|Single wavelength anisotropy kinetics
Both parallel and perpendicular polarised absorption traces are collected simultaneously. The probe beam passes through the sample at 45° relative to the pump beam and is split into parallel and perpendicular beams afterwards. Timing between parallel and perpendicular polarised probe is perfect, but he optical Kerr effect tends to produce big artefacts around time zero. Alternatively, both parallel and perpendicular polarised probe beams are passed through the sample. Timing between parallel and perpendicular polarised probe is now a problem. It has to be adjusted carefully during experiment and small corrections are usually needed during fitting. The relative overlap between pump and the two probes are somewhat problematic. But he optical Kerr effect artefacts are gone. Despite the problems mentioned above it is more accurate to measure anisotropy kinetics this way than doing it by repeating two single wavelength measurements with different polarized probes and of course faster.