OPTICAL-PROPERTIES OF GUANIDINIUM ALUMINUM SULFATE HEXAHYDRATE (GASH)

Far-infrared reflection spectra were determined, for the first time, f or single crystals of guanidinium aluminium sulphate hexahydrate (GASH ) and its solid solution for 5 mol% chromium isomorph (GCSH). The infr ared active transversal and associated longitudinal phonon frequency a nd the dielectric permittivity functions for E parallel-to C and E per pendicular-to C have been determined using both Kramers-Kronig analysi s arid a fitting procedure based on a four-parameter model. The indice s of refraction were also measured using the immersion method with Car gille liquid and the results were compared with data obtained by numer ical analysis of reflectivity measurements. The optical transmission o f the samples were measured in the visible range and three wide energy bands were observed at about 2.6 eV, 3 eV and 4.9 eV for GASH doped w ith Cr, below the conduction energy zone.