The electronic structure of actinyl ions

Abstract

Polarized high resolution absorption spectra at 4-2 K are reported for single crystals of CszU(Np)O2C1 a and CsU(Np)O,,(NOz)s.Five transitions of the charge-transfer type are observed in both complexes. Zeeman effect measurements give values of g~ in every case. MCD measurements in the nitrate complex permit the unambiguous assignment of a number of excited state symmetries.It is shown by evaluation of the electron-electron repulsion integrals that the excited states are best described as originating from euy),', as opposed to rru s yy', configurations. These configurations are analogous to those describing the charge-transfer states of the uranyl(VI) ion and in some cases the parentage of the neptunyl transitions can be recognized from the polarization of their vibronic structure.

Theoretical study of the electronic spectra of neutral and cationic NpO and NpO2

“…20 The absorption spectrum of NpO 2 2+ was also recorded in the form doped into Cs 2 UO 2 Cl 4 and CsUO 2 (NO 3 ) 3 crystals. [21][22][23][24][25] These latter spectra were similar to the solution ones implying that the transition energies are not much affected by the environment. The ground electronic states could be well determined on the basis of the above experiments: they are the 3 .…”

“…Selected experimental 20,23,24 and theoretical [29][30][31]33,34 results of NpO 2 2+ are compared in Table V. In the experimental spectra, five bands (two in solution 20 and five in the Cs 2 UO 2 Cl 4 crystal 23 ) have been identified as 5f-5f electronic transitions from the ground state to low-lying excited states.…”

“…[16][17][18][19][20][23][24][25][30][31][32][33][34][35] Due to the environment influencing considerably the spectral intensities in solutions and solids, our Einstein coefficients computed for the isolated molecules may not be suited for comparison. In contrast, the transition energies suffer less from the environment.…”

“…12,19,[23][24][25][26][29][30][31][32][33][34][35]38,39 We computed the excited electronic states up to ca. 35 000 cm −1 using the SO-CASPT2 method.…”

“…The ground electronic states could be well determined on the basis of the above experiments: they are the 3 . 23,24,26 The electronic spectra of the solutions were first assigned using semi-empirical ligand-field theory (NpO 2 +27 and NpO 2 2+ 28 ) and were revised later by quantum chemical calculations. 19,25,[29][30][31][32][33][34][35] Matsika et al 19,25,29 used configuration interaction methods in conjunction with relativistic effective core potentials that incorporate also spin-orbit coupling 36 (SO-MRCI).…”