The optical spectra of copper ions in alkali-lime-silica glasses

It has been shown that the position of the cupric band is affected very little either by changing the silica: soda ratio or by changing the time content while keeping the silica:soda ratio constant in the molar composition range 14.7-22Na 2 O, 12-20CaO, 66-73.3SiO 2 however, it shifts to a shorter wavelength as soda is replaced by lithia and to a longer wavelength as soda is replaced by potash