Rare Earth Crystal Field Spectra as a Probe of Librational Motions in BaY2F8 Solid State Laser Crystals

The fine structure (FS) accompanying a few lines, originated by crystal field (CF) transitions of rare earths (RE), as Er3+ and Tm3+, in BaY2F8 single crystals, is analyzed as a function of the RE3+ concentration (0.5÷20 at%) and temperature (9-300 K), by using high resolution (as fine as 0.02 cm-1) Fourier transform spectroscopy and linear dichroism measurements. The 9 K absorption spectra show that FS includes weak, narrow, and closely spaced (0.4÷0.8 cm-1) lines, covering a few cm-1 range on both sides of the narrowest among the CF lines. The FS increases by increasing the RE3+ concentration and vanishes at rather low temperature (40 and 60 K for Er3+ and Tm3+, respectively). The polarized light spectra confirm the association of a given set of FS lines to a specific CF line. The FS is ascribed to the simultaneous excitation of an electronic CF transition and of a local librational (or hindered rotation) mode of the RE3+-F- group. The attribution is supported 1) by specific features of the host matrix and guest rare earths, which allow some mobility of F- ions, and 2) by the spacing of the FS lines, which is in excellent agreement with the calculated RE3+-F- group rotational constant.

CAPELLETTI R.;  BARALDI A.;  BUFFAGNI E.;  MAGNANI Nicola;  MAZZERA M.; 

2011-01-25

Institute of Physics Publishing (IOP)

JRC61986

http://iopscience.iop.org/1742-6596/249/1/012017,    https://publications.jrc.ec.europa.eu/repository/handle/JRC61986,   

10.1088/1742-6596/249/1/012017,