Absorption of X-coloured RbCl: Sr in the F region

Abstract

Absorption spectra of X-rayed RbCl: Sr were investigated in the visible region and compared to that of pure RbCl. The half width of the F band in Sr-doped RbCl was 0·24 eV (at L.N.T.) compared to 0·19 eV in pure RbCl. The shape of the F band in the doped crystal did not fit a single Gauss Ian. Thermal annealing to about 420°K reduced the half width to 0·19 eV and caused the shape of the F band in RbCl: Sr to coincide with the Gaussian shape of the F band in the pure crystal. An absorption band at 2·85 eV was found to grow and decay proportionally with the Z ₁ band (1·78 eV.) A theoretical approach is outlined which takes into account the strong admixture of the Is and 2pz states of the F centre due to the lowering of the symmetry in the Z ₁ centre.