High-energy (2)G(2)(9/2) emission and 4f(2)5d -> 4f(3) multiphonon relaxation for Nd3+ in orthoborates and orthophosphates - art. no. 045115

Luminescence from the high 4f(3) energy level of trivalent neodymium (2)G(2 )(9/2) (similar to 47 400 cm(-1)) is reported. For Nd3+ in MBO3 and MPO4 (M = La, Y, Lu, Sc), either emission from this level or emission from the 4f( 2)5d level, is observed upon excitation into the 4f(2)5d configuration. A c lear correlation between the occurrence of (2)G(2)(9/2) emission and the 4f (2)5d(-2)G(2)(J) energy gap was found. For gaps larger than four or five ti mes the maximum phonon energy, radiative decay from the 4f(2)5d level domin ates (resulting in f-d emission) while for smaller gaps the 4f(2)5d to 4f(3 )[(2)G(2)(J)] nonradiative relaxation is the faster process [resulting in ( 2)G(2)(9/2) emission]. The similarity between the presently observed critic al gap for which 4f(n)-(1)5d to 4f(n) relaxation can compete with f-d emiss ion and the well-known critical gap (also four to five high-energy phonons) for nonradiative relaxation between different 4f(n) levels is rather surpr ising and is discussed.