On the mechanism of ⁴He(γ, pn)²H reaction
The interpretation is given on the effect of two "peaks" appearance in the experimental deuteron energy distributions in the ⁴He(g, pn)²H reaction with photon energies Eg=30...50 MeV. The mechanism of pole ²H-diagram determining the first "peak" motion and the mechanism of triang...
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| Опубліковано в: : | Вопросы атомной науки и техники |
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| Дата: | 2011 |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2011
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| Цитувати: | On the mechanism of ⁴He(γ, pn)²H reaction / V.N. Guryev // Вопросы атомной науки и техники. — 2011. — № 3. — С. 27-30. — Бібліогр.: 17 назв. — англ. |
Репозитарії
Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859625892314087424 |
|---|---|
| author | Guryev, V.N. |
| author_facet | Guryev, V.N. |
| citation_txt | On the mechanism of ⁴He(γ, pn)²H reaction / V.N. Guryev // Вопросы атомной науки и техники. — 2011. — № 3. — С. 27-30. — Бібліогр.: 17 назв. — англ. |
| collection | DSpace DC |
| container_title | Вопросы атомной науки и техники |
| description | The interpretation is given on the effect of two "peaks" appearance in the experimental deuteron energy distributions in the ⁴He(g, pn)²H reaction with photon energies Eg=30...50 MeV. The mechanism of pole ²H-diagram determining the first "peak" motion and the mechanism of triangular ³He(³H)-diagrams showing a fixed appearance of the second "peak" with a deuteron energy Em₂H=2.22 MeV due to the root singularity in the p + n → ²H vertex are taken into account. The position of maxima in the calculated distributions by the relative pn-pair energy, going out from the photon vertex, coincides in the diagrams under consideration for Eg=45...150 MeV.
Надано інтерпретацію ефекту появи двох "піків" в експериментальних енергетичних розподілах дейтронів в реакції ⁴He(g, pn)²H при енергіях фотонів Eg=30...50 МеВ з урахуванням механізму полюсної ²H-діаграми, визначаючим рух першого "піку", і механізму трикутних ³He(³H)-діаграм з фіксованим проявом другого піку з енергією дейтрона Em₂H=2.22 МеВ через корневу особливість у вершині p + n → ²H. Положення максимумів у розрахункових розподілах по відносній енергії pn-пари, що виходять з фотонної вершини, співпадає для розглянутих діаграм при Eg=45...150 МеВ.
Дана интерпретация эффекта проявления двух "пиков" в экспериментальных энергетических распределениях дейтронов в реакции ⁴He(g, pn)²H при энергиях фотонов Eg=30...50 МэВ с учетом механизма полюсной ²H -диаграммы, определяющим движение первого "пика", и механизма треугольных ³He(³H) диаграмм с фиксированным проявлением второго пика с энергией дейтрона Em₂H=2.22 МэВ из-за корневой особенности в вершине p + n → ²H. Положение максимумов в расчетных распределениях по относительной энергии pn-пары, выходящих из фотонной вершины, совпадает для рассмотренных диаграмм при Eg=45...150 МэВ.
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| first_indexed | 2025-11-29T10:31:22Z |
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ON THE MECHANISM OF 4He(γ, pn)2H REACTION
V.N. Guryev∗
National Science Center ”Kharkov Institute of Physics and Technology”, 61108, Kharkov, Ukraine
(Received April 11, 2011)
The interpretation is given on the effect of two ”peaks” appearance in the experimental deuteron energy distributions
in the 4He(γ, pn)2H reaction with photon energies Eγ=30...50 MeV. The mechanism of pole 2H-diagram determining
the first ”peak” motion and the mechanism of triangular 3He(3H)-diagrams showing a fixed appearance of the second
”peak” with a deuteron energy Em
2H=2.22 MeV due to the root singularity in the p + n → 2H vertex are taken into
account. The position of maxima in the calculated distributions by the relative pn-pair energy, going out from the
photon vertex, coincides in the diagrams under consideration for Eγ=45...150 MeV.
PACS: 25.20.-x
1. INTRODUCTION
The interest to the problem of three-particle pho-
todisintegration of 4He nucleus is determined by
the possibility of proving the notions about nuclear
forces, nucleon-nucleon correlations, cluster configu-
rations and meson exchange currents in nuclei. All
these questions are associated with determination of
a reaction mechanism. According to the experimen-
tal investigations [1] (FIAN, Moscow; Wilson cham-
ber), [2-4] (NSC KIPT; diffusion chamber in the
magnetic field), [5] (Turino, Italy; diffusion cham-
ber in the magnetic field) and theoretical research
[6-12] carried out in 60-70 years using the photon
energies Eγ=26...150 MeV the main mechanism of
4He(γ, pn)2H reaction is the photon absorption by
the pair of nucleons (quasideuteron) being at a short
distance from each other. In the 80-th years these
investigations were continued at the Kharkov Insti-
tute of Physics and Technology using the experimen-
tal data obtained by means of a diffusion chamber
with an appreciably improved statistics (4.5 thousand
of events for the given reaction) [13-15].
A satisfactory fit was obtained for the theoreti-
cal estimated values to a pole quasideuteron approx-
imation and the experimental energy distributions of
deuterons, protons, neutrons, pair (pn), (pd), (nd)
correlations and angular (pn) correlations. In [15] a
contribution of triangular 3H, 2H and A=3-Feynman
diagrams was analyzed and a little importance of the
final state interaction (FSI) even with low energies
Eγ was stated. However, the interpretation of an ef-
fect of the appearance of two maxima at Eγ ∼50 and
75 MeV in the energy distributions of total cross-
sections of the σt(Eγ)4He(γ, pn)2H reaction should
be considered as one of unsolved theoretical prob-
lems.
Also, unsolved was a problem of two ”peaks” ap-
pearance in the experimental dN/dEd energies distri-
butions of deuterons [14] with Em
d (I) ≈1.25 MeV and
Em
d (II) ≈2.5 MeV at Eγ=28...45 and 28...50 MeV,
their contributions to the reaction section being
changing with Eγ increasing (the first ”peak” be-
comes blurry and the second ”peak” becomes dis-
tinct). The interpretation of this effect is given in
Section 2 within the bounds of extension of the mech-
anism of 4He(γ, pn)2H reaction with taking into ac-
count a pole quasi-deuteron mechanism and 3He(3H)-
triangular diagrams which differ markedly from the
triangular diagrams [15] by the (np)-pair knocking-
out from the photon vertex.
2. MECHANISMS OF 4He(γ,pn)2H
REACTION IN THE DIAGRAM
REPRESENTATION
The pole mechanism of 4He(γ, pn)2H reac-
tion, being discussed in the introduction, cor-
responds to the Feynman pole diagram (Fig.1)
with a quasi-deuteron photodisintegration outside
the mass surface in the photon vertex 1 and
with a nuclear form-factor in spectator channel 2.
Fig.1. Pole quasideuteron diagram for the
4He(γ, pn)2H reaction
∗Corresponding author E-mail address: guryev@kipt.kharkov.ua
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2011, N3.
Series: Nuclear Physics Investigations (55), p.27-30.
27
In the first approximation, to take into account
only the pole mechanism features, vertex 1 and ver-
tex 2 of Fig.1 are replaced by the constants. Then
the distributions (being the most sensitive to the re-
action mechanism) by the relative energy of (pn) pair,
dΛ/dtpn, and the kinetic energy of deuteron, dΛ/dEd,
take the following form [13,16]
dΛ
dtpn
= C1[
ε′
E0
+ (1− tpn)]−2 · dV
dtpn
, (1)
dV
dtpn
= C21[tpn(1− tpn)]1/2 , (2)
dΛ
dEd
= C3[ε′
md
mHe
+ Ed]−2 · dV
dEd
, (3)
dV
dEd
= C4[Ed(E0 − Ed
md + mp + mn
mp + mn
)]1/2 , (4)
where dV/dtpn and dV/dEd are the phase dis-
tributions, ε′ = 2md − mHe, E0 = Eγ − ε,
ε = md + mp + mn −mHe, tpn = Epn/E0, Epn and
Ed are the relative energy of (pn)-pair and the kinetic
energy of deuteron in the c.m.s. reaction respectively,
C1...C4 are the constants.
The distributions (1) and (3) correspond to the
experimental data [14] and [13] at Eγ=30...45 MeV,
45...75 MeV and Eγ=28...150 MeV respectively with
a normalization performed for the total number of
events. The taking into account of triangular dia-
grams for the 4He(γ, pn)2H reaction is considered
in [15] and presented in Fig.2. The calculations
of dΛ/dEp, dΛ/dEn, dΛ/dEd in [15] did not allowed
one to describe simultaneously, within the theory
domain [17], the experimental energy spectra of all
the 4He(γ, pn)2H reaction products in the region of
Eγ=26...50 MeV and 50...150 MeV and opened to
question the role of FSI in this reaction.
Fig.2. Triangular diagrams [15] for the 4He(γ, pn)2H reaction
In [14] one discovered, but did not explained,
the effect of two ”peaks” appearance in dN/dEd for
Em
d =1.25 and 2.5 MeV at Eγ= 28...45 MeV and
28...50 MeV the contributions of which to the reac-
tion cross-section was varying depending on Eγ .
Table 1.
Eγ 28...30 30...35 35...40 40...50
Em
d (I), MeV 0.66±0.20 1.25±0.35 1.81±0.26 2.39±0.29
Em
d (II), MeV 2.22 2.22 2.22
In the present paper this effect was obtained tak-
ing into account the pole 2H-diagram (Fig.1) with
the distribution dΛ/dEd in equation (3) and with
taking into account the triangular 3He(3H)-diagrams
(Fig.3) (being qualitative different from the triangu-
lar diagram of Fig.2) with a root singularity in the
p + n →2 H vertex on the mass shell at a deuteron
kinetic energy E∗
d , according to the theory [17], equal
to
dEm
d (II) = mp + mn −m2H = 2.22 MeV . (5)
This values of E∗
d(II), owing to proper singular-
ity’s triangular diagram independence on Eγ [17], de-
termines the position of the stable second ”peak” (5)
at Eγ ≥30 MeV. At the same time, the first ”peak”,
unlike the interpretation in [14], moving with Eγ
changing, is related with the motion of a maximum
of E∗
d(I) in the distribution dΛ/dEd (3), the position
of which is determined by the standard procedure of
extremum calculation (3)
dEm
d (I) =
3E0 + 48− [9E2
0 + 96E0 + (48)2]1/2
8
.
(6)
In Table 1 given are the calculation results for
Em
d (I) by formula (6) and for Em
d (II) by formula
(5) with taken into account the divergances from
the average values of E0 for the intervals of en-
ergy Eγ=28...30, 30...35, 35...40 and 40...50 MeV.
In whole, a noncontradictory agreement between the
model estimates and the experiment takes place.
It is interesting to compare for the diagrams of
Fig.1 and Fig.3 the estimated values of tmpn in the
distributions of maxima dΛ/dtpn in the different en-
28
ergy intervals Eγ , where tpn = Epn/E0. For the pole
2H-diagram formula (1) takes place and for the tri-
angular 3He(3H)-diagrams we use a general equation
for the 4He(γ, pn)2H reaction [1,14].
Epn
E0
= 1− Ed
Emax
d
, (7)
where
Emax
d = E0
mp + mn
md + mp + mn
(8)
Taking into consideration (5) we obtain
tmpn =
Em
pn
E0
= 1− 2Em
d (II)
E0
(9)
n(p)
p(n)
3He(3H)
2H
n
p
γ
4He
Fig.3. Triangular 3He(3H) diagrams for the
4He(γ, pn)2H reaction
In Table 2 given are the estimated val-
ues of tmpn(1) for the distributions dΛ/dtmpn (1),
normalized to all the events, and the esti-
mates of tmpn(9) by (9) with taking into ac-
count the divergences from the average values
of E0 for Eγ=30...45, 45...75 and 75...150 MeV.
Table 2.
Eγ 30...45 45...75 75...150
tmpn(1) 0.65±0.10 0.82±0.05 0.92±0.02
tmpn(9) 0.61±0.23 0.87±0.07 0.95±0.03
As is obvious from Table 2 the estimates of tmpn(1)
and tmpn(9) are coinciding for Eγ=45...150 MeV. For
phase distributions (2) tpn=0.5. From the experimen-
tal analysis of pn-correlations it is practically impos-
sible to single out the mechanisms of 4He(γ, pn)2H
reactions presented in Figs.1 and 3.
3. DISCUSSION
In the present paper, taking into account the exper-
imental appearance of two ”peaks” in the deuteron
energy distribution un the range of Eγ=28...50 MeV,
for the first time a conclusion (Table 1) was made
about the contribution to the 4He(γ, pn)2H reac-
tion not only from the mechanism of a pole quasi-
deuteron diagram (see Fig.1) with the first ”peak”
Em
d (I) moving at an energy Eγ according to Equa-
tion (6), but, also, from the mechanism of triangu-
lar 3He(3H)-diagrams presented in Fig.3 with a fixed
root singularity Em
d (II)=2.22 MeV in the p+n →2 H
vertex. It has been shown that the positions of max-
ima tmpn(1) in the distributions dΛ/tpn(1) for the pole
2H-diagram and tmpn(9) with Em
d (II), practically, are
coinciding in the range of Eγ=45...150 MeV (Tabl.2).
And, therefore, from the experimental analysis of
(pn)-correlations one had not succeeded previously
to single out the contribution of triangular 3He(3H)-
diagram.
Taking into consideration the results obtained
upon the mechanisms of 4He(γ, pn)2H reaction, of
particular interest is the experimental and theoret-
ical analysis of residual nuclei (10B, 12C and 14N)
energy distributions in the reactions 12C(γ, pn)10B,
14N(γ, pn)12C and 16O(γ, pn)14N .
References
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29
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О МЕХАНИЗМЕ РЕАКЦИИ 4He(γ, pn)2H
В.Н. Гурьев
Дана интерпретация эффекта возникновения двух "пиков"в экспериментальных энергетических рас-
пределениях дейтронов в реакции 4He(γ, pn)2H при энергиях фотонов Eγ=30...50 МэВ с учетом меха-
низма полюсной 2H-диаграммы, определяющим движение первого "пика", и механизма треугольных
3He(3H) диаграмм с фиксированным проявлением второго пика с энергией дейтрона Em
2H=2.22 МэВ
из-за корневой особенности в вершине p+n →2H. Положение максимумов в расчетных распределениях
по относительной энергии pn-пары, выходящих из фотонной вершины, совпадает для рассмотренных
диаграмм при Eγ=45...150 МэВ.
ПРО МЕХАНIЗМ РЕАКЦIЇ 4He(γ, pn)2H
В.М. Гур’ев
Надано iнтерпретацiю ефекту появи двох "пiкiв"в експериментальних енергетичних розподiлах дей-
тронiв в реакцiї 4He(γ, pn)2H при енергiях фотонiв Eγ=30...50 МеВ з урахуванням механiзму полюсної
2H-дiаграми, визначаючим рух першого "пiку", i механiзму трикутних 3He(3H)-дiаграм з фiксова-
ним проявом другого пiку з енергiєю дейтрона Em
2H=2.22 МеВ через корневу особливiсть у вершинi
p + n →2 H. Положення максимумiв у розрахункових розподiлах по вiдноснiй енергiї pn-пари, що ви-
ходять з фотонної вершини, спiвпадає для розглянутих дiаграм при Eγ=45...150 МеВ.
30
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| id | nasplib_isofts_kiev_ua-123456789-111131 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-11-29T10:31:22Z |
| publishDate | 2011 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Guryev, V.N. 2017-01-08T14:43:35Z 2017-01-08T14:43:35Z 2011 On the mechanism of ⁴He(γ, pn)²H reaction / V.N. Guryev // Вопросы атомной науки и техники. — 2011. — № 3. — С. 27-30. — Бібліогр.: 17 назв. — англ. 1562-6016 PACS: 25.20.-x https://nasplib.isofts.kiev.ua/handle/123456789/111131 The interpretation is given on the effect of two "peaks" appearance in the experimental deuteron energy distributions in the ⁴He(g, pn)²H reaction with photon energies Eg=30...50 MeV. The mechanism of pole ²H-diagram determining the first "peak" motion and the mechanism of triangular ³He(³H)-diagrams showing a fixed appearance of the second "peak" with a deuteron energy Em₂H=2.22 MeV due to the root singularity in the p + n → ²H vertex are taken into account. The position of maxima in the calculated distributions by the relative pn-pair energy, going out from the photon vertex, coincides in the diagrams under consideration for Eg=45...150 MeV. Надано інтерпретацію ефекту появи двох "піків" в експериментальних енергетичних розподілах дейтронів в реакції ⁴He(g, pn)²H при енергіях фотонів Eg=30...50 МеВ з урахуванням механізму полюсної ²H-діаграми, визначаючим рух першого "піку", і механізму трикутних ³He(³H)-діаграм з фіксованим проявом другого піку з енергією дейтрона Em₂H=2.22 МеВ через корневу особливість у вершині p + n → ²H. Положення максимумів у розрахункових розподілах по відносній енергії pn-пари, що виходять з фотонної вершини, співпадає для розглянутих діаграм при Eg=45...150 МеВ. Дана интерпретация эффекта проявления двух "пиков" в экспериментальных энергетических распределениях дейтронов в реакции ⁴He(g, pn)²H при энергиях фотонов Eg=30...50 МэВ с учетом механизма полюсной ²H -диаграммы, определяющим движение первого "пика", и механизма треугольных ³He(³H) диаграмм с фиксированным проявлением второго пика с энергией дейтрона Em₂H=2.22 МэВ из-за корневой особенности в вершине p + n → ²H. Положение максимумов в расчетных распределениях по относительной энергии pn-пары, выходящих из фотонной вершины, совпадает для рассмотренных диаграмм при Eg=45...150 МэВ. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Ядерная физика и элементарные частицы On the mechanism of ⁴He(γ, pn)²H reaction Про механiзм реакцiї ⁴He(γ, pn)²H О механизме реакции ⁴He(γ, pn)²H Article published earlier |
| spellingShingle | On the mechanism of ⁴He(γ, pn)²H reaction Guryev, V.N. Ядерная физика и элементарные частицы |
| title | On the mechanism of ⁴He(γ, pn)²H reaction |
| title_alt | Про механiзм реакцiї ⁴He(γ, pn)²H О механизме реакции ⁴He(γ, pn)²H |
| title_full | On the mechanism of ⁴He(γ, pn)²H reaction |
| title_fullStr | On the mechanism of ⁴He(γ, pn)²H reaction |
| title_full_unstemmed | On the mechanism of ⁴He(γ, pn)²H reaction |
| title_short | On the mechanism of ⁴He(γ, pn)²H reaction |
| title_sort | on the mechanism of ⁴he(γ, pn)²h reaction |
| topic | Ядерная физика и элементарные частицы |
| topic_facet | Ядерная физика и элементарные частицы |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/111131 |
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