This work was supported by National Science Foundation Grant PHY 75-00289 and Indiana Universit

Gray, W.S.

Griffin, H.C.

Smith, H.A. Jr.

Tickle, R.S.

English

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NUCLEAR STRUCTURE STUDIES OF LIGHT-MASS RADON ISOTOPES USING THE 2 0 9 ~ i ( 6 ~ i ,  xny) REACTIONS 
R.S. Tickle*, W.S. Gray*, H.C. Griff in*,  and H.A. Smith, Jr. 
The methods of in-beam y-ray spectroscopy,  e x c i t a t i o n  funct ions  and hence t o  a s s ign  prompt 
employing the  r e l a t i v e l y  ene rge t i c  6 ~ i  beams y- t rans i t ions  t o  s p e c i f i c  nucl ides ,  c ross  s ec t ions  
ava i l ab l e  a t  IUCF, a r e  being used t o  s tudy t h e  f o r  t h e  6~ i - induced  r eac t ions  have been determined 
proton-rich i so topes  2 0 9 ~ n  and 210~n. A 1  though from ana lys i s  of t h e  o f f - l i ne  a c t i v i t y  measurements. 
t he  unique p rope r t i e s  of (ion,xny) r eac t ions  have Some of our prel iminary cross  s ec t ion  r e s u l t s  f o r  
been explo i ted  i n  many p a r t s  of t he  pe r iod ic  6 ~ i  reac t ions  on 209~i  a r e  shown i n  Table 1. A t  
t a b l e  t o  study nuc l e i  which a r e  f a r  from the  l i n e  65 MeV, which is probably c lo se  t o  t he  optimum f o r  
of s t a b i l i t y  and hence o f t e n  otherwise inacces- t he  6n r eac t ion ,  some 7n r eac t ion  leading  t o  2 0 8 ~ n  
s i b l e ,  l i t t l e  a t t e n t i o n  has been devoted thus f a r  t o  was expected but  not  observed. While t he  y rays  i n  
t he  i n t e r e s t i n g  region  beyond bismuth. t he  decay of 2 0 8 ~ n  (24 min; 80% EC) a r e  unknown, t he  
Two po in t s  on the  e x c i t a t i o n  funct ions  f o r  y rays  a r e  known i n  t he  decay of t he  daughter, 2 0 8 ~ t  
the  209~i (6~i ,  5ny) 210~n and 209~i  ( 6 ~ i ,  6ny) 209Rn (1.6 h r ;  99% EC), but  were not  seen i n  t he  decay 
fusion-evaporation r eac t ions  have been measured by spec t ra .  The 6n c ros s  s ec t ion  was determined from 
bombarding self-support ing t a r g e t s  of 209~i with  t h e  daughter 2 0 9 ~ t  a c t i v i t y  r a t h e r  than from t h e  
55 MeV and 65 MeV 6 ~ i  ions.  I n  add i t i on  t o  parent  2 0 9 ~ n ,  where t he  y branching i s  uncer ta in .  
measuring in-beam s i n g l e s  t o  determine t h e  in-  A t  both energies  t he  expected growth of t h e  2 0 9 ~ t  
t e n s i t i e s  of r e l a t i v e l y  prompt y- t rans i t ions ,  o f f -  a c t i v i t y  was observed wi th  no evidence f o r  d i r e c t  
l i n e  measurements of t a r g e t  r e s i d u a l  y - a c t i v i t i e s  production of 2 0 9 ~ t .  
were made f o r  periods of  1-2 hours fol lowing each The c ros s  s ec t ion  f o r  t h e  5n r eac t ion  cannot 
bombardment. While add i t i ona l  bombardments a t  be determined from our decay da ta .  The r e s idua l  
o the r  energies  a r e ' s t i l l  needed t o  complete t h e  nucl ide ,  210~n,  decays pr imar i ly  by a emission 
t o  t he  ground s t a t e  of  8.8-day *06po wi th  a very 
Table 1. Measured cross  s ec t ions  f o r  production 
of s e l ec t ed  nuc l e i  by (6~i ,  xn) Reactions on weak 4% EC branch t o  210~t. The y rays  a s soc i a t ed  
209Bi t a r g e t ,  
wi th  t h e  EC decay of 210~n a r e  unknown. However, 
Cross Sect ion  (mb) 
Reaction 55 MeV 65 MeV t r a n s i t i o n s  from t h e  decay of * l O A t  a r e  being pro- 
( 6 ~ i ,  7n) 2 0 8 ~ n  -- -- duced d i r e c t l y .  Entrance channel breakup of t he  
@Li, 6n) 209Rn 15 7 615 6Li i on  i n t o  a + d followed by the  2 0 9 ~ i ( a , 3 n )  
( 6 ~ i ,  4n) 2 1 1 ~ n  182 -- *''At r e ac t ion  is the most l i k e l y  mechanism. The 
( 6 ~ i ,  d3n) 210~t 189 185 optimum a -pa r t i c l e  energy f o r  t h i s  r eac t ion  i s  
est imated t o  be 40 MeV from a simple semi-empirical 
r e l a t i onsh ip .  Assuming the  a p a r t i c l e ,  a f t e r  
-85- 
breakup, c a r r i e s  2 / 3  of t h e  6 ~ i  energy, 
i t  would have 36.7 and 43.3 MeV re spec t ive ly  
a t  bombarding energies  of  55 and 65 MeV. There- 
f o r e  one would expect ,  a s  observed, t h e  cross  
s ec t ions  f o r  t h e  ( 6 ~ i ,  d3n)210~t r e a c t i o n  t o  be  
s i m i l a r  a t  t h e  two bombarding energies.  
I n  add i t i on  t o  t he  in-beam s i n g l e s  and of f -  
l i n e  a c t i v i t y  measruements, we have measured in-  
beam y-y coincidences (% 30 x l o6  events )  from 
6 ~ i  + 'O9gi. r e a c t i o n s  a t  65 MeV.  Using two Ge(Li) 
de t ec to r s  a t  900 wi th  respect  t o  t he  beam 
d i r ec t ion ,  4-parameter (El, E2 ,y-y TAC ,y-FU? TAC) 
coincidence da t a  were recorded event  by event  and 
s to red  on magnetic tape.  The tapes  have been 
so r t ed  o f f - l i ne  using t h e  Univers i ty  of Michigan 
Amdahl 4 7 0 ~ 1 6  computer and ana lys i s  of t he  r e s u l t s  
is  i n  progress.  
The bulk of  t h e  experimental  work w i l l  be 
completed i n  t he  near f u t u r e  by measuring ad- 
d i t i o n a l  po in t s  on t h e  e x c i t a t i o n  funct ions  and 
by measuring y-ray angular  d i s t r i b u t i o n s .  
*University of Michigan, Ann Arbor, Michigan. 
4 8104 


Nuclear Structure Studies of Light-Mass Radon Isotopes Using the 209-Bi(6-Li,xnγ) Reactions

https://scholarworks.iu.edu/dspace/bitstream/2022/3040/1/iucf_1976_85-86.pdf

Nuclear Structure Studies of Light-Mass Radon Isotopes Using the 209-Bi(6-Li,xnγ) Reactions

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