We report the scintillation spectra of Ar-CF4 mixtures in the range
210-800~nm, obtained under X-ray irradiation for various pressures (1-5~bar)
and concentrations (0-100%). Special care was taken to eliminate effects
related to space charge and recombination, so that results can be extrapolated
following conventional wisdom to those expected for minimum ionizing particles
under the typical electric fields employed in gaseous instrumentation. Our
study sheds light into the microscopic pathways leading to scintillation in
this family of mixtures.Comment: Updated to match current journal submissio