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1.
N. Srivastava C. Wang T. S. Dibble 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(1):77-86
Simultaneous measurements of absolute concentrations of H2O and OH
radicals in an atmospheric AC discharge using continuous wave cavity
ringdown spectroscopy (cw-CRDS) are reported. Formation of OH radicals and
plasma temperatures are characterized by optical emission spectroscopy. The
concentration of OH radical at the edge of the discharge plume at 380 K is
measured by the cw-CRDS technique to be 1.1 ×1015 molecule
cm-3. Ringdown measurements of the H2O (120-000) band and the OH
first overtone around 1515 nm enable us to determine an OH generation yield,
, to be 4.8 ×10-3, where
NOH and are the number densities of OH and H2O,
respectively. The minimum detectable absorption coefficient of the
cw-CRDS system is 8.9 ×10-9 cm-1, which corresponds to a
1σ detection limit of OH number density of 1.2 ×1013 molecule cm-3 in the discharge. This experimental approach is
demonstrated for the first time ever in an AC discharge, and can be applied
in general to a variety of atmospheric plasmas to help study OH formation
mechanisms and OH-related plasma applications. 相似文献
2.
F.?Kr?ma M.??áková 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):369-375
The nitrogen pink afterglow was studied by optical emission spectroscopy in the DC flowing regime at a total gas pressure
of 700 Pa and at the discharge current of 120 mA. The discharge was created in a Pyrex tube of 13 mm i.d. using nitrogen and
argon of 99.999% purity with additional purification by Oxiclear columns and liquid nitrogen traps. The area ±3 cm around
the observation point had to be cooled down to liquid nitrogen wall temperature in order to allow the study of the reactor
wall temperature effect on the post-discharge. The maximum pink afterglow emission in pure nitrogen at ambient wall temperature
was observed at a decay time of 6 ms. When the argon percentage in the gas mixture was increased the pink emission maximum
was shifted to the later decay times. Simultaneously, the intensity of the pink afterglow decreased and at a 1:1 nitrogen-argon
ratio the effect disappeared. Similar effects were also observed when the discharge tube wall around the observation point
was cooled down to liquid nitrogen temperature. The argon atomic lines were only observed during the post-discharge at the
highest argon concentration at a low wall temperature. The kinetic model showed that the pink afterglow quenching was connected
to the decrease of the and pooling processes efficiency. 相似文献
3.
L. Torrisi A. Borrielli D. Margarone F. Caridi A. M. Mezzasalma 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):343-348
A pulsed Nd:Yag laser, at intensities of the order of 1010 W/cm2, is employed to irradiate different thick metallic targets (Ti, Fe, Ag, and Ni) placed in vacuum. The obtained non-equilibrium
plasmas are investigated with various analytical techniques. An electrostatic ion energy analyzer and different ion collectors
are employed to monitor in situ the ions ejected from the plasma and to determine the core plasma temperature, the ion energy
distributions and the ion angular emission. An optical spectrometer is employed to analyze the plasma corona emitted light
vs. wavelength and to identify the emitted characteristic lines. The optical spectroscopy permitted to evaluate the electron
temperatures and densities. Results show strong temperature and density gradients occurring in the laser-generated plasma
plume. 相似文献
4.
A. Lorusso J. Krása L. Láska V. Nassisi L. Velardi 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):473-476
In the last years the ion component of a laser-produced plasma has been considered and studied as an object to provide high-density
ion sources, which can be applied in many fields such as laser-induced implantation. In this work a KrF laser beam of 108 W/cm2 irradiance was focused onto single-crystalline Fe and single-crystalline Fe with 2% of Si targets and the characteristics
of both free expanding laser-produced plasmas were compared. The time-of-flight (TOF) method was applied to determine the
ion charge yield at various laser fluences and the ion angular spread. The analyses of TOF spectra showed a synergetic effect
of the silicon admixture in target material on the Fe ions production. Besides, this admixture was also responsible of the
increasing of the plasma temperature which corresponds in turn to the increasing of the average kinetic energy of the particles
as well as of the more collimated ion distribution. 相似文献
5.
Spatially resolved measurements of vibrational and rotational temperature determined from the N2(C) nitrogen bands intensities have been performed by means of optical scanner of original construction. It has been found
that radial variations of studied bands are independent of pressure and discharge current under our experimental conditions,
i.e. in the pressure range (100–300) Pa and for discharge current up to 40 mA. Moreover, it has been found that vibrational
as well as rotational temperatures stay almost constant in the radial direction. No radial changes of both temperatures can
be explained by good thermal conductivity of the positive column of DC glow discharge.
This research was supported by grants: Charles University No. GAUK 194/01, Ministry of Education of Czech Republic MSM 11320002,
and Grant Agency of Czech Republic GAČR 202/03/0827. The theme of presented article was included in the EU project No. G1RT-CT-2002-05083
“Plasmatech”. 相似文献
6.
M. Kubkowska P. Gasior M. Rosinski J. Wolowski M. J. Sadowski K. Malinowski E. Skladnik-Sadowska 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):463-466
This paper describes results of spectroscopic investigation of laser-produced tungsten plasma. The laser intensity on the
target surface reached up to 30 GW/cm2 depending on the focusing conditions. Optical spectra emitted from plasma plumes which were formed under vacuum conditions
in front of the tungsten target due to the interaction of Nd-YAG laser pulses (1.06 μm, 0.5 J), were characterised by means
of an optical spectrometer (λ/Δλ= 900) in the wavelength range from 300 to 1100 nm. The spectra were recorded automatically
with the use of a CCD detector with exposition time varied from 100 ns to 50 ms. On the basis of WI and WII lines it was possible
to estimate electron temperature and electron density which corresponded to the expansion phase of the plasma. Te and Ne were measured as 1.1 eV and 8×1016 cm-3, respectively. The spectra collected by the ion energy analyser showed that the plasma included tungsten ions up to 6+ ion
charge. Signals from the ion collector allowed to estimate the average value of ion energy of tungsten as 4.6 keV. Basing
on this value the electron temperature corresponding to the initial stage of the plasma formation was estimated to be about
320 eV. Optical microscope investigation showed that laser irradiation caused structural changes on the surface of the target. 相似文献
7.
Vanja Margetic Ticijana Ban Ota Samek Franz Leis Kay Niemax Roland Hergenröder 《Czechoslovak Journal of Physics》2004,54(4):423-429
Fluorescence measurements have been used to characterize the velocity of atoms in a femtosecond-laser-produced plasma. Nanogram
amounts of a copper sample were ablated by the focused radiation (λ=775 nm) of an all-solid-state laser. The laser was operated
at a pulse rate of 10 Hz with an energy of 200μJ per pulse. The microplasma expanded into a defined argon atmosphere of pressures between 0.02 and 850 mbar. Atomic fluorescence
was excited in the laser plume by a dye-laser pulse with the wavelength set to the line Cu I 282.4 nm. The narrowed beam of
the dye-laser was directed into the plasma at different heights above the sample surface. The fluorescence radiation was measured
with an échelle-spectrometer, equipped with an intensified-charge-coupled device as the detector. The velocity depends strongly
on the pressure of the ambient atmosphere and the distance from the sample surface. The highest velocity found at an argon
pressure of 0.02 mbar was 1.0×106 cm s−1. 相似文献
8.
We describe a new technique to measure the UV/visible absorption spectrum of the ablated material during the laser pulse.
The technique utilizes the continuum emission from one laser produced plasma as a light source to measure the absorption properties
of a second laser produced plasma which is formed on a semi-transparent target with an array of 40 μm holes. A 6 ns, 1064
nm laser was used to ablate a Ag target and the plasma absorption was measured in the range 450–625 nm for a laser fluence
of 1 J cm−2. The total absorption cross-section is (0.5–1.5)×10−17 cm2 in the range 450–540 nm. By comparing the measured absorption with a calculation using the plasma spectroscopy code FLYCHK
it can be concluded that, in the wavelength region examined here, the absorption is mainly due to bound-bound transitions. 相似文献
9.
H. M. Gao S. L. Ma C. M. Xu L. Wu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,47(2):191-196
Electron densities in an atmospheric helium arc plasma have been measured with the Stark broadening parameters of helium spectral
lines. The spatially distributed radiation intensities are converted to plasma emission coefficients at every wavelength by
means of Abel inversion. From the inverted profiles of He I lines of 4713 ?, 5016 ?, and 6678 ? electron density has been
calculated, which ranges from 0.5 ×1016 to 4 ×1016 cm-3 for a helium arc with current 200 A. Stark widths of He I lines of 3889 ? and 7065 ? are determined based on the measurements
and compared with existing data. 相似文献
10.
K. Nowakowska-Langier L. Jakubowski E. O. Baronova K. Czaus M. Rabinski M. J. Jakubowski 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):377-382
This study reports the results of a pilot experiment concerning observations of extreme ultraviolet emission from plasma produced
by the capillary discharges. A few kA current was applied across the gas-filled alumina capillary (1 mm diameter and 8 mm
long) to generate radiation in the EUV region (12–63 nm). Spectroscopic studies were carried out by means of a XEUV spectrometer
which was upgraded for special lithography purposes. The results obtained from the EUV spectroscopic measurements provided
information about the radiation processes from xenon and argon plasma and testifies that given capillary is an effective source
of EUV emission. Additionally we showed a simulation which describes plasma dynamics parameters and dynamics of various ionization
stages in capillary discharge. Our computer simulation confirmed the presence of ions, which spectra was registered in the
experiment. 相似文献
11.
H. Nowakowska M. Jasiński J. Mizeraczyk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):511-518
We present results from simulations of 2D distributions of the electromagnetic field inside a waveguide-based axial-type microwave
plasma source (MPS) used for hydrogen production via methane reforming. The studies are aimed at optimization of discharge
processes and hydrogen production. We derive equations for determining electromagnetic field distributions and next determine
the electromagnetic field distributions for two cases – without and with plasma inside the MPS. For the first case, we examine
the influence of the length of the inner conductor of the coaxial line on electromagnetic field distributions. We have obtained
standing wave patterns along the coaxial line and found resonances for certain positions of the coaxial line inner conductor.
For the case with plasma inside the MPS, we perform calculations assuming that distributions of plasma parameters are known.
Simulations are done for several values of maximum electron density. We have found that for values of electron density greater
than strong skin effect in the plasma is observed. Consequently, plasma may be treated as an extension of the inner conductor
of the coaxial line. We have used FlexPDE software for the calculations. 相似文献
12.
Kuo-Sheng Kao Shang-Hao Chang Po-Tsung Hsieh Chih-Ming Wang Da-Long Cheng 《Applied Physics A: Materials Science & Processing》2009,96(2):529-533
Three-layered ZnO/Ag–Ti/ZnO structures were prepared using both the sol-gel technique and DC magnetron sputtering. This study
focuses on the electrical and optical properties of the ZnO/Ag–Ti/ZnO multilayers with various thicknesses of the Ag–Ti layer.
The ZnO thin film prepared by the sol–gel method was dried at 300°C for 3 minutes, and a fixed thickness of 20 nm was obtained.
The thickness of the Ag–Ti thin film was controlled by varying the sputtering time. The Ag–Ti layer substantially reduced
the electrical resistivity of the sol–gel-sprayed ZnO thin films. The sheet resistance of the Ag–Ti layer decreased dramatically
and then became steady beyond a sputtering time of 60 s. The sputtering time of Ag–Ti thin film deposition was determined
to be 60 s, taking into account the optical transmittance. Consequently, the transmittance of the ZnO/Ag–Ti/ZnO multilayer
films was 71% at 550 nm and 60% at 350 nm. The sheet resistance was 4.2 Ω/sq. 相似文献
13.
Yu. A. Lebedev A. V. Tatarinov I. L. Epstein 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(3):319-328
1D quasi-static self-consistent model of
nonequilibrium nitrogen and oxygen plasma with highly non-uniform spatial
distribution of the electric field strength is used for analysis of the
correlation of ionization rate profile and charged particles profiles. It is
shown that inside a region of local increase of the ionization rate the
layers with violation of quasi-neutrality can exist. This leads to the
appearance of local static electric fields. Special attention is devoted to
plasma resonance regions in microwave plasma. The role of negative ions is
also studied. 相似文献
14.
R. Vladoiu M. Contulov A. Mandes G. Musa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):287-291
The M-effect (monochromatization-effect) is a powerful tool which can give high intensity monochromatic spectra with a certain
wavelength depending on the type of used gas mixtures to generate plasma state. The effect consists in the emission of a single
spectral line of plasmas ignited in certain gas mixtures. The main condition to obtain the M effect is the presence of an
electropositive and an electronegative gas mixture. For example, in the case of Ne+H2 monochrome radiation was obtained, the wavelength of Ne being 585.3 nm (1s2–2p5). In this paper we prove the general character of this effect, i.e. if the optical emission spectra reduced to nearly one
line can be observed also in other gas mixture discharges, for example in the case of one electronegative gas and two electropositive
gases. Different other mixtures, as Xe+Ne+H2 and Xe+Ar+H2 have been studied. In all these cases, the M-effect appeared without doubt. 相似文献
15.
J. Hoffman W. Mróz A. Prokopiuk Z. Szymanski 《Applied Physics A: Materials Science & Processing》2008,92(4):921-926
The plasma plume induced during ArF laser ablation of a graphite target is studied. Velocities of the plasma expansion front
are determined by the optical time of flight method. Mass center velocities of the emitting atoms and ions are constant and
amount to 1.7×104 and 3.8×104 m s−1, respectively. Higher velocities of ions result probably from their acceleration in electrostatic field created by electron
emission prior to ion emission. The emission spectroscopy of the plasma plume is used to determine the electron densities
and temperatures at various distances from the target. The electron density is determined from the Stark broadening of the
Ca II and Ca I lines. It reaches a maximum of ∼9.5×1023 m−3 30 ns from the beginning of the laser pulse at the distance of 1.2 mm from the target and next decreases to ∼1.2×1022 m−3 at the distance of 7.6 mm from the target. The electron temperature is determined from the ratio of intensities of ionic
and atomic lines. Close to the target the electron temperature of ∼30 kK is found but it decreases quickly to 11.5 kK 4 mm
from the target. 相似文献
16.
R. Hannachi S. Boussaïdi P. Teulet G. Taieb Y. Cressault A. Gleizes Zohra Ben Lakhdar 《Applied Physics A: Materials Science & Processing》2008,92(4):933-937
A spectroscopic study of the plasma plume created by a laser beam on the surface of NaCl aqueous solution is presented. Optical
emission spectra are recorded and temporally analyzed; electron number density is determined from the Stark broadening of
the NI nitrogen line, and temperature is obtained from relative intensity of OI oxygen lines. The intensity of an atomic line
from sodium was used to quantitate its molar percentage in the Oceanic and Mediterranean sea, and calibration curves have
been constructed for concentrations ranging up to 1.5%. 相似文献
17.
E. Sterling C. Pagano J. G. Lunney 《Applied Physics A: Materials Science & Processing》2008,92(4):1031-1035
For some applications of laser produced plasma it may be advantageous to implement some degree of control on the ion flux
and velocity distribution in the plasma expansion. We have shown how a fast, high current discharge in a laser produced plasma
leads to a dramatic increase in the plasma ionization and expansion velocity. These observations are consistent with a magnetohydrodynamic
discharge model whereby the self-induced magnetic field causes radial compression of an open-ended plasma column. 相似文献
18.
Z. W. Liu X. F. Yang A. M. Zhu G. L. Zhao Y. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,48(3):365-373
The hydroxyl radical (OH) plays an important role in combustion systems,
atmospheric chemistry and the removal of air pollutants by non-thermal
plasmas. The present work reports the determination of the hydroxyl radicals
in atmospheric dielectric barrier discharge plasmas via near infrared
continuous wave cavity ring-down spectroscopy. The P-branches of OH
X2Πi (ν' = 2 ←ν′′ = 0) bands were used for its number density measurements. The minimum measurable absorption coefficient is about
3 × 10-8 cm-1 in DBD plasmas. At certain experimental
conditions (a.c. frequency of 70 kHz, 6700 ppm H2O in He, 1 atm), when
the peak-to-peak discharge voltage varied from 6 kV to 10.4 kV, the
determined OH radical concentration increased from (2.1 ± 0.1) ×
1013 molecules cm-3 to (3.7 ± 0.1) × 1013 molecules cm-3. The plasma gas temperature, derived from the Boltzmann plots of OH rotational population distributions, ranged from 312
± 10 K to 363 ± 10 K when the discharge voltage was raised in the above range.
The influences of O2 and N2 addition on the production of OH
radicals have been also investigated. 相似文献
19.
Z.-S. Liu 《Applied Physics A: Materials Science & Processing》2009,95(2):443-445
In a rare-earth antiferromagnet, two neighboring magnetic ions order spontaneously in opposite directions below the Néel temperature.
Especially when it is placed in an external magnetic field, the two magnetic ions react to the field in different ways, so
that they usually have different magnitudes and orientations below the magnetic transition temperature. Therefore, to describe
the magnetic structure of an antiferromagnet, the single-ion ferromagnetic-like model is inadequate. To solve this problem,
a two-ion model for rare-earth antiferromagnets is proposed and used in this work to investigate the magnetic properties of
DyNi2B2C. The magnetic susceptibility curves obtained with this model show good agreements with experimental data. 相似文献
20.
M. Jasiński M. Dors J. Mizeraczyk 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,54(2):179-183
In this paper, results of hydrogen production via methane pyrolysis in the atmospheric pressure microwave plasma with CH4 swirl are presented. A waveguide-based nozzleless cylinder-type microwave plasma source (MPS) was used to convert methane
into hydrogen. The plasma generation was stabilized by a CH4 swirl having a flow rate of 87.5 L min-1. The absorbed microwave power was 1.5–5 kW. The hydrogen production rate and the corresponding energy efficiency were 866 g
(H2) h-1 and 577 g (H2) kWh-1 of microwave energy absorbed by the plasma, respectively. These parameters are better than our previous results when nitrogen
was used as a swirl gas and much better than those typical for other plasma methods of hydrogen production (electron beam,
gliding arc, plasmatron). 相似文献