Extension of High-Resolution Optical Absorption Spectroscopy to Divalent Neodymium: Absorption Spectra of Nd(2+) Ions in a SrCl2 Host.

There is a lack of information on electronic spectra of divalent neodymium, and thus the synthesis and characterization of Nd(2+) 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 Nd(3+) system employed previously. This method yields good-quality SrCl2 :Nd(2+) single crystals. For the first time the electronic absorption spectra of Nd(2+) 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 Nd(2+) absorption spectrum provides basis for fingerprinting method enabling identification of the presence of Nd(2+) ions in future spectra as well as in existing but as-yet not fully resolved spectra.