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Atomic-scale visualization of inertial dynamics
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2005 (English)In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 308, no 5720, p. 392-395Article in journal (Refereed) Published
Abstract [en]

The motion of atoms on interatomic potential energy surfaces is fundamental to the dynamics of liquids and solids. An accelerator-based source of femtosecond x-ray pulses allowed us to follow directly atomic displacements on an optically modified energy landscape, leading eventually to the transition from crystalline solid to disordered liquid. We show that, to first order in time, the dynamics are inertial, and we place constraints on the shape and curvature of the transition-state potential energy surface. Our measurements point toward analogies between this nonequilibrium phase transition and the short-time dynamics intrinsic to equilibrium liquids.

Place, publisher, year, edition, pages
2005. Vol. 308, no 5720, p. 392-395
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:mau:diva-44536DOI: 10.1126/science.1107996ISI: 000228492000046PubMedID: 15831753OAI: oai:DiVA.org:mau-44536DiVA, id: diva2:1578283
Available from: 2021-07-06 Created: 2021-07-06 Last updated: 2021-07-06Bibliographically approved
In thesis
1. Time-resolved X-ray diffraction studies of phonons and phase transitions
Open this publication in new window or tab >>Time-resolved X-ray diffraction studies of phonons and phase transitions
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [sv]

Denna avhandling sammanfattar arbete där tidsupplöst röntgendiffraktion har använts för att undersöka kristallina material och studera dynamiken hos fononer och fasövergångar.Röntgendiffraktion är standardverktyget för stukturbestämning på en atomär skala. Det har använts länge och har framgångsrikt hjälp vetenskapsmän att bestämma strukturen hos en stor mängd material. Användningen av ultrasnabb tidsupplöst röntgendiffration är ett starkt växande område som fortfarande utvecklas.Akustiska impulser, eller koherenta akustiska fononer, har studerats med hjälp av optiska tekniker i åtminstonde två årtionden. Optiska pulser kan dock endast underöka en halvledares yta. Röntgen penetrerar djupare in i proven och kan följa fononer då de färdas in i proven.Realtidsstudier av fasövergångar har också utförts med hjälp av optiska metoder. Dessa mätningar är indirekta då de mäter ändringar i susceptibiliteten hos provet istället för atomernas positioner. Återigen kan tidsupplöst röntgendiffraktion ge en ny insyn i området genom att den gör en direkt mätning av de strukturella ändringarna.Den här avhandlingen fokuserar huvudsaklingen på experimentellt arbete där tidsupplöst röntgendiffraktion använts för att studera fononer eller prover som genomgår en fasövergång. En kort teoretisk bakgrund finns med, liksom en beskrivning av D611, ett synkrotronljusstrålrör för tidsupplöst röntgendiffraktion som utvecklats under arbetet med den här avhandlingen.

Abstract [en]

This thesis summarizes work in which time-resolved X-ray diffraction has been used to probe crystalline materials, thereby revealing the dynamics of phonons and phase transitions.X-ray diffraction is the standard tool in investigations of structure on the atomic scale. It has been used for a long time, and has successfully helped scientists to find the structure of a wide range of materials. The use of ultrafast time-resolved X-ray diffraction is a strongly emerging field which is still under development.Impulsive strain pulses, or coherent acoustic phonons, have been probed using optical techniques for at least two decades. Yet, optical pulses can only probe the surface of a semiconductor. X-rays penetrate deeper and can follow the phonons as they propagate into the sample.Real time studies of phase transitions have also been conducted using optical methods. These measurements are indirect in the sense that they probe the susceptibility change of the sample rather than the positions of the atoms. Again, time-resolved X-ray diffraction can give new insights into the field by probing the structural changes directly.This thesis focuses mainly on experimental work in which time-resolved X-ray diffraction has been used to probe phonons or samples undergoing phase transitions. A brief theoretical background will also be given, as well as a description of beamline D611 at MAX-lab, a synchrotron beamline for time-resolved X-ray diffraction measurements which has been developed during the work for this thesis.

Place, publisher, year, edition, pages
Department of Physics, Lund University, 2005
Series
Lund Reports on Atomic Physics, ISSN 0281-2762 ; 350
Keywords
X-ray diffraction, phonons, phase transitions
National Category
Physical Sciences
Identifiers
urn:nbn:se:mau:diva-7776 (URN)1843 (Local ID)91-628-6662-1 (ISBN)1843 (Archive number)1843 (OAI)
Note

Paper VII in dissertation as manuscript with title: "Transient metal-like heat conduction in a semiconductor"

Note: The papers are not included in the fulltext online

Available from: 2020-02-28 Created: 2020-02-28 Last updated: 2024-02-26Bibliographically approved

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