Nuclear Forward-Scattering of Synchrotron Radiation From Krypton: First Observation and Application to the Study of Lattice Dynamics in Near-Monolayer Krypton-on-Graphite

<p>Since 1985 nuclear-resonant scattering, and in particular nuclear forward-scattering, of synchrotron radiation has been observed in a select few Mossbauer isotopes including: ⁵⁷Fe, ¹¹⁹Sn, ¹⁶⁹Tm. For the first time, nuclear forward-scattering from the 9.4 keV Mossbauer level in ⁸³Kr has been observed. A large resonance effect, comparable to that in ⁵⁷Fe, has been observed in a variety of systems containing Kr including bulk crystals and physisorbed Kr-on-exfoliated graphite. Previous nuclear-resonant scattering experiments using synchrotron radiation have consisted of demonstration experiments. Nuclear forward-scattering from Kr has been applied to study the lattice dynamics of near-monolayer Kr-on-graphite by measurement of the probability for recoil-free scattering, i.e., Lamb-Mossbauer factor, (f_LM) as a function of both relative coverage on the substrate and sample temperature. This represents the first practical application of the nuclear forward-scattering technique to a previously unsolved physical problem.</p> <p>It was found that f_LM of the physisorbed Kr displays a coverage-dependent behavior, indicating a change of the in-plane f_LM due to neighbor-neighbor interactions in the layer. At low coverages, the slope of f_LM with temperature is reminiscent of anharmonic behavior in the bulk, while at near-monolayer coverages, the slope of f_LM with temperature is like a harmonic 3-D solid. A measurement of f_Lm at low temperatures through the commensurate-incommensurate transition of Kr-on-graphite shows a dramatic decrease and slow recovery in the transition region. This behavior is shown to be consistent with a simple calculation of the interaction energy of the incommensurate layer.</p> <p>The nuclear forward-scattering technique is shown to be a powerful tool, complementary to conventional x-ray diffraction measurements, as the time-resolved resonant scattering is free from any non-resonant graphite background and independent of the static structure of the system.</p>

Name thesis:degree_name

Doctor of Philosophy (PhD)

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Physics

Year dc:date.available

1995

Author dc:creator

• Johnson, David Eric

Contributors dc:contributor

• Gilbert R. Hoy
• John Adam
• Mark Havey
• Gary E. Copeland
• Desmond Cook

• Graphite
• Forward scattering
• Krypton
• Condensed Matter Physics

Statement dc:rights

• <p>In Copyright. URI: <a href="http://rightsstatements.org/vocab/InC/1.0/">http://rightsstatements.org/vocab/InC/1.0/</a> This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).</p>

Repository record dc:identifier

https://digitalcommons.odu.edu/physics_etds/61

OAI identifier oai:identifier

oai:digitalcommons.odu.edu:physics_etds-1053