We did some experiments with the samples that we know very well and we noticed that the kinetics are distorted.

If a kinetic profile appears to be distorted (non-exponential, wrong lifetimes) it usually means that the delay stage needs to be realigned. Please refer to the probe alignment section of the manual. A misaligned delay stage will change the overlap between the pump and the probe (Helios) or the pump and the gate (Halcyone) as you scan the delay line. This results in distorted, usually non-exponential, kinetic profiles. Another possible reason for strange kinetic profiles is sample degradation. Stirring (flowing) or translating the sample is recommended in this case.