Ultrafast core-loss spectroscopy in four-dimensional electron microscopy

Renske M van der Veen; Thomas J Penfold; Ahmed H Zewail

doi:10.1063/1.4916897

Ultrafast core-loss spectroscopy in four-dimensional electron microscopy

Struct Dyn. 2015 Apr 28;2(2):024302. doi: 10.1063/1.4916897. eCollection 2015 Mar.

Authors

Renske M van der Veen, Thomas J Penfold¹, Ahmed H Zewail²

Affiliations

¹ SwissFEL, Paul Scherrer Institut , 5232 Villigen PSI, Switzerland.
² Physical Biology Center for Ultrafast Science and Technology, Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology , Pasadena, California 91125, USA.

Abstract

We demonstrate ultrafast core-electron energy-loss spectroscopy in four-dimensional electron microscopy as an element-specific probe of nanoscale dynamics. We apply it to the study of photoexcited graphite with femtosecond and nanosecond resolutions. The transient core-loss spectra, in combination with ab initio molecular dynamics simulations, reveal the elongation of the carbon-carbon bonds, even though the overall behavior is a contraction of the crystal lattice. A prompt energy-gap shrinkage is observed on the picosecond time scale, which is caused by local bond length elongation and the direct renormalization of band energies due to temperature-dependent electron-phonon interactions.