The study of ¹⁷⁷mLu decay
High-precision measurements of the relative γ-ray intensities from the decay of ¹⁷⁷mLu were performed by means of a γ-spectrometer. The data were used to determine the internal conversion coefficient (ICC) for the K-forbidden E1-transition with the energy of 55 keV in ¹⁷⁷Hf. High value of the hindra...
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
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irk-123456789-1118582017-01-16T03:02:45Z The study of ¹⁷⁷mLu decay Lashko, A.P. Lashko, T.N. Ядерная физика и элементарные частицы High-precision measurements of the relative γ-ray intensities from the decay of ¹⁷⁷mLu were performed by means of a γ-spectrometer. The data were used to determine the internal conversion coefficient (ICC) for the K-forbidden E1-transition with the energy of 55 keV in ¹⁷⁷Hf. High value of the hindrance factor for the γ-radiation leads to anomalies in the ICC which are observed in the experiment. The discrepancy between experimental and theoretical values of ICC cannot be explained by admixtures of different multipolarities with the same parity. Such variance can be eliminated only by assuming the presence of intranuclear conversion. На γ-спектрометрi з високою точнiстю помiрянi вiдноснi iнтенсивностi γ-променiв, якi збуджуються при розпадi ¹⁷⁷mLu. Цi данi були використанi для визначення коефiцiєнта внутрiшньої конверсiї (КВК)-забороненого E1-переходу з енергiєю 55 кеВ у ¹⁷⁷Hf. Високий фактор заборони γ-випромiнювання призводить до аномалiй в КВК, якiй спостерiгаються в експериментi. Розбiжностi мiж теоретичними та експериментальними значеннями КВК неможливо пояснити домiшками iнших мультипольностей тiєї ж парностi. Їх можна узгодити лише припустивши наявнiсть внутрiшньоядерної конверсiї. На γ-спектрометре с высокой точностью измерены относительные интенсивности γ-лучей, возбуждающиеся при распаде ¹⁷⁷mLu. Эти данные были использованы для определения коэффициента внутренней конверсии (КВК) -запрещенного E1-перехода с энергией 55 кэВ в ¹⁷⁷Hf. Высокий фактор запрета γ-излучения приводит к аномалиям в КВК, которые и наблюдаются в эксперименте. Расхождения между теоретическими и экспериментальными значениями КВК нельзя объяснить примесями других мультипольностей той же четности. Их можно согласовать, только предположив наличие внутриядерной конверсии. 2013 Article The study of ¹⁷⁷mLu decay / A.P. Lashko, T.N. Lashko // Вопросы атомной науки и техники. — 2013. — № 3. — С. 129-135. — Бібліогр.: 29 назв. — англ. 1562-6016 PACS: 23.20.Lv, 23.20.Nx, 27.70.+q http://dspace.nbuv.gov.ua/handle/123456789/111858 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. Lashko, T.N. The study of ¹⁷⁷mLu decay Вопросы атомной науки и техники |
| description |
High-precision measurements of the relative γ-ray intensities from the decay of ¹⁷⁷mLu were performed by means of a γ-spectrometer. The data were used to determine the internal conversion coefficient (ICC) for the K-forbidden E1-transition with the energy of 55 keV in ¹⁷⁷Hf. High value of the hindrance factor for the γ-radiation leads to anomalies in the ICC which are observed in the experiment. The discrepancy between experimental and theoretical values of ICC cannot be explained by admixtures of different multipolarities with the same parity. Such variance can be eliminated only by assuming the presence of intranuclear conversion. |
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Article |
| author |
Lashko, A.P. Lashko, T.N. |
| author_facet |
Lashko, A.P. Lashko, T.N. |
| author_sort |
Lashko, A.P. |
| title |
The study of ¹⁷⁷mLu decay |
| title_short |
The study of ¹⁷⁷mLu decay |
| title_full |
The study of ¹⁷⁷mLu decay |
| title_fullStr |
The study of ¹⁷⁷mLu decay |
| title_full_unstemmed |
The study of ¹⁷⁷mLu decay |
| title_sort |
study of ¹⁷⁷mlu decay |
| publisher |
Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2013 |
| topic_facet |
Ядерная физика и элементарные частицы |
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http://dspace.nbuv.gov.ua/handle/123456789/111858 |
| citation_txt |
The study of ¹⁷⁷mLu decay / A.P. Lashko, T.N. Lashko // Вопросы атомной науки и техники. — 2013. — № 3. — С. 129-135. — Бібліогр.: 29 назв. — англ. |
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Вопросы атомной науки и техники |
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| fulltext |
THE STUDY OF 177mLu DECAY
A.P. Lashko and T.N. Lashko∗
Institute for Nuclear Research, 03680, Kiev, Ukraine
(Received July 9, 2012)
High-precision measurements of the relative γ-ray intensities from the decay of 177mLu were performed by means of
a γ-spectrometer. The data were used to determine the internal conversion coefficient (ICC) for the K-forbidden
E1-transition with the energy of 55 keV in 177Hf . High value of the hindrance factor for the γ-radiation leads to
anomalies in the ICC which are observed in the experiment. The discrepancy between experimental and theoretical
values of ICC cannot be explained by admixtures of different multipolarities with the same parity. Such variance can
be eliminated only by assuming the presence of intranuclear conversion.
PACS: 23.20.Lv, 23.20.Nx, 27.70.+q
1. INTRODUCTION
The decay of the three-particle isomeric state in
177Lu (Kπ = 23/2−, T1/2 = 160 days) has been stud-
ied for almost half a century and it still continues.
The characteristics of rotational bands in 177Lu and
177Hf are being studied; the K-forbidden transitions
excited by the decay of the 177mLu cause consider-
able interest. 177mLu can also be used as a calibra-
tion source in nuclear spectroscopy experiments. A
convenient half-life, simple production in the (n, γ)-
reaction, and over 40 sufficiently intense γ-lines in the
energy range of 105 to 465 keV make it a very attrac-
tive isotope for such purposes. The intensities of the
strong γ-rays are known with accuracy of (2...5)% [1],
still there is disagreement on the estimates of intensi-
ties of some of the weaker lines. Precise data on it is
necessary in the first place for calculation of internal
conversion coefficients for the retarded γ-transitions
in which anomalies caused by penetration effect may
occur. Our current research was to clarify all contro-
versial questions in this area.
2. EXPERIMENTAL TECHNIQUE
The relative intensities of γ-rays following the decay
of 177mLu were measured with a γ-spectrometer that
comprises two horizontal coaxial HPGe-detectors:
GMX-30190 and GEM-40195, having the resolution
of 1.89 and 1.73 keV for the γ1332-line of 60Co and
efficiency of 33 and 43% respectively. The radioactive
177mLu sources were obtained in the (n, γ) reaction
as a result of enriched to 27.1% in 176 mass num-
ber lutetium target irradiation with neutrons at the
research nuclear reactor WWR −M . The measure-
ments of γ-ray spectra started two months after the
end of irradiation so that 177Lu (T1/2 = 6.6 days),
having much larger activation cross-section, must
have decayed en masse. The standard 60Co, 133Ba,
137Cs, 152Eu, 228Th, and 241Am γ-sources were used
for accurate calibration of detectors for the energy
range of 26 to 1620 keV . The shape of the efficiency
curve is well described by the Campbell function [2]:
ε(E) =
3∑
i=1
p2i−1e
−p2iE + p7E
−p8 . (1)
Calibration parameters pi were found by the least-
square method. The uncertainty in the efficiency
curve of both detectors does not exceed 2% through-
out the energy range. To minimize possible system-
atic errors a series of measurements were performed
- using different types of HPGe-detectors, at differ-
ent geometries, at different gains and channel widths
of an amplitude-to-digital converter (8192 and 16384
quantization levels of the input signal) - 20 series of
measurements in all.
3. RESULTS AND DISCUSSION
3.1. THE γ-RAY INTENSITIES FROM THE
177mLu DECAY
The γ-ray spectra were analysed using WinSpectrum
[3], a computer program which allows determining
with high precision the energy and intensity of com-
ponents that have an asymmetric line shape and the
ones that are overlapping. The results of our mea-
surements and the data of better works are shown
in Table 1. The γ-transition energies are taken from
Ref.[4]. The usage of different types of detectors al-
lowed us to determine the relative intensities of γ-
rays for the energy range above 100 keV more pre-
cisely. Our data agrees to a great extent with the
data of other researchers while having higher preci-
sion. In the energy range above 100 keV the authors
of Ref. [7] also observed two weak cascade transi-
tions in the reaction 176Y b(9Be, α4n)177Hf with the
energies of 203 and 223 keV between the levels of
the 177Hf ground-state rotational band. In addition,
∗Corresponding author E-mail address: lashkoa@kinr.kiev.ua
ISSN 1562-6016. PROBLEMS OF ATOMIC SCIENCE AND TECHNOLOGY, 2013, N3(85).
Series: Nuclear Physics Investigations (60), p.129-135.
129
at energies less than 100 keV transitions with ener-
gies 14, 55, 69, 71, and 88 keV belong to the decay
of 177mLu. The first two deexcite an isomeric state
(Iπ = 23/2+, T1/2 = 1.1 sec) of the 177Hf , while the
rest are interband transitions from levels of the 9/2+
[624] band to levels of the 7/2− [514] band of the
177Hf ground state.
Table 1. Relative intensities of γ-rays from the decay of 177mLu
Energies of
γ-rays, keV
Intensities of γ-rays, relative units
Present work [5] [6]
105.3589 100.0 100.0 100.0
112.9498 173.0± 2.5 179.1± 8.4 178.6± 5.4
115.8682 5.12± 0.14 5.0± 0.5 5.46± 0.32
117.14 − − 1.51± 0.20
121.6211 48.2± 0.8 48.7± 2.9 48.3± 1.7
128.5027 126.1± 1.8 126.9± 5.7 126.6± 3.5
136.7245 11.47± 0.23 11.4± 1.1 11.41± 0.55
145.7693 7.65± 0.13 7.5± 0.8 7.42± 0.43
147.1637 28.1± 0.4 30.2± 2.3 28.4± 1.5
153.2842 136.2± 2.0 150.0± 7.1 136.4± 3.8
159.7341 4.21± 0.09 5.0± 0.6 4.20± 0.22
171.8574 38.1± 0.6 41.0± 2.2 39.0± 1.4
174.3988 100.8± 1.4 105.3± 5.3 102.5± 2.9
177.0007 28.6± 0.4 28.9± 1.8 28.0± 1.1
181.9093 0.77± 0.07 0.8± 0.2 1.01± 0.10
195.5602 6.60± 0.12 7.2± 0.7 6.86± 0.33
204.1050 109.2± 1.6 119.0± 5.6 111.7± 3.3
208.3662 482± 7 510.0± 22.4 488.0± 13.9
214.4341 51.8± 0.7 54.6± 3.1 53.6± 1.8
218.1038 26.8± 0.5 25.1± 3.0 27.0± 1.1
228.4838 296± 5 310.0± 12.6 300.6± 8.5
233.8615 44.5± 0.7 47.1± 2.3 45.3± 1.7
242.07 0.458± 0.024 − 0.30± 0.10
249.6742 49.0± 0.9 51.3± 2.5 50.0± 2.0
268.7847 27.4± 0.7 28.3± 1.5 28.2± 1.2
281.7868 112.6± 2.3 116.7± 5.3 115.2± 3.4
283.609 3.23± 0.26 4.3± 0.6 2.89± 0.40
291.5429 8.14± 0.30 14.9± 1.3 8.22± 0.57
292.5266 6.75± 0.10 14.9± 1.3 6.67± 0.45
296.4584 39.8± 0.8 44.5± 2.7 40.8± 1.4
299.0534 13.11± 0.29 14.3± 1.0 14.77± 0.54
305.5033 14.11± 0.29 14.5± 1.2 14.87± 0.54
313.7250 9.9± 0.3 11.5± 0.8 9.98± 0.45
319.0210 83.1± 2.3 85.7± 4.7 85.6± 3.0
321.3159 10.3± 0.4 11.6± 0.9 9.93± 0.63
327.6829 145.9± 2.8 145.9± 6.4 148.6± 4.5
341.6432 13.8± 0.4 14.9± 1.3 13.74± 0.61
367.4174 25.1± 0.6 24.8± 1.6 26.07± 0.91
378.5036 241± 5 232.2± 10.7 246.2± 7.4
385.0304 25.4± 0.4 24.5± 1.6 25.99± 0.92
413.6637 138.8± 2.1 137.5± 7.0 143.4± 4.2
418.5388 171.7± 2.3 167.0± 8.4 175.9± 5.3
426.4726 3.64± 0.16 3.4± 0.4 3.52± 0.21
465.8416 19.8± 0.3 19.4± 1.3 19.2± 1.5
The internal-conversion electron lines of the
14 keV transition in L1-and M1-subshells of 177Hf
were observed by the authors of Ref.[8] in the 177mLu
conversion spectrum. The study of the 177mLu
γ-spectrum with a crystal diffraction spectrometer
made it possible to determine the intensity of the
γ55 keV transition [9]. The intensities of γ-rays with
energies of 69 and 88 keV were measured by means
of the anti-Compton Ge(Li) spectrometer and high
resolution Ge(Li)-detectors [10,11]. The γ-transition
with the energy of 71 keV belongs to the decay of
the daughter 177Lu and is observed with confidence
130
in γ-spectrum by authors of all works. It should be
noted that the accuracy of determining of these tran-
sitions’ intensities, except the γ71 keV line, do not
exceed (10...35)%. Therefore, the problem of precise
studies of the low energy region of 177mLu γ-spectrum
is on today’s agenda.
3.2. ON THE ENERGY OF THE γ 242 keV
TRANSITION
γ-transitions with the energy of 242.5 and (242.07±
0.10) keV were observed in the 177mLu γ-spectrum
by the authors of Ref.[11] and Ref.[6] respectively. It
is located in the 177mLu decay scheme as a cascade
transition from the 21/2− to the 19/2− level within
177Hf ground-state rotational band. The energy of
the transition in Ref.[11] is given without measure-
ment error, while its experimental energy value in
Ref.[6] differs from the calculated one by more than
four standard deviations. This raises the question
on the reliability of identification of this γ-transition.
Whether it is true can be seen by thoroughly measur-
ing the transition’s energy and comparing it with the
energy difference for levels between which it occurs.
The energies of 38 γ-transitions accompanying the
177mLu decay were measured by means of a semi-
conductor spectrometer with high (up to a few elec-
tron volts) precision owing to the original method of
the spectrum calibration developed by the authors
of Ref.[4]. The system nonlinearity was determined
with a pulser using a high-precision digital voltmeter.
These data allowed determining the energy levels of
rotational bands and the energy of the isomeric states
in 177Lu and 177Hf with high precision.
In our previous work [12] the energy difference
of several transitions in 177Lu and 177Hf was mea-
sured by using a magnetic β-spectrometer of the π
√
2
type. A joint analysis of these results showed no sys-
tematic errors in the transition energy determination,
and these data have been recommended for use as
energy standards for nuclear spectroscopy. There-
fore, it was decided to use the γ-lines with energies
of (233861.5± 0.5) and (249674.2± 0.6) eV from the
177mLu decay as reference lines to determine the en-
ergy of the γ242 keV transition.
The technique of such measurements was reported
in detail in Ref.[13, 14]. The difference in energy of
the γ249 and γ242 keV lines based on the results of 19
series of measurements is (7445± 60) eV . Weight er-
ror is given as the measurement error. The spread er-
ror turned to be smaller than the weight error, which
indicates the absence of systematic errors of measure-
ments. The obtained difference leads to the γ242 keV
line energy value Eγ(242)exp = (242230 ± 60) eV ,
which is in good agreement with the data from
Ref.[6], but is more precise. The calculated value
of the γ242 keV transition energy is slightly higher
Eγ(242)calc = (242490.5±2.4) eV . The observed dis-
crepancy by four standard deviations may possibly
be explained by the errors of description of the back-
ground near a very weak γ242 keV line, the intensity
of which is three degrees smaller than the one for
the γ233 and γ249 keV transitions. The placement
of the γ242 keV transition in 177mLu decay scheme
is most likely to be true. This conclusion is impor-
tant for the calculation of the intensity balance at
the 21/2−1260 keV level in 177Hf and was used in
the next section of this paper.
3.3. THE TOTAL ICC FOR THE
K-FORBIDDEN E1-TRANSITION WITH
THE ENERGY OF 55 keV
The 177mLu isomer is a very promising nucleus for
searching of anomalies in ICCs for the K-forbidden
g-transitions. Three electric and one magnetic multi-
pole γ-transition with high hindrance factors on the
quantum number K are excited by its discharging
(Fig. 1). Decay of 177mLu occurs both to the 17/2+
level of rotational band of the 177Lu ground state via
K-forbidden E3-transition with energy 116 keV and
to the 23/2+ isomeric state in 177Hf via γ-decay.
The latter state is deexcited by the K-forbidden
M1-transition with the energy of 14 keV to the 21/2+
level of the rotational band of the 9/2+ [624] one-
particle state in 177Hf and by the K-forbidden E2-
transition with the energy of 228 keV to the 19/2+
level of the same band. The discharge of this state
by means of the K-forbidden E1-transition with the
energy of 55 keV to the level of 21/2+ ground state
rotational band of 177Hf is also observed. All of them
are hindered as compared to single-particle estimates.
Some anomalies in γ-ray internal-conversion coeffi-
cients, caused by penetration effect, are possible for
such transitions.
In internal conversion theory, by a penetration ef-
fect or intranuclear conversion is implied a correction
to ICC arising in passing from transition electromag-
netic potentials calculated for point-like nucleus to
the potentials calculated for finite-size nucleus. Gen-
erally, such corrections do not exceed 2% and have
only a slight effect on ICC value. A completely dif-
ferent type of situation occurs in the case of strongly
hindered γ-transitions. In such case a contribution
from internal conversion may become a crucial factor
governing the ICC value. Of course, selection rules,
which are responsible for a decrease in probability of
γ-radiation, should have essentially smaller effect on
the probability of internal conversion.
Appearance of anomalies in ICC of K-forbidden
transitions is due to admixtures with respect to quan-
tum number K in wave functions of initial and fi-
nal states. There are admixtures that allow con-
version transition according to the selection rules
with respect to asymptotic quantum numbers, while
γ-transition is forbidden. In this case anomalies in
ICC caused by the penetration effect are observed.
If the selection rules for conversion transition and
γ-transition are identical, there are no anomalies. At
present, it is very difficult to quantitatively estimate
these admixtures. By this reason, it is not feasible to
make a prediction of anomalies in ICC for a given
K-forbidden transition.
131
Fig.1. The partial decay scheme of 177mLu
Earlier, in Ref. [15, 16] there was found minor
variance between experimental and theoretical val-
ues of ICC for γ228 and γ116 keV transitions, which
cannot be explained by admixtures of different mul-
tipolarities with the same parity. Such deviation can
be eliminated by assuming the presence of intranu-
clear conversion.
The total ICC of the γ55 keV E1-transiton can
be estimated from the balance of intensities of the
21/2−1260 keV level in 177Hf . Following from the
177mHf decay scheme (see Fig.1), this level is pow-
ered by the γ55 keV transition and deexcited by two
intraband γ242 and γ466 keV transitions having the
M1- and E2-multipolarity respectively. The inten-
sity balance at the 21/2− 1260 keV level in 177Hf
can be written as
(1 + α(55))Iγ(55) = (1 + α(242))Iγ(242) +
(1 + α(466))Iγ(466) , (2)
where α(55), α(242), α(466) and Iγ(55), Iγ(242),
Iγ(466) are the total ICCs and transition intensities
with the energy of 55, 242, and 466 keV respectively.
Using our data on the intensities of the γ242 and
γ466 keV transitions from the Table 1, bringing the
experimental value Iγ(55) from Ref.[9] and theoreti-
cal values of ICC for γ242 and γ466 keV transitions
from Ref.[17], we have calculated the total ICC of the
γ55 keV E1-transiton to be α(55)exp = 1.08 ± 0.23.
The theoretical value of ICC in the hafnium for the
γ55 keV E1-transiton is much lower, α(55)th = 0.337.
To coordinate them the existence of the admixture of
M2-multipolarity or the existence of the intranuclear
conversion should be assumed.
The value of the admixture of M2-multipolarity
can be calculated using the expression
α(55)exp − α(E1)
1
1 + δ2(M2/E1)
+
α(M2)
δ2(M2/E1)
1 + δ2(M2/E1)
, (3)
where δ(M2/E1) is M2/E1 multipole mixing ratio
for γ55 keV transition in 177Hf , α(E1) and α(M2)
are the theoretical values of ICC for this transition
assuming E1- and M2-multipolarity respectively.
The obtained value of δ2(M2/E1) = (5.2± 1.6) · 10−3
leads to the Weisskopf hindrance factor for the M2-
component FW (γ55 M2) = (5...9) · 106, while the
factors are much higher for other K-forbidden transi-
tions in 177Lu and 177Hf (Table 2).
Table 2. Weisskopf hindrance factors for K-forbidden transitions in 177Lu and 177Hf
Eγ , keV Multipolarity, L ∆K = Ki −Kf ν = ∆K − L Fw fν = (Fw)1/ν
14 M1 7 6 7.0 · 1010 64.2
55 E1 8 7 3.7 · 1013 86.8
55 M2 8 6 (5...9) · 106 13.1...14.4
116 E3 8 6 9.1 · 108 61.9
228 E2 7 5 1.5 · 108 43.2
132
Table 2 shows that the M2-component for
γ-transition with the energy of 55 keV has a 3.0 to
6.6 times smaller hindrance factor per K-forbidenness
unit fν than other transitions. It means that the
M2-admixture value is likely to be exaggerated 103
to 105 times.
Analyses of the cases of anomalous conversion can
be made with the inclusion of penetration corrections
developed by Church and Weneser [18]. Using the pa-
rameterization of Hager and Seltzer [19] the electric
ICC ′s can be written as
ICC = α(EL)(1 + A1λ1 + A2λ
2
1 + A3λ2 +
A4λ
2
2 + A5λ1λ2) , (4)
where α(EL) are the normal (no penetration) ICC ′s
tabulated in Ref. [17], Ai are coefficients calculated in
Ref. [19] from electron wave functions for the mulipo-
larity of interest, and λi are the electric penetration
parameters. The penetration parameters depend on
nuclear structure and are determined from an analy-
sis of the experimental quantities.
If, as it is in our case, independent experimental
data are insufficient for finding both penetration pa-
rameters λ1 and λ2, the calculations are limited to
one nuclear current parameter λ1, which, in general,
the anomalies in the EL-transitions depend on; the
nuclear charge parameter λ2 is considered to be zero.
Because of the fact that in Ref. [19] the penetration
coefficients are tabulated only for K-, L-, and M -
subshells the following expression was used for the
data set analysis
α(55)exp = αL(1 + AL
1 λ1 + AL
2 λ2
1) +
αM (1 + AM
1 λ1 + AM
2 λ2
1) + αN+O , (5)
where αL, αM , αM+O are the theoretical values of
ICC, AL
i , AM
j are the coefficients for penetration ef-
fect analysis in ICC for L-, M -, and N +O-subshells
of hafnium respectively.
Theoretical values for the conversion coefficients
and penetration coefficients were interpolated from
the tables by Hager and Seltzer [17, 19]. The re-
sults of calculation are listed in Table 3. Known ex-
perimental values of nuclear penetration parameter
λ1l1 for other K-forbidden E1-transitions from the
Ref. [20] are also given in the table.
Table 3. Experimental values of the nuclear penetration parameter λ1 for the
K-forbidden E1-transitions
Nucleus Eγ , keV ν = ∆K − L Fw λ1 Reference
169Tm 240.3 2 2.9 · 109 4.5± 0.6 21
171Tm 295.9 2 9.3 · 108 2.7± 0.6 22
2.8 23
171Tm 308.3 2 5.3 · 108 1.2± 0.4 22
1.2 23
171Y b 19.39 2 1.2 · 109 −(1.5± 0.5) 24
177Hf 55, 15 6 3.7 · 1013 12± 3 present
or − (17± 3) work
180Hf 57.6 7 3.6 · 1016 7.8± 1.0 25
6.9 26
7.0± 0.3 27
6.0± 0.5∗ 28
6.4± 0.3∗ 28
7.7± 1.0∗ 28
7.6± 0.5∗ 28
7.0± 0.7 29
6.8± 0.2∗∗
∗ - Using d2 from different references. ∗∗ - Weighted mean.
For quantitative estimates of nuclear penetration
parameter λ1 depending on the Weisskopf hindrance
factor FW on the basis of empirical data it is con-
venient to draw a graph of such relation using the
experimental data given in Table 3 (Fig. 2).
For Fig. 2 empirical relation (solid line) between
the nuclear penetration parameter —l1— and the
Weisskopf hindrance factor FW for the K-forbidden
E1-transitions was determined without considering
the γ55 keV transition in 177Hf . It is described by
the equation λ1 = a + b lg(FW ). The following val-
ues were found by the least-square method: a =
−(3.5± 1.5); b = 0.63± 0.11. The dashed lines show
a 68% confidence interval. As Fig. 2 shows, the ob-
tained experimental value of λ1 for the γ55 keV tran-
sition in 177Hf appear to be higher than expected
from the empirical relationship.
Despite that, the explanation of anomalies in the
internal conversion coefficients for the E1-transition
with the energy of 55 keV with occurrence of in-
tranuclear conversion, from our standpoint, is more
grounded.
133
Fig.2. Relation between the nuclear penetration
parameter |λ1| and the Weisskopf hindrance factor
FW for the K-forbidden E1-transitions.
1- 171Tm (308.3); 2-171Tm (295.9); 3- 171Y b (19.39);
4- 169Tm (240.3); 5- 177Hf (55.15); 6- 180Hf (57.6);
the number in parentheses is the transition energy
in keV . Smaller by absolute value, |λ1| = 12 ± 3 is
shown for 177Hf
As for possible aspects of further research, it would
be very interesting to obtain experimental data on
the relative intensities of internal-conversion elec-
tron lines on L-subshells of 177Hf for this transition,
or to attempt to determine more precisely the in-
tensity of the γ55 keV photon in γ-spectrum using
high-resolution detectors.
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ИССЛЕДОВАНИЕ РАСПАДА 177mLu
А.П.Лашко, Т.Н.Лашко
На γ-спектрометре с высокой точностью измерены относительные интенсивности γ-лучей, возбуждаю-
щиеся при распаде 177mLu. Эти данные были использованы для определения коэффициента внутрен-
ней конверсии (КВК) -запрещенного E1-перехода с энергией 55 кэВ в 177Hf . Высокий фактор запрета
γ-излучения приводит к аномалиям в КВК, которые и наблюдаются в эксперименте. Расхождения
между теоретическими и экспериментальными значениями КВК нельзя объяснить примесями других
мультипольностей той же четности. Их можно согласовать, только предположив наличие внутриядер-
ной конверсии.
ДОСЛIДЖЕННЯ РОЗПАДУ 177mLu
А.П.Лашко, Т.М.Лашко
На γ-спектрометрi з високою точнiстю помiрянi вiдноснi iнтенсивностi γ-променiв, якi збуджуються
при розпадi 177mLu. Цi данi були використанi для визначення коефiцiєнта внутрiшньої конверсiї (КВК)
-забороненого E1-переходу з енергiєю 55 кеВ у 177Hf . Високий фактор заборони γ-випромiнювання
призводить до аномалiй в КВК, якi й спостерiгаються в експериментi. Розбiжностi мiж теоретичними
та експериментальними значеннями КВК неможливо пояснити домiшками iнших мультипольностей
тiєї ж парностi. Їх можна узгодити лише припустивши наявнiсть внутрiшньоядерної конверсiї.
135
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