HAL Id: jpa-00227298
https://hal.archives-ouvertes.fr/jpa-00227298
Submitted on 1 Jan 1987
HAL is a multi-disciplinary open access archive for the deposit and dissemination of sci- entific research documents, whether they are pub- lished or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers.
L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
DETERMINATION OF CORE HOLE LIFETIMES USING X-RAY PHOTOELECTRON
SPECTROSCOPY : APPLICATION AND USE OF DECONVOLUTION PROCEDURES
I. Cserny, L. Kövér, J. Tóth, M. Fi Er
To cite this version:
I. Cserny, L. Kövér, J. Tóth, M. Fi Er. DETERMINATION OF CORE HOLE LIFETIMES US- ING X-RAY PHOTOELECTRON SPECTROSCOPY : APPLICATION AND USE OF DECON- VOLUTION PROCEDURES. Journal de Physique Colloques, 1987, 48 (C9), pp.C9-1017-C9-1020.
�10.1051/jphyscol:19879182�. �jpa-00227298�
DETERMINATION OF CORE HOLE LIFETIMES USING X-RAY PHOTOELECTRON SPECTROSCOPY
:APPLICATION AND USE OF DECONVOLUTION PROCEDURES
I. CSERNY, L. K O V ~ R , J. T ~ T H and M. F I ~ E R *
Institute of Nuclear Research of the Hungarian Academy of Sciences, PO Box 51, H-4001 Debrecen, Hungary
" ~ u c l e a r Physics Institute of the Czechoslovak Academy of Sciences, 25068 Rez, Near Prague, Czechoslovakia
A b s t r a c t : M o d i f i c a t i o n o f a s e l f - d e c o n v o l u t i o n procedure (adopted f r o m R e f . [33) and i t s a p p l i c a t i o n f o r t h e d e t e r m i n a t i o n o f c o r e - h o l e l i f e t i m e s o f Tc metal 34 l e v e l s , u s i n g X-ray p h o t o e l e c t r o n spectroscopy, a r e presented.
In a previous paper ~ B r t e n s s o n and Nyholm [il have o b s e r v e d t h e existence o f an MqMgN4,5 Coster-Kronig (CK) decay channel t h r o u g h t h e broadening ( r C K ) o f t h e 36312 c o r e level o f metals Nb-Rh (2.41-451, with t h e exception o f Tc ( n o t examined). The CK-broadening o f t h e Tc 3d312 c o r e level was observed by Kov6r e t al. [2].
The d e t e r m i n a t i o n o f t h e l i f e t i m e broadening c o n t r i b u t i o n t o t h e p h o t o e l e c t r o n line width r e l i e s on t h e assumption t h a t t h e line shapes o f t h e two spin-orbit components (34312
,
34512) a r e t h e same, except f o r a possible d i f f e r e n c e in t h e lifetime broadening due t o t h e Coster-Kronig decay. Since t h e f i n i t e lifetime gives a Lorentzian contribution t o t h e line shape, t h e p a r t i a l l y overlapping spin-orbit components can be compared using t h e s e l f - deconvolution procedure suggested by Nyholm and ~ Z r t e n s s o n [3]:S t a r t i n g f r o m t h e low-binding-energy p a r t o f t h e spectrum (where t h e 3d512 line vanishes) t h e f o l d e d (using a Lorentzian broadening function) and s h i f t e d (by t h e ESO s p i n - o r b i t s p l i t t i n g ) r e p l i c a o f t h e 3dSl2 line i s s u b t r a c t e d successively. The 34512 t o 36312 intensity r a t i o also has t o be taKen i n t o account. The p a r a m e t e r s o f t h e procedure a r e all varied until t h e r e s u l t i n g 3dg12 single-line p r o f i l e g e t s a line shape considered "physically reasonable* visually. This procedure however, has a subjective c h a r a c t e r , So t h e accuracy o f t h e method is undetermined.
In t h i s paper, a modification o f t h e s e l f deconvolution procedure i s presented: instead o f t h e visual inspection o f t h e 3d512 line profile, t h e
"oscillations1* o f t h e line t a i l around a smooth curve (which was f i t t e d t o t h e d a t a points in each i t e r a t i o n c y c l e b y l e a s t - s q u a r e s method) was minimized. I t t u r n e d out, t h a t t h e physically m o s t reasonable line shape gives t h e least chi-square value, so t h e deconvolution p r o c e d u r e can be automated obtaining htgher accuracy.
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19879182
C9-1018
JOURNALDE
PHYSIQUE264 260 256 252 248
Binding energy
(eV)
F i g . 1 The measured Tc 36 core l e v e l spectrum w i t h t h e deconvoluted 34512 s i n g l e - l i n e p r o f i l e ( s o l i d l i n e ) and t h e f i t t e d y=a/xb curve (dashed 1 ine)
.
Using t h i s method, a Coster-Kronig broadening o f rC~=(0.39f0.05) eV o f t h e Tc 3d3/2 p h o t o e l e c t r o n line has been found in t h e case o f metallic Tc.
Fig. 1 shows t h e r e s u l t i n g single-line p r o f i l e and t h e f i t t e d y=a/xb function. We found, t h a t Es0=3.65 eV gives t h e most reasonable lineshape. The 3d5/2 t o 3d3/2 intensity r a t i o o f 1.45 was taken f r o m Ref.[41. The details o f t h e source preparation and experimental w i l l be published elsewhere.
The sensitivity o f t h e self-deconvolution procedure is demonstrated on Fig. 2, where single-line p r o f i l e s a r e p r e s e n t e d using d i f f e r e n t
rCK
parameter values.
Since our measurements were carried out using non-monochromatized X-ray excitation, f o r improving t h e r e s o l u t i o n we s u b t r a c t e d t h e broadening contribution o f t h e Al K, source using an i t e r a t i v e deconvolution method [5].
The necessary parameters o f t h e A l K, spectrum were t a k e n f r o m Ref.161.
Altough t h i s deconvolution procedure amplifies t h e s t a t i s t i c a l f l u c t u a t i o n s , it f a c i l i t a t e s t h e evaluation o f t h e s p e c t r a t h r o u g h t h e r e s o l u t i o n enhancement. It has been found, t h a t b o t h o f t h e raw d a t a and t h e deconvoluted data give nearly t h e same r e s u l t (see Fig.l and Fig.3). This agreement can be regarded as a p r o o f o f t h e "goodness" o f t h e deconvolution procedure, and a t t h e same time it provides an evidence f o r t h e justification of application o f t h i s resolution enhancement procedure in determination Of
c o r e hole lifetimes.
Binding energy (eV)
Fig. 2 The T c 3 4 spectrum after X-ray broadening removal, with different 34512 single-line profiles using various ~ C K parameter values.
Fig. 3 The T c 3d-spectrum after A1
Ka
broadening removal, with the deconvoluted 3d512 line profile (solid line) and the fitted y=a/xb curve (dashed 1 i ne).
C9-1020 JOURNAL DE PHYSIQUE
To determine t h e absolute c o r e level width 111 o f t h e Tc 3d5/2 line t h e Tc M4,5N4,5N4,5 Auger s p e c t r a were measured by XAES. The background was removed in two steps: f i r s t a linear background t h e n a conventional Shirley background [7] were subtracted.
T h e Tc M5N4,5N4,5/M4N4,5N4,5 Auger i n t e n s i t y r a t i o (\A) has been determined by least-squares f i t t i n g using skewed Gaussian [81 line shapes.
The shape o f t h e line (FWHM, asymmetry parameter) was reproduced by using t h e s e l f - c o n v o l u t i o n [9] o f t h e valence band p h o t o e l e c t r o n s p e c t r u m ( t h e broadening contribution o f t h e non-monochromatized excitation source had been removed b y deconvolution). Due t o t h e low peak-to-background r a t i o s we have g o t t h r e e d i f f e r e n t values (IA=6.62, 9.44 and 9.19) f r o m t h r e e independent experiments. The mean value o f 8.4 was used
,
and t h e estimated e r r o r o f about 40% was supposed.The absolute c o r e level width o f t h e 3d512 line i s expressed by [1]:
5 ~ C K
rA
=---
which g i v e s r A = ( 0 . 1 4 f 0 . 1 0 ) eV.2 1 A - 3
T h i s v a l u e agrees w e l l w ~ t h t h e tendency o f experimental r e s u l t s o b t a i n e d e a r l i e r [I] i n t h e 2 ~ 4 1 - 4 5 r e g i o n .
References
[I] N. Martensson, R . Nyholm, ~ h y s . Rev.
4
~ 0 . 1 2 (1981) 7121 123 L. KovCr,J. T 6 t h , l . Cserny,M. F i g e r , ATOMKI Annual Rep. 1986, 40 [3] N. Martensson,R. Nyholm, Chem. Phys. L e t t . 74 (1980) 337C4] H. S c o f i e l d , J. E l e c t r o n Spectrosc.
3
(1976) 129[5] A. F. C a r l e y , R.W. Joyner, J. E l e c t r o n Spectrosc.,
16
(1979) 1 [6] N. Beatham, A.F. Orchard, J. E l e c t r o n Spectrosc.,2
(1976) 129 173 D. A. S h i r l e y , Phys. Rev. B,5
(1972) 4709[8] R. D. B. F r a s e r , E. Suzuki
