CORRELATION OF THE MÖSSBAUER ISOMER SHIFT WITH THE X-RAY CHEMICAL SHIFT FOR Au IN Cu3Au

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CORRELATION OF THE MÖSSBAUER ISOMER SHIFT WITH THE X-RAY CHEMICAL SHIFT FOR

Au IN Cu3Au

L. Roberts, W. Josephson, D. Knoble

To cite this version:

L. Roberts, W. Josephson, D. Knoble. CORRELATION OF THE MÖSSBAUER ISOMER SHIFT WITH THE X-RAY CHEMICAL SHIFT FOR Au IN Cu3Au. Journal de Physique Colloques, 1974, 35 (C6), pp.C6-225-C6-225. �10.1051/jphyscol:1974627�. �jpa-00215784�

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JOURNAL DE PHYSIQUE Colloque C6, supplkment au no 12, Tome 35, Dicembre 1974, page C6-225

CORRELATION OF THE MOSSBAUER ISOMER SHIFT WITH THE X-RAY CHEMICAL SHIFT FOR Au IN Cu3Au

(*)

L. D. ROBERTS, W. D. JOSEPHSON and D. W. KNOBLE University of North Carolina, Chapel Hill, N. C. 27514, U. S. A.

RBsumB. - Le deplacement isombique Mossbauer et le deplacement chimique de rayons X ont ete mesures pour 197Au dans CusAu par rapport a l'or metallique. Ces donnees sont cornparks l'aide d'une thkorie appropriee. Les rksultats sont en accord avec le signe et approximativement avec la grandeur de Ar/r du noyau 197Au obtenus antkiieurement.

Abstract. - The Mossbauer isomer shift and the X-ray chemical shift have been measured for 197Au in CusAu relative to metallic gold. These are compared through appropriate theory. The results agree with the sign and approximately with the value for Arlr for the 197Au nucleus which was obtained earlier.

In the interpretation of a measured Mossbauer isomer shift, AEM, calculations of

I

^$(0)

IZ

are made, and these

I

⁺⁽⁰⁾

1'

are used to obtain a value for the nuclear parameter, ArJr. The greatest uncertainty in this pro- cedure is in the calculated values of

I

^$(0)

1'.

^{Thus we}

have sought to make an experimental and theoretical study which would give independent information about

(

$(0)

1'

and which would be relevant to AEM measurements. For this purpose we have made parallel studies of BEM and of the X-ray chemical shift, AE,, for Au alloys.

In first approximation, there is much similarity between AE, and AEM. This may be seen in eq. (1)

Here, $'(r) and $(r) are the Au valence band electron wave functions for Au in an alloy and for pure gold.

If

AE

of eq. (1) is to describe the Mossbauer isomer shift, AEM, Vi(r) and Vj(r) are the Coulomb potentials for the excited and ground states of the 1 9 7 A ~ nucleus.

If AE is to describe the X-ray chemical shift, AE,, V,(r) and Vj(r) will be the atomic single electron Coulomb potentials for an L shell and for the K shell of Au. Here the L + K transition gives the X-ray to be studied.

Since the atomic Dirac-Hartree-Fock-S1ater wave function program used in the calculation of $'(r) and of

$(r) also gives the atomic K and L shell potentials as results of the same wave function calculation, the information for a calculation of AE, from eq. (1) is available.

The essential point to be noted is that the same valence electron factor

(I

$'(r)

1'

-

I

$(r)

1')

enters in both AEM and AEx in eq. (1). A given calculation of this factor may thus be compared with AEM and BEx measurements on the same alloy.

We have previously calculated this valence electron factor [l] for Au alloyed in Cu, Ag, Pd and Pt and have used this result to interpret our AEM measurements for these alloys. From this alloy treatment [l] we obtained Arlr = 1.5 x lo-" in good agreement with several other studies [2,3,4].

We have now measured AE, for Au in Cu3Au rela- tive to Au for the gold K,, X-ray line. We find AEx = - 0.036

+

0.006 volt. The gold K,, X-ray from the alloy has a lower energy than from pure gold.

This experimental result may be compared with a value for AEx = - 0.050 volt calculated from eq. (1). In this calculation the same valence electron factor was used which we had used in our earlier interpretation of AE, measurements for ^"'AU alloys [I]. Thus the present AEx study confirms the sign and, approximately, the magnitude of the Ar/r values for 19'Au given earlier [l, 2, 3, 41.

References

[I] ROBERTS, L. D., BECKER, R. L., OBENSHAIN, F. E. and [3] BARTUNIK, H. D., POTZEL, ^W., MOSSBAUER, R. L. and THOMSON, ^J.O., Phys. Rev. 137A (1965) 895. KAINDL, G., 2. Phys. 240 (1970) 1-16.

[2] ROBERTS, L. D., PATTERSON, D. O., THOMSON, J. 0. and [4] KAINDL, G., LEARY, K. and BARTLETT, N., J. Chem. Phys.

LEVEY, R. P., Phys. Rev. 179 (1969) 656. 59 (1973) 5050.

(*) Work supported by the National Science Foundation under Grant No. ^36874Xat the University of North Carolina and by the Materials Research Center at the University of North Carolina under Grant No. GH-33632 from the National Science Foundation.

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Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:1974627