Long-range potentials and stark broadening of neutral lines

The influence of the dipole polarization and quadrupole potentials on the Stark broadening of isolated neutral lines in a plasma has been investigated within the semiclassical approximation. It has been shown that both the perturbing electron trajectories and the minimum impact parameter may undergo a noticeable change when reaction of the emitter on the impact electron is taken into account. The effects on the halfwidths of selected lines have been examined within the impact approximation. Calculated results are compared both with available experimental data and other theoretical results. The importance of including long-range effects is also discussed.     

On the stark broadening of ionized nitrogen lines

In this paper, we report an analysis of the experimental procedure and results obtained in a recently published paper on the Stark broadening of singly-, doubly-, and triply-ionized nitrogen lines. The results of this analysis indicate that the influence of self-absorption on the line profiles is not taken into account properly and that therefore the results of Ref. 6 cannot be applied with confidence. Comparisons of experimental results with numerous theoretical calculations have also been performed.     

An analysis of Markovian model microfield methods for stark broadening

Stark broadening theories which concentrate on the statistics of the plasma electric microfield rather than the dynamics of collisions have come to be known as Model Microfield Methods. In the present paper we present an analysis of Stark broadening problems based on Markovian model microfield statistics. Our derivation permits an easy comparison with traditional Stark broadening theories such as the impact and unified theories; this comparison is used to clarify the physical nature of the approximations employed by Markovian models. The strengths and weaknesses of various models are discussed, emphasizing the kangaroo process of Brissaud and Frisch, and methods are suggested for improving the current model microfield approach.     

Impact and quasistatic limit in the quantum-path theory of pressure broadening

The quantum-path theory of collision broadening involves a correlation function which can be calculated by infinite-order perturbation theory. From the expression obtained, both the impact and the quasistatic limit are easily derived. Application of the WKB method is discussed for the impact result.     

Experimental study of stark broadening of nitrogen ion lines in a theta pinch plasma

We have studied the Stark broadening of the 3s-3p, 3p-3d and 3d-4f emission lines of the nitrogen II, III, and IV ions emitted from a hot plasma. The plasma was created by a 60 kJ, 60 kV single turn coil theta pinch, where the fill gas was 3 torr of (49%He+51%N₂). The plasma was diagnosed by measuring the Stark-broadened profile of the He(II) 4686 Å line and by taking shadowgrams of the plasma development. It was found that the ionization stage distribution and thus the electron density departed from that predicted by Saha-Boltzmann equilibrium relations. The analysis of the plasma parameters gave an electron density of 1.4 x 10¹⁸ cm^-3. The electron temperature was measured from the relative intensities of emission lines as well as from the line-to-continuum ratio and was found to be 5.0 eV. The line profiles have been fitted to Lorentzian profiles and the thus measure line widths are compared with earlier experimental data as well as with simple theoretical calculations. We find that our line widths are broader than earlier data taken at lower densities if we assume a linear scaling of the half width with the density. A simple Lorentzian profile fits in most cases quite well to the observed line profile. The simple calculations can predict the linewidths within 20% for the low lying levels of both the singly and doubly ionized nitrogen while the predictions are far too narrow for the higher lying levels from the multiply ionized atoms.     

Observations of stark broadening of resonance lines in a beryllium,laser produced plasma

The resonance lines of Be IV are Stark-broadened in a laser produced plasma. The distribution of the electron density is derived by a measurement of the line profiles and comparison with theory. Density values up to 10²¹ cm^-3 have been found near the target.     

Electron density from time resolved stark profiles in ablation plasmas

A time-resolving X-ray crystal spectrograph is used to study the emission of high lying Lyman states in order to determine the electron density in a laser target plasma. The results are analyzed for a number of experiments and the sensitivity of the technique is shown. The ability of the diagnostic procedure to yield accurate densities is compared with the usual time-integrated diagnostic procedures.     

Electron impact broadening of NaI,multiplet 9, spectral lines

We present calculations of the electron impact broadening of NaI, multiplet 9, spectral lines in an attempt to resolve the discrepancy between recent experimental results and theoretical estimates.     

On the stark broadening of isolated lines of F(II) and Cl(III) by plasmas

Recent measurements of Stark widths of isolated lines emitted by singly-ionized fluorine atoms and doubly-ionized chlorine atoms are compared with the corresponding values calculated by the semiempirical impact approximation of Griem. A discussion is given of some of the difficulties which arise particularly when this method is applied to lines from multiply charged ions. On the basis of these comparisons, some new values are proposed for the threshold Gaunt factors of the ions under consideration, and these are compared with values deduced earlier for a number of other ions. Some systematic trends are observed.     

On quasistatic processes

The idea of a quasistatic process is analyzed. The problem of the applicability of the axiom of adiabatic inaccessibility and other propositions of the second law of thermodynamics to quasistatic processes is discussed. Moscow State Extra-Mural Institute of the Food Industry. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 6, pp. 56–60, June, 1997.     

Electron impact broadening of Si IV spectral lines: Comparison with recent experiments

Electron impact widths of eight Si IV spectral lines have been calculated using our quantum mechanical method. Semiclassical perturbation calculations using atomic data from the SUPERSTRUCTURE code have been also performed. Comparison with recent measurements shows that they are always lower than our quantum mechanical, semiclassical perturbation and all other theoretical results. A disagreement in the importance of fine structure effects between our results and the measured ones has been reported here.     

An adiabatic theorem applicable to the stark effect

We prove an adiabatic theorem applicable to an atom evolving in a slowly varying electric field. This yields an operational estimate of the tunneling rate even for systems where complex scaling techniques are not applicable.     

Projection operator approach to the resonant stark effect

An application of the projection operator technique to the spontaneous emission process of an atom dressed by a strong nearly resonant e.m. field is presented. In the one-photon emission limit, the transition probability is evaluated at all orders.     

Measurement of stark broadened Lyman-lines

Stark broadened profiles of the hydrogen Lyman-lines Ly-α to Ly-? have been measured in a wall-stabilized argon arc, providing a plasma of an electron density of 7·2 X 10¹⁶ cm^-3 and a temperature of 12,200 K. In the cases of Ly-α and Ly-β, detailed investigations of the profiles are performed including absolute measurements, measurements of line shifts and asymmetries and comparisons with modern theories. Moreover, a comprehensive discussion of experimental errors is given and some important features of the radiation source are outlined.     

CIV共振谱线的电子碰撞展宽的理论计算

 使用R-矩阵方法,利用碰撞近似和密耦理论,计算了确定CIV 2s²S-2p²P⁰共振谱线的碰撞参数,并由此得到了在电子密度为10¹⁷cm^-3 的条件下,共振谱线的线宽和线移随温度的变化关系。计算得到的线宽与半经典的理论计算值符合得比较好,但大约只有实验线宽的一半。     

Die Sprungtemperatur stark koppelnder Supraleiter

We investigate the general structure of the equation for the critical temperature of superconductors, introduced in an earlier work. An expression for the Coulomb pseudopotential allowing a better calculation is found without any cut-off procedure. Using an Einstein type phonon spectrum we give an explicit formula forT _c , which in case of strong coupling superconductors differs from McMillan's expression. The agreement with experimental values is good.