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The electron capture decay of 195Au
Goedbloed, Kemper, Blok,
Physica
W.
Mast enbroek,
30
204 L-2050
Em
A,
J.
1964
THE ELECTRON by W. GOEDBLOED,
CAPTURE
DECAY
E. MASTENBROEK, J. BLOK
Vrije Universiteit,
Amsterdam,
OF lg5Au
A. KEMPER
and
Nederland
Synopsis This paper A gamma The
deals with
radiation
transition
energy
QT =‘: 226 & 2 and Branching
ratios,
measurements
of 210 keV
on the electron
has been observed
is obtained
from
KX-gamma
capture
decay
of 1g5Au-1g5Pt.
that was not reported and
LX-gamma
previously. coincidences,
QT = 229 & 1 respectively.
relative
intensities
and conversion
coefficients
are given.
1. Introduction. It is possible to study the levels of 195Pt by means of: Coulomb excitation, the beta decay of 195Ir, the decay of the metastable 13/Z level and the electron capture decay of 195Au. Extensive Coulomb excitation measurements by several investigators3)5)6) indicate excited states at 99, 130, 210 and 240 keV and gamma radiations of 31, 99, 130, 140, 210 and 240 keV. Bernstein and Lewisd), by virtue of the excitation function of the 99 keV gamma radiation, suggest a first excited state at 31 keV, but Stelson and McGowans), discussing the excitation functions of the 99, 130, 140,210 and 240 keV gamma radiations, reject this suggestion; they propose the level scheme given in fig. 2. This scheme was extended by B arlo ut aud6) with levels at 420 and 720 keV. About the beta decay of the short living 195Ir only few data are known; Claf lin e,a. 9) reported gammas of 190 and 290 keV in coincidence and gave a half-life of 4.2 h. De Shalit and co-workersl) demonstrated a metastable &3/z state of 255 keV and Tl,z = 3.8 d; th eir conversion electron study of the electron capture decay of 19%4u and of the decay of this 195Ptm resulted in a level scheme which is given in figure 1. In a rather poor experiment with a proportional counter containing an argon-methane mixture, B isi and Zap-Paz) determined the ratio (pL/pK)129 = 0.58 & 0.14 and hence a total transition energy: QT = (272 & 17) keV; however, a few years later*) using scintillation methods, they corrected these values: (PL/pK)129 = = 5.5 -& 0.9 and QT = 235 keV. The present work is intended to examine the electron capture decay of 195Au with the help of proportional counters and scintillation spectrometers ; .
-
2041
-
2042
W.
GOEDBLOED,
Is. MASTENBROEK, -~__.-^-_-
A. KEMPER
in doing so we hope to give more accurate results tensities, capture ratios and transition energies, T = 3 8d l
ANI> Ja BLOK
about
gamma
ray in-
i13’2 /255
lteV T=180d
keV /
I
97
240
keV
5'2
3/2
130
f -10%)
1
"2
0
lg5Pt
Fig. 2. Level
diagram
of lW?t
from
C’doml-I
McGr)w;ttl
excitation
measurements
as given
by
and Stclsc,l~.
2. Ex @rimen tal procedure. The lg5Au activity was produced by irradiation of Pt with deuterons in the cyclotron of the “Instituut voor Kernphysisch Onderzoek” in Amsterdam. NaI scintillation counters of I + x 1&-in. counters containing an 1g X g-in, 18 X $-in, 14 x &-in and proportional argon-methane, a krypton-methane or a xenon-methane mixture were used
THE
for the measurements
ELECTRON
CAPTURE
DECAY
OF
195Au
of the X rays and the gamma radiations.
2043 Data about
the proportional counters were given previouslyll). For detections in the low energy range (up to 80 keV), we employed either one of the proportional counters or a 1; x $-in NaI crystal with 0.001 -in Al cover. The single count scintillation and the single count proportional counter spectra were analysed; a description of this analysis is given in section 3. ,4dditional information of the was obtained by coincidence experiments ; several combinations detectors, mentioned at the beginning of this section, were used to measure the KX-gamma, LX-gamma and gamma-gamma coincidences. All spectra were recorded with a RCL 512-channel analyser. A l& x l&-in NaI crystal in combination with a 3. Single cm.& sjbectra. set of tin absorbers (0.1, 0.5, 1 .O and 1.5 mm) was used to determine the relative intensities of the radiations involved, Figure 3 demonstrates the difference between two of these gamma ray scintillation spectra, one of them with an absorber of 0.26 cm tin, the other without any absorber. 4nalysis of the spectra revealed peaks at 35, 70, 99, 129 and 210 keV, the peak at 35 keV was a composite one of the KX-escape (about 38 keV) and the SO keV gamma radiations, the 70 keV is composed of the KX and 99escape radiations, while the 99, 129 and 210 kcV are gamma radiations, of 10"
I
I
1
I
N
t
to5
to4
50
250
150 -
CHANNEL
Fig. 3. Single
count
NUMBER
scintillation
a)
no absorber
b)
0.24 cm tin absorber.
spectra.
whicll the 210 keV was not reported before. In verifying the assumption of a 210 keV gamma radiation appearing in the electron capture decay of %4u, we u.sed absorbers of various thickness and different source to crystal
2044
W,
GOEDBLOED,
E. MASTENBROEK,
A. KEMPER
AXD
J. BLOK
-_- ---_
_
distances to reduce summation effects and to determine the relative intensity with regard to the 99 keV photopeak; we followed the counting rates of the 99, 129, and the 210 photopeaks for over a year to compare their half-lives. All these experiments supported our assumption, The proportional counters were very useful for the examination of the low-energetic 30 keV, LX and KX radiations. The krypton filled counter had a copper wall which gave rise to peculiar difficulties; thanks to the copper KX-radiation (about 8 keV) - stimulated by absorption of photons in this wall - part of the 30 keV gamma ray yield is found in the summation peak at 38 keV, so in this case it is necessary to read for the 30 keV gamma intensity appearing in the formulas 1 and 5 of section 4 the sum of the yields at 30 and 38 keV (see fig. 4). The argon and xenon counters had an aluminium wall, so the complications iust mentioned did not occur with these.
KnX
102
- QSC. I
50
150
A
Fig. 4. Spectrum
I
I
I
I
CHANNEL
250
NUMBER
of the krypton-methane counter showing the 38 keV summation peak,
;;t.o. the
30 ke\’ peak
and
Using the decay scheme as given 4. Experimenfal results. a. Formulae. in figure 6 one can derive the following relations: 1.
130
=
2.
199
=
NQ130E30 f + q&730
a30 + 1 +
3.
1129
=
NP7129E129 1 + ,129
; 999) a99
;
&99 ;
THE
4.
ELECTRON
9.
DECAY
OF
2045
195Au
~qm~21o -Pm
I 210 =
T +
,210
’ 99 fiK
IK-30 5 . ----.J30
6.
CAPTURE
k-99 -‘I99
=
__IK-K
2mK&K z _____
~30p~g+~99pg
coK&K
4730 +
IK-99
-
a99
1-t
&K&K
.
mE9(1
(1 + ,I29
899
;
> ’
q99
tip +
--
+
1.
plS9 cp129 K
agg)
)(y3dy9
+
%
J
Q799PF)
ag
129
10,
IK = NWKEK
99
(
9730
+
PgJg-+
+
pg”
> +
1 +O”K,99
1
pp
+ d2g
310 p210
1 +% ,210
+
Q?opg
where : N
= number of disintegrations
IE
= measured
1x-y
= measured radiation
PE
intensity
efficiency
total conversion K-conversion
1 ;
with energy E
of radiation
with energy
X
coincident
with
Y
= relative intensity of the e.c. exciting with energy E detector
+
1 + G9
per unit time
of radiation
intensity
of energy
+
for radiation
coefficient
transition
to an excited
state,
de-
with energy E
of radiation
with energy E
coefficient
fraction X-capture (X = K, Lr, . ..I K, LI, . . . fluorescence
in the e.c. transition yield
to a level
with
energy
probability = relative AFshell hole
fxu
that a Y-shell
hgle is caused by the filling of ;t
/xyz = rciative probability that a Z-shell hole is caused by the filling of a Y-shell hole which originates from the filling of a X-shell hole. From the parameters
given e~~uations various are given below.
parameters
can
be obtained;
these
6. The total transition energy. Using the computations of Br ys k and Rosel2) IVY derived ;t relation between the P:!, Pf, and the value of QE from the equations:
P& Lrrr z 0; usually ast-;umecl for allowed and nun-unique 7
I
once forbidden
transitions.
PIj_r+..ma. 1
-
_ = 0.266
_ Q?__.
Ex = binding energy of a X-shell
electron
__._~__
PF1:
QE= QT =
transition
QE-
energy to a level Cth
total transition
2.6
---
f2
14.31 >
energy E
energy
The relation bet\tTeen P E, PF, and QE is plotted in figure 5. From ~1. 7 we obtained the fraction K-capture to the 129 keV level : P:i_“” = 0.153 -+ 0.0 11
0.5
0.1
Ilr-Gg. 5. Fraction
K-capture,
LI-capture
as a function
of the transition
energy respectively.
THE
ELECTRON
CAPTURE
DECAY
OF
195Au
2047
this value corresponds with a total transition energy: QT = 226 h 2 keV. This leads to the supposition of a 2 10 keV gamma radiation de-exciting a level at 210 keV, which is excited by capture of atomic orbital electrons from the L- or outer shells; this assumption is supported by coincidence measurement-. It is likewise possible to determine the transition energy by way of eq. 8. Considering : ~L-21O/hl
--.-
pyq~x&xfxY@)
-
IL-.l29/h29
p;;‘F+XEXfXY@‘)
+
P~gG(WX&XfXYfKX)
>
where :
x,
Y, = LI,
br,
WX, fxu and
fKX
&II
are taken from refs 7, 13 and 15
pa10 P-
-p
I B==
LII
p210 rAI
= 0.0775
-
Q 210 -
pl29 JAII p = plZ9
Q210
0.0775
LI
Q12g -
13,735
2
Q129 -
14,355
EX: only the absorption factor in EX has to be known; factors like solid angle, fraction LX in single channel and possible loss in the fast coincidence arrangement, are the same in numerator and denominator and can be crossed out. Taking: /? m /Y w 0.0775 and Pg” = 0.153 -& 0.01 I equation
8 becomes : P;;”
x 0.452
Pz”,” x 0.452
+ 0.028
= 0’398
The transition energy follows from the &values corresponding end-points of a definite 81 keV interval on the QE-axis of fig, 5.
with the
QT = 229 & 1 keV in agreement with the former value. Once the QT value is known, all the PE values follow from the Pi curve. c. The conversion coefficients. The K-shell conversion coefficient of the 99 keV transition was obtained by eq. 9, with the help of equations 2, 3, 6 and 7; assuming a pure E2 character of the 129 keV transition, the ag” follows from the tables of Rose 14) and the equation EF + 0.0394
,gg
= 6.03
leads to ag = 6.01 & 0.15
2048
\%T. GOEIIBLOEII,
-..
.___~.
.- ----.
E. MASI’ENf?kOEK, -____~_~~__r”-_._--
A.
KEMYER
,4ND
J. BLOK
Measurements with a krypton as well as with an argon counter to evaluate 1~-~&0 of eq. 5, consequently
enabled
us
0.55 & 0.04 which leads to a total conversion $9
----_
___
refcrencc
d. Relative
_.- -__--_._
I
I
= 9.9 + 1.
7 _4 + 8*2 -m-2.8
- ---_ 999
--_
coefficient:
I
- -__. ._
i
8)
9.0
-.-.---
1 5 *8 ____1.5 / ~_ _~__ 6.86 __ _.
I!
3
6.01 -1.. 0.15 ~______ ! 9.9 _ “- 1
I
this paper
intensities.
The intensities of the KX and gamma radiations with regard to the 99 keV are given in table II; escape of I-KX rays, absorption in the cuver and the efficiencies of the detectors were taken into account.
Energy Relative
(k&J 1 30 1 A-,1- 1 ---_ -- _-__ __ __~ “__ intensity t 9.31 i 825 j
99 ’ 129 I 210 .___.,____ A._--. ._ 100 1 8.38 0.24
e. Branching ratios. Using the conversion coefficients from M c G o w an and St e 1s o n5) for the 129 and 210 keV transitions : ,129 = 1.79 ; ,210 = = 0.77 and for the 99 keV transition the values given above, we were able to derive the branching ratios. Eq. 6 leads to: v30/$99
The quotient
Analogou+
of the equations
from the equations
=
0.67 *
0.10
3 and 2 gives
4 and 3 it follows that
Moreover, knowledge of the quotient 1 hr/199 enables us to estimate the capture ratio to the ground state; this being a very rough estimate it only indicates that the capture transition probability to the ground state is smaller than six percent. The results are summarized in table ITI. f. Level scheme. A level scheme of the 195Au-195Pt decay is proposed and given in fig. 6 ; we didnot find an indication for a 110 keV gamma, as was
THE
ELECTROK
CAPTURE
TABLE reference
-. --
Dt! Shalit
DECAY
OF
III
p730
47129
1)
999
65%
35% m 50%
Bisi
8)
This
paper
67 !- 10 (39 z
‘p
4) “/
-50%
97210
1 1 w
3.6 1 0.7
0.07
m 0.05%
(2 z 0.5}%
‘;95Au 115
117
Fig. 6. Proposed
2049
195Au
decay
scheme 195Au-195Pt.
observed by McGowan and Stelson5) in the spectrum of the Coulomb excited 195Pt. They offered two possible explanations which are indicated by the dotted lines in figure 2; we tried to verify the one that gave a transition between the levels at 2 10 and 99 keV in recording the spectrum with a Xe proportional counter and looking for coincidences with the 99 keV gamma; we found no trace whatever, - but we like to stress the fact, that if 43110 5 ~3210holds, the possibilities for a conclusion are reduced considerably, Coincidences of the 129 keV with the Xenon proportional counter pulses, revealed no radiation of 81 keV, corresponding with the energy difference between the 210 and 129 keV levels. Acknowledgements. The authors wish to acknowledge the assistance rendered by the “Instituut voor Kernphysisch Onderzoek” in preparing their sources. They want to pay tribute to the late Mr. I. Blo k, who started these experiments. Received
12-6-64
2050
THE
De Shalit, Uisi,
A., Huber,
,A. and Zappa,
Potnis,
ELECTRON
CAPTURE
0. and Schncidcr, L., Xuovo
C’. Ii., Mandeville,
Cirnento
H., Helv. 12 (1954)
C. I<. arid Burlcw,
Berlisteill,
E. M. and Lewis,
McGowan,
1;. K. and S telsorl,
DECAY
H. \V., l’hys.
Phys.
Acta 25 (1952)
J. S., Phys.
Rev.
101) (1955)
1345.
(1959)
154.
Bar lo 11tarr d, I~., e.n., J. T’h>?s. radiunl 1:) (1958) 570, Robiusotl, 13. I,. and l’ink, 1C. \V., Rev. mod. 1’114’s. Z5Z (1960)
117.
Bisi,
A., Gurrnagnoli,
Rlok,
Rev.
Ilti
L., Allow Cirllento I i (1959) A. B., L’Vhite, R. T. md Pool, M. L., h’ucl. l’hys. SIi (1962) I<. T. alld Satchlcr, G. R., Nucl. T”hys, 32 (1962) 286.
Claflin, Hecht,
JZ. and Zappa,
I,., (;ot:dblocd,
Brysk,
H. arid Rose,
Wapstra,
ljT., Mastt:nbrock, M. I<., Rev.
A. H., Xygh,
mod.
E, and I31ok, Phys,
:JO (19%)
G. J. and VW> Lieshout,
279.
539.
Rev.
1’. H., I’hys.
195Au
OF
J.,
Phgica
(19%)
753.
843. 652. 58 (1962)
993.
1169.
R., Nuclear
Cie ( 1959) IAnlsterdarrl. Korth Hall. Row, M. I<., Intcrrlal conversion coefficierlts, Jopson, I<.C., Mark, H., Swift, C. 11. and Williaruwrl,
101
Spectroscopy
Tables,
Korth
Hall. l’ubl.
l’ubl. Cie 31. 4.,
( 1958)
Amsterdam.
l’hvt;. RFV. 3:{1 (1963)
1165.
Physica
W.
Mast enbroek,
30
204 L-2050
Em
A,
J.
1964
THE ELECTRON by W. GOEDBLOED,
CAPTURE
DECAY
E. MASTENBROEK, J. BLOK
Vrije Universiteit,
Amsterdam,
OF lg5Au
A. KEMPER
and
Nederland
Synopsis This paper A gamma The
deals with
radiation
transition
energy
QT =‘: 226 & 2 and Branching
ratios,
measurements
of 210 keV
on the electron
has been observed
is obtained
from
KX-gamma
capture
decay
of 1g5Au-1g5Pt.
that was not reported and
LX-gamma
previously. coincidences,
QT = 229 & 1 respectively.
relative
intensities
and conversion
coefficients
are given.
1. Introduction. It is possible to study the levels of 195Pt by means of: Coulomb excitation, the beta decay of 195Ir, the decay of the metastable 13/Z level and the electron capture decay of 195Au. Extensive Coulomb excitation measurements by several investigators3)5)6) indicate excited states at 99, 130, 210 and 240 keV and gamma radiations of 31, 99, 130, 140, 210 and 240 keV. Bernstein and Lewisd), by virtue of the excitation function of the 99 keV gamma radiation, suggest a first excited state at 31 keV, but Stelson and McGowans), discussing the excitation functions of the 99, 130, 140,210 and 240 keV gamma radiations, reject this suggestion; they propose the level scheme given in fig. 2. This scheme was extended by B arlo ut aud6) with levels at 420 and 720 keV. About the beta decay of the short living 195Ir only few data are known; Claf lin e,a. 9) reported gammas of 190 and 290 keV in coincidence and gave a half-life of 4.2 h. De Shalit and co-workersl) demonstrated a metastable &3/z state of 255 keV and Tl,z = 3.8 d; th eir conversion electron study of the electron capture decay of 19%4u and of the decay of this 195Ptm resulted in a level scheme which is given in figure 1. In a rather poor experiment with a proportional counter containing an argon-methane mixture, B isi and Zap-Paz) determined the ratio (pL/pK)129 = 0.58 & 0.14 and hence a total transition energy: QT = (272 & 17) keV; however, a few years later*) using scintillation methods, they corrected these values: (PL/pK)129 = = 5.5 -& 0.9 and QT = 235 keV. The present work is intended to examine the electron capture decay of 195Au with the help of proportional counters and scintillation spectrometers ; .
-
2041
-
2042
W.
GOEDBLOED,
Is. MASTENBROEK, -~__.-^-_-
A. KEMPER
in doing so we hope to give more accurate results tensities, capture ratios and transition energies, T = 3 8d l
ANI> Ja BLOK
about
gamma
ray in-
i13’2 /255
lteV T=180d
keV /
I
97
240
keV
5'2
3/2
130
f -10%)
1
"2
0
lg5Pt
Fig. 2. Level
diagram
of lW?t
from
C’doml-I
McGr)w;ttl
excitation
measurements
as given
by
and Stclsc,l~.
2. Ex @rimen tal procedure. The lg5Au activity was produced by irradiation of Pt with deuterons in the cyclotron of the “Instituut voor Kernphysisch Onderzoek” in Amsterdam. NaI scintillation counters of I + x 1&-in. counters containing an 1g X g-in, 18 X $-in, 14 x &-in and proportional argon-methane, a krypton-methane or a xenon-methane mixture were used
THE
for the measurements
ELECTRON
CAPTURE
DECAY
OF
195Au
of the X rays and the gamma radiations.
2043 Data about
the proportional counters were given previouslyll). For detections in the low energy range (up to 80 keV), we employed either one of the proportional counters or a 1; x $-in NaI crystal with 0.001 -in Al cover. The single count scintillation and the single count proportional counter spectra were analysed; a description of this analysis is given in section 3. ,4dditional information of the was obtained by coincidence experiments ; several combinations detectors, mentioned at the beginning of this section, were used to measure the KX-gamma, LX-gamma and gamma-gamma coincidences. All spectra were recorded with a RCL 512-channel analyser. A l& x l&-in NaI crystal in combination with a 3. Single cm.& sjbectra. set of tin absorbers (0.1, 0.5, 1 .O and 1.5 mm) was used to determine the relative intensities of the radiations involved, Figure 3 demonstrates the difference between two of these gamma ray scintillation spectra, one of them with an absorber of 0.26 cm tin, the other without any absorber. 4nalysis of the spectra revealed peaks at 35, 70, 99, 129 and 210 keV, the peak at 35 keV was a composite one of the KX-escape (about 38 keV) and the SO keV gamma radiations, the 70 keV is composed of the KX and 99escape radiations, while the 99, 129 and 210 kcV are gamma radiations, of 10"
I
I
1
I
N
t
to5
to4
50
250
150 -
CHANNEL
Fig. 3. Single
count
NUMBER
scintillation
a)
no absorber
b)
0.24 cm tin absorber.
spectra.
whicll the 210 keV was not reported before. In verifying the assumption of a 210 keV gamma radiation appearing in the electron capture decay of %4u, we u.sed absorbers of various thickness and different source to crystal
2044
W,
GOEDBLOED,
E. MASTENBROEK,
A. KEMPER
AXD
J. BLOK
-_- ---_
_
distances to reduce summation effects and to determine the relative intensity with regard to the 99 keV photopeak; we followed the counting rates of the 99, 129, and the 210 photopeaks for over a year to compare their half-lives. All these experiments supported our assumption, The proportional counters were very useful for the examination of the low-energetic 30 keV, LX and KX radiations. The krypton filled counter had a copper wall which gave rise to peculiar difficulties; thanks to the copper KX-radiation (about 8 keV) - stimulated by absorption of photons in this wall - part of the 30 keV gamma ray yield is found in the summation peak at 38 keV, so in this case it is necessary to read for the 30 keV gamma intensity appearing in the formulas 1 and 5 of section 4 the sum of the yields at 30 and 38 keV (see fig. 4). The argon and xenon counters had an aluminium wall, so the complications iust mentioned did not occur with these.
KnX
102
- QSC. I
50
150
A
Fig. 4. Spectrum
I
I
I
I
CHANNEL
250
NUMBER
of the krypton-methane counter showing the 38 keV summation peak,
;;t.o. the
30 ke\’ peak
and
Using the decay scheme as given 4. Experimenfal results. a. Formulae. in figure 6 one can derive the following relations: 1.
130
=
2.
199
=
NQ130E30 f + q&730
a30 + 1 +
3.
1129
=
NP7129E129 1 + ,129
; 999) a99
;
&99 ;
THE
4.
ELECTRON
9.
DECAY
OF
2045
195Au
~qm~21o -Pm
I 210 =
T +
,210
’ 99 fiK
IK-30 5 . ----.J30
6.
CAPTURE
k-99 -‘I99
=
__IK-K
2mK&K z _____
~30p~g+~99pg
coK&K
4730 +
IK-99
-
a99
1-t
&K&K
.
mE9(1
(1 + ,I29
899
;
> ’
q99
tip +
--
+
1.
plS9 cp129 K
agg)
)(y3dy9
+
%
J
Q799PF)
ag
129
10,
IK = NWKEK
99
(
9730
+
PgJg-+
+
pg”
> +
1 +O”K,99
1
pp
+ d2g
310 p210
1 +% ,210
+
Q?opg
where : N
= number of disintegrations
IE
= measured
1x-y
= measured radiation
PE
intensity
efficiency
total conversion K-conversion
1 ;
with energy E
of radiation
with energy
X
coincident
with
Y
= relative intensity of the e.c. exciting with energy E detector
+
1 + G9
per unit time
of radiation
intensity
of energy
+
for radiation
coefficient
transition
to an excited
state,
de-
with energy E
of radiation
with energy E
coefficient
fraction X-capture (X = K, Lr, . ..I K, LI, . . . fluorescence
in the e.c. transition yield
to a level
with
energy
probability = relative AFshell hole
fxu
that a Y-shell
hgle is caused by the filling of ;t
/xyz = rciative probability that a Z-shell hole is caused by the filling of a Y-shell hole which originates from the filling of a X-shell hole. From the parameters
given e~~uations various are given below.
parameters
can
be obtained;
these
6. The total transition energy. Using the computations of Br ys k and Rosel2) IVY derived ;t relation between the P:!, Pf, and the value of QE from the equations:
P& Lrrr z 0; usually ast-;umecl for allowed and nun-unique 7
I
once forbidden
transitions.
PIj_r+..ma. 1
-
_ = 0.266
_ Q?__.
Ex = binding energy of a X-shell
electron
__._~__
PF1:
QE= QT =
transition
QE-
energy to a level Cth
total transition
2.6
---
f2
14.31 >
energy E
energy
The relation bet\tTeen P E, PF, and QE is plotted in figure 5. From ~1. 7 we obtained the fraction K-capture to the 129 keV level : P:i_“” = 0.153 -+ 0.0 11
0.5
0.1
Ilr-Gg. 5. Fraction
K-capture,
LI-capture
as a function
of the transition
energy respectively.
THE
ELECTRON
CAPTURE
DECAY
OF
195Au
2047
this value corresponds with a total transition energy: QT = 226 h 2 keV. This leads to the supposition of a 2 10 keV gamma radiation de-exciting a level at 210 keV, which is excited by capture of atomic orbital electrons from the L- or outer shells; this assumption is supported by coincidence measurement-. It is likewise possible to determine the transition energy by way of eq. 8. Considering : ~L-21O/hl
--.-
pyq~x&xfxY@)
-
IL-.l29/h29
p;;‘F+XEXfXY@‘)
+
P~gG(WX&XfXYfKX)
>
where :
x,
Y, = LI,
br,
WX, fxu and
fKX
&II
are taken from refs 7, 13 and 15
pa10 P-
-p
I B==
LII
p210 rAI
= 0.0775
-
Q 210 -
pl29 JAII p = plZ9
Q210
0.0775
LI
Q12g -
13,735
2
Q129 -
14,355
EX: only the absorption factor in EX has to be known; factors like solid angle, fraction LX in single channel and possible loss in the fast coincidence arrangement, are the same in numerator and denominator and can be crossed out. Taking: /? m /Y w 0.0775 and Pg” = 0.153 -& 0.01 I equation
8 becomes : P;;”
x 0.452
Pz”,” x 0.452
+ 0.028
= 0’398
The transition energy follows from the &values corresponding end-points of a definite 81 keV interval on the QE-axis of fig, 5.
with the
QT = 229 & 1 keV in agreement with the former value. Once the QT value is known, all the PE values follow from the Pi curve. c. The conversion coefficients. The K-shell conversion coefficient of the 99 keV transition was obtained by eq. 9, with the help of equations 2, 3, 6 and 7; assuming a pure E2 character of the 129 keV transition, the ag” follows from the tables of Rose 14) and the equation EF + 0.0394
,gg
= 6.03
leads to ag = 6.01 & 0.15
2048
\%T. GOEIIBLOEII,
-..
.___~.
.- ----.
E. MASI’ENf?kOEK, -____~_~~__r”-_._--
A.
KEMYER
,4ND
J. BLOK
Measurements with a krypton as well as with an argon counter to evaluate 1~-~&0 of eq. 5, consequently
enabled
us
0.55 & 0.04 which leads to a total conversion $9
----_
___
refcrencc
d. Relative
_.- -__--_._
I
I
= 9.9 + 1.
7 _4 + 8*2 -m-2.8
- ---_ 999
--_
coefficient:
I
- -__. ._
i
8)
9.0
-.-.---
1 5 *8 ____1.5 / ~_ _~__ 6.86 __ _.
I!
3
6.01 -1.. 0.15 ~______ ! 9.9 _ “- 1
I
this paper
intensities.
The intensities of the KX and gamma radiations with regard to the 99 keV are given in table II; escape of I-KX rays, absorption in the cuver and the efficiencies of the detectors were taken into account.
Energy Relative
(k&J 1 30 1 A-,1- 1 ---_ -- _-__ __ __~ “__ intensity t 9.31 i 825 j
99 ’ 129 I 210 .___.,____ A._--. ._ 100 1 8.38 0.24
e. Branching ratios. Using the conversion coefficients from M c G o w an and St e 1s o n5) for the 129 and 210 keV transitions : ,129 = 1.79 ; ,210 = = 0.77 and for the 99 keV transition the values given above, we were able to derive the branching ratios. Eq. 6 leads to: v30/$99
The quotient
Analogou+
of the equations
from the equations
=
0.67 *
0.10
3 and 2 gives
4 and 3 it follows that
Moreover, knowledge of the quotient 1 hr/199 enables us to estimate the capture ratio to the ground state; this being a very rough estimate it only indicates that the capture transition probability to the ground state is smaller than six percent. The results are summarized in table ITI. f. Level scheme. A level scheme of the 195Au-195Pt decay is proposed and given in fig. 6 ; we didnot find an indication for a 110 keV gamma, as was
THE
ELECTROK
CAPTURE
TABLE reference
-. --
Dt! Shalit
DECAY
OF
III
p730
47129
1)
999
65%
35% m 50%
Bisi
8)
This
paper
67 !- 10 (39 z
‘p
4) “/
-50%
97210
1 1 w
3.6 1 0.7
0.07
m 0.05%
(2 z 0.5}%
‘;95Au 115
117
Fig. 6. Proposed
2049
195Au
decay
scheme 195Au-195Pt.
observed by McGowan and Stelson5) in the spectrum of the Coulomb excited 195Pt. They offered two possible explanations which are indicated by the dotted lines in figure 2; we tried to verify the one that gave a transition between the levels at 2 10 and 99 keV in recording the spectrum with a Xe proportional counter and looking for coincidences with the 99 keV gamma; we found no trace whatever, - but we like to stress the fact, that if 43110 5 ~3210holds, the possibilities for a conclusion are reduced considerably, Coincidences of the 129 keV with the Xenon proportional counter pulses, revealed no radiation of 81 keV, corresponding with the energy difference between the 210 and 129 keV levels. Acknowledgements. The authors wish to acknowledge the assistance rendered by the “Instituut voor Kernphysisch Onderzoek” in preparing their sources. They want to pay tribute to the late Mr. I. Blo k, who started these experiments. Received
12-6-64
2050
THE
De Shalit, Uisi,
A., Huber,
,A. and Zappa,
Potnis,
ELECTRON
CAPTURE
0. and Schncidcr, L., Xuovo
C’. Ii., Mandeville,
Cirnento
H., Helv. 12 (1954)
C. I<. arid Burlcw,
Berlisteill,
E. M. and Lewis,
McGowan,
1;. K. and S telsorl,
DECAY
H. \V., l’hys.
Phys.
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J. S., Phys.
Rev.
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1345.
(1959)
154.
Bar lo 11tarr d, I~., e.n., J. T’h>?s. radiunl 1:) (1958) 570, Robiusotl, 13. I,. and l’ink, 1C. \V., Rev. mod. 1’114’s. Z5Z (1960)
117.
Bisi,
A., Gurrnagnoli,
Rlok,
Rev.
Ilti
L., Allow Cirllento I i (1959) A. B., L’Vhite, R. T. md Pool, M. L., h’ucl. l’hys. SIi (1962) I<. T. alld Satchlcr, G. R., Nucl. T”hys, 32 (1962) 286.
Claflin, Hecht,
JZ. and Zappa,
I,., (;ot:dblocd,
Brysk,
H. arid Rose,
Wapstra,
ljT., Mastt:nbrock, M. I<., Rev.
A. H., Xygh,
mod.
E, and I31ok, Phys,
:JO (19%)
G. J. and VW> Lieshout,
279.
539.
Rev.
1’. H., I’hys.
195Au
OF
J.,
Phgica
(19%)
753.
843. 652. 58 (1962)
993.
1169.
R., Nuclear
Cie ( 1959) IAnlsterdarrl. Korth Hall. Row, M. I<., Intcrrlal conversion coefficierlts, Jopson, I<.C., Mark, H., Swift, C. 11. and Williaruwrl,
101
Spectroscopy
Tables,
Korth
Hall. l’ubl.
l’ubl. Cie 31. 4.,
( 1958)
Amsterdam.
l’hvt;. RFV. 3:{1 (1963)
1165.