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11.
S. N. Terekhov P. Mojzes S. M. Kachan N. I. Mukhurov S. P. Zhvavyi A. Yu. Panarin I. A. Khodasevich V. A. Orlovich A. Thorel F. Grillon P.‐Y. Turpin 《Journal of Raman spectroscopy : JRS》2011,42(1):12-20
Three types of Ag‐coated arrays from porous anodic aluminum oxide (AAO) were prepared and studied as substrates for surface‐enhanced Raman scattering (SERS). They were compared with Ag‐coated porous silicon (PSi) samples. AAO‐based substrates were prepared by the vapor deposition of silver directly onto the surface of porous AAO with different morphologies of the pores, whereas SERS‐active island films on the PSi were prepared by immersion plating. The resulting metallic nanostructures were characterized by UV‐vis absorption spectroscopy and scanning electron microscopy (SEM). Thermal evaporation leads to the formation of granular arrays of Ag nanoparticles on the surface of AAO. SERS activity of the substrates was tested using water‐soluble cationic Zn(II)‐tetrakis (4‐N‐methylpyridyl) porphyrin (ZnTMPyP4) as a probe molecule. The results indicate that all AAO‐based substrates studied here exhibit some degree of SERS activity. Noteworthy, for excitation at 532 nm, signals from AAO‐based substrates were comparable with those from the PSi‐based ones, whereas for 441.6 nm excitation they were about twice higher. The strongest SERS‐enhancement at 441.6 nm excitationwas provided by the AAO substrates with silver deposited on the monolith (originally nonporous) side of AAO. Preferential SERS‐enhancement of the bands ascribed to the vibrations of the N‐methylpyridinium group of ZnTMPyP4 when going to blue excitation was found. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
12.
P. Balcou R. Haroutunian S. Sebban G. Grillon A. Rousse G. Mullot J.-P. Chambaret G. Rey A. Antonetti D. Hulin L. Roos D. Descamps M.B. Gaarde A. L’Huillier E. Constant E. Mevel D. von der Linde A. Orisch A. Tarasevitch U. Teubner D. Klöpfel W. Theobald 《Applied physics. B, Lasers and optics》2002,74(6):509-515
We present a review of some recent results on high-order-harmonic generation, aiming at optimizing the photon flux to allow
for future applications in extreme-ultra-violet non-linear optics. We first present new schemes to control phase matching
of high harmonics in gases, by using the effect of the spatially varying atomic phase displayed by the high harmonics. An
enhancement by a factor of 50 is observed in neon in conditions for which the gradient of the atomic dispersion balances the
electronic dispersion. A new scheme to manipulate the laser field was demonstrated, and shown to improve phase matching. We
then turn to high-harmonic generation by solid targets, and show that high harmonics generated by an intense 30-fs laser pulse
remain collimated even at the threshold of the relativistic regime.
Received: 5 December 2001 / Published online: 24 April 2002 相似文献
13.
Grillon G Balcou P Chambaret J Hulin D Martino J Moustaizis S Notebaert L Pittman M Pussieux T Rousse A Rousseau J Sebban S Sublemontier O Schmidt M 《Physical review letters》2002,89(6):065005
Following the interaction of superintense, short pulse lasers and plasmas, ions can be accelerated to velocities sufficient to drive nuclear fusion reactions, in particular, by the process of Coulomb explosion of clusters [T. Ditmire, Nature (London) 398, 491 (1999)]]. We show here how short bursts of neutrons can be produced using a jet of low-density deuterated methane clusters. Ion velocity distributions were simultaneously measured by a Thomson parabola mass spectrometer, demonstrating deuteron energies up to 120 keV. We show that, in such conditions, nuclear fusion will occur not only in the hot plasma core, but also in the cold outer region by collision processes. 相似文献
14.
Bastiani S Audebert P Geindre JP Schlegel T Gauthier JC Quoix C Hamoniaux G Grillon G Antonetti A 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》1999,60(3):3439-3442
We have studied the distribution function of the hot electrons produced during the interaction of a 120-fs, 60-mJ, 800-nm wavelength and a p-polarized laser pulse with bilayered Al/Fe targets. The main pulse interacts with a preformed plasma, obtained with a controlled prepulse, whose density gradient scale length has been measured. The electron distribution function is characterized by means of the Kalpha emission of the two materials of the target as a function of the Al-layer thickness. The low-energy region (<50 keV) of the hot-electron distribution function shows no dependency in shape on the gradient scale length, but only a variation in the total number of the generated electrons. The comparison between the experimental results and the particle-in-cell and Monte Carlo calculations of the electron distribution function and the Kalpha emission is gratifying. 相似文献
15.
Valentin C Douillet D Kazamias S Lefrou T Grillon G Augé F Mullot G Balcou P Mercère P Zeitoun P 《Optics letters》2003,28(12):1049-1051
We present a direct method of studying the focusability of an intense, short-pulse extreme-ultraviolet (XUV) beam obtained by high-harmonic generation. We perform near-field imaging of the focal spot of five high-harmonic orders strongly focused by a broadband toroidal mirror. To visualize the focal spot directly, we image the fluorescence induced by an XUV beam on a cerium-doped YAG crystal on a visible CCD camera. We can thus measure the harmonic spot size on a single image, together with the Strehl ratio, to evaluate the quality of focusing. Such techniques should become instrumental in optimizing the focusing conditions and reaching intensities required for exploring attosecond nonlinear optics in the XUV range. 相似文献
16.
C. Valentin S. Kazamias D. Douillet G. Grillon T. Lefrou F. Augé S. Sebban P. Balcou 《Applied physics. B, Lasers and optics》2004,78(7-8):845-849
A variety of complex phenomena occurs when an ultra-short laser pulse interacts with atoms in the 1013 W/cm2 range: non-sequential ionisation, electron recollision, and Freeman resonances. We show that high-harmonic spectra obtained experimentally in this parameter range also display anomalous features, which are difficult to understand in the framework of the three-step, semiclassical model. The results of a systematic study of these high harmonics generated in argon, xenon, and krypton are presented. From the experimental curves, complex high-order harmonic generation phenomena are discussed. PACS 42.65.Ky; 32.80.Rm 相似文献
17.
François Grillon 《Mikrochimica acta》2006,155(1-2):157-161
The images obtained with a transmission electron detector in low voltage SEM show an evolution of the well known dark field
and bright field contrast with the accelerating voltage. Monte Carlo simulations explain these contrasts by the evolution
of the electron scattering angle and stopping power of the thin foil with the accelerating voltage. 相似文献
18.
D. Bernard F. Moulin F. Amiranoff A. Braun J.P. Chambaret G. Darpentigny G. Grillon S. Ranc F. Perrone 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2000,10(1):141-145
We have searched for stimulated photon scattering in vacuum at a center of mass photon energy of 0.8 eV. The QED contribution
to this process is equivalent to four wave mixing in vacuum. No evidence for scattering was observed. The corresponding upper limit of the cross-section is .
Received 29 September 1999 相似文献
19.
Sebban S Haroutunian R Balcou P Grillon G Rousse A Kazamias S Marin T Rousseau JP Notebaert L Pittman M Chambaret JP Antonetti A Hulin D Ros D Klisnick A Carillon A Jaeglé P Jamelot G Wyart JF 《Physical review letters》2001,86(14):3004-3007
We report the first saturated amplification of an optical-field-ionization soft x-ray laser. The amplifying medium is generated by focusing a circularly polarized 330-mJ, 35-fs, 10-Hz Ti:sapphire laser system in a few-mm cell filled with xenon. A gain of 67 cm(-1) on the 4d(9)5p-4d(9)5d transition at 41.8 nm in Pd-like xenon and a gain-length product of 15 have been inferred at saturation. This source delivers about 5 x 10(9) photons per pulse. The influence of the pumping energy and the laser polarization on the lasing output are also presented. 相似文献
20.
By use of a double beam technique, we were able to observe, in the OKE dynamics of many non saturated organic compounds, a very fast decay response superimposed upon the much slower decline of the usual effect of molecular origin. 相似文献