Excitation of isomeric low-lying level of nucleus ¹⁸¹Ta by relativistic electrons
Influence on efficiency of exciting of the E1-level ¹⁸¹Ta with energy 6.24 keV of neutron-capture reaction and photonuclear processes by means of the processes caused by passage of powerful electron beam through tantalum is studied. Strengthening of reaction yield ¹⁸¹Ta(γ,2n)¹⁷⁹Ta and neutron-captur...
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| Zitieren: | Excitation of isomeric low-lying level of nucleus ¹⁸¹Ta by relativistic electrons / N.P. Dikiy, A.N. Dovbnya, Yu.V. Lyashko, V.I. Nikiforov, V.L. Uvarov, I.D. Fedorets // Вопросы атомной науки и техники. — 2013. — № 3. — С. 175-178. — Бібліогр.: 19 назв. — англ. |
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irk-123456789-1118512017-01-16T03:02:35Z Excitation of isomeric low-lying level of nucleus ¹⁸¹Ta by relativistic electrons Dikiy, N.P. Dovbnya, A.N. Lyashko, Yu.V. Nikiforov, V.I. Uvarov, V.L. Fedorets, I.D. Ядерная физика и элементарные частицы Influence on efficiency of exciting of the E1-level ¹⁸¹Ta with energy 6.24 keV of neutron-capture reaction and photonuclear processes by means of the processes caused by passage of powerful electron beam through tantalum is studied. Strengthening of reaction yield ¹⁸¹Ta(γ,2n)¹⁷⁹Ta and neutron-capture reaction ¹⁸¹Ta(n,γ)¹⁸²Ta by means of high intensity of high-energy electrons are discovered. Розглянуто вплив процесiв, обумовлених проходженням потужнострумового пучка електронiв через тантал, на швидкiсть заселення Е1-рiвня ¹⁸¹Ta з енергiєю 6,24 кeВ, на радiацiйне захоплення нейтронiв i фотоядернi процеси. Виявлено посилення фотоядерної реакцiї ¹⁸¹Ta(γ,2n)¹⁷⁹Ta i реакцiї радiацiйного захоплення нейтронiв ¹⁸¹Ta(n,γ)¹⁸²Ta при високiй iнтенсивностi високоенергетичних електронiв. Рассмотрено влияние процессов, обусловленных прохождением сильноточного пучка электронов через тантал, на скорость заселения E1-уровня ¹⁸¹Ta с энергией 6,24 кэВ, на радиационный захват нейтронов и фотоядерные процессы. Обнаружено усиление фотоядерной реакции ¹⁸¹Ta(γ,2n)179Ta и реакции радиационного захвата нейтронов ¹⁸¹Ta(n,γ)¹⁸²Ta при высокой интенсивности высоко энергетических электронов. 2013 Article Excitation of isomeric low-lying level of nucleus ¹⁸¹Ta by relativistic electrons / N.P. Dikiy, A.N. Dovbnya, Yu.V. Lyashko, V.I. Nikiforov, V.L. Uvarov, I.D. Fedorets // Вопросы атомной науки и техники. — 2013. — № 3. — С. 175-178. — Бібліогр.: 19 назв. — англ. 1562-6016 PACS: 34.80.Pa; 41.60.-m; 61.85.+p http://dspace.nbuv.gov.ua/handle/123456789/111851 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Ядерная физика и элементарные частицы Ядерная физика и элементарные частицы |
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Ядерная физика и элементарные частицы Ядерная физика и элементарные частицы Dikiy, N.P. Dovbnya, A.N. Lyashko, Yu.V. Nikiforov, V.I. Uvarov, V.L. Fedorets, I.D. Excitation of isomeric low-lying level of nucleus ¹⁸¹Ta by relativistic electrons Вопросы атомной науки и техники |
| description |
Influence on efficiency of exciting of the E1-level ¹⁸¹Ta with energy 6.24 keV of neutron-capture reaction and photonuclear processes by means of the processes caused by passage of powerful electron beam through tantalum is studied. Strengthening of reaction yield ¹⁸¹Ta(γ,2n)¹⁷⁹Ta and neutron-capture reaction ¹⁸¹Ta(n,γ)¹⁸²Ta by means of high intensity of high-energy electrons are discovered. |
| format |
Article |
| author |
Dikiy, N.P. Dovbnya, A.N. Lyashko, Yu.V. Nikiforov, V.I. Uvarov, V.L. Fedorets, I.D. |
| author_facet |
Dikiy, N.P. Dovbnya, A.N. Lyashko, Yu.V. Nikiforov, V.I. Uvarov, V.L. Fedorets, I.D. |
| author_sort |
Dikiy, N.P. |
| title |
Excitation of isomeric low-lying level of nucleus ¹⁸¹Ta by relativistic electrons |
| title_short |
Excitation of isomeric low-lying level of nucleus ¹⁸¹Ta by relativistic electrons |
| title_full |
Excitation of isomeric low-lying level of nucleus ¹⁸¹Ta by relativistic electrons |
| title_fullStr |
Excitation of isomeric low-lying level of nucleus ¹⁸¹Ta by relativistic electrons |
| title_full_unstemmed |
Excitation of isomeric low-lying level of nucleus ¹⁸¹Ta by relativistic electrons |
| title_sort |
excitation of isomeric low-lying level of nucleus ¹⁸¹ta by relativistic electrons |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| publishDate |
2013 |
| topic_facet |
Ядерная физика и элементарные частицы |
| url |
http://dspace.nbuv.gov.ua/handle/123456789/111851 |
| citation_txt |
Excitation of isomeric low-lying level of nucleus ¹⁸¹Ta by relativistic electrons / N.P. Dikiy, A.N. Dovbnya, Yu.V. Lyashko, V.I. Nikiforov, V.L. Uvarov, I.D. Fedorets // Вопросы атомной науки и техники. — 2013. — № 3. — С. 175-178. — Бібліогр.: 19 назв. — англ. |
| series |
Вопросы атомной науки и техники |
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2025-07-08T02:48:09Z |
| last_indexed |
2025-07-08T02:48:09Z |
| _version_ |
1837045267958857728 |
| fulltext |
EXCITATION OF ISOMERIC LOW-LYING LEVEL OF
NUCLEUS 181Ta BY RELATIVISTIC ELECTRONS
N.P. Dikiy1∗, A.N. Dovbnya1, Yu.V. Lyashko1,
V.I. Nikiforov1, V.L. Uvarov1, I.D. Fedorets2
1National Science Center ”Kharkov Institute of Physics and Technology”, 61108, Kharkov, Ukraine
2V.N. Karazin Kharkov National University, 61077, Kharkov, Ukraine
(Received January 31, 2013)
Influence on efficiency of exciting of the E1-level 181Ta with energy 6.24 keV of neutron-capture reaction and pho-
tonuclear processes by means of the processes caused by passage of powerful electron beam through tantalum is
studied. Strengthening of reaction yield 181Ta(γ,2n)179Ta and neutron-capture reaction 181Ta(n,γ)182Ta by means of
high intensity of high-energy electrons are discovered.
PACS: 34.80.Pa; 41.60.-m; 61.85.+p
1. INTRODUCTION
Radiation and absorption by the charged particles
in various structures intensively is investigated. This
is caused by huge influence of such processes on the
most different areas of natural sciences, technics, vi-
tal functions of the person. A striking illustration of
the influence of the processes of radiation generation
is the creation and use of free-electron lasers. Radi-
ation processes can be both spontaneous and forced,
which are caused by an intense external field.
The first indications of the role of spontaneous
and induced processes were examined sufficiently long
ago [1]. However investigation of such processes con-
tinued intensively and in present time [see eg. 2,3].
Also a theory of passage of charged particles in mat-
ter is developing intensively [4-7]. The radiating
processes are observed in large spatial areas in the
case of passage of high-energy radiation through sub-
stance. Consequently, the environment has a sig-
nificant effect on electromagnetic phenomena. It is
necessary to mention about of wake potential of the
charged particles which causes slowly fading fluctua-
tions wake charge density [5], the virtual excitation of
atomic electrons by accelerated particles, which pro-
duce a dynamic polarization of the target [8], etc. It
should be noted the effect of the crystal lattice on the
generation of electromagnetic radiation [9].
The above-mentioned processes can lead to exci-
tation of nuclear states with low energy, which in turn
can be used to create X-ray lasers.
2. MATERIALS AND METHODS
Tantalum target of 1 mm thickness were irradi-
ated by an electron linear accelerator KUT-20 (”Ac-
celerator” Science and Research Establishment of
NSC KIPT). Experimental setup is shown in Fig. 1.
The distance between the targets chosen 1 mm.
The electron energy was 36 MeV, average current
9.5 µA. Duration electron bunches irradiation has
made about 16 ps, the peak intensity - 9.44 A. The
diameter of the electron beam on the first target was
4.6mm.
Fig.1. The scheme of experiment
The activity of 179,182Ta was measured by means
of detector based on high-purity germanium and
Ge(Li)-detector with an energy resolution on line
137Cs 661.6 keV 1.25 keV and 3.2 keV on line
1333 keV, respectively.
3. RESULTS AND DISCUSSION
The reaction yield 181Ta(γ,2n)179Ta and
181Ta(n,γ)182Ta for the incoming and outgoing beam
of tantalum plates is shown in Fig. 2. The reaction
yield 181Ta(γ,2n)179Ta and 181Ta(n,γ)182Ta for the
incoming and outgoing beam which calculated by
PENELOPE-2008 is shown in Fig. 3,4.
∗Corresponding author E-mail address: ndikiy@kipt.kharkov.ua
ISSN 1562-6016. PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2013, N3(85).
Series: Nuclear Physics Investigations (60), p.175-178.
175
Feature of these dependences of reaction yield are
increase their value at the transition from one to the
other plate. Theoretical calculations show as rule op-
posite results. Probably the increase of yield of reac-
tion 181Ta(γ,2n)179Ta and 181Ta(n,γ)182Ta is caused
by excitation of the lower level of the tantalum-181
with an energy of 6.24 keV. Its parameters are listed
in Table.
The parameters of the lower level of the nucleus
181Ta
polarity transition energy, keV Γc, eV
E1 6.24 7.6 10−11
T1/2, µs basic state excited state
6.05 7/2+ 9/2−
Fig.2. Relative change of intensity of lines 179Ta
from effective depth for Ta samples (above).
Relative change of intensity of lines 182Ta from
effective depth for Ta samples (below)
Among processes which can cause high excitation
efficiency of state of tantalum 6.24 keV it is possible
to note the following.
Scattering of Meller. For small recoil energy of
electron (∆ << γ-1) it is expressed by the equation
[10]:
dσ =
4πe4
mv2
d∆
∆2
, (1)
where ∆ - the energy of the recoil electron, e - electron
charge, v, m - the velocity and mass of the incident
electron. For the recoil energy of electron 6.32 keV
cross section of formation of low-energy electrons can
be several kilobarn.
Fig.3. The calculated yield of reaction
181Ta(γ,2n)179Ta for an entering and leaving bunch
from a layer thickness 3 microns
Fig.4. The calculated yield of reaction
181Ta(γ,2n)179Ta for an entering and leaving bunch
from a layer thickness 226 microns
Emission of soft photons in collisions of ultrarel-
ativistic electrons with the nucleus. In this case the
cross section is:
dσ$ =
16
3
Z2αr2
e
dω
ω
ln
ε2
mω
, (2)
where Z - charge of the nucleus, re - radius of the elec-
tron, α - the fine structure constant, ω - frequency of
soft photons, ε - the energy of the incident electrons
[11]. Cross sections for gamma rays at forward angles
(up to 5◦) may be tens of barns.
The distance between the electrons in a bunch is
about 1.7 microns. Naturally a coherent radiation
with wavelengths much larger than 1.7 microns can
be. As shown in [2] at the passage of electrons of a
176
bunch there is possibility of modulation of its density
and the formation of one or more of the quasi - com-
pact electron bunches. This can result in radiation
of wavelength smaller than in the original size of the
bunch.
A possible explanation the generation of electro-
magnetic radiation may be caused by mechanism
which is presented in [3]. The presence of periodic
inhomogeneity, and wake potential of slowly decay-
ing collective oscillations of the electron density in
the electron bunch which passes in textured tantalum
may excite radiation with frequencies that correspond
to the high numbers of harmonics, ie, maximum of
the emission spectrum can correspond frequencies,
which are much superior to the natural frequencies
of the oscillators [3].
It is known that the resonant interaction of
gamma rays or particles with nuclei in the crystal
lattice, which lead to excited state (compound nu-
cleus) has a collective character [12,13]. In this case,
if the state of the lattice is not changed, the Coulomb
excitation and subsequent gamma decay will be of a
coherent character. For multipolarity E1 and M1 at
grazing collisions of charged particles with the lat-
tice atoms becomes possible manifestations of coher-
ent processes in the Coulomb excitation in a crystal.
Gamma rays are emitted from the cones with the
axis along the beam direction. To obtain a signifi-
cant effect of coherent excitation is necessary to use
extremely low-lying levels of the isomer type and use
beams fast enough particles so that the momentum
transfer p - p
′
(p, p
′
- the initial and final momen-
tum of the incident particle) is not very different from
the wave vector gamma quanta [12-14]. Note that
the coherent excitation of the medium of the moving
particle, leading to a coherent electron loss was ob-
served by surface scattering of helium ions by crystal
tungsten [15]. It is known that rolled tantalum has
a high degree of texture in the {100}. This can lead
to coherent excitation of 6.24 keV level of tantalum,
which is due to the influence of the crystal struc-
ture. Note that for the period of oscillation of the
electrons channeling particles with transverse energy
Eo = Uo (Uo - the maximum value of the transverse
energy of the particle) can be much greater than for
positrons (semichanneling particles). Therefore, for
some of the electrons passing tantalum plate, can be
realized undulator radiation with sufficiently low en-
ergy (6...10 keV energy range). Accordingly, it can
cause stimulated emission level of 6.24 keV tantalum-
181 high-gain due to its high population inversion.
We know that in the low-frequency spectral-angular
density of the radiation intensity is almost indepen-
dent of frequency [9,16].
It is known that the lifetime of the state 6.24 keV
of tantalum-181 in the high-temperature laser plasma
is greater than the lifetime of a given level in the neu-
tral atom [17]. The authors of [17] suggest that this
may be due to the decrease in the probability of in-
ternal electron conversion due to the ionization of the
upper atomic shells up to M-shell inclusive. It is pos-
sible that the lifetime of the excited state 6.24 keV of
the tantalum-181 depended by elastic deformations
in the crystal tantalum when a beam of electrons
passes [18]. It is known that inhibition of gamma-
resonance self-absorption of iron-57 observed at high
power ultrasound [19]. Therefore, the generation of
ultrasonic waves in plates of tantalum can lead to
high levels of occupancy 6.24 keV 181Ta and thus lead
to increased nuclear reaction yield 181Ta(γ,2n)179Ta
and 181Ta(n,γ)182Ta. The main feature of the man-
ifestation of the effect of excitation level of 6.24 keV
due to higher yield of reactions 181Ta(γ,2n)179Ta
and 181Ta(n,γ)182Ta in the transition from one plate
to the other. For example, for L-line calculation
gives a decrease in the intensity of the reaction yield
181Ta(γ,2n)179Ta at the transition from one to the
other of plate, but the experimental data is shows an
increase in the yield of the reaction.
In Fig. 5 shows the calculated yield of
181Ta(n,γ)182Ta tantalum plates are caused by neu-
trons which have arisen in a given plate, in the as-
sumption that the neutron yield in each plate is
uniform. Influence of each plate on others is de-
scribed by the equations of a flat source. It was
assumed that the yield (n,γ)-reaction is due mainly
resonance neutrons. You can see that the ratio of the
yield of reaction 181Ta(n,γ)182Ta/181Ta(γ,2n)179Ta
significantly greater for the first tantalum plate.
Fig.5. The calculated ratio of activity 182Ta/179Ta
for plates of tantalum
4. CONCLUSIONS
1. The main feature of the manifestation of
the effect of excitation level of 6.24 keV is due
to higher yield of reactions 181Ta(γ,2n)179Ta and
181Ta(n,γ)182Ta in the transition from one plate to
the other. At the same time, the calculation for the
L-lines shows reduction in the intensity of the reac-
tion yield 181Ta(γ,2n)179Ta in the transition from one
plate to the other, but for the experimental data ob-
served increase in the yield of the reaction.
2. Found a higher yield of ratio reaction
181Ta(n,γ)182Ta/181Ta(γ,2n)179Ta for the first plate
of tantalum.
177
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ВОЗБУЖДЕНИЕ НИЗКО-ЛЕЖАЩЕГО ИЗОМЕРНОГО УРОВНЯ ЯДРА 181Та
РЕЛЯТИВИСТСКИМИ ЭЛЕКТРОНАМИ
Н.П. Дикий, A.Н. Довбня, Ю.В. Ляшко, В.И. Никифоров, В.Л. Уваров, И.Д. Федорец
Рассмотрено влияние процессов, обусловленных прохождением сильноточного пучка электронов через
тантал, на скорость заселения E1-уровня 181Ta с энергией 6,24 кэВ, на радиационный захват нейтро-
нов и фотоядерные процессы. Обнаружено усиление фотоядерной реакции 181Ta(γ,2n)179Ta и реакции
радиационного захвата нейтронов 181Ta(n,γ)182Ta при высокой интенсивности высокоэнергетических
электронов.
ЗБУДЖЕННЯ НИЗЬКО-ЛЕЖАЧОГО IЗОМЕРНОГО РIВНЯ ЯДРА 181Та
РЕЛЯТИВIСТСЬКИМИ ЕЛЕКТРОНАМИ
М.П. Дикий, A.М. Довбня, Ю.В. Ляшко, В.I. Нiкiфоров, В.Л. Уваров, I.Д. Федорець
Розглянуто вплив процесiв, обумовлених проходженням потужнострумового пучка електронiв через
тантал, на швидкiсть заселення Е1-рiвня 181Ta з енергiєю 6,24 кeВ, на радiацiйне захоплення нейтронiв
i фотоядернi процеси. Виявлено посилення фотоядерної реакцiї 181Ta(γ,2n)179Ta i реакцiї радiацiйного
захоплення нейтронiв 181Ta(n,γ)182Ta при високiй iнтенсивностi високоенергетичних електронiв.
178
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