RAMAN-SPECTRA OF IODIDE SPECIES IN INTERCALATED IBI2SR2CACU2O8+DELTA

We report Raman spectra of pristine Bi2Sr2CaCu2O8+delta and intercalated stage-1 IBi2Sr2CaCu2O8+delta single crystals. Low frequency spectra of the intercalated crystal taken at room and liquid nitrogen temperatures with the 488 nm Ar+ excitation line exhibit a strong band at 105 cm-1 and weaker bands at almost-equal-to 73 and almost-equal-to 150 cm-1. The results are confirmed by using the 647 nm Kr+ excitation line. These bands characterize the fundamental vibrations of I3- molecular anions embedded in the lattice. Drastic change of the micro-Raman scattering in the 200-700 cm-1 region is observed between pristine and iodinated crystals. A factor group analysis of stage-1 IBi2Sr2CaCu2O8+delta is presented based on possible structures and predicts that iodine vibrations can be Raman active in a non-centrosymmetric lattice.