title: Observation of inhibited electron-ion coupling in strongly heated graphite.
abstract: Creating non-equilibrium states of matter with highly unequal electron and lattice temperatures (T(ele)≠T(ion)) allows unsurpassed insight into the dynamic coupling between electrons and ions through time-resolved energy relaxation measurements. Recent studies on low-temperature laser-heated graphite suggest a complex energy exchange when compared to other materials. To avoid problems related to surface preparation, crystal quality and poor understanding of the energy deposition and transport mechanisms, we apply a different energy deposition mechanism, via laser-accelerated protons, to isochorically and non-radiatively heat macroscopic graphite samples up to temperatures close to the melting threshold. Using time-resolved x ray diffraction, we show clear evidence of a very small electron-ion energy transfer, yielding approximately three times longer relaxation times than previously reported. This is indicative of the existence of an energy transfer bottleneck in non-equilibrium warm dense matter.
authors.affiliation: University of Oxford, Clarendon Laboratory, Parks Road, Oxford, OX1 3PU, UK. thomas.white@physics.ox.ac.uk
authors.forename: T G
authors.initials: TG
authors.lastname: White
authors.forename: J
authors.initials: J
authors.lastname: Vorberger
authors.forename: C R D
authors.initials: CR
authors.lastname: Brown
authors.forename: B J B
authors.initials: BJ
authors.lastname: Crowley
authors.forename: P
authors.initials: P
authors.lastname: Davis
authors.forename: S H
authors.initials: SH
authors.lastname: Glenzer
authors.forename: J W O
authors.initials: JW
authors.lastname: Harris
authors.forename: D C
authors.initials: DC
authors.lastname: Hochhaus
authors.forename: S
authors.initials: S
authors.lastname: Le Pape
authors.forename: T
authors.initials: T
authors.lastname: Ma
authors.forename: C D
authors.initials: CD
authors.lastname: Murphy
authors.forename: P
authors.initials: P
authors.lastname: Neumayer
authors.forename: L K
authors.initials: LK
authors.lastname: Pattison
authors.forename: S
authors.initials: S
authors.lastname: Richardson
authors.forename: D O
authors.initials: DO
authors.lastname: Gericke
authors.forename: G
authors.initials: G
authors.lastname: Gregori