Spectroscopic and crystal field investigation of Kramers-ions:: Nd3+:YAB -: a case study of the crystal field structure of the 4I9/2 ground state

Single crystals of yttrium aluminium borate, YAl3(BO3)(4), (referred to as YAB) doped with 20 and 40 mol% of Nd3+ were grown using a flux growth method. Inconsistencies in regard to the reported ground state splitting of the doped material are pointed out. A consistent splitting and assignment of the I-4(9/2) ground state levels of the Kramers-ion Nd3+ was obtained by a combination of both, temperature-dependent I-4(9/2) --> P-2(1/2) polarized absorption spectroscopy and room temperature F-4(3/2) --> I-4(9/2) luminescence spectroscopy. The group theoretical implications of the crystal field analysis are considered and discussed. (C) 2002 Elsevier Science (USA).