Electronic spectra and crystal field analysis of energy levels of Ho 3+ in HoF 6 3-

The electronic absorption spectra of single crystals of Cs ₂NaHoF ₆ have been recorded in the spectral region between 4700 and 42000 cm ^-1 at temperatures down to 10 K. The structure in the ⁵I ₈ → ⁵I _J (J = 7-4), ⁵F _J (J = 5-1), ⁵S ₂, ⁵G _J (J = 4-6), ³K _J (J = 7, 8) transitions has been analyzed and assigned. The emission spectra ⁵S ₂ → ⁵I _J (J = 6-8) and ⁵G ₄ → ⁵I _J (J = 5-7), ⁵F ₅ have also been recorded at 10 K for crystals of Cs ₂NaHoF ₆ and partly also for samples of Cs ₂NaHoF ₆:Yb ³⁺. The spectra comprise magnetic dipole zero phonon lines and electric dipole allowed one-phonon vibronic sidebands. From the detailed interpretation of the emission and absorption spectra, aided by a clear understanding of the vibrational behavior of the HoF ₆ ^3- moiety and by magnetic dipole intensity calculations, a data set of 59 energy levels spanning 17 multiplet terms was derived. Crystal field calculations were then performed using a 4f ¹⁰ basis, as well as including the configuration interaction with a p-electron configuration. The latter calculation, which employed 14 parameters, gave better agreement with experiment and the mean deviation was 13.5 cm ^-1. A comparison with the energy level fittings for Cs ₂NaHoCl ₆ has been included. The crystal field parameters for the fluoro- and chloro-systems followed empirically predicted ratios. © 2011 American Chemical Society.