Inhomogeneous broadening of the dynamically split Kramers spectral line and up-conversion in the pair and quartet centers in CaF 2 :Nd<sup>3+</sup>
Abstract
The detailed site-selective and time-resolved fluorescence laser spectroscopy and kinetic measurements with high spectral and nanosecond temporal resolution were applied to analyze the M and N absorption bands at the <SUP>4</SUP>I<SUB>9/2</SUB>(1) yields <SUP>4</SUP>G<SUB>5/2</SUB>(1) crystal field (CF) transition in the CaF<SUB>2</SUB>:Nd<SUP>3+</SUP> crystal at 4.2 K. It was found that at helium temperatures the dynamically split spectral line at the <SUP>4</SUP>I<SUB>9/2</SUB>(1) yields <SUP>4</SUP>G<SUB>5/2</SUB>(1) CF transition of coherently coupled Nd<SUP>3+</SUP> ions in the pair M- and quartet N-centers is inhomogeneously broadened. Small variation of fluorescence lifetimes of the <SUP>4</SUP>F<SUB>3/2</SUB> and <SUP>4</SUP>D<SUB>3/2</SUB> levels due to small variation of distances between Nd<SUP>3+</SUP> ions in the pairs was found. Approximately 1 percent variation of the Nd-Nd distance in the pair -center was determined form lifetime variation of the <SUP>4</SUP>F<SUB>3/2</SUB> manifold.