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Three-particle excitations in Lu177 at 1230 and 1240 keV
Volume 8, number I
PHYSICS
LETTERS
THREE-PARTICLE EXCITATIONS AT 1230 AND 1240 key
1 January 1964
IN L u 177
H. S. JOHANSEN, M, J ~ R G E N S E N , O. B. NIELSEN and G. SIDENIUS
Institute for Theoretical Physics, University of Cope~,~ge~, Denmark Received 5 December 1963
In the decay of 1.9 h ~s177, a level in Lu177 at ~1240 key has been observed in addition to s o m e iow lying states I, 2). The population of this state has apparently not been determined very accurately, trdt the Ic~gft for the fl-transition from Yb!77 s e e m s to be low, ~, 4.4 2), suggesting allowed unhindered ~mtare. Mottelson and Nlisson 3) have p o i n t ~ out that the ~round state of yb177, interpreted as the 9/2 + (6 2 4) neutron state, cannot take part in such a transition, as no protein state with these asymptotic quantum r~amber6 is available in this region of the isotopes. This ;~-dec~y can thus ~ot be considered a simple transformation of the odd neutron iu yb177 into a sir~le-×proton state in Lu I~7, The only relevant neutron-proton pair witi~ identical asymptotic quantum numbers is v 7/2- (5 1 4), 9/2" (5 1 4). A n allowed unhindered ~-transltion can only proceed by the breaking of a neutron pair in Yb 177 and the formation of a configuration of the ~bove two states together -with the 9/2 + (6 2 4) neutron. Accordiagly, the 1240 keV state is a threeparticle state. A s the two (5 1 4) particles can couple either to spin I+ or 8 +, the three-particle states in this corJiguratlon can have spin 7/2+ (two possibilities), 11/2+ or 2,q/2+. R was the aim of the present investigation to obi =in a more accuj'ate log f/ value for the ~-transition to the 1240 keV level, and to establish experimentally the ~pin and the parry of this level. Activities of Y b 177 were produced in the Danish reactor D R 3 by irradiating Yb2!76 03 enriched to 97.5% Yb176 in a fltu~of ~=~8× i0 I~ neutrons/era ~scc. Thin ;~-ray sources were prepared by electroplatmg on ~200 ~g/crn 2 nickel foil. A strong source fer the measurement of the high energy conversion lines consib'ted of a p~ece o| ~ 0.5 mg/cr~2 foil of yb176 m e tal, which could be used as ~-~'ay source immediately after irradiation Ln the reactor. Neither of these srr~rce~ was satisfactory for the low-energy measurements m the f~ray v.pectrometcr, ~he spectIic acUvlt~ being insufficient, ~ d also the conteat ot -~)IT5 caused trouble. For this reason~ a ~-r~,y s~mrce with a strength of I00 ,~C~tr. was pre~ared in the Copenhagen isotope separator for the ~tudy oi the low energy et~nversion lines.
Continuous E-ray spectra, conversion lines a~.d e~f coincidence spectra were studied in a singa~. ~-ray spectrometer. The r-ray spectra ~:ere recorded by means of a 7.5 c m dia.× 7.5 c m Nal crystal and a multichaunel analyzer. Fig. 1 shows the r-ray spectrum of an isotope~ separated, source, with which a small amount of the daughter 6.8 d Lu177 has grown in, In addition to the previously known "r-rays 1 ~2), a line ~ 785 keV is apparent. Fig. 2 shows the low-energT conversion line spectrum. The 147.4 and the 162.6 keV transitions have not been reported earlier in the Y b 177 decay, but the 147.4 keV transition is known from the decay of the 155 d LuIV7 isomer 6) to connect the 11/2 + and 9/2+ states in the ground-state rotational band. The 162.6 keV transition was found to be coincident with P~~.780 keV 7 - r a y (fig. 3), apparently the line observed also in the single y - r a y spectrum, and is according!y placed between the level at 452 keV (see fig. 4) This is interpreted as the 13/2" level in the I{=9/2" band. We observed K-conversion lines of the two high energy transitions of 1239~ 2 keV and 1079~:5 keV, which were suggested from earlier r - r coincidence studies to populate the ground state and the l S l keV state. The line K 1239 could be measured on a low background hi coincidence with K X-rays. The ~-continuum below the K 1079 line was strongly coincident with low energy r - r a y s , and the line could not be seen in the coincidence measurements, but only in a scan of the single ~ - r a y spectrum. F o r this reason our energy measurements w~ re scarcely better than 5 keV, and the result is consistent with the assumption that the two tran~Jitions originate in the same high energy level. D,~ing the investigations we were, however, kind.y .:nformed of the accurate energy measure~r.ents of the Chalk River group 5), clearly LudLmting the presence of two different levels at :230.7 and 1240.6 keV. The experimental results for '~e electromagnetic transitions a r e summarizc
Volume 8. number }
PIIYSICS
LETTERS
1 January I
x IO~
.J
t
II
~.
M
~ It
I I
CHAf~NEL NUMBER
Fig.
z
].
CHANNEL NUMBER
Low attd high energy, f - r a y s p e c t r a of isotope-y[ s e p a r a t e d Yb 177, m e a s u r e d with a 7.5 c ~ dta ° ; ,5 cm N a i - c r y s i a l .
~
.~ ,tB - ( 10)
:t ,ol
=.
:
t
%=
Fig. ~, Low e ~ r g y c o n v e r s i o n lir~ e 2 e ~ u r n of e eource yb177 pr~par~-X i~, tl e isotope, sep,t~ator. Tim ~r~c/r~,tm ~ not t o r t e . t i e d f(~r decay.
62
?
V o l u m e 8~ n~r~t~r I
I~HYSICS
LETTERS
li'l
"
* -
1 January 1964
"~ .................
' I!! i
r.'""
-
i
_
~2~o
{%)+
t
I
I
i.t
:.:
,..
,.. ,¢ ".\...
,
Fig. 3 , ¢-ra) ~lmctr~,:m tn c ~ u v ' A e ~ w:th ~ line K !£2 (fig. 2~. TP~ , t r o n g ttne of_ 208 I**"' Ls due ~ !~e t a l l (~f th~ Iil~+ ( t1:1. T ' : e n-<.:cs ~ e n - , e - " ' ' ~:lozu~e,~ w:th o~~la~ivel~ ¢Ac +.,:rs~- h ~rger eoat~n~ of L u * ' - t h a n :ndlea+~-d ':n ,~g ,he ~ t i s ~ c a l fluctuz~:o~ a r e ]ar~, ~I'~ L~ t h , ~aL=: -, ='or.-
t e n s i t ! e c t o t h e int~l n a ! c o n v e r s ~ o D ~me~, . c ~ ~ . r f o r m e d thx~mgh ~'~,:, cor, ve.r~:o~t e'..~Ui"AC~t o~ th:~ i 5 1 k e V tr;zt.~'l~¢:o T~us c c u l d be r a e a s u r ( . ~ f r ~ : ~ t h e r a t i o of K X - r a y s m 1 5 i k e V > - r ~ y y tn ~, ~ ~e,4trozn of y - r a y s de~-v,~? ~. f--;: tc,,th~ o f -. ~ r , . r ~ l a t i v e to 3 - p a r t i c ! e _ ~ , ,: m e e o n t m t m m , T h i s epc,. t r u m c o u l d be m e a s u r e d m ~ d e r fav_~v~rab!~ !>~2t;i~,uu,~d c o a d i t ~ o n s , a s t h ~ : ~ k e V s t a t e (f g % ~ t h e o n t y
t r m m , c o r r e s p o n d i n g t o t h e g r o u n d - s t l t ~ t:rr~nsl,.~,u, wa= %urM tO M 1 4 0 9 ± 20 k e Y . T h e i~W e n e r g y ~ : o t , ~ ...... a n ~ 1241 ~.,~~ ~=~~,~ w~ ~ e m e a s u r e d i n c o o,, i~eidc: : : v+~h ~!gh eae~ g y y - r a y s , The ",re.re n o t :'e.~otve~ .~nto ¢.. ,portents; t h e m e a n m a ~ . ~ u r v ~:r~err ~ s u i f _ 7,~r t h e t o t a l d e c : 7 t _ ~ 7 :$ p r e v i o u s n~: ~ s t ~ r e m e n t $ . Imtensit2e~ oi the fs-grouv,~ ~ r ~ v e ~ in f a b l e 2, upou *h-~ / - r a y i n t e r . ~ : ,-~ : 7 3 m ~ b i e
w e l l ~i7 v.<':'., ~a,_, - ,, :: ,a,'.,2c
m~iniy based 1. T h l ~ p r ~ z e -
i
Lu"+ ~ ,accay scbem~ YLI~ 7 Lu 177, The m~.~, ie.~Lare~ were revealed ~n -,, . ~ ~','~, .:jations i~ ~)
/ I 2 '*' ~nd i s td,:n~ffied a~ tim (4 0 4) "7f? + 1~"='%.~ ~ t a t e . ".~h~e~ ~ "~,~ o n i v ~ , , ~ r l y i n g ~qilsson s t a t e wi¢/~ t h i s s p ~ . :~..V.,~we-~ u;'-', <.Mered ~ - t r a n s i ~ o a i,:,vels, mud f ~ , Ig2 ~ t u r e o f ~ h e 124t kcV ~ . :~ i n ,£~=.~te tha~ ~ t h e s e l e v e l s h-~.~e t h e ~am, : ~:. ~i:~ a s L~ ~77 ~ o u n ~ s t a t e . T M s c o n f i r m s t h e (6 2 4) ~, - ~ M g ~ m e r t o£ f ~ N = 1 0 7 g r o u n d ~ t a t e of ~!77 ~ s al~ n e ~ , ~ u r i n g n,~u~roa statez b.qve n e ~ g u t i v e par~;7. T,~*~ 1 2 3 0 v a ~ d 1 2 4 0 k e V s t r t e s :~,< L u 177 r a n t h e n o ~ / ~ - ~ 7 / 2 +, 9 / 2 + o r 1 1 / 7 % O n e of t h e m -uw-~ b c 1~/2+~ "-'~c~ i~ .'te~x~ites to a l e v e l w i t h ~ p ~ ~ 3 / $ - ~ ~'be ~-~~ i'0 k e V y - r a y i s n o t m e a ~ v r e d ~e-~°-~t~ .'., ~ u e ~ h t o d i s t ~ . n ~ s h be1~v~en the t m <)~,s:.: h i i J ~ e s . W e h a v e ~ g e s t . . ~ l t h e 1221 k e V ,'_evel ~c ~e t h e 1 i / 2 + s l a t e . ?,race i t decay.= s t r o n g l y ~o !he g/2- m e m b e r ,if. ~;ne s a m e rotrd~.~or',, h~vdo It i s l ~ m t ~ ~ g t o i m e r p r e t e t h e 1240ke~i ~' v~i ~.~ tin? of ~. : 12+ sta~e~ ef t h e sa~a~ t h r e e - p a r t i c l e c o n f i g u r -
r ~ y s , a s sh-'-, '~_~, 4 , m a y c o m ~ t n e o a L r t L ~ ,-'ns ,,~'~,r, boLh hfgtl (,m: rVL" b-' ~ . T h e a l l o w e d u n b L ~ d e t e d n M u ~ - * ~ ~ h e O - t r a r i s i i L ~ r m , ,: .~ 0"-4~ ~ f¢~:~dV e s t a b l t a h v . : : ,~ hotb ot t2,~ k m e n e r g y i~-:~'o'*.' ~ T h ? _~a : r ~ i c u ~.~as s t ~ n u h ~ t e d b y P r o f e s s o r s The gro~ 2~te of Lu 177 bus ~ ~.lea~ed sp~.n .:-. ~. B~. ~..~¢m a n d B. C. ~¢ilsson. W e a r e i n d e b t e d
63
PHYSICS
VolulIIc 8, Rumber I
t January
LETTER~
1964
Table I
I2-~.6 139.a 147.4 150.8 162~g 785 940 1079
80e#, MI a) + ."0% ,'~
5.25 1.50
~5%ydc'~25%V2 Mainly M~
}
[
' ~6
} ,., ~ J
! I
~ 0~'~ ] t5.5 i ' 0.08
0.80
E1
0,~5 ~ 5
I
0.4,
El d)
7.0 %06
, ~ ~
k(.OOO9
;I20
0.0012 }~ I}
I~
n_j_Li.Ol I 0
_ _ _ _
E:
{
0.0021
0.~020 I
, 6.~
} I
4.7 {
! ~0
~
""
a,a
5
[
1o.o 0.4 2u.0 0. t6 5
~
1 ,
.~ ~O.a
} 4.7
I
4.7
t
AL intensities are given in % of all decays. Toe transition in~ait~.es in the t ~ t cotun-m ar~ mainly Imsed on Iy vale., which ar~ obtained ~Jydividing the conv~rs~m Iir~ inter~Ities by the adopt ~d c~K's. a) E2/M: ; .~to based on K/L =4.5+ 0.6 and LI ~ Ill/1£II -~4.6± 0.6. givL'%g~2 = E2/MI = 0 25~0.3
b) Based onR L =5±1, giving only rougbl:~ '2-eE2 co~tent. c) ~{esultfrom '55 d Lu 177 dec iy 7), d~ the 150.8 keV ~a'ansition is a s~ow El transition with abnormal co~version ooeff|clent~ 5).
T:~ble 2 ir~ensitms of ~-grou~ Energy. of daughter 1~., el 0 12t .6 1"0.8 289 123i 1241
Transition
Inmns :ty
energy
~7o~
lcgft f
1400 1280 1250 ~110 i 7O I60
00 9 t7 2 6 5
7.2 0.8 7.5 4,4 ~.4
6.6 "!
the uncertaintK-~ of the log q vahm~ arc about 0.2
84
I I I
to M r . Sven B j ~ r n h o i m f o r p u t t i n g t h e Yb 177 me" f o i l a t o u r d i s p o s a l D r . G . T . Ewmn h a s k i n d l y c o m m u n i c a t e d to u s Me Chalk R i v e r r e s u l t s p r i o r to p u b l i c a t i o n . 1} J . M Cork et sic, Phys Rev. I01 (1956) 1942. 2) J, P. Mize, M. E. Bunker and J . W . S t a r n e r , Phys. Rev. 103 (1956) 132. a) B.R Motteb o~ and S.C,.Nils~n, prorate comm~mieatier.. 4) B.R MottoI~or .m~t S.G,Nilsson, Mat Fys, Skit. Dan. Vid. Sclsk. I (19591 ,la. ~. 5} G, T. Ewaa. private comm,laicativn, 6) F . R . P e l e r s e n and H A.Shugart, Phys. Rcv. i26 (1962) 252. 7) L.¥e-istensen et a L . Physics Letters 8 (1963~ 57.
PHYSICS
LETTERS
THREE-PARTICLE EXCITATIONS AT 1230 AND 1240 key
1 January 1964
IN L u 177
H. S. JOHANSEN, M, J ~ R G E N S E N , O. B. NIELSEN and G. SIDENIUS
Institute for Theoretical Physics, University of Cope~,~ge~, Denmark Received 5 December 1963
In the decay of 1.9 h ~s177, a level in Lu177 at ~1240 key has been observed in addition to s o m e iow lying states I, 2). The population of this state has apparently not been determined very accurately, trdt the Ic~gft for the fl-transition from Yb!77 s e e m s to be low, ~, 4.4 2), suggesting allowed unhindered ~mtare. Mottelson and Nlisson 3) have p o i n t ~ out that the ~round state of yb177, interpreted as the 9/2 + (6 2 4) neutron state, cannot take part in such a transition, as no protein state with these asymptotic quantum r~amber6 is available in this region of the isotopes. This ;~-dec~y can thus ~ot be considered a simple transformation of the odd neutron iu yb177 into a sir~le-×proton state in Lu I~7, The only relevant neutron-proton pair witi~ identical asymptotic quantum numbers is v 7/2- (5 1 4), 9/2" (5 1 4). A n allowed unhindered ~-transltion can only proceed by the breaking of a neutron pair in Yb 177 and the formation of a configuration of the ~bove two states together -with the 9/2 + (6 2 4) neutron. Accordiagly, the 1240 keV state is a threeparticle state. A s the two (5 1 4) particles can couple either to spin I+ or 8 +, the three-particle states in this corJiguratlon can have spin 7/2+ (two possibilities), 11/2+ or 2,q/2+. R was the aim of the present investigation to obi =in a more accuj'ate log f/ value for the ~-transition to the 1240 keV level, and to establish experimentally the ~pin and the parry of this level. Activities of Y b 177 were produced in the Danish reactor D R 3 by irradiating Yb2!76 03 enriched to 97.5% Yb176 in a fltu~of ~=~8× i0 I~ neutrons/era ~scc. Thin ;~-ray sources were prepared by electroplatmg on ~200 ~g/crn 2 nickel foil. A strong source fer the measurement of the high energy conversion lines consib'ted of a p~ece o| ~ 0.5 mg/cr~2 foil of yb176 m e tal, which could be used as ~-~'ay source immediately after irradiation Ln the reactor. Neither of these srr~rce~ was satisfactory for the low-energy measurements m the f~ray v.pectrometcr, ~he spectIic acUvlt~ being insufficient, ~ d also the conteat ot -~)IT5 caused trouble. For this reason~ a ~-r~,y s~mrce with a strength of I00 ,~C~tr. was pre~ared in the Copenhagen isotope separator for the ~tudy oi the low energy et~nversion lines.
Continuous E-ray spectra, conversion lines a~.d e~f coincidence spectra were studied in a singa~. ~-ray spectrometer. The r-ray spectra ~:ere recorded by means of a 7.5 c m dia.× 7.5 c m Nal crystal and a multichaunel analyzer. Fig. 1 shows the r-ray spectrum of an isotope~ separated, source, with which a small amount of the daughter 6.8 d Lu177 has grown in, In addition to the previously known "r-rays 1 ~2), a line ~ 785 keV is apparent. Fig. 2 shows the low-energT conversion line spectrum. The 147.4 and the 162.6 keV transitions have not been reported earlier in the Y b 177 decay, but the 147.4 keV transition is known from the decay of the 155 d LuIV7 isomer 6) to connect the 11/2 + and 9/2+ states in the ground-state rotational band. The 162.6 keV transition was found to be coincident with P~~.780 keV 7 - r a y (fig. 3), apparently the line observed also in the single y - r a y spectrum, and is according!y placed between the level at 452 keV (see fig. 4) This is interpreted as the 13/2" level in the I{=9/2" band. We observed K-conversion lines of the two high energy transitions of 1239~ 2 keV and 1079~:5 keV, which were suggested from earlier r - r coincidence studies to populate the ground state and the l S l keV state. The line K 1239 could be measured on a low background hi coincidence with K X-rays. The ~-continuum below the K 1079 line was strongly coincident with low energy r - r a y s , and the line could not be seen in the coincidence measurements, but only in a scan of the single ~ - r a y spectrum. F o r this reason our energy measurements w~ re scarcely better than 5 keV, and the result is consistent with the assumption that the two tran~Jitions originate in the same high energy level. D,~ing the investigations we were, however, kind.y .:nformed of the accurate energy measure~r.ents of the Chalk River group 5), clearly LudLmting the presence of two different levels at :230.7 and 1240.6 keV. The experimental results for '~e electromagnetic transitions a r e summarizc
Volume 8. number }
PIIYSICS
LETTERS
1 January I
x IO~
.J
t
II
~.
M
~ It
I I
CHAf~NEL NUMBER
Fig.
z
].
CHANNEL NUMBER
Low attd high energy, f - r a y s p e c t r a of isotope-y[ s e p a r a t e d Yb 177, m e a s u r e d with a 7.5 c ~ dta ° ; ,5 cm N a i - c r y s i a l .
~
.~ ,tB - ( 10)
:t ,ol
=.
:
t
%=
Fig. ~, Low e ~ r g y c o n v e r s i o n lir~ e 2 e ~ u r n of e eource yb177 pr~par~-X i~, tl e isotope, sep,t~ator. Tim ~r~c/r~,tm ~ not t o r t e . t i e d f(~r decay.
62
?
V o l u m e 8~ n~r~t~r I
I~HYSICS
LETTERS
li'l
"
* -
1 January 1964
"~ .................
' I!! i
r.'""
-
i
_
~2~o
{%)+
t
I
I
i.t
:.:
,..
,.. ,¢ ".\...
,
Fig. 3 , ¢-ra) ~lmctr~,:m tn c ~ u v ' A e ~ w:th ~ line K !£2 (fig. 2~. TP~ , t r o n g ttne of_ 208 I**"' Ls due ~ !~e t a l l (~f th~ Iil~+ ( t1:1. T ' : e n-<.:cs ~ e n - , e - " ' ' ~:lozu~e,~ w:th o~~la~ivel~ ¢Ac +.,:rs~- h ~rger eoat~n~ of L u * ' - t h a n :ndlea+~-d ':n ,~g ,he ~ t i s ~ c a l fluctuz~:o~ a r e ]ar~, ~I'~ L~ t h , ~aL=: -, ='or.-
t e n s i t ! e c t o t h e int~l n a ! c o n v e r s ~ o D ~me~, . c ~ ~ . r f o r m e d thx~mgh ~'~,:, cor, ve.r~:o~t e'..~Ui"AC~t o~ th:~ i 5 1 k e V tr;zt.~'l~¢:o T~us c c u l d be r a e a s u r ( . ~ f r ~ : ~ t h e r a t i o of K X - r a y s m 1 5 i k e V > - r ~ y y tn ~, ~ ~e,4trozn of y - r a y s de~-v,~? ~. f--;: tc,,th~ o f -. ~ r , . r ~ l a t i v e to 3 - p a r t i c ! e _ ~ , ,: m e e o n t m t m m , T h i s epc,. t r u m c o u l d be m e a s u r e d m ~ d e r fav_~v~rab!~ !>~2t;i~,uu,~d c o a d i t ~ o n s , a s t h ~ : ~ k e V s t a t e (f g % ~ t h e o n t y
t r m m , c o r r e s p o n d i n g t o t h e g r o u n d - s t l t ~ t:rr~nsl,.~,u, wa= %urM tO M 1 4 0 9 ± 20 k e Y . T h e i~W e n e r g y ~ : o t , ~ ...... a n ~ 1241 ~.,~~ ~=~~,~ w~ ~ e m e a s u r e d i n c o o,, i~eidc: : : v+~h ~!gh eae~ g y y - r a y s , The ",re.re n o t :'e.~otve~ .~nto ¢.. ,portents; t h e m e a n m a ~ . ~ u r v ~:r~err ~ s u i f _ 7,~r t h e t o t a l d e c : 7 t _ ~ 7 :$ p r e v i o u s n~: ~ s t ~ r e m e n t $ . Imtensit2e~ oi the fs-grouv,~ ~ r ~ v e ~ in f a b l e 2, upou *h-~ / - r a y i n t e r . ~ : ,-~ : 7 3 m ~ b i e
w e l l ~i7 v.<':'., ~a,_, - ,, :: ,a,'.,2c
m~iniy based 1. T h l ~ p r ~ z e -
i
Lu"+ ~ ,accay scbem~ YLI~ 7 Lu 177, The m~.~, ie.~Lare~ were revealed ~n -,, . ~ ~','~, .:jations i~ ~)
/ I 2 '*' ~nd i s td,:n~ffied a~ tim (4 0 4) "7f? + 1~"='%.~ ~ t a t e . ".~h~e~ ~ "~,~ o n i v ~ , , ~ r l y i n g ~qilsson s t a t e wi¢/~ t h i s s p ~ . :~..V.,~we-~ u;'-', <.Mered ~ - t r a n s i ~ o a i,:,vels, mud f ~ , Ig2 ~ t u r e o f ~ h e 124t kcV ~ . :~ i n ,£~=.~te tha~ ~ t h e s e l e v e l s h-~.~e t h e ~am, : ~:. ~i:~ a s L~ ~77 ~ o u n ~ s t a t e . T M s c o n f i r m s t h e (6 2 4) ~, - ~ M g ~ m e r t o£ f ~ N = 1 0 7 g r o u n d ~ t a t e of ~!77 ~ s al~ n e ~ , ~ u r i n g n,~u~roa statez b.qve n e ~ g u t i v e par~;7. T,~*~ 1 2 3 0 v a ~ d 1 2 4 0 k e V s t r t e s :~,< L u 177 r a n t h e n o ~ / ~ - ~ 7 / 2 +, 9 / 2 + o r 1 1 / 7 % O n e of t h e m -uw-~ b c 1~/2+~ "-'~c~ i~ .'te~x~ites to a l e v e l w i t h ~ p ~ ~ 3 / $ - ~ ~'be ~-~~ i'0 k e V y - r a y i s n o t m e a ~ v r e d ~e-~°-~t~ .'., ~ u e ~ h t o d i s t ~ . n ~ s h be1~v~en the t m <)~,s:.: h i i J ~ e s . W e h a v e ~ g e s t . . ~ l t h e 1221 k e V ,'_evel ~c ~e t h e 1 i / 2 + s l a t e . ?,race i t decay.= s t r o n g l y ~o !he g/2- m e m b e r ,if. ~;ne s a m e rotrd~.~or',, h~vdo It i s l ~ m t ~ ~ g t o i m e r p r e t e t h e 1240ke~i ~' v~i ~.~ tin? of ~. : 12+ sta~e~ ef t h e sa~a~ t h r e e - p a r t i c l e c o n f i g u r -
r ~ y s , a s sh-'-, '~_~, 4 , m a y c o m ~ t n e o a L r t L ~ ,-'ns ,,~'~,r, boLh hfgtl (,m: rVL" b-' ~ . T h e a l l o w e d u n b L ~ d e t e d n M u ~ - * ~ ~ h e O - t r a r i s i i L ~ r m , ,: .~ 0"-4~ ~ f¢~:~dV e s t a b l t a h v . : : ,~ hotb ot t2,~ k m e n e r g y i~-:~'o'*.' ~ T h ? _~a : r ~ i c u ~.~as s t ~ n u h ~ t e d b y P r o f e s s o r s The gro~ 2~te of Lu 177 bus ~ ~.lea~ed sp~.n .:-. ~. B~. ~..~¢m a n d B. C. ~¢ilsson. W e a r e i n d e b t e d
63
PHYSICS
VolulIIc 8, Rumber I
t January
LETTER~
1964
Table I
I2-~.6 139.a 147.4 150.8 162~g 785 940 1079
80e#, MI a) + ."0% ,'~
5.25 1.50
~5%ydc'~25%V2 Mainly M~
}
[
' ~6
} ,., ~ J
! I
~ 0~'~ ] t5.5 i ' 0.08
0.80
E1
0,~5 ~ 5
I
0.4,
El d)
7.0 %06
, ~ ~
k(.OOO9
;I20
0.0012 }~ I}
I~
n_j_Li.Ol I 0
_ _ _ _
E:
{
0.0021
0.~020 I
, 6.~
} I
4.7 {
! ~0
~
""
a,a
5
[
1o.o 0.4 2u.0 0. t6 5
~
1 ,
.~ ~O.a
} 4.7
I
4.7
t
AL intensities are given in % of all decays. Toe transition in~ait~.es in the t ~ t cotun-m ar~ mainly Imsed on Iy vale., which ar~ obtained ~Jydividing the conv~rs~m Iir~ inter~Ities by the adopt ~d c~K's. a) E2/M: ; .~to based on K/L =4.5+ 0.6 and LI ~ Ill/1£II -~4.6± 0.6. givL'%g~2 = E2/MI = 0 25~0.3
b) Based onR L =5±1, giving only rougbl:~ '2-eE2 co~tent. c) ~{esultfrom '55 d Lu 177 dec iy 7), d~ the 150.8 keV ~a'ansition is a s~ow El transition with abnormal co~version ooeff|clent~ 5).
T:~ble 2 ir~ensitms of ~-grou~ Energy. of daughter 1~., el 0 12t .6 1"0.8 289 123i 1241
Transition
Inmns :ty
energy
~7o~
lcgft f
1400 1280 1250 ~110 i 7O I60
00 9 t7 2 6 5
7.2 0.8 7.5 4,4 ~.4
6.6 "!
the uncertaintK-~ of the log q vahm~ arc about 0.2
84
I I I
to M r . Sven B j ~ r n h o i m f o r p u t t i n g t h e Yb 177 me" f o i l a t o u r d i s p o s a l D r . G . T . Ewmn h a s k i n d l y c o m m u n i c a t e d to u s Me Chalk R i v e r r e s u l t s p r i o r to p u b l i c a t i o n . 1} J . M Cork et sic, Phys Rev. I01 (1956) 1942. 2) J, P. Mize, M. E. Bunker and J . W . S t a r n e r , Phys. Rev. 103 (1956) 132. a) B.R Motteb o~ and S.C,.Nils~n, prorate comm~mieatier.. 4) B.R MottoI~or .m~t S.G,Nilsson, Mat Fys, Skit. Dan. Vid. Sclsk. I (19591 ,la. ~. 5} G, T. Ewaa. private comm,laicativn, 6) F . R . P e l e r s e n and H A.Shugart, Phys. Rcv. i26 (1962) 252. 7) L.¥e-istensen et a L . Physics Letters 8 (1963~ 57.