The decay of ¹⁹¹Pt
The energy difference for γ268 and γ295 lines was measured with gamma-spectrometer. The γ268 keV transition is excited in the ¹⁹¹Pt decay, while another transition, the energy of which is known up to a high precision, accompanies the ¹⁹²Ir decay. A measured energy value of the 3/2- → 7/2- transition...
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irk-123456789-1112762017-01-10T03:02:21Z The decay of ¹⁹¹Pt Lashko, A.P. Ядерная физика и элементарные частицы The energy difference for γ268 and γ295 lines was measured with gamma-spectrometer. The γ268 keV transition is excited in the ¹⁹¹Pt decay, while another transition, the energy of which is known up to a high precision, accompanies the ¹⁹²Ir decay. A measured energy value of the 3/2- → 7/2- transitions (268 keV ), along with the data from our previous work, allowed us to perform a high-precision calculation of energy levels in ¹⁹¹Ir and energies of γ-rays deexciting these levels. На гамма-спектрометрі поміряли різницю енергій ліній γ268 та γ295 кеВ. Перехід γ268 кеВ збуджується при розпаді ¹⁹¹Pt, а другий, енергія якого відома з високою точністю, супроводжує розпад ¹⁹²Ir. Отримане значення енергії переходу 3/2- → 7/2- 268 кеВ дозволило, разом з даними нашої попередньої роботи, розрахувати з високою точністю енергії рівнів ¹⁹¹Ir та енергії розряджаючих їх γ-променів. На γ-спектрометре измерена разность энергий линий γ268 и γ295 кэВ. Переход γ268 кэВ возбуждается при распаде ¹⁹¹Pt, а второй, энергия которого известна с высокой точностью, сопровождает распад ¹⁹²Ir. Измеренное значение энергии перехода 3/2- → 7/2- 268 кэВ позволило, совместно с данными нашей предыдущей работы, рассчитать с высокой точностью энергии уровней ¹⁹¹Ir и энергии разряжающих их γ-лучей. 2009 Article The decay of ¹⁹¹Pt / A.P. Lashko // Вопросы атомной науки и техники. — 2009. — № 3. — С. 33-37. — Бібліогр.: 15 назв. — англ. 1562-6016 PACS: 23.20.Lv, 27.80.+w, 29.30.Kv http://dspace.nbuv.gov.ua/handle/123456789/111276 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 Lashko, A.P. The decay of ¹⁹¹Pt Вопросы атомной науки и техники |
| description |
The energy difference for γ268 and γ295 lines was measured with gamma-spectrometer. The γ268 keV transition is excited in the ¹⁹¹Pt decay, while another transition, the energy of which is known up to a high precision, accompanies the ¹⁹²Ir decay. A measured energy value of the 3/2- → 7/2- transitions (268 keV ), along with the data from our previous work, allowed us to perform a high-precision calculation of energy levels in ¹⁹¹Ir and energies of γ-rays deexciting these levels. |
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Article |
| author |
Lashko, A.P. |
| author_facet |
Lashko, A.P. |
| author_sort |
Lashko, A.P. |
| title |
The decay of ¹⁹¹Pt |
| title_short |
The decay of ¹⁹¹Pt |
| title_full |
The decay of ¹⁹¹Pt |
| title_fullStr |
The decay of ¹⁹¹Pt |
| title_full_unstemmed |
The decay of ¹⁹¹Pt |
| title_sort |
decay of ¹⁹¹pt |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2009 |
| topic_facet |
Ядерная физика и элементарные частицы |
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http://dspace.nbuv.gov.ua/handle/123456789/111276 |
| citation_txt |
The decay of ¹⁹¹Pt / A.P. Lashko // Вопросы атомной науки и техники. — 2009. — № 3. — С. 33-37. — Бібліогр.: 15 назв. — англ. |
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Вопросы атомной науки и техники |
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AT lashkoap thedecayof191pt AT lashkoap decayof191pt |
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| fulltext |
THE DECAY OF 191Pt
A.P. Lashko∗
Institute for Nuclear Research, National Academy of Sciences of Ukraine, 03680, Kiev, Ukraine
(Received March 17, 2008)
The energy difference for γ268 and γ295 lines was measured with gamma-spectrometer. The γ268 keV transition is
excited in the 191Pt decay, while another transition, the energy of which is known up to a high precision, accompanies
the 192Ir decay. A measured energy value of the 3/2− → 7/2− transitions (268 keV ), along with the data from our
previous work, allowed us to perform a high-precision calculation of energy levels in 191Ir and energies of γ-rays
deexciting these levels..
PACS: 23.20.Lv, 27.80.+w, 29.30.Kv
1. INTRODUCTION
Decay of the 191Pt (Iπ = 3/2−, T1/2 = 2.8 days) oc-
curs by the electron capture to 16 levels of the 191Ir,
excluding the 11/2− isomeric state. In the process 50
γ-transitions in the energy range 42 to 935 keV are
excited. According to the recent review [1], energies
of these transitions are measured, at best, to within
several tens of electron-volts. The data on energies of
excited states of atomic nuclei known with an accu-
racy of several electron-volts and higher become in-
creasingly required today. The evolution of technique
of high-precision measurement of γ-ray energy based
on the semiconductor spectrometers, along with the
essential extension of nuclear-spectroscopic standards
mesh, have provided great scope for all-inclusive mea-
surements of energies of excited nuclear states popu-
lated in the decay of sources with more or less notice-
able life-time. Isotope 191Pt appeared to be an ap-
propriate object for such purpose. Our long-standing
researches [2-5] allowed high-precision determination
of the energies of 9 levels of the 191Ir and the ener-
gies of 36 γ-quanta accompanying the decay of 191Pt.
Until recently, energies of 7/2− level (390 keV ) and
11/2− level (171 keV ) can not be determined with
such an accuracy. We failed to measure energies of
any transitions that might relate these levels with
others. To this end, either the energy of the very weak
(6.4× 10−5%) 41 keV γ-transition or the energies of
the 268.0 + 268.8 keV doublet should be measured.
This problem was finally resolved in the present pa-
per.
2. EXPERIMENTAL TECHNIQUE
The number of levels exciting in the radioactive
decay of mother nucleus is generally less than the
number of γ-rays deexciting these levels. It is not
necessary for all γ-rays to be measured, in order to
get information about their energies. The reference
nuclear transition method can be used instead. Ap-
plication of this method allows one to essentially re-
duce laboriousness of the experiments.
Procedure of determination of energies of excited
nuclear states and γ-rays deexciting these states by
the reference nuclear transition method reduces to
the following basis stages:
1) the most appropriate for measurement single
intense γ-lines are chosen as reference lines;
2) the set of references is selected from the list
of recommended energy standards for nuclear spec-
troscopy. In order to minimize the errors arising from
an ambiguity of calibration curve, it is necessary to
select such references that would be close to the mea-
sured γ-line while still being easily resolved in the
spectrum;
3) the mixed radioactive source of required com-
position is prepared with desired ratios of specific ac-
tivities of radionuclides entering into the source. For
statistical error (uncertainty in determination of dis-
tance between lines) to be minimized, the reference
and measured line should have close intensities;
4) to minimize possible systematic errors, mea-
surements are performed by series on different de-
tectors, at various geometries, different amplification
coefficients and different quantization levels of the in-
put signal on amplitude-digital converters;
5) energies of reference transitions are deter-
mined;
6) to calculate energies of levels, a set of linear
equations is derived and then it is solved with the
least-squares procedure;
7) energies of all γ-quanta accompanying the de-
cay of mother nucleus are calculated on basis of the
obtained data.
The technique of such measurements and the
problems concerning preparation of a mixed radioac-
tive source of optimal composition were reported in
detail in [6-7].
∗Corresponding author E-mail address: lashkoa@kinr.kiev.ua
PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2009, N3.
Series: Nuclear Physics Investigations (51), p.33-37.
33
The energy difference for γ267 and γ295 lines
was measured with gamma-spectrometer, which com-
prises two horizontal detectors made from high-purity
germanium (coaxial GEM−40195 with 1.73 keV res-
olution for γ1332-line of 60Co and planar GLP −
36360/13 with 580 eV resolution for γ122-line of
57Co) and multichannel ORTEC buffer 919 SPEC-
TRUM MASTER. The γ267 keV transition is excited
in the 191Pt decay, while another transition, the en-
ergy of which is known up to a high precision, accom-
panies the 192Ir decay. To prepare a mixed radioac-
tive source of required composition, the 191Pt was ob-
tained in (n, γ) reaction under irradiation of enriched
platinum (190Pt isotope content is 0, 8%) with re-
search reactor WWR-M. The 192Ir (T1/2 = 74 days)
was also produced in (n, γ) reaction under irradiation
of enriched iridium (191Ir isotope content is 94%) by
slow neutrons.
The functional dependence of the energy calibra-
tion of the γ-spectrometer was investigated in detail.
It was established that the deviation from linearity
does not exceed 3 × 10−5 for the energy range from
84 to 604 keV . To minimize possible systematic er-
rors, we performed a series of measurements using
sources with different ratios of specific activities of
191Pt, 182Ta, and 192Ir, at different gains and chan-
nel widths of an amplitude digital converter (4096
and 8192 quantization levels of the input signal). 18
series of measurements were performed in all. The
spectra were also analyzed with respect to the half-
decay period to exclude possible impurities of other
radionuclides. To the same end, we determined with
high accuracy the relative intensities of the γ-lines
accompanying decay of 191Pt. The results of these
measurements are shown in Table 1. Good agree-
ment with the data of other researchers is observed,
which confirms the absence of ”foreign” γ-lines in the
spectral regions of interest.
Table 1. Intensities I of the γ-lines from the decay of 191Pt for the energy range
above 150 keV in the relative units
Energy, keV I, Our data I, Compilation [8] Energy, keV I, Our data I, Compilation [8]
172.2 39.8± 1.2 44± 2 479.9 0.71± 0.05 0.71± 0.07
179.0 11.2± 0.3 12.7± 0.6 494.7 0.77± 0.03 0.75± 0.07
187.7 4.69± 0.14 5.2± 0.3 538.9 180± 4 171± 9
219.7 10.1± 0.3 10.3± 0.5 541.7 5.00± 0.15 4.6± 0.5
221.8 1.80± 0.06 1.45± 0.15 568.9 0.69± 0.04 0.66± 0.05
223.7 1.54± 0.05 1.40± 0.15 576.4 1.56± 0.06 1.47± 0.11
268.0 9.2± 0.4 9.7± 1.0 583.6 1.02± 0.05 0.95± 0.07
268.8 19.8± 0.9 20.6± 2.0 618.4 0.17± 0.04 0.11± 0.04
351.2 41.8± 1.0 42± 2 624.1 19.1± 0.6 17.6± 0.9
359.9 74.2± 1.8 75± 4 633.1 0.40± 0.07 0.30± 0.03
396.6 0.21± 0.05 0.13± 0.04 658.9 0.20± 0.04 0.19± 0.02
409.5 100 100± 5 680.2 0.096± 0.009 0.086± 0.017
445.1 0.76± 0.05 0.68± 0.07 762.6 0.169± 0.011 0.15± 0.02
456.5 42.3± 1.0 42± 2 806.4 0.068± 0.020 0.047± 0.009
458.6 0.78± 0.08 0.54± 0.10 935.3 0.143± 0.009 0.15± 0.02
3. RESULTS AND DISCUSSION
The g-spectra were treated using the programs devel-
oped by us [9–11] based on the method of fitting the
”instrumental” peak into the spectrum region of in-
terest. This method allows a high-precision measure-
ment of energies and intensities of the components
in the case of lines of asymmetric shape and overlap-
ping lines. This technique implies measuring a single
gamma peak from the obtained spectrum (or, if such
a peak is absent, specially measured single gamma
peak with the shape similar to that of the line in
the studied region of spectrum) with high statistical
accuracy. After subtraction of the background, it is
described by the multiple cubic-spline interpolation,
and it is used as ”instrumental”, i.e. defines the ex-
perimental peak shape for the subsequent analysis
by the least-squares method. The experiment was a
considerable challenge due to the fact that the γ267
line is not completely resolved in the spectrum with
the γ268 line (see Fig.1).
Fig.1. Part of the γ-spectrum in the energy region
260...300 keV from the decay of 191Pt, measured
with the HPGe-detector GLP − 36360/13
34
Special care must be used to control an accuracy of
component decomposition of the γ267 + γ268 dou-
blet. Intensities of these two γ-lines are known to
within 5%. Control over the change in component
intensities still did not ensure correctness of determi-
nation of γ-line energies with an accuracy of several
electron-volts. We made use of the fact that the γ268
energy was previously determined with a precision of
1.7 eV as the energy difference of the 5/2+ 351 keV
and 1/2+ 82 keV levels, between which this transi-
tion occurs [5]. Simultaneously with the component
decomposition of the doublet the energy difference
for γ267, γ268 keV lines of 191Pt and γ295 keV line
of 192Ir was determined. Requirement for the devi-
ation of the γ268 energy from measured value not
to exceed 3σ served as a criterion of accuracy of
γ-spectrum fitting procedure. First, the energy dif-
ference for γ267 line of 191Pt and γ295 line of 192Ir
were determined as a weighted mean from the results
of all measurements and then the transition energies
were found. The measurement results are in good
agreement with each other. Taking into account that
the energy of the recoil nucleus for γ267 of 191Pt is
0.20 eV , we obtained the value 267952.8± 1.8 eV for
the transition energy. In the same way we previously
determined the energies of 19 transitions from the
decay of 191Pt [3-5]. Their location in the 191Pt
decay scheme is shown in Fig.2.
Fig.2. Fragment of the schematic diagram of 191Pt decay
Using the data on the transition energies and
the Ritz rule for cascade transitions (E1 + E2 = E3,
where E3 is the energy of the closing direct tran-
sition between the boundary levels), we formulated
the system of linear approximate equations of differ-
ent weight to calculate the level energies:
a1x + b1y + ... + m1ν = t1 ±∆t1 ,
a2x + b2y + ... + m2ν = t2 ±∆t2 ,
................................. = ...............
aNx + bNy + ... + mNν = tN ±∆tN , (1)
where a, b,. . . , m are specified numbers (generally
they are equal to ±1 or zero), t and ∆t are the tran-
sition energies and their errors; x, y, . . . , ν are un-
known level energies. Since N is larger than the num-
ber of unknowns, the system was solved by the least-
squares method [12]; i.e., we determined such values
of unknowns at which the sum
N∑
i=1
pi(ti − aix− biy − ...−miν)2 , (2)
(pi = (∆ti)−2; i = 1, 2, ..., N) was minimum. The er-
rors of all parameters can be obtained using the par-
abolic dependence χ2 = χ2(αi), where αi(x, y, ..., ν)
is the parameter studied. In this case, all other pa-
rameters are fixed and correspond to optimal values.
The standard errors ∆α are determined using the re-
lation:
χ2(αopt
i ±∆αi) = χ2
min + 1 , (3)
where αopt
i is the optimal value of the parameter ai,
which minimizes χ2. After determination of the en-
ergies of nuclear excited states, it was quite easy
to calculate the γ-transition energies between these
states. The results of the calculations, along with
the weighted mean values from compilation [1], are
shown in Table 2. We determined the energies of 11
levels of 191Ir and the energies of 39 γ-quanta accom-
panying decay of 191Pt with an accuracy exceeding
the known values by an order of magnitude. Most
of them completely correspond to the requirements
imposed on the fourth-order energy normals.
35
Table 2. Energies of the 191Ir levels and γ-ray photons excited in 191Pt decay:
present work and compilation [1]
Energy levels, eV γ-rays energy, eV Energy levels, eV γ-rays energy, eV
[1] [1]
82427.0± 0.9 82427.0± 0.9 82405± 7 82398± 7
129431.9± 1.0 47004.9± 1.4 129396± 7 −
129431.9± 1.0 129400± 7
171296± 6 41864± 6 171320± 30 41930± 30
178977.3± 0.9 49545.4± 1.4 178934± 10 49590± 30
96550.3± 1.3 965517± 9
178977.2± 0.9 178960± 30
351187.5± 1.4 172210.1± 1.7 351139± 16 172190± 20
221755.5± 1.7 221740± 80
268760.3± 1.7 268710± 80
351187.1± 1.4 351170± 30
390968± 4 219672± 5 390970± 50 219650± 50
538904.2± 0.9 187716.6± 1.7 538839± 15 187690± 40
359926.5± 1.3 359880± 30
409471.8± 1.4 409440± 20
456476.6± 1.3 456470± 50
538903.4± 0.9 538870± 50
624098± 5 85194± 5 624060± 40 85150± 80
445120± 5 445130± 80
494666± 5 494690± 70
541671± 5 541640± 100
624097± 5 624060± 60
658920.5± 3.2 267952.8± 1.8 658870± 50 267920± 80
307732.7± 3.5 308000± 1000
479942.5± 3.3 479950± 70
576492.6± 3.3 576460± 80
658919.3± 3.2 658750± 150
747833± 6 208929± 6 747780± 70 208960± 150
396645± 6 396700± 200
568855± 6 568810± 80
618400± 6 618700± 400
747833± 6 748000± 200
762580.3± 2.9 138482± 6 762520± 50 138200± 200
223676.0± 3.0 223670± 80
411392.3± 3.2 411000± 1000
583602.0± 3.0 583610± 80
633147.3± 3.1 633180± 100
680152.0± 3.0 680000± 200
762578.7± 2.9 762600± 150
4. CONCLUSION
At present, the list of the recommended energy
standards for nuclear spectroscopy includes about
240 γ-rays covering the energy range from 24 up to
4806 keV [13, 14]. For all of them the relative error
in energy definition does not exceed 10−5.
The reference line should be close to the mea-
sured γ-line for precision determination of transi-
tion energies. This allows minimization of the er-
rors arising due to an ambiguity of calibration curve
of the spectrometer. Therefore, in deciding on ref-
erence γ-lines, the presence of convenient nuclear-
spectroscopic standards in a given part of spectrum
is of no small importance.
191Pt isotope is sufficiently produced in the slow-
neutron reaction (n, γ) (activation cross-section is
about 800 barns [15]). Only the need for using plat-
inum enriched by 190Pt isotope is a problem, because
content of this isotope in natural isotopic mixture
does not exceed 0, 013%. However, the large number
of sufficiently intense γ-lines, which can be used as
references in energy range from 50 to 760 keV , makes
up for this inconvenience.
36
References
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РАСПАД 191Pt
А.П. Лашко
На γ-спектрометре измерена разность энергий линий γ268 и γ295 кэВ. Переход γ268 кэВ возбуждается
при распаде 191Pt, а второй, энергия которого известна с высокой точностью, сопровождает распад
192Ir. Измеренное значение энергии перехода 3/2− → 7/2− 268 кэВ позволило, совместно с данными
нашей предыдущей работы, рассчитать с высокой точностью энергии уровней 191Ir и энергии разря-
жающих их γ-лучей.
РОЗПАД 191Pt
А.П. Лашко
На гамма-спектрометрi помiряли рiзницю енергiй лiнiй γ268 та γ295 кеВ. Перехiд γ268 кеВ збуджується
при розпадi 191Pt, а другий, енергiя якого вiдома з високою точнiстю, супроводжує розпад 192Ir. От-
римане значення енергiї переходу 3/2− → 7/2− 268 кеВ дозволило, разом з даними нашої попередньої
роботи, розрахувати з високою точнiстю енергiї рiвнiв 191Ir та енергiї розряджаючих їх γ-променiв.
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