24 Identifying Nilsson States in A β-Decay Properties 1
1
1
≡100 Nuclei by Investigating Gross 1
2
2
K.-L. Kratz , H. Gabelmann, W. Ziegert , V. Harms , J. Krumlinde , and P. Möller 1
Institut für Kernchemie, Universität Mainz, D-6500 Mainz, Federal Republic of Germany Department of Mathematical Physics, Lund Institute of Technology, Lund University, Box 118, S-22100 Lund, Sweden
Downloaded via TUFTS UNIV on July 13, 2018 at 05:05:58 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
2
Since most nuclei in the region of deformation at A~ 100 can only be produced with rather low yields which makes detailed spectroscopic studies d i f f i c u l t , we have examined p o s s i b i l i t i e s of extracting nuclear structure information from easily measurable gross β-decay properties. As examples, comparisons of recent experimental results on Rb-Y and Rb-Y to RPA shell model calculations using Nilsson-model wave functions are presented and discussed. 99
101
The existence of strong deformation for neutron-rich A~100 nuclei was already extablished 15 years ago [CHE70], and data continue to collect on this region up to now. They revealed a rather complex picture indicating rapid nuclear shape changes and shape coexistence [BEN84,MEY85] which can be related to the occurrance of several (quasi-) spherical and deformed subshells for both Ζ and Ν (see Fig.1). While in the past years spec troscopic studies were mainly restricted to even-even nuclei, more recent investigations have turned towards odd-mass nuclei which allowed f i r s t conclusions on individual Nilsson orbitals as well as the determination of the Nilsson Hamiltonian in theA~100mass region (see e.g. [SIS84]). Usually, characterization of nuclear structures in transitional nuclei requires rather sophisticated spectroscopic investigations, e.g. measure ments of level life-times, γ - t r a n s i t i o n multipolarities and magnetic mo ments. Unfortunately, most of the nuclei of interest in the A-100 mass region are fission products far from β - s t a b i l i t y which - at present - can only be produced with rather low yields. This makes detailed spectroscopic studies very time-consuming, and in a number of cases even impossible. Therefore, we have examined p o s s i b i l i t i e s of determining shape transitions and Nilsson states in very-neutron-rich nuclei via correlated changes in easily measurable gross β-decay properties, such as the h a l f - l i f e (T1/2), the delayed neutron emission probability ( P ) , or the gross β-brancning pattern in terms of the β-strength function (Sg). To be more specific, we thoroughly compare existing experimental data on these quantities with shell model [KRU84] expectations for different nuclear structures, and from agreement, respectively disagreement between measurements and predictions information on Nilsson parameters (χ, μ, odd-particle states) and deformation is deduced. n
The trigger for this attempt was the observation of strong variations in the shape of Sg of neutron-rich odd-mass Rb isotopes [KRA81,83,84] which could be related to the spherical N=56 subshell closure and to the sudden onset of strong deformation at the deformed N=60 shell gap (see F i g . l ) . In 0097-6156/86/ 0324-0165506.00/ 0 © 1986 American Chemical Society
Meyer and Brenner; Nuclei Off the Line of Stability ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
166
NUCLEI OFF THE LINE OF STABILITY
F i g . l . S i n g l e - p a r t i c l e l e v e l s f o r p r o t o n s and n e u t r o n s i n t h e A=100 r e g i o n f o r t h e m o d i f i e d o s c i l l a t o r p o t e n t i a l o f t h e N i l s s o n model as a f u n c t i o n o f p r o l a t e d e f o r m a t i o n . t h e case o f t h e N=60 i s o t o n e R b , t h e shape o f S$ l e a d t o t h e n [ 4 3 1 3 / 2 ] assignment f o r the ground s t a t e ( g . s . ) o f t h i s n u c l e u s , which c o n s t i t u t e d some o f t h e f i r s t e v i d e n c e f o r e s t a b l i s h i n g d e f o r m a t i o n i n medium-mass o d d n u c l e o n i s o t o p e s . To g i v e an example f o r t h e p o s s i b l e s e n s i t i v i t y o f s h e l l s t r u c t u r e on g r o s s β - d e c a y p r o p e r t i e s , i n F i g . 2 t h e s i t u a t i o n f o r 9 7 R is shown i n a s i m p l i f i e d , s c h e m a t i c way. As i s d i s c u s s e d i n some d e t a i l in [ K R A 8 3 , 8 4 ] , d e p e n d i n g on t h e v a l e n c e - p r o t o n N i l s s o n o r b i t a l , q u i t e d i f f e r e n t shapes o f 5β w i l l o c c u r . W i t h t h e π [ 3 0 1 3 / 2 ] c o n f i g u r a t i o n , Sg w i l l have a d i s t r i b u t i o n s i m i l a r t o t h a t shown i n t h e u p p e r p a r t o f F i g . 2 , w i t h t h e l o w e s t G a m o w - T e l l e r (GT) t r a n s i t i o n ( v g-//2 - * - n g g / 2 ) a t medium e x c i t a t i o n e n e r g y . T h i s w i l l r e s u l t i n a ' l o n g ' Τ χ / 2 and a ' h i g h ' P - v a l u e . For t h e c o n n e c t i o n o f b o t h q u a n t i t i e s t o S R , see [ K R A 8 4 ] . On t h e o t h e r h a n d , when assuming t h e odd p r o t o n in the [431 3 / 2 ] N i l s s o n o r b i t a l , p a r t o f the 97/2-* 9?/2 strength w i l l be s h i f t e d down t o ( n e a r ) t h e g . s . o f Sr, r e s u l t i n g i n an S$ d i s t r i b u t i o n s i m i l a r t o t h a t i n t h e l o w e r p a r t o f F i g . 2 . T h i s w i l l g i v e a ' s h o r t ' Τχη and a ' l o w ' P . I t i s r e a s o n a b l e t o assume t h a t such d i f f e r e n c e s i n β-decay p r o p e r t i e s w i l l o c c u r a l s o f o r o t h e r o d d p a r t i c l e n u c l e i i n t h e A-100 mass r e g i o n , t h u s p r o v i d i n g a new and s i m p l e method f o r an i d e n t i f i c a t i o n o f N i l s s o n s t a t e s . 9 7
d
n
ν
π
9 7
n
MOT [ 1
Fig. 2. Schematic m o d e l - S ^ ' s f o r t h e decay o f a f a r - u n s t a b l e n u c l e u s , as e . g . R b , and t h e i r i n f l u e n c e on Τ χ / 2 and P . F o r d i s c u s s i o n , see t e x t . 9 7
n
3
2-10
T
A good example f o r t e s t i n g t h e a p p l i c a b i l i t y o f o u r approach i s t h e β-decay o f t h e o d d - p r o t o n (Z=37) n u c l e u s R b t o t h e o d d - n e u t r o n (N=61) daughter S r . As was shown i n Î P F E 8 4 ] , even f r o m a r a t h e r t i m e - c o n s u m i n g spectroscopic i n v e s t i g a t i o n of 99R decay a t OSTIS, r e s u l t i n g i n g . s . band properties considerably improved over those reported in an earlier 9 9
9 9
d
Meyer and Brenner; Nuclei Off the Line of Stability ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
24.
167
Identifying Nilsson States
KRATZ ET AL.
p u b l i c a t i o n [W0H83], an unambiguous N=61 N i l s s o n o r b i t a l a s s i g n m e n t was n o t possible since both calculated (gK"9R)/Qo curves f o r ν [ 4 1 1 3 / 2 ] and v[541 3 / 2 ] overlapped w i t h the experimental value f o r deformations of ε>0.3. However, we were able to demonstrate^ t h a t , when including β - i n t e n s i t y arguments f o r t h e decays o f m o t h e r and d a u g h t e r n u c l e u s ( i n p a r t i c u l a r l o g f t - v a l u e s f o r t h e Rb-^Sr and S r - * Y g . s . t o g . s . t r a n s i t i o n s ) , and w i t h a d d i t i o n a l c o m p a r i s o n t o s h e l l model p r e d i c t i o n s u s i n a t h e N=60 N i l s s o n p a r a m e t e r s e t [KRU84], t h e v [ 5 4 1 3 / 2 ] o r b i t a l f o r t h e ^ S r g r o u n d band c o u l d be r u l e d o u t . I n t h i s w a y , a l s o two e x c i t e d r o t a t i o n a l bands built on the v[413 5/2] and v [ 4 2 2 3 / 2 ] Nilsson configurations were i d e n t i f i e d (see F i g . l o f [ P F E 8 4 ] ) . I t s h o u l d be p o i n t e d o u t i n t h i s c o n t e x t , t h a t good agreement between e x p e r i m e n t a l e n e r g i e s and l o g f t - v a l u e s f o r t h e d i f f e r e n t band heads w i t h s h e l l model p r e d i c t i o n s can be o b t a i n e d , p r o v i d e d an a p p r o p r i a t e c h o i c e o f N i l s s o n p a r a m e t e r s and d e f o r m a t i o n i s made. As i s d e m o n s t r a t e d i n [KRU84] f o r n e u t r o n - r i c h Rb i s o t o p e s and as w i l l be more g e n e r a l l y discussed f o r the A = 80-110 r e g i o n i n [KRA85], N i l s s o n parameters fitting experimental data o f spherical nuclei near s t a b i l i t y , l i k e the s t a n d a r d A=100 s e t o f [ L A R 7 6 ] , t e n d t o become i n a p p r o p r i a t e f o r f a r - u n s t a b l e deformed n u c l e i . T h i s may, f o r e x a m p l e , be t h e r e a s o n f o r some i n c o r r e c t p r o t o n o r b i t a l a s s i g n m e n t s t o band heads i n Y [W0H85] w h i c h were based on BCS+pairing p r e d i c t i o n s using N i l s s o n parameters a d j u s t e d t o s i n g l e - p a r t i c l e levels of near-stable Y isotopes. 9 9
I n p r i n c i p l e , t h e same c o n c l u s i o n on t h e N i l s s o n o r b i t a l o f t h e Sr g . s . as o b t a i n e d by t h e above m e n t i o n e d γ - s p e c t r o s c o p i c work can a l r e a d y be drawn from a comparison of easily measurable g r o s s β-decay features (requiring ~ 5 h m e a s u r i n g t i m e f o r β- and n - m u l t i s c a l i n g , compared t o ~ 3 weeks f o r γ - s p e c t r o s c o p y ) t o p r e d i c t i o n s o f o u r RPA s h e l l m o d e l . I n t h e 9 9
Nilsson states 37th7T
61st ν
[3013/ ] - [413 s/ ] 2
2
[ 3 0 1 -
[541 /2] 3
Shell model
TVzlms]
©
190
39
205
66
420
59
[312 3/2] - [404*2]
P
[%]
n
Shell model [440 >2] - [411 3/2] 1
[431 3/ ] - [411 3/ ] 2
2
®
[431 4] - [532 /2] 3
5
I 59*1 I
I
20 *
21
Energy [MeV]
Fig.3. Comparison o f t h e e x p e r i m e n t a l d i s t r i b u t i o n o f R b decay w i t h RPA s h e l l model p r e d i c t i o n s ( m i d d l e p a r t ) i n v o l v i n g d i f f e r e n t o d d - p a r t i c l e N i l s s o n s t a t e s l y i n g near t h e Fermi l e v e l ( l e f t p a r t ) . I n t h e r i g h t p a r t , t h e c o r r e s p o n d i n g Λ\ιι and P v a l u e s a r e l i s t e d . 9 9
n
Meyer and Brenner; Nuclei Off the Line of Stability ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
168
NUCLEI OFF THE LINE OF STABILITY
middle p a r t o f F i g . 3 , the β - s t r e n g t h p a t t e r n f o r R b decay o b s e r v e d i n e x p e r i m e n t i s compared t o ( s c h e m a t i c a l ) Sg p r e d i c t i o n s i n v o l v i n g t h e o d d p a r t i c l e N i l s s o n s t a t e s shown i n t h e l e f t p a r t o f t h e f i g u r e . Two d i f f e r e n t types of strength distributions are c a l c u l a t e d : (a) w i t h o u t low-lying G T - s t r e n g t h , and ( b ) w i t h g . s . t o ( n e a r ) g . s . G T - t r a n s i t i o n s . I n t h e r i g h t p a r t o f F i g . 3 , t h e c o r r e s p o n d i n g m o d e l - Τ χ / 2 and P a r e l i s t e d t o g e t h e r w i t h o u r e x p e r i m e n t a l v a l u e s . C l e a r l y , f r o m b o t h t h e shape o f as w e l l as f r o m Τ χ / 2 and P , t h e N i l s s o n o r b i t a l c o m b i n a t i o n s f o r t y p e ( a ) decay p a t t e r n s can be e x c l u d e d . F u r t h e r m o r e , f o r t y p e ( b ) s t r e n g t h f u n c t i o n s t h e n [ 4 4 0 1 / 2 ] - v [ 4 1 1 3 / 2 ] c o m b i n a t i o n can be r u l e d o u t - a l t h o u g h h a v i n g t h e c o r r e c t S$ shape - because t h e e s t i m a t e d P v a l u e i s a f a c t o r 2 . 5 t o o l o w . W i t h t h i s , t h e [ 4 3 1 3 / 2 ] o r b i t a l can be a s s i g n e d t o t h e 3 7 t h p r o t o n i n Rb, while for t h e 6 1 s t n e u t r o n no d i s t i n c t i o n between t h e N i l s s o n s t a t e s [ 4 1 1 3 / 2 ] and [532 5 / 2 ] i s p o s s i b l e f r o m t h e g r o s s β-decay p r o p e r t i e s o f t h i s i s o t o p e . However, a s i m i l a r c o m p a r i s o n o f t h e o r e t i c a l Τ χ / 2 and P w i t h e x p e r i m e n t a l data f o r S r decay (see T a b . l ) a l l o w s t h e unambiguous a s s i g n m e n t o f t h e v[411 3 / 2 ] o r b i t a l t o the g . s . of S r and, moreover, c o n f i r m s the e a r l i e r assignment o f the π[422 5 / 2 ] o r b i t a l f o r the Y g r o u n d band [M0N82]. 9 9
n
n
n
9 9
n
9 9
9 9
9 9
Tab.l. Comparison o f e x p e r i m e n t a l T l / 2 and P f o r S r t o s h e l l model predictions f o r d i f f e r e n t odd-par t i c l e N i l s s o n o r b i t a l s near the Fermi l e v e l
N i l s s o n states 61st ν 39th π
L
l / 2 [ms]
9 9
n
413 411 411 541 532 [411
550 431 3/2 5/2 177 431 3/2 3/2 190 301 3/2 3/2 1065 431 3/2 3/2 1172 422 5/2 5/2 3/2] - [422 5/2] 275 Experiments 285-15
0.29 0.03 0.03 0.34 1.21 0.20 0.19*0.10 1
The second example i s r e l a t e d t o t h e p o s s i b l e i d e n t i f i c a t i o n o f N i l s s o n s t a t e s i n o d d - n u c l e o n A=101 i s o t o p e s . I n t h e case o f ^ R b , t h e 3 7 t h p r o t o n may occupy t h e [ 3 0 1 3 / 2 ] , [ 4 3 1 3 / 2 ] o r [312 3 / 2 1 N i l s s o n o r b i t a l , and s i m i l a r l y t h e 6 3 r d n e u t r o n i n t h e d a u g h t e r n u c l e u s ^ S r may be i n d i f f e r e n t s t a t e s n e a r t h e Fermi s u r f a c e (see F i g . l ) . The c o r r e s p o n d i n g o d d - p a r t i c l e N i l s s o n o r b i t a l c o m b i n a t i o n s may a g a i n y i e l d d i f f e r e n t S3 d i s t r i b u t i o n s a n d , consequently, different Τχ/2 and P (see F i g . 4 ) . From a v e r y recent e x p e r i m e n t p e r f o r m e d a t CERN-ISOLDE, a r a t h e r s h o r t β-decay h a l f - l i f e o f T i / 2 = ( 3 2 ± 5 ) ms and a r e l a t i v e l y low P - v a l u e o f (24+5) % were o b t a i n e d . Com p a r i s o n o f t h e s e ( p r e l i m i n a r y ) r e s u l t s w i t h o u r s h e l l model predictions favours an S$ of type (b) and thus suggests the τι[431 3 / 2 ] g.s. c o n f i g u r a t i o n f o r the precursor ^ R b , b u t i t c a n n o t d e t e r m i n e t h e N=63 Nilsson assignment f o r S r . However, as i n t h e A=99 c a s e , t h i s a m b i g u i t y can be removed by c o n s i d e r i n g g r o s s β-decay p r o p e r t i e s o f t h e l a t t e r n u c l e u s to levels in * Y (see F i g . 5 ) . A p a r t f r o m an o l d e r measurement a t ISOLDE w h i c h y i e l d e d a Τχ/2 o f a b o u t 180 ms, t h e o n l y o t h e r i n f o r m a t i o n on Sr decay comes f r o m r e c e n t s t u d i e s a t TRISTAN. Wohn e t a l . [W0H83] have e s t a b l i s h e d two r o t a t i o n a l bands i n Y , and Reeder e t a l . [REE85] have measured Τ χ / 2 and P f o r t h e Sr p r e c u r s o r . As can be seen f r o m F i g . 5 , a c o m p a r i s o n o f t h e s e e x p e r i m e n t a l d a t a w i t h o u r s h e l l model p r e d i c t i o n s f o r d i f f e r e n t N i l s s o n o r b i t a l c o m b i n a t i o n s f o r t h e 6 3 r d n e u t r o n and t h e 3 9 t h proton suggests the [411 3 / 2 ] assignment f o r the S r g . s . and c o n f i r m s t h e n[422 5 / 2 ] c o n f i g u r a t i o n f o r the Y g r o u n d band [W0H83]. F u r t h e r m o r e , d e f o r m a t i o n s o f ε = 0 . 3 5 ΐ 0 . 0 3 can be deduced f o r b o t h i s o t o p e s . n
n
1 0 1
1 0
1 0 1
1 0 1
n
1 0 1
1 0 1
Meyer and Brenner; Nuclei Off the Line of Stability ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
24.
KRATZ ET AL.
169
Identifying NUsson States
Nilsson states 37th7r
63rdv
^
[3013/i ] - [413 5/ ]
1
[31234] - [411 3/]
^
2
2
[43134]- [532 54]
f
[4313/2] - [411 3/]
~
2
I Shell model |
®^
TMms]
W
®
\
219
100
46
29
48
28
a
Exp.: [32^51 1
1
1
θ"
5 Energy [MeV]
10
[%]
n
83
1 Shell model |
"ou CO
P
108
Γ24±Π
F i g . 4 . S h e l l model p r e d i c t i o n s o f Sg d i s t r i b u t i o n s o f Rb decay ( m i d d l e p a r t ) i n v o l v i n g d i f f e r e n t o d d - p a r t i c l e N i l s s o n o r b i t a l s ( l e f t p a r t ) . In the r i g h t p a r t , the corresponding m o d e l - Τ χ / 2 and P a r e l i s t e d and compared t o e x p e r i m e n t a l d a t a . 1 U i
n
Nilsson states 39th π
TV [ms]
Shell model
63 rd ν
2
[4313/2] - [4135/2]
232
[43134] - [541 4] 3
[301 34] - [532 54] [422 54] - [532 54]
ι*
P
[%]
n
1.6
Shell model
338
1.85
®
546
4.3
473
3.8
Shell model [422 4 ] - [4113/ ] 5
2
©
160
10
1115/180 I I 2.5±0.3 |
Energy [MeV]
F i g . 5. S h e l l model p r e d i c t i o n s o f Sg d i s t r i b u t i o n s o f 1 0 1 decay ( m i d d l e p a r t ) i n v o l v i n g d i f f e r e n t o d d - p a r t i c l e N i l s s o n s t a t e s n e a r t h e Fermi s u r f a c e ( l e f t p a r t ) . I n t h e r i g h t p a r t , t h e c o r r e s p o n d i n g m o d e l - Τ χ / 2 and P a r e compared t o e x i s t i n g experimental data.
S r
n
So f a r , we have c o n s i d e r e d β-decay m o t h e r - d a u g h t e r p a i r s w i t h ( a l m o s t ) i d e n t i c a l g . s . d e f o r m a t i o n s , s i n c e o u r s h e l l model i m p l i c i t l y c o n t a i n s t h i s c o n s t r a i n t [KRU84]. C o n s e q u e n t l y , i n case o f d i f f e r e n t g . s . d e f o r m a t i o n s f o r m o t h e r and d a u g h t e r , o r i n case o f shape c o e x i s t e n c e , o u r method i s l e s s conclusive. Nevertheless, by c a l c u l a t i n g Sp w i t h b o t h d e f o r m a t i o n s and t a k i n g i n a sense t h e ' a v e r a g e ' o f b o t h p r e d i c t i o n s , we can a t l e a s t deduce some i n f o r m a t i o n on t h e e f f e c t i v e structure p r o p e r t i e s o f such n u c l e i . F o l l o w i n g t h i s l i n e , we c a n , f o r e x a m p l e , d e m o n s t r a t e t h a t t h e g e n e r a l shape o f S$ as w e l l as Τ χ / 2 and P o f ^ R b ]y u n d e r s t o o d when assuming a g.s. deformation of ε » 0 . 3 f o r t h e p r e c u r s o r and ε < 0 . 2 f o r t h e g . s . o f t h e d a u g h t e r . Moreover, i n o r d e r t o reproduce the magnitude o f the e x p e r i m e n t a l S(3, we have t o assume a change i n d e f o r m a t i o n t o ε ^ 0 . 3 f o r l e v e l s above 0 . 5 MeV i n S r . This observation is c o n s i s t e n t w i t h the i n t e r p r e t a t i o n of n
c
a
n
o n
D e
9 7
Meyer and Brenner; Nuclei Off the Line of Stability ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
170
NUCLEI OFF T H E LINE OF STABILITY
shape c o e x i s t e n c e i n t h i s N=59 i s o t o n e [PFE81,KRA83,MEY85] and d e t e r m i n e s t h e g . s . c o n f i g u r a t i o n o f ^Sr t o be [ 4 1 1 3 / 2 ] , i n c o n t r a s t t o o u r e a r l i e r assignment o f J = l / 2 [PFE81]. In summary, we have d e m o n s t r a t e d that the comparison o f present generation shell model predictions for very-neutron-rich odd-nucleon i s o t o p e s i n t h e A - 100 r e g i o n w i t h e x p e r i m e n t a l gross β-decay p r o p e r t i e s may serve to identify, within limits, nuclear shape changes and Nilsson parameters, and t o d e t e r m i n e n u c l e a r d e f o r m a t i o n . However, in order to deduce r e l i a b l e i n f o r m a t i o n c a r e must be e x c e r c i s e d when s e l e c t i n g the s i n g l e - p a r t i c l e p a r a m e t e r s i n t h e models used i n t h e c a l c u l a t i o n o f β-decay p r o p e r t i e s . W i t h t h i s , t h e o r e t i c a l e s t i m a t e s o f Τ χ / 2 and decay p a t t e r n s may s e r v e as a v a l u a b l e g u i d e t o t h e s e l e c t i o n o f e x p e r i m e n t s f o r i n v e s t i g a t i n g e x o t i c i s o t o p e s o f unknown p r o p e r t i e s , and - more g e n e r a l l y - may r e s u l t i n more r e l i a b l e e x t r a p o l a t i o n s up t o t h e n e u t r o n d r i p l i n e . For e x a m p l e , w i t h r e g a r d t o a s t r o p h y s i c a l a p p l i c a t i o n , o u r s h e l l model p r e d i c t i o n s o f Τ χ / 2 , b e i n g on t h e average a f a c t o r o f two l o n g e r t h a n t h o s e e s t i m a t e d by K l a p d o r e t a l . [KLA84], might (again) r a i s e questions about the p l a u s i b i l i t y of r-process nucleosynthesis in He-burning environments. n
+
Acknowledgment Thanks a r e due t o t h e o r g a n i z e r s o f t h i s symposium and t o t h e ACS. Withoul t h e i r s u p p o r t , K . - L . K r a t z and P. M o l l e r c o u l d n o t have p a r t i c i p a t e d . This work was s u p p o r t e d by t h e German BMFT and by t h e Swedish NSRC.
[BEN84] [CHE70] [KLA84] [KRA81] [KRA83] [KRA84] [KRA85] [KRU84] [LAR76] [MEY85] [MON82] [PFE81] [PFE84] [REE85] [SIS84] [WOH83] [WOH85]
References R. Bengtsson et a l . , Phys. Scripta 29 402 (1984). E. Cheifetz et a l . , Phys. Rev. Lett. 25 38 (1970). H.V. Klapdor et a l . , At. Data Nucl. Data Tables 31 81 (1984). K.-L. Kratz et a l . , Proc. 4th Int. Conf. on Nuclei Far From Stabi l i t y , Helsingør, Denmark, CERN 81-09 317 (1981). K.-L. Kratz et a l . , Z. Physik A312 43 (1983). K.-L. Kratz, Nucl. Phys. A417 447 (1984). K.-L. Kratz et a l . , 'Beta-Strength Function Systematics of A = 100 Nuclei', to be published. J. Krumlinde and P. Möller, Nucl. Phys. A417 419 (1984). S.E. Larsson et a l . , Nucl. Phys. A261 77 (1976). R.A. Meyer, Hyperfine Interactions 22 385 (1985), and Refs. therein. E. Monnand et a l . , Ζ. Physik A306 183 (1982). Β. Pfeiffer et a l . , Proc. 4th Int. Conf. on Nuclei Far From Stabi l i t y , Helsingør, Denmark, CERN 81-09 423 (1981). Β. Pfeiffer et a l . , Z. Physik A317 123 (1984). P.L. Reeder et a l . , these proceedings. K. Sistemich et a l . , Proc. Int. Symp. on In-Beam Nuclear Spectros copy, Debrecen, Hungary, Vol. I 51 (1984), and Refs. therein. F.K. Wohn et a l . , Phys. Rev. Lett. 51 873 (1983). F.K. Wohn et a l . , Phys. Rev. C31 621 and 634 (1985),and these proceedings.
RECEIVED August 20, 1986
Meyer and Brenner; Nuclei Off the Line of Stability ACS Symposium Series; American Chemical Society: Washington, DC, 1986.
