Raman spectroscopy of nacrite single crystals at 298 and 77 K

A Raman microscope in conjunction with a thermal stage has been used to determine the Raman spectra of single crystals of nacrite at 298 and 77 K. The spectra obtained are a function of the physics of the spectrometer and were orientation dependent. Bands are observed at 3710, 3646, 3630 and 3623 cm(-1). Upon obtaining the Raman spectra at liquid nitrogen temperature, the band at 3648 cm(-1) was not observed but an additional band at 3603 cm(-1) appeared. This latter band may be attributed to the hydroxyl stretching of non-hydrogen bonded interlayer hydroxyls in the nacrite. The bands attributed to both the inner and inner surface hydroxyls moved to lower frequencies upon cooling to liquid nitrogen temperatures. Low frequency bands also showed orientation dependence.