Solid state and nuclear results from Mössbauer studies with I[superscript 129]
Hafemeister, David Walter
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https://hdl.handle.net/2142/23949
Description
Title
Solid state and nuclear results from Mössbauer studies with I[superscript 129]
Author(s)
Hafemeister, David Walter
Issue Date
1964
Doctoral Committee Chair(s)
Frauenfelder, Hans
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Mossbauer effect
isomeric shifts
alkali iodides
solid states
Language
en
Abstract
"The MIio ssbauer effect of the 26.8 keY transition in I 129 has
been studied in a number of iodine compounds. The following results
have been obtained:
a) The isomeric shifts for the alkali iodides were found to be
linearly dependent on the number of 5p holes in the iodine ion. From
this dependency, a calibration of the isomeric shift scale in terms
. of the 5s-electron denSity was obtained. The sand p populations
inferred from these data are in sharp disagreement with those predicted
by the simple theory of electronegativity. An explanation for this
discrepancy is given.
b) From the calibration mentioned under a), a relative change of
nuclear radius ~/R = (R26 •8 - Rgnd)/Rgnd = 3 x 10-5 is computed.
c) The isomeric shifts for some iodates indicate that their 5s-electron
density is about 18% lA.rger than that of the iodides. This increase
is caused by the partial removal of 5p electrons from iodine in the
I-O bonds, which results in reduced screening of the 5s electrons.
The shift for potassium periodate implies that the 5s-electron density
is decreased by 33% compared to the iodate. This decrease is
attributed mainly to the sp hybridization of the I-O bonds in KI04•
The charge removed per 1-0 bond calculated from the isomeric shifts
of the iodates and periodate is 0.61 e.
d) The quadrupole splitting of K103 was used to determine the 1129
quadrupole ratio, Q26.8/Qgnd """" 1,23 ± 0.02. The asymmetry of the
iodate spectrum and the sign of quadrupole moment show that the sign
of the iodate field gradient is negative. The values of the quadrupole
coupling constant, eqQ, at 800K for K103 and NH4I03 are in agreement
with NMR results and eqQ127 = 1030 ± 20 Mc/sec for Ba(I03)2'
e) Using conventional time-to-pulse-height techniques, the mean life,
~ = 26.8 ± 1.5 nsec$ of the 26.8 keY state of 1129 has been determined.
This value corresponds to a retardation factor of 140 when compared to
the single particle Ml estimate. An extrapolation of the absorption
line width to zero thickness gives a value of 20 nsec for the mean life.
This should be considered as a lower limit because of the possibility
of solid state broadening.
f) Th€ recoilless fraction f was found to deviate from 0.26 by less
than 25% for all alkali iodides at 80oK."
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