摘要:

Recent work on the evaluation of the atomic internal partition function at densities less than about 10−2gm cm−3is discussed, in which an attempt is made to identify the physical mechanism responsible for determining the level populations of atoms and ions in dense LTE plasmas. Level populations predicted by a phenomenological theory based on this identification are compared with these obtained by the activity expansion method.

ISSN:0094-243X    

DOI:10.1063/1.37180

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A theoretical formalism and computer code to calculate spectra of multi‐electron emitters in plasmas are described. A quantum‐mechanical relaxation theory of line broadening due to electrons is used; and broadening due to plasma ions is treated in the static ion approximation. Calculated lithium‐like and beryllium‐like krypton spectra are compared to experimental spectra obtained from laser‐driven pellet implosion experiments at the Laboratory for Laser Energetics, University of Rochester. Calculated spectra of lithium‐like fluorine are presented.

ISSN:0094-243X    

DOI:10.1063/1.37179

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

An intense laser pulse with a duration of 100 femtoseconds can be focused onto a solid target to produce a solid state density plasma. Electrons in the solid are heated within an optical skin depth with little expansion of the heated region over the duration of the laser pulse. A model and experimental work is described.

ISSN:0094-243X    

DOI:10.1063/1.37181

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

We formulate a method to add dielectronic recombination to the average‐atom mode without conflict with the principle of detailed balance. The essential ingredient in this extended average atom model is a treatment of strong correlations of electron populations induced by the dielectronic attachment process.

ISSN:0094-243X    

DOI:10.1063/1.37182

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

To illustrate the tremendous range in physical conditions encountered in analyses of radiation from various astrophysical sources, we discuss representative physical conditions in several zones of a typical star. Even though these zones do not cover the full range of physical conditions encountered in the most exotic astronomical objects, they nevertheless give a good idea of the kinds of data required in astrophysical work. Moreover they provide a sequence of states progressively farther from equilibrium.We discuss the physical mechanisms important in determining the internal state (i.e., excitation and ionization degrees) of the material in each of the regimes chosen, and comment on whether one should expect equilibrium or non‐equilibrium distribution functions. In parallel, we delineate the major issues affecting the transport of radiation through typical astrophysical media; material properties, equilibrium versus non‐equilibrium, velocity fields, and dynamics. We attempt to emphasize the close interplay between the nature of the radiation field and the state of the material. We also try to mention where progress is being slowed by lack of data for atomic processes, and indicate what kinds of data are still needed.

ISSN:0094-243X    

DOI:10.1063/1.37183

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The methods by which we model high temperature plasmas will be described. The code XRASER is run on the Cray computers to simulate the kinetics, hydrodynamics, and radiation transfer in the high temperature plasma. Certain input is required by XRASER in the form of an atomic data file. The atomic data files are created using a variety of production atomic physics codes such as YODA. YODA will generate detailed energy levels, oscillator strengths, photoionization cross sections, collisional excitation and ionization cross section, and auger rates using relativistic multi‐configuration wavefunctions. This information is stored in an atomic data base. The code ADAM reads the atomic data from the data base and fills in the requested number of Rydberg energy levels based on a scaled hydrogenic approximation. ADAM adds the oscillator strengths, photoionization cross sections, and collisional excitation and ionization cross sections to connect the Rydberg levels with each other and also to connect the Rydberg levels with the detailed levels provided by YODA. The output of ADAM is a format which XRASER understands. Using the atomic data file and a generator which specifies the plasma, XRASER is run to determine the time dependent properties of the plasma.

ISSN:0094-243X    

DOI:10.1063/1.37184

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

With the primary aim of calculating stellar envelope opacities, a joint international collaboration is under way for the calculation of basic atomic data for radiative processes: oscillator strengths, photoionization cross sections, energy levels, radiative damping constants (including line broadening). Atomic calculations have been completed for the first ten isoelectronic sequences, H‐like to Ne‐like, going up to iron, and work is in progress on the third and fourth row atoms and isosequences. The close‐coupling approximation is employed throughout using a new version of the R‐matrix method. Particular emphasis is placed on the detailed resolution of the autoionization structures in the bound‐free continuum.

ISSN:0094-243X    

DOI:10.1063/1.37185

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

A formal expansion of the Collisional Radiative Model in powers of a small parameter is presented. The terms of the expansion are products of matrices. Inverse matrices are interpreted as effects of cascades. It will be shown that this allows for the separation of the different contributions to the populations, thus providing a natural classification scheme for processes involving atoms in plasmas. Sum rules can be formulated, allowing the population of the levels, in some simple cases, to be related in a transparent way to the quantum numbers.

ISSN:0094-243X    

DOI:10.1063/1.37189

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

The computer codes currently available to calculate the energy levels and radiative transition probabilities of highly ionized atoms taking some account of relativistic effects are compared and discussed. Some attempt is made to assess the relative quality of the various predictions.

ISSN:0094-243X    

DOI:10.1063/1.37190

出版商:AIP    

年代:1988

数据来源: AIP

摘要:

General theoretical methods for the calculation of direct and indirect processes in the electron‐impact ionization of heavy atomic ions are reviewed. Cross section results for Xe8+and U89+are presented.

ISSN:0094-243X    

DOI:10.1063/1.37191

出版商:AIP    

年代:1988

数据来源: AIP