共查询到20条相似文献,搜索用时 46 毫秒
1.
B. N. Mironov S. A. Aseev S. V. Chekalin V. F. Ivanov O. L. Gribkova 《JETP Letters》2013,96(9):601-603
The possibility of the desorption of complicated molecular complexes by soft X rays resulting from a solid target irradiated by a single sharply focused femtosecond laser pulse with an energy of several millijoules has been experimentally demonstrated for polyaniline, which is an organic conducting polymer. X-ray desorption and photodesorption of polyaniline by femtosecond laser pulses have been compared using a time-of-flight mass spectrometer. The results provide the possibility of studying surfaces with spatial nanoresolution and high elemental (chemical) selectivity, as well as observing the photodesorption with a high temporal resolution. 相似文献
2.
N. Petit F. Gervais P. Buvat P. Hourquebie P. Topart 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(3):367-372
The reflectivity spectrum of a polyaniline CSA-doped in presence of m-cresol has been measured over the wide wavenumber range
of 15- 9 000 cm
-1 (0.002-1.1 eV) at room temperature. Experimental data compare well with similar experiments performed by another group. The
conductivity spectrum of this conducting polymer has been deduced from the reflectivity spectrum by means of two methods,
Kramers-Kronig transformation and best fit of an “extended Drude” model to the reflectivity spectrum. Whereas the deviation
from Drude behavior was interpreted in terms of Anderson localization or by inhomogeneous disorder by other groups, it is
shown here that a different model developed for conducting oxides that also exhibit non-Drude behavior, applies very well
to this example of conducting polymer.
Received 11 February 1999 and Received in final form 26 April 1999 相似文献
3.
We report the synthesis of an organic–inorganic hybrid material composed of a conducting polyaniline (PANI) matrix and Prussian blue (PB) network, the latter formed in situ in the polymer matrix. The hybrid was prepared by treating FeCl4 ?-doped PANI with K3Fe(CN)6 unlike the previously reported method of potential cycling to obtain alternate layers of PANI and PB. Cyclic voltammetry and X-ray photoelectron spectroscopy investigations confirmed the formation of a network typical of PB inside the PANI matrix. Infrared spectroscopy points to the formation of an extended network between Fe in PANI matrix and Fe from K3Fe(CN)6. Magnetization studies of the hybrid material showed ferromagnetic ordering with a T c of about 6?K. 相似文献
4.
A fiber-coupled laser-diode (LD) end-pumped Nd:GdVO4 slab continuous-wave (CW) 912-nm laser and an LD bar end-pumped Nd:GdVO4 slab CW 912-nm laser are both demonstrated in this paper. Using the fiber-coupled LD of end-pumped type, a highest CW 912-nm laser output power of 10.17 W is obtained with a high optical-to-optical conversion efficiency of 24.6% and a slope efficiency of 34.5%. The measured M2 factors of beam quality in x and y directions are 5.3 and 5.1, respectively. Besides, an LD bar of end-pumped type is used to realize CW 912-nm laser output, which has the advantages of compactness and low cost. When the pump power is 38.8 W, the output power is 8.87 W and the measured M2 factors of beam quality in x and y directions are 16 and 1.31, respectively. In order to improve the beam quality of the 912-nm laser at x direction, a new quasi-concentric laser resonator will be designed, and an LD bar end-pumped Nd:GdVO4 slab high-power CW 912-nm TEM00 laser will be realized in the future. 相似文献
5.
G. P. Smith B. Krancevic D. L. Huestis H. Oser 《Applied physics. B, Lasers and optics》2009,94(1):127-132
Pulsed laser desorption of non-volatile organic dye molecules paraterphenyl and tetra-t-butyl-p-quinquephenyl (QUI) was studied
using gas phase ultraviolet laser induced fluorescence, following heating of a steel substrate by a pulsed 1.06-μm Nd:YAG laser. The fluorescence signal intensity is linear in concentration up to at least 30 monolayers and shows infrared
power threshold behavior, as expected for evaporation, at ∼0.2 J/cm2. Similar signal levels were also observed in air, with 532-nm heating, and using other metallic or dark black surfaces. 相似文献
6.
B. A. Zon A. S. Kornev E. B. Tulenko 《Journal of Experimental and Theoretical Physics》2010,111(6):921-935
Some of the many-body effects in the formation of multiply charged ions in a laser field have been taken into account: inelastic
tunneling, collective tunneling, and magnetic moment projection relaxation of the atomic core. Strong fields with an intensity
exceeding 1017 W cm−2 are considered when the magnetic component of the laser field acts on the free motion of a photoelectron; therefore, the
formation of multiply charged ions through rescattering becomes unlikely. Numerical calculations have been performed for Ar9+ … Ar13+, Kr19+ … Kr23+, Rb10+, and Rb11+ ions. A significant contribution of collective tunneling, which was not observed in weaker fields investigated previously,
has been revealed. Allowance for collective tunneling is shown to reduce the intensity leading to saturation by more than
10%. In this case, the yield of multiply charged Rb ions changes by an order of magnitude, while the yield of multiply charged
Ar and Kr ions changes by more than a factor of 2. Comparison with experimental data on the formation of argon ions under
the action of a linearly polarized laser pulse is made. 相似文献
7.
The generation of lower (third) and higher harmonics of femtosecond laser radiation in plasmas produced by laser ablation
of different targets with a small atomic number Z (B, Be, Li) has been investigated. The high (10−3) efficiency of third-harmonic generation was observed in plasma produced on the boron surface. Efficient third-harmonic generation
was also observed in beryllium plasma using femtosecond pulses of Ti:sapphire laser radiation (λ = 790 nm) and its second
harmonic (395 nm). We could tune the higher harmonics generation spectrum by tuning the crystal converter when using 395-nm
radiation to be converted. It is shown that, in plasmas formed on targets with small Z, the conversion efficiency and limiting generated harmonic order depend on the delay between the ablation pulse and the pulse
to be converted. 相似文献
8.
U. Chakravarty P. A. Naik B. S. Rao V. Arora H. Singhal G. M. Bhalerao A. K. Sinha P. Tiwari P. D. Gupta 《Applied physics. B, Lasers and optics》2011,103(3):571-577
A comparative experimental study of the X-ray emission in the water-window spectral region has been performed using carbon
nanofibers (CNFs) of different sizes and graphite plate targets, irradiated with ultra-short (Ti:sapphire) laser pulses. More
than an order of magnitude enhancement in the X-ray yield is observed from CNFs of 60-nm diameter with respect to graphite
targets. The X-ray emission from CNFs of 160-nm diameter was also high. The integrated X-ray yield of these carbon-based targets
scales with the laser intensity (I
L) as IL ~ 1.3-1.4I_{\mathrm{L}}^{\sim 1.3-1.4} in the intensity range of 4×1016–4×1017 W/cm2. The effect of the laser pulse duration on the X-ray emission from the CNFs was also studied by varying the pulse duration
from 45 fs up to 3 ps at a constant fluence of 2×104 J/cm2. The optimum laser pulse duration for maximum X-ray emission increases with the diameter of the CNFs used. The results are
explained from physical considerations of heating and hydrodynamic expansion of the CNF plasma in which resonance field enhancement
takes place while passing through two times the critical density. The results add to the efforts towards achieving an efficient
low-cost water-window X-ray source for microscopy. 相似文献
9.
Flame-generated soot was heated using a pulsed laser, and temperatures of the irradiated soot were inferred by fitting the
Planck function to spectrally resolved laser-induced incandescence with the temperature as an adjustable parameter. The effect
of the wavelength dependence of the emissivity on the inferred temperatures of the irradiated soot was studied using selected
expressions for the soot emissivity in the fit. Depending upon the choice of the functional form of the emissivity, the maximum
temperature reached by the soot during the laser pulse was calculated to span a range of 341 K (3475–3816 K) at a 1064-nm
laser fluence of 0.1 J/cm2 and 456 K (4115–4571 K) at a 1064-nm laser fluence of 0.4 J/cm2 with a 1σ standard deviation about the mean of ∼25 K. Comparison of the present results with temperature measurements from previous
studies suggests that the emissivity may depend on flame conditions and that further investigation on the subject is needed.
The use of two-color or spectrally resolved LII to infer the soot temperature during or after laser heating requires a careful
characterization of the wavelength dependence of the emissivity. The spread in temperature leads to large uncertainties regarding
the physico-chemical processes occurring at the surface of the soot during the laser heating. 相似文献
10.
85 Rb, 5s2S1/2(F”=2)→6p2P1/2(F’=2,3) absorption resonance with the 88Sr+, 5s2S1/2→5p2P1/2 transition is exploited to provide a simple, effective frequency reference for a laser cooling/fluorescence excitation source
applied to single Sr+ ions. A modulation-free frequency stabilization system has been designed which uses the differential signal from two frequency-displaced
beams traversing a Rb cell and which probe the Doppler-broadened Rb S–P lineshape at microwatt power levels. The method is
applied to frequency lock a 422-nm frequency-doubled diode laser system that is used for excitation of a single 88Sr+ ion. Stable, long-term laser cooling and fluorescence are achieved using the frequency-stabilized 422-nm source resulting
in observed ion confinement times without adjustment of over 8 h, together with an improvement in single-ion loading efficiency.
Received: 12 February 1998 相似文献
11.
S. A. Aseev B. N. Mironov V. G. Minogin S. V. Chekalin V. S. Letokhov 《JETP Letters》2009,90(1):13-17
A method based on an original electron microscope created for investigating photoelectron beams is presented. It ensures a
nanometer spatial resolution and picosecond time resolution. Electrons appearing when a metal needle is irradiated by femtosecond
laser pulses are transmitted through a dielectric microcapillary and are subjected to a ponderomotive potential created by
femtosecond laser radiation focused near the capillary tip. The position-sensitive detection scheme allows for the detection
of the spatial profile of a photo-electron beam with a magnification of K ≅ 4 × 104. The time structure of the photoelectron beam is visualized by scanning the delay time between laser pulses irradiating the
needle and a laser pulse focused near the capillary tip. 相似文献
12.
Thin films of ZnSe and PEO–chitosan blend polymer doped with NH4I and iodine crystals were prepared to form the two sides of a semiconductor electrolyte junction. ZnSe was electrodeposited
on indium tin oxide (ITO) conducting glass. The polymer is a blend of 50 wt% chitosan and 50 wt% polyethylene oxide. The polymer
blend was complexed with ammonium iodide (NH4I), and some iodine crystals were added to the polymer–NH4I solution to provide the I−/I3−redox couple. The room temperature ionic conductivity of the polymer electrolyte is 4.32 × 10−6 S/cm. The polymer film was sandwiched between the ZnSe semiconductor and an ITO glass to form a ZnSe/polymer electrolyte/ITO
photovoltaic cell. The open circuit voltage (V
oc) of the fabricated cells ranges between 200 to 400 mV and the short circuit current between 7 to 10 μA. 相似文献
13.
Mareike Mathieu Steffen Franzka Jürgen Koch Boris N. Chichkov Nils Hartmann 《Applied Physics A: Materials Science & Processing》2010,101(3):461-466
Femtosecond laser patterning of alkanethiol monolayers on gold-coated silicon substrates at λ=800 nm, τ<30 fs and ambient conditions has been investigated. Single-pulse processing allows one to selectively remove the organic
coating. Subsequently, pattern transfer into the gold film via wet etching in ferri-/ferrocyanide solution is achieved. As
demonstrated, burr-free patterning can be carried out over an extremely wide range of laser pulse fluences from above 2 J/cm2 down to 0.5 J/cm2. Moreover, at low fluences, sub-wavelength processing down to λ/5 is feasible. In particular, at a 1/e laser spot diameter of about 1 μm, holes with diameters of 160 nm and step edges below
80 nm are fabricated. These results emphasize the prospects of organic monolayers as high-resolution resists in rapid nonlinear
femtosecond laser processing. 相似文献
14.
We have demonstrated proof-of-principle of an incoherent ArF∗ emission source with a quasi-point emission geometry using a laser-produced plasma in an Ar/F2/He/Ne mixed gas. The VUV emission characteristics, such as the emission size, were dependent on those of the plasma-initiating
laser. The average emission power was 10 μW at a repetition rate of 10 Hz at 193 nm. The average power conversion efficiency
of the 193-nm emission from the plasma-initiating Nd:YAG laser was 6.3×10−6. The average emission power at 193 nm was proportional to that of the plasma-initiating laser, indicating the scaling of
the emission source. 相似文献
15.
An attempt has been made to prepare a new proton conducting polymer electrolyte based on polyvinyl alcohol (PVA) doped with
NH4NO3 by solution casting technique. The complex formation between polymer and dissociated salt has been confirmed by X-ray diffraction
analysis. The ionic conductivity of the prepared polymer electrolyte has been found by ac impedance spectroscopic analysis.
The highest ionic conductivity has been found to be 7.5 × 10−3 Scm−1 at ambient temperature for 20 mol% NH4NO3-doped PVA with low activation energy (~0.19 eV). The temperature-dependent conductivity of the polymer electrolyte follows
an Arrhenius relationship, which shows hopping of ions in the polymer matrix. 相似文献
16.
Vas Dev M. L. Shah A. K. Pulhani B. M. Suri 《Applied physics. B, Lasers and optics》2005,80(4-5):587-594
A U–Ne hollow cathode discharge tube is used as a source of uranium atomic vapors as well as a photoelectron/photoion detector
for carrying out two-color three-photon photoionization spectroscopy of uranium. Using the uranium excitation transition 0
cm−1 (5L
6
0
) → 16 900.38 cm−1 (7M7) at 591.5-nm laser wavelength as a first step transition and scanning the wavelength of a second laser from 558 to 568 nm,
high-lying odd-parity atomic levels of uranium are studied in the energy region 34 500–34 813 cm−1. All the expected 21 odd-parity atomic levels identified by various researchers in this region are observed in a single spectrum,
demonstrating the high sensitivity achieved therein. In addition to this, we have identified eight autoionization resonances
of uranium starting from its odd-parity atomic level at 33 801.06 cm−1 pumped by two-photon excitation. Four out of these eight autoionization resonances are observed for the first time. 相似文献
17.
Low - cost, easily fabricated dry cells were constructed by gluing a composite conducting material or a metal sulphide on
magnesium or aluminium foils, using a solid electrolyte made from polyvinyl - pyrolidone. Composite conducting materials consisted
of polypyrrole and polyaniline incorporated into an inorganic or polymer matrix or cupric oxide incorporated into a styrene
- butadiene copolymer matrix. The efficiency, energy densities and voltage values of the cells were in the range 0.5 – 18.3
mWh cm−3, 9 – 339 wh kg−1 and 0.5 – 2.0 V, respectively. The energy densities of the cells were up to seventeen times more than the energy density
of the PbO2 -H2SO4 - Pb multiple charge / discharge system and up to ten times more than the energy density of the nickel / cadmium rechargeable
cell.
A dry cell composed solely from polymers was constructed with cell voltage 0.25 – 0.50 V and efficiency ranging from 0.07
to 0.13 mWh cm−3 ten times lower than other commercial cells.
Paper presented at the 1st Euroconference on Solid State Ionics, Zakynthos, Greece, 11–18 Sept. 1994 相似文献
18.
N. Pavel V. Lupei J. Saikawa T. Taira H. Kan 《Applied physics. B, Lasers and optics》2006,82(4):599-605
Laser emission in the 0.94-, 1.06- and 1.34-micron ranges in diluted and concentrated Nd:YAG crystals longitudinally pumped by a 885-nm diode laser on the 4
I
9/2→4
F
3/2 transition is investigated. Continuous-wave operation at watt level in all these wavelength ranges is demonstrated with a 1.0-at. % Nd:YAG crystal; however, the laser performance is impeded by the low pump absorption efficiency. Improved output power and overall efficiency were obtained with a highly doped 2.5-at. % Nd:YAG crystal: 5.5 W at 1.06 μm and 3.8 W at 1.34 μm with 0.38 and 0.26 efficiencies, respectively. Comparative results with traditional pumping at 809 nm into the highly absorbing 4
F
5/2 level are presented, showing the advantage of the direct 4
F
3/2 pumping. The influence of the lasing wavelength and of the Nd concentration on the thermal effects induced by the optical pumping in the laser material is discussed. A clear relation between the heat generated in the Nd:YAG crystals in lasing and non-lasing regimes, a function of the Nd doping, is demonstrated. PACS 42.55.Rz; 42.60.By; 42.60.Da 相似文献
19.
Steffen Duhm Ingo Salzmann Robert L. Johnson Norbert Koch 《Journal of Electron Spectroscopy and Related Phenomena》2009,174(1-3):40
The electronic structure of vacuum-sublimed layered organic heterostructures of pentacene (PEN) and fullerene (C60) on conducting polymer substrates was investigated using ultraviolet photoelectron spectroscopy (UPS). The conditions at the PEN/C60interface changed from thermodynamic non-equilibrium (i.e. the onset of the PEN highest occupied molecular orbital above the substrate Fermi-energy) for thin PEN coverages on C60 to thermodynamic equilibrium for thicker PEN coverages (i.e. Fermi-level pinning of PEN). This finding is attributed to a coverage-dependent pinhole connection of PEN through the C60 layer with the substrate. The experiments demonstrate the importance of organic thin film morphology for UPS measurements to assess the energy level alignment at organic/organic heterointerfaces. 相似文献
20.
We have measured the absorption of the 19.47-nm neon like bromine (J=2–1) X-ray laser line in low-pressure helium. The experiment
was motivated by the coincidence of this line with the low-absorption wing of an autoionizing transition in helium. We observe
that, with 1 mbar of helium, the continuum background and another bromine X-ray laser line at 19.82 nm are strongly reduced,
enhancing the relative strength of the 19.47-nm laser line. Increasing the helium pressure to 1.5 mbar makes the continuum
virtually disappear, resulting in an almost monochromatic emission of the X-ray laser line. An estimate of the absorption
cross section for the 19.47-nm line is given as ≈3.9×10-19 cm2 and for the nearby continuum as 0.9–1.3×10-18 cm2.
Received: 8 March 1999 / Revised version: 26 April 1999 / Published online: 11 August 1999 相似文献