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1.
A simple model, allowing to determine the electron temperature in a steady-state low-pressure plasma, is proposed. The model makes use of optical cross-sections and therefore takes into account direct and cascade excitation from ground and metastable states. Spectroscopic data from Mitic et al. (New J. Phys. 11, 083020 (2009)) are used to illustrate the performance of the method. 相似文献
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Novel infrared differential optical absorption spectroscopy remote sensing system to measure carbon dioxide emission
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《中国物理 B》2019,(1)
A CO_2 infrared remote sensing system based on the algorithm of weighting function modified differential optical absorption spectroscopy(WFM-DOAS) is developed for measuring CO_2 emissions from pollution sources. The system is composed of a spectrometer with band from 900 nm to 1700 nm, a telescope with a field of view of 1.12?, a silica optical fiber, an automatic position adjuster, and the data acquisition and processing module. The performance is discussed,including the electronic noise of the charge-coupled device(CCD), the spectral shift, and detection limits. The resolution of the spectrometer is 0.4 nm, the detection limit is 8.5 × 10~(20)molecules·cm~(-2), and the relative retrieval error is 1.5%.On May 26, 2018, a field experiment was performed to measure CO_2 emissions from the Feng-tai power plant, and a twodimensional distribution of CO_2 from the plume was obtained. The retrieved differential slant column densities(dSCDs)of CO_2 are around 2 × 10~(21) molecules·cm~(-2) in the unpolluted areas, 5.5 × 10~(21)molecules·cm~(-2) in the plume locations most strongly affected by local CO_2 emissions, and the fitting error is less than 2 × 10~(20)molecules·cm~(-2), which proves that the infrared remote sensing system has the characteristics of fast response and high precision, suitable for measuring CO_2 emission from the sources. 相似文献
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G. O’Connell I. Tobin J. G. Lunney 《Applied Physics A: Materials Science & Processing》2013,110(3):731-734
This paper describes the results of an experimental and theoretical investigation of the physical origin of the visible continuum emission usually observed in the early stages of nanosecond laser ablation of solid materials. It has been suggested, but not confirmed that the continuum is due to radiative recombination and bremsstrahlung emission. Time and space-resolved emission spectroscopy with an absolutely calibrated spectrometer was used to study the spectral emission in laser ablation of zinc in vacuum at 4.1 J?cm?2 using a 8 ns, 1064 nm laser pulse. By modelling the spectral emission with a spectral synthesis code, it has been shown that the continuum emission is primarily due to bound-bound transitions between strongly Stark broadened energy levels. Similarly, it can be concluded that the optical absorption is primarily due to bound-bound transitions. 相似文献
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Takashi Kajiwara Takashi Nishiyama Sachi Morinaga Kunihito Nagayama 《Applied Physics A: Materials Science & Processing》2010,101(4):739-742
We carried out the thin film deposition of iron silicide by pulsed laser ablation (PLA) on a sapphire substrate, which was
placed on a high-speed rotating titanium disk. The deposited thin film exhibited a continuous composition gradient. We investigated
how the continuous composition gradient was attained, because the strength of the gravity field in our experiment was far
below that in the experiment on bulk crystalline compounds. In the present study, we obtain the spatial distribution of several
species in the PLA plume of FeSi2 by using an intensified charge-coupled device (ICCD) camera. 相似文献
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A. A. Ilyin E. B. Sokolova S. S. Golik O. A. Bukin K. A. Shmirko 《Journal of Applied Spectroscopy》2012,78(6):861-866
The spectral and temporal characteristics of plasmas produced by femtosecond laser pulses acting on seawater surfaces are
studied. The time dependence of the decay in the intensities of emission lines and the continuum are determined and the electron
density is estimated using the three-body recombination time. It is shown that an atomic line with a low excitation potential
is the most sensitive for femtosecond laser induced breakdown spectroscopy. 相似文献
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The spatial and temporal behavior of the tantalum plasma produced in air by third harmonic Nd:YAG laser (0.6 GW cm−2) has been studied using optical emission spectroscopy. Excitation temperature and electron density have been estimated from the analysis of spectral data as well as their spatio-temporal evolutions. As the delay time increases from 400 to 2000 ns, the excitation temperature has found to decrease from 10,000 K to 7900 K. The value of Ne decreases continuously from 4 × 1018 near the zero position to 5 × 1017 in a linear approach along with the propagation axe of the plasma plume. Laser-supported consumption wave regime has been proposed to explain the propagation of the plasma. 相似文献
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Phonon sideband optical spectroscopy determines the energy of the dark K-momentum exciton for (6,5) carbon nanotubes. One-phonon sidebands appear in absorption and emission, split by two zone-boundary (K-point) phonons. Their average energy locates the E11 K-momentum exciton 36 meV above the E11 bright level, higher than available theoretical estimates. A model for exciton-phonon coupling shows the absorbance sideband depends sensitively on the K-momentum exciton effective mass and has minimal contributions from zone-center phonons, which dominate the Raman spectra of carbon nanotubes. 相似文献
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G. Koren 《Applied physics. B, Lasers and optics》1988,46(2):147-149
The infrared emission spectrum of the plume produced by KrF excimer laser ablation of polyimide films in air and in He was measured in the 680 to 1580 cm–1 wavenumber range. Using 400 mJ/cm2 laser pulses of 248 nm and 35 ns duration yielded a strong emission band characteristic of thev
2 transitions of hot HCN molecules. Band counters calculations were carried out of thev
2 emission expected from HCN in thermal equilibrium at various temperatures. They indicate that except for a slight deviation of the measured data from thermal equilibrium, the best fit of the observed results is obtained at a plume temperature of 2250±150K. 相似文献
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C. Snchez Ak H. Sobral M. Villagrn Muniz L. Escobar-Alarcn E. Camps 《Optics and Lasers in Engineering》2003,39(5-6):581-588
Laser probe beam and multiple-pass deflection techniques were used for real time and in situ monitoring of laser ablation plasma plumes in the mTorr pressure regime. Intensity and transit time of shock wave fronts were studied as functions of focal lens position, laser energy and pressure. The velocity of the shock wave was determined to be up to 30 km s−1 for a pressure of 40 mTorr and to drop below 4 km s−1 at 1 Torr. For transparent targets rear-side shock wave velocity was on to be slower than the corresponding front one. This method promises a reliable diagnostic tool for pulsed laser deposition processing allowing an increase in the quality of coating technologies. 相似文献
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We present results of wavelength-dependent ultra-fast pump–probe experiments on micelle-suspended single-walled carbon nanotubes. The linear absorption and photoluminescence spectra of the samples show a number of chirality-dependent peaks and, consequently, the pump–probe results sensitively depend on the wavelength. In the wavelength range corresponding to the second van Hove singularities (VHSs) we observe subpicosecond decays, as has been seen in previous pump–probe studies. We ascribe these ultra-fast decays to intraband carrier relaxation. On the other hand, in the wavelength range corresponding to the first VHSs, we observe two distinct regimes in ultra-fast carrier relaxation: fast (0.3–1.2 ps) and slow (5–20 ps). The slow component, which has not been observed previously, is resonantly enhanced whenever the pump photon energy resonates with an interband absorption peak, and we attribute it to interband carrier recombination. Finally, the slow component is dependent on the pH of the solution, which suggests an important role played by H+ ions surrounding the nanotubes. PACS 78.47.+p; 78.67.Ch; 73.22.-f 相似文献
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L. Torrisi 《辐射效应与固体损伤》2013,168(3):347-356
A pulsed infrared laser (Q-switched Nd:Yag) is employed to irradiate different metal targets having atomic number from Z =13 up to Z =82. The high laser fluence deposited on the metals, of the order of 100 v J/cm, produces high ablation yield and a plasma generation at the target surface. The emitted species are neutral and ionized atoms. Both components have been investigated in terms of yield emission, time-of-flight measurements and angular distribution. Results indicate that the main emission occurs mainly along the normal to the target surface, that the etching, at high fluence, is of the order of 10 v atoms/ pulse, that the atoms velocities are of the order of 10 v m/s, that the maximum ion energies are of the order of keV. During the laser irradiation, expanding and non-equilibrium plasma is produced in front of the target. The plasma has a fraction ionization depending by the metal species and generally within 10% and 80%. The plasma'temperature, at high fluence, can be theoretically calculated and reaches about 10 v K. The fractional ionization of the plasma, experimentally measured, has been investigated as a function of the laser fluence and of the energy binding of the target molecules. The ion emission yield is presented and discussed in view of the possibility to realize a laser ion source for ion accelerators. 相似文献
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Optical emission spectroscopy (OES) is used as the main experimental tool for comparison with simulations of the plasma and gas phase composition during plasma-enhanced hot filament catalytic chemical vapor deposition (PE HF CCVD) growth of carbon nanotubes (CNTs). Calculated concentration of more than 45 species in model of the CVD reactor is acquired by Chemkin™ software. Study of different conditions is performed and a close relationship can be found between the nature and the growth rate of carbon nanostructures and the concentration of the active gas phase species. Moreover it is shown that significant changes in the density and morphology of the CNTs grown in the presence of NH3 could be mainly explained by the gas phase formation of CN and HCN. 相似文献
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H. S. Desarkar P. Kumbhakar A. K. Mitra 《Applied Physics A: Materials Science & Processing》2012,108(1):81-89
Gold nanoparticles of average size varying between 1.1 and 3.3?nm are prepared by 1064?nm Nd:YAG laser ablation of solid gold target kept in ethylene glycol medium. The measured UV-Visible absorption spectra showed the presence of sharp absorption peaks in the UV and in the visible regions due to the interband transition and surface plasmon resonance (SPR) oscillations in Au nanoparticles, respectively. The increase in linewidth of the SPR peaks with the reduction in particle sizes is observed due to intrinsic size effects. The prepared samples exhibit photoluminescence (PL) emissions in the UV-Visible region peaked at ??354?nm due to the recombination of electrons with holes from sp conduction band to d-band of Au. The peak PL intensity in the sample prepared with 60 minutes of laser ablation time is enhanced by a factor of ??2.5 compared to that obtained in the sample prepared with a laser-ablation time duration of 15 minutes. 相似文献
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S. Suzuki H. Yamaguchi T. Ishigaki R. Sen H. Kataura W. Krätschmer Y. Achiba 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,16(1):369-372
Time evolution of emission by carbon nanoparticles generated with a laser furnace technique was investigated with a high-speed
video camera. Assuming blackbody radiation formula for small spherical particle, the internal temperature of these carbon
nanoparticles was determined as a function of time delay (Δt) after laser vaporization. It was found that the internal temperature of them drastically decreased at Δt < 400μs through collision with the surrounding rare gas inside the furnace. On the other hand, in particular laser vaporization
condition where yields of C60 and other higher fullerenes in the soot were found to be high, an increase in the blackbody emission intensity could be recognized
for longer wavelength ( 660 < λ < 830 nm) at Δt > 400μs. This finding suggests that a certain exothermic process related to the formation of C60 and other higher fullerenes should occur at Δt > 400μs inside the furnace. 相似文献
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The optical emission spectra(atomic hydrogen(Hα,Hβ,Hγ),atomic carbon C(2p3s→2p2:λ=165.7 nm) and radical CH(A2△→X2П:λ=420-440 nm))in the gas phase process of the diamond film growth from a gas mixture of CH4 and H2 by the technology of electron-assisted chemical vapor deposition (EACVD)have been investigated by using Monte Carlo simulation.The results show that the growth rate may be enhanced by the substrate bias due to the increase of atomic hydrogen concentration and the mean temperature of electrons.And a method of determining the mean temperature of electrons in the plasma in-situ iS given.The strong dependence on substrate temperature of the quality of diamond film mainly attributes to the change of gas phase process near the substrate surface. 相似文献
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Q.L. Zhang J.P. Zhang C.Y. Liang B.T. Li X. Li Q.L. Guo G.S. Fu 《Applied Surface Science》2009,255(17):7669-7671
An experimental investigation of the effect of different thickness of carbon layer coated on ferroelectric films on the atomic emission intensity using laser-induced plasmas spectroscopy technique with charge-coupled device (CCD) experimental system has been conducted. The experimental results show that the intensity of the spectra emitted with the carbon layer thickness of 15 μm is much higher than that of pure ferroelectric films. By using this best experimental condition, the atomic concentration ratios of ferroelectric films are evaluated by rationing the integrated intensities of selected spectral emission lines of the plasma produced from the films. And the experimental results show that NLa/NCo and NSr/NCo atomic concentration ratios are almost in agreement with the corresponding values obtained by traditional compositional analysis techniques of inductively coupled plasma (ICP). 相似文献
20.
Time resolved second harmonic spectra from glass microballoons irradiated by neodymium laser pulses (∽ 1016W cm-2, ∽ 100 ps) have been recorded with a resolution of ∽ 10 ps in time, ∽ 1 Å in wavelength and ∽ 10μm in the target plane. Intense, time and wavelength resolution-limited spots appear, whose origin has not yet been explained. 相似文献