The method of branching ratio measurements for nuclear unbound states produced by three particle reactions
The direct method of decay branching ratio determination for nuclear unbound states is proposed. The method is
 based on the complex study of three particle reactions in kinematically complete and incomplete experiments. The
 resonance decay probability is defined as a ratio of exper...
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| Veröffentlicht in: | Вопросы атомной науки и техники |
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| Zitieren: | The method of branching ratio measurements for nuclear unbound states produced by three particle reactions / Yu.N. Pavlenko // Вопросы атомной науки и техники. — 2005. — № 6. — С. 11-16. — Бібліогр.: 21 назв. — англ. |
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| citation_txt | The method of branching ratio measurements for nuclear unbound states produced by three particle reactions / Yu.N. Pavlenko // Вопросы атомной науки и техники. — 2005. — № 6. — С. 11-16. — Бібліогр.: 21 назв. — англ. |
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| container_title | Вопросы атомной науки и техники |
| description | The direct method of decay branching ratio determination for nuclear unbound states is proposed. The method is
based on the complex study of three particle reactions in kinematically complete and incomplete experiments. The
resonance decay probability is defined as a ratio of experimentally observed magnitudes, namely the differential
cross sections corresponding to the processes of resonance excitation and their decay. The most favourable conditions
for such measurements have unbound states with the excitation energy near the decay threshold into the one of
the possible channels. The peculiarities and some applications of the proposed method are discussed.
Запропоновано прямий метод визначення розподілу гілок розпаду незв’язаних станів ядер. Метод базується на комплексному дослідженні тричастинкових реакцій у кінематично повних та неповних експериментах. Ймовірність розпаду резонансів визначається як відношення експериментально спостережуваних величин, а саме диференціальних перерізів, що відповідають процесам збудження резонансів та їх розпаду. Найбільш сприятливі умови для таких вимірювань мають незв’язані стани з енергією збудження, що незначно перевищує поріг розпаду в один з можливих каналів. Аналізуються особливості запропонованого методу, наведено приклади його застосування.
Предложен прямой метод определения распределения ветвей распада несвязанных состояний ядер. Метод основан на комплексном исследовании трехчастичных реакций в кинематически полных и неполных экспериментах. Вероятность распада резонансов определяется как отношение экспериментально наблюдаемых величин, а именно, дифференциальных сечений, соответствующих процессам возбуждения резонансов и их распада. Наиболее благоприятные условия для таких измерений имеют несвязанные состояния с энергией возбуждения, незначительно превышающей порог распада в один из возможных каналов. Анализируются особенности предлагаемого метода, приведены примеры его использования.
|
| first_indexed | 2025-12-07T18:27:46Z |
| format | Article |
| fulltext |
THE METHOD OF BRANCHING RATIO MEASUREMENTS
FOR NUCLEAR UNBOUND STATES PRODUCED
BY THREE PARTICLE REACTIONS
Yu.N. Pavlenko
Institute for Nuclear Research, Kyiv, Ukraine
e-mail: ypavlen@kinr.kiev.ua
The direct method of decay branching ratio determination for nuclear unbound states is proposed. The method is
based on the complex study of three particle reactions in kinematically complete and incomplete experiments. The
resonance decay probability is defined as a ratio of experimentally observed magnitudes, namely the differential
cross sections corresponding to the processes of resonance excitation and their decay. The most favourable condi-
tions for such measurements have unbound states with the excitation energy near the decay threshold into the one of
the possible channels. The peculiarities and some applications of the proposed method are discussed.
PACS: 13.75Gx
1. INTRODUCTION
The main data about nuclear unbound states proper-
ties were obtained at study of binary reactions like
→ i+ j, (1а)
i+j → R →
→ m + n , (1b)
in which these states are produced as intermediate res-
onance systems R decaying into i+j and m+n channels.
Such researches involve laborious measurements of re-
action cross sections with a small energy step of bom-
barding nuclei. In most cases the resonance parameters
are obtained from the analysis of experimental data us-
ing R-matrix theory, which foundations were laid in
work [1]. The important parameters of this and other
more contemporary theories (e.g. [2]) are reduced
widths γij
2, γmn
2 of the channels (1a), (1b) which are ener-
getically independent and characterize the structure of
resonance R. The resonance branches ratio data may be
received from the values of partial widths Гij, Гmn
(Гij+Гmn=Г, where Г is a total level width). The radi-
ation width Гγ may be neglected in comparison with the
particle (m≠0) decay widths. The magnitudes Гij, Гmn, Г
are energetically dependent as Гij=2Рij(Еij)γij
2,
Гmn=2Рmn(Еmn)γmn
2, Рij(Еij) and Рmn(Еmn) being penetrabil-
ity of the Coulomb and centrifugal barriers in corres-
ponding decay channels, Eij , Emn are the relative ener-
gies of decay products. The values of Гij, Гmn are usually
presented at the resonance energy Er. Accordingly the
Гij/Г and Гmn/Г ratios correspond to the decay branches
ratio only at Е = Er energy.
Despite the detailed studies that have been carrying
out for tens of years, there still are significant discrepan-
cies of resonance parameters obtained for a number of
nuclei. The intensively studied “thermonuclear reson-
ance” 5He*(16.75 МеV) may serve as an example. This
resonance was observed at the precision measurements
of energy dependences of cross sections for the reac-
tions (e.g. [3,4])
d+ t→ 5He* → α+ n, (2)
as well as of the total cross sections of elastic neutron
scattering by 4He nuclei [5]. The different values of par-
tial widths for 5He* decay into the channels d+t and
α+n were obtained by different authors, for example
Гdt=33.07 kеV, Гαn=38.83 kеV in [3] and Гdt=25.77 kеV,
Гαn=48.39 kеV in [4]. The detailed analysis of various
approaches for determination of widhts Гdt and Гαn in
binary reactions like (2) was carried out in [6].
Note must be taken that the branches ratios data for
nuclear unbound states produced in many-particle reac-
tions are almost absent till now. The direct method of
the resonance decay probability measurements at the
fixed energy in the input channel of three particle reac-
tions is proposed in the given work. The method is
based on the complex study of these reactions in inclus-
ive and exclusive experiments.
2. DETERMINATION OF RESONANCE
EXCITATION PROBABILITY
IN INCLUSIVE EXPERIMENTS
It is known that in reactions
p+T → k + R (3)
the excitation of recoil nuclei R is provided in the en-
ergy range from 0 to E*
max at the fixed energy of incident
particles Ep (the value of E*
max depends on the type of
particles in the input and exit reaction channels and en-
ergy Ep). If the nucleus R excitation energy in reactions
(3) exceeds the decay threshold on the i+j and m+n
channels, the three particles are produced in the exit
channels:
→ k + i + j, (4а)
p+T → k+R →
→ k + m+ n. (4b)
The complete definition of reaction kinematics is
provided by the measurement of two product’s mo-
mentums, for example, particles k and i or k and m [7,8].
In kinematically incomplete experiments the momentum
of only one final particle is measured. The structure of
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2005, № 6.
Series: Nuclear Physics Investigations (45), p. 11-16. 11
inclusive spectrum of particles k (or differential reac-
tions cross sections
kk dEd
d
Ω
σ2
(5)
of reaction (4)) measured in such experiments are
defined in a great extent by the excitation processes of
recoil nuclei R. By integrating the cross section (5)
measured at the Θk,ϕk angles over the k particle energy
in the range that corresponds to the excitation of ana-
lysed nucleus R the following cross section is obtained:
k
exc
d
d
Ω
σ
. (6)
This cross section characterizes the excitation probabil-
ity of nucleus R which centre of mass according to the
kinematics of reaction (4) must move in the direction
that is determined by the angles ΘR, ϕR=ϕk -180° (see
Fig. 1).
Fig. 1. Vector’s velocity diagram for reaction (4a)
In many cases the cross sections (5) may also have a
continuum part caused by the emission of particles k
from the decay of nuclear unbound states produced in
accompanied reaction channels. For defining the contri-
bution of these processes the well-known procedures of
the inclusive spectra analysis is used (see, e.g. [9]).
3. DETERMINATION OF RESONANCE
DECAY PROBABILITY
IN EXCLUSIVE EXPERIMENTS
At the decay of nucleus R with excitation energy E*
into the channel R→i+j the emission angles of decay
products Θi, ϕi, Θj, ϕj and their velocities Vi, Vj in the
laboratory system are defined by the vectors VR and Vi
R,
Vj
R (Fig. 1). The velocities Vi
R and Vj
R depend on the Q-
value of decay R→i+j: Q=Ei-j=Е*-Еthr, where Еthr is the
energy of decay threshold, Ei-j – relative energy of
particles i and j. The range of possible emission angles
∆Θi= Θi
max-Θi
min, ∆ϕi=ϕi
max-ϕi
min is defined by the ratio
Vi
R/VR and can be simply evaluated (at Vi
R<<VR ) as:
∆Θi = ∆ϕi ≈ 2arctg(Vi
R/VR). (7)
At the fixed angle Θk=const the particle i as a decay
product of unbound state R with excitation energy E*
can be observed within the “cone” defined by the pos-
sible emission angles ∆Θi, ∆ϕi. The information about
of excitation and decay probability of nucleus R into the
channel i+j (reaction (4a)) are contained in the differen-
tial cross sections
)()(
4
jijikk dEddEd
d
ΩΩ
σ , (8)
which are obtained from coincidence spectra of particles
k and i (or k and j). Theoretical interpretation of cross
sections (8) is rather complicated that is why the triple
differential cross sections are used for the analysis:
kjik dEdd
d
)(
3
ΩΩ
σ , (9a)
)()(
3
jijik dEdd
d
ΩΩ
σ . (9b)
(9a) and (9b) are the result of integrating of cross sec-
tions (8) over the energy Ei(j) or Ek around the corres-
ponding kinematical curves (functions Ei(Ek) or Ej(Ek)
determined by the energy and momentum conservation
law).
By integrating of (9a) over the energy of particle k in
the same range as (5) the double differential cross sec-
tion
)(
2
jik dd
d
ΩΩ
σ (10)
can be obtained. This cross section characterises the
probability of formation and decay of nucleus R within
the solid angle dΩi(j) simultaneously. The total probabil-
ity of decay into i+j channel is defined by the ratio
k
exc
k
dec
d
d
d
d
jiP
ΩΩ
=+
σσ
)( , (11)
where
k
dec
d
d
Ω
σ
(12)
is the result of integrating (9) over the solid angles Ωi or
Ωj which determined by the range of all possible angles
Θi, ϕi or Θj, ϕj (see Eq. (7) and Fig. 1). For reaction (4b)
the probability of decay into the channel m+n can be
defined in the same way by the measurements of coin-
cidence spectra of particles k (Θk=const) and m(n) with-
in the solid angle Ωm(n).
4. PECULIARITIES OF RESONANCES
DECAY PROBABILITY MEASUREMENTS
The procedure of determination of reaction cross
sections (6) is well known and in most cases not diffi-
cult. Now the technique of coincidence measurements is
also well developed. But the long measurement’s time is
the main shortcoming of such experiments. However the
differential cross sections (8)-(10) of different reactions
like (4) have been measured in lots of experiments. It
gave the possibility to study reaction dynamics effects
as well as to get the values of resonance parameters of
many nuclear unbound states produced by these reac-
12
tions. But the branches ratio data have not been obtained
even until now because of the absence of experimental
data about the cross sections (12). The cross sections
(10) have been usually measured at limited sets of regis-
tration angles of reaction products. But the detailed an-
gular correlations data covered the whole range of emis-
sion angles ∆Θ, ∆ϕ (see (7)) are needed to obtain the
cross sections (12). For most unbound states produced
by reactions (4) at low and middle energies of incident
particles this angular range is sufficiently large.
The most favourable conditions of the decay probab-
ility measurements have unbound states with the excita-
tion energy slightly exceeds the decay threshold into the
one of the possible channels (e.g. i+j). For such states
the angular range of decay consists of ∆Θi(j)~10°…30°,
that is quite acceptable for the measurements. The vivid
example of state with excitation energy near the decay
threshold is the mentioned above “thermonuclear reson-
ance” 5He*(16.75 МеV). At the formation of this reson-
ance in reaction
→ α+α+ n (13а)
d+7Li → α+5He*→
→ α+ t + d (13b)
at deuteron energies Еd > 30 МеV it is easy to provide
such solid angle ∆Ωt(d) of tritons or deuterons registra-
tion which would cover all the possible decay angles
into the channel 5He*→ t+d. The whole range of these
angles is very small due to the small value of relative
energy of deuterons and tritons (Еt-d= 0.05 МеV) while
5He* centre of mass energy at different emission angles
in reaction (13) at Еd=30 МеV consists of 10…20 МеV.
In this case the decay products can be registered by the
detectors with relatively small aperture.
Generally the multi-element silicon detectors with
large total square of sensitive surface can be effectively
used for registration of decay products [10]. The whole
range ∆Θi(j) can be covered by full aperture of such de-
tector. At the same time the cross sections (8)-(10) are
measured with high angular resolution because of sim-
ultaneous using each element of detector. At ∆Θi(j)≤10°
the whole decay cone can be covered even by one-ele-
ment detector with not very big aperture.
According to the theory of many particle nuclear re-
actions [11] the cross sections of reactions (4) depend
on the three-body scattering amplitudes, which in the
assumption of dominating role of pair forces are defined
by the two-particle amplitudes, which correspond to the
interaction of every particle pair in the final state. That
is why it is very important to choose for measurements
such regions of phase space where the interaction of one
particle pair dominates. In our case it is the pair of
particles i and j, which interaction is responsible for
formation of the R resonance in reaction (4a).
The velocity diagram on Fig. 1 corresponds to the
ideal conditions of decay probability measurements for
the states with Γ=0. For real states the change of excita-
tion energy within the limits of ∆Е*~(2…3)Γ causes
certain modification of energy of particles k (∆Еk) detec-
ted at fixed angle Θk also as modification of energy (∆
ЕR) and emission angle (∆ΘR) of nuclei R and relative
energies of decay products ∆Еij =∆Еmn=∆Е*. The men-
tioned factors (∆ЕR, ∆ΘR and ∆Еij) lead to the change of
maximal and minimal observation angles of nuclei R de-
cay products, that is to the range ∆Θi(j), ∆ϕi(j) widening.
The additional widening of this range and modification
of differential cross sections (8), (9) are caused by a
number of conditions of carrying out the real experi-
ments. There are beam energy dispersion (∆Ep), beam
spot size on the target, target thickness, solid angles (∆
Ωk, ∆Ω i(j)) and energy resolution of the detectors used
for the reaction products registration. .
One of the best methods of taking into account all
these factors is the simulation of the investigated pro-
cesses by Monte-Carlo method [12]. Fig. 2 contains the
simulated differential cross sections (8), (9) which cor-
respond to the excitation and decay of 7Li*(7.45 МеV)
nuclei into the 6Li+n channel in reaction
α+7Li → α+7Li* → α+6Li+n (14)
at the beam energy of 27.2 MeV.
Fig. 2. Monte-Carlo simulation of α-6Li coincidence
spectra (a,b – differential cross sections (8) and (9), re-
spectively) for reaction (14) in the region of excitation
and decay of 7Li*(7.45 МеV) into the 6Li+n channel. E1
and E2 are the energies of α-particles and 6Li nuclei re-
gistered at Θ1=34°, φ1=0° and Θ2=44.5°, φ2=180°, re-
spectively
The real conditions of coincidence measurements
have been used for these simulations. In particular, the
solid angles of α-particles and 6Li registration were ∆
Ω1=0.76ּ10–3 sr and ∆Ω2=2.72ּ10–3 sr, respectively. The
total solid angle of decay into the 6Li+n channel consists
of ∆Ω2=3.55ּ10–2 sr. The space distribution of α-6Li co-
13
incidence events simulated for 6Li-detector plane is
shown in Fig. 3.
Fig. 3. The space distribution of α-6Li coincidence
events simulated for reaction (14) and shown in the
plane of 6Li-detector placed at the distance of 127 mm
from the target. The point x=y=0 corresponds to the
angles Θ2=46.5°, φ2=0°
Fig. 4. Inclusive spectrum of α-particles for reaction (14)
Fig. 5. α-6Li coincidence spectra (a,b – differential
cross sections (8) and (9), respectively) measured for
reaction (14). E1 and E2 are the energies of α-particles
and 6Li nuclei registered at Θ1=34°, φ1=0° and Θ
2=44.5°, φ2=180°, respectively. Solid line is the kin-
ematical curve for reaction (14)
If the detector’s aperture does not completely covers
the angular range of decay it would be appropriate to
calculate a “registration efficiency”:
ε = Ni(j / NR, (15)
where NR – the number of excited recoil nuclei R or cor-
responding particles k detected without coincidences
with other particles, Ni(j) – the number of particles k de-
tected in coincidences with one of the particles from de-
cay R→i+j. The number NR defines the value of cross
sections (5), (6) and Ni(j) – of cross sections (8)-(10).
5. EXAMPLE OF METHOD APPLICATION
The Monte-Carlo simulations of differential cross
sections (5), (6), (8)-(10) and “registration efficiency”
(15) were used to choose the optimal conditions of
7Li*(7.45 МеV) decay probability measurements in re-
action (14). This experiment was performed at the incid-
ent α-particle’s energy of 27.2 МеV at the cyclotron U-
120 of the Institute of Nuclear Research (Kyiv).
The inclusive spectrum of α-particles (differential
cross section (5)) that was measured for this reaction at
the angles Θα=34°, φα=0° [13] is shown in Fig. 4. The
peaks observed in the spectrum correspond to the elastic
and inelastic scattering of α-particles by 7Li and target
admixture nuclei of 6Li, 12C, 19F and Ni. Continuum part
of spectrum observed at low energies is caused by the
registration of α-particles as the products of decay of
nuclear unbound states produced by inelastic scattering
and others accompanied reaction channels. Using the
procedure given in [9] the differential cross section (6)
corresponding to the excitation of 7Li*(7.45 МеV) nuc-
leus has been obtained from this spectrum. According to
the kinematics of reaction 7Li(α,α)7Li* the centre of
mass of 7Li* must move at the angles Θ7Li*=46.5°,
φ7Li*=180°.
The α-6Li coincidence spectra have been measured
around this direction within the range ΔΘ6Li=Δφ6Li=12°
(at fixed angles Θα=34°, φα=0°) which covered all pos-
sible emission angles of 6Li as a product of
7Li*(7.45 МеV) decay. The example of coincidence
spectra (differential cross sections (8) and (9)) is shown
in Fig. 5. The most intensive peak in Fig. 5b corres-
ponds to the contribution of 7Li*(7.45 МеV) excitation
and decay into 6Li+n channel.
14
Fig. 6. The Θ2-angular dependence of measured and
simulated differential cross sections (10) for one of the
angle values φ2= φ6Li= - 6°
By integrating the cross sections (9) over Eα energy
within this peak the differential cross sections (10) have
been obtained. Their angular dependence is shown in
Fig. 6. And finally by integrating the measured cross
sections (10) over the Θ2, φ2 angles the cross section
(12) has been obtained. Its ratio to cross section (6) de-
termined from the inclusive α-particle spectrum accord-
ing to (11) is the probability of 7Li*(7.45 МеV) decay
into the 6Li+n channel.
The value of ratio (11) consists of P(n+6Li)= 0.49±
0.06 that significantly differs from the results of binary
reactions studies. This level was observed as pro-
nounced resonance at low energy interaction of neutrons
with 6Li nuclei [14] and α-particles with tritons [15].
The resonance has a large neutron width and a small α-
width (γn
2/γα
2=48, Γn(Er)/Γ(Er)=0.77, σn/σtot= 0.71 [14],
where σtot is the total neutron cross section, σn is the
cross section of n+6Li elastic scattering).
Extremely large width (Γ~0.5 MeV) of 5He* “ther-
monuclear resonance” with respect to the standard value
(Γ~0.076 MeV [16]) was deduced from experimental
data for reaction (13a) in Ref. [17]. The strong modific-
ation of branching ratio for this resonance was also ob-
served at the study of reactions (13a) and (13b) at deu-
teron energy of 37 MeV [18]. The spectrum of α-
particles measured in coincidences with tritons (reaction
(13b)) is shown in Fig. 7. High registration efficiency (ε
=0.46, see Eq. (15)) for reaction channel (13b) was
achieved due to the large solid angle (∆Ω2=1.82ּ10–2 sr)
of detector used for the registration of tritons. The pro-
nounced peak at the energy of Eα=14.8 MeV corres-
ponds to the contribution of narrow (Γ=24 keV, [16])
resonance of 6Li*(2.185 MeV). The broadening of the
observed peak is mainly caused by large value of the
solid angle ∆Ω2. It is well reproduced by Monte-Carlo
calculations. The middle part of spectrum corresponds
to the possible contribution of other states of 5He* with
excitation energy E*>18 MeV [16,19] or 6Li* with
E*>4 MeV [16].
Fig. 7. Reaction 7Li(d,αt)d at Ed=37 MeV. The spec-
trum of α-particles (Θ1=45°, φ1=0°) measured in coin-
cidences with tritons (Θ2=79°, φ2=180°). The results of
Monte Carlo simulations of the excitation and decay of
5He*(16.75 MeV) and 6Li*(2.185 MeV) unbound states
are shown as histograms
Contrary to the binary reactions the formation and
decay of 7Li*(7.45 МеV) in three particle reaction (14)
as well as 5He*(16.75 MeV) in reaction (13) occurs with
the presence of accompanying α-particles. The influence
of its Coulomb field may be one of the reasons for a
modification of resonance decay branches ratio in com-
parison with the binary reactions [11,20,21].
CONCLUSIONS
The method proposed for the determination of decay
branching ratio for nuclear unbound states produced by
three-particle reactions (4) is based on the measure-
ments of differential cross sections of these reactions in
kinematically complete and incomplete experiments.
The method has many advantages over the known pro-
cedures, developed for binary reactions (1). Firstly, this
is a method of direct measurement of decay probability
of resonance states into one or two channels as it is
defined as a ratio of experimentally observed mag-
nitudes, namely the number of nuclei decaying into the
given channel to the number of excited nuclei (see (11)).
Secondly, the method needs no implication of theoretic-
al analysis. Thirdly, there is no need to measure the
cross sections of reactions at different energies of incid-
ent particles.
Besides mentioned above resonances of 5He* and
7Li* the method can be used for the measurement of the
decay probability of many other nuclear states. It is
most suitable for the states which excitation energy
slightly exceeds the decay threshold into one of the
probable channels, for example: 4He*(21.1 МеV)→
3He+n, 5He*(19.8 МеV)→ 3He+2n, 5Li*(16.6 МеV)→
3He+d, 7Li*(9.9 МеV)→6He+p, 8Be*(18.91 МеV)→
7Li+p, 8Be*(22.2 МеV)→6Li+d and others. The experi-
mental data about the decay branches ratios for such
nuclei states are important for testing of existing theor-
ies of many particle reactions and further study of influ-
ence effects of accompanying particles on the processes
of formation and decay of short lived nuclear states. The
results of experimental and theoretical works [13,20,21]
prove the availability of this research direction.
This work has been supported in part by the Funda-
mental Researches State Fund of Ukraine under Grant
02.07/00244.
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117 keV // Phys. Rev. C. 1984, v. 29, p. 2031-
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МЕТОД ИЗМЕРЕНИЯ РАСПРЕДЕЛЕНИЯ ВЕТВЕЙ РАСПАДА НЕСВЯЗАННЫХ
СОСТОЯНИЙ ЯДЕР В ТРЕХЧАСТИЧНЫХ РЕАКЦИЯХ
Ю.Н. Павленко
Предложен прямой метод определения распределения ветвей распада несвязанных состояний ядер. Ме-
тод основан на комплексном исследовании трехчастичных реакций в кинематически полных и неполных
экспериментах. Вероятность распада резонансов определяется как отношение экспериментально наблюдае-
мых величин, а именно, дифференциальных сечений, соответствующих процессам возбуждения резонансов
и их распада. Наиболее благоприятные условия для таких измерений имеют несвязанные состояния с энер-
гией возбуждения, незначительно превышающей порог распада в один из возможных каналов. Анализиру-
ются особенности предлагаемого метода, приведены примеры его использования.
МЕТОД ВИМІРЮВАННЯ РОЗПОДІЛУ ГІЛОК РОЗПАДУ НЕЗВ’ЯЗАНИХ
СТАНІВ ЯДЕР В ТРИЧАСТИНКОВИХ РЕАКЦІЯХ
Ю.М. Павленко
16
Запропоновано прямий метод визначення розподілу гілок розпаду незв’язаних станів ядер. Метод
базується на комплексному дослідженні тричастинкових реакцій у кінематично повних та неповних
експериментах. Ймовірність розпаду резонансів визначається як відношення експериментально
спостережуваних величин, а саме диференціальних перерізів, що відповідають процесам збудження
резонансів та їх розпаду. Найбільш сприятливі умови для таких вимірювань мають незв’язані стани з
енергією збудження, що незначно перевищує поріг розпаду в один з можливих каналів. Аналізуються
особливості запропонованого методу, наведено приклади його застосування.
17
Institute for Nuclear Research, Kyiv, Ukraine
The main data about nuclear unbound states properties were obtained at study of binary reactions like
It is known that in reactions
|
| id | nasplib_isofts_kiev_ua-123456789-81214 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 1562-6016 |
| language | English |
| last_indexed | 2025-12-07T18:27:46Z |
| publishDate | 2005 |
| publisher | Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
| record_format | dspace |
| spelling | Pavlenko, Yu.N. 2015-05-13T16:28:14Z 2015-05-13T16:28:14Z 2005 The method of branching ratio measurements for nuclear unbound states produced by three particle reactions / Yu.N. Pavlenko // Вопросы атомной науки и техники. — 2005. — № 6. — С. 11-16. — Бібліогр.: 21 назв. — англ. 1562-6016 https://nasplib.isofts.kiev.ua/handle/123456789/81214 PACS: 13.75Gx The direct method of decay branching ratio determination for nuclear unbound states is proposed. The method is
 based on the complex study of three particle reactions in kinematically complete and incomplete experiments. The
 resonance decay probability is defined as a ratio of experimentally observed magnitudes, namely the differential
 cross sections corresponding to the processes of resonance excitation and their decay. The most favourable conditions
 for such measurements have unbound states with the excitation energy near the decay threshold into the one of
 the possible channels. The peculiarities and some applications of the proposed method are discussed. Запропоновано прямий метод визначення розподілу гілок розпаду незв’язаних станів ядер. Метод базується на комплексному дослідженні тричастинкових реакцій у кінематично повних та неповних експериментах. Ймовірність розпаду резонансів визначається як відношення експериментально спостережуваних величин, а саме диференціальних перерізів, що відповідають процесам збудження резонансів та їх розпаду. Найбільш сприятливі умови для таких вимірювань мають незв’язані стани з енергією збудження, що незначно перевищує поріг розпаду в один з можливих каналів. Аналізуються особливості запропонованого методу, наведено приклади його застосування. Предложен прямой метод определения распределения ветвей распада несвязанных состояний ядер. Метод основан на комплексном исследовании трехчастичных реакций в кинематически полных и неполных экспериментах. Вероятность распада резонансов определяется как отношение экспериментально наблюдаемых величин, а именно, дифференциальных сечений, соответствующих процессам возбуждения резонансов и их распада. Наиболее благоприятные условия для таких измерений имеют несвязанные состояния с энергией возбуждения, незначительно превышающей порог распада в один из возможных каналов. Анализируются особенности предлагаемого метода, приведены примеры его использования. This work has been supported in part by the Fundamental Researches State Fund of Ukraine under Grant 02.07/00244. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Ядерная физика и элементарные частицы The method of branching ratio measurements for nuclear unbound states produced by three particle reactions Метод вимірювання розподілу гілок розпаду незв’язаних станів ядер в тричастинкових реакціях Метод измерения распределения ветвей распада несвязанных состояний ядер в трехчастичных реакциях Article published earlier |
| spellingShingle | The method of branching ratio measurements for nuclear unbound states produced by three particle reactions Pavlenko, Yu.N. Ядерная физика и элементарные частицы |
| title | The method of branching ratio measurements for nuclear unbound states produced by three particle reactions |
| title_alt | Метод вимірювання розподілу гілок розпаду незв’язаних станів ядер в тричастинкових реакціях Метод измерения распределения ветвей распада несвязанных состояний ядер в трехчастичных реакциях |
| title_full | The method of branching ratio measurements for nuclear unbound states produced by three particle reactions |
| title_fullStr | The method of branching ratio measurements for nuclear unbound states produced by three particle reactions |
| title_full_unstemmed | The method of branching ratio measurements for nuclear unbound states produced by three particle reactions |
| title_short | The method of branching ratio measurements for nuclear unbound states produced by three particle reactions |
| title_sort | method of branching ratio measurements for nuclear unbound states produced by three particle reactions |
| topic | Ядерная физика и элементарные частицы |
| topic_facet | Ядерная физика и элементарные частицы |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/81214 |
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