  The understanding of the mean free path (MFP) distribution of the energy
carriers in materials (e.g. electrons, phonons, magnons, etc.) is a key
physical insight into their transport properties. In this context, MFP
spectroscopy has become an important tool to describe the contribution of
carriers with different MFP to the total transport phenomenon. In this work, we
revise the MFP reconstruction technique and present a study on the impact of
the regularization parameter on the MFP distribution of the energy carriers. By
using the L-curve criterion, we calculate the optimal mathematical value of the
regularization parameter. The effect of the change from the optimal value in
the MFP distribution is analyzed in three case studies of heat transport by
phonons. These results demonstrate that the choice of the regularization
parameter has a large impact on the physical information obtained from the
reconstructed accumulation function, and thus cannot be chosen arbitrarily. The
approach can be applied to various transport phenomena at the nanoscale
involving carriers of different physical nature and behavior.
