьян, С.С. Авотин, Н.Я. Рохманов
Измерено отношение коэффициентов эмиссии электронов на прострел и на отражение, которая
индуцирована изотропным потоком -частиц из цинка. На основе измеренных значений и
экспериментальных данных, полученных в более ранних экспериментах для других материалов, проведена
систематизация отношения коэффициентов на прострел и отражение, и установлена связь этого параметра с
удельными ионизационными потерями иона в веществе. Проанализирована зависимость работы выхода
электронов для различных материалов от отношения коэффициентов эмиссии.
ВІДНОШЕННЯ КОЕФІЦІЄНТІВ ВИХОДУ ЕЛЕКТРОНІВ НА ПРОСТРІЛ І НА ВІДБИТТЯ
ДЛЯ ІНДУКОВАНОЇ -ЧАСТИНКАМИ ЕМІСІЇ З РІЗНИХ МАТЕРІАЛІВ
В.П. Журенко, С.І. Кононенко, O.В. Калантар’ян, С.С. Авотін, М.Я. Рохманов
Виміряно відношення коефіцієнтів емісії електронів на простріл і на відбиття, яка індукована ізотропним
потоком -частинок з цинку. На основі виміряних значень і експериментальних даних, отриманих в
попередніх експериментах для інших матеріалів, проведена систематизація відношення коефіцієнтів на
простріл і відбиття, і встановлено зв'язок цього параметра з питомими іонізаційними втратами іона в
речовині. Проаналізовано залежність роботи виходу електронів для різних матеріалів від відношення
коефіцієнтів емісії.
http://dx/
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