Balazs F. Rozsnyai

An overview of the problems connected with theoretical calculations for hot plasmas

Abstract A brief description is given of the different quantum-mechanical models and approximations used in hot plasma calculations. The subject is elucidated by presentation of computed data for iron and astrophysical plasmas.

Theory and experiment for ultrahigh pressure shock Hugoniots

Abstract Several equation of state models for hot, dense matter are compared with experimental data for the shock Hugoniots of beryllium, aluminum, iron, copper, and molybdenum up to extreme pressures. The best models are in good agreement with experiment and with one another, suggesting that our understanding of dense, partially ionized matter is good.

Computation of free-free Gaunt factors and conductive opacities in hot matter

Abstract Analytic formulas are derived for the computation of free-free Gaunt factors and electron conductive opacities by approximating the self-consistent electron-ion potential with two superimposed Yukawa potentials. The method has general validity for arbitrary temperature and matter density.

Spectral lines in hot dense matter

Abstract An algorithm is presented for the computation of photoabsorption cross sections at arbitrary temperature and matter density. The “average atom” model is refined to give an approximaate account for the different ionization stages. The broadening of spectral lines is accounted for in a simple approximation. Calculations are presented for the beryllium and germanium plasmas in the frequency region of spectral lines.

Photoexcitation and photoionization of atoms at arbitrary temperature and matter density

Abstract Bound-bound and bound-free oscillator strengths are calculated based on a self-consistent Hartree-Fock-Slater model of the atom. The effect of variable matter density is analyzed in detail for cold helium. Data are also presented for the Al13 and Cs55 atoms at different temperatures and matter densities.

Screening effects upon spectral lines in hot matter

Abstract Calculations of transition energies and oscillator strengths are presented for the principal series of HeII and LiII in hot plasmas. The basis of the calculations is a self-consistent Hartree-Fock-Slater average-atom model. The results disagree with the predictions of theory of plasma polarization shift and with those of the Debye-Huckel screening model.

Continuum wave functions and bremsstrahlung in plasmas based on the ion-sphere and jellium models

Abstract We determine the density of states and subject the continuum wave functions to normalization and asymptotic conditions consistent with the ion-sphere and jellium models of the plasma. To illustrate the difference between the two models, we present bremsstrahlung calculations for aluminum and iron plasmas. We also compare the exact quantum-mechanical results with the predictions of the Born-Elwert approximation and with some predictions based on phase-shift calculations. Finally, we discuss briefly the effect of a non-Maxwellian electron distribution.

Measuring opacity of shock generated argon plasmas

Abstract Plasmas are generated by passage of a strong planar shock wave through gas. Initial experiments in argon have produced plasmas with 2eV temperature, 0.004–0.04 g/cm 3 density, and coupling parameter Γ ∼ 0.3–0.7. Plasmas having Γ > 1 are attainable with greater initial gas pressure. The opacity of the plasma is measured versus wavelength by recording the risetime of emitted light. Initial measurements are in visible light. Preliminary results are compared with calculations using the HOPE code.

Photorecombination rates of hydrogenic and nonhydrogenic states

The authors present analytical approximations for photoionization cross sections from hydrogenic and nonhydrogenic nl-subshells. Their analytical representations satisfy the requirement that the S[sub 2] oscillator strength sum rule must not be violated. Using the analytical approximations for the cross sections, the photorecombination rates are given as functions of temperature in terms of hypergeometric functions.

Spectrum profiles in the presence of stark, Lorentz and Doppler broadenings

Abstract The nearest neighbor approximation of the Stark broadening is used, together with the standard Lorentzian and Doppler profiles, to compute convoluted line profiles. Two universal profile functions are obtained which are analogous to the Voigt function.