Absorption Spectra of the Octahedral Complex AmBr63- in the Cs2NaLuBr6 Crystal

Absorption spectra of the Cs₂NaLuBr₆:Am³⁺ (5 mol % of ²⁴³Am) were studied in the 450-2500 nm range at temperatures from 300 to 15 K. The spectra exhibited transitions from the ground level ⁷F₀ of the Am3+ (f⁶) ion to the levels belonging to the ground term (⁷F₂, ⁷F₄, and ⁷F₆) and to the levels of the three excited states: ⁵L₆, ⁵G₂, and ⁵D₂. The vibronic pattern analysis for these transitions enabled localization of 17 electronic sublevels of the americium ion in the octahedral complex AmBr₆^3-. One sublevel of the electronic level with odd J value (⁷F₅) was localized for which the transition from the ground ⁷F0 level is forbidden in accordance with the Judd-Ofelt theory. The crystal-field paramaters of the complex studied were calculated.