Direct Observation of Optically Induced Transient Structures in Graphite Using Ultrafast Electron Crystallography
2008; American Physical Society; Volume: 101; Issue: 7 Linguagem: Inglês
10.1103/physrevlett.101.077401
ISSN1092-0145
AutoresRamani K. Raman, Yoshie Murooka, Chong‐Yu Ruan, Teng Yang, Savaş Berber, David Tománek,
Tópico(s)Ion-surface interactions and analysis
ResumoWe use ultrafast electron crystallography to study structural changes induced in graphite by a femtosecond laser pulse. At moderate fluences of < or =21 mJ/cm2, lattice vibrations are observed to thermalize on a time scale of approximately 8 ps. At higher fluences approaching the damage threshold, lattice vibration amplitudes saturate. Following a marked initial contraction, graphite is driven nonthermally into a transient state with sp3-like character, forming interlayer bonds. Using ab initio density functional calculations, we trace the governing mechanism back to electronic structure changes following the photoexcitation.
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