共查询到20条相似文献,搜索用时 390 毫秒
1.
This is a study of target destruction and the dynamics of surface plasma formation during the interaction of quasicontinuous
laser radiation (λ = 1.06 μm, q = 1–7 MW/cm2, τ ∼ 1.5 msec) with D16T duraluminum and bismuth in nitrogen atmospheres at pressures p = 1–20 atm. High speed photography and spectroscopy of the erosion plasma flare are used to determine the onset time for
vaporization of the target, as well as the times of appearance of erosion and nitrogen plasmas for different gas pressures
and laser energy fluxes q. The emergence of the plasma front from the vapor zone into the surrounding nitrogen is detected experimentally and the properties
of the nitrogen plasma are studied. 相似文献
2.
Hidetoshi Nakano Katsuya Oguri Yasuaki Okano Tadashi Nishikawa 《Applied Physics A: Materials Science & Processing》2010,101(3):523-531
We investigated spatiotemporal evolution of expanding ablation plume of aluminum created by a 100-fs, 1014–1015-W/cm2 laser pulse. For diagnosing dynamic behavior of ablation plume, we employed the spatiotemporally resolved X-ray absorption
spectroscopy (XAS) system that consists of a femtosecond-laser-plasma soft X-ray source and a Kirkpatrick–Baez (K–B) microscope.
We successfully assigned the ejected particles by analyzing structure of absorption spectra near the L
II,III absorption edge of Al, and we clarified the spatial distribution of Al+ ions, Al atoms, and liquid droplets of Al in the plume. We found that the ejected particles strongly depend the irradiated
laser intensity. The spatial distribution of atomic density and the expansion velocity of each type of particle were estimated
from the spatiotemporal evolution of ablation particles. We also investigated a temperature of the aluminum fine particles
in liquid phase during the plume expansion by analyzing the slope of the L
II,III absorption edge in case of 1014-W/cm2 laser irradiation where the nanoparticles are most efficiently produced. The result suggests that the ejected particles travel
in a vacuum as a liquid phase with a temperature of about 2500 to 4200 K in the early stage of plume expansion. 相似文献
3.
E.G. Gamaly A.V. Rode A. Perrone A. Zocco 《Applied Physics A: Materials Science & Processing》2001,73(2):143-149
We present two sets of experimental results on the ablation-rate decrease with increase of the number of consecutive laser
pulses hitting the same spot on the target surface. We have studied laser ablation of a carbon target with nanosecond pulses
in two different interaction regimes: one with a XeCl laser (λ=308 nm) and the other with a Nd:YAG laser (λ=1064 nm), in both
cases at the intensity ∼5×108 W/cm2 Two different mechanisms were found to be responsible for the ablation-rate decrease; they are directly related to the two
different laser–matter interaction regimes. The UV-laser interaction is in the regime of transparent vapour (surface absorption).
The increase of the neutral vapour density in the crater produced by the preceding laser pulses is the main reason for the
decrease of ablation rate. With the IR laser each single laser pulse interacts with a partially ionised plume. With increase
of the number of pulses hitting the same spot on the target surface, the laser–matter interaction regime gradually changes
from the near-surface absorption to the volume absorption, resulting in the decrease in absorption in the target and thus
in the decrease in the ablation rate. The change in the evaporation rate was considered for both vacuum and reactive-gas environments.
Received: 21 February 2001 / Accepted: 26 February 2001 / Published online: 23 May 2001 相似文献
4.
Philipp Reissaus Tomas Waldemarsson Jürgen Blum Dominik Clément Isabel Llamas Harald Mutschke Frank Giovane 《Journal of nanoparticle research》2006,8(5):693-703
In order to find reliable collector surfaces for the Mesospheric Aerosol – Genesis, Interaction and Composition (MAGIC) sounding rocket experiment, intended to collect atmospheric nanoparticles, the sticking efficiency of nanoparticles was measured on several targets of different materials. The nanoparticles were generated by a molecular beam apparatus in Jena, Germany, by laser ablation (Al2O3 particles, diameter 5–50 nm) and by laser pyrolysis (carbon particles, diameter 10–20 nm). In a vacuum environment (>10−5 mbar) the particles condensed from the gas phase, formed a particle beam, and were accelerated to ∼
∼1 km/s. The sticking efficiency on the target materials carbon, gold and grease was measured by a microbalance. Results demonstrate moderate to high sticking probabilities. Thus, the capture and retrieval of atmospheric nanoparticles was found to be quantitatively feasible. 相似文献
5.
We investigated the subpicosecond laser ablation of copper and fused silica under 100 fs laser irradiation at 800 nm in vacuum by means of fast plume imaging and time- and space-resolved optical emission spectroscopy. We found that, to the difference of copper ablation, the laser-generated plasma from a fused silica target exhibited one “main” component only. The “slow” plasma component, observed during copper ablation and usually assigned to optical emission from nanoparticles was not detected by either plasma fast imaging or optical emission spectroscopy even when fused silica targets were submitted to the highest incident fluences used in our experiments. The characteristic expansion velocity of this unique component was about three times larger than the velocity of the fast plume component observed during copper ablation. The dependence of laser fluence on both plasma expansion and ablation rate was investigated and discussed in terms of ablation efficiency and initiation mechanisms. 相似文献
6.
B. Hopp G. Kecskeméti T. Smausz T. Ajtai A. Filep N. Utry A. Kohut Z. Bozóki G. Szabó 《Applied Physics A: Materials Science & Processing》2012,107(2):429-435
Preparation of organic thin layers on various special substrates using the pulsed laser deposition (PLD) technique is an important
task from the point of view of bioengineering and biosensor technologies. Earlier studies demonstrated that particle ejection
starts during the ablating laser pulse resulting in significant shielding effects which can influence the real fluence on
the target surface and consequently the efficiency of layer preparation. In this study, we introduce a photoacoustic absorption
measurement technique for in-situ characterization of ablated particles during PLD experiments. A KrF excimer laser beam (λ=248 nm, FWHM=18 ns) was focused onto pepsin targets in a PLD chamber; the applied laser fluences were 440 and 660 mJ/cm2. We determined the wavelength dependence of optical absorption and mass specific absorption coefficient of laser ablation
generated pepsin aerosols in the UV–VIS–NIR range. On the basis of our measurements, we calculated the absorbance at the ablating
laser wavelength, too. We demonstrated that when the laser ablation generated pepsin aerosols spread through the whole PLD
chamber the effect of absorptivity is negligible for the subsequent pulses. However, the interaction of the laser pulse and
the just formed particle cloud generated by the same pulse is more significant. 相似文献
7.
O. A. Grebenshchikov V. B. Zalesskii V. V. Naumov 《Journal of Applied Spectroscopy》2006,73(2):313-316
We describe equipment and a procedure for measuring inhomogeneities in active regions of solar cells, photoelectric transducers,
and multielement photodetectors, based on a computer-controlled dual-beam laser scanner including a Pentium III personal computer,
an HP-34401A digital multimeter with RS-232 serial interface;, a platform movable along the Y coordinate with the sample multielement
photodetector to be tested and a microprobe device for picking up the photocurrents, an optical head with laser photodiodes
in the visible (λ1 = 0.68 μm) and IR (λ2 = 0.82 μm) ranges scanning along the X coordinate, and a control unit for focusing the laser beams λ1, λ2, stabilizing the laser radiation power, and controlling the step motors for the X,Y coordinates.
The equipment and procedure enable laser scanning of sample multielement photodetectors, with external dimensions 10 × 10
μm2 to 150 × 150 mm2, along the X, Y coordinates at a maximum rate of 100 mm/sec; minimum radiation power of the laser diodes, 10 mW; range of
laser beam diameters, 2–50 μm; range of scanning steps along the X, Y coordinates, 5–100 μm; current sensitivity 1·10−8 A, voltage sensitivity 1·10−7 V; measurement and analysis accuracy at least 0.5%; storage of color plots of the inhomogeneities in the active regions of
the multielement photodetectors on the hard disk of the personal computer, with output of analysis results to a monitor and
color printer, 32 color gradations. Software written in Delphi 7.0.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 277–280, March–April, 2006. 相似文献
8.
J.M. Auerhammer R. Walker A.F.G. van der Meer B. Jean 《Applied physics. B, Lasers and optics》1999,68(1):111-119
2 . Dynamic parameters such as the extension of the ablation cloud, the initial velocity and momentum of the ablated particles
as well as the ablation threshold, the ablated mass, and the particle size were investigated. The ablation plume was made
visible with a stroboscopic technique. For a fluence of 3.1 J/cm2 the average initial velocity of the ejected particles was deduced from the extension of the plume to range from 120–400 m/s.
Measurements of the recoil momentum using a sensitive pendulum led to values between 0.5 and 2.0 mm g/s. All measured properties
were related to the spectroscopically determined absorption coefficient of cornea αcornea. Where absorption due to proteins is high (at λ=6.2 and 6.5 μm), ablated mass, velocity and recoil momentum behave according
to αcornea. For the first time, variations of the ablation plume from pulse to pulse were observed. Those, as well as the particle size,
not only depend on the absorption coefficient, but also on the predominant absorber.
Received: 4 November 1997/Revised version: 7 September 1998 相似文献
9.
L. I. Burov A. S. Gorbatsevich A. G. Ryabtsev G. I. Ryabtsev A. N. Imenkov Yu. P. Yakovlev 《Journal of Applied Spectroscopy》2008,75(6):805-809
The spatial distribution of emission intensity in the active layer of a laser diode (LD) based on an InAsSb/InAsSbP heterostructure
(generation wavelength λgen ∼ 3.3 μm) is obtained for various stripe widths w by means of numerical solution of the wave equation in the 2D approximation
taking into account the refractive index nonlinearity. It has been shown that the special distribution of emission intensity
becomes strongly inhomogeneous at w values exceeding 9–10 μm, which results in the appearance of additional maxima in the
far-field pattern. Calculated far-field patterns in the active layer plane of the LD agree with corresponding experimental
data.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 804–808, November–December, 2008. 相似文献
10.
V. K. Goncharov K. V. Kozadaev V. I. Popechits M. V. Puzyrev 《Journal of Applied Spectroscopy》2008,75(6):892-897
We have used a combination of physical diagnostics methods (laser probe, absorption spectroscopy, transmission electron microscopy)
to study an aqueous suspension of silver nanoparticles, formed by laser ablation of a metal target in the atmosphere. We have
established that application of the methods described allows us to obtain the most complete information about the state of
nanosized metal particles in optically transparent media.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 896–901, November–December, 2008. 相似文献
11.
We have studied multiple regressions between the spectral aerosol extinction coefficient ε, backscatter indicatrix gπ, and light-scattering coefficients βθ at angles of θ = 1–180°, which we used to select the optimal scattering angle for determining the extinction coefficient
at the wavelengths 0.350, 0.532, and 1.060 μm. We have estimated the errors in determination of the values of ε and gπ at the given wavelengths for different atmospheric situations with different meteorological parameters. We have shown that
it is possible to use the spectral βθ values at a 33° angle to determine the reference values for ε(λ) and gπ(λ) at λ = 0.350, 0.532, and 1.060 μm in laser detection and ranging (lidar) measurements, and we give examples of recovering
the vertical profiles of ε in a slightly turbid atmosphere from the results of simultaneous multiwavelength lidar and nephelometric
measurements.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 6, pp. 767–772, November–December, 2007. 相似文献
12.
M. H. Mahdieh H. Hosseini?Shokoh 《Applied Physics A: Materials Science & Processing》2012,106(4):995-1004
In this paper we present evidence for a phase explosion during the laser-induced ablation process by studying the optical
reflectivity of the ablated plume. The ablation was produced by irradiating thin film aluminum coated on a quartz substrate
with a single pulse laser beam in ambient air. The laser pulse was provided by the second harmonic of a Q-switched Nd:YAG
laser with ∼10 ns pulse duration. The transmission of a low power He–Ne laser beam through the hot ablated material plume
and its reflection (from the front surface, and rear surface of aluminum film) were also monitored during the duration of
the ablation event. The results show that the front surface reflectivity is enhanced at an early time of ablation which is
described as strong evidence for the creation of a phase explosion in this process. 相似文献
13.
We have shown that brief exposure of sturgeon embryos (fertilized roe) in the organogenesis stage to low-intensity radiation
in the visible region of the spectrum can have a long-term effect on embryonic and post-embryonic development of the fish,
detectable 50 days after the irradiation procedure. The biological effects (size-weight characteristics and hardiness parameters
of the fish relative to unfavorable habitat conditions) induced by linearly polarized emission from a monochromatic laser
source (helium-neon laser, λ = 632.8 nm, Δλ ≈ 0.02 nm) and a quasi-monochromatic light-emitting diode (LED) source (maximum
in emission spectrum λ = 631 nm, Δ λ = 15 nm) are practically the same. Going to broadband linearly polarized radiation (λ
= 420–800 nm) is accompanied by a decrease in the biological effect.
From the results of studies of the effect on embryos from linearly polarized and unpolarized radiation from an LED source
and also the effect of linearly polarized, circularly polarized, and unpolarized radiation from a helium-neon laser, we concluded
that the type of polarization is of critical importance in realization of the biological effect of radiation. In this case,
the maximum stimulating effect (on the size×weight characteristics and the hardiness parameters for juvenile fish) is observed
on exposure to linearly polarized radiation; the photobiological effect induced in the same dose range by light with natural
polarization (i.e., unpolarized) is significantly less pronounced; the stimulating effect of circularly polarized radiation
occupies an intermediate position.
Based on the presented data and also on data obtained previously, we conclude that among the resonant and nonresonant photophysical
processes (orientational effect of light, effect of gradient forces, dipole-dipole interactions, thermooptic processes) capable
of inducing photobiological effects dependent on such laser-specific characteristics as polarization and coherence, the determining
influence in the processes studied in this work comes from the orientational effect of light and dipole×dipole interactions.
And the orientational effect can appear for anisotropic media with liquid-crystal type ordering (especially domains in membranes
and multiple-enzyme complexes) both under conditions when there is no resonant absorption and for weakly absorbing structures,
and can initiate a change in their conformations and accordingly their functional characteristics.
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 6, pp. 843–858, November–December, 2008. 相似文献
14.
L. G. Samsonova N. S. Eremina V. A. Svetlichnyi T. N. Kopylova G. V. Maier N. S. Kobotaeva E. E. Sirotkina 《Journal of Applied Spectroscopy》2006,73(2):194-199
We have studied the spectral and lasing properties of 4-dicyanomethylene-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM)
in polyepoxypropylcarbazole (PEPK), polybutylcarbazole (PBK), and polyvinylcarbazole (PVK) films when excited by emission
from a XeCl laser (λ = 308 nm) and the second harmonic of a YAGNd laser (λ = 532 nm). Stimulated emission was excited without
an external cavity in the traveling wave mode in films of thickness 0.5–0.8 μm, obtained by the centrifuging method.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 177–181, March–April, 2006. 相似文献
15.
S. Amoruso R. Bruzzese C. Pagano X. Wang 《Applied Physics A: Materials Science & Processing》2007,89(4):1017-1024
We present an experimental characterization describing the characteristics features of the plasma plume dynamics and material
removal efficiency during ultrashort, visible (527 nm, ≈300 fs) laser ablation of nickel in high vacuum. The spatio-temporal
structure and expansion dynamics of the laser ablation plasma plume are investigated by using both time-gated fast imaging
and optical emission spectroscopy. The spatio-temporal evolution of the ablation plume exhibits a layered structure which
changes with the laser pulse fluence F. At low laser fluences (F<0.5 J/cm2) the plume consists of two main populations: fast Ni atoms and slower Ni nanoparticles, with average velocities of ≈104 m/s for the atomic state and ≈102 m/s for the condensed state. At larger fluences (F>0.5 J/cm2), a third component of much faster atoms is observed to precede the main atomic plume component. These atoms can be ascribed
to the recombination of faster ions with electrons in the early stages of the plume evolution. A particularly interesting
feature of our analysis is that the study of the ablation efficiency as a function of the laser fluence indicates the existence
of an optimal fluence range (a maximum) for nanoparticles generation, and an increase of atomization at larger fluences.
PACS 52.50.-b; 52.38.Mf; 79.20.Ds; 81.07.-b 相似文献
16.
A. I. Vodchits V. I. Dashkevich N. S. Kazak V. K. Pavlenko V. I. Pokryshkin I. P. Petrovich V. V. Rukhovets A. S. Kraskovskii V. A. Orlovich 《Journal of Applied Spectroscopy》2006,73(2):285-291
We have studied an optical parametric oscillator (OPO) with an unstable telescopic cavity, placed inside the cavity of an
actively Q-switched multimode Nd3+:KGW pump laser. We used a KTP crystal as the nonlinear medium for the OPO. We have compared the emission characteristics
of OPOs with unstable telescopic and planar cavities. We have established that compared with the planar cavity, the unstable
cavity reduces the OPO beam divergence and improves the spatial distribution of the radiation energy in the far wave zone.
Based on our investigations, we have designed a compact eye-safe (λ = 1.578 μm) laser source with natural cooling, emitting
(for electrical pumping energy 7.3 J) pulses with pulse energy 22 mJ and pulse duration 6 nsec. The FWHM beam divergence for
the source is no greater than 3.5 mrad.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 254–259, March–April, 2006. 相似文献
17.
E. Yu. Loktionov A. V. Ovchinnikov Yu. Yu. Protasov D. S. Sitnikov 《Journal of Applied Spectroscopy》2010,77(4):561-568
We present the results of an experimental study of the ablation energy thresholds and ablated mass for a number of refractory
metals (Ti, Zr, Nb, Mo) by femtosecond (τ
0.5 = 45–70 fs) exposed to laser pulses in the ultraviolet — near infrared range (λ = 266, 400, 800 nm) under atmospheric conditions and under vacuum (p ~ 10–2 Pa). We have analyzed the ablation efficiency (mass yield per unit energy of the acting coherent radiation) and ablation
energy thresholds vs. the laser pulse duration and photon energy. 相似文献
18.
Molecular imaging by Mid-IR laser ablation mass spectrometry 总被引:1,自引:0,他引:1
Akos Vertes Peter Nemes Bindesh Shrestha Alexis A. Barton Zhaoyang Chen Yue Li 《Applied Physics A: Materials Science & Processing》2008,93(4):885-891
Mid-IR laser ablation at atmospheric pressure (AP) produces a mixture of ions, neutrals, clusters, and particles with a size
distribution extending into the nanoparticle range. Using external electric fields the ions can be extracted and sampled by
a mass spectrometer. In AP infrared (IR) matrix-assisted laser desorption ionization (MALDI) experiments, the plume was shown
to contain an appreciable proportion of ionic components that reflected the composition of the ablated target and enabled
mass spectrometric analysis. The detected ion intensities rapidly declined with increasing distance of sampling from the ablated
surface to ∼4 mm. This was rationalized in terms of ion recombination and the stopping of the plume expansion by the background
gas. In laser ablation electrospray ionization (LAESI) experiments, the ablation plume was intercepted by an electrospray.
The neutral particles in the plume were ionized by the charged droplets in the spray and enabled the detection of large molecules
(up to 66 kDa). Maximum ion production in LAESI was observed at large (∼15 mm) spray axis to ablated surface distance indicating
a radically different ion formation mechanism compared to AP IR-MALDI. The feasibility of molecular imaging by both AP IR-MALDI
and LAESI was demonstrated on targets with mock patterns.
Presented at the 9-th International Conference on Laser Ablation, 2007 Tenerife, Canary Islands, Spain 相似文献
19.
M. Sanz M. López-Arias E. Rebollar R. de Nalda M. Castillejo 《Journal of nanoparticle research》2011,13(12):6621-6631
Nanostructured CdS and ZnS films on Si (100) substrates were obtained by nanosecond pulsed laser deposition at the wavelengths
of 266 and 532 nm. The effect of laser irradiation wavelength on the surface structure and crystallinity of deposits was characterized,
together with the composition, expansion dynamics and thermodynamic parameters of the ablation plume. Deposits were analyzed
by environmental scanning electron microscopy, atomic force microscopy and X-ray diffraction, while in situ monitoring of
the plume was carried out with spectral, temporal and spatial resolution by optical emission spectroscopy. The deposits consist
of 25–50 nm nanoparticle assembled films but ablation in the visible results in larger aggregates (150 nm) over imposed on
the film surface. The aggregate free films grown at 266 nm on heated substrates are thicker than those grown at room temperature
and in the former case they reveal a crystalline structure congruent with that of the initial target material. The observed
trends are discussed in reference to the light absorption step, the plasma composition and the nucleation processes occurring
on the substrate. 相似文献
20.
E. György I.N. Mihailescu P. Serra A. Pérez del Pino J.L. Morenza 《Applied Physics A: Materials Science & Processing》2002,74(6):755-759
We report micrometre-sized crown-like structure growth on a Ti surface by multipulse Nd:YAG (λ=1.064 μm,τ=170 ns) laser irradiation
in air at atmospheric pressure. The irradiation was performed at 8×107 W/cm2 laser-pulse intensity, below the ablation threshold. A ring-shape structure develops in the centre of the irradiation spot
after the action of five laser pulses. The further increase of the laser-pulse number leads gradually to a crown-like structure,
which has, for 150 pulses, a height of 120–140 μm above the non-irradiated Ti surface. The forming crater’s depth does not
exceed the height of the grown structure. In the neighbouring zone, after the action of 25 laser pulses, microcracks of the
oxide surface layer develop. With the next pulses this leads to the formation of a surface microrelief. The crown-like-structure
growth is originated by molten material movement attributed to the laser-induced plasma-recoil pressure.
Received: 6 June 2001 / Accepted: 6 January 2002 / Published online: 26 March 2002 相似文献