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MICROCOPY RESOLUTION TEST CHART
NATIONAL BUREAU OF STANDARDS - 1963
LEGAL NOTICE
This report was prepared as an account of
Government sponsored work. Neither the
United States, nor the Commission, nor any
person acting on behalf of the Commission:
A. Makes any warranty or representa-
tion, expressed or implied, with respect to
the accuracy, completeness, or usefulness
of the information contained in this report,
or that the use of any information, appa-
ratus, method, or process disclosed in this
report may not infringe privately owned
rights; or
B. Assumes any liabilities with respect
to the use of, or for damages resulting from
the use of any information, apparatus,
method, or process disclosed in this report.
As used in the above, "person acting on
behalf of the Commission” includes any em-
ployee or contractor of the Commission, or
employee of such contractor, to the extent
that such employee or contractor of the
Commission, or employee of such contractor
prepares, disseminates, or provides access
to, any information pursuant to his employ-
ment or contract with the Commission, or
his employment with such contractor.
of diamond
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ORNA P-1248
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CONF-65052553
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SUN ? 1965 :
(To be presented at the International Conference on the Internal Conversion Process,
Nashville, Tennessee, May 10 – 13, 1965)
ORNI - AEC - Oficile
.
SOME CONVERSION COEFFICIENTS WHICH SHOULD BE MEASURED*
:
SS
Agda Artna, Oak Ridge National Laboratory, Oak Ridge, Tennessee
:.
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Abstract
A number of cases will be pointed out where a measurement of the conver-
sion coefficient or of the conversion coefficient catios would be of considerable
.
interest. These cases fall into thrve groups.
*
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1.LT
1. Values of conversion coofficients in apparent disagreement with theory
..
4:
have been reported in some rare-e:irth nuclei, for example in 175Lu and 17?Lu.
Further study of cases where disagreement between experiment and theory is
.
indicated or expected would be of interest.
2. Different experiments have led to different conclusions about the tran-
sition multipolarity. For example, o obtained from angular correlation experiment
does not agree with 82 obtained froin conversion electron studies (172Yb, 181Ta).
r
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3. Conversion coefficients are not known to a desired precision. No values
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of conversion coefficients or ratios have been reported. Knowledge of these would be
-,
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H
4
T
ind
helpful in assigning spins and parities to nuclear levels. Examples: 163Dy, 169Er.
1
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Introduction
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During the preparation of Nuclear Data Sheets, the Nuclear Data Group has
noted a number of cases where measurements of conversion coefficients would be
.
OANL - AEC - OFFICIAL
*Research sponsored by the U. S. Atomic Energy Commission under contract with
the Union Carbide Corporation,
PATENT CLEARANCE OBTAINED. RELEASE TO
THE PUBLIC IS APPROVED. PROCEDURES
AREON EILE IN THE RECE’YING SECTION,
2.
of considerable interest. Some of these will be pointed out in this paper. The dis
:
ORNI - AEC - OFFICIAL
cussion will be limited to the mass region where the Nuclear Data Sheets have been
recently revised, that is A = 150 to A = 180. All the experimental results quoted
are taken from the Nuclear Data Sheets (Volumes 5 and 6) where exact references
are given.
The cases to be discussed fall into three groups in which:
1. Comparison between experiment and theory is of interest
.
2. Disagreement between different pieces of experimental information
exists
3. Conversion coefficients, not previousiy measured, are of interest.
Group 1
. In the first group belong the so-called anomalous, hindered El transitions.
It seems that all El transitions in the rotational nuclei are highly hindered. Further
it appears that some of them have anomalous conversion coefficients, while others
do not. A review of the E1 transitions in odd-mass nuclei in the rotational region
will be presented at this conference by W.B. Ewbank, who will point out the cases
.
of interest. Since hindered transitions can tell us something about the configurations
of the nuclear levels involved, it would be of interest to investigate further the E1
transitions in even-A nuclei. Table la shows a list of some hindered transitions in
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even-mass nuclei. This list includes only the transitions for which the half-life has
been measured. There are many transitions believed to be E1, where the lifetime
has not been determined, for example 1525m, 154, 156, 158Gd, 156Eu, 160, 162 Dy;
168Er, and 174yb.
OANL - AEC - OFFICIAL
-3-
Another group of transitions which belong to this category are the E2
.
ORNL - AEC - OFFICIAL
transitions between collective levels. Table 1b shows a list of transitions 2+ to
0+ in even-mass nuclei, and one case of E2 transition from a y-vibrational level
to the ground state of an odd-mass nucleus. The fact that the measured value is
always a little higher than the theoretical one has been observed before, and in
...
some cases has been explained as due to experimental difficulties. However, it
is interesting to note that in Er167 where the conversion coefficient has been meas- ::
i. e.
ured for a pure collective motion transition, the transition from a vibrational level.'
to ground state, the measured conversion coefficient is again higher than theory.
..
It seems, therefore, that it would be interesting to learn more about the E2 tran- :
sitions between collective motion levels.
Group 2
Secondly, I would like to point out some cases where there are discrepancies
between different experimental measurements. A list is given in Table 2. The first
part of the table shows cases where different measurements of the conversion coef-
ficient have given different values, such different values that multipolarities cannot
be established until some more work is done on the conversion coefficients. The.
second part of the table presents cases where the multipolarity obtained from the
conversion coefficients does not agree with other experimental information, or with
. .
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the level scheme as proposed.
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Group 3
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Table 3 contains a list of nuclei for which measurements of conversion coef-
.
ficients would be of great help in establishing and understanding the level scheme."
..
In the case of 160Ho it is a question of the spin of a single level, the 5-hr, 0.060-
OANL - AEC - OFFICIAL
MeV isomeric state. In the other cases, either the whole level scheme or a number
of higher energy levels are still to be satisfactorily described and understood.
TABLE 1A. HINDERED EI TRANSITIONS IN SOME EVEN-MASS NUCLEI
Nucleus
Transition
Energy
(MeV)
ak
ORNE - AEC - OFFICIAL

(Transition)
(sec )
Measured Theoreticalº
Remarks
Theoretical
Measured
625mgo
0.0015
0.0010
0.0012
0.00097
$0.4
0.12
169H099
168E1200
El from L, iLq:Ls
0.842
0.963
0.137
0.0993
0.198
0.273
0.831
1.016
0.630
0.995
0.0575
6x10-14
7.3 x 10-14
2x 10-4
4x10-5
9 x 10^6
3 x 10-5
1.6 x 10-7
2.4 x 10-5
8.9 x 10-4
2.1 x 10-4
2.4 x 105
5 x 10-16
4 x 10-16
9 x 10-14
2x 10-13
4x10-14
1 x 10-14
5 x 10-16
3x10-16
1x 10-15
3 x 10-16
8 x 10-13
17696,04
0.0038
a = 0.54 4
0.00128
ay = 0.23 El from Lizha
199HF, 08
and an
Weisskopf estimate. From Nuclear Spectroscopy Tables by A. H. Wapstra, G. J. Nijgh, R. van Lieshout,
p. 73 (1959).
TABLE 1b. E2 TRANSITIONS

Nucleus
Theoretical
260Dy
1.55
..
I
..
2.1
.
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164Dy
164Er
166Er
..
..
TO
1.
Transition
ak
Energy (MeV) Spin Change Measured
0.0868 | 24->0* 1.65 2, 1.5, 1.7,
1.52, 1.59, 1.67,
2.0 2
0.07339 2->0* 2.7 5
0.0915 | 27- 01
11.92
0.0806 2- 07 1.9, 1.7 3, 1.9 2,
1.76 15, 1.9,
1.75 7, 1.85 1
1.67 7
0.08419 2-0+ 1.60 15, 1.65 12,
1.56 15, 1.57 15,
1.69 2, 1.46 5.
1.34 7, 1.31 8
0.08836 | 21- 0* 1.32 11, 1.35 7,
1.25, 1.10,
1.37 7
0.532 3-> * 0.035 15, 0.015
'.
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1704b
1.38
',.-:...
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ORNL - AEC - OFFICIAL
..
176Hf
1.12
..
..war
167Er
0.113
nain w
i
e:
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TABLE 2. CASES WHERE DISCREPANCIES EXIST BETWEEN DIFFERENT
EXPERIMENTAL MEASUREMENTS
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ак
ORNb - AEC - OFFICIAL

Nucleus
Transition
Energy
(MeV)
Other Information
Measured
Theoretical
1525m
1.389
yy(@) and yy(L.) requirs El + <1% M2
159 Tb
0.0004
0.0015
0.039 8
0.008
0.0081 20
0.0085 18
0.026 5
0.0005 EI
0.0015 M1
0.052 MI
0.0087 E1
0.363
1735 m
0.399
0.0086 EI
0.0242 E2
154GB
0.874
167 Er
0.0072
0.0053
0.55 10
20.75
*0.6
0.0025
0.00268
0.0054 MB | (0.874y)(0.1231y)(0) requires 5 38 514
0.0030 E2 (0.724y)(0.874y)(0) requires -40>8 >19
0.460 E3 KiL,:L, L, indicates E3 transition
From lovelscheme 1/2° to 7/2*
0.2079
172Yb
1.094
0.0026 E2
0.0048 M1
0.023 M3
0.00086 E1
1744b
1.240
0.00066 33
yy(o data indicatos ina inly dipole
transition with small amount (<1%)
quadrupole or octupole admixture
(1.240y)(0.0765y)(0) requires
8 = -0.26 4 if d, -2
.-0.17 4 if J... 3
J, - 3 preferred from B-decay data
yy(0) requires 99% M1 + 1% E2
181T.
0.4821
Conversion data indicatos
15% MI + 85% E2
ORNI - AEC - OFFICIAL
TABLE 3. NUCLEI FOR WHICH CONVERSION COEFFICIENT MEASUREMENTS
WOULD BE OF INTEREST

Transition
Energy
Remarks
Nucleus
160H0
| 0.060 MeV
.163Dy
163Er
167Tm
1677b
Isomeric transition. L:L:L, ratios fit E2, E3, E4, favor E3.
Half-life favors E4..
Spins of levels other than g.s. rotational band are not known.
Spins of levels above 0.300 MeV are not known.
Transition intensities have been calculated from ce-intensities and
theoretical conversion coefficients. Resulting intensity balance
on level scheme is very poor.
No satisfactory level scheme can be proposed without a knowledge of
some transition multipolarities.
No transition multipolarities are known.. Proposed level scheme is
based entirely on analogy with 17 Yb.
No transition multipolarities are known.
Level scheme has not been established.
Spins of levels above 0.890 MeV ure rot known.
Level scheme has not been established.
169Er
1725m
172 Lu
173LU
176 Lu
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END
DATE FILMED
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