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Odd-even isotope shifts in the atomic spectrum of tin
Volume 29A, number 5
ODD-EVEN
PHYSICS LETTERS
ISOTOPE
SHIFTS
IN THE
ATOMIC
19 May 1969
SPECTRUM
OF
TIN
J. D. SILVER and D. N. STACEY
Clarendon Laboratory. Oxford, UK Received 21 April 1969
Measurements of odd-even isotope shifts in the line X 3283 A of the atomic spectrum of tin are reported. These are compared with previous work, and revised values of staggering coefficient are given.
M e a s u r e m e n t s of isotope shifts in a t o m i c s p e c t r a afford an opportunity to study changes i n n u c l e a r charge d i s t r i b u t i o n f r o m one isotope of a n e l e m e n t to another. In t h i s context, tin i s a p a r t i c u l a r l y i n t e r e s t i n g e l e m e n t , b e c a u s e the n u c l e a r d e f o r m a t i o n s of the isotopes a r e s m a l l , so that r a d i a l effects a r e p r i m a r i l y r e s p o n s i b l e for the o b s e r v e d field shifts, and can be studied d i r e c t l y . F u r t h e r , m e a s u r e m e n t s of m u - m e s i c isotope shifts [1] e x i s t for s e v e r a l isotope p a i r s in tin, m a k i n g d e t a i l e d c o m p a r i s o n s of the r e s u l t s of the two types of e x p e r i m e n t p o s s i b l e . Shifts b e t w e e n the even isotopes i n t h r e e optical l i n e s have b e e n studied [2-4], but the only publ i s h e d datum for the o d d - e v e n shifts [4] is of much lower quoted a c c u r a c y , s i n c e it was o b t a i n e d by a method l i a b l e to s y s t e m a t i c e r r o r . The p r e s e n t i n v e s t i g a t i o n was u n d e r t a k e n to p r o vide r e l i a b l e data for t h e s e shifts, to e n a b l e c o m p a r i s o n s both with m u - m e s i c r e s u l t s and with those of optical i n v e s t i g a t i o n s in n e i g h b o u r ing e l e m e n t s ( s u m m a r i z e d by King et al. [5]). R e s u l t s for the shifts involving l l T S n and l l g s n a r e r e p o r t e d h e r e , though it is intended to obtain f u r t h e r data and to extend the work to include the r a r e isotope l l 5 S n . A direct-recording Fabry-Perot interferometer [6] was u s e d to obtain p r o f i l e s of ~ 3283 ~ in the a t o m i c s p e c t r u m of tin, excited in hollow-cathode d i s c h a r g e t u b e s as d e s c r i b e d in ref. [4]. Two or t h r e e m i l l i g r a m s of i s o t o p i c a l l y e n r i c h e d s a m p l e s of high p u r i t y w e r e u s e d i n each cathode. One cathode contained an odd isotope, a s e c o n d cont a i n e d 120Sn, and these w e r e exposed i n a l t e r n a t e o r d e r s of i n t e r f e r e n c e d u r i n g the s a m e scan. The v a l u e s given below a r e b a s e d on m e a s u r e m e n t s with an etalon s p a c i n g of 1.5 cm, which gave the highest r e s o l u t i o n o b t a i n a b l e without
248
o v e r l a p of o r d e r s . R e s u l t s f r o m a 1 c m s p a c e r a g r e e d within t h e i r slightly l a r g e r l i m i t s of e r r o r . erfine splitting: l l 9 S n : 163.6 ± 0.6 mK, n: 155.5 ± 0.6 mK. Shift of C. G. compared with 120Sn, a f t e r allowance foE n o r m a l m a s s s h i f t : l l 9 s n : 12.8 ± 0.6 inK, 17Sn: 32.5 ± 0.6 mK. The r a t i o of the hyperfine s p l i t t ing i s 1.052 ± 0.008 and a g r e e s well with the r a tio 1.047 of the n u c l e a r m o m e n t s . F o r d e t a i l s of the hyperfine splitting i n • 3283 ~ , see [4]. In both c a d m i u m and tin, w h e r e the shift m e a s u r e m e n t s a r e likely to be m o s t a c c u r a t e , the oddodd shift is slightly l a r g e r than the a d j a c e n t e v e n even shifts. The table of s t a g g e r i n g coefficients given i n [5] m a y now be r e v i s e d , and shows a r e c o g n i s a b l e t r e n d in the sequence of e l e m e n t s 44Ru, 48Cd, 50Sn and 52Te. F o r the l i g h t e r odd isotope the values a r e 0.35, 0.83, 1.0 and 1.15, and for the h e a v i e r 0.56, 0.72, 0.70, 1.29. It m u s t be b o r n e in mind, however, that v a l u e s of the s t a g g e r i n g coefficient a r e s e n s i t i v e to (a) the value of the specific m a s s shift, which is u n c e r t a i n , and (b) s m a l l e r r o r s i n the shift m e a s u r e m e n t s . The a u t h o r s a r e indebted to Dr. H. G. Kuhn for his i n t e r e s t in the work and for m a n y valuable discussions.
References 1. R. D. Ehrlich e t a l . , Phys. Rev. Letters 18 (1967) 959. 2. K. Murakawa, J. Phys. Soc. Japan 9 (1954) 876. 3. W . R . Hindmarsh and H. G. Kuhn, Proc. Phys. Soe.
A68 (1955) 433. 4. D.N. Stacey, Proe. Roy. Soc. A280 (1964) 439. 5. W. H. King, H.G. Kuhn and D. N. Stacey, Prec. Roy. Soc. A296 (1967) 24. 6. H.G. Kuhn, E. L. Lewis, D.N. Stacey and J. M. Vaughan, Rev. Sci. Instr. 39 (1968) 86.
ODD-EVEN
PHYSICS LETTERS
ISOTOPE
SHIFTS
IN THE
ATOMIC
19 May 1969
SPECTRUM
OF
TIN
J. D. SILVER and D. N. STACEY
Clarendon Laboratory. Oxford, UK Received 21 April 1969
Measurements of odd-even isotope shifts in the line X 3283 A of the atomic spectrum of tin are reported. These are compared with previous work, and revised values of staggering coefficient are given.
M e a s u r e m e n t s of isotope shifts in a t o m i c s p e c t r a afford an opportunity to study changes i n n u c l e a r charge d i s t r i b u t i o n f r o m one isotope of a n e l e m e n t to another. In t h i s context, tin i s a p a r t i c u l a r l y i n t e r e s t i n g e l e m e n t , b e c a u s e the n u c l e a r d e f o r m a t i o n s of the isotopes a r e s m a l l , so that r a d i a l effects a r e p r i m a r i l y r e s p o n s i b l e for the o b s e r v e d field shifts, and can be studied d i r e c t l y . F u r t h e r , m e a s u r e m e n t s of m u - m e s i c isotope shifts [1] e x i s t for s e v e r a l isotope p a i r s in tin, m a k i n g d e t a i l e d c o m p a r i s o n s of the r e s u l t s of the two types of e x p e r i m e n t p o s s i b l e . Shifts b e t w e e n the even isotopes i n t h r e e optical l i n e s have b e e n studied [2-4], but the only publ i s h e d datum for the o d d - e v e n shifts [4] is of much lower quoted a c c u r a c y , s i n c e it was o b t a i n e d by a method l i a b l e to s y s t e m a t i c e r r o r . The p r e s e n t i n v e s t i g a t i o n was u n d e r t a k e n to p r o vide r e l i a b l e data for t h e s e shifts, to e n a b l e c o m p a r i s o n s both with m u - m e s i c r e s u l t s and with those of optical i n v e s t i g a t i o n s in n e i g h b o u r ing e l e m e n t s ( s u m m a r i z e d by King et al. [5]). R e s u l t s for the shifts involving l l T S n and l l g s n a r e r e p o r t e d h e r e , though it is intended to obtain f u r t h e r data and to extend the work to include the r a r e isotope l l 5 S n . A direct-recording Fabry-Perot interferometer [6] was u s e d to obtain p r o f i l e s of ~ 3283 ~ in the a t o m i c s p e c t r u m of tin, excited in hollow-cathode d i s c h a r g e t u b e s as d e s c r i b e d in ref. [4]. Two or t h r e e m i l l i g r a m s of i s o t o p i c a l l y e n r i c h e d s a m p l e s of high p u r i t y w e r e u s e d i n each cathode. One cathode contained an odd isotope, a s e c o n d cont a i n e d 120Sn, and these w e r e exposed i n a l t e r n a t e o r d e r s of i n t e r f e r e n c e d u r i n g the s a m e scan. The v a l u e s given below a r e b a s e d on m e a s u r e m e n t s with an etalon s p a c i n g of 1.5 cm, which gave the highest r e s o l u t i o n o b t a i n a b l e without
248
o v e r l a p of o r d e r s . R e s u l t s f r o m a 1 c m s p a c e r a g r e e d within t h e i r slightly l a r g e r l i m i t s of e r r o r . erfine splitting: l l 9 S n : 163.6 ± 0.6 mK, n: 155.5 ± 0.6 mK. Shift of C. G. compared with 120Sn, a f t e r allowance foE n o r m a l m a s s s h i f t : l l 9 s n : 12.8 ± 0.6 inK, 17Sn: 32.5 ± 0.6 mK. The r a t i o of the hyperfine s p l i t t ing i s 1.052 ± 0.008 and a g r e e s well with the r a tio 1.047 of the n u c l e a r m o m e n t s . F o r d e t a i l s of the hyperfine splitting i n • 3283 ~ , see [4]. In both c a d m i u m and tin, w h e r e the shift m e a s u r e m e n t s a r e likely to be m o s t a c c u r a t e , the oddodd shift is slightly l a r g e r than the a d j a c e n t e v e n even shifts. The table of s t a g g e r i n g coefficients given i n [5] m a y now be r e v i s e d , and shows a r e c o g n i s a b l e t r e n d in the sequence of e l e m e n t s 44Ru, 48Cd, 50Sn and 52Te. F o r the l i g h t e r odd isotope the values a r e 0.35, 0.83, 1.0 and 1.15, and for the h e a v i e r 0.56, 0.72, 0.70, 1.29. It m u s t be b o r n e in mind, however, that v a l u e s of the s t a g g e r i n g coefficient a r e s e n s i t i v e to (a) the value of the specific m a s s shift, which is u n c e r t a i n , and (b) s m a l l e r r o r s i n the shift m e a s u r e m e n t s . The a u t h o r s a r e indebted to Dr. H. G. Kuhn for his i n t e r e s t in the work and for m a n y valuable discussions.
References 1. R. D. Ehrlich e t a l . , Phys. Rev. Letters 18 (1967) 959. 2. K. Murakawa, J. Phys. Soc. Japan 9 (1954) 876. 3. W . R . Hindmarsh and H. G. Kuhn, Proc. Phys. Soe.
A68 (1955) 433. 4. D.N. Stacey, Proe. Roy. Soc. A280 (1964) 439. 5. W. H. King, H.G. Kuhn and D. N. Stacey, Prec. Roy. Soc. A296 (1967) 24. 6. H.G. Kuhn, E. L. Lewis, D.N. Stacey and J. M. Vaughan, Rev. Sci. Instr. 39 (1968) 86.