Vacuum-ultraviolet absorption bands of trivalent lanthanides in La<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">F</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math>

The ultraviolet absorption bands of trivalent rare earths in La${\mathrm{F}}_{3}$ are located by the use of absorption and selective excitation spectra. These absorptions are quite strong arising from the electric dipole transition, which promotes a $4f$ electron from the rare-earth $4{f}^{n}$ shell to the $5d$ or some higher-lying orbital. The onsets of the $5d$ absorptions range from about 40 000 ${\mathrm{cm}}^{\ensuremath{-}1}$ for cerium to beyond 80 000 ${\mathrm{cm}}^{\ensuremath{-}1}$ for lutetium showing a general increase from cerium to gadolinium, a sudden drop from gadolinium to terbium, and another increase. The positions of the bands are compared with estimates by several workers of the $5d$ level position for trivalent free ions. In general the La${\mathrm{F}}_{3}$ crystal field lowers and broadens the $5d$ level with respect to its freeion counterpart. For the simplest rare earth, cerium, the splitting caused by the La${\mathrm{F}}_{3}$ crystal field is calculated using a point-charge model. Agreement with experiment is poor, so a two-parameter fit to the splitting is made which indicates that the point-charge model plus the approximation for the radial integrals involved overestimate the crystal-field perturbation on the $5d$ electron by roughly a factor of 3.