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Selected gamma-ray energies and emission probabilities for the decay of 125Sb and 154Eu
A&. Rod&. Isor. Vol. 41. No. I, pp. 75-81, hf. .I. Radiar. Appl. Insrrum. Part A Printed in Great Britain
1990
0883-2889/90 $3.00 + 0.00 Pergamon Press plc
Selected Gamma-ray Energies and Emission Probabilities for the Decay of 12jSb and ‘j4Eu R. G. HELMER Idaho
National
Engineering
Laboratory,
EG&G
Idaho,
Idaho
Falls, ID 83415, U.S.A.
(Received 4 March 1989) The energies of 17 y rays from 12Sb and 35 from lS“Eu have been determined with typical uncertainties of 5510 eV. Relative y-ray emission rates have also been measured for 16 y rays from n5Sb and 24 from ‘54E~. These data will make more useful the mixed standard of lz5Sb, ‘54E~ and 15’Eu that is often used to calibrate Ge p-ray detectors
1. Introduction
ships within the decay schemes were used to check the consistency of the uncertainties, to test for systematic errors and for ‘25Sb to compute the energies of other y rays: The radionuclides used for the energy calibrations and for the reference lines were 46Sc, @‘Co, 94Nb, “OrnAg, ,37Cs, 139Ce, IOBrnA ‘*‘Ta and *“Bi. The g, energies for the associated y rays taken from Helmer et al. (1979) are on the keV scale on which the strong y ray from the decay of 19’Au has an energy of 411.8044(11) keV. For each energy difference, several spectra were obtained. Each spectrum was measured at a different gain in order to average out any systematic distortion caused by the ADC (Wilkinson-type). For each spectrum a set of calibration lines was used to determine the parameters of the energy function E(x) = a + bx + cx*, where x is the channel. For two peaks at channels X, and X2, the energy difference is
Although, as illustrated by the data in Helmer et ai. (1979), the energies of many y rays are known well enough to be used for energy calibration of y-ray spectra, it is particularly convenient if the same sources can be used for both efficiency and energy calibration. One of the commonly used sources for the efficiency calibration of Ge II-ray detectors is the mixture of ‘25Sb, ‘54E~ and “‘Eu which was developed as a calibration standard by the National Bureau of Standards (now known as the National Institute of Standards and Technology) (Coursey et al., 1982). The y-ray energies for ‘*‘Sb and ‘54E~ are not, however, particularly well measured. Therefore, to make this mixed source more useful, we have determined values for the energies of 17 lines from ‘*%b and 35 from ls4Eu. At the same time, we have measured the relative y-ray emission rates for these two nuclides, so that these data will be available for any future evaluations. These measurements were made with a high-purity, p-type Ge, closed-end coaxial detector with a volume of about 114 cm). 2. Gamma-ray
AE = E, - E, = b(X, -A’,)
+ c(X; - A’:).
The uncertainties in the X,, 0(X,), are available from the peak analyses; and those associated with the parameters b and c are available from the energy calibration. As long as the two peaks of interest are resolved, we expect covar(X,, X2) = 0; then, we have
Energies
Since the measurement methods used are similar to those previously described (Greenwood ef al., 1970; Helmer et al., 1971), only a brief description of them will be included herein. All of these measurements involve the determination of the energy difference between two closely spaced, but resolved, lines in the same spectrum. Given the energy of one line, that of the other was computed. Cascade
var(AE) = (b + 2cX, )‘.var(X,
)
+ (b + 2cX,)*.var(X,) +(X2 - X,)*.var(b) +(X:
- Xi)2.var(c)
+2(X2 - X,) (X: - X:) .covar(b, 75
c).
R. G.
16
For all of these measurements, approximated quite accurately
this expression by
HELMEK Table
can be
I. Effect
peak
energy.
and
‘“‘Ta
of source+letector Data
source
are for
distance
a ‘“Co
source
on measured
(I 173)
at 15 cm
(I 189)at variousdistances
from
the
detector
var(AE)
z h’[var(X,)
+ var(X,)]
‘“Ta
2. Gamma-ray
energy
differences
Maximum 7 -Rays
and
Number
of
spectra
nuclides 172-156(Ta)
(7)
52
3
15.787
(9)
4x
4
15.790
(9)
45
5
15.797
(9)
3x
7
I5 SOO(7)
35
IO
I5 X17(7)
IX
17.5
IS X19(9)
Ih
25
15.X20(7)
number
lS.K~5 m parentheses
determined
position
correction
(ev)
4
for
“‘Sb
Energy difierence
(kev)
zk
I 93
16.325(14)
5
6.X60
(7)
172-176(Sb)
4
3.601
(14)
172-l
4
6.682(16)
176-165
(Ce)
l76-179(Ta)
0.69
I 93 2.24
5
IO 459
( I)
0.49
4
3.0x2
(I)
33
(8)
204-198
(Ta)
4
5.786
208--19X
(Ta)
4
9.730(17)
208-204
(Sb)
8
208-222
(Ta)
4
427433
(Ag)
5
~- 1.5
6.063
(I
443433
(Ag)
5
+ I.5
9.61X
(8)
463-433
(Ag)
s
+ 1.5
29.428(l)
600-529
(Bi)
5
i- I.0
30.899
(I
600-614
(A@
5
~ 2.0
13.681
(I)
606-600
(Sb)
5
606-614(Ag)
G
0 m the la\t
diglts.
172.-l65(Ce) 79 (Ta)
(10) is the uncertainty
The results of the energy difference measurements for “‘Sb and ls4Eu are given in Tables 2 and 3. In these measurements :! variety of source positions were used, but a typical arrangement had the sources from I5 to I8 cm from the detector. In all cases the sources were at 9 cm or more and in all cases the spread in positions was 5cm or less. The corrections for the differences in the source positions were made. These vary between spectra. but the maximum corrections are noted in the tables. From these energy differences and the known energies of the reference lines, the measured “‘Sb y-ray energies have been computed as given in the first four columns of Table 4. Where several values are available, some care is needed in deducing the uncertainty of the average value. In many cases the average calculation will result in an uncertainty that is less than those of the reference lines. In some cases this might be correct, but in most cases it is not correct. In column 5 of Table 4 we have increased several computed uncertainties to meet an arbitrary requirement that the final uncertainty be at least 1 eV greater than the minimum uncertainty for the associated reference lines.
the uncertainty is completely statistical so the uncertainty in the average o(AE) will be smaller than the individual a(AE) as long as xi d 1.0. (If 1; > 1.0. the external uncertainty, which includes a factor lRI is used.) As is discussed in Helmer et ul. (1975) and the references therein, the pulse height of a ;I-ray peak changes with the distance between the source and the detector. To determine the magnitude of this effect for the detector used here, one set of measurements was made. In this case a 6oCo source was placed at 15 cm from the detector and ‘*‘Ta sources were measured at distances from 2 to 35cm. The values obtained for the 1I89( ‘*‘Ta)-1173( “Co) energy difference are given in Table 1 and show a shift of - 50 eV over this distance range. Two analytical steps were taken in order to obtain the corrections needed for this study. First, a smooth curve was drawn through the data from Table I. Second, it was assumed that the correction was proportional to the y-ray energy as suggested by the data in Fig. 5 of Helmer et al. (1975) which shows this correction as a function of both the y-ray energy and distance from another detector. Table
leV1
(keV)* 15.783
dig11 or
’ term
h[az(XZ) + aL(X
peak
2
35 *The
I” energ>
difference
(cm)
For a group of measurements of the same energy difference, a weighted average AE is computed with the weights taken as a(AE)-‘. The consistency of the individual values is judged on the basis of the reduced-x’ value, xi. To the extent that a(AE) is dominated by the
Shift
11x9.1173
SO”nx
distance
or
3.939
I 08 3.0
(9)
I .53
14.029(16)
-2.0
7.564
5
+2.0
21.669(l)
)
2.4 0.80 I .66
6.117(3)
5
2.30
)
0.35 0.30 2.0X
(2)
I.61
635614
(Ag)
0.20
635-661
(Cs)
5
-3.0
25.705
(I)
0.44
671-661
(Csl
5
+3.0
9.785
(3)
I .92
Decay
of ‘15Sb and
‘54Eu
Table 3. Energy differences determined Maximum position correction (eV)
for ‘54E~
Reference-line (kev)
Number of spectra
123%113(Ta) 123-l I6 (Ta) 188%179(Ta) 188-198 (Ta) 247-229 (Ta)
4
9.399(l)
4
6.651(2)
1.57
4
8.858(S)
0.63
4
IO.101 (8)
0.82
4
18.608(l)
0.25
247-264 401433 444433 444446 467446
(Ta) (Ag) (Ag) (Ag) (Ag)
4
16.145(l)
0.26
Differences (kev)
x: 0.39
4
+1.0
32.678(14)
1.62
4
-1.0
10.557(6)
0.56
3
-1.0
2.324(7)
3
+ 1.0
21.03
591414(Ag) 625-614 (Ag) 625.-620 (Ag) 625-661 (Cs) 676461 (Cs)
4
fl.0
22.519(3)
2.7
4
-1.0
'0.970(B)
0.59
676-702 692461 692487 692-702 692-706
(Nb) (Cs) (Ag) (Nb) (Ag)
7 15-702 715-706 723-706 723-744 756-744 756-764 845-8 I8 850-B I8 850-871 850-884
(5)
I.13 0.52
2
fl.0
4.982115)
0.00
4
fl.0
36.403(g)'
0.55
4
-1.0
14.938(16)
1.26
5
+2.0
26.044(13)
0.96
4
- 1.0
30.761(3)
1.04
3
+ 1.0
5.416(4)
0.25
5
f2.0
10.223(3)
0.18
3
-1.0
14.255(3)
0.70
(Nb) (Ag) (Ag) (AS) (Ag)
5
-2.0
13.148(20)
2.3
3
+ I.0
3
+ I.0
16.625(2)
1.39
3
-1.0
20.976(4)
0.39
3
+1.0
12.521(4)
0.75
(AS) (Ag) (Ag) (Nb) (Ag)
3
-1.0
7.136(3)
0.20
3
+1.0
27.392(7)
0.59
3
+1.0
32.612(15)
0.32
2
+0.5
20.487(24)
2.0
3
-1.5
34.037(15)
0.03
873-871 (Nb) 873-884 (Ag)
2
-0.5
2.066(6)
0.44
3
- 1.5
88&87l(Nb)
2
88&889(k) 892-884
9.096(22)
0.02
ll.494(3)
0.04
-0.5
9.48 (4)
0.00
4
+ I.5
8.663(30)
0.02
2
+ I.5
8.099(10)
0.63
892-889(k)
5
- 1.5
3.498(15)
0.07
904-884
3
+1.5
19.384(6)
904_889(Sc)
5
-1.5
14.805(5)
1.44
904-927(Ta)
4
+1.0
23.917(12)
0.79
904-937
3
-1.5
33.419(6)
2.2
3
- I.5
12.85 (5)
0.10
3
+1.5
58.774(3)
0.56
3
-1.0
36.538(9)
0.12
4
+ 1.0
5.445 (5)
4
-1.0
3.031 (5)
2.8
10041044(Ta) ll28-112O(Sc) 1128-l 121 (Ta) I 128-l I73 (Co) 1140--1120(sc)
4
+1.0
39.685(10)
0.63
5
-2.0
8.009(S)
0.19
3
-1.0
7.265(22)
1.01
2
-2.0
44.664(14)
0.13
5
-2.0
20.167(R)
0.90
114~1173(c0) 1160_1173(Co) IIBB-I 173 (Co) 1241-1231 (Ta) 12461257 (Ta)
2
-2.0
32.529(17)
0.01
I
-2.0
12.87
I
+2.0
14.86 (4)
4
-15
10.36 (5)
1.39
4
+1.5
11.268(7)
0.85
127&-1332(Co)
2
-2.0
58.063(6)
0.28
127&1384
3
-2.0
109.865(4)
0.11
1290-1332(h)
I
-2.0
41.99
1397-1384
(Ag) (Ag)
3
+2.0
13.05 (5)
2.5
3
+2.5
l&260(9)
0.61
(Ag) (A& (As) (A@ (A@
3
-2.5
2
i2.5
10.992 (7) 32.77 (4) 24.50 (4) 20.02 (4) 34.193(17)
0.48 0.34 0.55 0.06 2.6
(Ag) (Ag)
(Ag)
924-937
(Ag) 996-937 (Ag) 996-959 (Ta) 996-1001 (Ta) 1004-1001 (Ta)
149&1475 14961505 1537-1505 1537-1562 1542-1562
1596-l 562
(Ag)
2
-2.5
2
-2.5
3
+2.5
0.93
2.6
(Xj
(IO)
-
-
R. G.
7x
HELMER
Relationships in the “‘Sb decay scheme can be used to test the assigned uncertainties, and to determine the energies of other 7 rays. To do this a least-squares fit to the energies of the levels at 35,443, 463. 636, 642 and 671 keV was carried out, and then the y-ray energies were computed from these level energies, The corrections for nuclear recoil are taken into account by the fitting program. The results of the calculations are given in column 6 of Table 4; they include energies for six y rays that were not measured directly. From these results it is concluded that the energies and their uncertainties are reasonable, since the only significant difference is for the 7 ray at 172 keV. Adopted or recommended energies are given in the last column of Table 4. From the energy differences in Table 3 and the known energies of the reference lines, several y-ray energies for i5“Eu have been computed and are given in Table 5. As discussed above, the uncertainties in the average values have not been allowed to be as small as the smallest value for an associated reference line. The decay scheme of ‘54E~ is very complex and involves about I50 7 rays. As for “‘Sb, one could use the measured energies and do a least-squares fit to some of the level energies and then deduce the energies for many of the other y rays. However, since there are many multiplets in this y-ray spectrum, the calculation of these values without a detailed study of the spectrum might be misleading. Therefore, a much simpler check of the consistency of our measurements has been made. As given in several footnotes to
Table 4. Measured
Lines 172-i 56 172.165 172-l 76 172-l 79
(Ta) (Ce) (Sb) (Ta)
176-165(G) l76-179(Ta)
3. Relative
Gamma-emission
;I-ray energw
for decay of “‘Sb
Difference (keV)
i-Ray energy (keV)
156.3874 (5) 165.857 (6) 179.313(l) 179.3948 (5)
16.325 (14) 6.860 (7) 3.601 (14) 6.682(16)
172.712(14) 172.717(9) 172.712(14) 172.713(16)
172 714(6)
165.857 (6) 179.3948 (5)
IO.459 (1) 3.082(l)
176 316(6) 176.313(l)
1763lill)
20&19X
(Ta)
198 3530 (6)
5.786 (8)
(Ta) (Sb) (Tb)
198.3530 (6) 204.139 (8) 222.1099 (6)
9.730(17) 3.939 (9) 14.029 (16)
427-433 443433 463433 600-569 600-614
(Ag) (Ag) (Ag) (Bi) (Ag)
433.936 433.936 433.936 569.702 614.281
(4) (4) (4) (2) (4)
6.063 9.618 29.428 30.899 13.681
606400 606-614 635-614 635461 671-661
(Sb) (Ag) (Ag) (Cs) (Cs)
600.601 614.281 614.281 661.660 661.660
(2) (4) (4) (3) (3)
6.1 17 (2) 7.564 (2) 21.669(l) 25.705 (I) 9.785 (3)
reference energies are from Helmer “‘Sb lines from this work.
(I ) (8) (I) (I) (I)
Average (keV)
Computed energy (keV)
Adopted energy (keV)
35.489 (5)
35.489 (5)
I72 723 (4)
17?.719(Xl
178.842 (5) 198.654 (I I )
176.313 (I) I78 842 (5) 198654(ll)
204 139(X) 208.083 (17) 208.078 (13~ 208.081 (16)
600.601 (2) 600.600 (4) 606.718 606.717 635.950 635.955
Probabilities
The results of an initial measurement of the relative ;I-emission rates were reported by Coursey et al. (I 982) at the time that the use of this mixed standard was proposed. Although other measurements have been made (see the evaluations in Tamura et ol., 1981; Helmer, l987), it would be desirable to have another such determination, so we have undertaken such a measurement. The efficiency of this detector was most recently calibrated in September 1987 and the “‘Sb and lS4Eu measurements were made in February and March 1988. All spectra involved were analyzed with the GAP program (Killian and Hartwell. 1988) on a VAX-750 computer. This program automatically finds peaks, defines a fixed linear background and the fitting range, and fits a Gaussian to the data points in the peak. The interpolated efficiency values were determined from the hand-drawn curves through the measured values. It is estimated that the uncertainty in the interpolated efficiency is 1% below 300 keV and 0.75% above that energy. See Helmer (1988) for more details concerning this efficiency determination. Due to the long time period between the efficiency calibration and the measurements, it is important to
Reference energy (keV)*
20X-198 208-204 208-222
*All
and computed
Table 5 a crossover y-ray energy is computed from the energies of the cascade y rays for comparison with the measured crossover y-ray energy. These comparisons indicate that these energies and uncertainties are quite consistent.
(3~ (4) (4) (3)
704 139 (8)
208 080 (9)
208.079 227.891 380.452 408.065
427.873 (5) 443.554 (9) 463.364 (5)
427.877 (4) 463 366 (4)
427.X75 (6) 443.554 (9) 463.365 (5)
600.601 (3)
600.599 (3)
600.600 (4)
(4) (IO) (8) (IO)
606.?18(3) 635.953 (4) 671.445 (4)
208.079 227.891 380.452 408.065
(4) (IO) (8) (IO)
606.71X (3) 635.955 (4) 671.444 (4)
er a/. (1979) except those for the lx9Ce line at 165 keV. which is from Helmer
635.954 (5) 67 I.445 (4) el ul. (1971) and the
Decay Table 5. Measured Reference energy (keV)*
Lines
of ‘25Sband
79
ls4Eu
~-ray ._ energies _ from the decav of lYEu Difference (keV)
Average (keV)
123-I 13 (Ta) 123-l I6 (Ta) 188-l 79 (Ta) 188-198 (Ta) 247-229 (Ta)
113.6723 (4) 116.4186(7) 179.3948 (5) 198.3530 (6) 229.3220 (9)
9.399 6.651 8.858 IO.101 18.605
247-264 401433 444433 444446 467446
264.0755 (8) 433.936 (4) 433.936 (4) 446.811 (3) 446.81 I (3)
16.145 (I) 32.678 (14) 10.557 16) 2.324 (7) 21.03 (5)
591&614(Ag) 625414 (Ag) 625420 (Ag) 625461 (Cs) 676-661 (Cs)
614.281 (4) 614.281 (4) 620.360 (3) 661.660(3) 66 I.660 (3)
22.519 (3) 10.971) (8) 4.982 (I 5) 36.403 (8) 14.938 (16)
625.251 (9) 625.342 (Is)? 625.257 (8) 676.598(16)
676-702 692461 692487 692-702 692-706
(Nb) (Cs) (Ag) (Nb) (Ag)
702.645 661.660 687.015 702.645 706.682
(6) (3) (3) (6) (3)
26.044 30.761 5.416 10.223 14.255
(I 3) (3) (4) (3) (3)
676.601 692.421 692.431 692.422 692.427
(14) (4) (5) (7) (4)
715-702(Nb) 715-706 (Ag) 723-706 (Ag) 723-744 (Ag) 756-744 (Ag)
702.645 706.682 706.682 744.277 744.277
(6) (3) (3) (3) (3)
13. I48 9.096 16.625 20.976 12.521
(20) (22) (2) (4) (4)
715.793 715.778 723.307 723.301 756.798
(21) (22) (4) (5) (5)
756-763 845-818 850-818 850-871 850-884
(Ag) (Ag) (Ag) (Nb) (Ag)
763.944 (3) 818.031 (4) 818.031 (4) 871.119(4) 884.685 (3)
7.136(3) 27.932 (7) 32.612(15) 20.487 (24) 34.037 (15)
850.643 (16) 850.632 (24) 850.648(15)
873-871 873-884 880-871 880-889 892-884
(Nb) (Ag) (Nb) (SC) (Ag)
X71.119(4) 884.685 (3) 871.119(4) 889.277 (3) 884.685 (3)
2.066 (6) Il.494 (3) 9.48 (4) 8.663 (30) 8.099 (IO)
873.185 (7) 873.191 (4) 880.60 (4) 880.614 (30) 892.784(10)
892-889 904884 904-889 904927 904-937
(SC) (Ag) (SC) (Ta) (Ag)
889.227 884.685 889.277 927.992 937.493
(3) (3) (3) (5) (4)
3.498 19.384 14.805 23.917 33.419
892.775 904.069 904.082 904.075 904.074
(15) (7) (6) (I 3) (7)
924-937 (Ag) 996-937 (Ag) 996-959 (Ta) 996-1001 (Ta) 1004-1001 (Ta)
937.493 937.493 959.730 1001.695 1001.695
(4) (4) (5) (5) (5)
12.85 (5) 55.774 (3) 36.538 (9) 5.445 (5) 3.031 (5)
996.267 996.268 996.250 1004.726
(5) (IO) (7) (7)
10041044(Ta) ll28-ll2O(Sc) Il28-II21 (Ta) 1128-l 173 (Co) 1140_1120(Sc)
1044.408 1120.545 1121.301 1173.238 1120.545
(5) (4) (5) (4) (4)
39.685 8.009 7.265 44.664 20.167
(IO) (8) (22) (14) (8)
1004.723 (I I) 1128.554 (9) 1128.566 (23) 1128.574(15) 1140.712(9)
1004.725 (7)‘
114&1173(c0) 116&l 173 (Co) 1188&1173(Co) 1241-1231 (Ta) 1246-1257 (Ta)
1173.238 (4) 1173.238 (4) 1173.238 (4) 1231.016(5) 1257.418 (5)
32.529 (17) 12.87 (8) 14.86 (4) 10.36 (5) I 1.268 (7)
1140.709 (17)
1140.71 I (9)” 1160.37 (8) Il88.10 (4) 1241.38 (5) 1246.150 (9)
127&1332 (Co) 12741384 (Ag) 129G-1332 (Co) l397-1384(Ag) 1494-1475 (Ag)
1332.502 1384.300 1332.502 1384.300 1475.788
(5) (4) (5) (4) (6)
58.063 (6) 109.865 (4) 41.99(10) 13.05 (5) 18.260 (9)
14941505 1537-1505 1537-l 562 1542-l 562 1596-l 562
1505.040 I505.040 1562.302 1562.302 1562.302
(5) (5) (5) (5) (5)
10.992 (7) 32.77 (4) 24.50 (4) 20.02 (4) 34.193 (7)
(Ta) (Ag) (Ag) (Ag) (Ag)
(Ag) (Ag) (Ag) (Ag) (Ag)
(I) (2) (8) (8) (I)
y-Ray energy (keV)
(I 5) (6) (5) (12) (6)
123.071 123.070 188.253 188.252 247.930
(I) (2) (8) (8) (I)
247.930 (I) 444.493 (7) 444.487 (8)
123.071 (I) 188.252 (8) 247.930 (I) 401.258 (14) 444.490 (6) 467.84 (5) 591.762 (5)
756.808 (4)
625.254 (7) 676.600 (12)
692.425 (4)f 715.786(18) 723.305 (5) 756.804 (5) 845.423 (8)
850.643 (I 2) 873.190(5) 880.61 (3) 892.781 (9)
904.076 (6) 924.64 (5)
1274.439 (8) 1274.435 (6)
996.262 (6%
1128.560 (8)
1274.436 (6)tt 1290.51 (IO) 1397.35 (5)
1494.048 (I I) 1494.048 (9) 1537.81 (4) 1537.80 (4)
1494.048 (9):t 1537.80 (4) 1542.28 (4) 1596.495 (l8H
*All values are from Helmer er al. (1979) except those for the ‘“‘Ta lines at 927, 959, 1001, and 1044 keV which were computed from the values in Helmer et al. (1979) and the decay scheme. tValue not used in average. fFrom 247 + 444 sum, computed energy is 692.419 (6) keV. §From 123 + 873 sum, computed energy is 996.260 (5) keV. q/From 247 + 756 sum, computed energy is 1004.733 (5) keV. **From 247 + 892 sum, computed energy is 1140.709 (9) keV. ttFrom 401 + 873 sum, computed energy is 1274.446(15) keV. IfFrom 247 + 1246 sum, computed energy is 1494.078 (4) keV. @From 591 + 1004,692 + 904 and 723 + 873 sums, the average computed energy is 1596.491 (5) keV.
80
R. G.
HELMER
coincidence summing (from KORSUM computer code, Debertin and Schotzig, 1979) and the detector efficiencies are also given there. Due to the very low count rate the random summing or pile-up correction, which would be -0.1% for all peaks, is neglected. The resulting relative y-emission probabilities are given in column 5. The components in the quoted uncertainties are as follows. That for the peak area is shown with the average area. For the coincidence summing, it is taken as 20% of the correction (i.e. 20% of the factor shown minus 1.0). As noted above, for the efficiency the uncertainty is 1.0% below 300 keV and 0.75% above there. The results in the 1981 Nuclear Data Sheets evaluation (Tamura et al., 1981) and the subsequent measurements of Coursey er al. (1982) Iwata et al. (1984) and this work are generally in agreement.
have an estimate of the possible change in the efficiency. This has been monitored by monthly measurements with a source of “‘Eu [t,:2 = 4933(11) days]. We estimated that variations in any peak area of 0.14.2% are to be expected from variations in the fitting process. This is especially true since the low-energy tailing on the peak is not taken into account in the peak-shape function. The results (Helmer, 1988) are then consistent with no change in the efficiency curve over the time period of interest. For “‘Sb four spectra were measured at a count rate of 72 s-’ for durations of 20,000-55,000 s. This gave 1.2 x 10’ to 3.4 x IO5 counts in the peak at 427 keV. For each y ray, the average peak area, relative to that of the 427-keV peak, was determined as an unweighted average. These results are given in Table 6. The calculated correction factors for Table ;’ Energy (keV) 116.6 172.7 176.3 204.1 20x.1
6. “%b
relative
.J-emission
Coincidence summing corrections
Relative peak area I899 (48) 1345 (19) 46.661 (I 19) 2026 (39) I538(26)
probabilities Efficiency (I x IO’)
1.0106 I .0078 I .0034 1.0107 I .0078
3.70 3.44 3.41 3.17 3 I4
Relative ;,-emission probability 8.67 (24) 6.59(11) 229.6 (24) 10.80 (23) 8.25(16)
227.9 321.1 380.5 408.1 421.9
776 1809 5704 655 = 100.000
(40) (38) (30) (19)
1.0071 I .00X7 I .003l I .0055 I.0017
2.95 2.17 I.861 I .749 I .675
4.43 (23) 14.1 (3) 51.4(5) 6.30(19) = 1000.(8)
443.6 463.4 600.6 606.7 636.0
985 32,743 44.069 12,358 26.687
(27) (SO) (67) (42) (74)
I .003x 0.9999 1.0016 1.0016 1.0015
I.622 I.561 I .249 I .239 I.191
IO.19 (29) 350.7 (28) 590.9 (45) 167.0(14) 357.2 (30)
4122 (22)
0.9993
I. I 39
60.5 (6)
671.4
Table y Energy (keVI
7. lS4Eu relative
Relative txak area
y-emwmn
Coincidence summing corrections
probabilities Efficiency (f x 102)
Relative y-emission probability
123.1 188.3 248.0 401.3 444.5
642,436 (I 150) 3193(13) 79,426 (I 15) l428(10) 3809(17)
I .0062 I.0191 1.0143 I .0095 I .02Ol
3.70 3.315 2.72 I .772 1.620
ll65(12) 6.55 (7) 198 (2) 5.43 (6) 16.00(15)
478.3 557.6 582.1 591.8 692.6
1454(g) 1525(19) 4826 (6) 26,573 (24) X378 (24)
I .0083 I .Ol67 I.0135 1.0143 I.0114
I.518 I.329 I.283 I.265 I.1 IO
6.44 (6) 7.78(11) 25.43 (2!) 142.! (I I) 50.9 (4)
723.4 756.8 815.6 845.4 873.2
9 1,092 (94) 19.771 (28) 2135(ll) 2418 (20) 47.212 (32)
I .0095 1.0162 0.989X I.0133 I.0125
1.071 I.032 0.969 0.941 0.916
573 (4) 129.9(11) 14.55 (14) 17.37 (20) 348. I (ZS)]
904. I 996.3 1004.8 1128.5 1140.8
3341 (IO) 36,681 (35) 62,570 (59) 1050(14) 739 (7)
I.0130 I .0004 I .0079 I .0081 I .0008
0.890 0.822 0.816 0.742 G.735
25.37 (22) 297.8 (23) 515.5 (40) 9.52(15) 6.71 (8)
1.0148 I .0074 I .0040 0.9917
0.684 0.672 0.591 0.560
24.49 (23) = 1000.0 19.79 (16) 50.78 (40)
1245.8 1274.5 1493.8 1596.6
2475(ll) - I00,000 I746 (4) 4299 (8)
Decay
of lz5Sb and ‘54E~
Similar measurements were carried out for “IEu. Two sources were used and they gave count rates of 1590 SC’ and 3970 s-‘. The source material was prepared in 1976 by isotope separation at the INEL. A common impurity in ls4Eu samples is is2Eu. From the peak at 1408 keV, the measured spectra indicated that the ‘52E~ content was such that - 0.1% of the peak at 122 keV, the major interference, was due to 152E~. Thus, any interference is negligible. The 15“Eu spectra were measured for periods of 12,00(~50,000 s and the 1274-keV peak had areas of 4.5 x 10’ to 4.6 x lo6 counts. At these count rates the corrections for random summing (pile-up) range from 2.6 to 7.3%. However, we report the y-emission probabilities relative to that of the 1274-keV y ray. Therefore, only the variation of this correction with the y-ray energy needs to be taken into account. This variation is only 0.4% for the weaker source and 1.0% for the stronger one. Four spectra were measured for each source. For each 7 ray the four peak areas, relative to that of the 1274-keV line, were averaged and corresponding uncertainty calculated. After correcting each average for random summing, a weighted (by c-2) average of the two values was computed. These values, the calculated coincidence summing correction factors, and the interpolated detector efficiencies are given in Table 7. The resulting relative y-ray emission probabilities are given in column 5 of this table. The
81
uncertainties have been computed as discussed above for iz5Sb. The results of this work and those summarized in the 1987 Nuclear Data Sheets evaluation (Helmer, 1987) generally agree well. Acknowledgement-We wish to thank R. A. Anderl for providing the isotope separated sample of 15”Eu. This work was supported by the U.S. Department of Energy under DOE (Contract No. DE-AC07-76IDOl570.
References Coursey, B. M., Hoppes D. D. and Schima F. J. (1982) Nuci. Instrum. Methods 193, 1. Debertin K. and Schiitzig U. (1979) Nucl. Instrum. Methods 158, 471. Greenwood R. C., Helmer R. G. and Gehrke R. J. (1970) Nucl. Instrum. Methods ?I, 141. Helmer R. G. (1987) Nucl. Data Sheets 52. 1. Helmer R. G. (1988) Report EGG-PHY-8250. Helmer R. G., Greenwood R. C. and Gehrke R. J. (1971) Nucf. Instrum. Methods 96, 173. Helmer R. G., Gehrke R. J. and Greenwood R. C. (1975) Nucl. Instrum. Methods 123, 51. Helmer R. G., Van Assche P..H. M. and van der Leun C. (1979) AI. Data Nucl. Dala Tables 24, 39. Iwata Y., Yasuhara M., Moeda K. and Yoshizawa Y. (1984) Nucl. Instrum. Methods 219, 123. Some of the ‘54E~ data in this article come from Yoshizawa Y., Iwata Y. and Iinuma Y. (1980) Nucl. Instrum. Methods 174, 133. Killian E. W. and Hartwell J. K. (1988) Report EGG-2533. Tamura T., Matumoto Z. and Ohshima M. (1981) Nucl. Data Sheets 32, 497.
1990
0883-2889/90 $3.00 + 0.00 Pergamon Press plc
Selected Gamma-ray Energies and Emission Probabilities for the Decay of 12jSb and ‘j4Eu R. G. HELMER Idaho
National
Engineering
Laboratory,
EG&G
Idaho,
Idaho
Falls, ID 83415, U.S.A.
(Received 4 March 1989) The energies of 17 y rays from 12Sb and 35 from lS“Eu have been determined with typical uncertainties of 5510 eV. Relative y-ray emission rates have also been measured for 16 y rays from n5Sb and 24 from ‘54E~. These data will make more useful the mixed standard of lz5Sb, ‘54E~ and 15’Eu that is often used to calibrate Ge p-ray detectors
1. Introduction
ships within the decay schemes were used to check the consistency of the uncertainties, to test for systematic errors and for ‘25Sb to compute the energies of other y rays: The radionuclides used for the energy calibrations and for the reference lines were 46Sc, @‘Co, 94Nb, “OrnAg, ,37Cs, 139Ce, IOBrnA ‘*‘Ta and *“Bi. The g, energies for the associated y rays taken from Helmer et al. (1979) are on the keV scale on which the strong y ray from the decay of 19’Au has an energy of 411.8044(11) keV. For each energy difference, several spectra were obtained. Each spectrum was measured at a different gain in order to average out any systematic distortion caused by the ADC (Wilkinson-type). For each spectrum a set of calibration lines was used to determine the parameters of the energy function E(x) = a + bx + cx*, where x is the channel. For two peaks at channels X, and X2, the energy difference is
Although, as illustrated by the data in Helmer et ai. (1979), the energies of many y rays are known well enough to be used for energy calibration of y-ray spectra, it is particularly convenient if the same sources can be used for both efficiency and energy calibration. One of the commonly used sources for the efficiency calibration of Ge II-ray detectors is the mixture of ‘25Sb, ‘54E~ and “‘Eu which was developed as a calibration standard by the National Bureau of Standards (now known as the National Institute of Standards and Technology) (Coursey et al., 1982). The y-ray energies for ‘*‘Sb and ‘54E~ are not, however, particularly well measured. Therefore, to make this mixed source more useful, we have determined values for the energies of 17 lines from ‘*%b and 35 from ls4Eu. At the same time, we have measured the relative y-ray emission rates for these two nuclides, so that these data will be available for any future evaluations. These measurements were made with a high-purity, p-type Ge, closed-end coaxial detector with a volume of about 114 cm). 2. Gamma-ray
AE = E, - E, = b(X, -A’,)
+ c(X; - A’:).
The uncertainties in the X,, 0(X,), are available from the peak analyses; and those associated with the parameters b and c are available from the energy calibration. As long as the two peaks of interest are resolved, we expect covar(X,, X2) = 0; then, we have
Energies
Since the measurement methods used are similar to those previously described (Greenwood ef al., 1970; Helmer et al., 1971), only a brief description of them will be included herein. All of these measurements involve the determination of the energy difference between two closely spaced, but resolved, lines in the same spectrum. Given the energy of one line, that of the other was computed. Cascade
var(AE) = (b + 2cX, )‘.var(X,
)
+ (b + 2cX,)*.var(X,) +(X2 - X,)*.var(b) +(X:
- Xi)2.var(c)
+2(X2 - X,) (X: - X:) .covar(b, 75
c).
R. G.
16
For all of these measurements, approximated quite accurately
this expression by
HELMEK Table
can be
I. Effect
peak
energy.
and
‘“‘Ta
of source+letector Data
source
are for
distance
a ‘“Co
source
on measured
(I 173)
at 15 cm
(I 189)at variousdistances
from
the
detector
var(AE)
z h’[var(X,)
+ var(X,)]
‘“Ta
2. Gamma-ray
energy
differences
Maximum 7 -Rays
and
Number
of
spectra
nuclides 172-156(Ta)
(7)
52
3
15.787
(9)
4x
4
15.790
(9)
45
5
15.797
(9)
3x
7
I5 SOO(7)
35
IO
I5 X17(7)
IX
17.5
IS X19(9)
Ih
25
15.X20(7)
number
lS.K~5 m parentheses
determined
position
correction
(ev)
4
for
“‘Sb
Energy difierence
(kev)
zk
I 93
16.325(14)
5
6.X60
(7)
172-176(Sb)
4
3.601
(14)
172-l
4
6.682(16)
176-165
(Ce)
l76-179(Ta)
0.69
I 93 2.24
5
IO 459
( I)
0.49
4
3.0x2
(I)
33
(8)
204-198
(Ta)
4
5.786
208--19X
(Ta)
4
9.730(17)
208-204
(Sb)
8
208-222
(Ta)
4
427433
(Ag)
5
~- 1.5
6.063
(I
443433
(Ag)
5
+ I.5
9.61X
(8)
463-433
(Ag)
s
+ 1.5
29.428(l)
600-529
(Bi)
5
i- I.0
30.899
(I
600-614
(A@
5
~ 2.0
13.681
(I)
606-600
(Sb)
5
606-614(Ag)
G
0 m the la\t
diglts.
172.-l65(Ce) 79 (Ta)
(10) is the uncertainty
The results of the energy difference measurements for “‘Sb and ls4Eu are given in Tables 2 and 3. In these measurements :! variety of source positions were used, but a typical arrangement had the sources from I5 to I8 cm from the detector. In all cases the sources were at 9 cm or more and in all cases the spread in positions was 5cm or less. The corrections for the differences in the source positions were made. These vary between spectra. but the maximum corrections are noted in the tables. From these energy differences and the known energies of the reference lines, the measured “‘Sb y-ray energies have been computed as given in the first four columns of Table 4. Where several values are available, some care is needed in deducing the uncertainty of the average value. In many cases the average calculation will result in an uncertainty that is less than those of the reference lines. In some cases this might be correct, but in most cases it is not correct. In column 5 of Table 4 we have increased several computed uncertainties to meet an arbitrary requirement that the final uncertainty be at least 1 eV greater than the minimum uncertainty for the associated reference lines.
the uncertainty is completely statistical so the uncertainty in the average o(AE) will be smaller than the individual a(AE) as long as xi d 1.0. (If 1; > 1.0. the external uncertainty, which includes a factor lRI is used.) As is discussed in Helmer et ul. (1975) and the references therein, the pulse height of a ;I-ray peak changes with the distance between the source and the detector. To determine the magnitude of this effect for the detector used here, one set of measurements was made. In this case a 6oCo source was placed at 15 cm from the detector and ‘*‘Ta sources were measured at distances from 2 to 35cm. The values obtained for the 1I89( ‘*‘Ta)-1173( “Co) energy difference are given in Table 1 and show a shift of - 50 eV over this distance range. Two analytical steps were taken in order to obtain the corrections needed for this study. First, a smooth curve was drawn through the data from Table I. Second, it was assumed that the correction was proportional to the y-ray energy as suggested by the data in Fig. 5 of Helmer et al. (1975) which shows this correction as a function of both the y-ray energy and distance from another detector. Table
leV1
(keV)* 15.783
dig11 or
’ term
h[az(XZ) + aL(X
peak
2
35 *The
I” energ>
difference
(cm)
For a group of measurements of the same energy difference, a weighted average AE is computed with the weights taken as a(AE)-‘. The consistency of the individual values is judged on the basis of the reduced-x’ value, xi. To the extent that a(AE) is dominated by the
Shift
11x9.1173
SO”nx
distance
or
3.939
I 08 3.0
(9)
I .53
14.029(16)
-2.0
7.564
5
+2.0
21.669(l)
)
2.4 0.80 I .66
6.117(3)
5
2.30
)
0.35 0.30 2.0X
(2)
I.61
635614
(Ag)
0.20
635-661
(Cs)
5
-3.0
25.705
(I)
0.44
671-661
(Csl
5
+3.0
9.785
(3)
I .92
Decay
of ‘15Sb and
‘54Eu
Table 3. Energy differences determined Maximum position correction (eV)
for ‘54E~
Reference-line (kev)
Number of spectra
123%113(Ta) 123-l I6 (Ta) 188%179(Ta) 188-198 (Ta) 247-229 (Ta)
4
9.399(l)
4
6.651(2)
1.57
4
8.858(S)
0.63
4
IO.101 (8)
0.82
4
18.608(l)
0.25
247-264 401433 444433 444446 467446
(Ta) (Ag) (Ag) (Ag) (Ag)
4
16.145(l)
0.26
Differences (kev)
x: 0.39
4
+1.0
32.678(14)
1.62
4
-1.0
10.557(6)
0.56
3
-1.0
2.324(7)
3
+ 1.0
21.03
591414(Ag) 625-614 (Ag) 625.-620 (Ag) 625-661 (Cs) 676461 (Cs)
4
fl.0
22.519(3)
2.7
4
-1.0
'0.970(B)
0.59
676-702 692461 692487 692-702 692-706
(Nb) (Cs) (Ag) (Nb) (Ag)
7 15-702 715-706 723-706 723-744 756-744 756-764 845-8 I8 850-B I8 850-871 850-884
(5)
I.13 0.52
2
fl.0
4.982115)
0.00
4
fl.0
36.403(g)'
0.55
4
-1.0
14.938(16)
1.26
5
+2.0
26.044(13)
0.96
4
- 1.0
30.761(3)
1.04
3
+ 1.0
5.416(4)
0.25
5
f2.0
10.223(3)
0.18
3
-1.0
14.255(3)
0.70
(Nb) (Ag) (Ag) (AS) (Ag)
5
-2.0
13.148(20)
2.3
3
+ I.0
3
+ I.0
16.625(2)
1.39
3
-1.0
20.976(4)
0.39
3
+1.0
12.521(4)
0.75
(AS) (Ag) (Ag) (Nb) (Ag)
3
-1.0
7.136(3)
0.20
3
+1.0
27.392(7)
0.59
3
+1.0
32.612(15)
0.32
2
+0.5
20.487(24)
2.0
3
-1.5
34.037(15)
0.03
873-871 (Nb) 873-884 (Ag)
2
-0.5
2.066(6)
0.44
3
- 1.5
88&87l(Nb)
2
88&889(k) 892-884
9.096(22)
0.02
ll.494(3)
0.04
-0.5
9.48 (4)
0.00
4
+ I.5
8.663(30)
0.02
2
+ I.5
8.099(10)
0.63
892-889(k)
5
- 1.5
3.498(15)
0.07
904-884
3
+1.5
19.384(6)
904_889(Sc)
5
-1.5
14.805(5)
1.44
904-927(Ta)
4
+1.0
23.917(12)
0.79
904-937
3
-1.5
33.419(6)
2.2
3
- I.5
12.85 (5)
0.10
3
+1.5
58.774(3)
0.56
3
-1.0
36.538(9)
0.12
4
+ 1.0
5.445 (5)
4
-1.0
3.031 (5)
2.8
10041044(Ta) ll28-112O(Sc) 1128-l 121 (Ta) I 128-l I73 (Co) 1140--1120(sc)
4
+1.0
39.685(10)
0.63
5
-2.0
8.009(S)
0.19
3
-1.0
7.265(22)
1.01
2
-2.0
44.664(14)
0.13
5
-2.0
20.167(R)
0.90
114~1173(c0) 1160_1173(Co) IIBB-I 173 (Co) 1241-1231 (Ta) 12461257 (Ta)
2
-2.0
32.529(17)
0.01
I
-2.0
12.87
I
+2.0
14.86 (4)
4
-15
10.36 (5)
1.39
4
+1.5
11.268(7)
0.85
127&-1332(Co)
2
-2.0
58.063(6)
0.28
127&1384
3
-2.0
109.865(4)
0.11
1290-1332(h)
I
-2.0
41.99
1397-1384
(Ag) (Ag)
3
+2.0
13.05 (5)
2.5
3
+2.5
l&260(9)
0.61
(Ag) (A& (As) (A@ (A@
3
-2.5
2
i2.5
10.992 (7) 32.77 (4) 24.50 (4) 20.02 (4) 34.193(17)
0.48 0.34 0.55 0.06 2.6
(Ag) (Ag)
(Ag)
924-937
(Ag) 996-937 (Ag) 996-959 (Ta) 996-1001 (Ta) 1004-1001 (Ta)
149&1475 14961505 1537-1505 1537-1562 1542-1562
1596-l 562
(Ag)
2
-2.5
2
-2.5
3
+2.5
0.93
2.6
(Xj
(IO)
-
-
R. G.
7x
HELMER
Relationships in the “‘Sb decay scheme can be used to test the assigned uncertainties, and to determine the energies of other 7 rays. To do this a least-squares fit to the energies of the levels at 35,443, 463. 636, 642 and 671 keV was carried out, and then the y-ray energies were computed from these level energies, The corrections for nuclear recoil are taken into account by the fitting program. The results of the calculations are given in column 6 of Table 4; they include energies for six y rays that were not measured directly. From these results it is concluded that the energies and their uncertainties are reasonable, since the only significant difference is for the 7 ray at 172 keV. Adopted or recommended energies are given in the last column of Table 4. From the energy differences in Table 3 and the known energies of the reference lines, several y-ray energies for i5“Eu have been computed and are given in Table 5. As discussed above, the uncertainties in the average values have not been allowed to be as small as the smallest value for an associated reference line. The decay scheme of ‘54E~ is very complex and involves about I50 7 rays. As for “‘Sb, one could use the measured energies and do a least-squares fit to some of the level energies and then deduce the energies for many of the other y rays. However, since there are many multiplets in this y-ray spectrum, the calculation of these values without a detailed study of the spectrum might be misleading. Therefore, a much simpler check of the consistency of our measurements has been made. As given in several footnotes to
Table 4. Measured
Lines 172-i 56 172.165 172-l 76 172-l 79
(Ta) (Ce) (Sb) (Ta)
176-165(G) l76-179(Ta)
3. Relative
Gamma-emission
;I-ray energw
for decay of “‘Sb
Difference (keV)
i-Ray energy (keV)
156.3874 (5) 165.857 (6) 179.313(l) 179.3948 (5)
16.325 (14) 6.860 (7) 3.601 (14) 6.682(16)
172.712(14) 172.717(9) 172.712(14) 172.713(16)
172 714(6)
165.857 (6) 179.3948 (5)
IO.459 (1) 3.082(l)
176 316(6) 176.313(l)
1763lill)
20&19X
(Ta)
198 3530 (6)
5.786 (8)
(Ta) (Sb) (Tb)
198.3530 (6) 204.139 (8) 222.1099 (6)
9.730(17) 3.939 (9) 14.029 (16)
427-433 443433 463433 600-569 600-614
(Ag) (Ag) (Ag) (Bi) (Ag)
433.936 433.936 433.936 569.702 614.281
(4) (4) (4) (2) (4)
6.063 9.618 29.428 30.899 13.681
606400 606-614 635-614 635461 671-661
(Sb) (Ag) (Ag) (Cs) (Cs)
600.601 614.281 614.281 661.660 661.660
(2) (4) (4) (3) (3)
6.1 17 (2) 7.564 (2) 21.669(l) 25.705 (I) 9.785 (3)
reference energies are from Helmer “‘Sb lines from this work.
(I ) (8) (I) (I) (I)
Average (keV)
Computed energy (keV)
Adopted energy (keV)
35.489 (5)
35.489 (5)
I72 723 (4)
17?.719(Xl
178.842 (5) 198.654 (I I )
176.313 (I) I78 842 (5) 198654(ll)
204 139(X) 208.083 (17) 208.078 (13~ 208.081 (16)
600.601 (2) 600.600 (4) 606.718 606.717 635.950 635.955
Probabilities
The results of an initial measurement of the relative ;I-emission rates were reported by Coursey et al. (I 982) at the time that the use of this mixed standard was proposed. Although other measurements have been made (see the evaluations in Tamura et ol., 1981; Helmer, l987), it would be desirable to have another such determination, so we have undertaken such a measurement. The efficiency of this detector was most recently calibrated in September 1987 and the “‘Sb and lS4Eu measurements were made in February and March 1988. All spectra involved were analyzed with the GAP program (Killian and Hartwell. 1988) on a VAX-750 computer. This program automatically finds peaks, defines a fixed linear background and the fitting range, and fits a Gaussian to the data points in the peak. The interpolated efficiency values were determined from the hand-drawn curves through the measured values. It is estimated that the uncertainty in the interpolated efficiency is 1% below 300 keV and 0.75% above that energy. See Helmer (1988) for more details concerning this efficiency determination. Due to the long time period between the efficiency calibration and the measurements, it is important to
Reference energy (keV)*
20X-198 208-204 208-222
*All
and computed
Table 5 a crossover y-ray energy is computed from the energies of the cascade y rays for comparison with the measured crossover y-ray energy. These comparisons indicate that these energies and uncertainties are quite consistent.
(3~ (4) (4) (3)
704 139 (8)
208 080 (9)
208.079 227.891 380.452 408.065
427.873 (5) 443.554 (9) 463.364 (5)
427.877 (4) 463 366 (4)
427.X75 (6) 443.554 (9) 463.365 (5)
600.601 (3)
600.599 (3)
600.600 (4)
(4) (IO) (8) (IO)
606.?18(3) 635.953 (4) 671.445 (4)
208.079 227.891 380.452 408.065
(4) (IO) (8) (IO)
606.71X (3) 635.955 (4) 671.444 (4)
er a/. (1979) except those for the lx9Ce line at 165 keV. which is from Helmer
635.954 (5) 67 I.445 (4) el ul. (1971) and the
Decay Table 5. Measured Reference energy (keV)*
Lines
of ‘25Sband
79
ls4Eu
~-ray ._ energies _ from the decav of lYEu Difference (keV)
Average (keV)
123-I 13 (Ta) 123-l I6 (Ta) 188-l 79 (Ta) 188-198 (Ta) 247-229 (Ta)
113.6723 (4) 116.4186(7) 179.3948 (5) 198.3530 (6) 229.3220 (9)
9.399 6.651 8.858 IO.101 18.605
247-264 401433 444433 444446 467446
264.0755 (8) 433.936 (4) 433.936 (4) 446.811 (3) 446.81 I (3)
16.145 (I) 32.678 (14) 10.557 16) 2.324 (7) 21.03 (5)
591&614(Ag) 625414 (Ag) 625420 (Ag) 625461 (Cs) 676-661 (Cs)
614.281 (4) 614.281 (4) 620.360 (3) 661.660(3) 66 I.660 (3)
22.519 (3) 10.971) (8) 4.982 (I 5) 36.403 (8) 14.938 (16)
625.251 (9) 625.342 (Is)? 625.257 (8) 676.598(16)
676-702 692461 692487 692-702 692-706
(Nb) (Cs) (Ag) (Nb) (Ag)
702.645 661.660 687.015 702.645 706.682
(6) (3) (3) (6) (3)
26.044 30.761 5.416 10.223 14.255
(I 3) (3) (4) (3) (3)
676.601 692.421 692.431 692.422 692.427
(14) (4) (5) (7) (4)
715-702(Nb) 715-706 (Ag) 723-706 (Ag) 723-744 (Ag) 756-744 (Ag)
702.645 706.682 706.682 744.277 744.277
(6) (3) (3) (3) (3)
13. I48 9.096 16.625 20.976 12.521
(20) (22) (2) (4) (4)
715.793 715.778 723.307 723.301 756.798
(21) (22) (4) (5) (5)
756-763 845-818 850-818 850-871 850-884
(Ag) (Ag) (Ag) (Nb) (Ag)
763.944 (3) 818.031 (4) 818.031 (4) 871.119(4) 884.685 (3)
7.136(3) 27.932 (7) 32.612(15) 20.487 (24) 34.037 (15)
850.643 (16) 850.632 (24) 850.648(15)
873-871 873-884 880-871 880-889 892-884
(Nb) (Ag) (Nb) (SC) (Ag)
X71.119(4) 884.685 (3) 871.119(4) 889.277 (3) 884.685 (3)
2.066 (6) Il.494 (3) 9.48 (4) 8.663 (30) 8.099 (IO)
873.185 (7) 873.191 (4) 880.60 (4) 880.614 (30) 892.784(10)
892-889 904884 904-889 904927 904-937
(SC) (Ag) (SC) (Ta) (Ag)
889.227 884.685 889.277 927.992 937.493
(3) (3) (3) (5) (4)
3.498 19.384 14.805 23.917 33.419
892.775 904.069 904.082 904.075 904.074
(15) (7) (6) (I 3) (7)
924-937 (Ag) 996-937 (Ag) 996-959 (Ta) 996-1001 (Ta) 1004-1001 (Ta)
937.493 937.493 959.730 1001.695 1001.695
(4) (4) (5) (5) (5)
12.85 (5) 55.774 (3) 36.538 (9) 5.445 (5) 3.031 (5)
996.267 996.268 996.250 1004.726
(5) (IO) (7) (7)
10041044(Ta) ll28-ll2O(Sc) Il28-II21 (Ta) 1128-l 173 (Co) 1140_1120(Sc)
1044.408 1120.545 1121.301 1173.238 1120.545
(5) (4) (5) (4) (4)
39.685 8.009 7.265 44.664 20.167
(IO) (8) (22) (14) (8)
1004.723 (I I) 1128.554 (9) 1128.566 (23) 1128.574(15) 1140.712(9)
1004.725 (7)‘
114&1173(c0) 116&l 173 (Co) 1188&1173(Co) 1241-1231 (Ta) 1246-1257 (Ta)
1173.238 (4) 1173.238 (4) 1173.238 (4) 1231.016(5) 1257.418 (5)
32.529 (17) 12.87 (8) 14.86 (4) 10.36 (5) I 1.268 (7)
1140.709 (17)
1140.71 I (9)” 1160.37 (8) Il88.10 (4) 1241.38 (5) 1246.150 (9)
127&1332 (Co) 12741384 (Ag) 129G-1332 (Co) l397-1384(Ag) 1494-1475 (Ag)
1332.502 1384.300 1332.502 1384.300 1475.788
(5) (4) (5) (4) (6)
58.063 (6) 109.865 (4) 41.99(10) 13.05 (5) 18.260 (9)
14941505 1537-1505 1537-l 562 1542-l 562 1596-l 562
1505.040 I505.040 1562.302 1562.302 1562.302
(5) (5) (5) (5) (5)
10.992 (7) 32.77 (4) 24.50 (4) 20.02 (4) 34.193 (7)
(Ta) (Ag) (Ag) (Ag) (Ag)
(Ag) (Ag) (Ag) (Ag) (Ag)
(I) (2) (8) (8) (I)
y-Ray energy (keV)
(I 5) (6) (5) (12) (6)
123.071 123.070 188.253 188.252 247.930
(I) (2) (8) (8) (I)
247.930 (I) 444.493 (7) 444.487 (8)
123.071 (I) 188.252 (8) 247.930 (I) 401.258 (14) 444.490 (6) 467.84 (5) 591.762 (5)
756.808 (4)
625.254 (7) 676.600 (12)
692.425 (4)f 715.786(18) 723.305 (5) 756.804 (5) 845.423 (8)
850.643 (I 2) 873.190(5) 880.61 (3) 892.781 (9)
904.076 (6) 924.64 (5)
1274.439 (8) 1274.435 (6)
996.262 (6%
1128.560 (8)
1274.436 (6)tt 1290.51 (IO) 1397.35 (5)
1494.048 (I I) 1494.048 (9) 1537.81 (4) 1537.80 (4)
1494.048 (9):t 1537.80 (4) 1542.28 (4) 1596.495 (l8H
*All values are from Helmer er al. (1979) except those for the ‘“‘Ta lines at 927, 959, 1001, and 1044 keV which were computed from the values in Helmer et al. (1979) and the decay scheme. tValue not used in average. fFrom 247 + 444 sum, computed energy is 692.419 (6) keV. §From 123 + 873 sum, computed energy is 996.260 (5) keV. q/From 247 + 756 sum, computed energy is 1004.733 (5) keV. **From 247 + 892 sum, computed energy is 1140.709 (9) keV. ttFrom 401 + 873 sum, computed energy is 1274.446(15) keV. IfFrom 247 + 1246 sum, computed energy is 1494.078 (4) keV. @From 591 + 1004,692 + 904 and 723 + 873 sums, the average computed energy is 1596.491 (5) keV.
80
R. G.
HELMER
coincidence summing (from KORSUM computer code, Debertin and Schotzig, 1979) and the detector efficiencies are also given there. Due to the very low count rate the random summing or pile-up correction, which would be -0.1% for all peaks, is neglected. The resulting relative y-emission probabilities are given in column 5. The components in the quoted uncertainties are as follows. That for the peak area is shown with the average area. For the coincidence summing, it is taken as 20% of the correction (i.e. 20% of the factor shown minus 1.0). As noted above, for the efficiency the uncertainty is 1.0% below 300 keV and 0.75% above there. The results in the 1981 Nuclear Data Sheets evaluation (Tamura et al., 1981) and the subsequent measurements of Coursey er al. (1982) Iwata et al. (1984) and this work are generally in agreement.
have an estimate of the possible change in the efficiency. This has been monitored by monthly measurements with a source of “‘Eu [t,:2 = 4933(11) days]. We estimated that variations in any peak area of 0.14.2% are to be expected from variations in the fitting process. This is especially true since the low-energy tailing on the peak is not taken into account in the peak-shape function. The results (Helmer, 1988) are then consistent with no change in the efficiency curve over the time period of interest. For “‘Sb four spectra were measured at a count rate of 72 s-’ for durations of 20,000-55,000 s. This gave 1.2 x 10’ to 3.4 x IO5 counts in the peak at 427 keV. For each y ray, the average peak area, relative to that of the 427-keV peak, was determined as an unweighted average. These results are given in Table 6. The calculated correction factors for Table ;’ Energy (keV) 116.6 172.7 176.3 204.1 20x.1
6. “%b
relative
.J-emission
Coincidence summing corrections
Relative peak area I899 (48) 1345 (19) 46.661 (I 19) 2026 (39) I538(26)
probabilities Efficiency (I x IO’)
1.0106 I .0078 I .0034 1.0107 I .0078
3.70 3.44 3.41 3.17 3 I4
Relative ;,-emission probability 8.67 (24) 6.59(11) 229.6 (24) 10.80 (23) 8.25(16)
227.9 321.1 380.5 408.1 421.9
776 1809 5704 655 = 100.000
(40) (38) (30) (19)
1.0071 I .00X7 I .003l I .0055 I.0017
2.95 2.17 I.861 I .749 I .675
4.43 (23) 14.1 (3) 51.4(5) 6.30(19) = 1000.(8)
443.6 463.4 600.6 606.7 636.0
985 32,743 44.069 12,358 26.687
(27) (SO) (67) (42) (74)
I .003x 0.9999 1.0016 1.0016 1.0015
I.622 I.561 I .249 I .239 I.191
IO.19 (29) 350.7 (28) 590.9 (45) 167.0(14) 357.2 (30)
4122 (22)
0.9993
I. I 39
60.5 (6)
671.4
Table y Energy (keVI
7. lS4Eu relative
Relative txak area
y-emwmn
Coincidence summing corrections
probabilities Efficiency (f x 102)
Relative y-emission probability
123.1 188.3 248.0 401.3 444.5
642,436 (I 150) 3193(13) 79,426 (I 15) l428(10) 3809(17)
I .0062 I.0191 1.0143 I .0095 I .02Ol
3.70 3.315 2.72 I .772 1.620
ll65(12) 6.55 (7) 198 (2) 5.43 (6) 16.00(15)
478.3 557.6 582.1 591.8 692.6
1454(g) 1525(19) 4826 (6) 26,573 (24) X378 (24)
I .0083 I .Ol67 I.0135 1.0143 I.0114
I.518 I.329 I.283 I.265 I.1 IO
6.44 (6) 7.78(11) 25.43 (2!) 142.! (I I) 50.9 (4)
723.4 756.8 815.6 845.4 873.2
9 1,092 (94) 19.771 (28) 2135(ll) 2418 (20) 47.212 (32)
I .0095 1.0162 0.989X I.0133 I.0125
1.071 I.032 0.969 0.941 0.916
573 (4) 129.9(11) 14.55 (14) 17.37 (20) 348. I (ZS)]
904. I 996.3 1004.8 1128.5 1140.8
3341 (IO) 36,681 (35) 62,570 (59) 1050(14) 739 (7)
I.0130 I .0004 I .0079 I .0081 I .0008
0.890 0.822 0.816 0.742 G.735
25.37 (22) 297.8 (23) 515.5 (40) 9.52(15) 6.71 (8)
1.0148 I .0074 I .0040 0.9917
0.684 0.672 0.591 0.560
24.49 (23) = 1000.0 19.79 (16) 50.78 (40)
1245.8 1274.5 1493.8 1596.6
2475(ll) - I00,000 I746 (4) 4299 (8)
Decay
of lz5Sb and ‘54E~
Similar measurements were carried out for “IEu. Two sources were used and they gave count rates of 1590 SC’ and 3970 s-‘. The source material was prepared in 1976 by isotope separation at the INEL. A common impurity in ls4Eu samples is is2Eu. From the peak at 1408 keV, the measured spectra indicated that the ‘52E~ content was such that - 0.1% of the peak at 122 keV, the major interference, was due to 152E~. Thus, any interference is negligible. The 15“Eu spectra were measured for periods of 12,00(~50,000 s and the 1274-keV peak had areas of 4.5 x 10’ to 4.6 x lo6 counts. At these count rates the corrections for random summing (pile-up) range from 2.6 to 7.3%. However, we report the y-emission probabilities relative to that of the 1274-keV y ray. Therefore, only the variation of this correction with the y-ray energy needs to be taken into account. This variation is only 0.4% for the weaker source and 1.0% for the stronger one. Four spectra were measured for each source. For each 7 ray the four peak areas, relative to that of the 1274-keV line, were averaged and corresponding uncertainty calculated. After correcting each average for random summing, a weighted (by c-2) average of the two values was computed. These values, the calculated coincidence summing correction factors, and the interpolated detector efficiencies are given in Table 7. The resulting relative y-ray emission probabilities are given in column 5 of this table. The
81
uncertainties have been computed as discussed above for iz5Sb. The results of this work and those summarized in the 1987 Nuclear Data Sheets evaluation (Helmer, 1987) generally agree well. Acknowledgement-We wish to thank R. A. Anderl for providing the isotope separated sample of 15”Eu. This work was supported by the U.S. Department of Energy under DOE (Contract No. DE-AC07-76IDOl570.
References Coursey, B. M., Hoppes D. D. and Schima F. J. (1982) Nuci. Instrum. Methods 193, 1. Debertin K. and Schiitzig U. (1979) Nucl. Instrum. Methods 158, 471. Greenwood R. C., Helmer R. G. and Gehrke R. J. (1970) Nucl. Instrum. Methods ?I, 141. Helmer R. G. (1987) Nucl. Data Sheets 52. 1. Helmer R. G. (1988) Report EGG-PHY-8250. Helmer R. G., Greenwood R. C. and Gehrke R. J. (1971) Nucf. Instrum. Methods 96, 173. Helmer R. G., Gehrke R. J. and Greenwood R. C. (1975) Nucl. Instrum. Methods 123, 51. Helmer R. G., Van Assche P..H. M. and van der Leun C. (1979) AI. Data Nucl. Dala Tables 24, 39. Iwata Y., Yasuhara M., Moeda K. and Yoshizawa Y. (1984) Nucl. Instrum. Methods 219, 123. Some of the ‘54E~ data in this article come from Yoshizawa Y., Iwata Y. and Iinuma Y. (1980) Nucl. Instrum. Methods 174, 133. Killian E. W. and Hartwell J. K. (1988) Report EGG-2533. Tamura T., Matumoto Z. and Ohshima M. (1981) Nucl. Data Sheets 32, 497.