Absorption and circular dichroism spectra of Bi12SiO20⟨Nd⟩ crystals

The absorption and circular dichroism spectra of Nd-doped Bi12SiO20 crystals were measured in the range 10000 to 20000 cm(-1). The spectra showed electronic transitions related to only one type of Nd-related center: Nd substituting for Bi in position with symmetry C-1. The bands due to the transitions from the first Stark component of the ground state to Stark components of excites states (I-4(9/2) --> (4)G(5/2), 4I(9/2) --> (2)G(7/2), and I-4(9/2) --> (4)G(7/2)) were analyzed in detail. The dipole strength D-0k, rotatory power R-0k, and anisotropy factor G(0k) of these transitions were calculated. The intensities of transitions to Stark components were shown to vary by more than one order of magnitude within an excited-state multiplet. The anisotropy factors of the I-4(9/2), --> (2)G(7/2) and I-4(9/2) --> (4)G(7/2) transitions, allowed in the magnetic dipole approximation, are, on the average, larger than that of the I-4(9/2) --> (4)G(5/2) transition, which points to a significant contribution of the magnetic moment (lambda(mu)lambda(2)) to the total intensity of the transition.