Publications

2004

• Observation of high energy photoelectrons from solids at moderate laser intensity
  
  • N. Belsky A.
  • Bachau H.
  • Gaudin J.
  • Geoffroy G.
  • Guizard S.
  • Martin P.
  • Petite G.
  • Philippov A.
  • Vasil'Ev A.N.
  • N. Yatsenko B.
  Applied Physics B - Laser and Optics, Springer Verlag, 2004, 78, pp.989. We investigate the photoemission for a set of wide band-gap crystals irradiated by femtosecond Ti-Sapphire laser pulses at intensities varying from 0.5 to 6 TW/cm(2) (below the optical breakdown threshold). The measured total electron yield increases linearly with the laser intensity in this intensity range. An intense and wide plateau of high energy electrons appears in the photoelectron spectra at excitation intensities larger than 1 TW/cm(2). The exponential cut-off of this plateau reaches 40 eV at maximal applied intensities. In order to explain such a behavior, we propose a mechanism where the heating is due to a sequence of direct interbranch one- and multi-photon transitions in the conduction band
• Transition from Bose Glass to Normal State in the (K,Ba)BiO3 Superconductor
  
  • Klein T.
  • Marcenat C.
  • Blanchard S.
  • Marcus J.
  • Bourbonnais C.
  • Brusetti R.
  • J. van Der Beek C.
  • Konczykowski M.
  Physical Review Letters, American Physical Society, 2004, 92, pp.037005. The introduction of columnar defects in (K,Ba)BiO3 single crystals shifts both the irreversibility and thermodynamic transition lines, respectively, deduced from ac susceptibility (and/or transport) and specific heat measurements, upwards. This shift can be attributed to the defect-induced decrease of the difference (F) between the free energies in the superconducting and the normal states, assuming that the position of the superconducting transition is given by the condition |F|kBT/3. This criterion also perfectly reproduces the influence of the angle between the tracks and the external field. This result suggests that no vortex liquid phase exists in this system
• Electron acceleration by surface plasma waves in the interaction between femtosecond laser pulses and sharp-edged overdense plasmas
  
  • Kupersztych J
  • Raynaud M
  • Riconda C
  Physics of Plasmas, American Institute of Physics, 2004. The relativistic acceleration of electrons by the field of surface plasma waves created in the interaction between ultrashort high-intensity laser pulses with sharp-edged overdense plasmas has been investigated. It is shown that the initial phase of the wave experienced by the electrons play a leading part by yielding a well-defined peaked structure in the energy distribution function. This study suggests that resonant excitation of surface plasma waves could result in quasi-monokinetic energetic electron bunches. When the space charge field becomes too strong, this mechanism can evolve toward a true absorption process of the surface wave energy via an enhanced ''vacuum heating'' mechanism generalized to the case of surface plasma waves. (10.1063/1.1650353͔)
  DOI : 10.1063/1.1650353͔
• Comment on "Molecular dynamics study of the threshold displacement energy in vanadium
  
  • Vajda P.
  , 2004. The simulation study on Frenkel pair creation in vanadium by L.A. Zepeda-Ruiz et al. (Phys. Rev. B 67, 134114, 2003) is criticized for its lack of reference to existing experimental work and for generally inadequate treatment of literature data. Hence, the validity of the ensuing discussion of various results (e.g. the value of the minimum TDE and the Frenkel pair stability in V) is questioned.
• Spatially periodical structures, under femtosecond pulsed excitation of irradiated AI203 crystals
  
  • F. Martynovitch E.
  • Petite G.
  • P. Dresvianski V.
  • A. Starchenko A.
  Applied Physics Letters, American Institute of Physics, 2004, 84, pp.4550. Measuring the luminescence intensity of specially prepared irradiation defects induced in crystals, we observe that the longitudinal structure of quasi-interferences induced by two orthogonally polarized femtosecond pulses propagating together with different velocities is insensitive to the spatial broadening due to velocity dispersion in the crystals. On the contrary, it does depend on the pulse duration when it is changed by varying the spectral width of the radiation. It thus allows a direct measurement of the coherence time of such pulses. Stability of the axial selectivity is a good sign, taking away a number of serious limitations concerning possible applications
• Track formation in fluorapatite irradiated with energetic cluster ions
  
  • Jaskierowicz G.
  • Dunlop A.
  • Jonckheere R.
  Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, Elsevier, 2004, 222, pp.213. We present preliminary transmission electron microscopy observations on apatite samples irradiated at 300 K with 30 MeV C60 cluster ions up to fluences ranging from 1 × 1010 to 3 × 1011 cm-2. Each incoming projectile generates strong structural modifications in the vicinity of its path as a consequence of the very high density of energy deposited in electronic processes. It will be shown that a wide variety of morphologies is found in neighbouring tracks, some of them appearing as "continuous", whereas in the same sample region many consist of one or several alignments of droplets, which could be either voids or gas filled bubbles. Electron diffraction patterns seem to indicate that the core of the track do not consist of amorphous solid matter. The tracks induced under cluster irradiation evolve under the beam in the electron microscope. Some faceting of the damaged regions appears as the discontinuity along the track length increases