γ-decay of resonance-like structure observed in ³⁰Si(p,γ)³¹p reaction
γ-Decay of a resonance-like structure observed in the reaction ³⁰Si(p,γ)³¹p in the energy region Ep=1.4-2.7 MeV of accelerated protons is studied. The M1 resonance built on the ground state of ³¹P is identified. The position of the M1 resonance is explained taking into account pairing forces....
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| Cite this: | γ-decay of resonance-like structure observed in ³⁰Si(p,γ)³¹p reaction / A.S. Kachan, A.N. Vodin, V.Yu. Korda, L.P. Korda, V.M. Mishchenko, R.P. Slabospitsky // Вопросы атомной науки и техники. — 2002. — № 2. — С. 33-35. — Бібліогр.: 12 назв. — англ. |
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Kachan, A.S. Vodin, A.N. Korda, V.Yu. Korda, L.P. Mishchenko, V.M. Slabospitsky, R.P. 2015-04-11T19:43:58Z 2015-04-11T19:43:58Z 2002 γ-decay of resonance-like structure observed in ³⁰Si(p,γ)³¹p reaction / A.S. Kachan, A.N. Vodin, V.Yu. Korda, L.P. Korda, V.M. Mishchenko, R.P. Slabospitsky // Вопросы атомной науки и техники. — 2002. — № 2. — С. 33-35. — Бібліогр.: 12 назв. — англ. 1562-6016 PACS: 25.40.Lw, 25.40.Ny, 27.30+i, 24.30.Cs, 23.20.-g https://nasplib.isofts.kiev.ua/handle/123456789/80109 γ-Decay of a resonance-like structure observed in the reaction ³⁰Si(p,γ)³¹p in the energy region Ep=1.4-2.7 MeV of accelerated protons is studied. The M1 resonance built on the ground state of ³¹P is identified. The position of the M1 resonance is explained taking into account pairing forces. en Національний науковий центр «Харківський фізико-технічний інститут» НАН України Вопросы атомной науки и техники Nuclear reactions γ-decay of resonance-like structure observed in ³⁰Si(p,γ)³¹p reaction γ-распад резонансоподобной структуры, наблюдаемой в реакции ³⁰Si(p,γ)³¹p Article published earlier |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine |
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γ-decay of resonance-like structure observed in ³⁰Si(p,γ)³¹p reaction |
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γ-decay of resonance-like structure observed in ³⁰Si(p,γ)³¹p reaction Kachan, A.S. Vodin, A.N. Korda, V.Yu. Korda, L.P. Mishchenko, V.M. Slabospitsky, R.P. Nuclear reactions |
| title_short |
γ-decay of resonance-like structure observed in ³⁰Si(p,γ)³¹p reaction |
| title_full |
γ-decay of resonance-like structure observed in ³⁰Si(p,γ)³¹p reaction |
| title_fullStr |
γ-decay of resonance-like structure observed in ³⁰Si(p,γ)³¹p reaction |
| title_full_unstemmed |
γ-decay of resonance-like structure observed in ³⁰Si(p,γ)³¹p reaction |
| title_sort |
γ-decay of resonance-like structure observed in ³⁰si(p,γ)³¹p reaction |
| author |
Kachan, A.S. Vodin, A.N. Korda, V.Yu. Korda, L.P. Mishchenko, V.M. Slabospitsky, R.P. |
| author_facet |
Kachan, A.S. Vodin, A.N. Korda, V.Yu. Korda, L.P. Mishchenko, V.M. Slabospitsky, R.P. |
| topic |
Nuclear reactions |
| topic_facet |
Nuclear reactions |
| publishDate |
2002 |
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English |
| container_title |
Вопросы атомной науки и техники |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Article |
| title_alt |
γ-распад резонансоподобной структуры, наблюдаемой в реакции ³⁰Si(p,γ)³¹p |
| description |
γ-Decay of a resonance-like structure observed in the reaction ³⁰Si(p,γ)³¹p in the energy region Ep=1.4-2.7 MeV of accelerated protons is studied. The M1 resonance built on the ground state of ³¹P is identified. The position of the M1 resonance is explained taking into account pairing forces.
|
| issn |
1562-6016 |
| url |
https://nasplib.isofts.kiev.ua/handle/123456789/80109 |
| citation_txt |
γ-decay of resonance-like structure observed in ³⁰Si(p,γ)³¹p reaction / A.S. Kachan, A.N. Vodin, V.Yu. Korda, L.P. Korda, V.M. Mishchenko, R.P. Slabospitsky // Вопросы атомной науки и техники. — 2002. — № 2. — С. 33-35. — Бібліогр.: 12 назв. — англ. |
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| first_indexed |
2025-11-26T20:09:44Z |
| last_indexed |
2025-11-26T20:09:44Z |
| _version_ |
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| fulltext |
γ-DECAY OF RESONANCE-LIKE STRUCTURE
OBSERVED IN 30Si(p,γ)31P REACTION
A.S. Kachan1, A.N. Vodin1, V.Yu. Korda2, L.P. Korda1, V.M. Mishchenko1, R.P. Slabospitsky1
1National Scientific Centre “Kharkov Institute of Physics and Technology”, Kharkov, Ukraine
e-mail: kachan@kipt.kharkov.ua
2Scientific and Technological Centre of Electrophysics
National Academy of Sciences of Ukraine, Kharkov, Ukraine
e-mail: ipct@pem.kharkov.ua
γ-Decay of a resonance-like structure observed in the reaction 30Si(p,γ)31P in the energy region Ep=1.4-2.7 MeV
of accelerated protons is studied. The M1 resonance built on the ground state of 31P is identified. The position of the
M1 resonance is explained taking into account pairing forces.
PACS: 25.40.Lw, 25.40.Ny, 27.30+i, 24.30.Cs, 23.20.-g
1. INTRODUCTION
Later [1,2], having studied γ-decays of the
resonance-like structures (RLS) observed in the
reactions of radiative capture of protons by 21Ne, 25Mg,
29Si and 33S nuclei, we identified the magnetic dipole
resonance (MDR) built on the ground states of the odd-
odd 4N+np 22Na, 26Al and 30P nuclei and performed the
search for MDR in 34Cl nuclei. The position of the
centre-of-gravity (COG) of MDR (Е0=ΣkЕkВk(М1)/ΣkBk
(М1)) in these nuclei differs from that in 4N-nuclei by
3 MeV, on average, and, in fact, does not depend on
mass number A (it is usually thought that this
dependence must be of the form Ec.g=40⋅A-1/3). We
explained this new fact by assuming the existence of the
triplet neutron-proton pairing. The joint analysis of the
MDR total strength and position in 4N, 4N+2n and
4N+np nuclei shows that the formation of MDR in these
nuclei is strongly influenced by the valence nucleons
and that the MDR COG is determined not only by the
energy of spin-orbit splitting but also by the strengths of
both the nn(pp)-pairing and the np-pairing as well. The
similar analysis for odd nuclei shows that the position of
MDR COG in these nuclei depends on the state of odd
particle: d5/2 or d3/2. The position of MDR COG in the
first case must be in the region of excitation energies of
5-6 MeV. In the second case, the nn- or pp-pairs from
d5/2-subshell can participate in the formation of MDR
and the position of MDR COG in odd nucleus will then
slightly differ from that position in even nuclei. Up to
now, this conclusion is confirmed by our studies [3-6]
(MDR COG in 35Cl and 37Cl are situated in the region of
excitation energies of 9-10 MeV, while the same region
for 23Na and 27Al is 5-6 MeV). With the aim of
confirming and further developing the model vision of
the nature of MDR and its mechanisms, we need new
experimental data on the position, fine structure and
total strength of MDR in those even and odd nuclei
where MDR is not observed yet.
2. EXPERIMENTAL DATA AND DISCUSSION
Up to date, wide experimental information on resonance
states in 31P is collected via the reaction of radiative
capture of 0.5-4.0 MeV protons by 30Si [7-10]. But the
data for several resonance states are insufficient. For
instance, the angular distributions of the radiatively
captured protons were not measured for the resonance
states having intensive transitions into ground state with
Ep=1482, 2350 and 2505 keV. Thus, the multipole
mixing coefficients of γ-radiation are unknown for γ-
transitions from these states. In the context, we have
carried out the set of experiments associated with
identification and determination of the COG position,
fine structure and total strength of MDR in 31P via
measuring the excitation function of 30Si(p,γ) 31P
reaction in the proton energy region of Ep=1.4-2.7 MeV
(Fig. 1). The measurements were held on the
electrostatic accelerator of National Scientific Centre
“Kharkov Institute of Physics and Technology”. The γ-
output with Eγ>2.6 MeV were measured via the 150×
100 mm2 NaI(Tl) detector positioned at a distance of
5 cm from the target at an angle of 55° with respect to
the proton beam direction (to remove the dependence of
γ-output on angle). The resonance strength
(S=(2J+1)ГрГγ/Г) were determined by comparing the
square under the resonance curve for the resonances
under study with the same square for the resonance at
Ep=1880 keV. The strength of the latter is well known
and equal to 4.8±0.7 eV [7]. We found RLS (Fig. 2a)
similar to those ones we observed later in 23Na, 27Al, 35Cl
and 37Cl [3-6]. However, COG (Е0=ΣkЕkSk/ΣkSk) of this
RLS being equal to 10.4±0.5 MeV were situated in the
same region of excitation energy as for 37Cl and 1 MeV
higher the excitation energy for 35Cl. In all preceding
cases [1-6] RLS had complicated structures, comprising
the states belonged both to the M1-resonance on the
ground state and to the one built on the excited states.
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2002, № 2.
Series: Nuclear Physics Investigations (40), p. 33-35. 33
1400 1500 1800 1900 2000 2100 2200 2300 2400 2500 2600
0
4000
8000
12000
2
5
0
5
2
3
5
0
1
8
8
0
30S i(p,γ)31P
1
4
8
2
N γ
Ep, keV
Fig. 1. Excitation function of the reaction 30Si(p,γ) 31P in the region of proton energies Ер=1400-2700 keV
Only in the case of 34Cl RLS COG was determined
by the states of M1-resonance on the excited state.
The final conclusion on the nature of RLS observed
in 31P can be made after the determination of all
quantum characteristics of the resonance states
comprising this RLS and the study of their γ-decays.
The spectra of photons were measured with a Ge(Li)
detector of the volume of 60 cm3. The resolution of the
detector for Eγ=1332 keV was 4 keV. The detector was
positioned at a distance of 7 cm from a 20 µg/cm2-thick
target (30Si).
Experimental angular distributions of photons from the reaction 30Si(p,γ)31P
№ E
р
, кeV E
f
-E
i
, кeV a
2
±
∆а
2
a
4
±
∆а
4
a
6
±
∆а
6
χ
2
min
1 1482 8730 → 0 0.25±0.12 -0.14±0.12 -0.009±0.13 0.003
2 → 2234 -0.40±0.10 0.05 ±0.10 -0.11 ±0.09 1.2
3 → 3134 0.38±0.09 -0.05±0.08 0.06 ±0.09 0.27
4 → 3295 0.42±0.15 0.41 ±0.15 0.14 ±0.17 0.15
5 → 5015 -0.32±0.12 -0.11±0.12 -0.03 ±0.10 0.07
6 2350 9571 → 0 0.01 ±0.11 -0.04±0.12 0.08 ±0.13 1.9
7 → 1266 -0.12±0.12 0.09 ±0.13 0.07 ±0.12 0.0005
8 → 3134 0.09 ±0.11 0.12 ±0.13 0.15 ±0.14 0.0003
9 → 1727 -0.35±0.13 0.12 ±0.12 -0.11±0.12 0.01
10 2505 9721 → 0 -0.09±0.14 -0.09±0.15 0.12 ±0.16 0.04
11 → 1266 -0.39±0.14 0.04 ±0.13 0.005±0.14 0.21
12 → 2234 0.29 ±0.12 0.07 ±0.12 0.13 ±0.14 1.1
13 → 3506 -0.23±0.26 0.24 ±0.28 -0.21±0.30 1.45
14 → 4261 -0.04 ±0.11 0.35 ±0.13 -0.10±0.12 0.38
The target oriented at an angle of 45° with respect to the
proton-beam direction was at the centre of rotation. The
measurements were carried out at angles of 0°, 60°, 30°,
90° and 45°. Corrections taking into account finite
dimensions of the detector were borrowed from the
tables presented in [11]. A scintillation detector
involving a NaI(Tl) crystal of dimensions 150×100 mm2
served as a monitor. The same detector was also used to
measure the excitation function of the reaction 30Si(p,γ)
31P. The results represented as the coefficients (ak) in the
expansion in Legendre polynomials are displayed in the
Table. To find the coefficients ak, we constructed the
least-square fit to the experimental data proceeding from
the expression W(θ)=A0[1+ а2Р2(cosθ)+а4Р4(cosθ)
+а6Р6(cosθ)]. A further analysis of the angular
distributions involved determining the spins of
resonance states and the multipole-mixing coefficients
for γ-rays (δ) by minimizing the quantity
( ) ( )
( )
⋅∑
−
=
n
2
n
nn02
θ
exp
ΔW
θ
exp
WθtheorWA
χ (1)
where Wtheor(θ) = ΣkQkρk0Fk(J1,J2,L,δ)Pk is the theoretical
angular distribution of photons for the transition
between the initial and final states with spins J1 and J2,
Wexp(θ) and ∆Wexp(θ) are the experimental data and the
34
corresponding statistical uncertainty, А0 is the
normalization constant, Qк is a coefficient accounting
finite dimensions of the detector, ρk0 is an element of the
statistical tensor, n is the number of experimental points
(angles). The quantity χ2 was minimized with the help of
the software created on the basis of refined genetic
algorithm [12]. The fitting procedure for odd nuclei
differed from that for even nuclei: for odd nuclei the
parameters of the statistical tensor were calculated and
the multipole-mixing coefficient (δ) remained the only
fitting parameter. The spin values of resonances at hand
were defined, in general, via analysis of transitions to
the 31P ground state (Jπ=1/2+). The parities were defined
based on the comparison of probabilities of
electromagnetic transitions of different multipolarity
with recommended upper limits of the given values [7].
The reduced probability of γ-transition B(M1) was
calculated using the expression
B(M1)↑=86,6bS(eV)/((2J+1)E3
γ (MeV)), (2)
where b is the branching coefficient of γ-transition, J is
the spin of initial state, Eγ is the energy of γ-transition.
Figs. 2b and 2c show estimate of the upper limit of
В(М1) for the states for which not all quantum
characteristics are known.
0 2 4 6 8 10 12
0,0
0,5
1,0
1,5 cR 1266
0
2
4
b
↑
↑
B
(M
1
)
,
1
0-
1 µ
N
2
Ep , MeV
R 0
0
10
20
a30Si(p,γ )31P
QpγS
,
eV
Fig. 2. γ-decay of a resonance-like structure from
the reaction 30Si(p,γ)31P: a - resonance strength; b -
reduced probabilities of the γ-transitions from the 31P
ground state; c - reduced probabilities of the γ-
transitions from the 31P first excited state
(Е*=1266 keV). For the sake of convenience only those
resonance states for which S > 1 eV are presented
These values do not exceed 0,1 µ2
N (background
level for transitions to the ground state) and 0,05 µ2
N
(background level for transitions to the first excited
state). Derived probability distributions for magnetic
dipole γ-transitions allow concluding that the resonances
comprising RLS belong to the states of M1-resonance
built on the first excited state of 31P (Fig. 2c). The
greatest probability of M1-transition from the bound
state 7141 keV (Jπ=1/2+) to the ground one is equal to
0,47 µ2
N. This value is found accounting for the mean
half-time of the state 7141 keV [9]. The COG position
of MDR on 31P ground state (Fig. 2b) is equal to 8.5±
0.3 MeV and is situated in the region of excitation
energies which is expected for nuclei with closed d5/2-
subshell. This experimental fact confirms that the
formation of M1-resonance in 31P is affected by the
magnitude of nn(pp)-pairing in d5/2-subshell. The total
strength of MDR (SМ1
EW=ΣkЕкВк(М1)) on the ground
state being equal to 8 MeVµ2
N substantially differs from
that value for 35Cl. This fact is probably due to different
numbers of particles participating in the transition
between the spin-orbit partners. Our investigations show
that we have identified M1-resonance on the ground and
first excited states in 31P.
REFERENCES
1. A.S. Kachan, B.A. Nemashkalo,
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PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY. 2002, № 2.
Series: Nuclear Physics Investigations (40), p.
35
PACS: 25.40.Lw, 25.40.Ny, 27.30+i, 24.30.Cs, 23.20.-g
REFERENCES
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