Dynamical electron and phonon processes in the excited state of LGO: Cr3+ crystals

In pseudo-Stark effect studies on the R, R' lines of LGO: Cr 3+ the C 1 point symmetry of both types of Cr 3+ centers in the low-temperature ferroelectric (C 2v ) phase as well as evidence for local compensation of Cr 3+ (Ge 4+ ) extra charge in LGO lattices were established. In direct photoelectric studies it was found that Cr 3+ photoionization takes place in a two-quantum process via the intermediate 2 E excited state. With the help of fluorescent phonon detection the diffusive regime of THz acoustic phonon propagation in LGO at T = 2 K was observed; the anharmonic phonon decay times were measured for frequencies 55 cm −1 (150 ns) and 63 cm −1 (75 ns).