Wydział Chemii

Mirosław Karbowiak

Janusz Drożdżyński

Norman M. Edelstein

Stéphani Schmitt Hubert

2004

Journal of Physical Chemistry B

108

160-170

10.1021/jp036209r

Naukowa

Angielski

Artykuł

Laser selective excitation and emission spectra as well as σ- and π-polarized absorption spectra have been recorded for U³⁺ ions diluted in a CsCdBr₃ host crystal. Three distinct U³⁺ sites were observed. For the principal site, which was attributed to a symmetric dimer center, 45 crystal-field energy levels in the 0−13250 cm^-1 energy range were assigned. These experimentally determined levels were fitted to thirteen parameters of a semiempirical Hamiltonian representing the combined atomic, one-electron crystal field as well as two-particle correlation crystal-field (CCF) operators, with an rms deviation of 41 cm^-1. Above 14000 cm^-1 strong electric-dipole allowed 5f³−5f²6d ¹ transitions were observed. The lifetime of the ⁴G_7/2 fluorescing level has been measured for each of the three U³⁺ sites at liquid-helium temperatures and are 2.5, 4.3, and 7.6 μs. The emission is strongly influenced by temperature due to strong phonon coupling of the 5f³ states with the nearby 5f ²6d¹ states. Visible upconversion fluorescence observed when pumping the ⁴I_9/2 − (⁴F_7/2 + ⁴I_15/2) absorption transitions of the principal site A is attributed to excited-state absorption (ESA).

Crystal structure, Crystals, Energy levels, Group theory, Ions

https://doi.org/10.1021/jp036209r

https://www.acs.org/content/acs/en.html