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Ultrafast electron diffraction from a Bi(111) surface: Impulsive lattice excitation and Debye–Waller analysis at large momentum transfer.
- Source :
- Structural Dynamics; 2019, Vol. 6 Issue 3, pN.PAG-N.PAG, 9p
- Publication Year :
- 2019
-
Abstract
- The lattice response of a Bi(111) surface upon impulsive femtosecond laser excitation is studied with time-resolved reflection high-energy electron diffraction. We employ a Debye–Waller analysis at large momentum transfer of 9.3 Å<superscript>−1</superscript> ≤ Δ k ≤ 21.8 Å<superscript>−1</superscript> in order to study the lattice excitation dynamics of the Bi surface under conditions of weak optical excitation up to 2 mJ/cm<superscript>2</superscript> incident pump fluence. The observed time constants τ<subscript>int</subscript> of decay of diffraction spot intensity depend on the momentum transfer Δk and range from 5 to 12 ps. This large variation of τ<subscript>int</subscript> is caused by the nonlinearity of the exponential function in the Debye–Waller factor and has to be taken into account for an intensity drop ΔI > 0.2. An analysis of more than 20 diffraction spots with a large variation in Δk gave a consistent value for the time constant τ<subscript>T</subscript> of vibrational excitation of the surface lattice of 12 ± 1 ps independent on the excitation density. We found no evidence for a deviation from an isotropic Debye–Waller effect and conclude that the primary laser excitation leads to thermal lattice excitation, i.e., heating of the Bi surface. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 23297778
- Volume :
- 6
- Issue :
- 3
- Database :
- Complementary Index
- Journal :
- Structural Dynamics
- Publication Type :
- Academic Journal
- Accession number :
- 137252952
- Full Text :
- https://doi.org/10.1063/1.5093637