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Solid state and nuclear results from Mössbauer studies with I[superscript 129]

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Title: Solid state and nuclear results from Mössbauer studies with I[superscript 129]
Author(s): Hafemeister, David Walter
Doctoral Committee Chair(s): Frauenfelder, H.
Department / Program: Physics
Discipline: Physics
Degree: Ph.D.
Genre: Dissertation
Subject(s): Mossbauer effect isomeric shifts alkali iodides solid states
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.
Issue Date: 1964
Genre: Dissertation / Thesis
Type: Text
Language: English
URI: http://hdl.handle.net/2142/23949
Rights Information: 1964 David Walter Hafemeister
Date Available in IDEALS: 2011-05-18
Identifier in Online Catalog: 6138646
 

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