Additional Bands in the FT-Raman Spectra of Lanthanide Compounds

Abstract

Fourier transform Raman spectroscopy has superceded conventional Raman spectroscopy in many areas of research and process control, particularly when colored, photosensitive, or  uorescent materials are under investigation.1,2 The advantages of this technique,2 and the availability of reasonably priced (dual-purpose) instruments with sophisticated software control and remote Ž ber-optic and micro-sampling accessories, have created a revival in the application of Raman spectroscopy to analytical chemistry.3–5 In this report we show that nearinfrared excitation is not, however, entirely without problems. Some samples may exhibit apparently spurious bands in the Raman spectrum, which may confuse the in terpretation. For minerals, such as  uoroapatite, Ca10(PO 4)6F2, this effect has been recognized but not explained.6 In the case of the Raman spectra of a and gAl2O3, the spurious bands have been attributed to transition metal impurities such as Fe(III). The spectra of NdPO4 under three different laser excitation lines have been presented 8 to illustrate the completely different results thus obtained and the difŽ culty in deciding which features correspond to ‘true’ Raman bands.8 It was suggested 8 that time-gating could be an effective way to distinguish Raman scattering from luminescence, and indeed, we have previously demonstrated this to be possible9,10 by using ultrashort pulse excitation and time-resolved detection by a synchroscan streak camera.