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Relative intensities of 860 to 2130 keV Ir194 γ-lines
Nuclear Physics 41 (1963) 669---674; (~) North-Holland Publishing Co., Amsterdam Not to be reproduced by photoprint or microfilm without wwitten permissioa from the publisher
R E L A T I V E I N T E N S I T I E S OF 860 T O 2130 keV Ir 194 y-LINES V. D. V I T M A N , N. A. V O I N O V A a n d B. S. D ~ E L E P O V
D. 1 Mendeleyev Metrology Research Institute and
Physical-Technical Institute of the USSR Academy of Sciences, Leningrad, USSR Received 6 July 1962
Abstract: T h e 7-spectrurn o f Ir x94 is investigated with a y-spectrometer using magnetic analysis o f recoil electrons (elotron). A n u n k n o w n 7-line hv = 1569 keV is detected. Relative intensities o f 23 7-lines are determined.
Multipolarities are given for some transitions. The Ir 194 y-spectrum has been investigated most thoroughly by Johns and Nablo 1) and by Kern and B~ickstrSm 2). In refs. 1, 2) the relative intensities of y-lines are obtained in the investigation of the photoelectron spectrum with a double-focusing spectrometer. The results for some lines differ by a factor of 1.5 to 2. This investigation aims at obtaining more accurate relative intensities of y-lines with an elotron which has the advantage of very low background and a well-known spectral sensitivity. The source was a powder of spectrally pure Ir activated by neutrons in a PTI reactor beam 5.1013 to 1014 neutrons/cm 2. sec. To obtain uniform irradiation throughout the thickness of the source, 2 to 2.2 g of Ir powder were mixed with 1.3 g of graphite, and the mixture was placed into an aluminium case (9 m m in diameter, 41 mm long and 1 m m thick in its wall). Four sources with a strength of 20 to 30 Cur were made. Figs. 1-4 represent the experimental recoil electron spectrum and its analysis into components taking into account the instrumental line shape. From 860 to 2130 keV the spectrum reveals 23 y-lines of which the 1569 keV transition has been detected for the first time. The intensity of this line decreases with a period of 1 8 + 4 h, which confirms its assignment to Ir 194. In refs. 1, 2) this y-line was not detected probably because the 1569 keV K-line coincides with the L-line of the 1469 keV y-transition which is 10 times as intense (for a uranium target). A conversion line corresponding to the 1563 keV y-transition 3) was observed in the conversion spectrum of A u 194 decaying with the capture of electrons into Pt! 94, i.e., into the same nucleus into which Ir 194 decays. Perhaps the y-line we have detected corresponds to the same y-transition. A peak in the region of 1800 keV is produced by several close lines. According to 669
v.D.
670
VITMAN e t
aL
ref. 2), this region contains four y-lines hv = 1784.0, 1798.0, 1805.1 and 1807.5 keV. W e can represent this peak as the s u m o f t w o ~-lines: hv = 1786 and 1808 keV. It~9
1!721183
15 925 YS] 10
'
"
i i
5l
/ iI~;d
t'J~!
i
•
f104
/
;
i
!/ ~,)0
zdOfJ
6400
5200
Hf
Fig. h The Ir194 ~,-spectrum in the energy interval of 860 to 1400 keV.
[
Mcoin.
I~G
tSO~
L
min "t .o
54OO
680o
A
R~
Fig. 2. The IrT M ),-spectrum in the energy interval of 1400 to 1700 keV. W e could not obtain a unique analysis taking into account the four lines. Table 1 represents the energies and relative intensities o f the Ir t94 y-lines in comparison with the results o f refs. 1, 2). The 1149 keV line intensity is put equal to 100 and
RFLAIlVE
671
I N T E N S I T I E S OF 1i 194 y - L I N E S
the data of refs. ~' 2) are recalculated according to this normalization. The table shows that our relative intensities are in somewhat better agreement with the results of ref. 1) than ref. 2). The discrepancy between our results and those of ref. 2) is systematic which is clear from fig. 5. For energies higher than 1200 keV it amounts to 70 ~ . The spectral sensitivity of our instrument in the interval of 1150 to 2150 keV I A/co;n. ~,i,r -I
1~60
8
/
2
!
s~oe
58oo
6200
lip
Fig. 3. T h e Ir l x y - s p e c t r u m in the energy interval o f 1700 to 1900 keV.
06
t9~
2t3~4
2113
?
[1.2
!
i 7000
T 7/'00
7800
T • "
~He
Fig. 4. The Ir I°4 y-spectrum in the energy interval of 1900 to 2130 keV.
is known accurately to within 4~o; therefore we believe that the discrepancy results from systematic errors in the experiments of ref. 2). Besides, it seems to us that the errors in determinmg line intensities are somewhat underestimated in ref. 2): thus, the intensity of the line hv = 1294 keV is given to within 10Yo error. However, the line itself is masked by the adjacent lines and is only 8 ~o of the background after
672
v . D. V l r M A N et al.
TABLE 1
Relative intensities of Ir TM 7-lines Johns and Nablo l) E~,
100 J~'/J1149
937.4--0.4
100
1149.24-0.6
100
1180 -t-1 1216 -i-1
59 14
1339 4-2
10
1466 4-1
28
1478 .l-I 1507 --2
7 10
1618 --2 1662 --3
10 7
1802 -3_2
10
2048 4-4
1.7
Kern and BhckstrOm z) E~, 890.34-0.3 924.7±0.8 938.94-0.1 1000.65:0.4 1048.34-0.7 1104.54-0.7 1151.3--'___0.3 1176.14-0.6 1184.1.0.4 1219.44-0.5 1294.1±0.7 1343.04-0.7 1430.54-3 1469.5±0.5 1480.25:0.7 1488.04-0.9 1512.44-0.5 1622.84-0.6 1670.94-0.6 1784.04-3 1798.05:2 1805.14-2 1807.54-1.5 1832.0---3 1925.94-2 2044.1 4-0.8 2115.5 4-1.5
100 J~'/.f 1151 6.5 5.5 93 5.2 4.6 3.8 100 10.3 50 21.7 16.6 6.9 1.4 59
±0.7 4-0.7 q-3 ±1.0 4-0.3 4-0.3 4-3 4-1.7 +3 ±1.7 4-1.7 4-1.0 ~0.7 4-3 < 2 5.5 z::l.0 11.4 4-1.7 15.2 5:1.0 2.1 ±0.3 1.6 4-0.5 3.8 +0.7 3.8 4-0.7 5.9 ~0.7 0.554-0.17 0.764-0.3 1.414-0.07 0.594-0.07
Our data E~,
100J~'/.~t 149
8894-2 925 9374-2 10004-2 10474-2 11044-2 11494- 2 11724-3 11834-2 12154-3 1292_-'3 13436-3
13 4-3 ~ 6 95 4-5 8.6 4-1.4 5.4 4-_1.0 4.4 4-0.8 100 13 4-4 48 4-3 9.0 4-1.3 8.1 4-1.6 7.1 4-0.9
1469-- 2
31.2 -i 1.6
14904-4 1513±3 15694-3 1622--3 16694-4 1786±4
3.4 6.3 3.6 10.4 0.8 2.1
4-0.9 4-1.0 -;-0.6 ±1.2 4-0.3 --'0.8
1808±3
7.3 4-1.0
1930±4 2044--4 2118+4
0.37-4-0.11 1.0 4-0.2 0.5 4-0.2
the graphical separation. N o t h i n g is said in ref. 2) concerning the error in the spectral sensitivity when employing the photoelectron method u n d e r the conditions o f the experiments in question, b u t there are indications in other papers 4,s) that this sensitivity may be k n o w n accurately to within 5 to 8 ~ . Since the ),-line relative intensities seem to be erroneous in ref. 2), the transition multipolarities given in table 4 of the same paper must also be revised. Using our relative intensities of ),-lines a n d the conversion electron intensities o f ref. a), we o b t a i n e d the conversion coefficients for the transitions from the 1671, 1622 a n d 1512 keV levels to the two Pt 194 levels with energies 328 a n d 622 keV a n d spin a n d parity 2 + . The conversion coefficients were calculated u n d e r the a s s u m p t i o n that the g r o u n d state transitions from the 1671, 1622 a n d 1512 keV levels are of the E2 type. O u r values of the transition multipolarities are given in table 2. The multipolarities o f the transitions from the 1671 a n d 1512 keV levels to the low 2 + levels are of the
673
RELATIVE INTENSITIES OF' l r 19¢ ~,-LINES
type E 2 + M I . The conversion coefficients of,the corresponding transitions from the 1622 keV level are large. Probably, these transitions contain a considerable admixture o f E0.
z'
1 ....
!_
: 800
i
J
i~O0
I
'
t600
~000
'
b~ 0 ~eV
Fig. 5. T h e ratio o f o u r },-line intensities to those o f ref. z). T h e point at hv = 1800 keV c o r r e s p o n d s to the ratio o f the intensities o f a group o f poorly resolved lines, 1786 a n d 1808 keV according to o u r data a n d 1784, 1798, 1805 a n d 1807.5 keV according to the d a t a o f ref. 3).
TABLE 2 Multipolarities o f s o m e Ir 194 y-transitions Level energy (keV) 1671
1622
1512
Transition energy (keV) 1671 1343 1048 1622 1293 1000 1512 1184 890
Conversion coefficients 10s Experimental
Theoretical E2
1.75 3.5 ± 1.4 5.0 q- 2.1
1.83 13.0+3.0 9.8+2.0 2.06 3.64-0.6 5.9 ~ 1.7
1.75 2.6 4.2 1.83 2.8 4.5 2.06 3.25 5.6
....
Transition multipolarity
M1 3.0 5.2 9.9
3.2 5.7 11.3 3.8 7.2 14.7
E2 E2+ M 1 E2+ M 1 E2 E 2 + MI -:-E0 E2 t- M1 z- (E0) E2 E 2 + (M 1) E2 + (M 1)
674
v.D. VrrMAN et
al.
The a u t h o r s are indebted to Yu. P. Saikov a n d A. N. T i m o k h i n , associates of the P T I branch, for assistance in o b t a i n i n g the sources as well as to A. Vatai, a graduate s t u d e n t of the Leningrad State University, for his participation in the measurements.
References 1) 2) 3) 4) 5)
H. Johns and S. Nablo, Phys. Rev. 96 (1954) 1599 J. Kern and G. B~ickstr6m, Nuclear Physics 19 (1960) 461 G. B~iekstr6m, O. Bergman, J. Burde and J. Lindskog, Nuclear Physics 15 (1960) 566 M. Mladjenovi(3,Nucl. Instr. 10 (1961) I E. P. Grigoriyev and A. V. Zolotavin, Nucl. Instr. 7 (1960) 289
R E L A T I V E I N T E N S I T I E S OF 860 T O 2130 keV Ir 194 y-LINES V. D. V I T M A N , N. A. V O I N O V A a n d B. S. D ~ E L E P O V
D. 1 Mendeleyev Metrology Research Institute and
Physical-Technical Institute of the USSR Academy of Sciences, Leningrad, USSR Received 6 July 1962
Abstract: T h e 7-spectrurn o f Ir x94 is investigated with a y-spectrometer using magnetic analysis o f recoil electrons (elotron). A n u n k n o w n 7-line hv = 1569 keV is detected. Relative intensities o f 23 7-lines are determined.
Multipolarities are given for some transitions. The Ir 194 y-spectrum has been investigated most thoroughly by Johns and Nablo 1) and by Kern and B~ickstrSm 2). In refs. 1, 2) the relative intensities of y-lines are obtained in the investigation of the photoelectron spectrum with a double-focusing spectrometer. The results for some lines differ by a factor of 1.5 to 2. This investigation aims at obtaining more accurate relative intensities of y-lines with an elotron which has the advantage of very low background and a well-known spectral sensitivity. The source was a powder of spectrally pure Ir activated by neutrons in a PTI reactor beam 5.1013 to 1014 neutrons/cm 2. sec. To obtain uniform irradiation throughout the thickness of the source, 2 to 2.2 g of Ir powder were mixed with 1.3 g of graphite, and the mixture was placed into an aluminium case (9 m m in diameter, 41 mm long and 1 m m thick in its wall). Four sources with a strength of 20 to 30 Cur were made. Figs. 1-4 represent the experimental recoil electron spectrum and its analysis into components taking into account the instrumental line shape. From 860 to 2130 keV the spectrum reveals 23 y-lines of which the 1569 keV transition has been detected for the first time. The intensity of this line decreases with a period of 1 8 + 4 h, which confirms its assignment to Ir 194. In refs. 1, 2) this y-line was not detected probably because the 1569 keV K-line coincides with the L-line of the 1469 keV y-transition which is 10 times as intense (for a uranium target). A conversion line corresponding to the 1563 keV y-transition 3) was observed in the conversion spectrum of A u 194 decaying with the capture of electrons into Pt! 94, i.e., into the same nucleus into which Ir 194 decays. Perhaps the y-line we have detected corresponds to the same y-transition. A peak in the region of 1800 keV is produced by several close lines. According to 669
v.D.
670
VITMAN e t
aL
ref. 2), this region contains four y-lines hv = 1784.0, 1798.0, 1805.1 and 1807.5 keV. W e can represent this peak as the s u m o f t w o ~-lines: hv = 1786 and 1808 keV. It~9
1!721183
15 925 YS] 10
'
"
i i
5l
/ iI~;d
t'J~!
i
•
f104
/
;
i
!/ ~,)0
zdOfJ
6400
5200
Hf
Fig. h The Ir194 ~,-spectrum in the energy interval of 860 to 1400 keV.
[
Mcoin.
I~G
tSO~
L
min "t .o
54OO
680o
A
R~
Fig. 2. The IrT M ),-spectrum in the energy interval of 1400 to 1700 keV. W e could not obtain a unique analysis taking into account the four lines. Table 1 represents the energies and relative intensities o f the Ir t94 y-lines in comparison with the results o f refs. 1, 2). The 1149 keV line intensity is put equal to 100 and
RFLAIlVE
671
I N T E N S I T I E S OF 1i 194 y - L I N E S
the data of refs. ~' 2) are recalculated according to this normalization. The table shows that our relative intensities are in somewhat better agreement with the results of ref. 1) than ref. 2). The discrepancy between our results and those of ref. 2) is systematic which is clear from fig. 5. For energies higher than 1200 keV it amounts to 70 ~ . The spectral sensitivity of our instrument in the interval of 1150 to 2150 keV I A/co;n. ~,i,r -I
1~60
8
/
2
!
s~oe
58oo
6200
lip
Fig. 3. T h e Ir l x y - s p e c t r u m in the energy interval o f 1700 to 1900 keV.
06
t9~
2t3~4
2113
?
[1.2
!
i 7000
T 7/'00
7800
T • "
~He
Fig. 4. The Ir I°4 y-spectrum in the energy interval of 1900 to 2130 keV.
is known accurately to within 4~o; therefore we believe that the discrepancy results from systematic errors in the experiments of ref. 2). Besides, it seems to us that the errors in determinmg line intensities are somewhat underestimated in ref. 2): thus, the intensity of the line hv = 1294 keV is given to within 10Yo error. However, the line itself is masked by the adjacent lines and is only 8 ~o of the background after
672
v . D. V l r M A N et al.
TABLE 1
Relative intensities of Ir TM 7-lines Johns and Nablo l) E~,
100 J~'/J1149
937.4--0.4
100
1149.24-0.6
100
1180 -t-1 1216 -i-1
59 14
1339 4-2
10
1466 4-1
28
1478 .l-I 1507 --2
7 10
1618 --2 1662 --3
10 7
1802 -3_2
10
2048 4-4
1.7
Kern and BhckstrOm z) E~, 890.34-0.3 924.7±0.8 938.94-0.1 1000.65:0.4 1048.34-0.7 1104.54-0.7 1151.3--'___0.3 1176.14-0.6 1184.1.0.4 1219.44-0.5 1294.1±0.7 1343.04-0.7 1430.54-3 1469.5±0.5 1480.25:0.7 1488.04-0.9 1512.44-0.5 1622.84-0.6 1670.94-0.6 1784.04-3 1798.05:2 1805.14-2 1807.54-1.5 1832.0---3 1925.94-2 2044.1 4-0.8 2115.5 4-1.5
100 J~'/.f 1151 6.5 5.5 93 5.2 4.6 3.8 100 10.3 50 21.7 16.6 6.9 1.4 59
±0.7 4-0.7 q-3 ±1.0 4-0.3 4-0.3 4-3 4-1.7 +3 ±1.7 4-1.7 4-1.0 ~0.7 4-3 < 2 5.5 z::l.0 11.4 4-1.7 15.2 5:1.0 2.1 ±0.3 1.6 4-0.5 3.8 +0.7 3.8 4-0.7 5.9 ~0.7 0.554-0.17 0.764-0.3 1.414-0.07 0.594-0.07
Our data E~,
100J~'/.~t 149
8894-2 925 9374-2 10004-2 10474-2 11044-2 11494- 2 11724-3 11834-2 12154-3 1292_-'3 13436-3
13 4-3 ~ 6 95 4-5 8.6 4-1.4 5.4 4-_1.0 4.4 4-0.8 100 13 4-4 48 4-3 9.0 4-1.3 8.1 4-1.6 7.1 4-0.9
1469-- 2
31.2 -i 1.6
14904-4 1513±3 15694-3 1622--3 16694-4 1786±4
3.4 6.3 3.6 10.4 0.8 2.1
4-0.9 4-1.0 -;-0.6 ±1.2 4-0.3 --'0.8
1808±3
7.3 4-1.0
1930±4 2044--4 2118+4
0.37-4-0.11 1.0 4-0.2 0.5 4-0.2
the graphical separation. N o t h i n g is said in ref. 2) concerning the error in the spectral sensitivity when employing the photoelectron method u n d e r the conditions o f the experiments in question, b u t there are indications in other papers 4,s) that this sensitivity may be k n o w n accurately to within 5 to 8 ~ . Since the ),-line relative intensities seem to be erroneous in ref. 2), the transition multipolarities given in table 4 of the same paper must also be revised. Using our relative intensities of ),-lines a n d the conversion electron intensities o f ref. a), we o b t a i n e d the conversion coefficients for the transitions from the 1671, 1622 a n d 1512 keV levels to the two Pt 194 levels with energies 328 a n d 622 keV a n d spin a n d parity 2 + . The conversion coefficients were calculated u n d e r the a s s u m p t i o n that the g r o u n d state transitions from the 1671, 1622 a n d 1512 keV levels are of the E2 type. O u r values of the transition multipolarities are given in table 2. The multipolarities o f the transitions from the 1671 a n d 1512 keV levels to the low 2 + levels are of the
673
RELATIVE INTENSITIES OF' l r 19¢ ~,-LINES
type E 2 + M I . The conversion coefficients of,the corresponding transitions from the 1622 keV level are large. Probably, these transitions contain a considerable admixture o f E0.
z'
1 ....
!_
: 800
i
J
i~O0
I
'
t600
~000
'
b~ 0 ~eV
Fig. 5. T h e ratio o f o u r },-line intensities to those o f ref. z). T h e point at hv = 1800 keV c o r r e s p o n d s to the ratio o f the intensities o f a group o f poorly resolved lines, 1786 a n d 1808 keV according to o u r data a n d 1784, 1798, 1805 a n d 1807.5 keV according to the d a t a o f ref. 3).
TABLE 2 Multipolarities o f s o m e Ir 194 y-transitions Level energy (keV) 1671
1622
1512
Transition energy (keV) 1671 1343 1048 1622 1293 1000 1512 1184 890
Conversion coefficients 10s Experimental
Theoretical E2
1.75 3.5 ± 1.4 5.0 q- 2.1
1.83 13.0+3.0 9.8+2.0 2.06 3.64-0.6 5.9 ~ 1.7
1.75 2.6 4.2 1.83 2.8 4.5 2.06 3.25 5.6
....
Transition multipolarity
M1 3.0 5.2 9.9
3.2 5.7 11.3 3.8 7.2 14.7
E2 E2+ M 1 E2+ M 1 E2 E 2 + MI -:-E0 E2 t- M1 z- (E0) E2 E 2 + (M 1) E2 + (M 1)
674
v.D. VrrMAN et
al.
The a u t h o r s are indebted to Yu. P. Saikov a n d A. N. T i m o k h i n , associates of the P T I branch, for assistance in o b t a i n i n g the sources as well as to A. Vatai, a graduate s t u d e n t of the Leningrad State University, for his participation in the measurements.
References 1) 2) 3) 4) 5)
H. Johns and S. Nablo, Phys. Rev. 96 (1954) 1599 J. Kern and G. B~ickstr6m, Nuclear Physics 19 (1960) 461 G. B~iekstr6m, O. Bergman, J. Burde and J. Lindskog, Nuclear Physics 15 (1960) 566 M. Mladjenovi(3,Nucl. Instr. 10 (1961) I E. P. Grigoriyev and A. V. Zolotavin, Nucl. Instr. 7 (1960) 289