共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
对于高温高压下氩等离子体的电离度和物态方程,本文给出了一种基于Thomas-Feimi(TF)统计模型的简化计算新方法:首先将TF模型电离势的数值结果进行函数逼近,给出一个便于数值求解的计算电离度的近似计算方法,并由此计算了局部热动平衡下的氩等离子体在10~1000 eV高温范围内的物态方程.计算结果与国外报道的其他几种理论模型的计算结果均符合很好,与实验值也吻合较好.本文所提出的简单模型也适用于计算混合物物态方程,可以在电磁发射技术领域中的强电离等离子体中有更为广阔的应用前景. 相似文献
3.
E. A. Volkova A. M. Popov O. V. Tikhonova 《Journal of Experimental and Theoretical Physics》1998,87(5):875-884
The ionization of a simple two-electron model system, viz., the one-dimensional negative hydrogen ion, is investigated using direct numerical integration of the time-dependent Schrödinger equation. The one-and two-electron ionization probabilities as functions of frequency and radiation intensity are obtained. It is shown that two-electron ionization is mediated by both direct and sequential mechanisms. The stabilization of the two-electron system against the ionization process is investigated. The data obtained are compared with calculations performed within the one-dimensional single-particle model of H?. The photoelectron spectrum is analyzed in the region of parameters corresponding to the single-electron ionization regime. 相似文献
4.
电离能下降的现象与等离子体的成分、电离分布、热力学、输运性质息息相关,其精确测量值对于整个实验的模型检验和方案设计都至关重要.本文考虑粒子数的涨落,对经典的Stewart和Pyatt的模型进行修正,并耦合进先前发展的等离子体模型.利用修正的模型对熊刚等人的实验进行了解释,发现当前模型所得结果要优于其他理论结果,与实验更加一致. 相似文献
5.
Abstract: Mass spectrometry (MS) has become an integral tool in life sciences. The first step in MS analysis is ion formation (ionization). Many ionization methods currently exist; electrospray ionization (ESI) and matrix-assisted laser desorption ionization (MALDI) are the most commonly used. ESI relies on the formation of charged droplets releasing ions from the surface (ion evaporation model) or via complete solvent evaporation (charge residual model). MALDI ionization, however, is facilitated via laser energy and the use of a matrix. Despite wide use, ESI cannot efficiently ionize nonpolar compounds. Atmospheric pressure chemical ionization (APCI) and atmospheric pressure photo ionization (APPI) are better suited for such tasks. APPI requires photon energy and a dopant, whereas APCI is similar to chemical ionization. In 2004, ambient MS was introduced in which ionization occurs at the sample in its native form. Desorption electrospray ionization (DESI) and direct analysis in real time (DART) are the most widely used methods. In this mini-review, we provide an overview of the main ionization methods and the mechanisms of ion formation. This article is educational and intended for students/researchers who are not very familiar with MS and would like to learn the basics; it is not for MS experts. 相似文献
6.
《Journal of Electron Spectroscopy and Related Phenomena》2005,142(3):283-293
Collision-energy/electron-energy-resolved two-dimensional Penning ionization electron spectroscopy (2D-PIES) has been used to study outer characteristics of molecules. Anisotropic potential energy surfaces for collisional ionization of molecules with a metastable helium atom He*(23S) have been determined starting from ab initio model potentials via optimization based on trajectory calculations. Since ionization widths in the theoretical model of Penning ionization are functionals of target molecular orbitals, outer electron distributions of molecular orbitals can be determined via optimization procedures of calculated ionization cross-sections by trajectory calculations with respect to observed 2D-PIES data. 相似文献
7.
Multiphoton ionization and electron recombination processes are studied in argon using coherent microwave Rayleigh scattering from a localized, resonance-enhanced multiphoton ionization produced plasma. A time dependent one-dimensional plasma dynamic model is developed to predict the time evolution of the microwave scattering from the plasma. Experimental results of the argon ionization spectrum and electron recombination rates are in good agreement with the model predictions. 相似文献
8.
Two-colour coherent control of multiphoton ionization: a comparison between long-range and short-range potential model atoms
下载免费PDF全文
![点击此处可从《中国物理》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Using the numerical solution of the time-dependent Schr\"odinger
equation of a one-dimensional model atom in a two-colour laser field,
we have investigated the effects of the potential models on coherent
control of atomic multiphoton ionization. It is found that the
photoelectron spectra are obviously different for the long-range
(Coulomb-like) and short-range (with no excited bound states)
potential model atoms, which are produced by two-colour coherent
control of atomic multiphoton ionization in a few laser cycles. Our
results indicate that two-colour coherent control of atomic
multiphoton ionization can be observed in simulations, depending on
the choice of the model potentials. 相似文献
9.
10.
Quantum calculations of a (1+1)-dimensional model for double ionization in strong laser fields are used to trace the time evolution from the ground state through ionization and rescattering to the two-electron escape. The subspace of symmetric escape, a prime characteristic of nonsequential double ionization, remains accessible by a judicious choice of 1D coordinates for the electrons. The time-resolved ionization fluxes show the onset of single and double ionization, the sequence of events during the pulse, and the influences of pulse duration and reveal the relative importance of sequential and nonsequential double ionization, even when ionization takes place during the same field cycle. 相似文献
11.
12.
为了准确计算稠密等离子体电离平衡,在理想Saha 方程的基础上,加入了压致电离理论和德拜理论相结合的修正。此电离模型可以描述稠密等离子体内电离机制随着密度的增加由热电离转变为压致电离的现象。压致电离理论结合德拜理论修正的Saha 方程的计算结果与其它电离模型结果作了对比和分析。电离气体区域采用完全电离等离子体模型计算电子弛豫时间,而在凝聚态区域采用电子平均自由程计算电子弛豫时间。提出了将两个区域平滑连接起来的公式,从而建立了一种可以计算从理想等离子体态到凝聚态物质的半经验电导率模型,半经验模型计算结果与实验数据作了对比。 相似文献
13.
E. A. Volkova A. M. Popov M. A. Tikhonov O. V. Tikhonova 《Journal of Experimental and Theoretical Physics》2007,105(3):526-534
Direct numerical calculations of the single-photon ionization dynamics of the hydrogen atom were compared with the data obtained within the strong-field approximation (SFA). An analysis showed that the SFA model accurately determines the range of electromagnetic field intensities, upon reaching of which the ionization mode deviates from that described within perturbation theory; in particular, the ionization rate decreases with increasing intensity. It was demonstrated that the actual ionization mechanism under an intense pulse differs significantly from the SFA predictions. For example, an analysis of photoelectron angular distributions and energy spectra showed that the strong-field ionization features within the SFA model are primarily controlled by the ionization channel closing effect associated with the ponderomotive shift of the continuum boundary. At the same time, the results of direct numerical calculations of the ionization dynamics suggest that the Kramers-Henneberger atom is formed in a strong field, which is characterized by increased stability to strong-field ionization. 相似文献
14.
为了准确计算稠密等离子体电离平衡,在理想Saha方程的基础上,加入了压致电离理论和德拜理论相结合的修正。此电离模型可以描述稠密等离子体内电离机制随着密度的增加由热电离转变为压致电离的现象。压致电离理论结合德拜理论修正的 Saha 方程的计算结果与其它电离模型结果作了对比和分析。电离气体区域采用完全电离等离子体模型计算电子弛豫时间,而在凝聚态区域采用电子平均自由程计算电子弛豫时间。提出了将两个区域平滑连接起来的公式,从而建立了一种可以计算从理想等离子体态到凝聚态物质的半经验电导率模型,半经验模型计算结果与实验数据作了对比。 相似文献
15.
J. Davis K.G. Whitney J.P. Apruzese 《Journal of Quantitative Spectroscopy & Radiative Transfer》1978,20(4):353-370
The influence of temperature and density variations and opacity effects on the ionization dynamics of a spherical carbon plasma are determined. The calculations were done for solid, hollow and absorbing center geometries. The results of these calculations show that there are wide-spread differences in the amount and distribution of resonance line radiation emitted from the hydrogen- and helium-like ionization stages that depend on the model describing the ionization dynamics. 相似文献
16.
17.
Sequential over-barrier ionization of multi-electron atoms in the tens-to-hundreds keV/u energy range
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
Our previous work on the classical over-barrier ionization model for helium double ionization is extended to the complex multi-electron system of Ne.The total and q-fold ionization cross sections are calculated at energies ranging from a few tens to several hundred keV/u.The calculation results are in good agreement with the experimental data,and the energy dependence of the cross sections suggests that the multi-ionization of a strong perturbated complex atom is probably the sequential over-barrier ionization process. 相似文献
18.
Davis J. Clark R.W. Giuliani J.L. Jr. Thornhill J.W. Deeney C. 《IEEE transactions on plasma science. IEEE Nuclear and Plasma Sciences Society》1998,26(4):1192-1201
In this paper, we study the dynamics of a massive aluminum Z-pinch plasma load and evaluate its performance as a soft X-ray radiator. A radiation hydrodynamic model self-consistently driven by a circuit describes the dynamics. Comparisons are made for the K- and L-shell soft X-ray emission as a function of the ionization dynamic model. The ionization dynamic models are represented by: 1) a time-dependent nonequilibrium (NEQ) model, 2) a collisional radiative equilibrium (CRE) model, and 3) a local thermodynamic equilibrium (LTE) model. For all three scenarios the radiation is treated 1) in the free streaming optically thin approximation where the plasma is treated as a volume emitter and 2) in the optically thick regime where the opacity for the lines and continuum is self-consistently calculated online and the radiation is transported through the plasma. Each simulation is carried out independently to determine the sensitivity of the implosion dynamics to the ionization and radiation model, i.e., how the ionization dynamic model affects the radiative yield and emission spectra. Results are presented for the L- and K-shell radiation yields and emission spectra as a function of photon energy from 10 eV to 10 keV. Also, departure coefficients from LTE are presented for selected levels and ionization stages 相似文献
19.
A model differential equation relating the vertical ionization potentials of unexcited atoms and ions of elements is obtained; its solution establishes the relation between these quantities and the spectroscopic index of the electron expressed by an exponential. On the basis of this relation, the ionization potentials calculated in various works are compared. Using the model equation proposed here, it is possible to calculate unknown and refine known ionization potential values.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 14–17, November, 1984. 相似文献
20.
I. Baldea L. S. Cederbaum J. Schirmer 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,69(2):251-264
We report detailed results on ionization in metallic quantum-dot (QD) nanorings described by the extended Hubbard model at
half filling obtained by exact numerical diagonalization. In spite of very strong electron correlations, the ionization spectra
are astonishingly scarce. We attribute this scarcity to a hidden quasi-symmetry, generalizing thereby similar results on optical
absorption recently reported [Phys. Rev. B 75, 125323 (2007); 77, 165339 (2008)]. Numerical results indicate that this hidden quasi-symmetry of the extended Hubbard model does not evolve
into a true (hidden) symmetry but remains a quasi-symmetry in the case of the restricted Hubbard model as well. Based on the
observation on the number of significant ionization signals per each spatial symmetry, we claim the existence of a one-to-one
map between the relevant ionization signals of the correlated half-filled nanorings and the one-hole and two-hole-one-particle
processes possible in the noninteracting case. Similar to the case of optical absorption, numerous avoided crossings (anticrossings)
are present in the ionization spectra, which often involve more than two states. The present results demonstrate that ionization
could be a useful tool to study electron correlations in metallic QD-nanoarrays, providing information that is complementary
to optical absorption. 相似文献