Extension of High-Resolution Optical Absorption Spectroscopy to Divalent Neodymium: Absorption Spectra of Nd2+ Ions in a SrCl2 Host.

There is a lack of information on electronic spectra of divalent neodymium, and thus the synthesis and characterization of Nd2+ systems is now reported. Stabilization of neodymium is observed in a chloride host, which importantly has been accomplished with Nd ions introduced in a divalent state during synthesis, unlike by γ-irradiation of Nd3+ system employed previously. This method yields good-quality SrCl2 :Nd2+ single crystals. For the first time the electronic absorption spectra of Nd2+ doped in SrCl2 have been recorded with high resolution at liquid helium temperature (4.2 K). Identification of the absorption bands occurring in the spectral range of 5000-40 000 cm-1 (2000-250 nm) has been achieved and their tentative assignment proposed. This uniquely detailed Nd2+ absorption spectrum provides basis for fingerprinting method enabling identification of the presence of Nd2+ ions in future spectra as well as in existing but as-yet not fully resolved spectra.