Context : Models of stellar spectra are necessary for interpreting light from individual stars , planets , integrated stellar populations , nebulae , and the interstellar medium .

Aims : We provide a comprehensive and homogeneous collection of synthetic spectra for a wide range of atmospheric parameters and chemical compositions .

Methods : We compile atomic and molecular data from the literature .
We adopt the largest and most recent set of ATLAS9 model atmospheres , and use the radiative code ASS \epsilon T .

Results : The resulting collection of spectra is made publicly available at medium and high-resolution ( R \equiv \lambda / \delta \lambda = 10 , 000 , 100,000 and 300,000 ) spectral grids , which include variations in effective temperature between 3500 K and 30,000 K , surface gravity ( 0 \leq \log g \leq 5 ) , and metallicity ( -5 \leq [ Fe/H ] \leq + 0.5 ) , spanning the wavelength interval 120-6500 nm .
A second set of denser grids with additional dimensions , [ \alpha /Fe ] and micro-turbulence , are also provided ( covering 200-2500 nm ) .
We compare models with observations for a few representative cases .

Conclusions :