  We calculate the recombination spectra of the He-like ions He~I, C~V, N~VI,
O~VII, Ne~IX, Mg~XI, Si~XIII, S~XV, Ar~XVII, Ca~XIX, and Fe~XXV. We include the
following physical processes: radiative recombination, dielectronic
recombination, three-body recombination, electron impact ionization, and
collisional excitation by electrons, protons, and $\alpha$-particles. The
calculations account for the effects of lowering of the continuum at high
densities and high density corrections to dielectronic recombination.
  Then we construct models for He-like ions for fast computation of their
spectra. Every model includes 29 bound levels up to n=5 and 6 doubly excited
levels that account for the most important satellite lines. The models are
constructed in a way that allows for proper approach to LTE under appropriate
conditions. These models can simultaneously solve for the H/He-like ionization
balance in photoionized or collisionally ionized plasmas and compute emission
spectra including the combined effects of radiative and dielectronic
recombination, collisional excitation, photoionization from excited levels,
fluorescence, and line trapping. The models can be used for any temperature
between 100 and $10^9$K and electron densities of up to $10^{18}$ \cm3. The
models can be easily used within spectral modeling codes or as stand-alone
tools for spectral analysis.
  We present comparisons between the results of the present models and previous
work. Significant differences are found between the present effective
recombination rate coefficients to the $n=2$ and those of previous estimates.
Later, we study various emission line ratio diagnostics under collisional
ionization and photoionized conditions.

Astrophysics