The Formation of Warm Dense Matter: Experimental Evidence for Electronic Bond Hardening in Gold

Under strong optical excitation conditions, it is possible to create highly nonequilibrium states of matter. The nuclear response is determined by the rate of energy transfer from the excited electrons to the nuclei and the instantaneous effect of change in electron distribution on the interatomic potential energy landscape. We used femtosecond electron diffraction to follow the structural evolution of strongly excited gold under these transient electronic conditions. Generally, materials become softer with excitation. In contrast, the rate of disordering of the gold lattice is found to be retarded at excitation levels up to 2.85 megajoules per kilogram with respect to the degree of lattice heating, which is indicative of increased lattice stability at high effective electronic temperatures, a predicted effect that illustrates the strong correlation between electronic structure and lattice bonding.

[1]  J. Dwyer,et al.  Femtosecond electron diffraction: ‘making the molecular movie’ , 2006, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences.

[2]  Dynamics of size-selected gold nanoparticles studied by ultrafast electron nanocrystallography. , 2007, Nano letters.

[3]  Leonid V. Zhigilei,et al.  Combined atomistic-continuum modeling of short-pulse laser melting and disintegration of metal films , 2003 .

[4]  Chunlei Guo,et al.  Nonthermal component in heat-induced structural deformation and phase transition in gold , 2000 .

[5]  J. Hajdu,et al.  X-ray diffuse scattering measurements of nucleation dynamics at femtosecond resolution. , 2008, Physical review letters.

[6]  T. N. Hansen,et al.  Atomic-Scale Visualization of Inertial Dynamics , 2005, Science.

[7]  Martin E. Garcia,et al.  Anharmonic noninertial lattice dynamics during ultrafast nonthermal melting of InSb. , 2008, Physical review letters.

[8]  R. Biswas,et al.  Phonon spectrum of a model of electronically excited silicon , 1982 .

[9]  Maher Harb,et al.  Grating enhanced ponderomotive scattering for visualization and full characterization of femtosecond electron pulses. , 2008, Optics express.

[10]  M. Kandyla,et al.  Femtosecond dynamics of the laser-induced solid-to-liquid phase transition in aluminum , 2007, 2007 Quantum Electronics and Laser Science Conference.

[11]  Zhibin Lin,et al.  Time-resolved diffraction profiles and atomic dynamics in short-pulse laser-induced structural transformations: Molecular dynamics study , 2006 .

[12]  Jason R. Dwyer,et al.  An Atomic-Level View of Melting Using Femtosecond Electron Diffraction , 2003, Science.

[13]  V. Recoules,et al.  Ab-initio simulations of the optical properties of warm dense gold. , 2005, Physical review letters.

[14]  Zhibin Lin,et al.  Electron-phonon coupling and electron heat capacity of metals under conditions of strong electron-phonon nonequilibrium , 2008 .

[15]  Gilbert W. Collins,et al.  Broadband dielectric function of nonequilibrium warm dense gold. , 2006, Physical review letters.

[16]  Jason R. Dwyer,et al.  Femtosecond electron diffraction studies of strongly driven structural phase transitions , 2004 .

[17]  Christian Dahmen,et al.  Laser-induced heating and melting of gold nanoparticles studied by time-resolved x-ray scattering , 2004 .

[18]  G. Zerah,et al.  Formation enthalpies of monovacancies in aluminum and gold under the condition of intense laser irradiation , 2007 .

[19]  Klaus Sokolowski-Tinten,et al.  Ultrafast thermal melting of laser-excited solids by homogeneous nucleation , 2002 .

[20]  Y. Ping,et al.  Optical properties in nonequilibrium phase transitions. , 2006, Physical review letters.

[21]  S. Fourmaux,et al.  Non-thermal melting in semiconductors measured at femtosecond resolution , 2001, Nature.

[22]  Tommy Ao,et al.  Single-State Measurement of Electrical Conductivity of Warm Dense Gold , 2004 .

[23]  G. Radi.  Complex lattice potentials in electron diffraction calculated for a number of crystals , 1970 .

[24]  Juris Blums,et al.  Femtosecond X-ray measurement of coherent lattice vibrations near the Lindemann stability limit , 2003, Nature.

[25]  G Zérah,et al.  Effect of intense laser irradiation on the lattice stability of semiconductors and metals. , 2006, Physical review letters.

[26]  J. Güdde,et al.  Electron and lattice dynamics following optical excitation of metals , 2000 .

[27]  M. Lagally,et al.  Electronically driven structure changes of Si captured by femtosecond electron diffraction. , 2008, Physical review letters.

[28]  J. Hajdu,et al.  Ultrafast Bond Softening in Bismuth: Mapping a Solid's Interatomic Potential with X-rays , 2007, Science.