Magnetic-dipole and electric-quadrupole effects inLaCl3:Tb3+

An experimental study of the hyperfine structure of five ${\mathrm{LaCl}}_3$:${\mathrm{Tb}}^{3+}$ levels is presented, and the methods used for obtaining highly resolved optical spectra described. The results are satisfactorily interpreted by considering second-order effects in the Zeeman and electron-nuclear interaction. The magnetic-dipole and electric-quadrupole hyperfine-structure parameters of the 4$f^8$ configuration are derived. A new estimate of the quadrupole moment of the Tb nucleus is discussed.