Ultrafast XAFS measurements on laser excited Ge films

Edward A. Stern, Dale Brewe

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

3 Scopus citations


Laser-pump/x-ray-probe measurements were made on Ge films with nominal time-delay steps of 18 ps. The response of the Ge lattice to the excitation of a high efficiency 200 fs pulse laser operating at 800 nm wavelength and at the Advanced Photon Source (APS) ring frequency of 272 kHz is probed by x-ray absorption fine structure (XAFS) measurements which determine the time dependences of the local structure. Initially the lattice response is dominated by a large increase of the RMS nearest neighbor bond disorder that decays within a single delay step. The next nearest neighbor RMS disorder shows an increase delayed by ∼ 30 ps, consistent with only optical modes dominating the initial lattice response and other phonons being excited more slowly. The different rate of excitation of optical than the rest of phonons require a different mechanism for exciting the optical phonons. Because the laser excites electrons from binding to anti-binding states, a Franck-Condon like effect is suggested as the cause of this initial response, instead of the standard hot electron-hole coupling to phonons.

Original languageEnglish
Title of host publicationX-RAY ABSORPTION FINE STRUCTURE - XAFS13
Subtitle of host publication13th International Conference
Number of pages5
StatePublished - 2007
Externally publishedYes
EventX-RAY ABSORPTION FINE STRUCTURE - XAFS13: 13th International Conference - Stanford, CA, United States
Duration: 9 Jul 200614 Jul 2006

Publication series

NameAIP Conference Proceedings
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616


ConferenceX-RAY ABSORPTION FINE STRUCTURE - XAFS13: 13th International Conference
Country/TerritoryUnited States
CityStanford, CA


  • Franck-Condon effect
  • Germanium
  • Laser-pump/x-ray-probe
  • Ultrafast
  • XAFS


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