THE TRANSMISSION INTEGRAL AND DETERMINING THE ABSOLUTE MÖSSBAUER FRACTION

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THE TRANSMISSION INTEGRAL AND

DETERMINING THE ABSOLUTE MÖSSBAUER FRACTION

V. Belogurov, V. Bilinkin

To cite this version:

V. Belogurov, V. Bilinkin. THE TRANSMISSION INTEGRAL AND DETERMINING THE ABSO- LUTE MÖSSBAUER FRACTION. Journal de Physique Colloques, 1980, 41 (C1), pp.C1-109-C1-110.

�10.1051/jphyscol:1980119�. �jpa-00219679�

JOURNAL DE PHYSIQUE Colloque C1, supplkment au n

"

1 , Tome 41, janvier 1980, page C1-109

M E TRANSMISSION INTEGRAL AND DETERMINING M E ABSOLUTE N~SSBAUER FRACTION

V.N. Belogurov and V.A. Bilinkin

Physics I n s t i t u t e , L a t v i a n SSR Academy of S c i e n c e s , 229021 Riga, SaZaspiZs

-

2, USSR.

The probability of recoiless gamma-quanta integral intensities (normalized t o unit total inten- emission o r absorption ( f ) is one of the most im- s i t i e s ) and positions of the i-th line; 1

-

the number portant parameters when studying the Mossbauer of lines; T = 6 nf

-

the effective thickness;

-

o a o

effect. The absolute value of the effect depends on t h e maximum absorption cross-section a t resonan- t h e dynamics of crystal atoms containing the Moss-

bauer nuclei, and by measuring f w e get valuable information on t h e vibrational spectrum of the crys- t a l and on interatomic interaction for host and im- purity atoms of the lattice, a s well a s on the change of atom characteristics depending on temperature, p r e s s u r e , radiation, and a t phase transitions.

Different techniques known up to now a r e , in fact, applicable only for the c a s e s of single line o r well-resolved spectra.

According t o the technique suggested in the present paper t h e spectrum is approximated by the curve obtained by computing the transmission integ- r a l for a concrete spectrum, which allows to take a c o r r e c t account of badly-resolved and non-resolved

where N(E ) is the number of gamma-quanta re- v

gistered a t the Doppler shift velocity V ; E

-

the v Doppler shift energy; Q = B

+

S

-

the number of gamma-quanta registered a t infinite velocity; S

-

t h e number of gamma-quanta with the energy of the Mossbauer transition; B

-

the number of gamma- quanta with other energies;

d=fs.~=fis/Q -

t h e fraction of resonance gamma-quanta after a n ab- dorber; fs

-

resonance gamma-quanta emission probability;

5.G' ^-

the half-widths of the

\

emission and absorption lines and the n h a l half- width of the line, respectively; i and a i

-

the

c e nuclear density in the absorber; f

-

the proba- a

bility of the effect in t h e absorber.

The

d;

-parameter has been measured inde- pendently, since its variations reduce strongly the accuracy of the f determination1. The values of

a

f have been measured by means of the two reso-

2 3

nant absorber technique using "black" absorbers

.

The values of p have been measured by t h e techni- que, similar to the standard one 4

,

using cupric f i l t e r s

.

The technique has been tested for polycrystal- 1 ine samples of sodium nitroprusside and yttrium- i ron garnet ( Y IG )

.

NGR spectra m e a s u r e p e n t s providing good statistical accuracy (not less than 10 imp/channel) have been done using t h e spectro- 6 meter of constant acceleration with the velocity sta- bility not worse than 0.004 mm/s5 in the tempera- t u r e interval from 78 to 427K for sodium nitroprus- side and a t 590K for YIG.

By measuring several spectra of one sample using aluminium f i l t e r s of different thickness 6

(Table 1) and spectra of several samples with dif- ferent density (Table 21, both for the c a s e of sodi- um. nitroprusside a t room temperature, the limit of accuracy for determining the f-values has been found t o be f = 0.468+0.007 for the first c a s e , and f = 0.47+0.01 for t h e second case.

E r r o r s of the constants used when calculating t h e values of f , i. e. several inaccuracies in abso- lute values of velocity scale and absorber a r e a , ca- u s e the e r r o r of the absolute values of f (+0.035) exceeding the fidelity of the r e s u l t s ( s . 0 1 ) .

NGR spectra have been measured and spectra

Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1980119

c1-110 JOURNAL DE PHYSIQUE

parameters have been calculated a t different tempe- ratures. The r e s u l t s a r e listed in Table 3. The jump i n the magnitude of

A ^,

a s well a s the changes in t e m p e r a t u r e dependence of the f-value appear due t o

sodium nitroprusside dehydration 7

.

Table 1. The values of

& ,

f and

r

f o r sodi-

S

um nitroprusside measured using filters of different thickness a t T = 291 K.

No.

&

f E ( m m / s ) 1 0.506 0.466 0.116 2 0.459 0.476 0.118 3 0.430 0.475 0.118 4 0.369 0.461 0.120 5 0.304 0.461 0.124

Table 2. The values of

& ,

f and for so- dium nitroprusside with different density measured a t T = 291K.

Table 3. The values of isomer shift

8

( v e r s u s t h e

8

-values a t T = 2 9 1 ~ ) , q u a d r u p l e splitting

A ,

and f measured a t different temperatures. Maximum deviation from the values of

8

^{' and averaged}

over several measurements is s.00 1.

No. t ( ~ ) R(rnm/s) A(rnm/s) f 1 78 +0.066 1.713 0.895

2 291 0 1.710 0.470

3 339 -0.025 1.706 0-432 4 384 -0.055 1.929 0-324 5 427 -0.082 '1.926 0.269

Thrice-repeated measurements of NGR in YIG

t h a t for sodium nitroprusside, i. e. f = 0.558 2 0.006 for the b m =+I line and f = 0.525+0.009 f o r the A m = 0 line. Above-mentioned reasons account also for the e r r o r increase (up to s.035) when determining f. Calculations have shown the equality of the effect values in octa- and tetrasub- 1 attices of YIG

.

I n conclusion, we can say that t h e suggested technique allows to deterrriine the absolute value of f in badly- o r unresolved NGR spectra of absorb- ers with a r b i t r a r y thickness.

References

1 Belogurov, V . , Bilinkin, V.

,

Prepr.lnst.Fiz.

Akad.Nauk LSSR, Salaspils

,

1978.

2 Johnson, D.P.

,

Nucl.Instr. and Meth.

, 3

( 1970129.

3 Housley, R.M., Ericson, N:E., Dash, J.G.

Nucl.Instr. and Meth.

g(

1964)29.

4 Housley, R.M.

,

Nucl.Instr. and Meth., 35 (1965177.

5 Belogurov, V., Bilinkin, V., Prepr-Inst-Fiz.

Akad. Nauk LSSR

,

Zinatne

,

Riga, 1977.

6 Asylbaev, V.H., Orasbaev, T.A., Prikl. i Teor.Fiz., 2(1977) 158.

7 Boughton, C .A. et al.

,

J.Inorg.Nuc1. Chem.

,

38( 1976) 427.

-

( a t 590K its spectra is unresolved) using f i l t e r s of different thickness gave the fidelity values, close to