4.1.14. Ebit: laboratory astrophysics model

The EBIT model is a flexible emission line model designed to benchmark the SPEX atomic database directly against laboratory spectra, particularly from Electron Beam Ion Trap (EBIT) experiments.

This model calculates collisional excitation, including resonant excitation, and the resulting line emission due to ion-electron interactions. It operates per ion, as specified by the user. The EBIT model does not include other processes such as radiative recombination, dielectronic recombination, or continuum emission.

EBIT assumes a mono-energetic electron beam, as opposed to the Maxwellian electron distribution used in the CIE model.

There are no assumptions about ion concentration. Neighboring ion populations are typically set to zero or to a minimal value to prevent numerical overflow.

To simulate spectra involving multiple charge states, multiple EBIT components must be included.

The model enables line fitting as a function of principal quantum number n. All lines within the same n shell are scaled by a shared coefficient.

For details on the excitation cross sections used, please refer to the citations below.

Warning

Resonant excitation is not fully resolved. For more reliable results, it is recommended to focus on continuum excitation.

Warning

Some emission lines may be underestimated due to difficulty in separating resonant from continuum excitation.If significant discrepancies with laboratory data are observed, consult the SPEX support team for validation.

The parameters of the model are:

t : Beam energy T in keV. Default value: 1 keV.
iz : Element number iz. Default value: 26.
jz : Spectroscopic charge jz. Default value: 25. (Default is set to Fe XXV)
norm : The emission measure n_{\mathrm e} n_{\mathrm i} V in units of 10^{64} \mathrm{m}^{-3}. Default value: 1.
cn02 : Scaling coefficient for n=2. Default value: 1
…
cn30 : Scaling coefficient for n=30. Default value: 1
cnde : Scaling coefficient for doubly excited lines. Default value: 1
fwhm : Full width half maximum of the instrumental broadening in keV. Default value: 0.001
info : If set to 1, save model vs. database comparison to ebit_info:math:iz_jz.txt.

Default value: 1

Recommended citation: Gu et al. (2019) and Mao et al. (2022)