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Inhomogeneous broadening of the dynamically split Kramers spectral line and up-conversion in the pair and quartet centers in CaF2:Nd3+

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 4I9/2(1) yields 4G5/2(1) crystal field (CF) transition in the CaF2:Nd3+ crystal at 4.2 K. It was found that at helium temperatures the dynamically split spectral line at the 4I9/2(1) yields 4G5/2(1) CF transition of coherently coupled Nd3+ ions in the pair M- and quartet N-centers is inhomogeneously broadened. Small variation of fluorescence lifetimes of the 4F3/2 and 4D3/2 levels due to small variation of distances between Nd3+ 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 4F3/2 manifold.