In this paper we present the results of spin-orbit relativistic ab initio model potential embedded cluster calculations of the 5 f 2 6d 1 excited manifold of (UCl 6 ) 3Ϫ embedded in a reliable representation of the Cs 2 NaYCl 6 elpasolite host. They are aimed at interpreting the 5 f 3 →5 f 2 6d 1 absorption bands reported by Karbowiak et al. ͓J. Chem. Phys. 108, 10181 ͑1998͒.͔ An excellent agreement is found between the calculated energies of the absorption transitions from the ground state 5 f 3 1 ⌫ 8u ( 4 I 9/2 ) and the experimental data, which supports a detailed interpretation of the electronic nature of the absorption spectrum in the energy region 14 000-23 000 cm Ϫ1 . In particular, the three unidentified electronic origins that had been experimentally detected are now assigned, and the observed bands are interpreted as having multiple electronic origins. From the structural point of view, the excited states of the 5 f 2 6d 1 manifold are classified in two sets of main configuration 5 f 2 6d(t 2g ) 1 and 5 f 2 6d(e g ) 1 with bond distances R e ͓5 f 2 6d(t 2g ) 1 ͔ϽR e ͓5 f 3 ͔ ϽR e ͓5 f 2 6d(e g ) 1 ͔. The energies of the 5 f 2 6d 1 manifold of free U 3ϩ have also been calculated; experimental data on them are not available in the literature to the best of our knowledge. These results contribute to show that wave function based ab initio methods can provide useful structural and spectroscopic information, complementary to the experimental data, in studies on actinide ion impurities doping ionic hosts, where large manifolds of 5d nϪ1 6d 1 excited states are involved.