The Mossbauer effect of FE57 on the surface of tungsten
Burton, John Williams
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https://hdl.handle.net/2142/23965
Description
Title
The Mossbauer effect of FE57 on the surface of tungsten
Author(s)
Burton, John Williams
Issue Date
1965
Doctoral Committee Chair(s)
Frauenfelder, Hans
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Mossbauer effect
iron
tungsten
polycrystalline tungsten
energy shifts
quadrupole splitting
Language
en
Abstract
The Mossbuaer effect of Fe 57 on the surface of polycrystalline tungsten
has been measured over a temperature range of 80 - 5000 K, and at angles of
0° and 60° with respect to the normal. The M8ssbauer spectra consist of
three unresolved lines, the middle one agreeing with measured spectra of Fe
57
in the bulk of tungsten, and the outer two being attributed to surface effects.
The assymmetry of the surface spectra, the angular dependence of the shape,
and the magnitude of the splitting of the two surface lines indicate an electric
field gradient at the surface of 2.4 x 10
16
V/cm
2
directed along the
normal. An effective Debye temperature of 406 + l2°K is found for the bulk,
from a study of the temperature dependence of the intensity of the M8ssbauer
absorption. The effective Debye temperature for the surface is 354 + 300K
along the normal, and 255 + 300K parallel to the surface. The angular dependence
of the total intensity of the two surface lines agrees with a simple
theory for an atom bound above the top layer of the host lattice. The isomer
shift with respect to iron at 300 0K is .0151 + .0002 cm/sec in the bulk, and
,018 ± .002 cm/sec on the surface. The temperature dependence of the shift
was not determined with sufficient accuracy to detect any surface effects on
the .second order Doppler shift. Experimental apparatus and computer programs
are described.
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