  We have obtained a UVES spectrum of a slowly rotating strongly magnetic Ap
star, HD 144897, that exhibits very large overabundances of rare-earth
elements. Here we present a detailed spectral analysis of this object, also
taking into account effects of non-uniform vertical distribution
(stratification) of chemical elements. We have determined the photospheric
abundances of 40 ions. For seven elements (Mg, Si, Ca, Ti, Cr, Mn, Fe), we have
obtained a stratification model that allow us to produce a satisfactory fit to
the observed profiles of spectral lines of various strength. REEs abundances,
that for the first time in the literature have been determined from the lines
of the first and second ions, have been found typically four dex larger than
solar abundances. Our analysis of REE spectral lines provide a strong support
to the laboratory line classification and determination of the atomic
parameters. The only remarkable exception is Nd III, for which spectral
synthesis was found to be inconsistent with the observations. We have therefore
performed a revision of the Nd III classification. We have confirmed the
energies for 11 out of 24 odd energy levels classified previously, and we have
derived the energies for additional 24 levels of Nd III, thereby increasing
substantially the number of classified Nd III lines with corrected wavelengths
and atomic parameters.
