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MÖSSBAUER SPECTROSCOPY WITH ELECTRONS BELOW 10 eV
T. Tyliszczak, J. Sawicki, J. Stanek, B. Sawicka
To cite this version:
T. Tyliszczak, J. Sawicki, J. Stanek, B. Sawicka. MÖSSBAUER SPECTROSCOPY WITH ELECTRONS BELOW 10 eV. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-117-C1-118.
�10.1051/jphyscol:1980123�. �jpa-00219691�
JOURNAL DE PHYSIQUE CoNoque Cl , suppl&nent au n " 1, Tome 41, janvier 1980, page C1-117
P@SSBAUER SPECTROSCOPY WITH ELECTRONS BELOW 10 eV
T. Tyliszczak, J.A. Sawicki, J. Stanek and B.D. Sawicka
+ *
I n s t i t u t e of Physics, JagieZZonian University, Cracow
+ I n s t i t u t e o f Physics, Technical University, Cracow
+
I n s t i t u t e of Nuclear Physics, Cracow, Poland.Conversion electron Missbauer spectra are usually measured by detecting conver- sion and Auger electrons at an energy high- er than about 1 keV. In this work an at- tempt was made to investigate the resonant electrons of 57~e at an energy as low as 1
-
10 eV. An especially strong yield of electrons was observed at an energy of 1-
2 eV, which is analogous to the X-ray photoemission spectra of the valence elec- trons of iron '/. To our knowledge the resonant reemission of electrons at such a low energy as yet has neither been obser- ved experimentally nor considered theore- tically 2,3/.TO PUMP
r-
Fig. 1. Low-ener@;y electron spectrometer with retarding grids
A modular electron spectrometer was constructed. The scheme of the spectrome- ter with the retarding/accelerating grids module is shown in Fig. 1. Electrons from the sample after passing the grids were accelerated and detected using a channel-
tronx/. The grids were made of 40 urn mesh tungsten wire 1 mm apart. A +200 V poten- tial was applied to entrance of the channel- tron. Experiments were performed with enriched metallic iron and stainless steel foils as well as with silicon samples im- planted with 5 . 1 0 ~ ~ at. 57~e/cm2 at the energy of
70
keV. The source was 100 mCi 57co,,.The,technique of measurement of low energy electron spectra was developed.
The spectra can be taken readily in a mul- tiscaler mode by applying a triangle wave- form sweeping signal to the pair of retar- ding grids. The signal from the Mossbauer function generator /10 Hz, 20 V / was used.
PP
It was found that the count rate strong- ly increases at the resonant velocity /vo/
and varies with the retarding voltage.
The differentiation of the count-integrated curves reveals an electron peak at an ener- gy of approximately 1.5 eV in stainless- steel /Fig. 2/. Similar measurements were performed with a metallic iron foil and an 5 7 ~ e : ~ i implanted sample. The position and shape of the peak depended on the specimen used. A good agreement between the position of a peak observed here and the X-ray photoemission spectra of iron at very low energy is remarkable.
Rossbauer spectra obtajned with the inclusion of very low energy electrons showed a marked line broadening /Fig.
3/.
For instance, for a metallic iron one has approximately a line-width W = 0.41, 0.32 and 0.25 mm/s for a retarding potential equal to 0, 10 and 100 V, respectively.
The broadening decreases with increasing
Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980123
c1-118 JOURNAL DE PHYSIQUE
r e t e r d i n g p o t e n t i a l , t h a t i s with t h e decr- ease i n t h e contribution of very low energy electrons i n t h e spectrum, The reason f o r t h i s e f f e c t i s not c l e a r a s y e t , but one can suppose t h a t t h e broadening can be a t l e a s t p a r t l y associated with t h e surface e f f e c t s , f o r instance, t h e change of t h e hyperfine i n t e r a c t i o n s f o r t h e close-to-surface atoms /see r e f . 4/.
ENERGY lev1
Fig. 2, The low-energy e l e c t r o n s p e c t r a of s t a i n l e s s s t e e l obtained a t resonance v e l o c i t y /vo/ and far-off
resonance /vm/.
It can be suggested t h a t i n view of t h e i r very low p e n e t r a b i l i t y t h e very low energy electrons may be e s p e c i a l l y use- f u l i n s t u d i e s of surface magnetism a s well a s other p r o p e r t i e s of s o l i d surfaces.
The s p e c t r a of low-energy electrons and the corresponding Nassbauer s p e c t r a a r e stu- died now i n more d e t a i l s with a c y l i n d r i c a l mirror analyzer module, The possible connec- t i o n s between MSssbauer spectroscopy, X-ray photoemission spectroscopy, Auger e l e c t r o n spectroscopy, low-energy e l e c t r o n d i f f r a c - t i o n and ESCA a r e a l s o investigated.
METALLIC IRON
1001 ,
. .
0 100 200 300 400 500
CHANNELS
Fig. 3. Electron WSssbauer s p e c t r a of m e t a l l i c i r o n f o i l f o r a zero
r e t a r d i n g p o t e n t i a l ,
x/ The authors a r e obliged t o D r . 0. Gzowski from the Technical University of Gdahsk who produced a highly r e l i a b l e channeltron and made it a v a i l a b l e f o r our experiments.
Ref erenpes
1/ S.S. Hiifner, G.K. Wertheim, Phys. L e t t e r s 4 7 4 349 /1974/,
--
2/ T. Toriyama, K. Saneyoshi, K. Hisatake,
J. Phys. Collq. C2 40, 14 /l979/,
3/ R.A. Krakowski, R.B. Miiller, l u c l , I n s t r . Methods*
loo,
293 /1972/,4/ S.W. Duncan, R,J. Semper, A,H. Ovens, J.C. Walker, t h i s Conference.
