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Дата изменения: Fri Mar 15 16:35:49 2002
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The Arcetri Spectral Code - E.Landi and M.Landini (2002)

The Arcetri Spectral Code - E.Landi and M.Landini (2002)
The Arcetri Spectral Code (Landi and Landini 2002) 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 cm3 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 Mazzotta et al. (1998); elements are included 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 (term a of the above equation) for all the ions included in the present version. The calculation of level populations requires a huge amount of atomic data and radiative and collisional transition probabilities. The data are taken from the CHIANTI database (Dere et al. 1997, Landi et al. 1999, Dere et al. 2001). CHIANTI is a database consisting of critically evaluated atomic data and transition probabilities necessary to analyze spectral observations of optically thin plasmas.
Only some transitions, not yet included in the CHIANTI database, are still treated with the Coronal Model Approximation using the equations in Landini and Monsignori-Fossi (1990).
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

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Mail comments regarding interface to landi@poppeo.nrl.navy.mil
Mail comments regarding spectrum data to mlandini@arcetri.astro.it, landi@poppeo.nrl.navy.mil