Survey of the Spectra of the Divalent Rare-Earth Ions in Cubic Crystals

Abstract

The rare-earth ions may exist in the divalent state in suitable host crystals such as CaF2. All of the trivalent ions from Ce to Yb (and probably also La) are reduced in situ to the divalent state in CaF2 by gamma irradiation. The spectra of most of these ions show that the ground and first few excited states derive fromfn configurations, but the weak absorption due to these is masked at higher energies by strong broad bands of the parity-permitted f"->fn-'d transitions. The excitation energy of these spectra have been calculated in a first approximation as the energy difference between the "Hund rule," single-determinant states of the configurationsr-'d andf". This procedure satisfactorily accounts for the remarkable variations in the excitation energy in passing from one ion to the next in the series with the exception of Gd++ Ce++ and Tb++. Gd++ probably has Fa for its ground configuration, while Ce++ and Tb++ are borderlin~ cases: !he spectral str:uc~ure probably arises chiefly from the crystal-field splitting of the a orbital, since each ion m CaF2 has a Similar spectrum, and the spectra change drastically in sites of other than cubic symmetry.

Influence of Various Impurities on the Optical Properties of YbF3-Doped CaF2Crystals

“…For Yb 3+ ions the strongest absorption band peak appears around Y 4 = 979 nm and corresponds to C 2v or C 3v symmetries. The other peaks, called Y 1 , Y 2 , and Y 3 bands, are also observed by several investigators, but there are some discrepancies between their spectra [1][2][3][4]. The sharp Y 1 = 922 nm band has not been reported by [4] but has been observed by [3,9,11].…”

“…Several of RE ions (such as Eu, Sm, Ho, Tm, and Yb) can be stabilized in the divalent state in the CaF 2 . The change of valence has been attained by various methods [1][2][3][4][5]. There are a few reported results [6][7][8] about the properties of the Yb 2+ -ions, with high concentration in the as-grown crystals.…”

Optical Spectra and Electronic Structure of Actinide Ions in Compounds and in Solution

“…In their survey of the spectra of divalent lanthanides in CaF 2 , McClure and Kiss (1963) 18669 -a. The energy range shown in each case is that corresponding to the energy g-N between the ground state and the onset of intense absorption.…”

Chemiluminescence Energy Transfer Reaction for the On-Line Preparation of Peroxymonocarbonate and Eu(II)−Dipicolinate Complex

“…The absorption spectrum of Eu(II) ions in water environment revealed two bands with maxima at λ ) 248 and 318 nm ( Figure 5a), ascribed to the electronic transitions 4f f 4f 6 5d. 27 In the concentration range 10 -4 -10 -2 mol/L, for λ ) 248 nm, the Eu 2+ solutions satisfied the Lambert-Beer law. The other components of the system studied, H 2 O 2 , HCO 3 -, and HCO 4 -, did not give significant signals for λ ) 248 and 318 nm.…”