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L SUBSHELL FLUORESCENCE AND
COSTER-KRONIG YIELDS FOR Z = 78, 80, 81 AND 82
J. Campbell, P. Mcghee
To cite this version:
J. Campbell, P. Mcghee. L SUBSHELL FLUORESCENCE AND COSTER-KRONIG YIELDS FOR Z = 78, 80, 81 AND 82. Journal de Physique Colloques, 1987, 48 (C9), pp.C9-597-C9-600.
�10.1051/jphyscol:1987998�. �jpa-00227419�
JOURNAL DE PXYSIQUE
Colloque C9, supplkment au no12, Tome 48, dgcembre 1987
L
SUBSHELL FLUORESCENCE AND COSTER-KRONIG YIELDS FORZ
= 78, 80, 81 AND 82J.L. CAMPBELL AND P.L. McGHEE
Guelph W a t e r l o o Program f o r Graduate Work i n P h y s i c s , Guelph Campus, U n i v e r s i t y o f Guelph, Guelph, O n t a r i o , NIG
2W1,Canada
A b s t r a c t
-
X-ray c o i n c i d e n c e measurements of o,! o and fp3 a r e r e ~ o r t e d f o r t h e atomsZ
= 78. 9 0 , 8 1 , 82. S o e c i f i c a t t e n t ! o n 3 i s p a ~ d t o e l i m i n a t i o n o f e x p e r i m e n t a l e r r o r s t h o u g h t t o be r e s p o n s i b l e f o r s c a t t e r i n l i t e r a t u r e r e s u l t s . The p r e s e n t o,
W3 agree c l o s e l y w i t h D i r a c - H a r t r e e - S l a t e r t h e o r y b u t f 2 3 1 5s y s t e m a t i c a l 1% 1 ower t h a n t h e t h e o r e t i c a l v a l u e s . 1. I n t r o d u c t i o n
The l i t e r a t u r e c o n t a i n s many measurements
7f
L s u b s h e l l f l u o r e s c e n c e t o . ) and C o s t e r - K r o n i g ( f . . ) y i e l d s done b y t h e c l a s s i c a l ' K X-ray L x-ray c o i n c i d e n c e t e c h n i q u e I J w i t h r a d i o n u c l i d e X-ray s o u r c e s . These a r e now b e i n g supplemented by p h o t o - i o n i z a t i o n e x p e r i m e n t s u s i n g tuned s y n c h r o t r o n r a d i a t i o n . The o v e r a l l d a t a e x h i b i t s c a t t e r much g r e a t e r t h a n t h a t c l a i m e d f o r i n d i v i d u a l e x p e r i m e n t s , p r e c l u d i n g a c r i t i c a l assessment o f t h e most s o p h i s t i c a t e d p r e d i c t i o n s t o d a t e C11: these a r e ab i n i t i o r e l a t i v i s t i c c a l c u l a t i o n s w h i c h use D i r a c - H a r t r e e - S t a t e r wave f u n c t i o n s t o compute Auger and C o s t e r - K r o n i g t r a n s i t i o n r a t e s and employ e x i s t i n g Dirac-Hartree-Fock c a l c u l a t i o n s C2J o f r a d i a t i v e r a t e s . Most w o r k e r s r e q u i r i n g L s u b s h e l l y i e l d s r e l y upon an e x t e n s i v e s e t o f semi- e m p i r i c a l f i t s t o e x p e r i m e n t a l d a t a , p r o v i d e d b y Krause f 3 1 .The q u a n t i t i e s o. and f i . have many r o l e s . They a r e fundamental p a r a m e t e r s f o r X-ray e m i s s i o n a n a f y s i s . t h e y c o n s t i t u t e t h e b a s i c l i m i t a t i o n on e x t r a c t i o n o f L s u b s h e l l i o n i z a t i o n c r o s s ~ s e c t i o n s f r o m i o n - i n d u c e d L X-ray s p e c t r a . The C o s t e r - K r o n i g p r o b a b i l i t i e s f o r i n t r a - s h e l l vacancy t r a n s f e r i n an i s o l a t e d atom must be well-known i f t h e r e c e n t l y o b s e r v e d a d d i t i o n a l i n t r a - s h e l l t r a n s f e r s i n d u c e d b y s l o w p r o j e c t i l e s a r e t o be u n d e r s t o o d . F i n a l l y t h e f i . v a l u e s appear t o be s e n s i t i v e t o e f f e c t s such a s exchange and r e l a x a t i o n t h a t $ r e o m i t t e d f r o m c u r r e n t c a l c u l a t i o n s .
F o r these reasons. we r e p o r t measurements o f w2, w3 and f Z g f o r the atoms P t , Hg. TB and Pb.
2. E x p e r i m e n t a l Technique f o r L S u b s h e l l Measurements
F i g u r e 1 d e p i c t s the w i d e l y used KX-LX c o i n c i d e n c e t e c h n i q u e i n s c h e m a t i c form. I n t h e s i m p l e s t p o s s i b l e s i t u a t i o n o f a g r o u n d - s t a t e t o g r o u n d - s t a t e e l e c t r o n c a p t u r e decay, t h e numbers of L . X-rays r e c o r d e d i n t h e LX d e t e c t o r c o i n c i d e n t w i t h Kal o r Kap X-rays i n t h e
detector
a r e :Here N s i g n i f i e s c o u n t i n g r a t e o f a Ka 1
it[
i n t h e KX d e t e c t o r . € i s t h e a b s o l u t e LX d e t e c t o r e f f i c i e n c y f o r t h e j L 3 X-ray 1 in e , b 15 t 8 i t 1 in e " s f r a c t i o n a l i n t e n s i t y ,A22 i tr a n g u l a r c o r r e l a t i o n c o e f f i c i e n t a n d 3 i 2 t h e g e o m e t r i c a t t e n u a t i o n .S i n c e t h e L a o r L3Md5 l i n e a r i s e s o n l y f r o m L 3 v a c a n c i e s , we a l s o have
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1987998
JOURNAL DE PHYSIQUE
Lal ILa
T,&ai%anLQie?hqW*i u3, x-ray f Z 3 . col nc can I dence be spectra via these equations.
With more complex decay s c h e m e s involving c a s c a d e s of EC and internal conversion processes, corrections for extraneous coincidences arising between unrelated X-rays can be corrected for by taking coincidences between L X-rays and the KB group.
In our arrangement coincident e v e n t s recorded by a planar Ge and a SicLi) detector are recorded iboth energies and time separation) in list mode in a mu1 t i-channel analyzer memory and stored on disk. T h e various CLj values
T * d T
are determined during playback! with appropriate w i n d o w s defining Kal
,
Kap and KB.COINCIDENCE T h e X-ray sources used w e r e 195Au, RECORDER 203Hg. 204T.t a n d 207Bi. T h e first w a s
made by f 1 ash evaporation o n t o a Be Figure 1 . Schematic of experimental foil and the last by electroplating on
arrangement a Ni foil; the o t h e r s w e r e m a d e by allowing a solution droplet mixed with Catanac (American Cranamid Company antistatic agent) to dry on a Mylar foil. T h e s e techniques ensured uniform, very thin s o u r c e s which are essential to minimize L X-ray self-absorption, {auxiliary experiments with less carefully prepared s o u r c e s exhibited self-absorption losses of up to 10%). Attenuation of a focussed beam of 5.9 keU photons w a s found to be negl igible in each source, indicating negl igible self-absorption.
T h e absolute efficiency of the Si(Li) detector w a s measured a s a function of X-ray energy to about il.5:! accuracy using standard radionuclide s o u r c e s C41.
T h e crux of t h i s experiment is reliable discrimination between KaZ a n d Kal .gating e v e n t s in the Ge detector.
A
specially designed module C51 s t a b 1 1 lzed the K A D C on every signal received, while presenting only coincidence e v e n t s for storage. T h e low-energy tail of Kal f a l l s below66 68 70 72 74
Energy (keV)
Figure 2. Details of fit of lineshape model to the K X-ray spectrum of T&. T h e residuals are in units of one standard deviation.
( a s shown i n f i g u r e 2) a n d a d d s s p u r i o u s Kal c o i n c i d e n c e e v e n t s t o t h o s e Z f e c t e d b y t h e Ka g a t e : t h i s can c a u s e v e r y l a r g e e r r o r s i n f 2 3 . We t h e r e f o r e r e c o r d e d K X-ray Z i n g l e s s p e c t r a t o i n t r n s i t i e s o f 2 x 107 c o u n t s a n d l e a s t - s a u a r e s f i t t e d them t o
H e r e G i s t h e m a i n G a u s s i a n component. S a f l a t s h e l f on i t s l e f t , a n d t h e D's a r e l o n g a n d s h o r t - t e r m t a i l s w h i c h a r e G a u s s i a n - e x p o n e n t i a l c o n v o l u t e s 1 6 1 . T h i s e n t i r e peaK f u n c t i o n i s c o n v o l u t e d w i t h t h e i n t r i n s i c L o r e n t z i a n l i n e s h a p e L for each o f K~ , ~a a n d Ka3, a n d a l i n e a r b a c k g r o u n d i s 8 a d d e d . T y p ~ c a l l y , r e d u c e d c h i - s q u a r e d v i l u e s w e r e 1.0
-
1.1 p e r m i l l i o n Ka c o u n t s , a n d t h e agreement o f t h e v e r y weak Kag i n t e n s i t y w i t h t h e o r y C21 i n d i c a t e d t h a t t h e t a i l i n g was a c c u r a t e l y d e s c r i b e d .3. A u x i l i a r y M e a s u r e m e n t s
The v e r y w i d e s c a t t e r o f e x i s t i n o m e a s u r e d d a t a f o r w a n d W was m e n t i o n e d a b o v e . I t i s t h e r e f o r e i n c u m b e n t on i n y w o r k e r s who a d d t % t h i s g o d y o f d a t a t o adduce some p r o o f t h a t t h e i r r e s u l t s i m p r o v e t h e s i t u a t i o n r a t h e r t h a n j u s t p r o v i d i n g more p o i n t s t o be a v e r a g e d b y r e v i e w e r s .
We t h e r e f o r e - u s e d t h e same s y s t e m t o measure t h e Q u a n t i t y PflK b y y - r a y + X-ray c o i n c i d e n c e m e a s u r e m e n t s f o r f l a s h - e v a p o r a t e d s o u r c e s o f t h e t w o n u c l i d e s 54Mn and 6 s Z n . The o n l y change was t h e r e p l a c e m e n t o f t h e p l a n a r Ge d e t e c t o r b y a m o r e e f f i c i e n t c o a x i a l G e ( L i ) d e t e c t o r , The v a l u e s o f P WK ( w h i c h i s t h e K X- r a r y i e l d p e r d i s i n t e g r a t i o n i .e. t h e p r o d u c t o f K c a p f u r e p r o b a b i l i t y a n d K f l u o r e s c e n c e y i e l d ) a r e known [ 4 1 t o b e t t e r t h a n + i % . Our m e a s u r e m e n t s o f t h i s s u a n t i t r w o u l d r e v e a l any u n e x p e c t e d f a c t o r s c a u s i n g l o w e r e d d e t e c t i o n e f f i c i e n c y . The r a t i o s o f o u r r e s u l t s t o " b e s t l i t e r a t u r e v a l u e s " w e r e 0 . 9 9 3 t 0 . 0 1 4 r o 5aMn a n d 1.000+0.017 f o r 65Zn i n d i c a t i n g t h a t o u r a p p r o a c h t o measurement o f o v e r a l l c o i n c i d e n c e i n t e n s i t y i s f r e e o f s y s t e m a t i c o r e x o e r i m e n t a l e r r o r a t t h i s l e u e l .
4. R e s u l t s
T a b l e 1 compares o u r L - s h e l l r e s u l t s w i t h DHS p r e d i c t i o n s C l l , semi- e m p i r i c a l f i t t e d v a l u e s o f K r a u s e 131 a n d two o t h e r r e c e n t m e a s u r e m e n t s u s i n g r e s p e c t i v e l y a s y n c h r o t r o n r a d i a t i o n t e c h n i s u e 171 a n d a c o i n c i d e n c e t e c h n i q u e s i m i l a r t o t h e p r e s e n t one 1 8 1 . Our w a n d w3 v a l u e s a g r e e w i t h t h e o r y t o w i t h i n t h e t y p i c a l e r r o r (63! c o n f i d e n c e l e u e ? ) o f 2-TL9 w h i c h a r i s e s a b p u t e q u a l l y f r o m e f f i c i e n c y d e t e r m i n a t i o n a n d e x t r a c t i o n o f L X - r a y peaK i n t e n s i t i e s f r o m t h e c o i n c i d e n c e s p e c t r a . T h e y d o n o t f a v o u r t h e s e m i - e m p i r i c a l v a l u e s , w h i c h t e n d t o l i e above t h e o r y f o r w a n d b e l o w t h e o r y f o r 02. One i n t e r e s t i n g p o i n t w o r t h y o f n o t e i s t h a t t h e l& f l u o r e s c e n c e y i e l d v a l u e s f o r Pb p r o d u c e d b y a s i m i l a r e x p e r i m e n t [ 8 1 c o r r e s p o n d c l o s e l y t o t h e r e s u l t s we o b t a i n e d u s i n g a d r o p - d r i e d s o u r c e w h i c h p r o v e d t o h a v e s i g n i f i c a n t s e l f - a t t e n u a t i o n when e x a m i n e d i n t h e c o l l i m a t e d beam e x p e r i m e n t .
Our f 2 3 v a l u e s a r e s y s t e m a t i c a l l y s e v e r a l p e r c e n t b e l o w t h e t h e o r e t i c a l o r e d i c t i o n s a n d t e n d t o w a r d s a g r e e m e n t w i t h t h e s e m i - e m p i r i c a l u a l u e s ; however +he l a t t e r a r e b a s e d on d a t a w i t h a v e r y l a r g e s p r e a d a n d K r a u s e a d d u c e s 15-20%
u n c e r t a i n t y t o them. The p r e s e n t d a t a p r o v i d e a much s t r o n g e r i n d i c a t i o n of a r e a l d i s c r e p a n c y r e l a t i v e t o t h e o r y .
5. D i s c u s s i o n
The p r e s e n t r e s u l t s s u b s t a n t i a t e t h e DHS p r e d i c t i o n s o f L, a n d Lg S u b s h e l l f l u o r e s c e n c e y i e l d s i n t h e 2-80 r e g i o n . E x t e n s i o n o f t h i s c o n f i r m a t i o n t o l o w e r a n d h i g h e r Z i s m o s t d e s i r a b l e , a n d we have b o t h i n p r o g r e s s . F o r t h e f i r s t t i m e , s y s t e m a t i c b e h a v i o u r o f fp3 i s a p p a r e n t . a n d t h i s o b s e r v a t i o n i s s u p p o r t e d b y new s y n c h r o t r o n r a d i a t i o n w o r k C71. T h i s s y s t e m a t i c d i s c r e p a n c y w i t h t h e o r y ma? i n d i c a t e t h e d e g r e e o f e r r o r i n c u r r e d b y n e g l e c t o f e x c h a n g e , r e l a x a t i o n a n d c o n f i g u r a t i o n i n t e r a c t i o n i n t h e s i n g l e - p a r t i c l e c a l c u l a t i o n . A c c u r a t e
L1
C9-600 JOURNAL DE PHYSIQUE
Table 1
Measured and predicted L subshell yields -for atoms in the Z~8Q region
z
78
79
80
81
82
w
2 .33?.321 .3424.010
.363 .334 .401+.020°
.368 .347 .371+.00?
.380 .360 .391+.010
.392 .373 .366*.026 .398+.010
«3 .300 .306 .286+.007
.320 .320 . .3201.010
.320 .333 .312 + . 006
.330 .347 .322+.005
.340 .360 .302+.021 .340+.007
*23 .131 .124 .112+.004
.128 .122 .100+.009
.127 .120 .122+.001
.126 .118 .11?+.002
.122 .116 .130+.002 .115+.002
Reference
T m
SE [33 E <Present) T [13 SE [33 E [7]
T m
SE C33 E (Present)
ten
SE [3]
E (Present) T [13 SE [33 E [83 E (Present) . T denotes theory, E experiment and SE a semi-empirical fit to data.
D Here the experiment determines if the ratio (0,/CiUi hence M, is assumed from 13]
and ft)2 deduced. £
subshell data would be of value in pursuing these.
This work is supported by the Natural Sciences and Engineering Research Council of Canada.
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