(1986) Mebert, Joachim; Koblinger, Otto; Döttinger, Siegfried; Eisenmenger, Wolfgang
In this work we show that in the presence of a strong phonon scattering background absorption structures can only be well resolved by reducing sample thickness to the phonon mean free path. This mean free path can be determined by analyzing the pulse shape of 285 GHz phonons. By reducing sample thickness to the appropriate value of 0,3mm the 21,2 cm -1 crystalline field transition in CaF 2:Er 3+ could be evaluated with the very high resolution of 5 GHz. In experiments performed on a 1mm thick LaF 3 Er 3+ sample we observed an absoption line at 14,2 cm -1 not visible in FIR absorption measurements.
