Emission and excitation spectra from divalent Ge ions in KCl single crystals

Abstract The emission from KCl:Ge 2+ excited in the A -absorption band was studied as a function of temperature. The A -band excitation produces complex emission from KCl:Ge 2+ , compared with ones from Tl + -like ions with the s 2 electronic configuration. The A -band emissions from KCl:Ge 0 and KCl:Ge 4+ were also measured at low temperature. The analysis of these spectra indicates that the two low-energy emission bands of KCl:Ge 2+ which peaked at 515 and 675 nm, respectively, are to be attributed to divalent Ge ions. The definitive assignment of the two bands is presented in terms of the adiabatic potential energy surface (APES).