Abstract
We use ultrafast electron crystallography to study structural changes induced in graphite by a femtosecond laser pulse. At moderate fluences of , lattice vibrations are observed to thermalize on a time scale of . 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 -like character, forming interlayer bonds. Using ab initio density functional calculations, we trace the governing mechanism back to electronic structure changes following the photoexcitation.
- Received 27 July 2007
DOI:https://doi.org/10.1103/PhysRevLett.101.077401
©2008 American Physical Society