HAL Id: jpa-00217072
https://hal.archives-ouvertes.fr/jpa-00217072
Submitted on 1 Jan 1977
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MÖSSBAUER SPECTROSCOPY OF SMALL GOLD
PARTICLES
M. Viegers, J. Trooster
To cite this version:
JOURNAL DE PHYSIQUE Colloque C2, suppldment au no 7 , Tome 38, Juillet 1977, page C2-161
MOSSBAUER SPECTROSCOPY OF SMALL GOLD PARTICLES
(I)M.
P. A. VIEGERS and J. M. TROOSTER
Department of Physical Chemistry, University of
Nijmegen, Toernooiveld, Nijmegen, The Netherlands
Abstract.
-
The intensity of Mossbauer absorption lines is proportional tofa = exp(- ( x 2 )/A2), where ( x 2 ) is the mean squared vibrational amplitude of the absorbing
atoms and 2 ?rA = A is the wavelength of the absorbed radiation. Intensity measurements of the Mossbauer effect in small particles can thus give information on changes in the phonon spectrum. A short review will be given of earlier work, which shows conflicting results. In this report results will be given of measurements on nine samples of small gold particles suspended in frozen gelatin. Average sample diameters range from 30
A
to 170A.
The intensity of the Mossbauer absorption of the 77 keV transition of I g 7 ~ u was measured as function of temperature between 4.2 K and 60 K. It is found that the Mossbauer fraction fa (and therefore( x 2 ) ) at the lowest temperature does not deviate considerably from the value of bulk gold.
However, with increasing temperature fa decreases more rapidly than in bulk, with strongest decrease for the smallest particle size. The various models for the phonon spectrum which were used to calculate the temperature dependence of fa will be discussed, but it appears that to explain the observed f,(T) it is necessary to take account of the vibrational amplitude of the particle as a whole. The implications for the study of small particles by means of the Mossbauer effect will be discussed.
('1 Published in Phys. Rev. B 15 (1977) 72.
