共查询到20条相似文献,搜索用时 15 毫秒
1.
V. V. Azharonok I. I. Filatova V. D. Shimanovich L. N. Orlov 《Journal of Applied Spectroscopy》2001,68(5):831-837
Using methods of emission spectroscopy, we have determined the gaskinetic temperature fields of planar highfrequency capacitive discharge plasma in N2/CO2/He gas mixtures depending on the excitation frequency, discharge current, pressure, and chemical composition of the mixture. It is shown that the dominant contribution to the neutral component heating in the center of the discharge chamber is made by the processes of V–T relaxation of vibrationally excited molecules N2(X
1, V) and CO2(X
1, V), whereas in the zones near the electrodes an important role in the heating is played, along with the V–T relaxation of the N2(X
1, V) and CO2(X
1, V) molecules, by the processes of deactivation of the metastable states A
3 of the N2 molecule. 相似文献
2.
A. V. Filippov I. N. Derbenev N. A. Dyatko S. A. Kurkin G. B. Lopantseva A. F. Pal’ A. N. Starostin 《Journal of Experimental and Theoretical Physics》2017,125(2):246-267
A kinetic model is proposed for ion–molecular processes involving charged particles of a humid air plasma produced by a fast electron beam. The model includes more than 600 processes involving electrons and 41 positive and 14 negative ions, including hydrated ions H3O+ (H2O) n and O 2 ? (H2O) n with n = 1, 2, …, 12. The energy costs of production of electron–ion pairs and electronic and vibrational (for water molecules, also rotational) excitation of molecules are calculated in nitrogen, oxygen, water vapor, air, and humid air. A method is proposed for calculating the energy costs in mixtures by the calculation data in pure gases. The evolution of the plasma composition is studied by the numerical solution of a system of 56 time-dependent balance equations for the number of charged particles of plasma by the fourth-order Runge–Kutta method. The steady-state composition of plasma is determined by solving nonlinear steady-state balance equations for the ionization rates of humid air from 10 to 1016 cm–3/s and the fraction of water molecules from 10–3% to 1.5%. It is established that, for water vapor content (the ratio of the number density of water molecules to the total number density of air molecules) of 0.015–1.5% in air at atmospheric pressure and room temperature, the main ion species are two types of positive ions H3O+ (H2O) n with the number of water molecules n = 5, 6 and three species of negative ions O 2 ? (H2O) n with n = 5, 8, 9. 相似文献
3.
The relative populations of the first through sixth vibrational levels are determined for the nitrogen molecule B3g state in a glow discharge. Deviation from Boltzmann's law is observed for distribution of the molecules over the vibrational levels for the B3g state.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 64–68, February, 1972. 相似文献
4.
A decaying weakly ionized helium plasma [ne=(0.2–1.1)·1011 cm–3, p=(40–70) mm Hg] was studied experimentally. It is shown that the experimental time dependences of the intensities of atomic lines and molecular bands in the afterglow phase can be explained if the vibrational kinetics of He2
+ ions is included in the analysis. Analysis of the measurements shows that for ne 1011 cm–3 and Na 1018 cm–3 deexcitation of He2
+ ions occurs primarily as a result of inelastic collisions with helium atoms. Based on the experimental data, an approximate value was obtained for the rate constants of the vibrational relaxation of molecular helium ions 10–16 cm3/sec. These results are used for making a qualitative analysis of the distribution of He2
+ ions over the vibrational states in the discharge phase.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 88–96, November, 1986. 相似文献
5.
The intensity of the first negative system ofN 2 + (B 2 Σ u + -X 2 Σ g + and of the second positive system ofN 2(C 3 Π u -B 3 Π g ) was observed in the discharge and in the afterglow as function of discharge current. An a. c. discharge in pure nitrogen was used at pressures of about 5 torr. The intensity of the first negative system ofN 2 + — in the discharge and in the afterglow — rises to a maximum and decreases with further increase of the discharge current. The afterglow intensity of the second positive system ofN 2 shows a maximum too. In the discharge, however, the intensity of the second positive system ofN 2 increases with increasing discharge current. The relative population of the vibrational levelsN v′ =i/N v′ =0 (i=1,2,3,4) of theB 2 Σ u + state ofN 2 + , in the discharge and in the afterglow, increases with increasing discharge current, while the relative population of the vibrational levelsN v′ =i/N v′ =0 (i=1, 2, 3, 4) of theC 3 Π u state ofN 2 reaches a maximum in the discharge. There seems to be evidence that the first negative system ofN 2 + is not excited by electron impact withN 2 molecules in ground state under the discharge conditions in question. 相似文献
6.
The dependence of the intensities of atomic lines and molecular bands emitted in the afterglow of a helium discharge on the electron temperature is used to identify the processes in which states of He and He
2
*
are populated. It is established that the formation of He* atoms (n = 3, 4) in decaying helium plasma occurs principally on account of the associative recombination of vibrationally excited He
2
+
ions and electrons. Analysis of the experimental reuslts leads to the conclusion that the distribution of the molecular ions He
2
+
over vibrational states is strongly nonequilibrium.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 67–72, February, 1984.It remains to thank N. P. Penkin for discussions and for his interest in the work. 相似文献
7.
Yu. Z. Ionikh N. B. Kolokolov A. V. Meshchanov N. V. Chernyshova 《Optics and Spectroscopy》2000,88(4):502-505
The electron energy distribution function in the afterglow of a low-pressure discharge in an Ar-N2 mixture was experimentally found. The values of electron temperature were determined. At the initial stage of plasma decay, the electron temperature was shown to be close to the nitrogen vibrational temperature. A study was made of the afterglow observed in the bands of the first negative system of N + 2 , and it is shown that this afterglow may be attributed to collisions of argon ions with nitrogen molecules found on higher vibrational levels. 相似文献
8.
A low-voltage xenon-hydrogen discharge is considered theoretically at an interelectrode distance of L = 1 cm and cathode emission current densities of j s = 2–20 A/cm2. Basic parameters of the discharge plasma, in particular, the total hydrogen and xenon densities, are optimized to attain the maximum possible density of negative hydrogen ions \(N_{H^ - } (L)\) at the plasma-anode boundary. The distributions of the plasma parameters over the discharge gap are calculated for optimized regimes. According to calculations, at intermediate cathode emission current densities (j s ≈ 5–10 A/cm2) in optimized discharge regimes, the density of negative hydrogen ions in the anode region of the plasma is \(N_{H^ - } (L)\) ≈ (1.5–2.5) × 1012 cm?3 and the total plasma pressure is p 0 = 0.5–0.6 Torr. 相似文献
9.
We have investigated ion desorption from adsorbed methane following keV He+ ion irradiation. The thickness of the adsorbed layer was precisely controlled. For mono-layered methane, only monomer ions (CHx+) were desorbed by 1 keV He+ ion irradiation. On the other hand, a large number of cluster ions (CnHx+) up to n = 20 were desorbed from multi-layered film. Among cluster ions, molecular ions with CC bonds were found, which indicates that chemical bonds are newly formed by ion irradiation. Based on the results for thickness dependences of the mass spectral patterns, it was elucidated that the monomer ions are desorbed from the top surface layer through single electron excitation. While the cluster ions are formed mainly in the inside of the layers along the nuclear track due to the high-density electronic excitation, which is produced by nuclear collision between incident He+ ions and frozen molecules. 相似文献
10.
On the basis of the mean value of electrical breakdown time delay and the standard deviation of electrical breakdown time delay σ dependence on the afterglow period τ, the mechanisms which dominantly influence to breakdown initiation in nitrogen were separated. It was shown that the positive ions formed in mutual collision of long‐lived metastable molecules have a dominant role in breakdown initiation for τ values up to 70 ms. The metastable molecules were derived from previous breakdown and discharge. In this case σ ≪ td and the total time delay td is approximately equal to formative time tf which decreases in value with the increase of overvoltage. When positive ions have a dominant role in the breakdown initiation the Gaussian distribution describes data of td ≈ tf very well. For τ > 1 s, N (4S) atoms formed in previous breakdown and discharge, have a dominant role in the breakdown initiation. Then, σ ≈ and Laue's distribution, which is valid for statistical time delay ts, describes td data very well (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
11.
R. E. Beverly III 《Optical and Quantum Electronics》1982,14(6):501-513
Onset of the dissociative-attachment instability requires that the rate coefficient for electron detachment (k
d) from negative ions be below a critical value. The predominant negative and positive ions in a CO2N2He gas-discharge plasma are known to change with time. As secondary by-products form and the predominant negative-ion species changes from CO
3
–
to NO
2
–
, a decrease ink
d occurs destabilizing the discharge. Since NO
2
–
and NO
3
–
are largely unreactive with respect to associative detachment,k
d depends in a sensitive fashion on the concentration of certain minority negative ions (O–, O
2
–
) and neutrals (CO, O, N). The sufficient conditions for the dissociative-attachment instability are much less sensitive to changes in the electron-ion and ion-ion recombination rate coefficients resulting from the ion aging process. 相似文献
12.
Naoaki Kumagai Nobuko Kumagai K. Tanno 《Applied Physics A: Materials Science & Processing》1989,49(1):83-89
The electrochemical characteristics and structural changes associated with discharge and charge of several tungstic acids such as H2WO4 and H2WO4 · H2O have been investigated. The suitability of these substances as new cathode materials for nonaqueous lithium batteries has been assessed. H2WO4, having only coordinated water molecules, showed a discharge capacity of about 410 Ah kg–1 of acid weight and a discharge potential around 2 V vs. Li/Li+. This capacity was much higher than the 40 180 Ah kg–1 of anhydrous WO3. H2WO4 showed a good charge-discharge cycling behavior at a capacity below 1e
–/W. However, the formation of a stable phase such as Li2WO4 during the cyclings limited the cycling number. In addition, the crystal structure of H2WO4 changed from orthorhombic to tetragonal during discharge, but the original layered lattice was kept on discharge to 1.5e
–/W. On the other hand, a significant decrease in the layer spacing of H2WO4 · H2O took place with discharge, due to the direct interaction between the interlayer water molecule and the lithium inserted between the layers. In this paper, in particular, the effect of the coordinated and hydrated water molecules in the acid structure on the electrochemical behavior is discussed. 相似文献
13.
The method similar to that of determining the asymmetric componentf
1 of electron distribution function was used to prove whether the nitrogen ions produced in discharge may be the very particles which directly influence magnesium nitridation in glow discharge. The amounts of created magnesium nitride on surfaces facing the anode and the cathode, and positive ion current to the plane double-probe were measured. It follows from experimental results that positive ions from bulk plasma are not decisive for nitride formation.The authors would like to thank Dr. V.Krejí and Dr. K.Maek for helpful discussions and critical notices. 相似文献
14.
Emil Baust 《Zeitschrift für Physik A Hadrons and Nuclei》1967,199(2):187-206
The attachment of radioactive atoms and ions to spherical aerosol particles has been studied theoretically. For uncharged atoms the deposition is considered to be solely governed by thermal diffusion. With calculations based on the “limiting-sphere”-method ofArendt-Kallman it is found, that the attached activity is proportional toΦ 2 for aerosol particle diametersΦ smaller than 0.1 μm, and proportional toΦ forΦ greater than 1 μm. For charged ions the diffusion process is modified by the influence of electrostatic forces between the diffusing ions and the aerosol particles. In the frequently occurring case of a symmetrically bipolar charged aerosol this influence can be expressed by a functionG p(Φ), which depends on the diameterΦ and the effective numberp of elementary charges on the aerosol particle. For an aerosol particle diameterΦ greater than 0.1 μm the attached activity is proportional toΦ 1.1, and forΦ smaller than 0.01 μm it is proportional toΦ 1.55. The effects of neglecting various terms in the calculation are considered. The distribution of natural radioactivity on atmospheric aerosols has been calculated for various particle size distributions according toJunge. The calculation shows that about 90% of the total natural activity should be attached to particles smaller thanΦ=0.5 μm, and about 35% to particles smaller thanΦ=0.1 μm. The time T1/2, in which the concentration of the radioactive particles decreases to half the initial value, depends on the concentration of the aerosol particles and on their size distribution. For 104 aerosol particles per cm3 and the size distributions mentioned,T 1/2 varies between 15 and 30 seconds for radioactive ions. For radioactive atomsT 1/2 is greater than it is for ions in the range of aerosol particle diameters belowΦ=0.25 μm, and smaller ifΦ greater than 0.25 μm. 相似文献
15.
C. Werner 《Optical and Quantum Electronics》1972,4(2):125-132
Hänel and Frankenberger have related the extinction coefficient and standard visibility to the relative humidity. It has been assumed that these relations also apply to the backscatter coefficient. Lidar measurements of atmospheric backscatter have confirmed that the assumption is reasonable and provide a means of distinguishing between air masses with different aerosol contents.Notation
k
extinction coefficient of sample
-
V
k
volume of sample
-
N
k
number of particles in sample
-
r
j
equivalent radius of particle
-
K
j
extinction efficiency factor for particle
-
r
k
characteristic radius of particle in sample
-
K
k
characteristic extinction efficiency factor
-
S
k
total extinction efficiency factor
-
f
relative humidity
-
solid angle
-
k()
scattering coefficient at angle
-
j
*
scattering phase shift parameter of particle
-
m
j
complex refractive index of particle
-
wavelength
-
Q
ratio of particle cross-section areas [4]
-
exponent in Kasten's relation
-
R
ratio of backscatter coefficients 相似文献
16.
17.
We spectroscopically studied the population of the excited hydrogen atomic states with the principal quantum numbers n=3 and 4 in a decaying plasma produced by a pulsed discharge in a mixture of helium (p=40.4 Torr) with a small amount of hydrogen ([H2]≈1012 cm?3). Experiments on recording the response of the spectral line intensities to a short-duration electron temperature perturbation revealed the contribution of electron-ion recombination to the population of the H*(n=3) states in the early afterglow. The ions produced by collisions of hydrogen molecules with metastable He(23 S 1) atoms, whose density decreases relatively rapidly with time in the decaying plasma, were assumed to be involved in this process. No population of the H*(n=4) atomic levels due to electron-ion recombination was found. Our experimental results are consistent with the conclusions of previous studies that excitation transfer during collisions of metastable helium molecules with hydrogen molecules plays a major role in the population of the excited hydrogen atomic states both with n=3 and with n=4 during most of the afterglow. 相似文献
18.
H. J. Kaiser E. Heinicke H. Baumann K. Bethge 《Zeitschrift für Physik A Hadrons and Nuclei》1971,243(1):46-59
The production of positive and negative ions of all elements of the sub-groupsA and some of the sub-groupsB has been investigated as an extension of previous work on Penning sources. Molecular ions of the typeX n ± ,n>1 and ions of hydride moleculesX nH m ± ,n,m>1 have been found. The maximum numberm max of the H atoms bound in the cluster is determined by the position of the element in the periodic system. The yield of the atomic and molecular beams has been measured as a function of the electric source parameters and the different gases maintaining the discharge to establish the production mechanism. The data on ion beam intensities and the state of clustering of molecules are listed in tables. 相似文献
19.
The center of traceX
CT
i
of the energy-momentum tensor of a spinning particle in General Relativity is defined. It is shown to be an invariant point of the particle, and its path is shown to be what is specified by the original side condition of Mathisson,S
u
=0. 相似文献
20.
F. Stienkemeier J. Higgins W. E. Ernst G. Scoles 《Zeitschrift für Physik B Condensed Matter》1995,98(3):413-416
Large helium clusters, ranging in size from a few hundred to several thousand atoms, are produced in a nozzle expansion. Combining this source with a pick-up scattering cell in which the clusters can be seeded with chromophores allows us to probe the influence of the helium environment on the atoms and molecules attached to the clusters. Using an alkali as chromophore we recorded laser induced fluorescence spectra of Na atoms and molecules attached to helium clusters. Apart from the spectrum of the Na monomer, we have found spectroscopic bands which can unambiguous be assigned to two bound Na atoms. The first of this bands is due to 11
+
(A) 11
g
+
(X) excitations of the covalently bound singlet Na2 molecule while the second is due to 13
g
+
13
+
excitations for the van der Waals bound triplet Na2 dimer. Both bands have been vibrationally resolved. Furthermore we found very large fluorescence intensities in the region 605–635 nm which are likely due to the excitation of a species containing three Na atoms attached to a helium cluster. 相似文献