Non-vibrational features in NIR FT-Raman spectra of lanthanide sesquioxides

In this Letter, we report the FT-Raman and FT-NIR spectra of all lanthanide sesquioxides and yttrium sesquioxide. The majority of lanthanide sesquioxides and yttrium sesquioxide show additional bands in FT-Raman spectra (after the excitation with the 1064 nm line of a Nd:YAG laser) that cannot be explained by vibrational origin. Additional bands in the FT-Raman spectra of heavy lanthanide sesquioxides appear in the Stokes region of the spectrum, but there are also some very strong unexpected bands in the anti-Stokes region of some light lanthanide sesquioxides and in yttrium sesquioxide, notably around 800 and 1100 cm−1. The non-vibrational bands present in FT-Raman spectra of lanthanide sesquioxides and yttrium sesquioxide are not seen in published Raman spectra with visible excitation. A possible origin of these additional bands is in luminescence of lanthanide ions.