4f-5d absorption of gadolinium ions in sodium gadolinium tetrafluorides

The excitation spectrum for the luminescence of Gd3+ ions appearing at ∼310 nm in NaGdF4 shows that at room temperature there appears an excitation band peaking at ∼160 nm, which originates likely from the 4f-5d transitions of Gd3+ ions on irregular crystallographic sites in NaGdF4.