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11:25 11.4 L6
MICROCOPY RESOLUTION TEST CHART
NATIONAL BUREAU OF STANDARDS -1963
1
.
.
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k ondig war vonimisoimmer Fentan yang menciptannien
totesine
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:
e 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.
..
.
-
-
-
-
-
11.
-
-
i.
-
.
-
-
.
.
.
-
.
.
;
..
S
.ORNO -1957
CONE-6505252 MAO
-,
-
.
+
:
:- (To be presented at the International Conference on the Internal Conversion Process,
Nashville, Tennessea, May 10 - 13, 1965)
ORNE AEC - Official
obo
:.:.
A SURVEY OF E1 TRANSITIONS IN THE RARE-EARTH REGION
W.B. Ewbank, Oak Ridge National Laboratory, Oak Ridge, Tennessee
Abstract
A review of the lifetimes and conversion properties of all predominantly
El-transitions in rare-earth nuclei has confirmed the correlation between the
.
gamma-ray hindrance and the observed anomalies in internal conversion coef-
ficients..
It is further shown that the anoinalies occur only in those transitions
.
.
.
.
for which internal conversion is allowed by the interaction of orbital electrons with
the nucleon spin-current inside the nucleus. The coefficients for conversion of a
transition in the K shell and in the L1, L2 subshells are shown to be increased by
about the same factor over their theoretical values.
·
.
.
.
In the rare-earth region of the periodic table there are several nuclei in
.
which E1 transitions exhibit anomalous conversion coefficients.1,2 The enhance-.
...
....
ment of K-, Ly- and Ly-conversion is observed to be as high as ten times the
theoretical values. In order to establish the cause of the observed anomalies, a
survey of all predominantly-E1 transitions in the rare-earth region was made. The
data on measured conversion coefficients were analyzed into groups consistert with,
. . . . PATENT CLEARANCE OBTAINED. RELEASE TOE
THE PUBLIC IS APPROVED. PROCEDURES
. ARE ON FILE IN THE RESUVING SECTION,
*Research sponsored by the U. $. Atomic Energy Commission under contract with
the Union Carbide Corporation.
: ORNL-AEC-OFFICIAL
i.
:
.
-2.
the penetration-conversion picture developed by Church and Weneser, 3 and by Nilsson
and Rasmussen, 4 and Kramer and Nilsson.5
ORNE OMEC - OFFICIAL
.
The penetration-matrix-element formalism may be used to distinguish three
..ways in which the nucleus may give up energy:
1. Photon emission
2. "Normal" internal conversion (which takes place in the
neighborhood of the nucleus, but does not include con-
tributions due to electron penetration into the nuclear
volume)
3. Penetration-conversion, in which the electron must be
present inside the nucleus
ime
The latter will be most sensitive to details of the distribution of nuclear charge and
bath
magnetism throughout the nucleus.
the
....
Three interactions which affect the penetration-conversion have been considered
.. in Refs. 3 - 5:
3a. The nuclear charge
ar
ons
.
.
3b. The intranuclear currents
..
.
.
3c. The nucleon spin-currents
.
„
Since the operators which describe these interactions are different, they will generally
:
. impose different sets of selection rules on the nuclear transition.
In Refs. 3 - 5, the selection rules for E1 transitions between Nilsson states
have been derived for each of the penetration-conversion operators. These are shown
-
-
in Table I. For simplicity, only those possibilities allowed for each operator, but
not allowed for normal photon emission, are listed. If normal photon emission is..
LE
.
.
allowed, then it will be of little importance that a penetration interaction also causes
.
ORNI- AEC - OFFICIAL
!
AEC - OFFICIAL
transitions. When the normal processes are highly forbidden, however, the pene-
on aina orainataan harian
tration effects assume their greatest importance.
The data used in this survey are listed in Table II. For each transition,
VE
the table includes the Nilsson quantum numbers of the initial and final states, the
.i.
.'.
.
factor Fw by which the transition is hindered from the Weisskopf estimate, and the" :-
:
wwmavá.
.
."
enhancement factor by which the observed conversion intensity exceeds that calçu-
w
memberi per
lated by Sliv and Band6 for a pure E1 transition. (Possible M2-admixtures have
n
a
not been considered.) All E1 transitions in nuclei with neutron number between 90,
and 112 are included if both the half-life and at least one conversion coefficient or : :,
itinda atalmashindwartaw
·
ratio is known. Since ratios Lj:L2:L3 are measured more frequently than absolute
L-subshell conversion coefficients, the ratios L1/L2 and L2/L7 have been tabulated
"
.
.
,..1
..
::.:.:.
...
h
rather than a I, and on.
This procedure has been empirically justified by the.
observation that Lz conversion coefficients are approximately normal, while anom-
alous conversion appears to be most important for ai, and al.: Presumably; this:
W
stems from the fact that K-, Ly- and Ly-conversion involve electron transitions of
the type 51/26-1/2, while Lg-conversion always involves the P3/2 orbital
.
.
'
electron. For cases where all three have been measured, UK, L1/L3 and L2/L3 are:
seen to have approximately the same ewhancement factor.
The enhancement factors (observed/theoretical) for the transitions in Table II
are plotted as a function of photon hindrance in Fig. 1. To avoid confusion, the errors
have not been put on the points of this graph, although they are shown on subsequent
an
figures.
ORNC-AEC - OFFICIAL
?.
.
The procedure now is to display separately the group of transitions that
ORNI - AEC - OFFICIAL
obey the selection rules for each operator so as to isolate the operator that is
responsible for the large conversion anomalies for Fw about 106.
.
. .
.
.
Emission of E1 photons is forbidden by the asymptotic selection rules on
:...
Nilsson quantum numbers for all the transitions in Table II. The total probability
for internal conversion is evidently forbidden to about the same degree, since most.:
of the conversion coefficients are normal as shown in Fig. 1..
None of the operators discussed by'Refs. 1 - 3 for El transitions will allow
Jak >i. The transitions from Table II which have AK = 2, +3 are shown in Fig. 2.
Although the data scatter somewhat, there appears to be no systematic enhancement
..
'ii:
...
of the conversion for these transitions.
...
..
Transitions for which penetration-conversion is allowed by the operators
. involving nuclear charge (3a) or intranuclear currents (3h) are shown in Fig. 3. For
: a wide range of hindrance factors there appear to be no anomalous conversion effects
that can be attributed to these kinds of penetration conversion. The greatest enhance-
ment is really only an upper limit for the ratio K/L3 in 15?gd. A careful measuremeni.
.....
of the relative intensity of the 2.14-keV conversion electrons from this transition would
.
.
..
remove the one ambiguity in this picture.
Transitions for which penetration-conversion is allowed by the nucleon spin-
currerts (3c) in the nucleus are summarized in Fig. 4. The.errors shown on each point
: ..
.
represent those assigned by the experimenters. Points without error bars may be
uncertain by a large factor. For the transitions in Fig. 4 a definite correlation between
enhancement and hindrance can be seen. Beginning at about Fw = 105 the enhancement
factor increases from unity to nearly ten for Fw = 6 x 106. The 0.32 transition in
OANL=AEC - OFFICIAL
...
-
-5
-5-
... :
. -
.
...
-..--con
::.
.
.
.
:...
- AEC - OFFICIAL
;,
..
"..
177hf may represent a maximum hindrance for this class of transition in the rare-
earths. For transitions in nuclei with higher or lower mass number, the hindrance:
factor is lower. (This apparent maximum gamma-ray hindrance has been discussed;
by Vergnes.' Precise measurements of Qx and the L-subshell ratios for the 0.321
......:::::
:
gamma in 177Hf would be very interesting.' More data on the three transitions in
175 Lu would also be useful. The apparently low enhancement factor for the 0.145
transition from the 0.396 level in 175Lu may be the result of imprecisely-known
.
branching ratios for the three de-exciting gamma rays. Improvements could also be
made in the precision of other ineasurements in Fig. 4.
The hindrance factors for some other El transitions in this group are included
- on the figure as a guide to their probably conversion anomalies. The only significant
..
1.
anomaly among these other transitions may arise for the 0.006 transition in 181Ta.
Unfortunately, the low energy prohibits any K-or L-subshell results for this transition:
The remaining E1 transitions with | Ks 1 from this survey are placed in Fig. 5) :
The group at the left are allowed by a second-order term in the nucleon spin-current
interaction. No conversion enhancement can be inferred for this class of transitions 16
.
within the small range of hindrance values shown. The 0.086 transition in 155Gū at the
:::::..
right of Fig. 5 involves An = 3, which cannot be expected from the interactions con
...
sidered here. The conversion coefficients are quite close to their expected theoretical
:
:* ....
values.
ir
:
.,
...
..!..
ni i i..
OANL - AEC - OFFICIAL
...
1
1
.
...
.
.
...
-6-
..
.
;
References
:.'.
ORNI - AEC - OFFICIAL
1. C.J. Herrlander and G.T. Ewan, to be published, "Conference on the Role ..
of Atomic Electrons in Nuclear Transformations," Warsaw 1963, G.T. Ewan,
priv. comm.
:.:.:.,::...
:
.
:
,,
.
2. Adopted values for branching ratios, half-lives and conversion-electron ratios
have been taken from recently-revised Nuclear Data Sheets (published by the ..
National Academy of Sciences, Washington, D.C., 1964-1965). .:.
:.:.::
3. E. L. Church and J. Weneser, Nucl. Phys. 28, 602 (1961).
4. S. G. Nilsson and J.O. Rasmussen, Nucl. Phys. 5, 617 (1958)...
I
.
'
.
-5. G. Kramer and S. G. Nilsson, Nucl. Phys. 35, 273 (1962).
.
.
.
.
.,
::
6. L. A. Sliv and I.M. Band, Coefficients of Internal Conversion of Gamma Radiaa:
tion, Part 1: K-Shell (1956), Part 2: L-Shell (1958), Academy of Sciences of the
USSR, Leningrad Physico-Technical Institute, Leningrad; Issued in the U.S.A.
as Reports 57 ICC K1 (1957) and 58 ICC L1 (1958), Physics Department, Univer-
sity of Illinois, Urbana, Illinois,
.
7. M.N. Vergnes, Nucl. Phys. 39, 273 (1962).
-
.:.
.
: .
.
.
...
:
...
..
...
::::...
:
OANL - AEC - OFFICIAL
.
...:
.
.
:-
.
S
·
-
.
..
.
-
e
Figure 1.
Enhancement of observed QK, Lj/L2 or L2/L3 over theoretical El
value plotted as a function of the hindrance of the photon half-life .
over the Weisskopf estimate. Data are included for all £1 transi-
tions in rare-earth nuclei.
:::ORNL-AEC - OFFICIAL
:
.
..
...
:.
zoak enhancement
x .3.
+123
id
.
mi
+
Tover) (E1) = 873.3 fs
o
o
.
X+o
XO
LLLL
o
-
.
.
Enhancement
.
..
.
.
.
..
X
.
O
o
to 8+
O
...
O
..
.
:
O
++x 8
+*
tx .
10
-OX
Oxt
...............
.
xoto 008
.
.
.
الا
..
i
..
- O'RNL - AEC - OFFICIAL
liididiri-will- odes
Nuwe
Hindrance
:. Fw
..
.
.......
.
..
..
::? Figure 2. Enhancement factors for El transitions with AK >1. The enhance-
ment of the observed QK, L1/Lz or L2/L3 over the theoretical El .
value is plotted as a function of the hindrance of the photon half-life.
over the Weisskopf estimate.
.
ORNL - AEC - OFFICIAL
<
::
i
O K enhancemen
X 123
.
i.
. .
..
.
. L2/L3
.-:..
.
.
....
.
.....
-,--...
.
.
.
.
-
-
-
..
--
--
-
to
--
.
..
LILULILI

:::::......
:.:.:.
OK =12
::
OK - #3
":
U
.
::
.:
.
.
Enhancement
ii.
...
m
Otxt
10txt
Axor
--
-
b+*
.'
LI
173 Lu 0.124
5/2 1/2 (541) – 7/27/2(404)
ORNL - AEC - OFFICIAL
golio
10°
Hindrance:
:
100-
Figure 3. Enhancement factors for E1 transitions allowed by penetration
interactions involving the nuclear charge or intranuclear current
(Selection rules in Table I b). The enhancement of the observed ..
ax, L1/L3 or L2/Lg over the theoretical El value is plotted as a
function of the hindrance of the photon half-life over the Weisskopf
estimate.
ORNL-AEC - OFFICIA!
OK
-3
enhancement
. и
x
+ 12/13 ::
IIIII
0.064 (KIL_3)
Enhancement
+X0-
X
:::
+
O
O
:
LLLLLL
O
.
OANL - AEC - OFFICIAL
0.1L
103
103
* 104
Hindrance 105
104
105
home deco
vie loire la community
. Whiline para mantenenti
i l.

ORNL - AEC -0$FICIAL
Figure 4. 'Enhancement factors for E1 transitions allowed by penetration inter-
· actions involving the nucleon spin-current (Selection rules in Table I c).
. The enhancement of the observed ik, L1/L3 or L2/Lz over the theo-
retical E1 value is plotted as a function of the hindrance of the photon.
half-life over the Weisskopf estimate.
RNL - AEC - OFFICIAL
.
.
.
1
..
.
ak onnoncomont
X LV3 ".
.in
na. ..
----Le
-
175 Lu (4396
0977H 0.321
.
.
To 0.02
177L4 0.150
.
Enhancement
f
I 175 Lu 0:283
04 TX
. to
O
''Hf 0.0726
177HF 0.208
LU 0.145
.
:
LLLLLLLL
161. in 17946 :
0.102 0.217
0.006
.
.
ORNI - AEC - OFFICIA
.ORNL - AEC - OFFICIAL
...0.1
1034
1045
i
100 $6
1067
1074
finna thinnen'.
..
Figure 5. Enhancement factors for E1 transitions with AK S1, but forbidden
by all selection rules in Table 1. The enhancement of the observed,
QK, L1/L9 or L2/L3 over the theoretical El value is plotted as a:
function of the hindrance of the photon half-life over the Weisskopf:
estimate.
OKNL - AEC - OFFICIAL

.
..
.-
**
-
.-
-
.
13
00 OK enhancement
.. X LKs
+423
:.:.
.
:.:
10
C
-
.
'
:;::
-
: Enhancement.
1556d 0.086
3/2 3/2 (651-- 3/2 3/2 (521)
.An3
.
-
II:
-
- ORNE - AEC - OFFICIAL
O
. 103
10 *Hindrance 1082
104
105
1 06
ORNL - AEC - OFFICIAL
Table I. Asymptotic Selection Rules for E1 Transitions
Δ2
ΔΛ.
a. Photon emission or "normal" conversion
1
1
0
+1
0
- 1
b. Penetration-conversion by nuclear charge
or intranuclear currents
- gioi sº là
+ 1
+ 2
£ 1
$ 2
- 1
ܝܺ ܘ ܘܝܽܘ
c. Penetration-conversion by nucleon spin-
currents (first-order term)
1
|
ORNL - AEC - OFFICIAL
INTE
1
AN
TO
111
IN
LU
BLANK PAGE
.
.....
.-
."-
...
IVILIQ -
V - INYO :
:
VIÐ1110 - 53V - INYO
.::
...
...Level..
(MeV).
TABLE IV: PREDOMINANTLY-EI TRANSITIONS IN RARE-EARTH NUCLEI
wccorAssignments
.y
Sélection.
Initial
Final
Hindran
(ns)(MeV)
Rule Type
-
di Ki Na Toko Nole
(Table 1)
Enhancement
in
e
):
F,
.
--
_
_
.. 47/13: Loh
..:
:...
.
.. .
.
;
.
.
.
.
::.
153EU
5/2
572
1.0.
.
None
5/2
5/2
5/2
3/2
3.2 411
5/2.532
5/2 532
3/2 411
5/2
512
5/2
5/2
532
413
413
532
5.5(4)
<5.5(3)
2.7(3)
0.9
155EU
5/2
5/2
None
b
1.3
1.5 2.
1.7.6
8.7(4)
1556d
3/2
,
5
5/2
3/2
None
None
3.0(5)
4.2(5)
1.5(4)
9.5(3)
1.4.2
3/2
j.j :
1.1
0.8
.
3/2
1.0
1.2.
1576d
159Tb
3/2
1.42
<4(K/L3)
<1.4
1.0(6)
5/
2
5/2
53 2.
3.4(5)
2.5(5)
3.6(4)
0.9
161Tb
7/2 72 523
7/2 3/2 411
5,2
3/2
52 52 413
7/2 3/2 41
5/2
5/2 5/2 413
3/2 3/2 411
0.9
0.075 0.14 0.075
0.097 <1 0.097
0.104 <0.4 0.104
0.246 1.2 .0.142
0.086 5.0 0.026
0.086
0.105 1.0 0.045
0.105
0.064 460 0.064
0.363 0.16 0.225
0.305
0.363
0.418 0.87 0.102
0.284
0.361
0.482 <0.2 0.165
0.482
0.026 28 0.026
0.075 3.0 0.075
0.379. 50 · 0.063
0.240
0.261
0.425 2600 0.296
0.308
0.351 0.45 0.172
0.273
0.351
0.124 75000. 0.124
0.396 3.3 0.145
0.283
2.0
AK = -2
AK = -2
None
3.414)
. 9.8(5)
2.5(5)
<1.0(3)
1.3
5/2
5,2
532
0.9
b
161 Dy
5/2
3/2
7/2
5/2
3/2
7/2
523
521
523
b.
1697m
None
1.0
1711m
712 72
523
17346
712
7/2
633
173LU
175LU
5/2
912
1/2
9:2
541
594
5/2 5/2 · 642 None
4.7(3)
1.1
0.9
5/2.5/2 642
4.9(4) 0.82 1.12 12 0.938 .
7/2 404
7.1(4)
411 AK = -3 9.4(8)
5/2
AK = -3 1.1(8) 0.9
7/2
--3 1.1(9) 1.18 12 1.04 11 0.98 10
AK = -3 5.1(8) 1.13 7. 1.06 11 1.08 10
912 5/2
7.0(4) 0.6
7/2
5.3(4) 0.7(KL) 0.7 ---
- 5/2
6.6(6) 0.6
7/2 7/2 404 Ak = +3
+3 7.7(8) 0.87 2 0.81 0.84
!12 7/2 404
1.3(6) 1.0
- 9.2
9.7(5) : -1.5. 1.5
. 2.4
.
Ć
1.7(6)
Sir - OFFICIAL
92 92 624
1.5 2 .
712 712 404c 3 .2(6): 256 2. ji 3
112 7/2 514
1.4(5): 1.4
4 1.5
2 1.54
972
☺ 3.1(4) : 0.9 2. 1.18.11 1.13 11
7/2
6.2(6) 76 .
9/
2 9/2 624 C.
712 7/2 404, c . 1.9(5) :-:-"1.8.::.
7/12 5/2 402 AK ---2-----2.7(6). 1.5.: 0.9
7 0
in
'n
.
.
: .iii..
.i
i
i
.
20
-...2;..
ar
..
.
...
;:
..
..
.
. .
.
.
. :
i
..
ORNL - AEC - OFFICIAL
3.64)
.
...
.
.
..
.
17746
177 LU
: 177HF
0.104
0.150
0.321
| 0
4.5 0.104' 72 72 514
120 0.1509 /
29/2 514
0.67 0.072 9/2. 9/2 624
; : 0.208
0.321
1.8: 0.217 7/2 7/2 514
1400 -0.031 9/
2 9/2 514
570 0.072 9/2 972 514
0 0 0
Late
8.7(4):.......
.
...
.
179Hf
179T
187Re
0.217
0.031
0.206
-
.
.
.
..
°Blank lines imply the same quantum numbers as on the preceding line.
Power-of-ten multiplier in parentheses: 1.3(6) = 1.3 x 106
::
.
END

DATE FILMED
9/9/65
--
- -
-
---
-
A
-
-