Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.arcetri.astro.it/science/spettro/old/readme.html
Дата изменения: Fri Oct 30 18:41:05 1998
Дата индексирования: Fri Feb 28 07:24:39 2014
Кодировка:
The Arcetri Spectral Code - E.Landi and M.Landini (1998)

The Arcetri Spectral Code - E.Landi and M.Landini (1998)
The Arcetri Spectral Code (Landi and Landini 1998) allows to evaluate the spectrum of continuum and line radiation emitted by hot and optically thin plasmas in the spectral range 1-2000 Angstrom.
The Code is composed by a large database of atomic data and transition probabilities for calculating spectral line emissivities and a suite of fortran programs able to evaluate free-free, free-bound and two-photon continuum radiation.

Continuum programs

The continuum programs and data are described in more detail in Landini and Monsignori Fossi (1990). The continuum approximations come from:
Free-free continuum: Kato (1976). The Code computation includes H and He only. The mean Gaunt factor is evaluated following Karzas and Latter (1961).

Free-bound continuum: Kato (1976). Free-bound continuum is evaluated for all ions up to Z=30; recombinations to the ground levels only are considered.

Two-photon continuum: Tucker and Koren (1971). Only H-like ions (up to Z=30) are considered.

Line emissivity

Line emissivities are calculated according to the formula: 

  
             Nj(X^+m)   N(X^+m)   N(X)   N(H)   Aij 
Emissivity = -------- x ------- x ---- x ---- x --- x (Ei - Ef)   erg cm^3 s-1
              N(X^+m)     N(X)    N(H)    Ne     Ne

	       (a)        (b)     (c)    (d)    (e)     (f)
where The element abundances from Feldman 1992 have been adopted.
The ionization equilibrium ion fractions come from Arnaud & Raymond (1992) for Fe, Arnaud & Rothenflug (1985) for H, He, C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca and Ni, and Landini & Monsignori Fossi 1991 for the remaining ions up to Z=30.

Emission line database

The Arcetri Spectral Code calculates spectral line emissivities by solving the equations of statistical equilibrium for level population (a) for all the ions included in the present version. Only H-like, He-like and a few other transitions are still treated with the Coronal Model Approximation using the equations in Landini and Monsignori-Fossi 1990.
The calculation of level populations requires a huge amount of atomic data and radiative and collisional transition probabilities. For this reason the database of the Arcetri Spectral Code has been entirely updated, and the number of ions and transitions included in the computation greatly increased. The data are taken from literature. Data for the most abundant ions (C, N, O, Ne, Mg, Al, Si, S, Ar, Ca, Fe and Ni) have been taken from the CHIANTI database (Dere et al. 1997, Landi et al. 1999), while the so-called Minor Elements (F, Na, P, Cl, K, Ti, Cr, Mn, Co and Zn) come from Landi and Landini (1998).
As the atomic data and transition probabilities are taken from intermediate coupling calculations, they allow the calculation of line emissivities for each component of a multiplet separately.

References

To get the Arcetri Code files

To get he Arcetri Spectral Code related publications

Go back to the main page


Mail comments regarding interface to enricol@arcetri.astro.it
Mail comments regarding spectrum data to mlandini@arcetri.astro.it, enricol@arcetri.astro.it