Extending Dieke's diagram

The use of vacuum ultraviolet radiation (VUV; λ<200 nm) in lanthanide spectroscopy has been triggered by the need for new luminescent materials for VUV excitation. In spite of this `applied’ incentive, the VUV studies have resulted in a wealth of new fundamental knowledge on the luminescence of lanthanides. Here, the observation of many new intraconfigurational 4fn transitions in the VUV is reported for various lanthanide ions. Based on these observations and energy level calculations an extension of the more than 30-year old Dieke diagram from 40 000 to about 70 000 cm−1 is obtained. New emitting 4f levels in the VUV are identified as well.